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FOR OFFICIAL USE ONLY

Developing a Roadmap for

Improving Water Quality of Lake

Toba Tourist Destination, Indonesia

Final Report – Final Draft

Prepared by Deltares for the World Bank upon the request of Indonesia’s Coordinating

Ministry of Maritime Affairs and the Ministry of Public Works and Housing This work received financial support from Australian Government through the Indonesia Infrastructure Support Trust Fund (INIS TF)

This document has a restricted distribution and may be used by recipients only in the performance of their official duties. Its contents may not otherwise be disclosed without World Bank authorization.

21 February 2018, Final Draft, FOR OFFICIAL USE ONLY

Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia -Final Report

i

Key Messages

Tourism is a promising growth sector in Indonesia that can provide inclusive and sustainable

opportunities for economic development. The archipelago is home to one of the most biodiverse

habitats in the world having a rich array of tourism endowments that form the underlying

attraction for visitors. Indonesia has expanded the promotion of its natural resources by

increasing the size of protected areas and attracting more online interest in nature. Despite this,

Indonesia’s tourism industry is not operating at a level consistent with the quality and diversity

of its natural and cultural endowments, with environmental sustainability a key risk factor for

the sector (WEF, 2017).

Four key constraints contribute to Indonesia not fulfilling its tourism potential. These include: (i)

continued poor access to, and quality of, infrastructure and services for citizens, visitors and

businesses; (ii) limited tourism workforce skills and private-sector tourism services and facilities

outside of Bali; (iii) weak enabling environment for private investment and business entry; and

(iv) poor inter-ministry/agency, central-local and public-private coordination and weak

implementation capabilities for tourism development in general, and for monitoring and

preservation of natural and cultural assets in particular.

In response, the Government has launched the Indonesia Tourism Development Priority

Program. For the implementation of the program, the Government has decided to sequence

the development of tourism destinations, starting with three priority destinations: Lombok in

West Nusa Tenggara province; Borobudur-Yogyakarta-Prambanan in Central Java province

and the Special Region of Yogyakarta; and Lake Toba in North Sumatra province. If developed

effectively, these three distinctively different and unique destinations are expected to increase

their combined annual foreign and domestic visitor expenditures from an estimated US$1.2

billion in 2015 to US$1.5 billion in 2021 and US$2.0 billion in 2026 (Horwath, 2017).

The objective of this report is to prepare a Roadmap for Improving Water Quality of Lake Toba

as a Tourism Destination. It provides an understanding of the key drivers of water quality issues

and investment scenarios to reduce nutrient loads into the lake. These are intended to inform

the preparation of an Integrated Tourism Master Plan to provide a stronger framework for

effective and sustainable tourism development.

Lake Toba is the largest volcano tectonic lake in the world and one of Indonesia’s priority

tourism destinations. However, Lake Toba is largely a destination for local tourism with

declining appeal. With improvements in accessibility, recreational activities and environmental

sustainability, Lake Toba can become an attractive destination for a much wider variety of

domestic and international visitors.

The water quality of Lake Toba is under threat from eutrophication. Science informed policy

measures have established the desired lake quality as oligotrophic. However, the current state

is mesotrophic for phosphorous and chlorophyll. This leads to local effects such as algal blooms

that harm the tourism sector. This eutrophication is mainly driven by residues from aquaculture

(68% of total phosphorous load and 76% of total nitrogen). Other contributors include livestock

(19% of phosphorous and 5% of nitrogen) and domestic wastewater (11% of phosphorous and

15% of nitrogen).

Aquaculture production is far in excess of the legally established carrying capacity. Whole lake

estimates based on numerous scientific studies have established the carrying capacity for

aquaculture at 10,000 tons. While aquaculture is a relatively recent economic activity in Lake

ii Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Toba, the rapid expansion of large commercial ventures and local producers since the 1990s

has resulted in thousands of floating fish cages in the lake, with 2015 production estimated

around 85,000 tons. Not all aquafarms are operating within the legal framework with poor inter-

ministry/agency, central-local and public-private coordination and weak implementation

capabilities for monitoring and preservation undermining the natural and cultural assets of Lake

Toba.

A compartmentalized approach to modelling the water quality of Lake Toba provides new

insights into the functioning and drivers of water quality. Four theoretical compartments have

been defined based on topography and bathymetry. This includes one northern and three

southern compartments. These compartments provide a differentiated assessment of the key

drivers associated with water quality in Lake Toba. These can be further refined based on a

continuous process of improvement informed through better data. Results show that targeted

strategies are required to achieve local impacts and for monitoring and management of water

quality interventions.

While an integrated approach to water management is required for Lake Toba, water quality

cannot be improved without reducing the current production of aquaculture. Four scenarios

have been modelled to compare the impact of low, intermediate and high levels of investment

intended to impact the nutrient loads into Lake Toba. Only by reducing aquaculture in the lake

to a total production level of no more than 10,000 tons per year can water quality in the lake be

expected to recover to an oligotrophic state.

Aquaculture can be reduced mainly by limiting licenses and by improving law enforcement. This

should be supported by training in alternative livelihoods such as organic farming and fisheries.

The estimated total costs over five years would be IDR 9.7 billion (US$ 719,000) under an

intermediate scenario, gradually bringing down fish production, and IDR 34.2 billion (US$ 2.5

million) under a high investment scenario to reach the target of 10,000 tons of fish per year in

2022. Crucial to the success of these measures is the political commitment to change the

licensing structure and implement more stringent law enforcement.

Such a strategy will have different impacts for different districts in Lake Toba, with the districts

benefiting from increased tourism growth and the districts being affected by reduced

aquaculture not always being the same. Similarly, tourism job gains and aquaculture job losses

might be distributed unevenly. The government’s agenda thus requires recognition and

quantification of trade-offs, which can be eased by measures, such as revenue-sharing

arrangements between districts, intensified training opportunities and a phased, rather than

abrupt change of policy.

Nutrient loads can be further reduced through interventions in processing livestock manure and

domestic wastewater management to further strengthen the impact of measures implemented

in the aquaculture sector. The conversion of livestock manure into biogas would require IDR

12.9 billion (US$ 957,000) for five years under an intermediate scenario, aiming for 20%

conversion by 2022 or IDR 18.8 billion (US$ 1.4 million) under a high investment scenario

resulting in 30% conversion.

Implementation of the national sanitation strategies could accelerate the construction of

individual and community-based on-site septic tank systems with positive benefits for longer

term water quality. An intermediate scenario would provide 85% of the population in the

catchment area of Lake Toba with septic tank systems by 2022. This would require an extra



iii

investment of IDR 694.6 billion (US$ 51.5 million). A high investment scenario would provide

access to centralized sewer-based systems for 31% of the population. Its costs would be IDR

3,866.9 billion (US$ 286.5 million).

The targeted oligotrophic status can only be achieved through an integrated management plan

under a high investment scenario. Total net investment costs for this scenario would be IDR

3,919.8 billion (US$ 290.5 million) for five years. While the biggest impacts would be realised

through improved regulation of aquaculture, the majority of these investments would be in water

supply and sanitation. The impacts of these interventions on nutrient concentrations would be

different for each of the compartments. In the southern part of Lake Toba, the oligotropic state

would be achieved in 2022, except for the smallest and most intensively used compartment

west of Samosir. This part of the lake would stay eutrophic even under high investment

scenarios, unless additional efforts are deployed to reduce nutrient loads from domestic

wastewater and livestock. In the northern part of the lake, concentrations would eventually

reach low mesotrophic levels, approaching the oligotrophic limit of 10 µg per litre. The

intermediate scenario, at a cost of IDR 717.2 million (US$ 53.0 million) for the first five years,

would achieve these results only in 2042. In 2022 the intermediate scenario would not result in

long term oligotrophic state in any of the compartments.

A cost-efficient approach would be a combination of options; selecting high investment

interventions for aquaculture and livestock, combined with intermediate interventions for

wastewater. This combination would cost IDR 747.5 billion (US$ 55.4 million), reducing the

public investment costs by IDR 3.17 billion (US$235 million) as compared to the high

investment scenario, while impacts on water quality would still be high because of the

substantial reduction in nutrients due to aquaculture.

A comprehensive water quality monitoring program is required to assess long term trends in

Lake Toba and to inform an adaptive management approach. This should be based on

collaboration aligned with institutional responsibilities and free open source data sharing. When

combining the existing activities of the main water quality monitoring institutions, a

comprehensive approach can be achieved, including signal, exploratory and statistical

functions. This should include regular sampling and analysing a range of variables for

background monitoring and depth profiles, at no less than forty stations distributed across the

lake. It is estimated to cost a minimum of IDR 20.4 billion (US$ 1.5 million) annually, or IDR

102 billion (US$ 7.6 million) over 5 years. A more aspirational program building on latest

technologies and involving stakeholders is estimated to cost around IDR 92.3 billion (US$ 6.8

million) per year, amounting to IDR 462 billion (US$ 32.4 million) over 5 years.

Sustained political commitment across all levels of government and sectoral coordination

among different stakeholders will be essential to realising the government’s agenda for

improving the water quality and tourism value of Lake Toba. Such an approach needs to be

supported by a water quality and waste load monitoring program. This could continuously

assess the impact of interventions under the Integrated Management Plan and to enable

adaptive actions during implementation. Together, the proposed interventions and monitoring

plan would guide the integrated management of water quality in Lake Toba and support the

contribution of Lake Toba to the economic and social development of Indonesia and serve as

an example for the management of other lake basins.

iv Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Contents

Executive Summary

Acronyms

Glossary

1 Introduction 1 1.1 Background 1

1.1.1 Water quality concerns at Lake Toba 1 1.1.2 Rationale for roadmap 2

1.2 Objective and approach 3 1.2.1 Stakeholder consultations 4 1.2.2 Reference Group 4

1.3 Overview 5

2 Lake Toba as a Tourism Destination 7 2.1 Lake Toba and its surroundings 7

2.1.1 Topography 7 2.1.2 Climate 8 2.1.3 Land-use practises and spatial development 8 2.1.4 Economy 10 2.1.5 Batak culture 14

2.2 Catchment hydrology and functioning of Lake Toba 15 2.2.1 Catchment dimensions and water level 15 2.2.2 Catchment erosion 16 2.2.3 Biogeochemical processes in Lake Toba 17 2.2.4 Residence time and recovery time of Lake Toba 17 2.2.5 Stratification 17 2.2.6 Horizontal lake circulation and zonation 19

2.3 Key factors of Lake Toba water quality problems 22

3 Legal and Institutional Environment 27 3.1 Approach 27 3.2 Standards for monitoring 27

3.2.1 Oligotrophic status and class 1 standard 29 3.2.2 Aquaculture Stewardship Council (ASC) Standards 30

3.3 Institutional arrangements for monitoring 31 3.3.1 Provincial Environment Department – North Sumatra (DLH-SU) 31 3.3.2 Indonesian Institute of Sciences (LIPI) 33 3.3.3 River Basin Operator (PJT1) 34 3.3.4 PT Aquafarm Nusantara (PTAN) 35

3.4 Legal arrangements for water quality management 36 3.4.1 Provincial setting 38 3.4.2 National setting 38 3.4.3 International setting 40 3.4.4 Licensing and permits 41

3.5 Legislation vs implementation 43



v

4 Stakeholders and Governance 45 4.1 Approach 45 4.2 Stakeholder mapping 45

4.2.1 Mapping 45 4.2.2 Key stakeholders 48

4.3 Stakeholder assessment 52 4.4 Governance for monitoring and management of Lake Toba 53

4.4.1 Approach 53 4.4.2 Overall SWOT 53 4.4.3 Synthesis 56

5 Drivers and Pressures: nutrient inputs 57 5.1 Approach: the Sumatra Spatial Model 57

5.1.1 Calibration of population growth 57 5.1.2 Load calculations 57

5.2 Assessment of point and non-point sources 59 5.3 Total and relative nutrient loads 64 5.4 Nutrient inputs 70

6 State and Impact: Lake Assessment 71 6.1 Approach 71 6.2 Available data 71

6.2.1 Main data sets 71 6.2.2 Quality of data 72

6.3 Physical and chemical parameters 73 6.3.1 Temperature 74 6.3.2 Dissolved Oxygen (DO) 76 6.3.3 Transparency (Secchi depth) 78

6.4 Nutrients 79 6.4.1 Phosphorous 79 6.4.2 Nitrogen 80

6.5 Organic content 81 6.6 Thermocline depth 82 6.7 Remote sensing insights into water quality dynamics 83 6.8 Hydrothermal stability and mixing events 85 6.9 Trends 89

6.9.1 Present data vs historical data 89 6.9.2 The 2016 anomaly 90

6.10 Lake status 91

7 Future Pressures and Future State 95 7.1 Approach 95 7.2 Input data 95

7.2.1 Population and economic growth drivers 95 7.2.2 Spatial plan 97

7.3 Projections in the Sumatra Spatial Model 99 7.3.1 Population projection 100 7.3.2 Land use change projection 101 7.3.3 Tourism 103

7.4 Nutrient concentration trajectories 103

vi Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


8 Response: water quality management 107 8.1 Approach 107 8.2 Aquaculture 111

8.2.1 Investment scenario 111 8.2.2 Impact on nutrients 116

8.3 Managing livestock manure 120 8.3.1 Investment scenarios 120 8.3.2 Impacts on nutrients 122

8.4 Wastewater (domestic and tourism) management 125 8.4.1 Approach and background 125 8.4.2 Investment scenarios 126 8.4.3 Impact on nutrients 130

8.5 Other interventions 134 8.5.1 Pollution in agriculture 134 8.5.2 Solid waste management 134 8.5.3 Erosion reduction 136

8.6 Cumulative impact of scenarios 138 8.6.1 Four scenarios 138 8.6.2 Alternative scenario 144

9 Response: water quality monitoring 149 9.1 Three pillars 149

9.1.1 System knowledge 150 9.1.2 Information needs 151 9.1.3 Technical capabilities 152 9.1.4 Incorproating remote sensing capabilities 152 9.1.5 Requirements 153 9.1.6 Data collection: Common sources of error 154

9.2 Monitoring working group 155 9.3 Monitoring parameters 158 9.4 Investment scenario 161

10 Summary results, conclusions and recommendations 165 10.1 Drivers of lake eutrophication 166 10.2 Status and functioning of Lake Toba 166

10.2.1 Historical and current lake status 167 10.2.2 Lake functioning 167

10.3 Water quality monitoring 168 10.3.1 Data assessment 168 10.3.2 Towards a water quality monitoring plan for Lake Toba 170

10.4 Water quality management 171 10.4.1 Potential of interventions 171 10.4.2 Reducing nutrient loads from aquaculture 174 10.4.3 Managing livestock manure 174 10.4.4 Wastewater management 175 10.4.5 Total investment costs for mitigating measures 176 10.4.6 Mitigation options and effects on eutrophication 178

10.5 Investments for impact 181

11 References A-1



vii

Appendices

A Stakeholder consultation process A-6 A.1 Reference Group A-6 A.2 Meetings A-7

A.2.1 Stakeholder meetings A-7 A.2.2 Individual meetings A-8

B Detailed description of Lake Toba B-1 B.1 Bathymetry B-1 B.2 Hydrological and administrative boundaries B-2 B.3 Soil B-2 B.4 Climate B-3 B.5 Water level B-5

C Background on functioning of lakes C-1 C.1 Theory of residence time C-1 C.2 Theory of biochemical processes C-1 C.3 Trophic level classification C-3

D Background on DPSIR D-1

E Institutional assessment E-1

F Overview of relevant legislation F-1 F.1 List of laws in English F-1 F.2 List of laws in Bahasa Indonesia F-2

G Water quality data PJT1 G-1

H Methodology of stakeholder assessment H-1 H.1 Theoretical framework H-1

H.1.1 Stakeholder roles and functions H-1 H.1.2 Social network analysis H-3

H.2 Methods and tools H-4 H.2.1 NetMap H-4

H.3 Stakeholder perceptions H-7 H.3.1 Observations from NetMap discussions H-7 H.3.2 Summary of stakeholder comments H-8

I Comprehensive list of stakeholders involved in Lake Toba water quality I-1

J Detailed methodology lake assessment J-1 J.1 Sumatra Spatial Model J-1

J.1.1 Introduction J-1 J.1.2 Land use changes J-4

J.2 Modules and variables J-5 J.2.1 Regional or Socio-economic sub-model J-6 J.2.2 Spatial allocation sub-model J-7

viii Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


J.2.3 Postprocessor for space, water and agricultural indicators J-8 J.3 Spatial results by compartment and year J-9 J.4 Calculation of nutrient concentration trajectories J-13 J.5 Comparison to LIPI data J-14

K Available data and their quality K-1 K.1 Data collected from stakeholders K-1 K.2 Completeness of the data sets K-6 K.3 Spatial and temporal distribution of data K-9

L Additional recommendations livestock L-10 L.1 Steps in managing livestock manure L-10 L.2 Promotion of biogas production L-10 L.3 Sustainable manure management L-11

M Background information wastewater interventions M-13 M.1 Background and approach M-13 M.2 Investment scenarios M-17 M.3 Parapat M-21 M.4 Institutional recommendations on wastewater management M-22

M.4.1 General considerations M-23 M.4.2 Policy actions M-23 M.4.3 Technical assistance M-26 M.4.4 Other recommendations M-27

N Other sectors N-1 N.1 Solid waste N-1

N.1.1 Approach and background N-1 N.1.2 Investment scenarios N-5 N.1.3 Conclusions and recommendations N-10

N.2 Erosion reduction N-10 N.2.1 Background N-10 N.2.2 Investment scenarios N-11



ix

Foreword [Foreword will be added to edited version]

x Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Acknowledgements This Development of a Roadmap for Improving the Water Quality of Lake Toba as a Tourist Destination is one of a series of products aimed at supporting the preparation of the Government of Indonesia Tourism Development Project. The World Bank team was led by Marcus Wishart (Senior Water Resources Management Specialist), Bertine Kamphuis (Senior Private Sector Specialist), and Amy Chua Fang Lim (Environmental Specialist), included Aleix Serrat-Capdevila (Senior Water Resources Management Specialist), Ivan Lalovic (Remote Sensing and Water Quality Specialist), Fernando Wilhelm (Remote Sensing and Water Quality Specialist), and benefitted from inputs from George Soraya (Lead Municipal Engineer), Evi Hermirasari (Senior Urban Development Specialist), and Muhammad Halik Rizki (Urban Planning Analyst). The analysis and model development were undertaken by Deltares and partners, led by Eline Boelee and included JanJaap Brinkman, Gertjan Geerling, Tineke Troost, Henni Hendarti, Bastien van Veen, Muhammad Fitranatanegara, Christophe Thiange, Rob Uittenbogaard, Bouke Ottow, Simon Groot, Annemiek Mertens (all Deltares), Hanny Chrysolite, Satrio Wicaksono, Arief Wijaya (all WRI Indonesia), Koen Broersma, J Sinarko Wibowo, Arina Priyanka Vedaswari, Hari Meidiyanto, Suhendi, Marco Piët (all Royal Haskoning DHV), as well as Poul Grashoff, Douglas Vermillion, and Robert Belk. The program was implemented under the guidance of Rodrigo A. Chaves (Country Director) and Ganesh Rasagam (Practice Manager) of the World Bank. The roadmap has been prepared upon the request of Indonesia’s Coordinating Ministry of Maritime Affairs and the Ministry of Public Works and Housing. The Coordinating Ministry of Maritime Affairs was led by Ridwan Djamaluddin (Deputy Minister for Infrastructure) and included Rahman Hidayat (Director for Infrastructure of Shipping, Fishery and Tourism) and Velly Asvaliantina (Deputy Director for Marine Tourism Infrastructure). Other Indonesian government agencies participating in the study included: 1. Fauzan Ali and Lukman (Centre of Limnology, Indonesian Institute of Sciences) 2. Rudi Nugroho, Titin Handayani, Nawa Suwedi and Agung Riyadi (Centre of Environmental

Technology, Agency for the Assessment and Application of Technology) 3. Budi Kurniawan (Directorate for Water Pollution Control, Ministry of Environment and

Forestry) 4. Hermono Sigit (Directorate for Watershed and Aquatic Management, Ministry of

Environment and Forestry) 5. Hidayati, Siti Bayu and Fauzi Tarigan (North Sumatra Provincial Environmental Agency) 6. Baru Panjaitan, Novita R and Serepita Sinurat (Basin Management Centre Sumatra II) 7. Arie Prasetyo (Head of Lake Toba Tourism Area Management Authority Board) 8. Raymond Tirtoadi (Centre for Strategic Areas, Ministry of Public Works and Housing) 9. Astria Nugrahany (Perum Jasa Tirta I)

This publication has been funded by the Australian Government through the Department of Foreign Affairs and Trade. The views expressed in this publication are the author’s alone and are not necessarily the views of the Australian Government.



xi

Acronyms

List of abbreviations, acronyms and Indonesian terms

Abbreviation/

Indonesian term

Meaning/translation

Alusi Tao Toba A local foundation in North Sumatra working mainly in the education

sector

ASC Aquaculture Stewardship Council: Dewan Pengelolaan Budidaya

Perikanan

Asosiasi Nelayan Asosiasi Nelayan/Budidaya: Fishermen Association

ATAB Air Tanah dan Air Baku – Kementerian Pekerjaan Umum dan

Perumahan Rakyat: Ground Water and Raw Water Division under

the Ministry of Public Works and Housing

ATR Kementerian Agraria dan Tata Ruang: The Ministry of Agrarian

and Spatial Planning

Badan Pengelola

GEOPARK

GEOPARK Management Agency

Balai PSDA Balai Pengelolaan Sumber Daya Air: River Basin Organisation (at

provincial level)

BAPPEDA PROV Badan Perencana Pembangunaan Daerah Provinsi: Provincial

Planning Agency

BAPPEDA KAB Badan Perencana Pembangunan Daerah Kabupaten: District

Planning Agency

BAPPENAS Badan Perencanaan Pembangunan Nasional: National

Development Planning Agency

Batak A collective term to identify a number of ethnic groups

predominantly found in North Sumatra

BBWS Balai Besar Wilayah Sungai: River Basin Organisation (at national

level)

BIG Badan Informasi Geospasial: Geospatial Information Agency

BKPEDT Badan Koordinasi Pelestarian Ecosistem Danau Toba:

Coordinating Agency for Lake Toba Ecosystem

Conservation/Environmental Sustainability Authority Lake Toba

BKPM Badan Koordinasi Penanaman Modal: Investment Coordinating

Board

BLH(-SU) Badan Lingkungan Hidup (-Sumatra Utara): Provincial

Environment Agency (- North Sumatra) from January 2017: DLH

BLU Badan Layanan Umum: Public service organization

BMKG Badan Meteorologi, Klimatologi dan Geofisika: Indonesian Agency

for Meteorological, Climatological and Geophysics

BNPB Badan Nasional Penanggulangan Bencana: The Indonesian

National Board for Disaster Management

BOD Biochemical oxygen demand

BOPDT/

BOPKPDT

Badan Otorita Pariwisata Danau Toba/ Badan Otorita Pengelola

Kawasan Pariwisata Danau Toba: Lake Toba Tourism Area

Management Authority, established through Presidential

Regulation 49/2016

xii Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Abbreviation/

Indonesian term

Meaning/translation

BPBD Badan Penanggulangan Bencana Daerah: Local Agency for

Disaster Management

BPDAS Badan Pengelola Daerah Aliran Sunga: Watershed Management

Agency (under KLHK)

BPIW Badan Pengembangan Infrastruktur Wilayah: Regional

Infrastructure Development Agency (Ministry of Public Works and

Housing

BPN-ATR Badan Pertanahan Nasional AgrariaTata Ruang: National Land

Agency, Agrarian and Spatial Planning Ministry

BPPT Badan Pengkajian dan Penerapan Teknologi: Agency for the

Assessment and Application of Technology

BPS Biro Pusat Statistik: Statistics Indonesia

BPS Buku Putih Sanitasi: Sanitation strategy for city or district

BTA 155 Bilateral Technical Assistance 155 (Cisadane-Cimanuk Integrated

Water Resources Development project), embryo of Pola and

Rencana (1985 –1991)

BTPAL Balai Teknologi Pengolahan Air dan Limbah: Organisation for

Technology of Wastewater Treatment (BPPT)

Bupati Head of district

BWRMP Basin Water Resources Management Plan (2001-2004):

Perencanaan Pengelolaan Sumber Daya Air Wilayah Sungai

BWRP Basin Water Resources Planning (1996-2001), later changed to

BWRMP: Perencanaan Sumber Daya Air Wilayah Sungai

BWS-S2

BWS-Sumatera II

Balai Wilayah Sungai Sumatera II: River Basin Organisation -

Sumatra II

CAPEX Capital investment costs

COD Chemical oxygen demand

CSO Civil society organization: Lembaga Swadaya Masyarakat

Daerma A fishermen’s association

Dewan SDA Provinsi Dewan Sumber Daya Air Provinsi: Provincial Water Resources

Council

DGWR Direktorat Jenderal Sumber Daya Air, Kemen (PUPR): Directorate

General for Water Resources under Ministry of Public Works and

Housing

Dinas Cipta Karya

Prov.

Dinas Cipta Karya: Provincial Human Settlements Agency

Dinas Cipta Karya

Kab.

Dinas Cipta Karya Kabupaten: District Human Settlements Agency

Dinas ESDM Dinas Energi dan Sumber Daya Mineral Daerah: Energy and

Mineral Resources Agency

Dinas BINA MARGA

PROV

Provincial Highway Engineering Services

Dinas Kehutanan

Prov.

Dinas Kehutanan: Provincial Forestry Agency



xiii

Abbreviation/

Indonesian term

Meaning/translation

Dinas Kehutanan

KAB

Dinas Kehutanan Kabupaten: District Forestry Agency

Dinas Kesehatan

Kab.

Dinas Kesehatan Kabupaten: District Health Agency

Dinas Lingk. Hidup

Daerah

Dinas Lingkungan Hidup Daerah: District Environmental Agency

Dinas Pariwisata

Prov

Dinas Pariwisata: Provincial Tourism Agency

Dinas Pariwisata

Kab.

Dinas Pariwisata Kabupaten: District Tourism Agency

Dinas Pemukiman

Tata Ruang

Dinas Pemukiman Tata Ruang: Human Settlements Spatial

Planning Agency

Dinas Perhub Dinas Perhubungan: Transportation Agency

Dinas Perijinan Prov. Dinas Perijinan: Provincial Licensing Agency

Dinas Perijinan

Daerah Kab.

Dinas Perijinan Daerah Kabupaten: District Licensing Agency

Dinas Perikanan

Prov.

Dinas Perikanan: Provincial Marine and Fisheries Agency

Dinas Perikanan

Kelautan Kab.

Dinas Perikanan Kelautan Kabupaten: District Fisheries and

Extension Agency

Dinas Pertanian Prov. Dinas Pertanian: Agriculture Provincial Agency

Dinas Pertanian Kab. Dinas Pertanian Kabupaten: District Agriculture Agency

Dinas Peternakan

Kab.

Dinas Peternakan Kabupaten: District Livestock Agency

Dinas PUP or SDA Dinas PU/SDA Provinsi (PU Pengairan): Provincial Water

Resources Service

Dinas Tanaman

Pangan dan

Holtikultura

Dinas Tanaman Pangan dan Holtikultura: Food Crops and

Horticulture Agency

Dir. Jenderal BINA

MARGA

Directorate General Highway Engineering (Ministry of Public

Works and Housing)

Dir. Sungai Pantai

PUPR

Direktorat Sungai dan Pantai – Kementerian Pekerjaan Umum dan

Perumahan Rakyat: Directorate of Coastal River (Ministry of Public

Works and Housing)

Ditjen Perikanan

Budidaya

Directorate General of Aquaculture and Fisheries

DLH(-SU) Dinas Lingkungan Hidup (-Sumatra Utara): Provincial Environment

Department (- North Sumatra)

DMI Domestic, Municipal and Industrial (Water Demand): Rumah

Tangga, Kota dan Industri (Kebutuhan Air)

DMO Toba Destination Management Organization Toba:

DO Dissolved oxygen

DPSIR Driver, Pressure, State, Impact, Response concept

DSS Decision Support System, such as RIBASIM: Sistem Pendukung

Pengambilan Keputusan

xiv Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Abbreviation/

Indonesian term

Meaning/translation

DTA (Lake Toba) Daerah tangkapan Air (Danau Toba): Danau Toba Area or catchment area (Lake Toba)

ESDM Kementerian Energi dan Sumber Daya Mineral: Ministry of Energy

and Mineral Resources

Forum DAS Forum Daerah Aliran Sungai: Watershed Forum

Forum Komunikasi

Toba

Forum Komunikasi Danau Toba: Lake Toba Communication

Forum

FEWS/HYMOS Hydrological data processing system based on Flood Early

Warning System/Hydrological Modelling System: Proses Data

Hidrologi berdasarkan Sistem Peringatan Dini Untuk Banjir/Sistem

Pemodelan Hidrologi

FMSB Flood Management in Selected Basins (2004 – 2005):

Pengelolaan Banjir untuk Wilayah Sungai Terpilih

Germadan Gerakan Penyelamatan Danau: Lake Rescue Initiative

GFW Water Global Forest Watch Water

GGN Global Geopark Network

GIS Geographic Information System: Sistem Informasi Geografik

GOI Government of Indonesia: Pemerintahan Indonesia

Harian Analisa North Sumatra-based newspaper

HRM Human Resources Management: Pengelolaan Sumber Daya

Manusia

ICWRMIP Integrated Citarum WRM Investment program: Program Investasi

Sumber Daya Air Terpadu Citarum

IDBP Indonesian Domestic Biogas Programme

IFI International Financing Institution

(PT) INALUM PT Indonesia Asahan Alumunium; a state-owned company in the

aluminium industry (owner of hydroelectric power plant along

Asahan river)

(PT) INHUTANI Perusahaan Umum (PERUM) Perhutani: National Corporation for

Forestry (INHUTANI IV for North Sumatra)

IPAL Instalasi Pengolahan Air Limbah: wastewater treatment plant

IPLT Instalasi Pengolahan Lumpur Tinja: sewage sludge treatment plant

ISO International Organization for Standards

IWRM Integrated Water Resources Management: Pengelolaan Sumber

Daya Air Terpadu

JABO(DE)TABEK Area comprising (Daerah) Jakarta, Bogor, (Depok), Tangerang,

Bekasi

JSM Java Spatial Model: Model Spasial Jawa

Jurung A local fish

JWRMS Jakarta Bogor Tangerang Bekasi Water Resources Management

Study (1991 – 1995): Studi Pengelolaan Sumber Daya Air

JABOTABEK

JWRSS Java Water Resources Strategic Study (2010 – 2012): Studi

Strategis Sumber Daya Air (pulau) Jawa



xv

Abbreviation/

Indonesian term

Meaning/translation

Kabupaten/Kota District/City, autonomous administrative level within the province

Kantor Pertanahan

Kab./Kota

Kantor Pertanahan Kabupaten/Kota: District/City Land Office

Kecamatan Sub-district

Kelompok

Keagamaan

Religious group

Kel. Sadar Wisata Kelompok Sadar Wisata: Local tourism group

Kel. Tani Kelompok Tani: Farmers group

Kemen. Pariwisata Kementerian Pariwisata: Ministry of Tourism

Kemen. ESDM Kementerian Energi dan Sumber Daya Mineral: Ministry of Energy

and Mineral Resources

Kemenaker Kementerian Ketenagakerjaan: The Ministry of Manpower

Kemendagri Kementerian Dalam Negeri: The Ministry of Internal Affairs

Kemendus Kementerian Perindustrian: The Ministry of Industry

Kemenhub Kementerian Perhubungan: The Ministry of Transportation

Kemenkeu Kementerian Keuangan: The Ministry of Finance

Kemenko Ekonomi Kementerian Koordinator Bidang Perekonomian: Coordinating

Ministry of Economic Affairs

Kemenko Maritim Kementerian Koordinator Bidang Kemaritiman: Coordinating

Ministry of Maritime Affairs

Kemenpan Kementerian Pendayagunaan Aparatur Negara dan Reformasi

Biro: The Ministry of Administrative and Bureaucratic Reform

Kementan Kementerian Pertanian: The Ministry of Agriculture

KJA Keramba Jaring Apung: floating fish cages

KKP Kementerian Kelautan dan Perikanan: The Ministry of Marine

Affrairs and Fisheries

KLHK Kementerian Lingkungan Hidup dan Kehutanan: The Ministry of

Environment and Forestry

Kom. Transportasi Air Komunitas Transportasi Air: Water Transportation Community

Kom. Adat Komunitas Adat: Indigenous Community

Kom. Hutan Komunitas Hutan: Forestry Community

Kom. Pariwisata Komunitas Pariwisata: Tourism Community

Kom. Sungai Komunitas Sungai: River Community

Komisi Irigasi Komisi Irigasi: Irrigation Commission

KPTS Keputusan: decree (decision)

KSM Kelompok Swadaya Masyarakat: Local community support group

KSN Kawasan Strategi Nasional: National Strategic Region (NSR)

KSP Kantor Staff Presiden: President’s Office

KSPPM Kelompok Studi dan Pengembangan Prakarsa Masyarakat; Study

Group and Community Initiative Development

LIPI Lembaga Ilmu Pengetahuan Indonesia: Indonesian Institute of

Sciences

xvi Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Abbreviation/

Indonesian term

Meaning/translation

LMA Badan Otorita Pengelola Kawasan Parawisata Danau Toba: Lake

Toba Tourism Area Management Authority (the Lake Management

Authority)

LTEMP Lake Toba Ecosystem Management Plan: Rencana Pengelolaan

Ekosistem Danau Toba

LSM Lembaga Swadaya Masyarakat: Civil Society Organization, Non-

Governmental Organization

MFF Multi-tranche Financing Facility (for ADB loans): Fasilitas

Pembiayaan Multi Tranche

MIS Management Information System: Pengelolaan Sistem Informasi

MOHA Ministry of Home Affairs: Kementerian Dalam Negeri

MPS Memorandum Program Sanitasi: Agreed Sanitation Program

MPW Ministry of Public Works: Kementerian Pekerjaan Umum

N nitrogen

NGB Pangambatan, a location of PT Aquafarm Nusantara

NGO Non-Governmental Organization: Lembaga Swadaya Masyarakat

NRW Non-Revenue Water: water distributed by PDAM, but not paid for

NSR National Strategic Region: Kawasan Strategi Nasional (KSN)

O&M Operation and Maintenance: Operasi dan Pemeliharaan

OPEX Operational expenses, running costs

P phosphorous

Palawija Staple crops other than rice (coarse grains, pulses, roots and

tubers)

PDAM Perusahaan Daerah Air Minum: Regional Water Supply Company

PE Political Economy: Ekonomi Politik

PEA Political Economic Assessment: Kajian Ekonomi Politik

Penambang Galian C Penambang Galian: Mining Company

Perpres Peraturan Presiden: Presidential Regulation

Peternak Livestock Farmers

PHT Panahatan, a location of PT Aquafarm Nusantara

PIU Project Implementation Unit: Unit Pelaksana/Implementasi Proyek

PJT1 and PJT2 Perusahaan Umum (PERUM) Jasa Tirta: National Corporation for

Basin Management (I for Brantas, Bengawan Solo and Toba

Asahan and others, II for Citarum)

PKK Pembinaan Kesejahteraan Keluarga: Family welfare management

PLTA Renun Pembangkit Listrik Tenaga Air: Hydropower plant in the village of

Renun

PMU Project Monitoring Unit: Unit Pemantauan/Monitoring Proyek

Pola Rencana Framework for strategic management plans

PPSP Program Nasional Percepatan Pembangunan Sanitasi

Permukiman: National Accelerated Sanitation Development for

Human Settlements Program



xvii

Abbreviation/

Indonesian term

Meaning/translation

Prov. Provincial

PSDA Pengelolaan Sumber Daya Air: Water Resources Management

PTAN PT Aquafarm Nusantara

PT Jasa Marga A state-controlled toll road operator that constructs and provides

toll road services

PTL-BPPT Pusat Teknologi Lingkungan: Center of Environmental Technology

under BPPT

PU and PUPR Kementerian Pekerjaan Umum Dan Perumahan Rakyat: Ministry

of Public Works and Housing

PusAir Pusat Penelitian dan Pengembangan Sumber Daya Air Kemen

(PUPR): Agency for Research and Development in Water

Resources, under MPW

Pusat Bendungan Pusat Bendungan – Kementerian Pekerjaan Umum dan

Perumahan Rakyat: Center of Dam/Reservoirs under The Ministry

of Public Works and Housing

RBO/RBMO River Basin Management Organization: Balai Wilayah

Sungai/Balai Besar Wilayah Sungai/Balai Pengelola SDA Prov

RBT River Basin Territory: Wilayah Sungai (WS)

Rencana Master Plan for River Basin Management (follow up of Pola)

RMCU Road Map Coordination Unit: Unit Koordinasi Road Map

RIBASIM River Basin Simulation Model, DSS for WR Planning and

Management: Model Simulasi Wilayah Sungai - Sistem

Pendukung Pengambilan Keputusan Rencana Pengelolaan SDA

RPJMN Rencana Pembangunan Jangka Menengah Nasional: National

Medium-Term Development Plan

Sawah Rice field

SDA Sumber Daya Air: Water Resources

Sekr Kabinet Sekretaris Kabinet: Cabinet Secretariat

SH Stakeholder: Pemangku Kepentingan

SKPD Satuan Kerja Perangkat Daerah: Regional Working Unit

SSK Strategi Sanitasi Kota: City Sanitation Strategy

Sumatera Utera North Sumatra

Suri Tani Pemuka A private fish company, part of JAPFA

SWOT Strengths, Weaknesses, Opportunities & Threats: Kekuatan

Kelemahan Kesempatan dan Ancaman

TA Technical Assistance

Tala lata ripe ripe Onshore fish ponds containing fish that are periodically released to

Lake Toba after reaching a certain age and size

TKPSDA Tim Koordinasi Pengelolaan Sumber Daya Air: Basin water

resources management council

TMK Tomok, a location of PT Aquafarm Nusantara

TN Total nitrogen

Toba Pulp Lestari Name of pulp company

xviii Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia - Final Report


Abbreviation/

Indonesian term

Meaning/translation

Tokoh adat Local leader

Tokoh Masyarakat Public figure

ToR Terms of Reference: Kerangka Acuan Kerja

TP Total phosphorous

USDP Urban Sanitation Development Program: Program Pengembangan

Sanitasi Perkotaan

Unimed Universitas Negeri Medan

Univ. HKBP

Nomansen

Universitas HKBP Nomansen

URI University of Rhode Island

USU Univsitas Sumatera Utara: University of North Sumatra

WALHI Wahana Lingkungan Hidup Indonesia: Friends of the Earth

Indonesia

WISMP Water Resources and Irrigation Sector Management Program:

Program Pengelolaan Sektor Irigasi dan Sumber Daya Air

WLC World Lake Conference: Konferensi Danau se Dunia

WQ Water Quality: Kualitas Air

WQ Roadmap The development of the Roadmap for Improving Water Quality of

Lake Toba as a Tourism Destination

WRD Water Resources Development: Pengembangan Sumber Daya Air

WRM Water Resources Management: Pengelolaan Sumber Daya Air

WS Wilayah Sungai: River Basin Territory

WUA/P3A Perkumpulan Petani Pemakai Air: Water User Association

Yayasan Bina Sarana

Bakti

A foundation that produces organic vegetables

YPDT Yayasan Pencinta Danau Toba: Lake Toba Heritage Foundation

Exchange rate (November 3rd, 2017): IDR 13,495 = US$ 1 (xe.com)


Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia -

Final Report

1

1 Introduction

1.1 Background

1.1.1 Water quality concerns at Lake Toba

Lake Toba belongs to the largest and deepest lakes in the world. Although the minimum

estimated residence time of the lake is around 80 years1 (Lukman, 2010), there is a concern

about the deterioration of water quality in Lake Toba. Numerous studies have been conducted,

with more recent assessments illustrating that Lake Toba is showing signs of environmental

degradation. Water quality at 22 monitoring locations has deteriorated from “good” in 1996 to

“insufficient” in 2012 with an alarmingly high level of suspended solids and chlorophyll

concentration (DLH-SU, 2017). Unprecedented algae blooms appeared from January to April

2016 for the first time since water quality monitoring started in approximately 1929. This was a

clear manifestation of the presence of higher phosphate and nitrogen levels.

The largest pollutant loads originate from aquaculture, followed by animal husbandry and

domestic waste (including tourism). Several institutes and universities have carried out pollutant

source analyses to understand the pollutant load pathways in Lake Toba and advise the

Government on its carrying capacity. Although these analyses differ somewhat, they all show

roughly the same picture, which has been summarized by the Provincial Environment

Department for North Sumatra (Dinas Lingkungan Hidup-Sumatra Utara, DLH-SU) in its advice

on carrying capacity given to the Minister of Environment and Forestry. The total phosphorous

emissions from aquaculture nearly doubled between 2012 and 2016 (from 1082 tons in 2012

to 2124 tons in 2016; DLH-SU, 2017). In 2016 this contribution was equivalent to the loads of

approximately 2.3 million people. In contrast, the domestic waste pollution load in 2016 of 197

tons, created by a population of 0.5 million people living in the catchment area, was equivalent

to roughly 0.2 million people (because part of the human waste stays behind on the land). This

domestic load has not changed over the years, with agricultural and other pollutant sources

having even smaller contributions.

Local and commercial aquaculture production started in the mid-1990s and has increased

rapidly over the past two decades. Aquaculture started in 1996 in Haranggaol Bay, located in

the northeastern part of Lake Toba, after several years of agricultural crop failures. Following

the example of successful aquaculture in the Jatiluhur reservoir, local Haranggaol farmers

decided to try aquaculture and were soon followed by many other local communities around

Lake Toba. Commercial operations started in 1998 with PT Aquafarm Nusantara (PTAN),

followed in 2012 by PT Suri Tani Pemuka.

The fish cages have been controversial since their inception because of environmental

concerns from local communities, local, provincial and national governments and

nongovernmental organizations (NGOs). These concerns have been aggravated by a series of

sudden and large-scale fish kills. Almost all fish production in Haranggaol Bay was wiped out

in 2004 because of a severe Koi Herpes virus infection. Following this, aquaculture was banned

for two years untill 2006. Another large fish kill occurred in Haranggaol Bay in May 4, 2016

(Danaparamita, 2016), followed by another in Silalahi village. Both fish kills are thought to have

1 Residence time is discussed in more detail in section 2.2.4 and annex C.1.


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been caused by overstocking of the cages. Local NGOs subsequently launched a series of

court cases against the licenses of commercial aquaculture companies operating on the lake.

The Government has issued several instructions in response to the deterioration of water

quality. The Minister of Environment and Forestry issued a letter (menlhk/ppkl/pkl.2/4/2017) on

April 03, 2017 to ask the Governor of North Sumatra to establish the status of Lake Toba as

class 1, oligotrophic (see Annex C.3), with a maximum fish production in floating cages of

10,000 tons per year. This letter was followed by two provincial government decrees issued by

the Governor of North Sumatra on the lake status (no. 188.44/209/KPTS/2017) and re-affirming

the carrying capacity of 10,000 tons of fish production per year for Lake Toba (no.

188.44/213/KPTS/2017).

Pollution from livestock, mainly individually owned, is another water quality concern.

Unmanaged manure partly percolates into the soil and the rest finds its way via surface runoff

and drainage channels into Lake Toba. The same holds true for domestic wastewater. Very

few residents around Lake Toba are connected to a sewer network. Many of the current urban

on-site sanitation facilities do not comply with the definition of a septic tank and are more like

pit latrines, which means that polluted water leaks into the groundwater that in turn drains into

the lake. At times of high precipitation or floods, many tanks overflow.

There are several catchment land use considerations that also have implications for the water

resources of Lake Toba. Deforestation and land conversion have only a limited effect on the

water quality but impact the water resources of Lake Toba’s catchment area. As of November

2017, only two undisturbed forest patches remain, including the upstream forest in the

Sibuatan/Silalahi forest in the north-west of the catchment and the forest patches in the south-

east, including the forest of Taman Eden. The biodiversity in both areas is rich and the upstream

Sibuatan/Silalahi forest is particularly important for the water resources of Lake Toba as it

covers the upstream catchment of a large part of the run-of-river power plant from the Renum

River to Lake Toba. Large parts of the upper catchment of the Renum River have been

converted over the past 10 years. This has resulted in a significant reduction of up to 60% of

the base flow in the Renum River. Both remaining forest patches have no conservation status

and are severely threatened by local encroachment and conversion to agroforestry and timber

production (BWS-S2, see also www.globalforestwatch.org/map).

1.1.2 Rationale for roadmap

The tourism sector in Indonesia is a promising growth sector that can provide inclusive and

sustainable opportunities for economic development. The archipelago is home to one of the

most biodiverse habitats in the world having a rich array of tourism endowments that form the

underlying attraction for visitors. Indonesia has expanded the promotion of its natural resources

by increasing the size of protected areas and attracting more online interest in nature-based

activities. Despite this, Indonesia’s tourism industry is not operating at a level consistent with

the quality and diversity of its natural and cultural endowments, with environmental

sustainability as a key risk factor for the sector (WEF, 2017).

Four key constraints contribute to Indonesia not fulfilling its tourism potential. These include: (i)

continued poor and quality of infrastructure and services for citizens, visitors and businesses;

(ii) limited tourism workforce skills and private-sector tourism services and facilities outside of

Bali; (iii) weak enabling environment for private investment and business entry; and (iv) poor

inter-ministry/agency, central-local and public-private coordination and weak implementation



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capabilities for tourism development in general, and for monitoring and preservation of natural

and cultural assets in particular.

Through the National Medium-Term Development Plan (Rencana Pembangunan Jangka

Menengah Nasional, RPJMN, 2014) 2015-2019, the Government has set several objectives to

increase the role of tourism in the Indonesian economy. In early 2016 President Joko (Jokowi)

Widodo urged his Cabinet to accelerate the development of ten priority tourism destinations,

including Lake Toba. Recognizing the importance of integrated and sustainable tourism

development, the government plans to prepare integrated tourism master plans for each of the

priority tourism destinations, which are intended to provide a strong framework for effective and

sustainable tourism development.

The Government has launched the Indonesia Tourism Development Priority Program. For the

implementation of the program, the Government has decided to sequence the development of

tourism destinations, starting with three priority destinations: Lombok in West Nusa Tenggara

province; Borobudur-Yogyakarta-Prambanan in Central Java province and the Special Region

of Yogyakarta; and Lake Toba in North Sumatra province. If developed effectively, these three

distinctively different and unique destinations are expected to increase their combined annual

foreign and domestic visitor expenditures from an estimated US$1.2 billion in 2015 to US$1.5

billion by 2021 and US$2.0 billion by 2026. Lake Toba can become a more attractive destination

for a wider variety of predominantly domestic and some foreign visitors, particularly short haul

weekenders from Singapore and Malaysia (HHTL, 2017) 2.

1.2 Objective and approach

The objective of the Roadmap for Improving Water Quality of Lake Toba as a Tourism

Destination is to provide an understanding of the key drivers leading to water quality issues

along with costed investment scenarios associated with specific investments aimed at reducing

nutrient loads into the lake. The roadmap is intended to inform preparation of an Integrated

Tourism Master Plan that will provide a framework for effective and sustainable tourism

development in and around Lake Toba.

Safeguarding the water quality of Lake Toba is considered critical to ensuring the best-case

tourism development projections. The development of the Roadmap for Improving Water

Quality of Lake Toba as a Tourism Destination (hereafter “WQ Roadmap”) will provide inputs

to the government planning and budgeting process and to the Integrated Tourism Master Plan

for the Lake Toba tourism destination.

The Roadmap for Improving Water Quality of Lake Toba Tourism Destination has been developed through a series

of deliverables (

Table 1.1) and consultations (Annex A.2). This final report builds on all previous deliverables.

2 As part of the Tourism Development Project preparation, upon the GoI’s request, the World Bank conducted Demand

Assessments, prepared by Horwath HTL (HHTL), covering for each of the destinations: (i) baseline supply and

demand of tourism services; (ii) investment analysis; (iii) future market demand analysis (future visitors and

investors); and (iv) investment needs (destination infrastructure, tourism infrastructure, skills, firm capabilities, and

legal and regulatory environment). The Lake Toba report is available at:

http://bpiw.pu.go.id/uploads/20170302_Lake_Toba_Market_and_Demand_Assessment.pdf


Final Report


4

Table 1.1, List of deliverables

Task Deliverables

1 1. Inception Report/Literature Review

2. Stakeholder Assessment/ Mapping

3. Legal, Institutional and Political Economy Assessment

2 4. Lake and Catchment Assessment

3 5. Recommendations for Integrated Lake Basin Management Plan

4 6. Stakeholder consultations: PowerPoint Presentations and Workshops

1-4 7. Draft Final Report

1.2.1 Stakeholder consultations

The development of the WQ Roadmap followed an iterative process of consultation meetings

with identified stakeholders, coupled with specific analyses and a series of reports. These

reports have been discussed with stakeholders, thus creating a deeper understanding of

stakeholder roles and the legislative and institutional settings. This iterative process of

stakeholder consultation has helped to clarify roles and responsibilities, some of which even

changed during the process.

Pre-identified stakeholders, together with the participants of the Reference Group (sub-section

1.2.2), served as a starting point for the first stakeholder mapping exercises. During subsequent

meetings, the stakeholders themselves contributed to improved understanding of their roles

and responsibilities in monitoring and managing the overall catchment area of Lake Toba.

These consultations helped to complete the inventory of existing legal and institutional

arrangements, and in identifying additional stakeholders, while at the same time facilitating

access to information and data.

In addition to consultation meetings, stakeholders have also been involved throughout the

process through field visits and individual meetings (Annex 0). In some cases, semi-structured

interviews were conducted. These interviews served as a source of information on relevant

issues around Lake Toba and to understand the legislative and institutional settings, as well as

the political economy of the region.

1.2.2 Reference Group

A Reference Group was established by the Coordinating Ministry of Maritime Affairs and the

Ministry of Public Works and Housing to provide feedback and guidance throughout the process

(Annex A). This Reference Group included key experts and managing organizations involved

in environmental monitoring and management of Lake Toba and was the main contact group

to guide and assist in preparation of the WQ Roadmap. The Reference Group helped to identify

the historical and present arrangement of water quality management at Lake Toba and ensured

a comprehensive approach that builds on existing information to provide a solid foundation to

inform the preparation of the WQ Roadmap.



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1.3 Overview

Most chapters (and some sections) start with a description of the approach. Details of the

various tools and theoretical frameworks are included as annexes.

Chapter 2 introduces Lake Toba and its surroundings, the hydrology and functioning of the

lake, and key factors of the lake’s water quality problems.

In Chapter 3, the legal and institutional arrangements related to water quality at Lake Toba are

discussed. First, specific standards and institutions for water quality monitoring are discussed,

followed by the legislation and institutional aspects of water quality management. The chapter

concludes with an identification of various gaps between relevant laws and regulations and

their implementation in practice.

Chapter 4 provides an overview of the stakeholder mapping, followed by a stakeholder

assessment. Subsequently, the findings on the legal and institutional environment and

stakeholders are summarized in an overall analysis of the governance strengths, weaknesses,

opportunities, and threats (i.e. SWOT) for water quality monitoring and management.

In Chapter 5 the key factors causing the present state of Lake Toba are analysed. This chapter

includes a point and non-point source analysis with the Sumatra Spatial Model.

Chapter 6 summarises the present state of the water quality in Lake Toba. The quality of the

available data sets is assessed and subsequently the data have been analysed. Physical and

chemical parameters are discussed, together with an overview of available information on

nutrients, and organic content. Subsequently the thermocline depth is identified as well as

horizontal mixing and trends.

In Chapter 7 the autonomous growth developments are combined with various investment

scenarios to calculate future growth trajectories of the trophic state of Lake Toba. This supports

the identification of initial opportunities for water quality management.

In Chapter 8 responses have been formulated around a water quality management plan.

Interventions to address the most important drivers of water quality (aquaculture, livestock and

domestic wastewater) are elaborated, together with an assessment of the impacts on nutrients.

Contributions from other sectors are discussed as well.

Chapter 9 outlines a proposed water monitoring plan for Lake Toba based on a range of

assumptions that lead to different scenarios.

Chapter 10 summarizes the findings, conclusions and recommendations made in the previous

chapters.



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2 Lake Toba as a Tourism Destination

2.1 Lake Toba and its surroundings

2.1.1 Topography

Lake (Danau) Toba is the largest lake in Indonesia and one of the largest and deepest lakes in

the world (Annex B.1). The lake is about 100 kilometres (62 miles) long, 30 kilometres (19 mi)

wide, and up to 505 metres (1,657 ft) deep, with a volume of 240 km3 (58 cu mi). It is a volcanic

lake formed in the old caldera of the Toba Volcanic Complex situated on the island of Sumatra

along the Barisan Mountain Range (Figure 2.1). To the West lies the Indian Ocean and to the

East the lowlands of North Sumatra stretch out to the Malacca Strait. Steep cliffs, formed by

the caldera, surround the lake at an elevation of 400-1,200m above the lake level. As the

surface water level of Lake Toba lies at approximately 900m above sea level, the steep slopes

and volcanoes around the lake reach up to 2,100m elevation.

Figure 2.1, Topography of the catchment area of Lake Toba.


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8

The island of Samosir has a tilted surface with a maximum elevation of approximately 1,600m

above sea level or about 700m above the water level in the lake along the northeast side of the

island.

Around the lake to the northwest several volcanoes dominate the landscape. To the south a

larger relative flat valley with an approximate elevation of 1,200m above sea level is dominated

by cultivated land. Clearly visible in Figure 2.1 is the narrow valley to the east where the lake

overflows and discharges into the Asahan River. Here the water level regulation works have

been constructed and further downstream various hydro dams have been constructed. The

surrounding area is flat with the shores only a few meters above the lake surface.

The catchment area of Lake Toba and the Asahan River lies completely in the province of North

Sumatra, with a total of seven kabupaten bordering the lake, and another one (Pakpak Barat)

included in the national strategic region (Annex B.2). The largest populations can be found in

the relative flat areas along the west side of Samosir Island, along the south-east shore of Lake

Toba in Toba Samosir and around Prapat in Simalungun. As a result, most villages (desa) can

be found in those areas.

The soil in the region is typical for weathered volcanic areas and varies between light clay and

loamy sand (B.3). The four main soil types vary from somewhat sensitive to highly sensitive to

erosion (Damage Control Directorate of Aquatic Ecosystems, 2017). The soil type determines

runoff rates in the model (section 6.1).

2.1.2 Climate

The precipitation regime in the region is typical for the humid tropics and is characterized by a

major wet season from August through November and a minor wet season from March to May.

The months in between are transition-months with varying precipitation, never below 50 mm

per month (Table B.2). The average yearly precipitation in the region during the period 2003-

2016 amounts to approximately 2,850mm/year, with significant differences in total precipitation

from year to year. The average temperature is 21.5 degrees Celcius in the period 2006-2016,

and the annual reference evaporation is 1,556 mm (Hargreaves and Allen, 2003; Zomer et al.,

2008). See Annex B.4 for more details on climate.

2.1.3 Land-use practises and spatial development

Samosir Island is largely cultivated with upland plantations. Towards the west shores various

crops are cultivated. To the north are grasslands for cattle. Most tourist accommodations can

be found along the eastern shore and on the peninsula of Tuktuk. Along the cliffs of the caldera

to the east and southeast plantations can be found, while further to the north crops are

cultivated. The area is famous for its coffee plantations. To the west cattle are raised, and there

is a large pig farm. Down the slopes to the Indian Ocean forests are present. In the relatively

flat valley to the south rice and other crops are grown (Figure 2.2). The lake itself is used for

aquaculture with floating fish ponds that can be found all over the lake from north to south

(section 2.1.4).



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Figure 2.2, Land-use in the Lake Toba Catchment area, based on the 2013 dataset from BIG (Badan Informasi

Geofisika). Source of satellite imagery for this and other maps: Esri, DigitalGlobe, GeoEye, Earthstar Geographics,

CNES/Airbus DS, USDA, USGA, AeroGRID, IGN, and the GIS User Community.

In the catchment area of Lake Toba, most of the population (91%) live in rural settlements. Less

than 10% live in urban areas that together occupy 4% of the land. Some 10% of the land is

used as sawah to grow rice, 11% is occupied by plantations and on 27% other agricultural

dryland crops are grown. Aproximately a fifth of the land is covered by forest and another fifth

by shrubs, grassland and other natural vegetation. The various types of land use, as applied to

the Sumatra Spatial Model, are listed for each of the compartments in Annex J.3.


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2.1.4 Economy

Lake Toba and its surroundings provide substantial economic benefits to local people and

commercial enterprises. The average Gross Regional Domestic Product of the 8 districts

around Lake Toba was IDR 8.3 trillion in 2016 (at constant prices of 2010), with an average

growth rate of 4.8% in 2015 (Table 2.2; see also section 7.2.1). The main contributors to the

districts’ economy are agriculture, forestry, and fishing (includes aquaculture as well as

fisheries), together providing the major livelihood for the communities. Table 2.1 presents a list

of commodities produced in the area.

Table 2.1, Main commodities around Lake Toba (Ministry of Public Works and Housing, 2016)

Sector Commodities Location

Food crops and horticulture

Rice, corn, sweet potato, potato, andaliman, orange

Dairi, Simalungun (Haranggao Horison), Samosir (Panguruan, Palipi), Toba Samosir (Porsea, Sigumpar, and others), Humbang Hasundutan (Dolok Sanggul)

Plantation Coffee, incense, sweet skin, clove, candlenut

Samosir, Pakpak Bharat, Humbang Hasundutan, Tapanuli Utara, Karo

Rubber, cocoa, palm oil, tea

Humbang Hasundutan, Simalungun

Aquaculture Fish (Nila, Emas, Mujair)

Farming Pig, chicken, cow, buffalo

Simalungun (Dolok Pardamean)



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Table 2.2, Gross regional domestic product of Toba regencies by sector, based district-level data from the Central Bureau of Statistics, North Sumatra (in million IDR, at constant

price level of 2010).

Karo % Pakpak Barat % Dairi % Samosir % Humbang Hasundutan% Tapanuli Utara % Toba Samosir % Simalungun %

A Agriculture, Forestry Fishing 7,123,559.75 57% 425,784.11 59% 2,617,659.46 46% 1,385,461.90 53% 1,654,889.35 46% 2,431,668.98 48% 1,620,067.80 34% 13,203,969.70 56%

B Mining and Quarrying 30,634.33 0% 288.75 0% 3,727.68 0% 16,417.50 1% 21,046.74 1% 3,762.95 0% 14,008.70 0% 53,954.10 0%

C Manufacturing 387,997.37 3% 1,336.18 0% 18,954.53 0% 14,277.80 1% 56,471.72 2% 101,727.74 2% 524,576.50 11% 2,529,290.10 11%

D Electricity and Gas 11,302.38 0% 1,755.86 0% 5,186.49 0% 1,941.90 0% 3,437.86 0% 5,583.12 0% 4,132.40 0% 19,760.80 0%

E

Water supply, Sewerage, Waste

Management and Remediation Activities 10,217.54 0% 469.50 0% 5,079.92 0% 1,302.60 0% 2,434.12 0% 5,364.68 0% 2,462.40 0% 18,668.60 0%

F Construction 813,954.62 7% 65,821.24 9% 735,019.30 13% 267,911.90 10% 482,624.12 13% 635,966.05 13% 613,835.80 13% 2,037,563.00 9%

G

Wholesale and Retail Trade, Repair of

Motor vehicles and Motorcycles 1,243,155.78 10% 75,475.15 11% 920,838.25 16% 293,781.40 11% 524,852.23 15% 624,827.69 12% 762,992.10 16% 3,194,169.30 14%

H Transportation and Storage 560,896.99 4% 14,499.05 2% 209,413.35 4% 79,487.50 3% 87,213.74 2% 237,197.57 5% 141,297.70 3% 358,667.70 2%

I

Accommodation and Food Service

Activities 305,208.80 2% 16,144.65 2% 173,332.88 3% 127,683.10 5% 114,912.67 3% 112,940.47 2% 139,284.70 3% 205,646.50 1%

J Information and Communication 115,780.93 1% 5,785.70 1% 64,814.89 1% 26,617.80 1% 41,097.12 1% 47,653.29 1% 62,422.00 1% 165,234.50 1%

K Financial and Insurance Activities 159,881.14 1% 6,170.97 1% 115,168.38 2% 24,182.90 1% 41,312.07 1% 79,909.16 2% 81,873.40 2% 229,737.60 1%

L Real Estate Activities 391,078.37 3% 10,675.70 1% 148,766.37 3% 54,336.30 2% 95,420.12 3% 109,492.78 2% 134,491.40 3% 203,716.00 1%

M,N Business Activities 23,210.94 0% 135.23 0% 3,495.11 0% 3,054.50 0% 4,602.02 0% 14,254.06 0% 39,592.70 1% 19,094.30 0%

O

Public Administration and Defense;

Compulsory Social Security 695,684.32 6% 81,059.91 11% 521,808.68 9% 299,786.40 11% 382,968.00 11% 522,284.68 10% 450,008.00 9% 924,458.50 4%

P Education 314,507.22 3% 9,406.44 1% 108,117.93 2% 23,948.70 1% 36,991.10 1% 90,934.77 2% 132,378.60 3% 237,003.70 1%

Q Human Health and Social Work Activities 150,793.34 1% 2,917.53 0% 35,973.86 1% 13,750.20 1% 22,370.10 1% 39,919.53 1% 39,119.80 1% 83,729.00 0%

R, S, T, UOther Services Activities 157,003.60 1% 165.20 0% 1,093.84 0% 1,825.20 0% 5,105.97 0% 6,707.34 0% 7,261.30 0% 23,306.30 0%

Gross Regional Domestic Product 12,494,867.43 100% 717,891.17 100% 5,688,450.93 100% 2,635,767.60 100% 3,577,749.06 100% 5,070,194.85 100% 4,769,805.46 100% 23,507,970.00 100%

Gross Regional Domestic Product of Toba Regencies at Constant Price of 2010 by Industrial Origin (million rupiahs and percentage), 2016

IndustryNo


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Aquaculture is an important economic activity at Lake Toba; floating fish farm ponds populate the lake (Figure 2.3 and Figure 5.1). The aquaculture industry in Lake Toba can be divided into two types:

1. Industrial scale aquaculture by two companies, PT Aquafarm Nusantara and PT Suri Tani Pemuka;

2. Small-scale local aquaculture financed by domestic investors and local fisherfolk themselves.

Together the two commercial companies employ about 4,000 workers and the full production is exported to Europe and the United States. Financial details of the companies are not available to the public. Small to medium scale aquaculture enterprises produce primarly for the local market and are typically owner-operated, providing employment for more than 5,000 people. According to the Directorate General of Aquaculture and Fisheries (Ditjen Perikanan Budidaya, October 2015) there were at least 23,000 floating fish cages (KJA) in 2014. It is estimated (personal communucation Harian Analisa, June 5, 2017) that this amount of KJA provides direct employment to about 11,500 people for an average income of approximately IDR 60 million (US$ 4,450) per person per year.

Figure 2.3, Floating fish farms on Lake Toba (Photo by Aria Danaparamita, 2016).

The fish production at Lake Toba is not systematically monitored and estimates vary between sources and years (Table 2.3). In 2014 the 23,000 KJA were estimated to producing about 96,000 tons of fish, almost all red tilapia (Ditjen Perikanan Budidaya, October 2015). In 2015 the production dropped to about 84,800 tons and for 2016 estimates range from 64,000 to 74,400 tons (Table 2.3).



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Table 2.3, Estimated fish production in aquaculture at Lake Toba (in tons per year).

Producer

Estimated

production

2014

Estimated

production

2015

Estimated

production

2016

Estimated

production

potential

PT Aquafarm

Nusantara

34,000 30,000 30,000-40,000

PT Suri Tani

Pemuka

20,800 4,000 55,000

Haranggoal Bay 30,000 40,000

30,000-50,000

Other smallholders 30,000-50,000

Total 96,000 84,8003 74,400 64,000-96,000

Source Ditjen

Perikanan

Budidaya,

2015

DLH-SU,

2017

Discussions with

stakeholders,

2017

Estimation

2008-2016

Local aquaculture started in Haranggaol Bay around 1996 after several years of

agricultural crop failures due to fungus infections and overexploitation of the soils. The

succesfull introduction of the fish cages in Haranggoal was soon followed by many other

local communities around Lake Toba. Over time, many smallholders experimented with

fish cages at various locations on Lake Toba. Some abandoned their cages within a few

months, others moved their cages around to find the best location, and some aquaculture

farmers successfully produced fish for local restaurants that serve national and

international tourists.

In 1998, PT Aquafarm Nusantara started operation, as part of a joint Swiss

Government/Republic of Indonesia Investment Agreement (BKPM). This initiative was one

of the first pioneering bi-lateral socio-economic and development projects within

Indonesia’s fisheries and aquaculture sector (personal communication with PT Aquafarm

Nusantara, 20174). Following a request by the local government to stimulate the local

economy and employment, PT Suri Tani Pemuka, a national company, started fish

production in 2012 (personal communication with PT Suri Tani Pemuka). The Demand Assessment suggests that in 2015, approximately 7,000 persons worked in the tourism industry. Based on its best-case scenario, it forecasts around 10,000 people employed in the industry in 2026, and 15,000 in 2041. By 2041, spending by visitors to Lake Toba is expected to rise to US$275 million in the best case, from an estimated US$75 million in 2015.5 As Lake Toba will remain predominantly a domestic tourism destination, the majority of this projected spending increase (over 60 percent) will come from relatively lower-spending domestic visitors. Incremental economic impacts from an estimated five-fold increase in foreign visitors will therefore be more limited, reflecting the low starting

3 At the request of the Reference Group, the 2015 production level of 84,800 tons of fish has been used in the

assessment of nutrient loads for 2015 and in baseline scenario A. There was no agreement about the

production level in 2016, but various stakeholders suggested that the local small scale aquaculture production

might be under-estimated. 4 Letter from I Wayan Mudana, Director of PT Aquafarm Nusantara, to Deltares dated July 28th, 2017. 5 HHTL 2017 and World Bank staff estimates.


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level (only 60,000 visitors in 2015). The Lake Toba Tourism Area Management Authority (BOPDT) indicates that many investors have shown an interest in the area around Lake Toba in recent years, mainly with the intention of building hotels (Ratman, 2016; Gumelar, 2017 and Kumparan, 2017). BOPDT expects that after finalisation of road infrastructure, airports and ports, which is expected in 2020, investors will start their development activities. According to the Demand Assessment, the level of private investment in accommodation and other tourism-linked activities is expected to rise from only US$1.5 million per annum in 2015 to over US$15 million by 2041.6

2.1.5 Batak culture7

The hidden wealth in Lake Toba is comprised of non-financial resources including local

skills, trust and know-how, knowledgeable resource persons, and care-based

relationships. Lake Toba is an integral part of Batak history, culture, and spirituality. The

ancestors of Batak people chose Lake Toba as their permanent site for settlement

centuries ago. It was here that their descendants developed into the five ethnic Batak

groups; namely the Angkola-Mandailing, Karo, Pakpak-Dairi, Simalungun and Toba. Until

today, Lake Toba is a unifying point for Batak people who inhabit the surrounding lake as

well as those who migrated to other places.

For traditional Batak people, Lake Toba is valuable and important. In the pre-historic era,

the Batak’ view relies on its surrounding natural and environmental condition. Previously

there were strong beliefs in myths, legends, and historical inheritance through stories

shared verbally (some of which persist until today). One myth of Lake Toba stated that

Lake Toba began with a woman’s sadness over her husband telling their daughter an

important secret from her past, that she was previously a fish. She told her daughter to run

uphill because a huge disaster was about to come. When her daughter left, she prayed.

Soon there was a big earthquake followed by non-stop pouring rain. The whole area then

got flooded and became Lake Toba. The woman turned into a fish again and the man

became the island of Samosir. As such, Lake Toba is considered sacred by Batak people,

and there is plenty of local wisdom associated with Lake Toba.

Traditionally there are certain (unwritten) rules on dealing with waste, fish and the forest,

which need to be respected. In the past, anyone who bathed in Lake Toba and wanted to

urinate must come out of the lake, because of the strong belief that everyone should

respect the Lake. No one dared to throw garbage into Lake Toba. Violation of local wisdom

would have resulted in sanctions from local chieftains. In terms of fisheries, some local

wisdom includes the presence of no-fishing-zones, fish capture quotas (only certain

amount of fish and fish of certain size may be captured), as well as management of tala-

lata ripe-ripe (onshore fish ponds containing fish that are periodically released into Lake

Toba after reaching a certain age and size). The local wisdom to respect Lake Toba was

also extended into the forests surrounding the lake. No one would carelessly cut down

trees in the forests around Lake Toba. This local wisdom is only shared verbally through

word of mouth and not documented in written rules or customary guidelines, making it

challenging to reach new residents around the lake. However, much local wisdom as such

is eroded lately due to the large number of migrants and a change in economic activities.

6 World Bank staff estimates. 7 This section is largely based on Sianipar, 2011.



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2.2 Catchment hydrology and functioning of Lake Toba

2.2.1 Catchment dimensions and water level

The total area of the Catchment (including the lake) is approximately: 3,813km2, of which

the lake surface accounts for more than 1,100 square kilometers. The area around the

lake is very steep and as a result the sub-catchments are generally small (Table 2.4). A

total of 19 rivers drain into the lake, subdivided into 153 sub-catchments (Figure 2.4). The

catchments together provide an estimated at 111 m3/S or 3.5 billion cubic meters to the

lake through inflow.

Table 2.4, Lake Toba sub-catchment dimensions (Source: PU 4/2016)

Sub-catchment Size

Lake Toba 1,130km2

Samosir Island 653km2

Outside lake 2,030km2

Total 3,813km2

In addition to natural inflows from the catchment area into Lake Toba, an inter-basin

transfer from the Renun River was constructed in 1993 to augment water for the Renun

Hydropower Plant (PLTA). This tunnel diverts approximately 8-9m3/s on average and 20-

21m3/s during peak power supply (04:00-08:00hrs and 16:00-23:00hrs) (Figure B.5).


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Figure 2.4, The catchment and sub-catchment areas of Lake Toba.

The only outflow from Lake Toba is in the south-east, and drains into the Asahan River

with water flowing towards the Strait of Melacca. In this river, a regulating dam and several

hydro dams have been constructed. The objective of the regulating dam at Siruar is to

manage Toba outflow to the Asahan River in such a way that the Toba Lake water levels

are within the range required for various uses on site and downstream. Thus, the water

level is kept between 905.25m and 902.50m above sea level. This is done with a release

between 90 and 140m3/s to the downstream Asahan River. Annex B.5 shows the releases

as well as the resulting end-of-month Toba Lake water levels. The water balance for Lake

Toba is summarized in Table 2.5. For the model, an average flow of 110m3/s has been

selected; see Table 7.2 and Table 7.3 that also show the flows between compartments.

Table 2.5, Simplified water balance for Lake Toba

Total for lake

Variables Rate In (Mm3/year) Out (Mm3/year)

Precipitation 2850

mm/year

3,203.4

Evaporation 1556

mm/year

1,748.9

Inflow 56 m3/s 1,762.2

Inter Basin Exchange Renun 8 m3/s 252.3

Outflow (110 m3/s) 3,469.0

Total 5,217.9 5,217.9

2.2.2 Catchment erosion

The conversion of forests surrounding Lake Toba into other types of land use, coupled

with illegal logging and land and forest fires, have contributed to the deterioration in Lake

Toba’s water quality. This is because of the combination of major and minor nutrients,

trace elements, and natural organic compounds released by the erosion of Toba

watersheds that together stimulate algal growth.

The high rate of erosion in the catchment of Lake Toba is characterized by the abundance

of land parcels with very thin soil layers or areas with exposed bedrock, especially in hilly

areas with steep slopes. Approximately 27 percent of the catchment area is composed of

open land, grasses, and shrubs (KLHK, 2017). When the topsoil becomes thin due to

erosion, it is difficult to develop natural forests again. This problem is exacerbated by the

facts that the topography of the catchment is quite hilly with steep slopes and that the soil

types are sensitive to erosion (KLHK, 2017). According to the Minister of Environment and

Forestry, up to 21% of Lake Toba catchment areas have been identified as critical land

(Times Indonesia, 2016). Almost every year forest and land fires occurr, burning scrub and

trees, causing loss of cover vegetation and increasing vulnerability to erosion. Continued

erosion further complicates the growth of new vegetation as the soil layer gets thinner.



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The interactive map of Global Forest Watch (2016) indicates that there has been some

moderate tree cover gain over the past 12 years around Lake Toba. This may be the result

of multiple programs and projects on reforestation and rehabilitation that have been carried

out by different stakeholders. Tree cover loss is also recorded, primarily within and near

the concession areas of PT Toba Pulp Lestari near Parapat and to the west of Lake Toba.

2.2.3 Biogeochemical processes in Lake Toba

In deep lakes, such as Lake Toba, algal growth is typically limited by light. This is because

of the large epilimnion depth over which the algae are being mixed (see Annex C.2 for the

theoretical background on biochemical processes). The peak biomass concentration of

the algal bloom is determined by the availability of nutrients. Nutrient addition from run-off

(land activities) and direct input from aquaculture, can lead to higher nutrient

concentrations in the upper layer above the thermocline. This may thus lead to higher algal

biomass in the event of an algal bloom. Therefore, the hydrothermal stability of Lake Toba

is of major importance. Hydrothermal stratification is a key aspect which is further

discussed in sections 6.6 and 6.8.

2.2.4 Residence time and recovery time of Lake Toba

Residence time, or turnover time, is the theoretical time required to refresh a water body

(Annex C.1). The residence time is calculated by dividing the lake volume by the outflow.

For Lake Toba the residence time is approximately 80 years, because of the lake’s large

water body and the relative small outflow. This means that if Lake Toba becomes polluted

with a soluble toxic element, and the source of the pollution is eliminated, it will take more

than 80 years before the polluted water has left the reservoir and is replace with non-

polluted water. Consequently, changes in water quality may be irreversible as a result of

the long residence time of the water in the lake.

2.2.5 Stratification

Lake Toba is a stratified lake, which means that it is not fully mixed but consists of various

water layers that are characterized by different temperatures and oxygen concentrations.

Stratification is clearly visible in the temperature and oxygen profiles at various locations

in Lake Toba in 1992 (Figure 2.5). The profiles show temperature and oxygen ranges that

fall within the generalized temperature and oxygen ranges as reported for mayor

Indonesian lakes deeper than 100m (Lehmusluoto and Machbub, 1997). The mixing layers

(thermoclines) in these temperature profiles seem fairly large, but slightly more stratified

in the Northern basin.


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Figure 2.5, Thermal profiles of the north and south basins of Lake Toba, indicated in red (Source:

Lehmusluoto and Machbub, 1997).

Lake Toba can be classified as ‘warm monomictic’ based on the generalised relationship

between mean depth, surface area and lake stratification type, (see Figure 2.6; Lewis,

2000. Warm monomictic lakes are lakes that never freeze, and are thermally stratified

throughout much of the year. The density difference between the warm surface waters,

the epilimnion, and the cooler bottom waters, the hypolimnion, restrict lake water mixing

during much of the year. The period of stratification in tropical lakes is typically long, but

the stability of the middle (thermocline) layer is relatively low, and is influenced by wind

and rain events that cause partial mixing (Lewis, 2000). More on assessment of the

thermocline depth in section 6.6.



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Figure 2.6, Generalised relationship between mean depth, surface area and mixing patterns in tropical lakes

(adapted from Lewis, 2000).

2.2.6 Horizontal lake circulation and zonation

Water mixing in Lake Toba is not homogenous and the lake cannot be considered a

homogenous water body. This means that nutrient loading in the north does not

immediately affect nutrient concentrations in the southern part of the lake. Horizontal

circulation patterns are an unknown variable, influenced by flow velocities. Flow velocities

in Lake Toba have been modelled by the Indonesian Institute of Sciences, Lembaga Ilmu

Pengetahuan Indonesia (LIPI) under the influence of real occurring prevailing wind

directions (Figure 2.7; Rustini et al., 2014). The flow velocities are mostly below 0.2m/s,

which is normal for lakes. The resulting horizontal circulation patterns are shown in Figure

2.8. Both examples show cells of circulating water and no clear direction of flow. Northern

and southern parts do not mix intensively. However, current water quality estimates are

based on complete vertical mixing and complete horizontal mixing.

Lake divisions were proposed to explore the implications for water quality dynamics. These

are based on topography, bathymetry, circulation flow directions and velocities (Figure

2.8), and sampling sites (section 3.3) following the advice of Oakley (2015). Three options

were defined for the purposes of the analysis: 1) one compartment, looking at the lake as

a whole; 2) two compartments; and 3) four compartments (Figure 2.9). Future models

could consider additional compartments.

Danau TobaLake Toba


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Figure 2.7, Flow velocities as calculated by modelling Lake Toba (source: Rustini et al., 2014). Orange

indicates 0-0.20 m/s, yellow 0.20-0.40m/s, light green 0.40-0.60 m/s and dark green 0.60-1.00 m/s.

Clearly the outflow of the lake in the south-eastern part is seen, where flow velocities are locally

higher.

Figure 2.8, The circulation pattern in the northern (left) and southern (right) part of Lake Toba as modelled by

LIPI (Rustini et al., 2014). The image shows ‘cells’ of circulating water. The length of the arrows

indicates flow velocity.



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1 compartment – the lake as a whole

2 compartments: north and south lake

4 compartments: 1 northern and 3 southern lakes

Figure 2.9, Possible zonation options for Lake Toba (base maps adapted from Chesner, 2012).Indicative

flows for the whole lake in billion m3/year.

N

S1

S3

S2

N

S

1compartmentWholelake

2compartmentsNorthandSouthlake

4compartments1Northand3Southlake


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2.3 Key factors of Lake Toba water quality problems

The key water quality factors for Lake Toba are assessed following the Driver, Pressure,

State, Impact, Response (DPSIR) concept (Borja et al., 2006, Annex D). On the catchment

level, the drivers, land use changes (being pressures and state) and impacts are shown in

Figure 2.10. Together, these forecast the autonomous growth and investment scenarios

in the model. The main drivers of urbanization are population growth, household size

reduction, economic growth and job growth. The resulting urban area growth can have

serious impacts on the water resources.

Figure 2.10, Drivers of land use change and associated impacts.

In Figure 2.11 and Figure 2.12 an overview is given of all drivers and pressures linked to state and impacts as mentioned in the mechanism of eutrophication as described by Chapman (1996). Also the emission routes to the lake are shown in the links between drivers, pressures and “nutrient loading”.



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Figure 2.11, Schematic overview of drivers, pressures, state and impacts (part of DPSIR) of nutrient related water quality at Lake Toba (left part).


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Figure 2.12, Schematic overview of drivers, pressures, state and impacts (part of DPSIR) of nutrient related water quality at Lake Toba (right part). Inset: Overview of DPSIR.



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The DPSIR scheme identifies point and non-point sources that influence the Lake Toba

environment; these sources are quantified in Chapters 5 and 6. Table 2.6 shows the links

between drivers, pressures, environmental state and impacts for Lake Toba, with a focus on

possible water quality issues.

Table 2.6, Drivers, Pressures, State, Impact and Responses (DPSIR) for water quality in Lake Toba.

Driver Pressure State Impact Response

Agriculture Livestock: manure

management

Nutrient loading by P,

N runoff

Alg

al b

loo

m, T

urb

id w

ater

, Oxy

gen

dep

leti

on

, gas

eru

pti

on

s (p

oss

ibili

ty u

nkn

ow

n)

lead

ing

to p

oss

ible

eff

ects

: -

Dec

reas

e in

sw

imm

ing

wat

er q

ual

ity,

-

Low

er a

qu

atic

bio

div

ers

ity,

sh

ift

in k

ind

s o

f sp

ecie

s,

- Lo

ss o

f n

ativ

e fi

sh a

nd

fis

h p

rod

uct

ion

cap

acit

y,

- Lo

wer

aes

thet

ic v

alu

e.

Measures to reduce livestock runoff

(unknown)

Agriculture Paddy: fertilizer use Fertilizer management program;

WWT irrigation

Agriculture Plantation: fertilizer use Fertilizer management program;

WWT irrigation

Agriculture Other agriculture: fertilizer

use

Fertilizer management program

Aquaculture Industrial scale

aquaculture: feed, fish

faeces, dead fish Nutrient loading by

direct input of P, N

through feed

Limit tonnage produce, improve

Feed Conversion Ratio

Aquaculture Local aquaculture: feed, fish

faeces, dead fish

Limit tonnage produce, improve

Feed Conversion Ratio

Domestic Urban population: organic

waste, faeces, waste water Nutrient loading by

river discharges of P,

N per person day

Centralised Waste Water Treatment

(Domestic)

Domestic Rural population: organic

waste, faeces, waste water

Septic Tank

Forestry Plantation: fertilizer use,

erosion Nutrient loading by

runoff and

subsequent discharge

from rivers of

(natural) emission of

P, N

Waste Water Treatment (Irrigation)

Land cover

(other)

Grass/other none

Land cover

(other)

Shrub none

Land cover

(other)

Forest none

Tourism Tourists in large hotels

Nutrient loading by

emission of P, N per

tourists day

Waste Water Treatment (Hotel)

Tourism Tourists in small hotels and

homes

Centralised Waste Water Treatment

(Domestic)



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3 Legal and Institutional Environment

3.1 Approach

A stepwise approach identified legal and institutional aspects relevant to the monitoring and

management of water quality in Lake Toba (adapted from Fritz et al. 2009, 2014). First the

specific problem is diagnosed, identifying any dysfunctional legal and institutional patterns. This

is followed by an analysis to determine why the observed patterns are present. In the response

chapter (chapter 8) ways forward are then identified. The legal and institutional assessment is

closely linked to the stakeholder assessment (see chapter 4).

Various laws, government regulations, presidential regulations, presidential decrees,

ministerial regulations, ministerial decrees, and governor decrees address water quality in

Indonesia. A list of all relevant laws is presented in Annex F. In most of these, water quality

monitoring and management are considered in unison and a distinction between these two

cannot easily be made in the Indonesian Water Resources Law of 2004. However, for the WQ

Roadmap the two dimensions of water quality monitoring and management have operational

importance. Hence, where possible and relevant these are discussed separately. An overview

of concerns, plans, efforts, and legal and institutional settings is maintained and provided by

the Lake Rescue Initiative (Germadan) for Lake Toba (KLHK, 2017). This has been an

important source of information for this chapter.

3.2 Standards for monitoring

Several standards for water quality apply to Lake Toba and provide legal guidance for

monitoring. In addition to national government legislation in Indonesia (Figure 3.1), voluntary

international standards for aquaculture are applied by commercial ventures.


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Figure 3.1, Overview of official water quality standards for Lake Toba over time, as part of the legal framework in Indonesia.



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3.2.1 Oligotrophic status and class 1 standard

Government Regulation No.82 of 2001 sets the water standard for drinking water in Indonesia.

Following that regulation, the governor of North Sumatra in 2009 classified Lake Toba as Class

1 Raw Water for drinking water through the Governor’s Regulation No.1 Year 2009. The

Governor’s regulation also set the water trophic status of Lake Toba as Oligotrophic. Although

this regulation provides a clear standard for Lake Toba’s water, the water quality of Lake Toba

has deteriorated to mesotrophic for several variables in most compartments (see section 6.10).

Discussion on Toba’s water standards re-emerged in 2017. After several years of intensive

investigation by institutes like LIPI, Environmental Provincial Agency (DLH-SU), PusAir and

several universities, the target water quality standards and required trophic state of lake Toba

were confirmed by the Minister of Environment and Forestry, in her letter on April 3, 2017 to

the Governor of North Sumatra8. The letter indicated that:

• The water quality of Lake Toba should meet class I (raw water for drinking water), as per

the standards set by the Government in 2001 (82/2001), and the classification of Lake Toba

by the Governor in 2009 (1/2009, chapter 5).

• The trophic status of Lake Toba is defined as oligotrophic in the Governor’s Regulation No.1 Year 2009.

• The maximum carrying capacity for fish cultivation in Lake Toba is set at 10,000 (ten thousand) tons of fish per year from fish cages (Keramba Jaring Apung, KJA).

The letter of the Minister of Environment and Forestry was a confirmation of the status of Lake

Toba as well as an instruction on the carrying capacity. This instruction was based on the

various studies mentioned above. The letter was followed by the Governor of North Sumatra’s

Decrees 188.44/209/KPTS/2017 and 188.44/213/KPTS/2017. These decrees made the

instructions on the pollution load and carrying capacity of Lake Toba legally binding. The

decrees also served to instruct the sub-national government officials and district heads on the

water quality maintenance of Lake Toba. The decrees confirmed the Minister’s letter and

passed it on to direct guidance for keeping the nutrient levels near zero. This means that source

pollution control became one of the key parts of the environmental management of Lake Toba.

DLH-SU confirmed this directive with the Governor, and provincial regulations followed the

recommendations by the Minister. However, regarding the limitation of aquaculture, the Ministry

of Marine Affairs and Fisheries would like to communicate further to determine the maximum

production level and look for alternative incomes for fish farmers. No consistent data are

available on the exact fish production over the years, especially because the total production

of local small and medium scale aquaculture is not monitored. Various stakeholders suggested

that the local small-scale aquaculture production might be underestimated. Numbers for total

production vary between 64,000 and 96,000 tons of fish produced per year between 2014 and

2016 (Table 2.3). As there appeared to be consensus9 about the 2015 production level of

84,800 tons of fish, that value has been used in this study. The Ministry indicates that some

time should be given to the investors and proposes a five-year implementation period, ensuring

compliance with the provincial regulations. The Ministry is still in the process of collecting

responses of other authorities mentioned in the letter (i.e. the eight districts around Toba).

8 MENLHK/PPKL/PKL.2/4/2017. The letter was copied to Coordinating Ministry of Maritime Affairs, Ministry of Public

Works and Housing, Ministry of Marine Affairs and Fisheries, and the eight districts surrounding Toba. 9 Among the members of the Reference Group.


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Although the letter of the Minister and the Governor’s Decrees allow for immediate further

action, and although the letter already included the eight districts, the letter was not addressed

to the Minister of Home Affairs. Based on the lessons learned from the past, the involvement

of the Minister of Home Affairs is crucial to provide clear direction to the different districts for

implementation. The roles of these and other governmental and non-governmental

stakeholders are elaborated in the next sections and in chapter 0.

3.2.2 Aquaculture Stewardship Council (ASC) Standards

On top of the oligotrophic status and Class 1 Standard set in the Governor’s Decrees,

commercial aquaculture in Lake Toba abides, voluntarily, by the regulations and principles of

the Aquaculture Stewardship Council (ASC)10. The two commercial aquaculture farms at Lake

Toba, PT Aquafarm Nusantara (PTAN) and PT Suri Tani Pemuka have been certified by the

ASC. This certificate indicates that all fish production activities have a minimal environmental

and social impact. ASC principles focus on: compliance with national and local regulations,

conservation of local habitat and biodiversity, preservation of water quality and water resources,

social responsibility and human welfare.

According to the most recent publication of the ASC Tilapia Standard, V1.1 2017, diurnal

dissolved oxygen fluctuation was selected as a practical parameter for limiting the effects of

eutrophication on a particular water body. However, it was considered necessary to go beyond

an oxygen criterion to protect waters that have low nutrient concentrations and where the

diurnal dissolved oxygen fluctuations are minimal; i.e., oligotrophic systems. To avoid the

excessive loading of nutrient-poor systems, a limit on the total phosphorus concentration in

these oligotrophic receiving waters has been imposed. Additionally, a limit on the concentration

of chlorophyll α has been established to restrain the productivity in these water bodies.

Water quality requirements for ASC with respect to eutrophication:

- The relative change in diurnal dissolved oxygen of receiving waters relative to dissolved

oxygen at saturation for the water’s specific salinity and temperature ≤ 65%

Additional water quality requirements for ASC with respect to oligotrophic receiving waters:

- Maximum diurnal change in percentage of dissolved oxygen is 65%. - Maximum Secchi disk visibility limit is 10 meters. - If Secchi disk visibility is equal to or less than 5 meters then:

o Maximum total phosphorus concentration limit in water is ≤ 20 μg/l o Maximum Chlorophyll α concentration in water is ≤ 4 μg/l

- Maximum amount of phosphorus added to culture system per metric ton of annually produced fish is ≤ 27 kg.

- Maximum amount of phosphorus released from culture system per metric ton of annually produced fish is ≤ 20 kg.

The standards prescribe that measurements shall be taken at the Receiving Water Farm Afar

(RWFA) sampling station. The RWFA is a point where the farm effluent has an influence in the

10 The Aquaculture Stewardship Council is an independent international non-profit organisation that manages the world’s

leading certification and labelling program for responsible aquaculture.



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receiving waters but is not in the immediate outfall/mixing zone. This location would be

downstream in a river, or down the prevailing current pattern in a lake, reservoir or estuary.

Note that, although additional requirements are set for oligotrophic waters, a quantitative

definition of the term ‘oligotrophic’ is not provided in the ASC Tilapia Standard. The

requirements above do imply that water bodies with an average annual Secchi disk visibility at

or above 10 meters are not permitted as receiving waters under the ASC Tilapia Standard

because of their ecological uniqueness and rarity. The implications of this for Lake Toba are

discussed in sections 6.3.3, 6.9.1, 6.9.2, and 8.2.1.3.

3.3 Institutional arrangements for monitoring

Several institutions conduct water quality monitoring activities in Lake Toba. These institutions include a range of public and private institutions with skilled personnel and equipment to monitor the water quality of Lake Toba. Of all the monitoring efforts done, the most important aspect in quality of water sample analysis is the consistency of the laboratory chosen. This allows for a more objective and consistent comparison between samples over time. The four major water quality monitoring institutions are described below.

3.3.1 Provincial Environment Department – North Sumatra (DLH-SU)

The Provincial Environment Department (till 2016 known as BLH, Badan Lingkungan Hidup, the Provinvial Environment Agency) of North Sumatra (DLH-SU) is tasked with the general monitoring role of the lake’s water and provides a signal function. The agency has 22 monitoring locations distributed over the whole lake that have been measured over a period of 10 years with a frequency of once or twice per year.


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Figure 3.2 shows the location of the 22 sampling points in 2016. The choice of monitoring locations is based on the coverage of the larger bays, inhabited coastline and aquaculture locations along the coastline to capture pollutant loads and effects. Overall, the frequency is aimed at monitoring long term trends in lake status (over decades), not short-term changes. DLH-SU focusses on parameters near the shore, as DLH-SU consider these near-shore monitoring points to be connected to local pollutant sources.



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Figure 3.2, Overview of the 22 locations sampled by BLH-SU (currently DLH-SU) in 2016, based on data from DLH-

SU, 2016.

3.3.2 Indonesian Institute of Sciences (LIPI)

As a research institute, LIPI seeks to understand the Lake Toba System for exploratory and scientific purposes. The institute has conducted various measurement campaigns across a range of locations and parameters. It has data of measurements starting in 2009 in which the analysis was carried out in LIPI’s own laboratory. The particular spatial distribution of sampling locations was selected with the aim to cover the deeper central parts of the whole lake to collect useful depth profiles (Figure 3.3). LIPI focuses on characterizing the lake itself by selecting only mid-lake monitoring points. LIPI is developing a 3D hydro-dynamic model for the lake in which the horizontal and vertical circulation is modelled dynamically. Such a 3D model of the lake circulation is primarily for future use, when more data are available to operate and verify the model.


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Figure 3.3, Overview of the 12 stations sampled by LIPI in 2009, based on information from LIPI (2009).

3.3.3 River Basin Operator (PJT1)

Perusahaan Umum Jasa Tirta (PJT) is the national corporation for basin management. PJT1

is the corporation responsible for the Brantas, Bengawan Solo, Toba Asahan and other river

basins. PJT2 is responsible for the Citarum River basin. In Presidential Decree No. 2/2014

(section 3.4.2) the President appointed PJT1 for operational lake management, with a role and

mandate on management of surface water sources in Toba-Asahan. PJT1 collects fees for the

management and monitoring of the lake. PJT1 is planning to build its own monitoring laboratory

near Parapat, North Sumatra to support its lake management efforts. PJT 1 has recently started

monitoring water quality (Figure 3.4; Annex G).



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Figure 3.4, Overview of the sampling locations of PJT1, based on information from PJT 1 in 2017.

3.3.4 PT Aquafarm Nusantara (PTAN)

Aside from monitoring efforts by government institutions, private stakeholders are interested in

water quality data of the lake and have their own monitoring efforts. For example, PT Aquafarm

Nusantara (PTAN), one of the two large aquaculture companies11, needs data for its

Aquaculture Standard Certification (ASC). It therefore needs to understand the effect of

aquaculture activities overtime on the lake system, especially on areas where the activities take

place. They have 4 monitoring locations, three of which are located at the center of fish farm

areas: Panahatan, Tomok and Pangambatan (Figure 3.5). The fourth station is located in the

centre of the lake (CL), and provides a reference as it is assumed not to be affected by the fish

farms. These data have been measured over a period of 10 years with a monthly frequency. At

one of the locations a temperature and oxygen profile is available over the full period. PTAN

uses on-site labs and these are periodically quality-checked by Wageningen University and

Research in the Netherlands. PTAN is focusing on their aquaculture farms and has one

reference point.

11 The other company out-sources water quality monitoring.


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Figure 3.5, Overview of Lake Toba catchment (top) and area with the 4 sites sampled by PTAN (bottom).

Panahatan (PTH), Tomok (TMK) and Pangambatan (NGB) are aquaculture locations (TMK was closed in

2008), CL is a control location in the middle of the lake. The color coding has been consistently applied in all

PTAN graphs.

3.4 Legal arrangements for water quality management

Various laws and institutional arrangements are in place for water quality management at Lake

Toba, at provincial, national, and international levels. The central level provides guidance,

evaluation and monitoring. Each ministry has its own scope, with implementation at the

provincial or district level. The processes that lead to the development of laws and regulations

sometimes overlap, as can be seen in the overview over time in Figure 3.6.



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Figure 3.6, Overview of legislation and formal institutional arrangements on Lake Toba over time. Note that the first fish cages appeared at Lake Toba in 1996.


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3.4.1 Provincial setting

Multiple efforts have been undertaken by different levels of government to protect and

safeguard Lake Toba. At the provincial level, in 1990, the Governor of North Sumatra issued a

Regional Plan with special attention to the protection and management of Lake Toba. In 2003,

through Provincial Regulation No. 7/2003, a provincial spatial plan was developed. Based on

this spatial plan, the Asahan Authority and the North Sumatra Provincial Government

developed the Lake Toba Ecosystem Management Plan (LTEMP) in 2004, which later formed

the basis for the Germadan developed by the Ministry of Environment (BKPEKDT, 2005;

Soeprobowati, 2015).

Law No UU 23/2014 regarding Sub-National Governance is a national level law, giving authority

to the provinvial levels, making them responsible for various basic services. This

decentralization law covers various sectors including Education, Health, Drinking Water,

Drainage, Wastewater, and Solid Waste, to name a few. One of the regulations includes the

Minimum Service Standards, in which the formal document is still a working draft. Based on

this law, district heads (heads of local government) are obliged to reach their target as their key

performance indicator, especially for drinking water and wastewater.

3.4.2 National setting

The LTEMP was one of the key inputs in 2009 for the 1st National Conference of Lakes in

Indonesia, which was organized to save and manage not only Lake Toba but also other

degrading lake ecosystems around Indonesia. The Conference resulted in the 2009 Bali Lake

Agreement, whose aim is to maintain, preserve and restore lakes’ functions based on balanced

ecosystem principles as well as environmental carrying capacity. This would be done through:

1. Management of lake ecosystems,

2. Utilization of lake water resources,

3. Development of lake monitoring, evaluation and information systems,

4. Formulation of adaptation and mitigation steps to prepare for climate change,

5. Strengthening of institutional capacity and coordination,

6. Enhancement of community roles and participation,

7. Sustainable financing.

The Agreement was supported by eight ministries (Environment, Home Affairs, Public Works,

Agriculture, Energy and Mineral Resources, Marine and Fisheries, Culture and Tourism, and

Forestry) and one agency (Agency for the Assessment and Application of Technology, BPPT).

While the ministries formally have a “willingness to collaborate with all parties”; the Agreement

was not legally binding. It included a first set of 15 priority lakes, including Lake Toba. In 2014,

all institutional and legal arrangements were nearly completed for full scale implementation of

the Agreement. The Ministry of Public Works and Housing prepared the draft Government Lake

Regulation (without a number assigned). However, in February 2015 the Water Resources Law

7/2004 was cancelled by the Constitutional Court (order No. 85/PUU-XI/2013). Lacking a legal

basis, the process came to a standstill and the Bali Lake Agreement (including the Germadan)

was not implemented. Consequently, the Lake Toba Ecosystem Management Plan (BKPEKDT,



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2005) was not implemented either, as it did not provide any legally binding implications for the

district and local levels. As a result, the Ministry of Home Affairs never adopted the plan as a

priority program.

In 2008, through the Government Spatial Planning Regulation No. 26/2008, Lake Toba area was named a National Strategic Region (NSR). Presidential Decree No. 2/2014 appointed PJT1 for operational lake management, with a specific role and mandate on management of surface water sources in Toba-Asahan. Both NSR and PJT1 are referred to as “initiative”: NSR because Lake Toba became a strategic tourism area. Also, PJT1, unlike BWS Sumatera II, is profit-oriented and can collect fees. The Decree was followed by two Presidential Regulations: Presidential Regulation No. 81/2014 and Presidential Regulation No. 49/2016. Through Presidential Regulation No. 81/2014 the NSR status was further strengthened and PJT1 was assigned the tasks to:

• manage the catchment area to maintain the sustainability of water resources and minimize

erosion to prevent sedimentation;

• maintain the water quality and manage the land and water contamination; and

• protect biodiversity and a sustainable biological production for local communities.

This Presidential Regulation also gives guidance on fisheries practices (Clause 8 (5) a, b, c, d),

in which aquaculture activities should occur at least 10 meters from the shore. The permits for

aquaculture activities issued by the districts also require the fish cages to be located only in

zones where the water depth is more than 100 meters. Based on this Presidential Regulation,

the Provincial Spatial Plan for North Sumatra (RTRW) has been formulated and was passed

as Provincial Regulation No. 2/2017 on January 13th, 2017 (Bisnis.com, 2017). PT Suri Tani

Pemuka tried to comply and moved the fish cages further onto the lake. However, as the cages

could not withstand the larger wave action further away from the shore, the cages were moved

back. No other efforts to comply have been observed.

In 2015, partly stimulated by the upcoming International World Lake Conference (WLC, Bali

2016) and also to address a large concern regarding the rapid degradation of many lakes in

Indonesia, the Ministry of Environment and Forestry started the Lake Rescue Initiative (or

Germadan) as a follow-up to restart the 2009 Bali Lake Agreement. At the Bali 2016 World

Lake Conference, a priority Lake Program was initiated whereby:

• Ministry of Public Works and Housing made IDR 330 billion (US$ 25 million) available for

the restoration and safeguarding of seven priority lakes, including Lake Toba;

• Ministry of Environment and Forestry issued Germadan Initiative as part of RPJMN 2015-

2019. This encompassed 15 priority lakes, including Lake Toba. The Germadan Initiative

was sent to the Coordinating Ministry for Economic Affairs for implementation.

Germadan Toba attempts to review all the regulations related to Lake Toba and analysed the

gaps in the overall management of Lake Toba, including its surroundings. It offers a set of

recommendations and timeline for different aspects of Lake Toba Management. In terms of

implementation of the recommended actions, so far, the Ministry of Environment and Forestry,

together with the Provincial Forest Service, have implemented a reforestation program. In this

program, members of the community are invited to manage 10 hectares of forest, for which

they get permission to plant 1 hectare with whatever trees they want. Nevertheless, the

stakeholders expressed fears that the Germadan is at risk of becoming yet another review or

planning document with little impact or no implementation because it does not legally bind the

stakeholders mentioned in the document to conduct certain actions.


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Indonesia’s Medium Term National Development Plan for 2015-2019 contains numerous

targets to be achieved by 2019. Few of them include the national target to achieve universal

water and sanitation access. This means 100 percent coverage for drinking water with 15 litres

per capita per day, sanitation, and rehabilitation of up to 5.5 million hectares of critical lands.

Priority is given to improvement of the urban solid waste situation for the period 2015-2019.

These targets act as guidance for management efforts on Lake Toba’s waters as well.

At the national level, several specific ministerial regulations act as guidelines to manage many

aspects of Lake Toba’s water. For example, on water usage, there are Ministry of Public Works

and Housing Regulation No. 9/2015 on water resources utilization and Ministry of Public Works

and Housing Regulation No. 37/2015 on the licensing of water use.

On wastewater, guidelines are provided in the Ministry of Environment and Forestry Regulation

No. 68/2016 on standards of wastewater management and in the Ministry of Public Works and

Housing Regulation No. 4/2017 on domestic wastewater management systems. For

implementation, the Regional Planning Agency and Ministry of Public Works and Housing

assembled working groups to prepare a Sanitation Strategy for Districts and Cities (or SSK).

The SSK prepared by working groups in the Lake Toba area so far only considers domestic

wastewater and does not consider waste from industry or aquaculture. On top of this, the

working groups have established sanitation roadmaps at province and district-level. One of the

requirements to submit a request for funding (sanitation budget proposal), is the establishment

of Local Community Support Groups (or KSM) to encourage local participation. Several of these

community groups already exist in the Lake Toba area. Other active groups at the community

level include Family Welfare Management Groups (or PKK).

The Presidential Regulation No. 49/2016 was issued to accelerate Lake Toba as a tourism

destination. In early 2016 President Joko (Jokowi) Widodo urged his Cabinet to accelerate the

development of the ten priority tourism destinations, including Lake Toba. The Regulation

instituted a new body, the Lake Toba Tourism Area Management Authority. The Coordinating

Ministry for Maritime Affairs is appointed as chair of the board. Presidential Regulation No.

49/2016 provides the Lake Toba Tourism Area Management Authority with (in article 2.2.2) the

authorization to develop a new tourism area of about 500-600 hectares and (in article 2.2.1)

the coordinating role for the area included in the Presidential Regulation 81/2014. This latter

area covers the whole of Lake Toba and its riparian land.

3.4.3 International setting

In 2014, Toba Caldera was designated by the President of Indonesia as a National Geopark of

the Republic of Indonesia with its distinct features as having a caldera of a super volcano and

uniqueness as the largest Quaternary Tectonic-Volcano in the world. The Toba Caldera was

targeted to be part of the Global Geopark Network (GGN) of UNESCO. The Lake Toba Tourism

Area Management Authority and the Executing Agency of Geopark Caldera Toba have

submitted their request for registration and are (as of February 2018) waiting for formal approval

by the GGN of UNESCO. If approved, the Government of Indonesia will be responsible to

maintain the ecological, archaeological, historical and cultural values with respect to local

economic development through conservation, education and tourism.



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3.4.4 Licensing and permits

Based on government regulation no. 69 (2014), any request for water usage of Toba should be

submitted to the Ministry of Public Works and Housing (PUPR). Such license proposals must

include a technical recommendation from the technical agencies at district or provincial level.

All recommendations must be approved by the water resources manager (BWS-S2). Applicants

can start the process by trying to get this recommendation first and then submit the complete

file to the Ministry. The technical recommendation includes technical concerns and considers

issues such as the type of water use, whether it is allowed at all; the location of the intended

water use; how the water will be taken and used; how, in the case of buildings or facilities, these

are designed; whether the intended water use will influence the water balance (neraca); and

what is the current condition of Lake Toba. Based on the technical recommendation, the

Ministry then makes one of three decisions: return the proposal and ask for more required

documents; issue the license (for a maximum of 10 years); or reject the proposal.

Typically, the licensing authority is located at the provincial and district levels. For international

investors, the central level plays a role, though this is a principle permit based on

recommendations from the province or district level. If permit requests are denied at the central

or provincial level, or if the process of technical recommendation takes too long, requesters

apply at the district level. There are no district-level services from the Ministry of Marine Affairs

and Fisheries in all districts, so at this level technical recommendations cannot always be

provided. As a result, despite the guiding rules that the process for issuing licenses should be

the same at all levels of government, permit granting at the district level tends to be more lenient

than at the provincial level.

3.4.4.1 Licensing for aquaculture

Local aquaculture started in Haranggaol Bay around 1996 with support from the local district of

Simalungun. The districts agreed with these new activities as they contributed to reducing the

high unemployment rates in the area. No formal licenses have been issued for the production

locations operated by local communities in Haranggaol Bay or elsewhere around Lake Toba.

However, the total local production potential, based on the number of cages, was estimated at

about 50,000 tons of fish annually in 2015.

Between May 2016 and June 2017, some of the district governments around the lake requested

the local communities to abandon aquaculture, because its foul odours hamper tourism and out

of concern for the water quality. Since then, many local fish cages have disappeared or are no

longer maintained. According to a fish farmers’ association, local aquaculture farmers in

Haranggaol have not received such a request from their local authorities, the Simalungun

district. Since the request of the local district governments, the estimated potential for small

scale production by communities has dropped to around 40,000 tons per year, most of it in

Haranggoal Bay.

Large and foreign commercial fish farms follow different procedures. For PT Aquafarm

Nusantara, being a foreign company, the license agreement was issued in 1998 through the

Investment Coordinating Board (BKPM) (personal communication with PT Aquafarm

Nusantara12). This license allows PT Aquafarm Nusantara to produce 36,000 tons of fish per

year. It is unknown when this license might expire. During the past few years PT Aquafarm

12 Letter from I Wayan Mudana, Director of PT Aquafarm Nusantara, to Deltares dated July 28th, 2017.


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Nusantara voluntarily reduced production to about 30,000 tons because of water quality

concerns based on their own monitoring program and external concerns.

For the domestic company, PT Suri Tani Pemuka, a subsidiary of PT Japfa Comfeed Indonesia,

the main production license is issued under the guidance of the Ministry of Marine Affairs and

Fisheries, but is managed at the provincial level. The license was issued for the period 2012 to

2016 and allowed PT Suri Tani Pemuka to produce 30,000 tons per year. As its licence expired

in February 2016, PT Suri Tani Pemuka is currently applying for a new license (from the Ministry

of Spatial Planning) to comply with the Toba Spatial plan. In 2016 PT Suri Tani Pemuka

produced around 4,000 tons per year but it intends to increase production and grow to the

maximum of 30,000 tons as soon as all licenses have been obtained13.

Both commercial companies, PT Aquafarm Nusantara and PT Suri Tani Pemuka have

requested technical recommendations from BWS Sumatera II to support their licence proposal.

Till now, the requests have been rejected, so from the point of view of BWS Sumatera II, both

companies are currently operating without a permit. Table 3.1 summarizes the available

information on licenses.

Table 3.1, Aquaculture licenses for Lake Toba (in tons of fish per year).

Producer License

period

2012-2016

Sources Licence in

November

2017

Sources

PT Aquafarm Nusantara 36,00012 Letter from

Mr. Mudana,

201712

unknown

PT Suri Tani Pemuka 30,000 Toba

Tilapia,

2016

0 BWS

Sumatera II

Haranggoal Bay 0 Stakeholder

meetings

0 Stakeholder

meetings Other smallholders 0 0

3.4.4.2 Other license requirements

The development of a (major) building, such as a hotel, requires the provision of wastewater

facilities as part of the building permit. Sanitary facilities of buildings are the responsibilitiy of

the district agencies, guided by the Directorate General for Human Settlements of the Ministry

of Public Works and Housing. Recommendations need to be issued by the relevant district level

agencies before the permit to develop the building is issued by the head of the district. The

District Licensing Agency and the District Environmental Agency currently do not systematically

monitor the discharge of wastewater.

The issuance of permits related to hydropower generation is handled by three different bodies.

The Ministry of Public Works and Housing (PP 69/2014, as described above) provides permits

for water usage. The Ministry of Energy and Mineral Resources provides permits related to the

generation of electricity. The Ministry of State Enterprises provides permits for businesses

(Permen PUPR 4/2014). The operation of the turbines for hydropower generation highly relates

to the water level of Lake Toba, so hydropower management would have to adhere to

13 This amount has been used in Scenario B.



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procedures from both the Ministry of Energy and Mineral Resources and the Ministry of Public

Works and Housing.

For any changes in land use, such as the implementation of wastewater infrastructure,

permission is not easily obtained. Much of the land surrounding Toba belongs to local clans or

communities (masyarakat adat) and has cultural significance. Any changes and regulations in

the land need confirmation and approval from all families involved.

3.5 Legislation vs implementation

After the Water Resources Law No.7 Year 2004 was revoked through the Constitutional Court

(Order No. 85/PU-XI/2013), the Lake Toba Ecosystem Management Plan was not

implemented. Currently, the general policy and strategic plans are made by the central level

government, while the implementation of most practical measures is carried out at the district

(or kabupaten) level. This includes the issuing of permits for, for instance, drinking water, waste

water, aquaculture, and land use change.

The cooperation and acceptance of the recommendations by the districts is required for

successful implementation of proposed programs. Since 1998, most of the proposed programs

and interventions lacked this support. The lack of official establishment of procedures and lack

of local linkages, as well as no “active” agreement on the National level with the Ministry of

Home Affairs are the main “dysfunctional features” or “bottlenecks” for the implementation of

different well-formulated and urgently-required programs to safeguard and improve the

environment and water quality of Lake Toba.

Implementation of legislation is also dependent on monitoring and enforcement efforts on the ground. For instance, there is no enforcement or penalty for hotels and buildings that do not have permits or wastewater facilities. Licenses are issued by the District Licensing Agencies with recommendations by the relevant district line agencies. However, because of the lengthy process of the technical recommendations, absence of relevant district agencys and lack of coordination, many hotels and other investors abandon the process. Many hotels surrounding the lake do not apply for permits at all.

The planning and execution of erosion control and reforestation is the domain of the national

and sub-national government agencies of the Ministry of Forestry, implemented through a top-

down approach. Local communities, non-governmental organizations, and members of the

private sector have been involved in restoration and reforestation efforts, although their

work has been limited in terms of scale, funding, and geographic scope relative to the

government’s efforts. Unfortunately, from the government’s side, there are regulations and

actions that could undermine the erosion control and reforestation efforts. For example,

Presidential Regulation No. 49/2016, which was issued to accelerate Lake Toba as a tourism

destination, contains a section about re-zoning. This means that some areas surrounding the

lake, currently classified as “protected forest”, could be converted and used for other purposes

such as tourism in a fast-tracked process. Other threats to the forests near Lake Toba include

legal and illegal logging, as well as uncontrolled burning (see e.g. Hadinaryanto et al., 2014;

Gunawan, 2016; Sitanggang, 2017). If unchecked, illegal logging could greatly undermine the

efforts to restore forests in the Toba landscape.



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4 Stakeholders and Governance

4.1 Approach

The stakeholder mapping and assessment uses the stakeholder roles as recognized by the

Indonesian water laws (Annex H.1.1) and reflects the social network analysis conducted in

2017 (Annex H.1.2). It identifies for each actor involved in monitoring and managing the Lake

Toba Asahan catchment, his or her specific roles, interests and responsibilities. Based on the

result of the stakeholder mapping, different groups of stakeholders were categorised as “co-

knowers”, “co-thinkers”, or “co-operators”.

The stakeholder assessment and mapping was based on the (2013-2015) Basin Water

Resources Management Council (Tim Koordinasi Pengelolaan Sumber Daya Air, TKPSDA)

process, in combination with recent (and on-going) processes. Stakeholders have been

identified in the Germadan Toba (Lake rescue initiative) process of the Ministry of Environment

and Forestry (Kementerian Lingkungan Hidup dan Kehutanan, KLHK), by the Environmental

Sustainability Authority for Lake Toba (Badan Koordinasi Pelestarian Ekosistem Danau Toba,

BKPEDT), by the Provincial Environment Agency (Dinas Lingkungan Hidup, DLH), and as part

of the Urban Sanitation Development Program (USDP). This assessment also builds on the

stakeholder mapping and assessment for the Basin Water Resources Management Plan

(2001-2004, Perencanaan Pengelolaan Sumber Daya Air Wilayah Sungai, BWRMP), which

was verified and updated. Insights from these earlier assessments were used to identify

stakeholders and structure the meetings.

Semi-structured interviews, meetings with the Reference Group, and the wider stakeholder

consultations as part of the WQ Roadmap assignment provided further insights into the views

of key stakeholders (Annex A). Social network analysis was performed as part of these

meetings, resulting in new NetMaps. The NetMap exercises and resulting maps (Figure 4.1

and Figure 4.2) helped identify additional stakeholders and showed which stakeholders play a

key role in water quality monitoring and management at Lake Toba.

4.2 Stakeholder mapping

4.2.1 Mapping

Two meetings were organised to map the stakeholders involved in water quality at Lake Toba

through NetMap analysis (Annex H.2.1): the first in Jakarta, and the second in Laguboti

(Sumatra), with a larger group. The involvement of the reference group in both meetings provided

an opportunity for reflecting on elements of the management of Toba Lake water quality, and

in understanding the dynamics in the management of water quality in Lake Toba without

conducting elaborate questionnaires. The discussion focussed on the key question: “Who

Influences the water quality management of Lake Toba?”

The meetings started with the identification of stakeholders (actors and actor groups), without

referring to ealier mapping processes. This allowed for a strong focus on water quality.

Subsequently, two important flow types between them were defined in relation to Lake Toba

water quality: authority and information (or coordination). In Figure 4.1 and Figure 4.2 these are


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represented in blue arrows for authority and in yellow arrows for information or coordination.

Solid lines represent formal flows and dotted lines point at informal flows. The size of the circle

for each actor illustrates relative influence: the larger the size of the circle, the higher the

influence of this stakeholder on the management of water quality.

Figure 4.1, Social Network Map from the first NetMap exercise on the influence on water quality management in

Lake Toba, as produced with the reference group on May 17, 2017.

The first meeting, held in Jakarta with 27 participants, produced a social network map (Figure

4.1) with a total of 248 connections. Assuming that coordination is a two-way relationship and

authority is a one-way interaction, the total number of linkages would be 496 (the “arrow heads”

in the figure). The map indicates the presence of several hubs that are highly connected and

have significant influence over the network. These hubs include the Basin Management Center

Sumatra II (or BWS Sumatera II), the Coordinating Ministry of Maritime Affairs (or Kemenko

Maritim), the Governor of North Sumatra (or Gubernur SU), the Ministry of Public Works and

Housing – Directorate General Water Resources (PUPR SDA), and the Ministry of Environment

and Forestry (KLHK). These key stakeholders are described in the next section 4.2.2.



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Figure 4.2, Social Network Map from the second NetMap exercise, building on the first NetMap exercise,

produced with more participants at the local level on June 14, 2017.

The 55 participants at the second meeting, held in Laguboti (Sumatra), identified more

local actors, for example traditional leaders. These additional stakeholders and

connections enriched the discussion on the management of Lake Toba. Hence the second

network map (Figure 4.2) shows more stakeholders in the map, with more connections,

especially at the sub-national level. At the second meeting, 389 connections have been

identified. With that coordination displayed as a two-way relationship and authority as a

one-way interaction, the total number of linkages would be 778. Interestingly, the hubs

stayed relatively unchanged even after more stakeholders were added to the map. With

more sub-national actors added to the map, a few new linkages were identified between

the sub-national actors. For example, Bappeda Kabupaten (District Planning Agency)

emerged as a hub for the district agencies. Annex H.3 includes some of the rich

discussions around the maps. Main findings are included in sections 4.2.2 and 4.3, while

the overall analysis of stakeholders and institutions is the scope of section 4.4.


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The NetMap process shows how the various government agencies are not as connected

with other actors (private sector, academia, and local communities), as it should be for

good communication and coordination.

The network map process helped prioritize actions by identifying the actors with the

perceived highest negative influences to the Lake (highest polluters). State actors are not

the only actors actively involved as for instance civil society organizations (CSOs) play a

significant role in shaping the water quality agenda. The net map shows that CSOs are

highly connected with each other and with other types of actors at different levels (national

and subnational). The local CSOs have attempted to influence water quality management

through a range of activities from public education, advocacy, environmental protection

and conservation, to information exchange. Many of the CSOs, such as Yayasan Pencinta

Danau Toba (YPDT), WALHI, Alusi Tao Toba, KSPPM, and local communities,

represented through DAERMA (Local Fishermen’s Association), expressed that often

when their aspirations are not well-received by the district services, they would go directly

to the relevant ministries at the national level.

Targeting actors with the highest negative influence could support lake management

intervention and enhance potential impact.

4.2.2 Key stakeholders

A total of 91 stakeholders were identified during the NetMap exercises. This number is an

under-representation of the actual number of stakeholders involved. For instance, certain

district level agencies were listed only once to represent all eight districts surrounding Lake

Toba. If all district level agencies were to be included, the number of actors would be 170.

An overview has been made of all stakeholders at Lake Toba with their key role as

regulator, coordinator, operator, developer or user (see Annex H.1.1 for an explanation of

these roles), the level at which they operate, type of organization and the sector. The full

list of stakeholders is presented in Annex I. Below the most important stakeholders are

briefly introduced with their mandate and main activities.

Table 4.1, Main stakeholders at the central government level with their mandate and activities in relation to

water quality of Lake Toba.

Institution Activities Involvement

Coordinating

Ministry of Maritime

Affairs

Coordinates Ministries of:

Transportation; Marine and Fisheries; Tourism;

and Energy and Mineral Resources

The Board chair of

BOPDT is from this

ministry; the head of

implementation is from

the Ministry of Tourism

(perspires 49/2016,

clause 5)



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Coordinating

Ministry of

Economic Affairs

Coordinates Ministries of:

Public Works and Housing; Forestry and

Environment; Finance; Industry; Trading;

Labour; Agriculture; Agraria and Spatial

Planning; State Owned Companies;

Cooperative and small enterprise.

Through several of the

ministries it coordinates.

Ministry of

PPN/National

Planning

Agency/Bappenas

(Sub Directorate

General of River,

Coastal, Reservoir,

Lake)

Coordination and policy formulation on

development planning, national development

strategy, sectoral, cross-sectoral, and trans-

regional policy directions, national and regional

macroeconomic frameworks, infrastructure and

infrastructure design, regulatory, institutional

and funding frameworks, and monitoring,

evaluation and control of the implementation of

national development.

National planning

agency, especially for

national priority

programs (e.g. tourism);

Planning of rivers,

reservoirs and lakes

influences Lake Toba.

Ministry of Tourism

Formulation and determination of policy on

tourism destination and tourism development,

development of foreign tourism marketing,

development of tourism marketing of

archipelago, and development of tourism

institute.

Tourism industry is a

polluter (via solid waste

and wastewater) and an

employer and potential

ally for improved water

quality; Lake Toba is a

priority tourism

destination.

Ministry of

Environment and

Forestry

Formulation and policy making on sustainable

forest and environment conservation,

conservation of natural resources and their

ecosystems, improvement of watershed

support capacity and forest protection,

sustainable forest management, enhancement

of forest industry competitiveness, quality of

environmental functions, control of pollution &

environmental degradation, climate change

adaptation and control of negative impacts,

forest & land fire control, social forestry and

environmental partnerships.

A substantial area

around Lake Toba is

classified as forest

estate, which is under

the purview of this

Ministry. Environmental

issues touch upon many

other sectors, hence the

broad involvement of this

Ministry.

Ministry of Agraria

and Spatial Planning

Formulation, determination, and

implementation of policy in spatial planning,

infrastructure of agriculture, land affairs, land

use, and soil.

Pres. Reg. 81/2014

(spatial plan of lake

Toba/NSR) has to be

monitored by this

Ministry

Ministry of Public

Works and Housing

(MPWH)

Formulation of water resources under DGWR,

wastewater management, sanitation, and

waste management under DG Human

Settlements, and management of lakes in the

Center of Lakes and Reservoirs, roads under

DG Bina Marga (PIPR)..

Management of water

resources, wastewater,

and sanitation; integrated

tourism master plans.


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Regional

Infrastrucutre

Development

Agency (RIDA),

MPWH

Preparation of technical policy and integrated

strategy of regional development (under

Ministry of Public Works and Housing).

Preparation of integrated

tourism master plan for

several tourism

destinations (including

Lake Toba)

BWS Sumatera II

Water resources planning and management of

upstream conservation, water quality, water

utilization, control of destructive water,

operation and maintenance, rehabilitation,

construction/development.

Water quality monitoring

Center Research of

Water Resources Research

Water quantity and

quality

Ministry of Marine

Affairs and Fisheries


implementation of policies on marine, and

freshwater fisheries and aquaculture

Aquaculture is a polluter

and employer.

Ministry of

Agriculture

Formulation and issuance of policies on

provision of agricultural infrastructure and

facilities, increasing production of meat, rice,

corn, soybeans, sugarcane, and other crops,

as well as enhancement of added value,

competitiveness, quality, and marketing.

Agriculture is an

employer and a polluter

(especially livestock)

Ministry of Industry


implementation of policies for industry;

technical guidance and supervision over

implementation of policies for industry.

Local industries (e.g.

TPL) are polluters and

employers.

Ministry of State

Owned Companies

Implement water resource commercialization,

Water resource services in water resource

utilization by users; provision of guarantee for

water resource services to users through

operation, maintenance and development of

water resource infrastructure; provision of

technical advice to water resource managers

authorized to prepare technical

recommendations for water resource

commercialization; implementation of operation

and maintenance of water resource

infrastructure, for which operation is handed

over to the company.

State-owned companies

around Lake Toba, such

as PJT1. The Ministry

can collect fees from

water users.



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Badan Otorita

Pariwisata Danau

Toba (Lake Toba

Tourism Area

Management

Authority; 2016 -

2041)

Preparation of Master Plan and Detailed Plan

of Development of Tourism Area of Lake Toba;

implementation of coordination and policy

strengthening of planning, development,

management, and control of Lake Toba

tourism area; formulation of operational

strategy of tourism development of Lake Toba

area; assistance to development of tourism in

the area around Lake Toba, facilitation and

stimulation of tourism growth in the Lake Toba

area; implementation of licensing and non-

licensing business centers and areas in the

region of approximately 500 ha in the Tourism

Area of Lake Toba; determination of strategic

steps to solve problems in planning,

development, management, and control of

Lake Toba tourism area.

Preparation of detailed

plan,14 coordinating

implementation of master

plan, management of

500 ha tourism area

Supports momentum for

water quality

improvement

Investment

Coordinating Board

/BKPM

Coordination in national level for

investment/investor; national one-stop-shop for

investment (for large domestic investors or

foreign investors)

Licensing for investors

(e.g. in aquaculture),

including foreign

investors

Table 4.2, Main stakeholder at the provincial level with their activities in relation to water quality of Lake Toba.

Institution Activities

Provincial Environment

Department North

Sumatra (DLH-SU)15

Determination of carrying capacity and environmental capacity; Determination of environmental quality standards; Determination of the pollution quality standard for the main sources; monitoring and conservation of biodiversity; development and empowerment of communities in waste management; facilities and infrastructure for sewage treatment; water quality monitoring; monitoring of pollutant sources; pollution prevention (provision of information, isolation and termination) of pollutant sources; recovery of pollution (cleaning, remediation, rehabilitation and restoration) of pollutant sources; regulation of pollutant sources

Badan Pengelola

Geopark Kaldera Danau

Toba

Special body (initial) for Lake Toba Geopark, as required by UNESCO

BKPEDT Coordination for ecosystem, including water quality

Forum DAS (Daerah

Aliran Sungai) Coordination forum for upstream catchment

PU province Takes care of river basins that belong to the province (Permen PUPR

4/2015)

14 It has been agreed between government agencies/ministries that RIDA of MPWH will prepare the Integrated

Tourism Master Plans. 15 Before January 2017, DLH-SU was named BLH-SU, Badan Lingkungan Hidup - Sumatra Utara: the Provincial

Environment Agency - North Sumatra.


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Table 4.3, Main stakeholders at district level with their activities in relation to water quality of Lake Toba16.

Institution Activities

Head of District

Licensing authority for fish cages and hotels, based on

technical recommendation from related agencies

Regional Planning Agency/

Bappeda Kab.

Coordinates planning from all sectors at district level

District PU Takes care of river basins that belong to the district

Table 4.4, Other major stakeholders with their activities in relation to water quality of Lake Toba.


Various NGOs Depending on their interest Some do monitoring

PDAM Tirtanadi Drinking water and wastewater

company

Manages wastewater

treatment plant (IPAL) Parapat

Electricity companies

(e.g. BDSN, INALUM,

PLN)

Hydropower Water user

TPL (Toba Pulp

Lestari) Pulp company Polluter and employer

PT Aquafarm

Nusantara Aquaculture Polluter and employer

PT Suri Tani Pemuka Aquaculture Polluter and employer

National Water

Resources Council/

Dewan Sumber Daya

Air Nasional

Preparation of national water resources

policy

Water quality is one aspect in

policies

Basin Council/

Tim Koordinasi

Pengelolaan Sumber

Daya Air Wilayah

Sungai

Coordinates water resources

management at basin level; endorse

strategic and master planning, global

and yearly water allocation,

implementation matrix on hydrology,

hydrogeology and hydro-climatology,

monitoring program and activities

Water quality is one aspect of

water resources conservation

4.3 Stakeholder assessment

The discussion and resulting NetMaps illustrate that management of water quality in Lake

Toba is complex and dynamic. The actors with many hubs (highly connected network) are

mostly at the central level. The second map (Figure 4.2) shows that there are few

connections at the sub-national levels (both at provincial and district levels, but especially

at the district level), to the rest of the actors on the map. These few connections are mainly

limited to other governmental entities, and rarely with the private sector, academia, or

16 In 2016 there were no agencies at district level for forestry, environment and aquaculture.



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others. There seems to be little collaboration between government agencies in different

sectors, nor between various levels. This confirms perceptions reflected in the first NetMap

(Figure 4.1), suggesting that the central level actors are more vocal and more involved in

the management of Lake Toba.

The NetMap itself did not capture actors that may influence water quality in Lake Toba but

have very limited interest in improving lake water quality or reducing pollution. The

discussion helped to identify them (for instance in aquaculture, livestock, tourism, mining).

There are several coordinating bodies (e.g. Forum DAS, TKPSDA, and BKEPDT) to

manage the water quality of Lake Toba but the NetMaps do not show a clear leader or

champion. This may be because these organizations have been initiated at national or

provincial level, with little focus on the district level. The hubs with intensive interaction

indicate the potential of some stakeholders to become champions or change agents

toward the better management of Lake Toba water quality.

It might be worth exploring the CSOs’ potential to guard the management process of Lake

Toba, considering their active participation and monitoring on the issue, and their close

relationships (formal and informal) with different kinds of stakeholders. From the

discussion at the second workshop, the CSOs emerged as having been engaged with

each other as well as with the local communities. They have been pressuring many

changes in the government and private sector as well.

4.4 Governance for monitoring and management of Lake Toba

4.4.1 Approach

The NetMaps (section 4.2.1) show relationships between actors. However, the strengths

and gaps in their governance are not apparent on the map, especially regarding the

capacity to monitor the implementation of programs, including the issuance of permits and

law enforcement. Thus, a separate analysis identifying strengths, weaknesses,

opportunities and threats (SWOT) has been conducted at the meetings for various sectors.

SWOT analyses help to identify internal strengths and weaknesses, as well as its external

opportunities and threats of an organization, initiative or sector. In this case, benefitting

from the expertise of the Reference Group present at the meetings, the analysis focused

on aspects that have an impact on the water quality of Lake Toba.

After separate SWOT analyses had been done for different stakeholders and processes

associated with water quality monitoring and management at Lake Toba, an overall

analysis could be made.

4.4.2 Overall SWOT

The following areas have been considered in identifying strengths, weaknesses,

opportunities and threats for the WQ Roadmap (Figure 4.3):

• Resources available: Labour, capital, management skills, technology, funds


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• Physical environment: Climate, severe weather events, volcano eruption, pests and

diseases

• Infrastructure factors: Roads, transport, Integrated Water Resources Management

(IWRM) infrastructure

• Economic factors: Livelihood issues, markets, tourism

• Social factors: Residents attitudes towards use of the lake, sanitation and waste

management, legal and institutional aspects, and key stakeholders.

Figure 4.3, SWOT framework for Lake Toba water quality monitoring and management.

Main strengths are defined as current positive circumstances that support the monitoring

and management of water quality. The main weakness would then consist of the opposite,

a negative or unfavourable condition that hampers the success of monitoring and

management of Lake Toba. Opportunities consist of innovative ways to make the

monitoring and management more successful, to create an environment that is more

favourable. Finally, threats are defined here as events or conditions that, if these would

happen, will harm the monitoring and management of Lake Toba. The factors shown in

Figure 4.4 have been identified as crucial strengths, weaknesses, opportunities and

threats to the implementation of a water quality roadmap for Lake Toba.



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Figure 4.4, Overall strength, weakness, opportunity and threat (SWOT) analysis of water quality monitoring and management of Lake Toba and its catchment area.

Strength

• The heightened momentum due to President Jokowi’s designation of Toba as one of the priority areas for tourism development.

• Wastewater treatment facilities and regulations were set up due to expected tourism activities (under decentralization law UU 23/2014, sanitation is a priority, triggered by the NSR).

• Strong demand and pressure for clean water in and around Toba, as reflected in infrastructure, initiatives, programs.

• Decentralization; provinces have more capacity and resources for operations and implementations.

• Provincial agency now handles management of solid waste.

• Reference and guidance for Lake Toba management is available from Lake Rescue Initiative and other studies. The letter from the Minister of Environment and Forestry (MENLHK/PPKL/PKL.2/4/2017) provides direction.

• Increasing public participation, with communities interested to comply and NGOs actively participating and involved in monitoring.

Weakness

• Not all eight districts have formally committed.

• Gaps between initiatives at the central level and implementing bodies at the district level.

• Limited monitoring and enforcement capacity in law compliance.

• Poor state of existing wastewater treatment plants.

• Low coordination between the license issuing agencies and the relevant technical services at the district level.

• Lack of legally binding regulations for the Lake Rescue Initiative to implement a management program.

• Diffuse responsibilities because of overlapping mandates between institutions.

Opportunity

• National programs as incentives for better management: Adipura, Social Forestry Program.

• High interest from the President to preserve Lake Toba, could be used to get other government bodies actively involved.

• Lake Toba as a priority National Strategic Region receives a lot of attention.

• Interest from the Coordinating Minister of Maritime Affairs could further push development of infrastructure around Lake Toba.

• Lake Toba Tourism Area Management Authority Board has a specific mandate

• The Government is in the middle of preparing an integrated tourism master plan.

• The presence of local community support groups (KSMs) could be used for information sharing, to advocate better management and to promote new intervention programs.

• Willingness of community members to change jobs, especially to tourism.

Threat

• Much of the land surrounding Lake Toba has cultural significance. Any changes in land use need customary approval from all families and clans. This long process could hamper the timely implementation of basic infrastructure.

• Lake Toba Tourism Area Management Authority Board is allowed conversion of areas around the lake, including those currently classified as “protected forest”, into other uses in a fast-tracked process.

• If fish production would be limited, jobs could be lost, possibly without alternative livelihoods, potentially leading to social conflicts or legal disputes.

• Political changes at national and provincial level could affect the strong commitment to restore the lake.

• Potential conflict of interests when government officials are involved in industry, such as fishing industry, or paper mills.

Monitoring and Management of

Lake Toba


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4.4.3 Synthesis

Overall, the heightened momentum to make Lake Toba a tourism destination has provided a

strong push for new initiatives and program to revive Lake Toba. The agenda for management

of Lake Toba is pushed at the national level, through the President, the Coordinating Ministry

of Maritime Affairs, the Lake Toba Tourism Area Management Authority, and the Ministry of

Environment and Forestry through the Lake Rescue Initiative. This agenda provides a window

of opportunity to accelerate the improvement of Lake Toba’s water quality. The heightened

interest allows more resources, be it human resources or financial resources, allocated to

support pollutant intervention in Lake Toba.

Regardless of this strong push, the bottleneck in the management has been at the district level,

where monitoring and law enforcement efforts happen. Currently, the district heads have not

shown strong commitment to manage the lake or may lack the capacity (where no fishery

agencies are present at district level, technical recommendations for licenses cannot be given).

As observed on the ground, there is weak maintenance of existing facilities, such as the waste

disposal sites or wastewater treatment plants. There is a lack of coordination between the

district that issues licenses and relevant district services. This is a major unfavourable condition

that will hamper the management efforts of the Lake Toba area.

To respond to this drawback, hence, a legal regulation to bind commitments on the district level

is urgently needed. The Governor could use his legal intervention power to instruct and guide

the Districts. In the past, the Ministry of Home Affairs has proven itself to be an effective body

to instruct district heads to build sanitation facilities. Direct implementation by provincial

agencies to take over management role is seen as positive, since provinces have more capacity

and resources (human resources and budget) for operations and implementations than the

districts. It is crucial for the provinces to do monitoring efforts and enforce the already existing

laws to ensure that all stakeholders abide by the regulations. It is also important for the governor

to actively voice a strong commitment to Lake Toba area management.

Local residents, including civil society groups (CSOs), have expressed support and are eager

to follow management programs and obey the laws. This includes farmers who have shifted

from horticulture to aquaculture. Though they are operating without a license, they have

expressed a keen interest in alternative livelihood options. There are active CSOs engaging

with residents and voicing concerns on the resident’s livelihoods. Residents have a strong

attachment to Lake Toba for its cultural value.



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5 Drivers and Pressures: nutrient inputs

5.1 Approach: the Sumatra Spatial Model

The Lake Toba catchment area was analysed with an adapted version of the Sumatra Spatial

Model (Annex J). The same spatial model has been applied in Indonesia to predict impacts on

water resources systems in earlier studies, such as the Java Spatial Model developed for the

ADB study for the 6 rivers around Jakarta (6Ci study); the World Bank-financed Java Strategic

Water Resources Study (JWRSS); and the Korean study for Strategic Water Resources of

Sulawesi.

5.1.1 Calibration of population growth

For the year 2015 a comparison was made of the population data according to the Dalam

Angka statistics by district found in the Lake Toba catchment area (Table 5.1). It is found that

the population growth 2010-2015 in this period is over-estimated by the Sumatra Spatial Model

as growth for Sumatra as a whole is set at about 3% annually. However, average growth for

the Lake Toba districts (Figure 7.1) is only about 1% annually according to the Dalam Angka

and about 2% in the Sumatra Spatial Model. In the drivers of SSM the growth reduces rapidly

after 2015. Therefore, it is expected that this difference in growth is only in the beginning of the

projection period.

Table 5.1, Comparison of 2015 Dalam Angka population with results from the Sumatra Spatial Model (SSM).

2015 population SSM/Dalam

Angka District Dalam Angka SSM

Tapanuli Utara 293,399 301,609 102.8%

Toba Samosir 179,704 189,917 105.7%

Asahan 706,283 739,829 104.7%

Sima Lungun 849,405 899,582 105.9%

Dairi 279,090 296,631 106.3%

Karo 389,591 391,915 100.6%

Humbang Hasundutan 182,991 185,717 101.5%

Samosir 123,789 132,155 106.8%

A proper comparison can only be made in the next population census. As the model

overestimates the waste load calculated by SSM, it is on the safe side for the water quality

analysis. Therefore, at this stage no further attempt to calibrate the spatial model for the Lake

Toba region was made. This can be considered at a later stage when making a more detailed

study of the Lake Toba water quality at present and in the future.

5.1.2 Load calculations

To quantify the importance of the current sources of nitrogen and phsphorous, load calculations

were performed on the basis of this model. These calculations and the SSM model also project

socio-economic developments, future land use and the corresponding nutrient and waste loads.

The assessment of key drivers is based on emission estimations for point and non-point

sources in the year 2015, across the selected zonation option to divide the lake into four


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compartments. After the loads have been calculated, total nitrogen (TN) and total phosphorous

(TP) concentrations are calculated for each of the compartments witha simple budget model

approach (Annex J). Below the model settings and assumptions are provided with respect to

emission and run-off factors per source.

Aquaculture

Emissions for the whole lake are calculated as the product of annual fish production (tons of

fish/year) and the nitrogen or phosphorous loss to the environment per ton of fish production.

The phosphorous loss is estimated as 15.98 kg per ton of fish, by applying a food conversion

ratio of 1.9 to the values estimated by Oakley (2015, Table 1). The nitrogen loss is taken as 6

times the phosphorous loss (based on Table 4 in Gyllenhammar and Hakanson, 200): 74.78

kg/ton fish. The total load is distributed over the various lake model compartments based on

the ratio of their surface.

For 2015 the total production based on DLH-SU 2017 was taken: 84,800 tons. However, the

distribution over the various producers, as suggested by DLH-SU in Table 2.3), could not be

justified based on observation. A GIS analysis (the data behind Figure 5.1) determined the

number of fish cages across Lake Toba. As the fish cages of smallholders outside Haranggoal

Bay varied over time (section 2.1.4), a weighing factor of 0.5 has been applied to estimate the

number of cages in 2015. Subsequently, the total production of 84,800 tons has been

proportionally distributed over the fish cages, assuming that commercial fish cages produce

twice the amount of smallholder cages. Emissions however, are set at the same value for

commercial and smallholder fish cages as commercial aquaculture operate more efficiently

(Table 5.2).

Table 5.2, Estimated fish production in aquaculture at Lake Toba in 2015 across the compartments per group of

producers (in tons of fish per year, with total production estimates by DLH-SU and geographical distribution

according to Figure 5.1).

Producers Estimated production 2015

N South S1 S2 S3 Total

PT Aquafarm

Nusantara

14,000 22,000 22,000 36,000

PT Suri Tani

Pemuka

9,700 0 9,700

Haranggoal Bay 22,700 0 22,700

Other smallholders 6,500 9,900 3,300 4,900 1,700 16,400

Total 52,900 31,900 3,300 26,900 1,700 84,800

Percentage

production

62% 38% 4% 32% 2%

Percentage

emission

60% 40% 8% 28% 4%

Livestock

Livestock counts are related to population numbers. The population forecasts per sub-

catchment provide growth factors to estimate the future load from livestock. The emission factor

for phosphorous is 384 ton P/year, based on DLH-SU (2017). The nitrogen load is taken as

three times the phosphorous load (i.e. 1,152 ton N/year) based on Buckley and Makortoff

(2004).



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Agriculture

Emissions are calculated as the product of cultivated areas, emission factors per crop or culture

type (g/ha/season) and the number of growing seasons per year (Table 5.3). The emission

factor for P was based on Iskandar (2013).

Table 5.3, Model settings for agriculture.

Emissions (g/ha/season) Number of

seasons

Runoff

factor N P

Total paddy area (ha) 20 10 3 1

Other agriculture (ha) 10 5 1 1

Plantation (ha) 3 1,5 1 1

Wastewater

Emissions are calculated as the product of population, emission factors per inhabitant

(g/person/day) and the runoff factor (Table 5.4). Emission factors were taken from DLH-SU

(2017) and Deltares & TNO (2016). The population numbers are based on national censuses

and the Sumatra Spatial Model and thus comprise only inhabitants of Lake Toba’s catchment

area (see Annex J).

Table 5.4, Model settings for domestic wastewater.

Emissions (g/person/day) Number of days

per year

Runoff

factor N P

Urban population 15 2,55 365 0,5

Rural population 15 2,55 365 0,5

The tourism load is estimated from a total of 5 million tourist night per year based on the Tourist

Demand study (Table 7.1). The resulting load is computed in a similar way as the domestic

loads (Table 5.4). The total tourist night are spread between the model compartments based

on the Tourist Demand Assessment (Nontji, 2016). Other land Use

For other land use, emissions are calculated as the product of land use areas and emissions

factors per land use class (Table 5.5). Phosphorous and nitrogen emission factors were based

on Iskandar (2013).

Table 5.5, Model settings for other land use.

Emissions (g/ha/year)

N P

Grass/Other (ha) 2,46 0,246

Shrub (ha) 2,46 0,246

Forest (ha) 1,94 0,194

5.2 Assessment of point and non-point sources

It is important to distinguish the potential sources to identify appropriate mitigation measures to reduce pollution loadings into the lake. From this perspective sources can be classified as point and non-point sources to guide infrastructure and other investments for potential mitigating measures. A classification for the most important drivers of pollution; aquaculture, livestock and domestic wastewater, is provided below with illustrative maps. However, for the water quality


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model a distinction between point and non-point sources is less important as it is assumed that each nutrient loading is immediately dispersed in a compartment up to the thermocline layer. Aquaculture

Theoretically, each fish cage could be considered as a separate point source. Mitigating

measures can be taken at farm level and from there at each individual cage.

Figure 5.1Figure 2.1 can serve as guidance to support targeted mitigating measures. In Figure 5.1 the dots represent clusters of individual fish cages as mapped from Google Earth images.



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Figure 5.1, Location of three types of aquaculture on Lake Toba, based on observations in Google Earth in the

period 2008-2015. Blue: clusters of long fish cages, as mainly found in Harangoal Bay; Green: clusters of

commercial fish cages; and Yellow: clusters and individual fish cages.

Livestock Numbers of farming animals in the models have been estimated from population growth in the Sumatra Spatial Model. Figure 5.2 shows livestock densities around Lake Toba, based on data from DLH-SU. Nutrient loads from manure mainly enter the lake via surface runoff and groundwater. Livestock can be classified as non-point source of pollution that roughly follow population densities. The same holds true for agriculture and other land use (minor contributions to nutrient loads only). The division into compartments extends to the catchment areas.


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Figure 5.2, Livestock densities around Lake Toba. Note that some data were available at desa level, some at district

level, and for other areas no data were available at all.

Wastewater

Most of the current sanitation facilities around Lake Toba are on-site facilities at household or

community level. Both in rural and urban areas most of the on-site systems do not comply with

the definition of a septic tank and are more like pit latrines. The one wastewater treatment plant

in the area is operating at only 10% of its capacity (section 8.4.2.1). As a result, a lot of polluted

water leaks to the groundwater. At times of high precipitation this is complemented by surface

runoff. Hence domestic wastewater can be classified as a non-point source ofpollution in the

catchment area, with concentrations following population density (Figure 5.3).



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Figure 5.3, Lake Toba catchment population density by desa in 2015.

Tourism numbers do not substantially increase the nutrient load from domestic wastewater, as

the numbers of visitors are low in comparison to the population density, though they are

concentrated in a limited number of desas (Figure 5.4). Hotels are generally small and even

without adequate sanitation facilities, the contribution of individual hotels can be compared with

a cluster of houses. Therefore, tourism can be classified as a non-point source.


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Figure 5.4, Main tourism areas around Lake Toba (based on Tourism Demand Assessment).

5.3 Total and relative nutrient loads

The modelled nitrogen (N) and phosphorous (P) loads for the year 2015 are shown in Figure

5.5, Figure 5.6 and Figure 5.7, with indications of the relative contributions of various sources

across the compartments. These figures clearly show that aquaculture is the main source of

nutrient loading, constituting 76% of the total N loads and 68% of the total P loads into the

whole lake. This is followed by domestic wastewater (sewage), responsible for 15% of the

nitrogen loads, and 11% of the phosphorous loads. The third main source is livestock, which

contributes 5% to the nitrogen loads and 19% to the phosphorous loads. Other sources of

nutrients include forests, meadows, tourism, sawahs and other agriculture, together

responsible for 4% of the nitrogen loads and 2% of the phosphorous loads (Figure 5.8).



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Nitrogen (N) loads in one compartment

Nitrogen (N) loads in two compartments

Nitrogen (N) loads in four compartments: N = north; S1, S2 and S3 are southern compartments

Figure 5.5, Relative contributions of various drivers to the total nitrogen (TN) load in various lake compartments in

2015, according to the load calculations based on land use and underlying SSM model.


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Phosphorous (P)

loads in one

compartment

Phosphorous (P)

loads in two

compartments

(N = north)

Figure 5.6, Relative contributions of various drivers to the total phosphorous (TP) load in one and two lake

compartments in 2015.



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Figure 5.7, Relative contributions of various drivers to the total phosphorous (TP) load in 2015, in four lake

compartments: N = north; S1, S2 and S3 are southern compartments.

Figure 5.8, Relative contributions of various sources to the total phosphorous load in Lake Toba as a whole in 2015.


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Tourism thus has relatively limited, if any, impact on nutrient loading – as evidenced from Figure

5.9.

Figure 5.9, Relative contributions of wastewater from residents (domestic loads) and tourists (tourist loads) for

nitrogen (top graph) and phosphorous (bottom graph) in four compartments of Lake Toba: N = north; S1, S2

and S3 are southern compartments.

The nutrient loads presented above are based on mixing in the lake compartments. In reality

there may be significant local effects that are not captured in the approach applied here. Hence

even in cases where the long term, far-field effects that are shown in this chapter are not very

large, the short term and local (near-field) effects may still be significant. LIPI calculated the

near field effects and these show that with increasing densities of fish cages, the water quality

may locally deteriorate to eutrophic and even hyper-eutrophic state, for instance along the

north-eastern coast (Table 5.6). This demonstrates that the findings in this report, showing

average values for entire compartments, could represent an under-estimation of the true local

pollution loads. On the other hand, local effects could also be very temporary, as influenced by

changes in local loads, winds and other factors.



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Table 5.6, 3D model results on the short term & near-field effects of nutrient loads resulting from aquaculture at various depths in Lake Toba (Figure provided as is by LIPI).

Density of

fish cages

Depth

1m 2m 10-15m 40-50m

0 cages/

segment

20 cages/

segment

100

cages/

segment

Each segment (pixel) is 250 x 250m


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5.4 Nutrient inputs

As part of the decision on the carrying capacity of Lake Toba, several key institutes and

universities have carried out a “pollutant source analysis” to understand the pollutant load

pathways in Lake Toba. Although the analyses differ somewhat, they all show the same picture,

which has been summarized by DLH-SU in their carrying capacity as proposed to the Minister

(DLH-SU, 2017; Figure 5.10): Phosphorus is identified as the most critical factor for water

quality. Other parameters are important as well, but for this Water Quality Roadmap the focus

is on the process of eutrophication with phosphorous as the main determinant. Findings on

nitrogen have been added to most sections as well.

Figure 5.10, Phosphorous loads to Lake Toba as reported by DLH-SU in ton/year (source: DLH-SU, 2017)

By far the largest nutrient loads originate from aquaculture, followed by animal husbandry and

domestic sewage (including tourism), agriculture and some very small other sources of

pollution. This is in agreement with the loadings calculated on the basis of the SSM model

reported in the previous section. Figure 5.10 also shows that the rate of daily phosphorous

contribution from aquaculture has doubled over the past four years. The pollution load from

livestock has increased by about 25%, while the domestic pollution load has minimal changes.

Nutrient inflows from agriculture, forest areas or as a result of erosion are relatively unimportant

for the process of eutrophication and have not been elaborated in detail. Nevertheless,

interventions in these sectors may contribute to the preservation of the Lake Toba area and

some suggestions about this are presented in section N.

In addition to phosphorous and nitrogen, other parameters are important for eutrophication,

such as biochemical oxygen demand (BOD). Subsequent more detailed studies on water

quality in Lake Toba would need to consider this as well. Apart from eutrophication, other

parameters may have locally important impacts on water quality and even human health, such

as inorganic compounds, pesticides and pathogens. These are among the variables suggested

for intensive monitoring in section 9.3.



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6 State and Impact: Lake Assessment

6.1 Approach

The method applied is a water quality system analysis which encompasses the understanding

of the water quality issues and the underlying causes or drivers. Key components of the water

quality system analysis are:

• Existing knowledge of the hydrology of the Lake Toba Asahan basin as modelled in the Basin Water Resources Management Planning (BWRMP) project (Vernimmen, 2015);

• Existing water quality data of Lake Toba (in collaboration with LIPI, DLH-SU and PTAN); and

• Point and non-point sources of pollution and their emissions, such as domestic emissions, deforestation, industrial development, poor sanitation and unregulated aquaculture;

• Calculations of the pollution loads into Lake Toba;

• Review and assessment of the resulting nutrient concentrations in Lake Toba and identify assumptions and uncertainties therein; and

• Evaluation of development scenarios in relation to the equilibrium pollutant concentration.

The most important aspect of lake water quality is the amount of biological nutrients that are

dissolved in the lake, the so-called eutrophic state. In contrast to other pollutants, continuous

pollution with nutrients (‘eutrophication’ by phosphorous and nitrogen) has the potential to

irreversibly upset the lake chemistry and biology on a system level. Whereas other types of

pollution such as pesticides and pathogens (such as E.coli) will degrade or dilute quickly upon

emission and do not amplify processes that can cause irreversible functional degradation on a

system level. Therefore, this assessment focuses on eutrophication related pollution, more

specifically phosphorous (P) and nitrogen (N) loads. Nutrient concentrations may vary dependent on the specific P-loads or N-loads from the upstream part of the river basin and the predominant circulation patterns. In close communication with LIPI, the assessment was thus carried out for various (sub) compartments (section 2.2.6):

• Whole lake (1 compartment)

• North and south lakes (2 compartments),

• North and 3 south lakes (4 compartments), and

• Other simulations to illustrate the implications of zonation.

Based on this zonation into compartments the changes in estimated concentrations were

compared and evaluated between the whole lake approach and a compartmental approach.

6.2 Available data

6.2.1 Main data sets

Many stakeholders possess or collect data relevant for the study, such as catchment-wide GIS

data on land use, population statistics, agricultural statistics or lake monitoring data such as

nutrient concentrations, water transparency and chlorophyll concentrations. In total 16

stakeholders have been identified, who could contribute data (Annex K.1). All stakeholders had


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different forms of access to, and needs for, these data, and therefore apply different monitoring

approaches. The types of data vary widely, from spatial (GIS) data to single water quality

parameters and can be divided into three functional categories: (1) signal function; (2)

exploratory data; (3) statistically conclusive.

Three data sources provided data for the water quality assessment: the Provincial Environment

Agency (DLH-SU), the Indonesian Institute of Science (LIPI), and PT Aquafarm Nusantara

(PTAN). An outline of these three datasets is provided in section 3.3. The initial purpose of the

datasets differs and so does the monitoring design. DLH-SU aims at the determination of lake

status (level 1, signal function). LIPI seeks to understand the system, aiming for levels 2

(exploratory) to 3 (scientific). PTAN needs the data for ASC certification, for which it needs to

understand the effect of aquaculture on the environment in which it is situated (system

knowledge). This means at least level 2, but only for a part of the lake system. The available

data sets have been compared to standard monitoring guidelines in Annex K.2.

Remote sensing was also used to illustrate the application of methods for measuring water

quality. Conventional in situ water quality sampling limited to a local scale can be costly and

labor intensive, whereas remote sensing can increase data availability by providing two-

dimensional maps derived through various inversion methods that would otherwise require a

large number of in situ water quality monitoring stations. Typically the application of proposed

remote sensing methods are supporting quantitative assessments of location, timing and

phasing of treatment infrastructure, a rationale for establishing priorities for water pollution

control interventions to improve environmental quality, and ultimately the development of

integrated pollution management and monitoring solutions that are financially, socially,

economically and environmentally sustainable, as well as the definition of a process for

prioritizing investment opportunities and trade-offs of the different options considered. Specific

objectives associated with appplication of the remote sensing tools included:

• An assessment on the feasibility of integrated modeling-remote sensing methods

towards integrated approaches of water quality monitoring in surface water bodies.

• A description of next steps in capacity strengthening activities on the use of water

quality modeling and remote sensing tools towards integrated approaches of water

quality monitoring.

6.2.2 Quality of data

Each data set is specific in its spatial and temporal distribution (Annex J.3). Information about

quality control of the monitoring data was only available from the literature and personal

communication. This has revealed that both LIPI and DLH use government labs (Pusarpedal

KLHK) and perform regular quality tests of their equipment. PTAN uses on-site labs and these

are periodically quality-checked by Wageningen University and Research in the Netherlands.

While this is not an official certification, it is sufficient for PTAN to comply with ASC standards

(section 3.2.2).

The most important aspect in quality of water sample analysis is the consistency of the

laboratory chosen (section 9.1.6). This allows for comparison between samples over time.

However, when a switch is made to a different laboratory, monitored concentrations are known

to change so it is highly recommended to keep the same laboratory involved throughout the

monitoring efforts.



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6.3 Physical and chemical parameters

Below, an overview is presented of the present state of water quality variables, and how they have developed over the past 10 years. The assessment below is mainly based on the PTAN data since it constitutes the data set with the highest sampling frequency. Other data sources (BLU-SU and LIPI) are selectively included to complement these data and/or give an impression of the level of agreement between data sets.

Multispectral remote sensing using publicly available earth-observation satellite data was

analysed to provide unique insight into the complex water-quality dynamics of Lake Toba.

Multiple sensors are needed since temporal coverage is limited by atmospheric conditions and

overpass schedule (LS8 / S2A ‘land’ sensors: 5~10 days; S3A: ~1day but lower spatial

resolution), with additional sensors projected to be available in the near future. A summary of

the sensors used and their key characteristics is provided inTable 6.1, and illustrated inFigure

6.1. These were used to carry out the following: • Time-series estimates of turbidity, chlorophyll and vegetative cover were derived

from Sentinel-2A, Landsat-8, MERIS, MODIS, Landsat- 5/7 • Long-term changes in water quality (MERIS time-series ~2006) across the lake,

and specific changes in land-use in the Aek Manira watershed were observed. • Possible contributors to a significant water-quality event on January 9th, 2017 in

Bakara / Baktiraja region were discovered and described • possible approaches to overcome challenges related to data quality & quantity due

to atmospheric conditions were demonstrated: (i) marine layer-cloud-glint masks; (ii) combination of water quality products from multiple sensors

• ability to obtain multi-spectral imagery and water-quality dynamics on short time-scales (daily / intra-day) using geostationary platform (e.g. Himawari-8) was demonstrated

• remote-sensing data access, sources, processing algorithms and future work towards a comprehensive monitoring strategy were documented.

Table 6.1. High-resolution multi-spectral instruments supplemented with other atmospheric / land / OC missions

used in the Lake Toba study.


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Figure 6.1, Illustration of the combination of sensors and analysis used to gain an integral understanding of water

quality dynamics in Lake Toba and its basin.

6.3.1 Temperature

Water temperature is one of the variables that determine the depth of the thermocline that in turn sets the boundary of the mixing layers in the lake (section 6.6). The water temperature varies between 25 and 28 degrees Celsius (Figure 6.2 and Figure 6.3) and has been stable for the last 10 years. A minor increase is seen in the beginning of 2016, when surface water temperatures peaked at over 28 degrees Celsius. Each PTAN station showed a similar trend and values.



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Figure 6.2, Temperature (in degrees Celsius) measured at 2 m depth at the four PTAN locations. (Figure provided

by PTAN, 2017. See Figure 3.5 for legend and location of the sites.)

Figure 6.3, Temperatures measured in April and October along a depth profile of 100 meters, as measured at

stations 2, 5, 7, 11, and 12 (figure provided by LIPI).


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Figure 6.4, Oxygen dynamics along depth profiles (in m below the surface) sampled on a monthly basis from 2008

to 2016 at field station Pangambatan (NGB). (Figure provided by PTAN, 2017)

Figure 6.5, Temperature dynamics along depth profiles sampled on a monthly basis from 2008 to 2016 at field

station Pangambatan (NGB). (Figure provided by PTAN, 2017)

6.3.2 Dissolved Oxygen (DO)

Levels of dissolved oxygen (DO in mg/l) show different values and trends for stations near fish farms in comparison with the control (Figure 6.6). Measurements at fish farm locations have lower DO levels and fluctuate within and between years. Control measurements show a peak in 2006, 2007 and again in 2016, but otherwise values are stable. DO values steadily decline as depth increases and level out after 200 meters (Figure 6.7).



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Figure 6.6, Dissolved oxygen (mg/l) measured at 2 m depth at the four PTAN locations. Figure provided by PTAN,

2017. See Figure 3.5 for legend and location of the sites.

Figure 6.7, Dissolved oxygen profiles (in mg/l) measured at the four PTAN locations (Figure provided by PTAN,

2017).

The LIPI depth profile measurements show similar values to PTAN (Figure 6.8). An interesting anomaly is seen at station 11, in the middle of the southern part of the lake. At around 200 meters depth there is a sudden increase in oxygen value. This increase is not shown at any of the other points and could be caused by very local nearby thermal vents, or it could be the result of measurement errors.


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Figure 6.8, Dissolved oxygen (mg/l) along a depth profile of 400 meters, measured at stations 2, 5, 7, 11, and 12, in

April (left) and October (right) 2009 (Figure provided by LIPI).

6.3.3 Transparency (Secchi depth)

Data from all field stations show a similar trend reaching highest values between 2009 and 2010, with a sudden and drastic decrease in 2016 (see section 6.9.2). After 2016 transparency reaches its initial value of around 6m depth (Figure 6.9), corresponding to an ultra-oligotrophic lake according to the classification of Chapman (1996). Secchi disk depth is almost always deeper at the control station. There are events during which visibility is above 10m. This is very rare for any type of lake. Such rare events would disqualify Lake Toba for ASC certification (see section 3.2.2).

Figure 6.9, Secchi depth (in m) measured at the four PTAN locations. (Figure provided by PTAN, 2017. See Figure

3.5 for legend and location of the sites.)



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6.4 Nutrients

6.4.1 Phosphorous

From 2006, when the measurements started, to 2012, phosphorous concentrations were low

(around 0.01 mg/l) with some occasional peaks especially at field station TMK, which was

closed in 2008. These values, presented in Figure 6.10 and Figure 6.11, seem to increase from

2012 onwards, with highest values measured in 2016, in roughly the same months as the other

anomalies (section 6.9.2). Analysis of the BHL-SU data shows that the temporal variation in

total phosphorous (TP) is higher than the spatial variation. Therefore, the average TP

measurements per moment were taken and plotted over time (Figure 6.12). The figure shows

that TP concentrations are mainly below 0.04 mg/l which is in line with the PTAN data for this

period. However, the BHL-SU data show a peak in 2014, at which moment they reach levels

clearly higher than those in the PTAN data (Figure 6.11).

Figure 6.10, Dissolved phosphorous concentration (mg/l) measured at the four PTAN locations over the period

2006-2017. (Figure provided by PTAN, 2017. See Figure 3.5 for legend and location of the sites.)

Figure 6.11, Total phosphorous concentration (in mg/l) measured at the four PTAN locations. (Figure provided by

PTAN, 2017. See Figure 3.5 for legend and location of the sites.)


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Figure 6.12, DLH-SU data on total phosphorous, averaged over all locations throughout Lake Toba in 1996, 2012,

2013, 2014 and 2016. Numbers at the bottom of each bar indicate the number of locations sampled (source:

DLU-SU).

The LIPI data set shows that TP concentrations measured in 2013 vary between 0.012 and 0.041 µg/l, which corresponds well with the previous figures. Station 7 and 8 (with concentrations of 0.019 and 0.015 µg/l) are those closest to the measuring points of PTAN. In the period from 2008 to 2012 the trophic state of the measuring locations is oligotrophic. From 2012 up to the end of 2016 the values correspond to a mesotrophic state.

A study conducted by LIPI in 2010 describes the trophic state of 19 different measuring points

along the coastline of Lake Toba. The state is determined by the values of a series of

parameters measured (Annex J.5). The LIPI findings correspond well with the PTAN figures.

6.4.2 Nitrogen

Total ammonia values at the PTAN control station seem fairly constant. Besides the minor

peaks in 2008, 2011 and 2014, control values are lower than values at fish farm stations (Figure

6.13). Total nitrogen (TN) values are lowest between 2009 and 2014. Measured TN

concentrations do not show a difference between control and fish farm stations. Measured TN

concentrations at the field stations mainly correspond to an oligotrophic state, as they are mostly below the most conservative threshold of 350 μg/l (KLH, 2009), and only very

occasionally exceed the most lenient threshold of 650 μg/l.

In 2013 LIPI conducted another assessment of water quality parameters. As in 2010 they

sampled 19 sites for different parameters. Only total nitrogen (TN) was measured in both years

(Figure 6.14). In 2013 TN was on average lower than in 2010. However, in view of the large

within-year variation (Figure 6.13) this cannot be interpreted in terms of trending. The LIPI 2013

data set shows that TN concentrations measured in 2013 vary between 0.075 and 0.374 mg/l,

which corresponds well with the above figures (see also Annex J.5).



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Figure 6.13, Total dissolved nitrogen (in mg/l) concentrations measured at the four PTAN locations. (Figure

provided by PTAN, 2017. See Figure 3.5 for legend and location of the sites.)

Figure 6.14, Total nitrogen concentrations measured at the four PTAN locations. (Figure provided by PTAN, 2017.

See Figure 3.5 for legend and location of the sites.)

6.5 Organic content Chlorophyll α concentration and dry weight show similar trends at all stations (Figure 6.15 and Figure 6.16). Chlorophyll α values show little difference between stations and all show a sudden peak in 2016. Dry weight values show the same trend, except in this case the values for the control station are lower compared to fish farm stations. Till the end of 2014, chlorophyll concentrations are within the class limit of ultra-oligotrophic lakes. During the period Feb-Aug 2016 however, chlorophyll concentrations rose to12 µg/l and the lake fell within the mesotrophic class (section 5.3).


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Figure 6.15, Chlorophyll concentration (in microgram/l) measured at the four PTAN locations. (Figure provided by


Figure 6.16, Dry weight (in mg/l) measured at the four PTAN locations between 2006 and 2017. (Figure provided by


6.6 Thermocline depth

The thermocline depth has a two-fold importance with respect to eutrophication. Firstly, it

determines the volume over which the incoming nutrients are diluted. The deeper the

thermocline, the more volume, and the lower the concentrations are. Secondly, it determines

whether an algal bloom may occur or not (see also section 2.2.5 and Annex C.2). The depth of

the thermocline in Lake Toba was determined with a simple 1Dv Delft3D-WAQ model assuming

the mixed layer to be fully mixed and a background extinction rate of 0.4 (which corresponds

to a Secchi depth of ~5m). Also, initial TN=0.2 mg/l and TP=0.02 mg/l. The relation between

thermocline depth and chlorophyll concentration resulting from the 1Dv model is shown in

Figure 6.17. The different lines correspond to different thermocline depths, or sequences

thereof: 60_30_20 means that the thermocline depth starts at 60m, but is changed at day 211

to 30m and at day 241 to 20m. The days at which the changes in thermocline depths occur are

fixed.



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Figure 6.17, Chlorophyll concentrations (µg/l) over time (in days) when the thermocline depth is assumed to occur

instantly, or achieved stepwise over time (e.g. from 20 to 30 and 60 meters).

The model results show that the maximum chlorophyll concentrations depend on whether the

thermocline depth is assumed to occur instantly, or whether it is achieved stepwise in time. For

example, when the thermocline depth changes instantly from 60m to 20m, chlorophyll

concentrations reach a peak value of 25 µg/l. However, if they change stepwise from 60m via

30m to 20m, the maximum chlorophyll concentration predicted by the model is 12 µg/l. This is

because algal growth and sedimentation may affect the loss of nutrients from the epilimnion,

and therefore changes the nutrient availability over time.

This analysis suggests that the default thermocline depth in Lake Toba lies around 50m, since

at this depth the modelled chlorophyll concentrations match best with observed chlorophyll

concentrations (Figure 6.15). This depth seems to be in line with the various observed

stratification profiles (e.g. Figure 6.6). A sensitivity analysis of the thermocline depth showed

that P concentrations lowered from about 60 µg/l at 20m thermocline depth to about 20 µg/l at

60m thermocline depth. Ultimately, 50m was selected based on all analyses combined.

According to the results of the 1Dv model, the thermocline depth in 2016 probably decreased

to a depth of 30m or (in a more stepwise manner) to 20m, since at these depths the modelled

chlorophyll matches best with the observed chlorophyll peak (Figure 6.15). Note that this

change in thermocline depth probably corresponds to a change in (or occurrence of the)

secondary thermocline, since the observed 25 °C level (~primary thermocline) is not shifted to

shallower depths (Figure 6.5).

6.7 Remote sensing insights into water quality dynamics

The remote sensing-based analysis of Lake Toba suggested the presence of complex water-

quality dynamics driven by nutrient-oxygen-light mixing. Although Lake Toba is a large and


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deep water mass, surface mixing appears to be driven by hydrologic transport (i.e., in-flow /

outflow).

Evidence of natural and cultural eutrophication is apparent in long-term (MERIS) time-series

data starting around 2006. An approximately two-fold increase in regionally-averaged

Chlorophyll-a from 1~2 mg/m3 to 2~6 mg/m3 and corresponding two-fold increase in light

attenuation at 490nm (turbidity) were observed. In localized areas, the maximum biological

productivity is much higher.

Mesotrophic to eutrophic lake conditions with Chlorophyll-a concentrations of 4 ~ 30 mg/m3

were also derived from Landsat-8 / Sentinel-2A imagery with complex local variability. To

improve the quality of data retrievals, cloud-glint data masking refinements and further regional

tuning are required. Additionally, the long term MERIS time-series and imagery as well as high-

resolution (Sentinel-2A / Landsat-8) imagery show a significant increase in variability (temporal

and spatial) for both chlorophyll / turbidity (Figure 6.18).

Time-series for broad regional segments of Lake Toba show a eutrophic condition of broad

regional segments (period 2013~present) with high level of spatial and temporal variability.

Broad lake aerial binning shows seasonal variability and an increase in Chlorophyll-a and

turbidity by a factor of 2 starting in mid 2005 ~ 2006. The rate of change and variability in

Chlorophyll-a and turbidity also increases during the period between 2006 and 2012 compared

to 2002 to 2005.

Figure 6.18, Ilustration of MERIS example images and time series of Turbidity and Chlorophyll-a for different parts

of Lake Toba.

The impacts of pollution events can also be captured through remote sensing observations. A

water-quality event on January 9th 2017 in the SE of Lake Toba in Bakara /Baktiraja region,

which led to hypoxia and aquaculture loss, is visible in RGB images from space using Landsat-

8, Himawari-8 and Sentinel-3A (VIIRS not verified), as depicted in Figure 6.19. Chlorophyll-a

levels reaching > 10mg/m3 (>30 locally) and evidence of benthic sediment re-suspension

(Figure 5-4) can possibly be explained by significant precipitation and discharge from Aek



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Manira/Silang. Reported meteorological conditions preceding significant precipitation event are

not available, but meteorology visible from Himawari-8 during first week of January. Himawari-

8 observation on Jan 10th shows significantly reduced HAB biological activity, which appears

well correlated with the dissolved oxygen measurements reported at sub 1ppm level (common

threshold supporting biological processes).

Figure 6.19, Illustration event of the Hypoxia and Harmful Algal Bloom (HAB) that occurred on January 9th of 2017,

resulting in hundreds of tons of dead fish in Lake Toba, and the satellite derived images of chlorophyll-a and

total suspended matter.

6.8 Hydrothermal stability and mixing events

Mixing events may have a large impact on the biogeochemistry of the lake (see section 2.2.6).

A brief analysis into the hydrothermal status of the lake has been carried out to explain the

patterns as observed in the temperature and oxygen profile measured over 9 years (from Feb

2008 until Feb 2017) at the PTAN field station Pangambattan located in the narrow passage,

east of Samosir peninsula (Figure 6.5, modified in Figure 6.20). White vertical lines show

instances when the anoxic level is shallow and black lines when it is deep. These instances

coincide with periods of thermal stratification, when the surface water is warm and with periods

of deeper mixing with cooler surface water, respectively. The analysis below is specifically

aimed at understanding the decrease in depth of anoxic water in the period February to August

2016.


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Figure 6.20, Oxygen and temperature dynamics Lake Toba 2008-2017 (after PTAN 2017).

Very little information on the hydrothermal status of and meteorology above Lake Toba is found

in the literature. Yet, Sene et al. (1991) provide some insight into the typical conditions for wind,

air temperature, and humidity over a short period of 42 days in January and February 1989

near Pulo Tao island (1 km north of Samosir, the large central peninsula). From this reference

meteorological observations in the period 2003-2010 were adjusted and the air temperature

was reduced by 3°C accordingly. Figure 6.21 shows the 1DV simulations based on the same

methodology as the 3D hydrodynamic and transport code Delft3D-FLOW of Deltares (Deltares,

2014). In Figure 6.21 the upper panel shows the applied air temperature (black line) and the

simulated surface water temperature (red line) and in the central panel the applied wind

magnitude. The lower panel in Figure 6.20 shows the temperature in the top 100m of the 505m

deep model. From Figure 6.21 it appears that Lake Toba develops a thermocline (warmer top

layer) of marginal stability i.e. with instances of mixing to depths of about 50m. These instances

appear to be bi-annual notably due to the wind of the monsoon cycles.



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Figure 6.21, 1DV run based on Delft3D-FLOW code for Lake Toba with 100 non-equidistant layers over its

maximum 505m depth (upper 100m shown) and meteorological forcing from National University of

Singapore from 2003-2010 and with air temperature reduced by 3 °C, in agreement with Sene et al., 1991.

Top panel: air temperature (black) and surface water temperature (red). Central panel: wind magnitude with

bi-annual increase in wind speed. Lower panel: stratification in water temperature with bi-annual periods

with deeper mixing due increased wind speed.

Patterns in the observed water temperature (Figure 6.20) suggest bi-annual mixing and re-

stratification events in the upper 10-20m in most of the years. The mixing events do not create

deep mixing (i.e. surface water is not mixed downward beyond 50m depth). The latter can be

understood by the reported mild wind pattern e.g. in Sene et al., 1991. Equal patterns in terms

of patterns rather than in precise temperatures can be found in the 1DV simulations (Figure

6.21).

It is this absence of deep(er) mixing that creates the permanent anoxic condition beyond 150m

depths shown in Figure 6.20. In periods of thermal stratification (warm surface water, red

coloured) the upper level of anoxic water rises to shallower depths (black lines in Figure 6.20).

In periods of deep mixing (cooler surface water, green coloured) the upper level of anoxic water

descends to greater depths (white lines in Figure 6.20). The rising of the upper level of anoxic

water appears not to be due to some strong upwelling events, since the observed 25 °C level

is not equally shifted upward with the DO isoline. Therefore, these coincidences are interpreted

as oxygen-rich water being mixed downward from the water surface, or (given some oxygen

consumption) oxygen-depleted water being created in the absence of vertical mixing.

In addition to the Feb-Aug 2016 event with the decreasing depth of anoxic water (more on this

anomaly in section 6.9.2), Figure 6.20 shows some instances with deep cooler water (blue

colour: 24°C). However, these cooler waters do not extend to the water surface. Hence, local


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cooling of the water surface and downward mixing is not the source of this 24°C cooler deep

water. More likely upwelling events from the deeper parts of Lake Toba bring cooler water from

larger depths up into the narrow passage east of the peninsula. Given the size of Lake Toba

north and south basins as well as the temperature stratification, the period of the internal

seiches ranges from 2-4 days. These events appear too short to be visualized in Figure 6.20

unless the sampling period of temperature is long relative to this monthly or other short-term

period and the interpolation of the plotting code artificially widens the cold periods.

If the upwelling events (and the subsequent period with deep cooler water) are not explained

by downward mixing or by internal seiches, what may then be causing them? One option is

some rare stormy event that creates very deep mixing elsewhere in Lake Toba down to depths

exceeding 200m. Temperature and wind speed records do not suggest particular windy or hot

events in February 2016 that would explain the longer temperature stratification and/or anoxic

depth levels (Figure 6.22). Alternatively, it may be caused by cooler (river) inflow which sinks

to larger depths, as is the fate of the cold Rhone River flow into Lake Geneva. Yet another

option is sub-aquatic sources of cooler water, such as are present in Lake Kivu, Rwanda (Ross

et al., 2015).

Figure 6.22, Temperature and wind speed recorded at Medan Airport 80 km North of Lake Toba.

In this brief analysis it is concluded that wind may lead to bi-annual mixing and re-stratification

events in the upper 10-20m in most of the years. Deep mixing does, however, not occur, which

explains the anoxia in the deep layers. Also, some upwelling of cooler water from the deep

occurs. But these cooler waters do not extend to the water surface (at least not in the observed

period). The February to August 2016 event with the decreasing depth of anoxic water seems

to be explained by long cloudless weather conditions during that period. The resulting long and

strong (secondary) temperature stratification in this period is probably the cause of an

exceptionally strong algal bloom (which was indeed recorded by PTAN, see Figure 6.15)

creating high concentrations of detritus and correspondingly large oxygen consumption.



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6.9 Trends

6.9.1 Present data vs historical data

The large volume of Lake Toba may buffer any nutrient input and shield the system from direct

effects (see section 2.2). As a result, changes only become visible when assessed over large

periods of time. In the first half of the previous century Ruttner (1931) conducted a series of

water quality measurements (Table 6.2). In this period the areas surrounding Lake Toba were

not yet affected by aquaculture, agriculture or forestry. In his study Ruttner made a division

between the northern and southern basin of the lake and he was also able to make a depth

profile for oxygen and dissolved phosphates. • Compared to the TP concentrations measured by Ruttner of 0.005 mg/l (in 1930; Ruttner,

1931), orthophosphates as measured by PTAN in 2013 (Figure 6.10) have doubled to 0.01 PO4-P (mg/l), and during the peak in 2016 they even show a tenfold increase to 0.05 PO4-P (mg/l).

• Also at greater water depths phosphorous concentrations are increasing. In 1930 concentrations at 150m depth were measured to be 0.012-0.18 PO4-P (mg/l), whereas in 2013 these values have (more than) doubled to 0.04 PO4-P (mg/l).

• With respect to oxygen, surface water concentrations at PTAN stations (Figure 6.6) seem to have remained constant over the last 90 years. At depths greater than 150 meter however, all DO values between 2008 and 2017 are below 0.5 mg/l (Figure 6.7), which is clearly lower than the values reported by Ruttner and which ranged between 5.35-5.40 mg/l. Potential causes for this difference are discussed in the next chapter.

• Transparency in the 1930’s ranged between 7.5-11.5m, above the limits for ASC certification. Current Secchi disk measurements fluctuate around 6 meters (Figure 6.9), showing a decrease in the average visibility depth of at least 1.5m.

The above comparison of current data to historical measurement clearly suggests that water quality in the lake has decreased since 1930, both at the surface and at greater depths. This may entail some risks as was discussed in section 2.2.6.


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Table 6.2 Values of water quality parameters in 1930 (Ruttner, 1931).

North basin South basin

Temperature (C°) 25.45-26.4 25.45-26.4

Transparency (m) 7.5-11.5 8.0-11.5

Dissolved O2 (mg/l) 7.0-7.6 7.0-7.6

Ortho PO4-P (mg/l) 0.005 0.005

Total PO4-P (mg/l) - -

Total N (mg/l) - -

O2 (mg/l)

Depth (m)

0 7.4 7.56

50 5.35 5.4

100 5.37 2.74

150 4.07 1.54

200 - 1.53

PO4-P (mg/l) Depth (m)

0 0.005 0.005

50 0.005 0.005

100 0.008 0.01

150 0.012 0.018

200 - 0.2

6.9.2 The 2016 anomaly

At the beginning of 2016, all measurements show extreme values. There is an increase in

temperature at the water surface (Figure 6.2) and water temperature (Figure 6.5). This

coincides with a remarkable drop in dissolved oxygen at shallower depth in the period February

to August 2016 (Figure 6.4) (less visible at 2m depth in Figure 6.6). This coincides with other

phenomena, such as the preceding drop in Secchi depth (Figure 6.9) as well as phosphorous

(Figure 6.10 and Figure 6.11). There was a similar sudden peak in chlorophyll concentration

(Figure 6.15) up to 12 µg/l and dry weight (Figure 6.16). This suggests that there was an algal

bloom at that moment and during this period the lake entered the mesotrophic class. The

subsequent increase in visibility to levels above 6m (Figure 6.9) cannot be explained easily.

The anomaly is also visible as a thermal stratification event in the period February – August

2016 (Figure 6.20). This event shows the same pattern as the other thermal stratification

events, but in 2016 the rising of the upper level of anoxic water is particularly strong. What

could have caused this? Temperature and wind speed recorded at Medan Airport 80 km north

of Lake Toba do not suggest particular windy or hot events in Feb 2016 (Figure 6.22). However,

these measurements may not be fully representative for the Lake Toba area as this period was

reported to be (at least locally) particularly cloudless17. This cloudless period could explain the

relatively long and strong (secondary) temperature stratification in this period. This, in turn, may

have caused an exceptionally strong algal bloom (which was indeed recorded by PTAN, see

17 Based on personal observations by JanJaap Brinkman. As the meteorological station is far from Lake Toba, hard

evidence on cloud cover is not available.



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Figure 6.15) creating high concentrations of detritus and correspondingly large oxygen

consumption. However, other causes may have influenced the temporary rising of anoxic water

as well.

6.10 Lake status

The most important determinant of lake water quality is the amount of dissolved nutrients; this

is known as the ’trophic state’. Table 6.3 lists the generally accepted classifications for eutrophic

state. In contrast to other pollutants, continuous nutrient pollution from phosphorous and

nitrogen, ‘eutrophication’, has the potential to irreversibly affect lake chemistry and biology on

a system level. Pollution from as pesticides and pathogens, e.g. E. coli, quickly degrade or

dilute and do not amplify processes that cause irreversible functional system level degradation.

Water transparency, organic content, e.g. chlorophyll-a, phosphorous, and nitrogen are are key

water quality parameters that determine the lake trophic state.

Table 6.3, Overview of types of lake status (Chapman, 1996).

Laks status Description

Oligotrophic

lakes

Lakes of low primary productivity and low biomass associated with low concentrations

of nutrients (N and P). These lakes tend to be saturated with Oxygen (O2) throughout

the water column.

Mesotrophic

lakes

These lakes are less well defined than either oligotrophic or eutrophic lakes and are

generally thought to be lakes in transition between the two conditions. Some

depression in oxygen (O2) concentrations occurs in the lower water layer

(hypolimnion).

Eutrophic lakes Lakes that display high concentrations of nutrients and an associated high biomass

production, usually with a low transparency. Water use may become limited. Oxygen

concentrations can get very low, often less than 1 mg/l in the hypolimnion during

stratification.

Hypereutrophic

lakes

Lakes at the extreme end of the eutrophic range with exceedingly high nutrient

concentrations and associated biomass production. The use of the water is severely

impaired. Anoxia or complete loss of oxygen often occurs in the hypolimnion during

stratification.

Based on available data from monitoring sites scattered along shorelines, observed values in

Lake Toba show mesotrophic status for phosphorous and oxygen profiles while nitrogen,

chlorophyll α and transparency point to oligotrophic status but occasionally reach the

mesotrophic (Table 6.4).


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Table 6.4, Overview of present status of selected water quality parameters at Lake Toba (based on data from DLH-

SU, LIPI, and PTAN).

Parameter Conditions at Lake Toba

Phosphorous

In the period from 2008 to 2012 the trophic state of the measuring locations is oligotrophic for

phosphorous. From 2012 untill the end of 2016 the phosphorous values correspond to a

mesotrophic state.

Nitrogen The measured total nitrogen concentrations at field stations correspond largely to an

oligotrophic state, as they are mostly below the most conservative threshold of 350 μg/l, and

only very occasionally exceed the most lenient threshold of 650 μg/l.

Chlorophyll α Chlorophyll α values show little difference between stations and all show a sudden peak in

2016. Till the end of 2014, chlorophyll concentrations are within the class limit of ultra-

oliogotrophic lakes. During the period Feb-Aug 2016 however, chlorophyll concentrations rise

to 12 µg/l, thereby reaching the mesotrophic class.

Transparency Water transparency (ecchi depth) data from all field stations show a similar trend, reaching

highest values between 2009 and 2010, with a sudden and drastic decrease in 2016 related

to the algal bloom occurring at that moment. After 2016 transparency reaches its initial value

of around 6 meter depth corresponding to an oligotrophic lake according to the classification

of Chapman (1996). There are events during which transparency is above 10 meter depth,

very rare for any type of lake.

Temperature Temperature at water surface varies between 25 and 28 degrees Celsius and has been stable

for the last 10 years. A minor increase is seen in the beginning of 2016, when surface water

temperatures peaks over 28 degrees Celsius. Each PTAN station shows similar trend and

values. Temperature profiles show clear stratification.

Oxygen Levels of dissolved oxygen (DO in mg/l) steadily decline as depth increases and remain the

same beyond 200 meters. Peaks occur in 2006, 2007 and again in 2016, but otherwise values

are stable. One exception is a rise to the surface of anoxic water in the period Feb-Aug 2016.

Stations near fish farms show different values and trends than elsewhere in the lake. Fish farm

locations have lower DO levels and fluctuate within and between years. An interesting

anomaly is seen at one measuring station, where the oxygen value suddenly increases at

around 200 meters depth. This could be caused by nearby thermal vents or be the result of

measurement errors.

The long-term trend gives information on possible “nutrient loading” of the lake, which ultimately

can lead to a change of status. In the first half of the previous century Ruttner (1931) conducted

a series of water quality measurements. In this period, the areas surrounding Lake Toba were

not yet affected by aquaculture, agriculture or forestry. The comparison of current data to these

historical measurements clearly suggests that the water quality in the lake has decreased since

1930, both at the surface and at greater depths (Table 6.5).



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Table 6.5, Trends in water quality of Lake Toba, comparing historical data with present day values.

Parameter Trend at Lake Toba

Phosphorous Compared to the phosphorous concentrations measured by Ruttner of 0.005 mg/l (1931),

the concentrations as measured by PTAN in 2013 have doubled to 0.01 PO4-P (mg/l) and

during the peak in 2016 they even show a tenfold increase to 0.05 PO4-P (mg/l). Also at

greater water depths phosphorous concentrations are increasing. In 1930 concentrations

at 150 meters depth were measured to be 0.012-0.18 PO4-P (mg/l), whereas in 2013

these values had (more than) doubled to 0.04 PO4-P (mg/l).

Transparency Transparency in the 1930’s ranged between 7.5-11.5 meters. Current transparency

(Secchi disk) measurements fluctuate around 6 meters, thus showing a decrease in the

average visibility depth of 1.5 meter.

Oxygen With respect to oxygen, surface water concentrations at PTAN stations seem to have

remained constant over the last 90 years. At depths greater than 150 meter however, all

DO values between 2008 and 2017 show values below 0.5mg/l, which is clearly lower

than the values between 5.35-5.40 mg/l as reported by Ruttner.



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7 Future Pressures and Future State

7.1 Approach

The existing Sumatra Spatial Model (Indra Karya, 2015) has been applied to analyse the Lake

Toba catchment area (section 5.1).

7.2 Input data

These are the input data for the scenarios at Lake Toba:

• Administrative units for 2010: Island; Provinces; Districts; Sub-districts; and Villages. Available as ESRI Shape files from BPS

• Drivers o Population growth scenario (BPS extended) o Economic growth scenario (historic trend data from BPS) o Rice / Palawija / Vegetable production and consumption 2010 data by plus

scenario by district (BPS)

• Unit load scenario for water demand, BOD waste load emissions

• Initial situation data for 2010 (population census year) o Population, households and employment by village from BPS o Land use:

▪ Rupa Bumi Indonesia (BIG), often outdated; needed improvement ▪ Peta Audit Baku Sawah from Ministry of Agriculture (paddy field map)

o Gross Regional Product (GRP) by district and sector from BPS o Province level spatial plans (district level not available) from Bappeda/PU Tata

Ruang o Road development plans

7.2.1 Population and economic growth drivers

Population data in the spatial model are taken by villages (desa) from the 2010 population

census from the Statistical Bureau BPS. This is considered the most reliable and consistent

data source for population in Indonesia. Population projections have been made by BPS per

province from the period 2010-2035. These were used as the basis for Figure 7.1 that shows

the annual multiplier for population growth per 5-year period.


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Figure 7.1, Sumatra population growth history and projection (up to 2035 BPS, remainder of SSM).

Economic growth data per province are available from BPS for the period 2000-2013. At the

level of Indonesia the economic growth has been on average 5% for the last 50 years (BPS).

These data provided the basis for a long-term growth scenario, visualised in Figure 7.2, in close

cooperation with the Ministry of PUPR in Sumatra Water Resources Strategic Study (Indra

Karya, 2015).

1971 1 980 1 990 1 995 2 000 2010 2015 2020 2025 2030 2035 2040 2045 2050

Annual multiplier 1.0613 1.0544 1.0226 1.0119 1.0327 1.0168 1.0143 1.0117 1.0095 1.0077 1.0066 1.0056 1.0046

Sumatra 20,808 28,016 36,506 40,830 43,309 5.1E+07 5.5E+07 5.9E+07 6.3E+07 6.6E+07 6.9E+07 7.1E+07 7.3E+07 7.5E+07

0.97

0.98

0.99

1

1.01

1.02

1.03

1.04

1.05

1.06

1.07

-

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000

80,000,000

Annual multiplier

Sumatra



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Figure 7.2, Economic growth by province 2000-2013 with average of 3.7%.

7.2.2 Spatial plan

One of the main inputs of the spatial model is the spatial plan (Figure 7.3). This model will

inform which areas are still free for conversion into an urban area. Areas indicated as ‘protected’

cannot easily be changed from one use to another. The provincial spatial plans show that part

of the area around Lake Toba is protected land and should not be converted to urban areas.

This was incorporated into the Sumatra Spatial Model.

0.00

20000.00

40000.00

60000.00

80000.00

100000.00

120000.00

140000.00

160000.00

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

11. Aceh

12. Sumatera Utara

13. Sumatera Barat

14. Riau

15. Jambi

16. Sumatera Selatan

17. Bengkulu

18. Lampung


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Figure 7.3, Lake Toba Spatial Plan.

Road development plans are relevant for the spatial model as the increased accessibility

leads to stronger development near planned roads, in particular the toll roads (Figure 7.4).



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Figure 7.4, PUPR Toll Road Development Plan 2009.

7.3 Projections in the Sumatra Spatial Model

The results of the Sumatra Spatial Model for future loads consist of:

• Population and employment projections 2010-2050, and

• Land use change projections 2010-2050

The above projections are available at desa, kecamatan, kabupaten, province, and island level.

With the SSM postprocessor these results are converted to the water districts (Figure 7.5) in

the Lake Toba simulation model. The projection starts with the 2010 population census data.

This is the most reliable population dataset for the intermediary years, but the BPS data on

birth, death and migration statistics are less reliable. Results are analysed for the years 2018,

2022 and 2042 to determine the impact of short term investments over a period of five years

and the long-term impacts after twenty-five years.


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7.3.1 Population projection

Projected population densities in the Lake Toba catchment are visualised in Figure 5.3 for 2018

and in Figure 7.5 for 2042. This includes each desa and keluhahan that drains into Lake Toba.

Subsequently, Figure 7.6 shows the population growth as the difference between projected

populations in 2042 and 2018.

Figure 7.5, Lake Toba catchment population density by desa predicted for 2042 (map provided by Poul Grashoff).

Figure 7.6, Percentage of Lake Toba catchment population growth by desa, 2018-2042 (map provided by Poul

Grashoff).



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Population numbers by water district (and totals by Lake Toba compartment) in combination

with unit waste load data serve to calculate the Lake Toba waste loads. The actual loads to

Lake Toba could be lower due to a reduction of loads during transport in local sewers or via

surface runoff. A correction factor for runoff has been integrated into the model.

7.3.2 Land use change projection

Land use changes are presented here as a proportion of a desa. In other words, it shows how

much of a desa has a certain land use. The waste loads are calculated with most relevant here:

the proportions of urban area, paddy field area and plantations. These are available for each

time step at the desa level. The results have also been converted to water district area forthe

waste load calculation.

For the urban area the results are shown for 2018 and 2042 in Figure 7.7 and Figure 7.8,

respectively. Compared to other regions the Lake Toba catchment area seems less urbanized

(only 4% in 2018) and that will most likely remain so in the near future. Nevertheless, the urban

area grows strongly by about 66% in the Lake Toba catchment area from 2018 to 2042.

Figure 7.7, Urban area fraction by desa in 2018 (map provided by Poul Grashoff).


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Figure 7.8, Urban area fraction by desa in 2042 (map provided by Poul Grashoff).

In terms of land use in the contributing watershed to the lake, a visual analysis of land use in

the Lake Toba catchment from MODIS and Landsat annual products showed limited large-

scale changes in overall vegetative cover observed in the period 2000-2010 (NASA MODIS).

However, pronounced change in land-use is apparent in a localized area SW of Lake Toba

(Aek Manira / Aek Silang aquifer): ~1% reduction in vegetative cover per year in period 2000-

2010 (MODIS PTC) and qualitatively more significant changes in the last 4 years (2013-2017,

Landsat-8 - Figure 7.9).

Figure 7.9, Ilustration of land use change analysis in the Aek Manira/Silang Watershed over the last five years and

the decline of the vegetation cover.



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7.3.3 Tourism

The spatial model does not include tourism as a sector in terms of population. To be able to

include tourism in the waste loads, tourism data were assigned to villages in the Lake Toba

catchment based on the tourism study. That study provided basic data to calculate equivalent

inhabitants and estimation of peak numbers (Table 7.1). These are yearly figures and not all

visitors visit at the same time. However, during the year as well as during the week there will

be peaks in the number of visitors. These peaks are less important in the calculations of

emissions, but crucial in the design of sanitation infrastructure (section 8.4) that will need to be

built for these peak times. To be on the safe side, it is assumed that a maximum of 1/6th of the

total annual number of visitors will be present at the same time (Table 7.1).

Table 7.1, Current and projected number of tourists to Lake Toba (HHTL, 2017).

Business-as-usual scenario Best case scenario

2015 2022 2042 2022 2042

Number of visitors

Domestic 1,743,500 1,978,279 2,219,700 2,125,128 3,128,700

Foreign 58,709 80,408 87,300 86,610 281,600

Total Lake Toba 1,802,209 2,058,686 2,307,000 2,211.739 3,410,300

Average length

of stay (days)

Domestic 2.7 2.6 2.7 2.7 2.6

Foreign 2.1 2.1 2.1 2.1 2.3

Equivalent

inhabitants

13,426 14,816 16,612 16,115 23,930

Peak number of

visitors at one

time

300,368 343,114 384,500 368,623 568,363

Tourism development (planned and unplanned) will take place in certain areas of interest and

attraction. According to ‘Market Analysis and Demand Assessment Lake Toba’ the focus of

future tourism development should be in villages in the following districts: Balige, Girsang

Sipangan Bolon, Simandindo, and Pangururan.

7.4 Nutrient concentration trajectories

Based on the loads calculated in chapter 5, total nitrogen (TN) and total phosphorous (TP)

concentrations were calculated for each of the compartments (see Annex J.4 for details on the

method). The budget model was given parameters as shown in Table 7.2 and Table 7.3. The

thermocline depth was determined on the basis of a simple 1Dv Delft3D-WAQ model (see

section 6.6) at a depth of 50m, and during the Feb-Aug 2016 event at a depth of 20-30m.


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Table 7.2, Properties of the whole lake and two compartments, as assumed in the carrying capacity calculations.

Whole lake 2 compartments

North South

Area (m2) 1,24E+09 6,60E+08 5,84E+08

Average depth (m) 228 206 206

Thermocline depth (m) 20 20 20

Outflow (m3/s) 110 50 110

Volume (m3) 2,84E+11 1,36E+11 1,20E+11

Epilimnion volume (m3) 2,49E+10 1,32E+10 1,17E+10

Table 7.3, Properties of four compartments, as assumed in the carrying capacity calculations

4 compartments

N S1 S2 S3

Area (m2) 6,60E+08 2,78E+07 4,68E+08 8,83E+07

Average depth (m) 90 200 100 80

Thermocline depth (m) 20 20 20 20

Outflow (m3/s) 50 10 110 110

Volume (m3) 5,94E+10 5,56E+09 4,68E+10 7,06E+09

Epilimnion volume (m3) 1,32E+10 5,56E+08 9,35E+09 1,77E+09

The model results were calibrated with the retention rate. The resulting total nitrogen (TN) and

total phosphorous (TP) concentrations match best with the present state when assuming

retention rates of 0.001 and 0.002 for nitrogen (N) and phosphorous (P) respectively. Resulting

TN and TP concentrations and how they depend on the thermocline depth are shown in Figure

7.10.

Obviously, at a smaller thermocline depth nutrients are diluted over a smaller volume which

leads to increased concentrations. At a thermocline depth of 50m (which was set to be the

default depth on the basis of chlorophyll concentrations), total nutrient concentrations averaged

over the whole lake amount to TN=224 µg/l and TP = 26 µg/l. These concentrations both lie

well within the observed ranges of 2015. At a thermocline depth of 20m, nutrient concentrations

increase to TN=467 µg/l and TP=59 µg/l, which correspond well to the observations in 2016.

Results may vary when the calculations are applied per compartment (Figure 7.11). This is due

to local differences with respect to compartment properties (Table 7.2 and Table 7.3) and

loadings. While results for the North compartment seem relatively similar to those of the whole

lake, concentrations in southern compartment S1 are clearly higher, and those in S2 and S3

are lower.



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Figure 7.10, Relation between thermocline depth and total nitrogen (TN) and total phosphorous (TP) concentrations

for the whole lake in 2015 as calculated by the budget model.

Figure 7.11, Assuming a thermocline depth of 50m, total nitrogen (TN) and total phosphorous (TP) concentrations

vary across the lake compartments in 2015 as calculated by the budget model.

The resulting concentrations do not represent the state at the moment of loading, but the

eventual equilibrium that will be reached in the lake compartment over time. Figure 7.12 shows

an example of a how a nutrient load would lead to increased concentrations over time, until a

certain equilibrium concentration is reached. With continuous loads, the equilibrium level would

shift up. The time required to reach the equilibrium is not known, but may be in the order of tens

of years. When the loads are reduced, the resulting concentration slowly goes down over time,

until a new equilibrium is reached (Figure 7.13).

Thermocline depth


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Figure 7.12, Nutrient concentration over time resulting from a load.

Figure 7.13, Shift in nutrient concentration over time resulting from a reduction in load.



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8 Response: water quality management

8.1 Approach

For each contributor of nutrients, potential investment scenarios are presented. Based on

the relative inputs of nutrients, aquaculture (68% of total phosphorous), livestock manure

(19%) and domestic wastewater (11%) have been identified as the starting points for

mitigating measures. Individual measures are discussed in more detail in the sections

below, as well as additional measures to reduce nutrient emissions into Lake Toba. These

additional measures have less impact on overall water quality in the lake, but do provide

other benefits that could be considered in an overall tourism development plan.

The existing Sumatra Spatial Model (section 5.1) quantified the impact of these scenarios

on nutrients, for the three largest sources: aquaculture, wastewater and livestock. In the

model, a future autonomous growth18 is based on predictions of population numbers and

land use for the catchment area of Lake Toba, not the full kabupaten surrounding the lake.

On top of this future autonomous growth, four scenarios have been applied, based on

mitigation measures for aquaculture, domestic wastewater and livestock manure. Various

interventions are possible to reduce the water quality loads into the system. The proposed

scenarios are explored to test their effectiveness in terms of resulting nutrient

concentration. Where other methods have been applied, they are briefly introduced at the

beginning of the section.

Mixing of water in the lake is not homogenous, which means that a load of nutrients in the

North does not immediately affect nutrient concentrations in the South. The mixing is an

unknown variable. Therefore, scenarios have been applied to different options for lake

compartments to show the effect of lack of mixing on the nutrient concentrations in the

lake. Figure 8.1 shows the selected zonation into four compartments. The labels N for

north, S1, S2 and S3 for the three separate southern compartments, are used in many

figures throughout this report.

Figure 8.1, Overview of the four compartments of Lake Toba in which the scenarios have been applied.

18 In the Sumatra Spatial Model, autonomous growth is a projection of population growth that would occur without

any intervention.


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Four different scenarios have been identified. Below is a general description, with a

summary of applied data in Table 8.1.

Scenario A

This is the baseline scenario, without any interventions, for comparison. For population

and livestock, the Sumatra Spatial Model calculates autonomous growth (section 7.3). For

aquaculture the 2015 production level is maintained 84,800 tons with a Food Conversion

Ratio (FCR) of 1.9. For wastewater an estimation of the current facilities is made, assuming

that even if people use on-site sanitation (such as septic tanks or latrines), these are not

functioning properly. For tourism the number of visitors according to the business as usual

forecast is selected.

Scenario B

This is the low scenario, mainly for comparison. For livestock, the Sumatra Spatial Model

calculates autonomous growth. For aquaculture, in the absence of any measures, the

production level is assumed to grow to a maximum level of 106,000 tons with a Food

Conversion Ratio (FCR) of 1.9. For wastewater a slow implementation of the currently

planned water and sanitation program is assumed, in which the number of people with

access to functioning on-site sanitation (such as septic tanks or latrines) increases from

0% in 2018 to 66% in 2022 and 94% in 2042, taking into account natural population growth.

In addition, limited investments in off-site sanitation supply 1% of the population with a

sewerage system in 2022 and 6% in 2042. For tourism, the number of visitors according

to the business as usual forecast is selected, without planning for additional sanitary

facilities. Because of the expected decline in water quality of Lake Toba, growth in

numbers of visitors will eventually decrease as well under this scenario.

Scenario C

This is the intermediate scenario, with interventions in aquaculture, livestock and

wastewater management. For aquaculture, the one remaining license is not renewed and

will expire naturally. There will be increasing pressure on fishfarmers without licenses. This

will likely result in assumed production levels of 64,000 tons in 2018, 50,000 tons in 2022

and 10,000 tons in 2042. For the management of livestock manure, biogas conversion is

promoted, resulting in 1% conversion of manure into biogas in 2018, 20% in 2022 and

40% in 2042. For wastewater, the currently water and sanitation program is implemented

as planned. Thus, the number of people with access to on-site sanitation (such as septic

tanks or latrines) increases from 50% in 2018 to 85% in 2022 and 94% in 2042. In addition,

limited investments in off-site sanitation supply 2% of the population with a sewerage

system in 2022 and 6% in 2042. As a result, the percentage of people practicing open

defecation decreases from 50% in 2018 to 13% in 2022 and 0% in 2042. For tourism, the

number of visitors according to the best-case scenario is selected, without planning for

additional sanitary facilities.

Scenario D

This is the high scenario, the most optimistic one, with interventions in aquaculture,

livestock and wastewater management. For aquaculture, an active reinforcement policy

ensures that the production level is reduced to 10,000 tons in 2022 and 2042. In addition,

better feeding practices in the remaining cages allow for a better food conversion ratio of

1.2. For the management of livestock manure, biogas conversion is promoted more

actively, resulting in 5% conversion of manure into biogas in 2018, 30% in 2022 and 60%



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in 2042. For wastewater, the water and sanitation program is accelerated with additional

funding. Thus, the number of people with access to on-site sanitation (such as septic tanks

or latrines) increases from 50% in 2018 to 69% in 2022 and then drops to 50% again in

2042. Off-site sanitation takes off so that in 2022 31% of the population is connected to a

central sewerage system, growing to 50% in 2042. As a result, the percentage of people

practicing open defaecation quickly decreases from 50% in 2018 to 0% in 2022 and 2042.

For tourism, the number of visitors according to the best case scenario is selected and

these numbers are included in the wastewater treatment plans.

Table 8.1, Overview of four investment scenarios to reduce nutrient loads into Lake Toba.

Driver Scenario A

Baseline

Scenario B

Low

Scenario C

Intermediate

Scenario D

High

Aquacultur

e

Extrapolation

of 2015

situation

Growth to

maximum potential

Gradual reduction of

production

Rigorous reduction of

production

2018

2022

2042

84,800 tons

FCR 1.9

106000 tons

FCR 1.9

64,000 tons, FRC 1.9

50,000 tons, FCR 1.9

10,000 tons, FCR 1.9

64,000 tons, FRC 1.2

10,000 tons, FCR 1.2

10,000 tons, FCR 1.2

Livestock Conversion of manure into biogas

2018

2022

2042

Extrapolation

of current

situation

Extrapolation of

current situation

1% conversion

20% conversion

40% conversion

5% conversion

30% conversion

60% conversion

Wastewater

No

intervention

Slow

implementation

Implementation as

planned

Accelerated

implementation

2018

2022

2042

On-site: 50%

On-site: 50%

On-site: 50%

On-site: 50%

On-site: 66%, Central : 1%


On-site: 50%

On-site: 85%, Central: 2%


On-site: 50%



Tourists per

year

Business as

usual

Business as usual Best case Best case

2018

2022

2042

1,802,200

2,059,000

2,307,000

1,802,200

2,059,000

2,307,000

1,802,200

2,212,000

3,410,300

1,802,200

2,212,000

3,410,300

The potential impact of these scenarios is shown in the graphs below, showing the relative

contribution of each driver to nitrogen (Figure 8.2) and phosphorous (Figure 8.3) loads in

Lake Toba. Clearly the intermediate C and high D scenarios have most substantial impacts

on nutrient loadings. For nitrogen, there is hardly any visible impact from interventions in

livestock and wastewater. For phosphorous this is somewhat more visible, but true

reductions are only achieved when aquaculture is reduced (blue colour in intermediate C

and high D scenarios). In the next sections the individual contributions for aquaculture,

livestock and wastewater on nutrient loads and concentrations are explained. At the end

of the chapter, the impact of combined scenarios on nutrient loads and concentrations is

presented for each of the four lake compartments.


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Figure 8.2, Nutrient loads of total nitrogen resulting from four different scenarios with combined measures in

management of nutrient emissions from aquaculture, livestock manure and wastewater, in the whole

Lake Toba (as one compartment). See Table 8.1 for the input data in each of the scenarios.

Figure 8.3, Nutrient loads of total phosphorous resulting from four different scenarios with combined

measures in management of nutrient emissions from aquaculture, livestock manure and wastewater,

in the whole Lake Toba (as one compartment). See Table 8.1 for the input data in each of the

scenarios.



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8.2 Aquaculture

8.2.1 Investment scenario

8.2.1.1 Infrastructure

The main interventions in aquaculture would be institutional in nature. However, supporting technical measures, not limited to infrastructure, could play a role. In existing aquafarms, the feeding efficiency could be increased by changing the stock/feed ratio, breeding different types of fish and using alternative feed. Such interventions are part and parcel of good aquaculture business models as efficient businesses make more profit, and the related investments are borne by the companies themselves.

For 2015 the production of PT Aquafarm Nusantara (PTAN) was modelled at the maximum

licensed amount of 36,000 tons of fish and that of PT Suri Tani Pemuka at 9,700 tons

(Table 5.2). Small-scale aquaculture farmers produced around 39,100 tons and the total

fish production at Lake Toba was set at 84,800 tons in 2015 (Table 5.2).

In 2016 the production had dropped to 74,400 tons, mainly because of the low production

at PT Suri Tani Pemuka (Table 2.3). At the same time, PTAN moved some of its cages

from the coast of Samosir in the northern compartment to the sourthern compartment S2.

Since 2016, when several districts took action to reduce aquaculture (section 3.4.4.1),

many smallholders across Lake Toba abandoned their cages. Subsequently, their total

production dropped from some 16,400 tons in 2015 (Table 5.2) to approximately half that

level in 2017 (sections 8.4.2.4 and 8.4.3). Those in Haranggoal Bay took this opportunity

and increased their production (Table 8.5).

Whereas the fish cages are located in lake compartments, their owners reside in districts.

The aquaculture producers in Haranggoal Bay are mainly from the district of Simalungun

and for them it is a major source of income. The other smallholders live across all of the

districts that surround Lake Toba. Many of them have abandoned their fish cages since

2016. Some rent out their overgrown cages, as pontoon or jetty for fishing. Tourists pay a

fee to use the cages for sport fishing on the lake. The people who still have productive fish

cages spread around Lake Toba, reside in various districts, not necessarily near their

cages. They serve tourism as well, because the fish is sold to local restaurants, where it

is served as a special dish of the region.

8.2.1.2 Institutional

An obvious scenario for reducing nutrient loads from aquaculture would be via licenses.

With the exception of PT Aquafarm Nusantara, none of the producers had formal licenses

in 2017 (Table 3.1). More information is needed on the extent of current aquaculture

activities (see section 8.2.1.3). Subsequently, concerted efforts are needed to gradually

phase out the existing licenses by not issuing new licenses and not renew the expired

ones, or only temporarily renew for a limited period, and improve compliance (scenario C).

Or a more active approach could be selected, in which no licences are issued or renewed

at all, and compliance is enforced immediately (scenario D). This would speed up the

process of reducing the nutrient load from aquaculture into Lake Toba. The purpose of this

scenario would be to achieve the carrying capacity limit of 10,000 tons per year by 2022.


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At the time of this draft report,19 the status of the PTAN license is unclear. Should this

license not expire prior to 2022, other options should be explored to achieve this scenario;

perhaps activey revoke the license of PT Aquafarm Nusantara. This may require an

intensive political process, for instance resulting in a new presidential decree, with

subsequent institutional backup.

For smallholders, who all operate without a license, a different approach, with emphasis

on law enforcement, is necessary. These people have been allowed to practise

aquaculture for several years. The producers in Haranggoal Bay, in the district of

Simalungun depend on aquaculture for their livelihoods. The investment scenarios

envisage a modest production level in Haranggoal Bay, of some 5,000 tons per year in

total. A similar quantity could be tolerated for the other smallholders, spread around Lake

Toba. Together, all smallholders could produce the maximum of 10,000 tons per year.

However, they need support to do this at the right place, i.e. at least 10 m away from the

shore, and where the water is at least 100m deep. Technical support and capacity building

efforts are also required to help these smallholders increase their efficiency so that they

can eventually achieve a food conversion ratio of 1.2.

Law enforcement on licensing and aquaculture practices (section 3.4.2) has a key role to

play in rolling out these strategies. Civil servant investigators, for instance under

responsibility of the Ministry of Marine and Fisheries, or the Ministry of Public Works and

Housing, can act on the information collected in the monitoring survey (see section 8.2.1.3)

and start court cases against companies or individuals that operate unlicensed

aquaculture farms.

For smallholders who may only have a few fish cages, as well as for people currently

working at the large aquaculture companies, alternative livelihood options need to be

supported. Several of the current individual aquaculture farmers used to practise

horticulture and grew cops such as onions. With some government support, they could

explore other profitable livelihood options, for instance in fisheries, organic farming or

(eco)tourism. Dedicated trainings could be developed by the ministries of Marine and

Fisheries, Agriculture, and Tourism, and delivered by the line agencies at the kecamatan

level, for instance the agricultural extension centers. Local foundations could also play a

role, for instance Yayasan Bina Sarana Bakti located in Ciawi, Bogor, that has been

established since 1984. The local government can collaborate with the tourism sector in

market development, boosting demand for native fish (e.g. batak or jurung) and vegetables

amongst tourists as well as for local consumption.

8.2.1.3 Information

The various strategies proposed above would benefit from sector-specific studies to further

guide the development of training and other supporting measures. A first step is to take

stock of the current licensing status and process in more detail (see section 8.2.1.3). This

effort would have to be supported with a strong legal mandate, not only to provide more

in-depth information on the process of licensing (section 3.4.4.1), but also to reveal more

details on the exact extent, validity and limitations of issued licenses. This includes

19 The Consultant will seek to close this information gap.



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guidelines or restrictions on for instance distance from the shore, minimum water depth

and maximum Secchi depth where aquaculture is permitted.

In addition, information has to be collected on the current aquaculture activities

themselves. At the time of this study (2017), all fish cages except those of PTAN are

operated without a license. A monitoring strategy is required to check where exactly the

fish cages are located, who owns them and how they are operated. This would include

monitoring of good practice, such as whether the minimum distance of the cages is indeed

10 meters from the shore in areas of at least 100 meters deep, as specified in Presidential

Regulation No. 81/2014 (section 3.4.2). Local leaders (tokoh adat) may play a role in this

as part of a participatory monitoring program.

8.2.1.4 Costed scenarios

Intermediate scenario C envisages a relatively slow phase-out of aquaculture: no new

licenses are issued and the remaining one for PT Aquafarm Nusantara is assumed to

expire between 2022 and 2042. At the same time, smallholders in Haranggoal Bay and

elsewhere at Lake Toba are not immediately forced to abandon the remaining fish cages.

Table 8.2 shows how the resulting fish production would be distributed over the

compartments. PT Aquafarm Nusantara will continue to produce 30,000 tons in 2018 and

2022 while PT Suri Tani Pemuka will phase out production from 4,000 tons in 2018 to none

in 2022. Aquaculture farmers in Harangoal Bay will reduce production from 23,100 tons in

2018 to 13,100 tons in 2022 and 5,000 tons in 2042. Other smallholders, spread around

Lake Toba and mainly producing fish for the local restaurants, will together produce 6,900

tons in 2018 and 2022, and 5,000 tons in 2042. In the small and fragile compartment S1

no aquaculture activities would be allowed in 2042. For Scenario C a Food Conversion

Ratio of 1.9 is assumed.

Table 8.2, Projected fish production in 2018, 2022 and 2042 in intermediate scenario C across the

compartments per group of aquaculture producers (in tons of fish per year).

Producer Estimated production 2018

N S1 S2 S3 total

PT Aquafarm

Nusantara

9,000 21,000 30,000

PT Suri Tani

Pemuka

4,000 4,000


Other smallholders 3,000 1,000 2,000 900 6,900

Total 39,100 1,000 23,000 900 64,000

Percentage

production

61% 2% 36% 1%

Percentage emission 69% 1% 29% 1%


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Estimated production 2022

Producer N S1 S2 S3 total

PT Aquafarm

Nusantara

9,000 21,000 30,000

PT Suri Tani

Pemuka

0 0



Total 25,100 1,000 23,000 900 50,000

Percentage

production

50% 2% 46% 2%


Estimated production 2042

Producer N S1 S2 S3 total

PT Aquafarm

Nusantara

0 0

PT Suri Tani

Pemuka

0 0


Other smallholders 2,100 0 2,000 900 5,000

Total 7,100 0 2,000 900 10,000

Percentage

production

71% 0% 20% 9%


Contrary, scenario D aims at a rapid decrease in fish production with immediate action

against unlicensed aquafarming and no new or renewed licenses. The one remaining

license for PT Aquafarm Nusantara is assumed to either expire before 2022 or to be

revoked before that year. Compliance with the law will be actively enforced and most

smallholders will be forced to abandon the remaining fish cages. The aquaculture farmers

at Harangoal Bay as well as the other smallholders will be allowed to continue aquaculture

at a lower level, each group producing no more than 5,000 tons per year. In the small and

fragile compartment S1 no aquaculture activities would be allowed in 2022. With better

feeding practices, they would be able to reach this production with less feed. Thus, the

targeted fish production of 10,000 tons for the whole of Lake Toba will be reached by 2022,

efficiently produced with a food conversion ratio of 1.2.



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Table 8.3, Projected fish production in 2018, 2022 and 2042 in high scenario D across the compartments per

group of aquaculture producers (in tons of fish per year).

Producer Estimated production 2018

N S1 S2 S3 Total

PT Aquafarm

Nusantara

9,000 21,000 30,000

PT Suri Tani

Pemuka

4,000 4,000



Total 39,100 1,000 23,000 900 64,000

Percentage

production

61% 2% 36% 1%


Producer Estimated production 2022 and 2042

N S1 S2 S3 total

PT Aquafarm

Nusantara

0 0

PT Suri Tani

Pemuka

0 0


Other smallholders 2,100 0 2,000 900 5,000

Total 7,100 0 2,000 900 10,000

Percentage

production

71% 0% 20% 9%


In Table 8.4 the various potential interventions are listed with estimated costs under two

scenarios, intermediate scenario C and high scenario D.

Table 8.4, Overview of estimated investment costs for the period 2018-2022 to reduce nutrient loads from

aquaculture into Lake Toba, in an intermediate scenario C (target production of 50,000 tons in 2022;

FCR 1.9) and a high scenario D (target production of 10,000 tons in 2022; FRC 1.2).

Summary

investments

C. Intermediate D. High

Duration

(years) OPEX20 OPEX Responsibility

Infrastructure

Buy better feed 0 50 Aquaculture companies,

smallholders

5

Institutional

Coordination 200 400 Ministry of Marine and

Fisheries, local government

5

Law enforcement:

monitoring

100 200 ATR BPN, Ministry of

Marine and Fisheries, BWS

Sumatera II, traditional

leaders

5

20 OPEX = Operational Expenses, running costs; total fore five years.


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Summary

investments


Duration

(years) OPEX20 OPEX Responsibility

Law enforcement:

investigation

50 100 Civil servant investigators

under ATR BPN, Ministry of

Marine and Fisheries, and

Ministry of Public Works

and Housing

5

Training on fisheries 600 4,000 Ministry of Marine and

Fisheries

3

Training on organic

farming

1,200 4,000 Ministry of Agriculture, local

foundations

3

Training on

ecotourism

600 4,000 Ministry of Tourism 3

Market development 500 4,000 local government, tourism

sector

5

Information

Guiding studies 1,500 4,500 Ministry of Marine and

Fisheries

1,5

Awareness campaign 4,950 12,900 Ministry of Environment

and Forestry, Ministry of

Marine and Fisheries

3

Total (million IDR) 9,700 34,150

US$ equivalent 718,785 2,530,567

8.2.2 Impact on nutrients

The effects of measures to reduce pollution in aquaculture are the largest compared to

measures taken on other sources of pollution. The impact of reduced fish production has

been modelled for the two investment scenarios in comparison with a baseline and

business-as-usual scenario: A. Baseline: Fish production as is, at 84,800 tons per year with FRC 1.9;

B. Low: Let capacity grow to maximum of licenses: 106,000 tons with FRC 1.9;

C. Intermediate: No new licenses, let licenses expire naturally and enforce gradually

from 64,000 tons in 2018 to 50,000 tons in 2022 and 10,000 tons in 2042, all with

FRC 1.9;

D. High: Actively reduce aquaculture from 64,000 tons in 2018 to 10,000 tons from 2022

onwards, with FRC 1.2.

Similar to the load calculations in section 5.1.2, emissions per fish cage are the same for

commercial and smallholder aquaculture producers. Commercial producers have a double

yield per cage as they can produce more efficiently. This explains why the percentages of

fish production in each compartment are not the same as the percentages emissions.



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In the baseline scenario A the same total fish production of 2015 is taken (Table 5.2) and

kept at a constant level from 2018 to 2042. However, the distribution across the

compartments has shifted since 2015 (section 8.2.1.1). In 2016, PTAN has moved some

of its cages from the north to the southern compartment S2. Since 2016, when several

districts took action to reduce aquaculture (section 3.4.4.1), many smallholders across

Lake Toba abandoned their cages and production dropped from 16,400 tons in 2015 to

8,200 tons in 2018. Those in Haranggoal Bay took this opportunity and increased their

production from 22,700 tons in 2015 to 30,900 tons in 2018 (Table 8.5).

Table 8.5, Projected fish production in 2018, 2022 and 2042 in baseline scenario A across the compartments

per group of aquacultureproducers (in tons of fish per year).

Producer Estimated production

N S1 S2 S3 total

PT Aquafarm

Nusantara 10,800 25,200 36,000

PT Suri Tani

Pemuka 9,700 9,700



Total 54,700 1,600 27,600 900 84,800

Percentage21

production 65% 2% 33% 1%


Contrarily, low investment scenario B allows for unlimited growth up to a total production

level of 106,000 tons per year from 2018 to 2042. PT Aquafarm Nusantara would produce

36,000 tons per year according to its. PT Suri Tani Pemuka is assumed to increase

production to the level of the original license, i.e. 30,000 tons per year. Aquaculture at

Haranggoal Bay will increase to 31,800 tons per year, while the total production of other

smallholders will stay at 8,200 tons per year (Table 8.6).

Table 8.6, Projected fish production in 2018, 2022 and 2042 in low investment scenario B across the

compartments per group of aquacultureproducers (in tons of fish per year).

Producer Estimated production

N S1 S2 S3 total

PT Aquafarm

Nusantara 10,800 25,200 36,000

PT Suri Tani

Pemuka 30,000 30,000



Total 75,900 1,600 27,600 900 106,000

Percentage

production 72% 2% 26% 1%


21 Because of rounding, percentages in tables may not exactly add up to 100%. The model applies the calculated,

non-rounded percentages.


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118

Nitrogen (N) and phosphorous (P) loads would drop dramatically when fish production is

limited to 10,000 tons/year. See Figure 8.4 for the whole lake compartment estimates. The

graphs show the high load under the static baseline scenario A with current production of

84,800 tons, and even higher loads under the low scenario B with the maximum fish

production of 106,000 tons. The intermediate scenario C, with gradually decreasing

production over time, gives lower loads. Obviously, the high scenario D has lowest loads.

In 2024 the difference between scenario C and D is clearly visible. Due to the Food

Conversion Ratio (FCR) of 1.2 in scenario D, its loads are almost half of those in scenario

C, where a food conversion ratio of 1.9 has been applied. The resulting load in 2042 for

scenario C is what would have been achieved in 2022 for scenario D if a food conversion

ratio of 1.9 instead of 1.2 had been applied.

Figure 8.4, Projected impacts of two intervention scenarios (C & D) and two comparison scenarios (A & B) on

loads from aquaculture and resulting long-term concentrations of nitrogen (left) and phosphorous

(right) for the whole of Lake Toba.

In Figure 8.4 projected nutrient concentrations are indicated, that would be the long-term

result from the load in a certain year, if aquaculture would be the only source of nitrogen

and phosphorous. The displayed concentrations thus represent equilibrium

concentrations on the basis of input data for 2018, 2022 and 2042. It may take tens of

years to achieve each of these equilibrium states (Figure 7.13) and in reality additional

sources will add to the load (section 0). Limits for oligotrophic and mesotrophic state have

been indicated for phosphorous at 10 and 30 μg/l respectively, and for nitrogen the

oligotrophic limit of 350 μg/l is displayed (based on Nürnberg, 1996; Table C.2 in Annex

C.3). Figure 8.5 shows the nitrogen and phosphorous loads and lon-term concentration

under the four aquaculture scenarios applied to the best zonation in four compartments.

The graphs show loads and concentrations by compartment at fixed scales to enable

comparisons between compartments.

The reductions in nutrient loads are particularly strong in the northern compartment N,

where many fish cages are situated, and in S2. In all compartments the long-term

phosphorous concentrations would drop below the limit of 10 μg/l, at minimum fish

production levels (scenario C in 2042 and scenario D in 2022 and 2042). This means that

the maximum production level of 10,000 tons/year on its own would not threaten the long-

term oligotrophic state for the compartments. However, continued loads may still lead to

local eutrophication effects.



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Figure 8.5, Projected impacts of two intervention scenarios (C & D) and two comparison scenarios (A & B) on

loads from aquaculture and resulting long-term concentrations of nitrogen (left) and phosphorous

(right) across the four compartments North, S1, S2, and S3 of Lake Toba.


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8.3 Managing livestock manure

8.3.1 Investment scenarios

Converting livestock dung into a valuable energy source (e.g. biogas) is one way to avoid

pollution from manure entering Lake Toba. Unless animal manure is managed carefully to

minimize odor, nutrient losses and emissions, it becomes a source of pollution and a threat

to aquifers and surface waters. It can also be a direct threat to human and livestock health.

Used appropriately, livestock manure is a valuable resource that can replace significant

amounts of chemical fertilizers. As biogas, it becomes a renewable energy source capable

of reducing the use of fuel-wood and fossil fuels.

The Indonesian Domestic Biogas Programme (IDBP) is in Indonesia better known as the

BIRU programme; an acronym of Biogas Rumah, or ‘biogas for the home’. BIRU aims to

promote the use of bio-digesters as a local, sustainable, energy source by developing the

market while working towards the development of a commercial, market-oriented sector,

leading to the creation of jobs. It is an initiative of two Dutch NGOs, Hivos and SNV. Closely

working with the Indonesian Ministry of Energy and Mineral Resources, the program is

implemented by Yayasan Rumah Energi (YRE) with funds made available by EnDev

(Energising Development), the Norwegian and Netherlands Embassies, together with

partners in promoting access to a modern and sustainable form of renewable energy for

rural people. BIRU started in May 2009 with financial support from the Netherlands

Embassy. As of November 2015, it has built 16,015 biogas digesters in nine provinces in

Indonesia. At the moment, BIRU works in ten provinces in Indonesia: Lampung, West

Java, Banten, Central Java, DI Yogyakarta, East Java, South Sulawesi, Bali, West Nusa

Tenggara dan East Nusa Tenggara (Sumba).

Additional recommendations on the conversion of livestock manure into biogas and more

generally, on the sustainable management of manure, can be found in Annex L.

8.3.1.1 Biogas infrastructure

The amount of biogas production differs per animal (Table 8.7). For comparison, 1 m3 of

biogas equals ± 0.46 kg LPG, ± 0.62 litre of kerosene, or ± 3.5 kg of wood.

Table 8.7, Biogas production from selected domestic animals

Organic material Biogas produced (l/kg)

Cow dung 40

Buffalo dung 30

Pig dung 60

Chicken dung 70

The fixed dome biogas plant has a minimum life of 15 years if properly operated and

maintained. Maintenance is easy; it merely requires the occasional checking and – if

necessary – repair of pipes and fittings. To operate one unit, the farmer needs to have at

least two cows or seven pigs (or a flock of 170 poultry) to produce enough feed for the

reactor to be able to generate sufficient gas to meet their daily basic cooking and lighting

needs22.

22 www.biru.or.id



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At household level the choice between an individual biogas and communal biogas

installation for several households depends on the distance between houses. The cost to

construct a biogas plant at household level is in the range IDR 6.0 – 7.5 million. A

successful pilot (suggested at minimum three areas), with support of intensive advocacy

and training, will increase the trust of the community to accept and replicate the initiative

in other places.

Under the intermediate scenario, 11 pilot biogas plants will be constructed and double this

number, 22 biogas plants, under the high investment scenario. Likewise, the second phase

of upscaling will be implemented with double efforts under the high scenario to ensure

30% update by 2022, as compared to the intermediate one (aimed at 20% uptake by

2022).


An action plan for the management of pollution from livestock covering all municipalities

around Lake Toba should be considered. It has to be facilitated by the Livestock and

Animal Health Agency of North Sumatra Province in coordination with related agencies in

each kabupaten and the Lake Toba Tourism Area Management Authority. Cooperation

with Yayasan Rumah Energi (YRE) or others for the implementation of biogas production

should be further investigated.

Supporting institutional efforts such as coordination between kabupaten and training

efforts under the high investment scenario are roughly one and a half to two times that of

the intermediate scenario.

8.3.1.3 Information

There is insufficient reliable information on the concentration of livestock owned by

individual farmers and by big companies. Guiding studies help to select the most promising

sites for the pilot biogas plants and for trainings.


In Table 8.8 the various potential interventions introduced above are listed with estimated costs under two scenarios, grouped into categories for infrastructure, institutional activities and information campaigns. More detail on the proposed activities is provided in annex L. Under the intermediate scenario C, 17 pilot biogas plants will be constructed, supported with upscaling activities and training resulting in 20% uptake in 2022. A higher number of 22 biogas plants will be implemented under the high investment scenario D, coupled with more intensive supporting activities, resulting in 30% uptake by 2022.


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livestock manure into Lake Toba, in an intermediate scenario C (conversion of 20% of manure into

biogas in 2022) and a high scenario D (conversion of 30% of manure into biogas in 2022).


CAPEX23 OPEX24 CAPEX OPEX Responsibility Duration

Infrastructure

Pilot project biogas

340 26 440 33 Dinas Peternakan at 7 kabupaten - coordinated by Dinas Peternakan & Kesehatan Hewan (DPKH) provinsi

18 months

Upscaling biogas installations

5,000 1,000 7,000 1,400 4 years

Institutional

Coordination

300

400

DPKH Province Sumatera Utara

5 years

Training

2,500

4,000 5 years

Information

Guiding studies

3,000

4,500 DPKH Kabupaten & Province Sumatera Utara

18 months

Campaign 750 1,000

Subtotal 5,340 7,576 7,440 11,333

Total (million IDR)

12,916 18,773

US$ equivalent (000, split)

396 561 551 840

US$ equivalent (000, total)

957 1,391

8.3.2 Impacts on nutrients

Future autonomous growth is based on predictions of population numbers and land use of

the Sumatra Spatial Model (baseline). On top of this future autonomous growth, the two

investment scenarios were applied and compared to the baseline. These are as follows:

A. Minimum: Business as usual, including the projected growth, no mitigations;

B. Low: Same as A;

23 CAPEX = Capital Expenses. 24 OPEX = Operational Expenses, running costs; total fore five years.



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C. Intermediate: Increasing conversion of manure into biogas, resulting in 1% uptake in

2018, 20% in 2022 and 40% in 2042, with an assumed efficiency of 70% reduction of

both nitrogen and phosphorous loads;

D. High: Accellerated conversion of manure into biogas, resulting in 5% uptake in 2018,

30% in 2022 and 60% in 2042, with an assumed efficiency of 70% reduction of both

nitrogen and phosphorous loads.

The effects of livestock nutrient emission measures are shown in Figure 8.6 for the whole

lake compartment estimates. The impact of the measures is limited. The intermediate

scenario C can just compensate for autonomous growth. For phosphorous the impact is a

bit more pronounced, particularly for high scenario D.

Figure 8.6, Projected impacts of two intervention scenarios (C & D) and a comparison scenario (A & B) on

loads from livestock and resulting long-term concentrations25 of nitrogen (left) and phosphorous (right)

for the whole of Lake Toba.


result from the load in a certain year, if livestock manure would be the only source of

nitrogen and phosphorous. The displayed concentrations thus represent equilibrium

concentrations on the basis of input data for 2018, 2022 and 2042. It may take tens of

years to achieve each of these equilibrium states (Figure 7.13) and in reality additional

sources will add to the load (section 0). Limits for oligotrophic and mesotrophic state have

been indicated for phosphorous at 10 and 30 μg/l respectively (based on Nürnberg, 1996;

Table C.2 in Annex C.3). For nitrogen, the resulting concentrations stayed well below the

limit of 350 μg/l for an oligotrophic state.

Figure 8.7 shows the nitrogen and phosphorous loads and long-term concentration under

the three livestock scenarios (scenarios A and B are the same) applied to the best zonation

in three compartments. For compartment S3 insufficient data were available so no reliable

modelling could be performed. For calculations of the loads in the whole lake, this made

no significant difference. The graphs show loads and concentrations by compartment at

fixed scales to enable comparisons between compartments.

The graphs show increasing loads under the autonomous growth scenario A/B. The

conversion of biogas at intermediate intensity in scenario C and even at higher intensity in

scenario D has a limited effect on nutrient loads. However, in the northern compartment

25 As scenario A and B are the same, the concentrations for scenario A are not visible; these are the same as for

scenario B.


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N, the reduction of phosphorous loads under the high scenario D would eventually lead to

concentrations below the oligotrophic limit of 10 μg/l. In the smallest southern compartment

S1 the low loads would lead to concentrations at the mesotrophic level, even when manure

is converted into biogas (scenarios C and D). Without interventions, scenario A/B, the

increasing loads would contribute to a eutrophic state.

Figure 8.7, Projected impacts of two intervention scenarios (C & D) and a comparison scenario (A & B) on

loads from livestock and resulting long-term concentrations26 of nitrogen (left) and phosphorous (right)

across three compartments North, S1, and S2 of Lake Toba. For compartment S3 insufficient data

were available.

26 As scenario A and B are the same, the concentrations for scenario A are not visible; these are the same as for

scenario B.



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8.4 Wastewater (domestic and tourism) management

8.4.1 Approach and background

This section covers domestic wastewater (sewage), with special attention to the tourism

industry. The initial input for the inventory of the existing and planned infrastructure related

to sewage is based on the sanitation strategies (e.g. BPS, SSK, MPS) for each kabupaten

in the catchment (Annex M, see also USDP, 2015). The selection of type of wastewater

treatment facilities is based on the approach explained in the Buku Referensi (TTPS,

2009). This approach aims to reduce the risk to health and environment at the lowest costs.

Thus, in urban areas with high population densities and high exposure levels, on-site

systems (septic tanks) are no longer preferred and off-site systems with improved

performance (removal efficiencies) are selected, which is a general applied approach

(UNEP, 2004).

Increasing the water supply coverage increases wastewater flow, but this has no impact

on the wastewater investments as these depend on the number of people covered and

unit investment cost per person. In the calculations below an assumption of average

wastewater flows based on full water supply coverage has been included.

An important input in terms of present tourism activity (numbers of visitors and tourist

centers) and its expected development is the recently carried out tourism demand

assessment (section 7.3.3).

Most hotels and restaurants still discharge the wastewater directly into Lake Toba. Out of

45 hotels only three are connected to the sewer system. The system is under the

responsibility of PDAM Tirtanadi. The facilities have not been regularly maintained and are

currently in a poor condition. The one wastewater treatment plant (IPAL) in the Lake Toba

area, is in Parapat. It has been constructed in 1996 with a loan from the Japanese

Overseas Economic Cooperation Fund, OECF (IDR 7.3 billion) and is operational since

2000. The system has 15,000m sewerage pipeline equipped with 128 man-holes and three

pump rooms. It has a capacity to treat 900 to 2,000 m3/day (equal to 3,000 house

connections) and occupies two hectares of land. In 2017 only 200 households are

connected, so the IPAL functions at only 10% of capacity (personal information, Mr Joni

Mulyadi, manager at PDAM Tirtabadi, November 2017). The pumps and other equipment

require rehabilitation. In addition, the sewer pipes are leaking.

New wastewater treatment facilities have been planned for Balige and Toba Samosir

Districts. However, a budget has not been secured yet and no timeline for implementation

has been set. The implementation of new wastewater treatment plants (IPAL - Instalasi

Pengolahan Air Limbah) or fecal sludge treatment plants (IPLT - Instalasi Pengolah

Lumpur Tinja) are often constrained due to delays from the land acquisition process. Many

land plots have cultural significance and require confirmation and approval from the family

or the clan that owns the land before any infrastructure can be built).

Domestic wastewater may not be the major contributor to the pollution of Lake Toba. Other

aspects such as health, wellbeing and environmental amenities make it necessary to

address proper disposal of wastewater—in particular in the light of tourism development.

For the assessment of required infrastructure, calculations have been made for all desa


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and keluhuran within the catchment area draining into the lake, hence not for the entire

kabupaten. For tourists, peak numbers of visitors have been calculated as follows (based

on Table 7.1): 300,368 in 2018 for all scenarios, 343,114 in 2022 and 384,500 in 2042 for

scenarios A and B, and 368,623 in 2022 and 568,363 for scenarios C and D.

8.4.2 Investment scenarios

8.4.2.1 Infrastructure

As a no-regret measure that can be implemented with relative ease, the existing sewerage

system of PDAM Tirtanadi in Parapat (one of the tourism areas) should be rehabilitated.

The wastewater treatment plant (WWTP) uses a conventional system consisting of

aeration ponds, facultative ponds and maturation ponds, all equipped with aerators. Since

land availability is an issue, one feasible option would be to upgrade the treatment process

at the WWTP, making it more efficient with a lower foot-print.

For the medium (until 2022) and longer term (until 2042) three scenarios are considered.

The intermediate one is the implementation of the national policy (USDP, 2015)27. The

high scenario targets an accelerated implementation of this plan, aiming for 100%

coverage in 2022 instead of 2042. It envisages additional facilities for the core tourist areas

at the southern and eastern shores of Lake Toba (section 7.3.3). These areas have higher

population densities and the sanitation services switch from community-based to off-site

wastewater treatment. The low scenario assumes a slower speed of implementation,

taking into account the lengthy processes to release sufficient funds. Table 8.1 provides

an overview of the percentages of access to various facilities over time in the different

scenarios.

In terms of tourism, the baseline and low scenario apply the number of visitors in the

‘business as usual’ projection (Table 7.1). The intermediate scenario is based on the ‘best

case’ number of visitors, but does not foresee additional infrastructure. The high scenario

uses the ‘best case’ projection with additional treatment facilities.

In the low and intermediate scenario, the national targets and type selection (Table 8.9)

applied to the Lake Toba catchment results in a focus on community based systems

(Sanimas) as well as individual septic tanks for rural areas (City Wide Sanitation

Investment Program, 2016). In urban areas off-site systems (Kawasan/Pusat) are applied;

only 5%-10% of the population will be on such systems by 2042. The majority of domestic

wastewater will not have advanced treatment (no nutrient removal). Under the low

scenario, a large part of direct cost is allocated to the users/community (30%), resulting in

a slower speed of implementation.

27 The original budget in the ADB study turned out to under-estimate the costs of off-site sanitation; in the

investment scenarios presented here, this bas been corrected.



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Table 8.9, Selection criteria for type of sanitation services (see also Table M.1).

Population density

(pp/ha) <25 25-100 100-175 175-250 >250

Urban function

(BPS, RTRW) no yes no yes no yes no yes no yes

On-site

1

Community based

2

Off-site (centralized)

Kawasan

1

2

Terpusat

3

Notes:

1 Existing areas, consider on-site systems; for new areas IPAL kawasan to be considered;

2 For very high dense rural areas both IPAL communal and kawasan could be considered;

3 There is no clear separation between IPAL kawasan and terpusat; off-site typically involves systems of >

10,000 HH;

4 Rural population <25 pp/ha not served by IPLT until 2022.

In the high scenario the application of higher targets and off-site systems for tourist areas

on Lake Toba catchment results in a shift from community based systems (Sanimas) to

off-site (IPAL Kawasan). There is only a small reduction in individual septic tanks. Half of

the population will be on off-site systems by 2042; half of domestic wastewater will have

advanced treatment (incl. nutrient removal). Compared to the other scenarios, the

accelerated approach and choice for more centralized systems results in a major increase

in the total cost. This is coupled with a major decrease in direct cost to users in the

community (~0.4x) compared to the base scenario. More details on the funding

mechanisms for wastewater interventions can be found in Annex M.


While the recommendations for wastewater management are based on national policies

for sanitation, the implementation requires institutional support as well (USDP, 2015). For

the Lake Toba area, it needs to be clear who is responsible for catchment-wide sanitation

services. Figure 8.8 shows the steps and activities to arrive sustainable sanitation services

in priority areas. For more details on the institutional aspects, see Annex M.4 that is largely

based on the City-Wide Sanitation Investment Program (2016).


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Figure 8.8, Sanitation implementation schedule (based on City Wide Sanitation Investment Program,

2016).

Local government has an important role to play in the planning, funding and operation of

improved wastewater management facilities. An incentive program could support the local

government to align a faecal sludge management program with improving on-site

sanitation. This would need to be supported by local and national funding for priority

measures that directly increase levels of access to improved waste water management

(no-regret measures). Subsidies will be needed to cover the gap between what households

can pay and the actual costs, particularly for low income and disadvantaged households.

Sewerage systems with wastewater treatment plants are under the responsibility of PDAM

Tirtanadi i.e. the wastewater section. Figure 8.9 shows the institional arrangements

required for wastewater interventions at Parapat. This encompasses the entire supply

chain to enhance sustainability beyond the construction phase. Similar diagrams display

the potential arrangements for other wastewater management options in Annex M.2.

Communal systems, typically shallow sewers with primary treatment plants, are managed

by the community. For the on-site system, the septic tank is owned by each household

while the sludge treatment plant (IPLT) is under the responsibility of the local government.

Costs of sludge collection are included in the operational costs of the on-site and

community-based systems.



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Figure 8.9, Supply chain for best wastewater investment scenarios at Parapat (after Tilley et al. 2008).

8.4.2.3 Information

In most areas wastewater is under the responsibility of the local Public Works Agency

(Dinas PU). However, if sustainability of the system has to be ensured, other agencies

need to be involved, such as the Health Agency (Dinas Kesehatan) for advocacy and

campaigns, Communication and Information Agency (Dinas Kominfo) for advocacy and

campaigns, local Government Planning Board (Bappeda) for preparing the program and

budget allocation, and PDAM or another agency for the operation of the system. Realizing

that coordination between agencies is important, under the National Accelerated

Sanitation Development for Human Settlements Program (PPSP) a pre-requisite condition

for the municipalities to be involved in the program is that they have to establish a City

Sanitation Working Group. To make the working group effective, the Ministry of Home

Affairs has released guidance that the working group shall be chaired by the Municipal

Secretary. The kabupaten have been involved in the PPSP program. Therefore to make

the program effective the City Sanitation Working Group should be re-activated to prepare

an action program to support Lake Toba water quality improvement.


An analysis was carried out to determine the investment (CAPEX) and operational costs

(OPEX) for wastewater collection and treatment facilities. A distinction is made between

investment figures for existing and new developing areas. In this assessment, the costs

for sewer systems for new areas are expected to be reduced by 50%28 compared to the

investments in an existing area. The cost for the wastewater treatment plant (WWTP) itself

is expected to be the same either way. In Annex M.2 the complete needs assessments

according to low, intermediate and high investment scenarios are elaborated. The costs

presented in Table 8.10 are total costs based on unit cost per person over five years.

However, these cost need to be covered from different sources. These budgets need to

come from both private and public sources (City Wide Sanitation Investment Program,

2016). And the public sources can be subdivided into national and local levels as well as

by department (i.e Public Works and Ministry of Health. More on this can be found in Annex

28 Based on data of the Dutch situation it is found that more than half of the costs of the sewer system in existing

areas are related to the opening and closing of existing roads and pavements. In new developments, the

opening up of the streets is not needed and the construction of pavement is considered part of the general

development, so a 50% factor for sewer system development is applied.

User

InterfaceStorage / Primary Treatment

Transportation /

Conveyance

Centralized

TreatmentRecycle / Disposal

Recycled

sludge

Effluent to

river / lake

WC / Toilet Sewer line WWTP

Items

Infrastructure

Finance CustomerProvince /

Central GovCentral Gov.

Regulation Obligation to connect & fee

PDAM TirtanadiInstitutionEnv agency to

monitor

Customer for house connection

LG for branch sewer


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M. The cost includes capital expenses for hardware (i.e. physical measures) and

operational expenses for software (ranging from e.g. advocacy and socialization to the

collection of sludge from septic tanks).


domestic wastewater (including tourism) into Lake Toba, in a low scenario B, an intermediate and a

high scenario D. Table 8.11 shows the percentages access to each type of facility and the tourism

numbers for each scenario.

B. Low C. Intermediate D. High

CAPEX29 OPEX30 CAPEX OPEX CAPEX OPEX responsibility

Infrastructure

On-site systems 86,000 66,215 203,000 75,434 219,000 76,652 users/community,

National & Local

government Community-

based systems

474,000 22,965 848,000 41,097 349,000 16,914

IPLT 76,000 ^ 103,000

102,000 ^ National & Local

government

Medium

centralized

95,000 10,925 236,000 18,655 3,693,000 240,932 National & Local

government

Institutional and information are included in OPEX

Subtotal 731,000 100,105 1,390,00

0

135,185 4,363,000 334,498

Reserved 730,472 100,105 730,472 100,105 730,472 100,105

Extra

investment

required (106

IDR)

528 0 659,528 35,081 3,632,528 234,393

Total (million

IDR)

529 694,610 3,866,922

US$ equivalent

(000, split)

39 0 48,872 2,600 269,176 17,369

US$ equivalent

(000, total)

39 51,472 286,545

8.4.3 Impact on nutrients

For calculation of the emissions, it should be considered that many of the urban on-site

systems do not comply with the definition of a septic tank and are more like pit latrines.

The result is that there is still a lot of leakage of polluted water to the groundwater. Hence,

the effective reduction of on-site sanitation facilities (septic tanks as well as community-

based systems) is only 5%. Off-site centralized systems are more effective and are

assumed to remove 67% of nutrients (based on Kerstens et al. 2015). The resulting

percentages nutrient reduction for the three scenarios are presented in Table 8.11.

29 CAPEX = Capital Expenses. 30 OPEX = Operational Expenses, running costs; total fore five years.



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Table 8.11, Access to sanitation facilities, assumed numbers of tourists, and effective reduction of nutrient

loads from domestic wastewater according to four scenarios. See section 8.1 for more details. Scenario A

Baseline

Scenario B

Low

Scenario C

Intermediate

Scenario D

High

2018

On-site

Centralized

Peak number of

tourists

Total reduction

0%

0%

300,368

0%

0%

0%

300,368

0%

0%

0%

300,368

0%

0%

0%

300,368

0%

2022

On-site

Centralized

Peak number of

tourists

Total reduction

0%

0%

343,114

0%

66%

1%

343,114

4%

85%

2%

368,623

6%

69%

31%

368,623

24%

2042

On-site

Centralized

Peak number of

tourists

Total reduction

0%

0%

384,500

0%

94%

6%

384,500

9%

94%

6%

368,623

9%

50%

50%

368,623

36%

The effects of measures to reduce sewage flows from domestic areas and tourism are

relatively small, see Figure 8.10. The majority of the population live in non-urban areas

and will continue to be connected to septic tanks. Even under high scenario D this will still

be 50%. These on-site systems have limited effect on phosphorous and nitrogen

emissions. However, locally these effects could be higher. Under the high scenario D a

higher percentage of the population will be connected to centralized sewer-based systems.

These are more effective in reducing nutrient emissions and thus more than compensate

for population growth. As a result, nutrient loads under this scenario reach levels below

those of 2018.

Figure 8.10, Projected impacts of three intervention scenarios and a comparison scenario (A) on loads from

domestic wastewater and resulting long-term concentrations of nitrogen (left) and phosphorous (right)

for the whole of Lake Toba.


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result from the load in a certain year, if wastewater from domestic areas and tourism would

be the only source of nitrogen and phosphorous. The displayed concentrations thus

represent equilibrium concentrations on the basis of input data for 2018, 2022 and 2042.

It may take tens of years to achieve each of these equilibrium states (Figure 7.13) and in

reality additional sources will add to the load (section 0).

Figure 8.11 shows the nitrogen and phosphorous loads and long-term concentration under

four scenarios applied to the best zonation in four compartments. The graphs show loads

and concentrations by compartment at fixed scales to enable comparisons between

compartments. The phosphorous limit for oligotrophic state has been indicated at 10 μg/l

(based on Nürnberg, 1996; Table C.2 in Annex C.3). For nitrogen, the resulting

concentrations stay well below the limit of 350 μg/l for an oligotrophic state in all

compartments in all scenarios.

The graphs show increasing loads from population growth in all scenarios except the high

investment scenario D. Based on loads from domestic wastewater alone, long-term

phosphorous concentrations do not go beyond the oligotrophic limit of 10 μg/l, in the large

compartments North and S2. In the small compartment S1 even under the high investment

scenario D, concentrations would reach mesotrophic levels. In compartment S3 the high

investment scenario would manage to keep the long-term concentratioms below 10 μg/l.



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Figure 8.11, Projected impacts of three intervention scenarios and a comparison scenario on loads from

domestic wastewater and resulting long-term concentrations of nitrogen (left) and phosphorous (right)

across four compartments North, S1, S2, and S3 of Lake Toba.


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8.5 Other interventions

In the sections below, additional interventions are presented that would reduce the nutrient

load in Lake Toba. However, as these were not main drivers of water quality (together

contributing less than 2% of total phosphorous loads), their impact on improving water

quality in Lake Toba is negligible. However, their impacts on, for instance, rural

development or tourism justify inclusion in this report. Roads, hydropower and telecom are

excluded from the report. Improvements in domestic water supply may increase

wastewater flows, but this has no impact on wastewater investments as these depend on

population numbers.

Moreover, as investors are waiting to develop infrastructure around Lake Toba (section

2.1.4), these new investments all need guidance to ensure that water quality is not further

threatened. BWS Sumatera II has positively advised DLH-SU to start collaboration and

build commitment on protection of water quality with the eight district governments around

Lake Toba. In this way, all related agencies, including the police, NGOs and the media,

could be mobilized.

8.5.1 Pollution in agriculture

Pollution from rice fields and other crops may come from synthetic pesticide and fertilizer.

One way of reducing this pollution is through organic farming. As with livestock

management, organic farming could be promoted via pilot projects. New farming practices

require capacity building at local level (training). In parallel, supply chains and marketing

of the products must be secured. Recommendations on upscaling of organic horticulture

via training and market development have been included among the livelihood options

presented as alternatives to aquaculture (section 8.2.1).

Several foundations can support the pilot including providing training for interested

farmers. The existence of old small local organizations such as Water User Associations

(WUA) are eager to support better agricultural farming practices and irrigation (especially

better use of fertilizer and pesticide or transition to organic farming).

8.5.2 Solid waste management

8.5.2.1 Approach and background

At the moment, solid waste might not contribute much to the water quality degradation of

Lake Toba and therefore the impacts have not been modelled. However, this may be

different in the future with more people. Moreover, as with wastewater, aspects such as

health, well-being and environmental amenities make it necessary to address proper

disposal of solid waste—in particular in the light of tourism development.

As with (domestic) wastewater, the National Accelerated Sanitation Development for

Human Settlements Program (PPSP-2 USDP; USDP, 2015) prepared an assessment of

the country-wide solid waste funding and facilities required in the period of 2015-2019 (and

beyond) for the National Medium-Term Development Plan 2015-2019 (RPJMN 2015-



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135

2019). The database that was developed for this assessment was adapted (scaled down)

to the Lake Toba catchment area and updated with population figures and developments

according to the Sumatra Spatial Model, with separate inputs for tourism. This means that

investments are calculated for the catchment population only. However, solid waste

intervention, especially treatment in landfills, is generally organised at a higher

administrative level, in which several kecamatans can make use of one landfill and

collection trucks can service several desa or keluhuran. Therefore, the interventions have

been assessed at a somewhat higher level than for wastewater management. As a result,

the solid waste interventions are clustered and individual measures cannot be directly

assigned to individual desa or keluhuran. Furthermore, in practice most solid waste

interventions will also service nearby non-catchment population. However, any additional

cost required is not included in this assessment. More details on solid waste and its

management can be found in Annex N.1.

8.5.2.2 Investment scenarios

For solid waste three scenarios are considered; 1) an intermediate scenario that follows the national policy, 2) a low scenario that envisages a more realistic, slower, rate of implementation, and 3) an accelerated scenario that reaches 100% coverage by 2022. Table 8.12 shows for each of the scenarios the access to domestic waste collection and disposal or 3R facilities. The next table, Table 8.12, presents the investment costs for the three scenarios. For the current situation that is mainly characterized by informal collection, zero coverage is assumed.

Table 8.12, Access to solid waste disposal facilities and services according to four scenarios. Scenario A

Baseline

Scenario B

Low

Scenario C

Intermediate

Scenario D

High

2018

Final disposal and

3R facilities

Collection activities

0%

0%

0%

0%

0%

0%

0%

0%

2022

Final disposal and

3R facilities


0%

0%

10%

11%

12%

12%

100%

100%

2042

Final disposal and

3R facilities


0%

0%

95%

93%

95%

93%

100%

100%

Improvements could be made with commitment from regional leaders, aiming at improving

solid waste management to support tourism in Lake Toba. The province could lead the

development of a regional waste management program, together with the seven districts

directly draining into the lake.


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solid domestic waste (including tourism) into Lake Toba, in low, intermediate and high investment

scenarios.


CAPEX OPEX* CAPEX OPEX* CAPEX OPEX

Infrastructure

Final disposal and

3R facilities 106,000 18,112 120,000 20,696 295,000 135,756

Collection activities 5,000 62,915 8,000 71,271 113,000 472,554

Institutional,

information

(included in OPEX)

Subtotal 111,000 81,027 128,000 91,967 408,000 608,310

Reserved 111 81,025

111 81,025 111 81,025

Extra investment

required (million

IDR) 110,889 2 127,889 10,942 407,889 527,285

Total (million IDR) 110,891 138,831 935,174

US$ equivalent

(000, split) 8,217,025 141 9,476,751 810,811 30,225,176

39,072,61

2

US$ equivalent

(000, total) 8,217,166 10,287,562 69,297,788

8.5.3 Erosion reduction

8.5.3.1 Background

Lake Toba’s water quality has been decreasing because of changing land use patterns.

Conversion of forest cover, with associated illegal logging and fires, is an unsustainable

practice. In addition, Toba stream water and surface runoff have stimulated algal growth.

Erosion control, forest rehabilitation, and better land-use management are therefore critical

to maintain the health of Lake Toba. The Save Indonesian Lake Movement (‘Germadan’)

in 2009 for Lake Toba attempts to review all the regulations related to Lake Toba and

analyses the gaps in the overall management of Lake Toba, including its surroundings

(section 3.4). The Ministry of Environment and Forestry, together with the Provincial Forest

Service, is now implementing a reforestation program. More details on erosion reduction

can be found in Annex N.2.

8.5.3.2 Investment scenarios

Several interventions would reduce erosion in Lake Toba’s catchment area. Below various suggestions are made, some of which would have optimal effects, while others can be considered the bare minimum. In Table 8.14 these are summarised with approximate costs and an indication of total budget for each of the two scenarios.



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Natural infrastructure approaches can mitigate and prevent further damage in watersheds.

In addition to conducting natural restoration, building several simple structures can go a

long way in the effort to reduce erosion. Examples of these are containment dam and gully

plugs in the upper watershed, controller dam and terraces in the central part of the

watershed, and infiltration wells in the lower watershed. Such structures could help prevent

natural disasters (floods and landslides) and protect vital buildings located downstream.

Another way of reducing erosion is by introducing more trees in the landscape through

social forestry and agroforestry. In support of this, agro-industry and agro-tourism could

be introduced with strong community involvement, encompassing all parts of the value-

chain. This will help to improve people’s livelihoods while reducing the extent of critical and

degraded lands. Support from agricultural extension services is required to encourage

local communities to adopt best planting practices and avoid detrimental impacts of

fertilizers and business-as-usual planting practices. This can help a transition towards

more sustainable agriculture that has the potential to halt and even reverse erosion instead

of causing it. Such processes require the further strengthening of both the regulations and

institutional aspects of restoration.

Monitoring can be strengthened by applying the free global database and interactive

mapping tool of Global Forest Watch Water (GFW Water). This tool can help stakeholders

to apply natural infrastructure as one of their strategies to enhance water security and

improve watershed management.

Table 8.14, Summary of measures for erosion control and total costs of two different scenarios.

Measure Costs

Best

scenario

Minimal

scenario

Infrastructure

a. Natural infrastructure

(reforestation)

1,150

US$/ha

x

b. Erosion control structures x

c. Restoration of degraded lands x

Institutional

d. Develop agro-industry and agro-

tourism

x

e. Promote best planting practices 859 US$/ha

f. Strengthen regulations and

institutional aspects

x

Information

g. Adapt GFW Water x

h. Monitor land-use conversion x


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8.6 Cumulative impact of scenarios

8.6.1 Four scenarios

The potential impact of the scenarios has been elaborated for the main sources

aquaculture, livestock and domestic wastewater in the sectios above. This section

evaluates the cumulative impact of the four combined scenarios on nutrient loads and

long-term concentrations. The scenarios are summarized in Table 8.1, while Figure 8.1

gives an overview of the four compartments.

The nutrient loads and concentrations resulting from the four combined scenarios are

presented in the following figures for the whole lake and four compartments. The displayed

concentrations represent equilibrium concentrations on the basis of input data for 2018,

2022 and 2042. It may take tens of years to achieve each of these equilibrium states

(Figure 7.13). Limits for oligotrophic and mesotrophic state have been indicated for

phosphorous at 10 and 30 μg/l respectively, and for nitrogen the 350 μg/l oligotrophic limit

is displayed (based on Nürnberg, 1996; Table C.2 in Annex C.3). Figure 8.12 shows the

results for the whole lake, Figure 8.13 for the northern compartment, Figure 8.14 for the

southern compartment S1, Figure 8.15 for the southern compartment S2, and Figure 8.16

for the southern compartment S3. The graphs show loads and concentrations by

compartment at fixed scales to enable comparisons between compartments.



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Figure 8.12, Projected impacts of four intervention scenarios (summarized in Table 8.1) on total loads and resulting long-term concentrations of nitrogen (left) and phosphorous

(right) for the whole of Lake Toba.


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(right) in the northern compartment (according to Figure 8.1) of Lake Toba.



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(right) in the southern compartment S1 (according to Figure 8.1) of Lake Toba.


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Without any interventions (scenarios A and B), nutrient concentrations will continue to rise,

leading to a long-term eutrophic state in the northern and southern compartment S1 for

phosphate and mesotrophic for nitrogen. The southern compartments S2 an S3 would remain

mesotrophic for phosphorous and oligotrophic for nitrogen. Substantial reductions in nutrient

loads, concentrations and trophic state can only be achieved in the two scenarios with reduction

of aquaculture: the intermediate C and high D scenarios.

For nitrogen (N), compartments S2 and S3 would remain oligotrophic in all scenarios. In the

northern compartment, increased loads under scenarios A and B would result in long-term

concentrations above the oligotrophic limit of 350 µg/l. This is mainly because of the loads from

aquaculture (Table 8.6 and Figure 8.5). In the smallest southern compartment S1, only scenario

D would lead to long-term concentrations below the limit for oligotrophic state, and scenario C

in 2042, with a maximum aquaculture production of 10,000 tons/year.

For phosphorous, the situation is different. For the lake as a whole, none of the scenarios would

eventually lead to an oligotrophic state. However, the effects differ significantly across the

compartments. In southern compartments S2 and S3, phosphorous loads from 2022 onwards

in scenario D would eventually bring the total phosphorous concentrations from a mesotrophic

level down to just below the oligotrophic limit of 10 µg/l. This means that if scenario D is

adopted, eventually oligotrophic water will flow out from compartment S3 into the Asahan River

to downstream users. Concentrations in the northern compartment N would slowly go down

below the limit for a mesotrophic state, based on the loads in 2022 and 2042 in scenarios C,

and all years in scenario D.

Compartment S1 is the smallest and also the most problematic in terms of water quality.

Because of the intensive use with high population densities and livestock, the loads lead to very

high long-term concentrations. In scenario C and D aquaculture is halted completely, but loads

from livestock and wastewater each bring the long-term phosphorous concentration to levels

above the oligotrophic limit of 10 µg/l (Figure 8.7 and Figure 8.11). Combined, these loads lead

to a long-term mesotrophic state for phosphorous, even under scenarios C and D.

Only when mitigating measures in all sources: aquaculture, livestock and domestic loads are

applied, under the high scenario D, can the oligotrophic limit eventually be reached in

compartments S2 and S3. For the lake as a whole and in the northern compartment, the

mesotrophic limit will be feasible. For compartment S1 additional measures will be needed.

8.6.2 Alternative scenario

Interventions in aquaculture and livestock manure management have high impacts on nutrients for relatively low investment costs when compared to wastewater management. Investments in sanitation facilities are expensive and have limited impacts on nutrient loads and resulting long-term concentrations. An alternative scenario E combines high investments in aquaculture and livestock manure management with an intermediate level of investment in wastewater (Table 8.15).



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Table 8.15, Three scenarios to reduce nutrient loads into Lake Toba.

Driver Scenario C

Intermediate

Scenario D

High

Scenario E

Alternative

Aquaculture

Gradual reduction of

production


production


production

2018

2022

2042

64,000 tons, FRC 1.9

50,000 tons, FCR 1.9

10,000 tons, FCR 1.9

64,000 tons, FRC 1.2

10,000 tons, FCR 1.2

10,000 tons, FCR 1.2

64,000 tons, FRC 1.2

10,000 tons, FCR 1.2

10,000 tons, FCR 1.2

Livestock Conversion of manure into biogas

2018

2022

2042

1% conversion

20% conversion

40% conversion

5% conversion

30% conversion

60% conversion

5% conversion

30% conversion

60% conversion

Wastewater

Implementation as

planned

Accelerated

implementation

Implementation as

planned

2018

2022

2042

On-site: 50%



On-site: 50%

On-site: 69%, Central:

31%

On-site: 50%, Central:

50%

On-site: 50%



Tourists

per year

Best case Best case Best case

2018

2022

2042

1,802,200

2,212,000

3,410,300

1,802,200

2,212,000

3,410,300

1,802,200

2,212,000

3,410,300

The impacts of the alternative scenario E on the total phosphorous and nitrogen loads are

compared to the intermediate scenario C and high scenario D in Figure 8.17. Subsequently,

the nutrient loads and concentrations resulting from these three scenarios in the four

compartments are presented in Figure 8.18. These graphs show loads and concentrations by

compartment at different scales to enable a closer look and comparison between scenarios in

each compartment. The displayed concentrations represent equilibrium concentrations on the

basis of input data for 2018, 2022 and 2042. It may take tens of years to achieve each of these

equilibrium states (Figure 7.13). Limits for oligotrophic and mesotrophic state have been

indicated for phosphorous at 10 and 30 μg/l respectively, and for nitrogen the 350 μg/l

oligotrophic limit is displayed (based on Nürnberg, 1996; Table C.2 in Annex C.3).

Figure 8.17 shows how the loads of aquaculture (in blue) and livestock (in red) in the alternative scenario E are similar to those in the high scenario D, while domestic wastewater (in green) is relatively higher, as in intermediate scenario C. In Figure 8.18 the resulting long-term concentrations of the alternative scenario E stay close to those of high scenario D, except for compartment S3, and for nitrogen also in S1. Compartment S3 is the only place where the alternative scenario E leads to long-term phosphorous concentrations that would change the eventual end-state, from oligotrophic to mesotrophic.


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Figure 8.17, Nutrient loads of total nitrogen (top) and total phosphorous (bottom) resulting from three different

scenarios to reduce nutrient emissions from aquaculture, livestock manure and wastewater, in Lake Toba as

a whole.



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Figure 8.18, Projected impacts of three intervention scenarios (summarized in Table 8.15) on total loads and

resulting long-term concentrations of nitrogen (left) and phosphorous (right) across four compartments

North, S1, S2, and S3 of Lake Toba.



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9 Response: water quality monitoring

9.1 Three pillars

The design of effective monitoring programs is based on three pillars that are of equal weight

(Buijse and Noordhuis, 2012; Figure 9.1). These are the following:

1. System knowledge. The workings of the lake ecosystem dictate what, where and when

monitoring should take place. Also, the system links connected to the issue(s) that prompt

the monitoring, such as eutrophication, determine what should be monitored.

2. Needs: the focus or the management decision (for which the data provides the basis).

The issues (impacts in terms of DIPSR) at hand or the policy questions are the second

determinant for the focus of the monitoring program. For example, the focus can be to only

receive a ‘signal’ when something is wrong in the system. The focus can be to monitor

progress of implemented policies. Alternatively, the focus can be to gain system knowledge.

All these examples of focus lead to different monitoring programs with different monitoring

intensities.

3. Technical monitoring possibilities. The available monitoring technology determines

what can be measured, at what level of accuracy and at what costs.

Figure 9.1, The three pillars needed to formulate a monitoring plan (source: Deltares).

These three pillars need to be defined clearly and in multi-stakeholder processes by all relevant

stakeholders, before all aspects of the monitoring plan can be defined and elaborated.


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9.1.1 System knowledge

As an example of the system knowledge needed for Lake Toba, the process of eutrophication

is crucial. In the simple causal diagram in Figure 9.2, the causes and effects of eutrophication

are shown. Based on this diagram, it is relatively easy to pick crucial parameters to monitor

eutrophication. First, changes in the concentration of nutrients and primary producers seem the

most important (central) parameters for the signal function. Secondly, in case people want to

predict potential problems, the monitoring of the causes and effects will provide insight under

what circumstances the (negative) effects will occur. Clearly, the second objective will lead to

more parameters to monitor. For monitoring purposes, all relevant stakeholders, both outside

and within organizations should have the same understanding of the ecosystem functioning.

Making a causal diagram is crucial to identify and agree on important monitoring parameters.

Figure 9.2, The causal diagram of eutrophication (source: Chapman, 1996).

The external link in the cause and effect figure links the lake system to its surrounding catchment. Therefore, in addition to the conceptual knowledge model of the lake system, a



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conceptual model on the catchment scale is also crucial to determine monitoring needs and most importantly, a common understanding and consensus among the stakeholders as to why certain system and monitoring aspects are important. In Figure 9.3 a conceptual model of a catchment system is given.

Figure 9.3, Conceptual model of a catchment (Lehr et al., 2005). A similar model can be made for the Lake Toba

catchment to underpin the monitoring choices made.

9.1.2 Information needs

The analysis in this report, as part of the water quality roadmap for Lake Toba, focused on

phosphate, and to a lesser extent nitrogen, as main determinants of eutrophication. Other

parameters may be relevant in this process as well, such as Biochemical Oxygen Demand

(BOD). Moreover, other water quality issues might play a role at Lake Toba, with potentially

important local impacts on, for instance, the aquatic ecosystem and even human health, such

as inorganic compounds, pesticides and pathogens. These would need to be considered as

well in an overall monitoring plan.

PJT1 recently measured increased values for BOD and COD between May 2016 and July 2017

at several locations (Table G.1). These results, together with the measured decrease in

dissolved oxygen indicate that the quality of Lake Toba’s water has further decreased. In a

future monitoring program, sampling points should be added close to the pollutant sources to

better understand the nature, extent, and potential degradation of the pollutant loads into Lake

Toba. This will make it easier for stakeholders to analyze the various causes of decreasing

water quality in Lake Toba.

To improve understandings about Lake Toba’s system, better meteorological data are required.

The meteorological station at Medan airport is 80 km North of Lake Toba whereas the mountain

range and the ridge of the caldera shield the lake from direct influence of wind. Therefore, two

on-lake meteorological stations preferably with on-line internet connection, one in the central

basin north and the other in the central basin south of Samonsir peninsula would greatly reduce

the uncertainty on the physical conditions and analyses of events such as shown in Figure 6.20.


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The hydrology and water balance of Lake Toba may at least hint at potential water sources

explaining the lake’s cooler deep water. To improve the hydrothermal analysis (especially with

respect to upwelling events) more information on these sources may be required.

Furthermore, the observation of dissolved gases, such as CO2 and CH4 and their sources, is

recommended as these gases may be introduced through ground water flows in this region

with active volcanoes as well as by bacterial fermentation. Possibly this may be enhanced by

more recent wastewater discharges into the lake and possibly unused fish food as well. In case

of high concentrations of dissolved CO2 this gas may reduce the lake’s stability, such as with

turn over events, as in Lake Nyos in Cameroon, WestAfrica, whereas CH4 would enhance its

stability.

Development of a dynamic model as a long-term goal would ensure good and consistent monitoring. This would need to be combined with a clear definition of the parameters that need to be monitored.

9.1.3 Technical capabilities

The institutes currently involved in water quality monitoring (see section 3.3), each have a role

to play in a future monitoring plan for Lake Toba, based on its mandate, technical capabilities

and financial possibilities.

• DLH-SU (22 sampling sites) is specialised in the signal function, general monitoring of

long term trends in lake status, with a focus on parameters near the shore.

• LIPI is specialised in exploratory and scientific monitoring, aimed at understanding the

lake’s functioning. Its 12 sampling locations are all in the middle in the lake, including

depth profiles, to further develop their 3D hydro-dynamic model.

• PJT1 is in a unique situation because of its mandate supported by Presidential Decree

2/2014, of being able to collect revenues for lake management. This supports their

financial ability to sustain a monitoring program. Its plans to construct a water quality

laboratory near Parapat are in an advanced stage and additional funding is sought to

accelerate the development process. They now have 20 sampling locations for water

quality monitoring, including one in a non-polluted area, as a reference point (Figure 3.4).

• PT Aquafarm Nusantara (PTAN) offers additional sampling sites near the major fish

farms.

A more detailed inventory of the technical capabilities and limitations of these main water quality

monitoring institutions and identifying comparative advantages of each, are among the first

activities of the monitoring working group (section 9.2). These are necessary first steps towards

combining the sampling sites into one comprehenvsive sampling and monitoring plan and

program.

9.1.4 Incorproating remote sensing capabilities

Remote sensing has been shown to be a powerful, feasible and relatively low-cost tool,

complementing in-situ water sampling, as part of comprehensive water quality monitoring.

Remote sensing data, for the most part, are open and free. However, the processing chain

requires development and periodic validation with ground reference data to get an accurate

representation of biogeochemical dynamics. Remote sensing enables unique insights into

spatial and temporal dynamics, but challenging atmospheric conditions in the tropics require



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maximizing satellite overpass coverage, thus combining several multispectral sensing

platforms is required to achieve an optimal result, i.e., (i) high-resolution (e.g. Sentinel-2A/2B,

Landsat-8); (ii) moderate-resolution (e.g. MERIS, S3A OLCI); and (iii) low-resolution

geostationary (e.g. Himawari-8).

Using high-resolution sensors like Sentinel-2 / Landsat-8, the revisit frequency will more than

double to less than a 5 day revisit (from ~10 days) due to Sentinel-2B data ramp-up by year-

end 2017. With this, and assuming atmospheric conditions similar to the last several years,

more than 5 to 8 cloud-free images per year can be expected.

In addition, Sentinel-3A, Sentinel-3B launches are scheduled for Q1 2018 with daily Ocean and

Land Color Instrument (OLCI) revisits. Also, five multi-spectral sensors will soon be online for

enhanced temporal coverage of Lake Toba, as follows: • 3 High spatial-resolution (Sentinel-2A + 2B, Landsat-8), enabling to fingerprint lake

surface and water-quality dynamics on a monthly to seasonal basis • 2 Moderate-resolution (S3A OLCI + S3B planned 2018), with daily to weekly dynamics

and long term continuity, multi-year / decadal monitoring (MERIS time-series).

Further optimization of the constant-threshold (CTR) filtering or masking of data based on

SWIR/NIR bands is needed to remove atmospheric (haze/clouds/marine layer) and optical

artifacts (glint), and to improve quality and quantity of valid pixels.

Benefits of higher remote sensing data sampling rates from lower-resolution sensors, such as

ESA MERIS, were demonstrated to overcome atmospherically-clear pixel availability and

generate high-value product maps and movies. Integration of these instruments (NASA

Aqua/Terra MODIS and ESA Sentinel-3A/3B OLCI) would be key part of comprehensive

monitoring strategy going forward.

9.1.5 Requirements

It is recommended to start by designing a monitoring program without taking the costs into

account. After the “ideal” monitoring program (for the predetermined focus) is composed, it can

be optimised for minimum costs and maximum benefits. Only in this order will it become clear

what cutting costs means for the results of the monitoring program. Sometimes cutting costs

without taking into account each of the three pillars can result in an ineffective or even useless

program.

In case the monitoring program is carried out in collaboration by multiple partner organizations,

the development and reasoning behind the monitoring program should be clear for all partners.

Preferably, the program is developed in a collaborative stakeholder process to make sure all

the perspectives are included, and changes that are made during the program will not affect

the overall anticipated result.

A central data storage and retrieval system is required to ensure availability of the data, and

consistency across time and stakeholders to make sure they base their analysis and decisions

on the same data. It is important to involve the future users and monitoring stakeholders at an

early stage. Likewise, the identification of a dedicated organization that will host the data

storage system is crucial, so that agreements on data ownership and access can be made

clear to all stakeholders from the beginning.


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9.1.6 Data collection: Common sources of error Chapman (1996) lists common sources of error and appropriate actions in water quality assessment. His table is provided here as practical checklist for monitoring studies (Table 9.1). The International Organization for Standardization (ISO) sets more elaborate standards for water quality monitoring, including sampling procedures and laboratory analyses in ISO standard 5667, parts 1 to 24, and for water quality laboratories in ISO standard 17025 (www.iso.org). Basically, most of the errors can be overcome by setting up standard field and laboratory protocols for monitoring. When contracting sub-contractors for the monitoring, these standard protocols should be included in the Terms of Reference. Important recommendations following from this table are summarised in the next paragraph.

Table 9.1, Some possible sources of errors in the water quality assessment process with special reference to

chemical methods (adapted from Chapman, 1996). For more details on ISO 5667 and ISO 17025, see

www.iso.org.

Assessment step Operation Possible source of error Appropriate actions

Monitoring design Site selection Station not representative (e.g. poor mixing in rivers)

Preliminary surveys

Frequency determination

Sample not representative (e.g. unexpected cycles or variations between samples)

Field operations Sampling Sample contamination (micropollutant monitoring)

Decontamination of sampling equipment, containers, preservatives

Filtration Contamination or loss Running field blanks

Field measurement Uncalibrated operations (pH, conduct., temperature)

Field calibrations, Replicate sampling

Inadequate understanding of hydrological regime

Hydrological survey

Sample shipments to laboratory

Sample conservation and identification

Error in chemical conservation

Field spiking

Lack of cooling Appropriate field pretreatment

Error in biological conservation

Error and loss of label Field operator training

Break of container

Laboratory Pre-concentration Contamination or loss Decontamination of laboratory equipment and facilities

Analysis Contamination Quality control of laboratory air, equipment and distilled water



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Assessment step Operation Possible source of error Appropriate actions

Lack of sensitivity Quality assurance tests (analysis of control sample; analysis of standards)

Lack of calibration

Error in data report Check internal consistency of data (e.g. with adjacent sample, ionic balance)

Computer facility Data entry and retrieval

Error in data handling Checks by data interpretation team

Interpretation Data interpretation Lack of basic knowledge Appropriate training of scientists

Ignorance of appropriate statistical methods

Omission in data report

Publication Data publication Lack of communication and dissemination of results to authorities, the public, scientists.

Setting of goals and training to meet the need of decision makers

9.2 Monitoring working group

The primary recommendation is to start with selecting a monitoring working group based on

stakeholders who already are involved in monitoring and/or heavily depend on monitoring water

quality data. Devising such a plan should take no more than 6 months. The plan may be revised

when additional information needs, monitoring techniques, or new system aspects arise that

require adaptation of the monitoring effort. The investments needed to set up an integrated

water quality monitoring plan are detailed in Table 9.2 for a minimal scenario. The costs are

expert opinions based on personnel, commercial laboratory analyses and equipment costs.

Staff time of local experts is set at a flat daily rate of US$ 200. Laboratory costs combine capital

and operational expenses into unit prices as per common practice for water analyses. As a first

step towards implementation of this plan, the monitoring working group should start by

assigning responsibilities and filling in the lead actor for each activity, based on their capacities

and current activities.

Table 9.2, Investment costs for the development of an integrated water quality monitoring plan (time investment).

Description Output Investments (US$)

Time (days)

Setting up working group, setting goals, dividing tasks between monitoring actors. Product: workplan for developing a monitoring plan

1 meeting and workplan description

1,000 5


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Description Output Investments (US$)

Time (days)

Chapter I: Update existing conceptual catchment and lake system description. Find consensus among stakeholders over system concepts.

1 meeting and written chapter

4,000 20

Chapter II: What questions / information needs does the monitoring need to serve?

2 meetings, interviews and written chapter

4,000 20

Chapter III: Inventory of existing monitoring programs and operational technology present among stakeholders

1 meeting, gather and rank information

2,000 10

Chapter IV: Link chapters I, II and III. List system parameters to be monitored. Ideal spatial distribution and frequency of monitoring. Show types of data and pilot graphs and how these fulfil the information needs

1 meeting, example analysis based on existing or example data.

4,000 20

Chapter V: Operational program. Divide monitoring tasks over existing actors. Who does what? Show final budgets

1 meeting. Writing chapter

2,000 10

Chapter VI: Information management. Write down data and information procedures, data ownership, central database

Writing chapter 2,000 10

Chapter VII: Open community. What can be contributed by citizen science (mapping fish cages, reporting algal blooms)


Chapter VIII: Describe existing links to scientific community, present common research goals and plan


Closing presentation

Presenting to stakeholders

200 2

Total costs for devising a monitoring plan (US$)

21,000 105

The table shows the rough contents of the monitoring plan, the actions and approximate time

needed to write the chapters. This estimate is based on the assumption that the systems,

information needs and technology approach as described in previous paragraphs is followed.

Important elements for a comprehensive and successful monitoring plan are the following:

• Chose a central monitoring actor or coordinating body (for instance Brantas - PJT1 as the

coordinator in an arranged MoU with DLH and BWS Sumatera II):

o Both DLH-SU and BWS Sumatera II already have the responsibility to carry out

quantity and quality monitoring in Lake Toba. PJT1 has recently started water

quality monitoring. PJT1 is allowed to collect fees for the management of the lake,

and as part of the management plan they also have a financing plan, similar to the

plans which they also have in the other basins. One of these actors could be a

central data manager or a coordinating body could be appointed and empowered

by MoUs between PJT1, DLH-SU and BWS Sumatera II.



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• Chose and empower central data manager.

• Open community: Lower bariers for exchange of data:

o PJT1, DLH, BMKG currently have implemented data policies. Follow these data

policies and if needed devise additional open and transparent regulations on data

exchange, especially to crucial stakeholders and the scientific community.

o Agreement on sharing the data in this Roadmap, for instance in a central database.

This could be the first step towards a more formal data sharing mechanism. BWS

Sumatera II has already agreed to data sharing.

• Long term budget linked to plan.

• Open community: foster links to scientific community:

o To foster links to scientific community links between LIPI, PusAir, other institutes,

universities and international partners can be strengthened. This ensures new

insights and linking to research and education ensures future inflow of well-

educated river and lake managers.

• Use data to improve existing and new models (such as LIPI):

o The system models as developed by LIPI are very useful for future impact analysis.

However, these models need data for calibration and verification. Data needed for

development and calibration of detailed models are: hourly temperature, rainfall,

wind and wind direction, and depth profiles of temperature (T) and dissolved oxygen

(DO). And a good temporal (weekly/monthly) and spatial dataset on the modelled

parameters, such as P, N and chlorophyll (algal) concentrations, will also be created

across depth gradients.

• Include local stakeholders, for example with local knowledge (such as mapping fish cages,

reporting algal blooms).

o Possible options to connect to and gather information from lake users could be an

online system or a mobile application for tourism, such as send and receive

swimming water conditions, fisher folk (send and receive info on algae bloom,

oxygen condition), water supply (water intake/swimming water conditions).

o Local communities can also ‘adopt’ new monitoring facilities, such as sensors or a

mesh network.


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9.3 Monitoring parameters While the selection of critical parameters, sampling locations and frequency of sampling needs to be determined by the stakeholders as part of the monitoring plan, a first list of variables can be compiled to guide the process (Table 9.3). The list is based on Chapman’s monitoring guidelines (1996; Table K.3) adapted to Lake Toba: • Signal function (minimum investment) – sample variables for background monitoring

monthly; • Exploratory function (intermediate investment): same as statistic but lower frequency for

expensive analyses; • Statistic function (no budget constraints) – sample variables for background monitoring

plus for aquatic life & fisheries plus for recreation and health weekly.

All monitoring scenarios take 40 sampling locations, combining the best sites from the existing 28 of DLH-SU, 12 of LIPI and 20 of PJT1. Some of these are close together and could be combined. The number and locations of sampling sites should be gradually implemented and evaluated every year. In addition to the parameters that are indicative of the in-lake water quality (Table 9.3), a second set of parameters is proposed in Table 9.4 for background and depth profiles. In the medium term (5-10 years), some of the sampling points could be developed for real-time online monitoring. In Table 9.3 prices per sample have been used to account for differences between laboratories and support separate calculations for signal, exploratory, and statistic monitoring, as well as for depth profiles (Table 9.4). Once the total budget has been secured, it could be used to equip a dedicated laboratory at Lake Toba and support sampling processes by the various institutions. Table 9.3, Frequency of sampling for in-lake water quality variables (based on Chapman, 1996, see Table K.3) for a signal, exploratory and statistical function at Lake Toba (40 sampling sites) with the price per sample.

31 The price per sample includes capital and operational expenses as per usual practice of commercial laboratories.

Frequency / Month Unit price/sample31

(IDR) Signal Exploratory Statistic

General parameters

Temperature 1 4 4 52,990

Colour 1 4 4 148,372

Odour 4 4 52,990

Suspended solids 1 4 4 211,960

Turbidity/transparency 1 4 4 127,176

Conductivity 1 4 4 105,980

Total dissolved solids 4 4 211,960

pH 1 4 4 52,990

Dissolved oxygen 1 4 4 105,980

Hardness 4 4 190,764

Chlorophyll a 1 1 4 572,291

Nutrients 529,899

Ammonia 1 4 4 211,960

Nitrate/Nitrite 1 4 4 423,919

Phosphorous or phosphate 1 4 4 317,939

Organic matter

TOC 1 1 4 529,899

COD 1 4 4 476,909



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Table 9.4, Frequency of sampling for water quality variables (based on Chapman, 1996; see Table K.3) for a signal, exploratory

and statistical function for background and depth profiles.

Background monitoring Depth profiles

General parameters

Temperature x x

Colour x

Suspended solids x x

Turbidity/transparency x x

Conductivity x x

pH x x

Dissolved oxygen x x

Chlorophyll a x x

Nutrients

Ammonia x

Nitrate/Nitrite x

Phosphorous or phosphate x

BOD 1 4 4 476,909

Major ions 1 4 4 317,939

Sodium 1 4 4

Potassium 1 4 4

Calcium 1 4 4

Magnesium 1 4 4

Chloride 1 4 4

Sulphate 1 4 4

Other inorganic variables

Fluoride 4 4 211,960

Boron 4 4 169,568

Cyanide 1 4 529,899

Trace elements 1 4 582,889

Heavy metals 1 4 317,939

Arsenic & selenium 1 4

Organic contaminants

Oil and hydrocarbons 1 4 847,838

Organic solvents PASSIVE SAMPLING 2,755,475

Phenols 1 4 635,879

Pesticides PASSIVE SAMPLING 1,907,636

Surfactants 1 4 0

Microbiological indicators

Fecal coliforms 4 4 370,929

Total coliforms 4 4 370,929

Pathogens 1 4 3,285,374

Dissolved gasses (CO2/CH4) 1 4 1,483,717


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Organic matter

TOC x

COD x x

BOD x x

Major ions

Sodium x

Potassium x

Calcium x

Magnesium x

Chloride x

Sulphate x

In addition to measuring the water quality parameters mentioned above, environmental

variables need to be monitored, such as the extent of aquaculture and livestock numbers, to

guide predictions and modelling efforts. An overview of the three investment scenarios is

presented in Table 9.5 and the total costs are summarized in Table 9.7.

Table 9.5, Overview of interventions in the three scenarios for water quality monitoring.

Signal Exploratory Statistical

Monitoring working group Monitoring plan Monitoring plan Monitoring plan

Water quality analysis in-

Lake

Table 9.3 and 9.4

Table 9.3 and 9.4

Table 9.3 and 9.4

River outflows - 10 River lake inflows,

monthly, background

package 2)

20 River lake inflows,

weekly, background

package 2)

Depth profiles 10 locations,

monthly, WQ

package depth

profile 2), 10 depths

per location

10 locations, weekly,

WQ package depth

profile 2), 10 depths per

location

20 locations, weekly,

package depth profile 2); 10 depths per

location

Passive samplers:

pesticides, (vet)medicines

- 10 locations, dry and

wet season

20 locations, dry and

wet season

Meteorology stations and

fixed sensors

2 online met

stations; 4

continuous online

depth profiles basic

WQ

4 online met stations; 8

online continuous online

depth profiles based

WQ

4 online met stations;

16 online continuous

online depth profiles

based WQ

mapping & surveys Survey of

aquaculture:

mapping locations,

supply chain sales,

stocking densities

Signal parameters +

mapping farmers

Exploratory

parameters + mapping

domestic interventions

Toba Research fund 1 PhD study 5 PhD studies 10 PhD studies



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9.4 Investment scenario

Based on the estimated requirements for sampling and the other elements of water quality

monitoring, three investment scenarios have been elaborated. A summary of the costs required

for water quality sampling is presented in Table 9.6. With the addition of costs for the working

group and the research fund, the annual costs for low, intermediate and high investment

scenarios vary from 20 to 92 billion Indonesian rupiah (Table 9.7). Total investment costs of a

minimal program would be IDR 102.2 billion (US$ 7.6 million) for the first five years from 2018

to 2022. A more ambitious intermediate program would cost a total of IDR 240.9 billion (US$

17.9 million), while an aspirational program would amount to IDR 461.1 billion (US$ 34.2 million)

for five years.

Table 9.6, Summary of sampling costs for three functions, corresponding to three investment scenarios, based on sampling frequency and unit prices in

Table 9.3. Annual costs

Signal Exploratory Statistical

General parameters 661 2,696 3,520

Nutrients 458 1,831 1,831

Organic matter 712 2,086 2,849

Major ions 153 610 610


987 1,750

Trace elements

280 1,119

Organic solvents

712 2,849


3,001 7,732

Dissolved gasses (CO2/CH4)

712 2,849

Total (million IDR) 1,984 12,915 25,109

US$ equivalent (000) 147 957 1,861

Table 9.7, Investment scenarios for an integrated water quality monitoring plan. The costs are expert opinions

based on personnel, commercial laboratory analyses and equipment costs. Minimal Intermediate High

Monitoring working group 280 561 1,966

Water quality analysis 1,984 12,915 25,109

Depth profiles 3,244 14,059 28,118

River outflows 228 1,977

Passive samplers 1,262 2,524

Meteorology stations and fixed sensors

(incl. CAPEX)

13, 513 16,323 27,027

Mapping & surveys 80 160 240

Research 1,338 2,676 5,352

Total (million IDR/year) 20,439 48,184 92,313

Total for 2018-2022 (million IDR) 102,195 240,920 461,565

US$ equivalent (000/year) 1,515 3,571 6,841

US$ equivalent for 2018-2022 (000) 7,573 17,853 34,203


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Table 9.7 shows direct costs for monitoring parameters that are not or incidentally monitored

at the moment. Moreover, the emission estimates depend on accurate statistical data of the

catchment, such as population numbers, livestock numbers, and fish production. These have

not been separately budgeted because it is an existing task for various government units.

Specific recommendations on the statistical data include the following:

• Certified data on amounts produced;

• Certified data on number of livestock per type at desa level;

• Number of livestock in what types of farms (small scale, large industrial scale);

• Locations of large-scale farms;

• Record waste water treatment facilities;

• Record licensed hotels, industries and other businesses.

Install on-lake meteorological stations that measure Temperature, rainfall, wind strength and

direction continuously, at least at four locations distributed across the lake (North, South, East,

West). An option could be to connect to weather forecasts already available in operational

databases and model DEWS/FEWS at BMKG. Costs are estimated at US$ 100,000 for each

site.

In anticipation of the monitoring plan the DLH-SU and LIPI monitorings locations could be

merged to achieve full coverage along the shoreline and mid-lake. The monitoring frequency

should increase to weekly for the upper epilimnion and can be monthly for depth profiles on

fewer locations. One could envisage in the monitoring plan a split between cheap and quick

manual variables gathered daily/weekly with a depth profile. Add more expensive variables that

are monitored monthly with a depth profile only for selected variables. These ‘trade-off’ choices

based on costs should be made during the development of the monitoring plan, in clear

coherence with the management information needed to monitor the state and to develop

system understanding.

In addition to the effort mentioned above, some variables can be monitored and data provided

online and on very high frequency and across a depth profile. These are T, DO, conductivity,

salinity.

In order to monitor the presence of possible toxic substances, a technique called ‘passive

sampling’ is useful and cost-effective. Passive samplers (such as silicon sheets) absorb the

micro pollutants during their deployment in water. They will absorb a time averaged (optimally

4 weeks) amount of the micro pollutants. Subsequently, these can be analysed in the lab for

pesticides, medicine (like antibiotics in aquaculture and human consumption) and hormones.

Hence only one single analysis will yield a time-averaged concentration of these pollutants.

Laboratory costs in a western laboratory are about US$ 4,000 in total for about 150 types of

substance.

The build-up of gasses (CO2 and CH4) can be a hazard for the local community. This is not part

of a monitoring plan, but can be researched by for example LIPI. Methane (CH4) in solution can

influence the lake stratification and as such is important to measure.

The use of existing telecommunication facilities can be integrated into the water monitoring

plan. The mobile network provides real time data relay from sensors and measuring stations to

a data server. According to the Tourism Report, PJT1 and others, the existing coverage of

telecommunication facilities around Lake Toba and core tourism areas is excellent, including



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internet and data services. In terms of service provision, TELKOMSEL has the best coverage,

with a stable connection and speed of data transfer, followed by ProXL and Smartfren.

TELKOMSEL and ProXL provide 4G connection. To support water quality monitoring purpose,

those providers could be contacted to discuss the best package or program for data transfer.

No specific investment is needed, other than a SIM card.

Data transmission to base stations should be included in the monitoring plan. If existing

connections are not reliable, there are numerous alternatives to 2G, 3G or 4G internet

connections. Specifically for lake monitoring, a LoRa mesh network could be set up with lake-

based fixed and on line systems (https://www.lora-alliance.org/technology). This is low cost

technology and these costs are negligible compared to other costs in this report.

Establishment of a remote sensing program in the future would allow specific questions about

Lake Toba water-quality, suspended particulates and algal-bloom dynamics. Regionally-tuned

models for Sentinel-2A+2B, Landsat-8 as well as MERIS / S3A / VIIRS will need to be

developed, integrating available in-situ sampling data. Such further efforts are summarized as

follows and (conservative) cost estimates for each item are provided in Table 9.8.

• refining spatial analysis using specific sampling locations and transects to better understand the noted changes in water-quality visible in ~mid 2005 (MERIS data) using additional data from MODIS (Aqua / Terra);

• performing focused multi-sensor analysis to determine specific conditions leading to the acute water-quality events of record (May 4, 2016 and Jan 9, 2017);

• refining atmospheric correction, glint, speckle and masks to improve data quality;

• incorporating processing of two new sensor platforms Sentinel-2B and Sentinel-3A (ramp-up completion expected by year-end 2017);

• defining a detailed remote sensing monitoring approach (specific sensors, processing chains and algorithm settings) as part of comprehensive water-quality management strategy.

Table 9.8, Summary of action items for remote sensing of water quality in Lake Toba

Action Item Cost Estimate (USD)

(1) Refinement of spatial data analysis $20,000

(2) Multi-sensor data analysis for acute water quality events (2016, 2017) $30,000

(3) Improving remote sensing data quality $20,000

(4) Incorporate new remote sensing platforms (Sentinel-2B and 3A) $30,000

(5) Develop approach for remote sensing data use as part of water quality

management strategy

$25,000

(6) Training of GOI personnel on the use of remote sensing methods and data

for water quality monitoring applications

$25,000

The cost estimate in the table above are one-time expenses required to develop and implement

a remote sensing monitoring strategy for the lake and its contributing watershed, and it is

estimated that this work can be carried out over a period of one year (or less). The costs of

operating such a program, for example, on an annual basis (for budgeting purposes) can be

estimated based on staff, institutional and other costs; this would be part of item (5) in Table

9.8.


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An additional recommendation is to build capacity in the use of remote sensing tools to

complement other efforts in water quality, or as a starting point for new efforts. This could be

done as part of a larger effort to advance the state of knowledge and application of remote

sensing for water resources assessments. In the case of Lake Toba, this would involve

developing a tailored training or capacity building activity such as item (6) proposed in Table

9.8, that would engage the corresponding stakeholders to assimilate remote sensing as an

additional tool to support water resources management in the lake and its surrounding

environment.

An important item moving forward is the incorporation of remote sensing observations into

water quality management tools being used in Lake Toba, and specifically water quality

modeling (Sumatera model) developed and in use fort the lake. Together with ground-based

observations and remote sensing data, a system to support decisions and investments in the

Lake Toba watershed should be developed and implemented, which will guide the evaluation,

prioritization and costing of measures and actions for lake water quality improvements.



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10 Summary results, conclusions and recommendations

The tourism sector in Indonesia is a promising growth sector that can provide inclusive

and sustainable opportunities for economic development. The archipelago is home to one

of the most biodiverse habitats in the world, having a rich array of tourism endowments

that form the underlying draw for visitors. Indonesia has expanded the offer and promotion

of its natural resources by increasing the size of protected areas and attracting more online

interest in natural activities. Despite this, Indonesia’s tourism industry is not operating at a

level consistent with the quality and diversity of its natural and cultural endowments, with

environmental sustainability being a key risk factor for the sector (WEF, 2017).

Four key constraints contribute to Indonesia not fulfilling its tourism potential. These

include: (i) continued poor access to, and quality of, infrastructure and services for citizens,

visitors and businesses; (ii) limited tourism workforce skills and private-sector tourism

services and facilities outside of Bali; (iii) weak enabling environment for private investment

and business entry; and (iv) poor inter-ministry/agency, central-local and public-private

coordination and weak implementation capabilities for tourism development in general,

and for monitoring and preservation of natural and cultural assets in particular.

In response, the Government has launched the Indonesia Tourism Development Priority

Program. For the implementation of the program, the GoI has decided to sequence the

development of tourism destinations, starting with three priority destinations: Lombok in

West Nusa Tenggara province; Borobudur-Yogyakarta-Prambanan in Central Java

province and the Special Region of Yogyakarta; and Lake Toba in North Sumatra province.

If developed effectively, these three distinctively different and unique destinations are

expected to increase their combined annual foreign and domestic visitor expenditures from

an estimated US$1.2 billion in 2015 to US$1.5 billion in 2021 and US$2.0 billion in 2026

(Horwath, 2017).

The objective of this report has been to prepare a Roadmap for Improving Water Quality

of Lake Toba as a Tourism Destination. It provides an understanding of the key drivers

leading to water quality issues along with costed investment scenarios associated with

specific investments aimed at reducing nutrient loads into the lake. These are intended to

inform preparation of an Integrated Tourism Master Plan to provide a stronger framework

for effective and sustainable tourism development.

Lake Toba is the largest volcano-tectonic lake in the world and one of Indonesia’s priority

tourism destinations. However, Lake Toba is largely a destination for local tourism with

declining appeal. With improvements in environmental sustainability, accessibility and

activities, Lake Toba can become an attractive destination for a wider variety of domestic

and international visitors.

This chapter summarizes the main findings of the study, with a focus on phosphorous (P),

the main determining factor of water quality in Lake Toba.


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10.1 Drivers of lake eutrophication

The most important aspect of water quality in Lake Toba is the amount of nutrients that

are dissolved in the lake. This is the “trophic state”. In contrast to other pollutants,

continuous pollution with nutrients (‘eutrophication’ by phosphorous and nitrogen) has the

potential to irreversibly affect the lake’s chemistry and biology on a system level. The water

quality of Lake Toba is under threat from eutrophication. Eutrophication is mainly driven

by nutrients from aquaculture (68% of total phosphorous load and 76% of total nitrogen).

Other contributors include livestock (19% of phosphorous and 5% of nitrogen) and

domestic wastewater (11% of phosphorous and % of nitrogen), shown in Figure 10.1.

Figure 10.1, Relative phosphorous loads into Lake Toba (P loads) from various sources for the whole lake.

10.2 Status and functioning of Lake Toba

Science informed policy measures have established the desired lake quality as

oligotrophic. The governor of North Sumatra issued decrees that indicate that the water

quality of Lake Toba should meet class I (raw water for drinking); and that the trophic state

of Lake Toba should be the natural state, being oligotrophic. In reality, based on available

data from monitoring sites scattered along shorelines, observed values show mesotrophic

status for phosphorous and oxygen profiles while nitrogen, chlorophyll and transparency

point to oligotrophic status but occasionally reach the mesotrophic as well. The

mesotrophic state leads to local effects such as algal blooms that harm the tourism sector.

Compared to data from 1930 (Ruttner, 1931), when the areas surrounding Lake Toba were

not yet affected by aquaculture, agriculture or forestry, the water quality in the lake has

decreased, both at the surface and at greater depths.



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10.2.1 Historical and current lake status

Monitoring water quality parameters indicate eutrophic states in Lake Toba ranging from

oligotrophic to mesotrophic. Table 10.1 presents an overview of the main conclusions on

the monitored parameters. The compartment model that predicts lake nutrient

concentrations has been calibrated to match monitored phosphorous and nitrogen

concentrations of 2015 by varying the retention rates of these nutrients in the model.

Ultimately, the modelled values for the year 2015 lie well within the ranges monitored in

the various compartments in the lake. Model results of LIPI suggest that local levels of

nutrient concentrations locally reach eutrophic levels, due to intense loading from sources

such as aquaculture. The conclusions below refer to long term average concentrations.

Due to the lake’s large size and long residence time, the effects of pollutant loads will

become visible over long time spans. Therefore present-day concentrations were

compared to concentrations measured in the 1930s. All monitored water quality

parameters have deteriorated since the 1930s both near the water surface and in deeper

water layers.

Table 10.1, Overview of present status of selected water quality parameters at Lake Toba: phosphorous,

nitrogen, chlorophyll-a, transparency, temperature and oxygen (based on data from DLH-SU, LIPI,

and PTAN).

Parameter Status in Lake Toba

Phosphorous Oligotrophic (2008-2012) to mesotrophic (2012-2016).

Phosphorous concentrations 1930: 0.005 mg/l; 2013: 0.01 PO4-P mg/l; 2016 peak: 0.05 PO4-

P mg/l.

Nitrogen Oligotrophic, mostly below 350 μg total nitrogen per litre, very occasionally above 650 μg/l.

Chlorophyll α

(algae)

Ultra-oligotrophic (till end 2014).

Mesotrophic (Feb-Aug 2016) with chlorophyll concentrations up to 12 µg/l.

Transparency Oligotrophic: 6m (Secchi depth highest 2009-2010: above 10m32); 1930s: 7.5-11.5 m

2016: algal bloom, sudden and drastic decrease, afterwards back to 6m.

Temperature Stable: between 25 and 28 degrees Celsius at water surface, stable for the last 10 years.

Temperature profiles and show clear stratification.

2016: peak over 28 degrees.

Oxygen Surface water concentrations constant in last 90 years, with peaks in 2006, 2007, 2016.

DO levels steadily decline as depth increases and remain the same beyond 200 meters.

Below 150 m in period 2008-2017: values below 0.5 mg/l; 1930s: 5.35-5.40 mg/l.

10.2.2 Lake functioning

To evaluate the effect of future developments on lake water quality, a general

understanding and agreement by stakeholders regarding the functioning of the lake is

important to produce useful calculations and widely supported policy recommendations.

To predict nutrient concentrations and subsequent eutrophication, the following factors on

lake functioning need to be considered for monitoring: lake vertical mixing or lake

stratification, horizontal mixing or hydraulic circulation and nutrient decay. The nutrient

loading, meaning the nutrient inputs to the lake by each source, is not a direct lake

characteristic but does require monitoring and quantification.

32 Lakes with Secchi depth above 10m do not qualify for ASC certification.


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The knowledge regarding vertical and horizontal water mixing in Lake Toba influences the

quantification of nutrient balance of the lake. Based on a comparison between modelled

and monitored chlorophyll concentrations, the default thermocline depth in Lake Toba is

estimated at around 50m, in line with observed thermal stratification data (PTAN, LIPI). As

a consequence, the pollutants emitted to the lake dissolve in the upper 50m water volume.

The water residence time in Lake Toba is around 80 years. Due to non-homogenous

mixing, this could be much longer for specific segments of Lake Toba. A long residence

time has the consequence that replacement of polluted lake water by clean inflows takes

a long time. Natural purification processes could be faster, but more research is needed

to determine whether this occurs in Lake Toba. It is important to note that a long residence

time makes an existing eutrophic state almost irreversible. Lake management of nutrients

is therefore of high importance and should start immediately.

Horizontal mixing determines the dispersion of pollutants entering the lake by rivers or

direct input. The shape of Lake Toba makes it unlikely that high pollutant loads in the North

will quickly reach the Southern part of the lake. However, in some of the current carrying

capacity calculations it is assumed that any pollutant entering the lake is immediately

dissolved in the total water volume of the lake33. This under-estimates the pollutant

concentrations occurring in the lake.

Monitoring data indicate lake stratification, oxygen depletion at greater depths and

fluctuations in stratification depth. The model-based analysis demonstrated that wind may

lead to bi-annual mixing and re-stratification events in the upper 10-20m in most of the

years. Deep mixing does not occur, explaining the lack of dissolved oxygen (anoxia) in the

deep layers (approximately >100m). Some upwelling of cooler water from deep layers

occurs, but these cooler waters do not arrive at the water surface (at least in the observed

period 2008-2016).

A zonal approach to modelling the water quality of Lake Toba provides new insights into

the functioning and drivers of water quality. Four theoretical compartments have been

defined based on topography and bathymetry. This includes one northern and three

southern compartments. These compartments provide a differentiated assessment of the

key drivers associated with water quality in Lake Toba. The compartment model that

predicts lake nutrient concentrations has been calibrated to match monitored phosphorous

and nitrogen concentrations of 2015 by varying the retention rates of these nutrients in the

model. Ultimately, the modelled values for the year 2015 lie well within the ranges

monitored in the various compartments in the lake. These can be further refined based on

a continuous process of improvement informed through better data. The results show

localised impacts requiring targeted strategies for the monitoring and management of

water quality interventions.

10.3 Water quality monitoring

10.3.1 Data assessment

The currently available data cover all aspects needed for an initial water quality

assessment and to construct simple effect models. There is no integrated monitoring

33 This is following current government regulations and therefore normal procedure in Indonesia



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program in which lake wide data were collected, stored and analysed over longer periods

of time. Data and their collection efforts were scattered among stakeholders. Datasets had

different levels of usefulness ranging from data to incidentally establish lake status to

(scarce) data with solid statistical validity. Field data are often low frequency data suited

to follow long term trends in status but usually have a frequency too low (years) or spatial

distribution too scarce to properly understand lake functioning. There appears to be no

mechanisms for systematic data quality control. Table K.4 presents an overview of the

various data and their characteristics.

The available water quality monitoring data are mostly included in reports and not as raw

data in digital form or as ‘open source’ data. When raw data are made available by

stakeholders, it is often in the form of Excel files. No centralized database has been

encountered.

The DLH-SU, LIPI and PTAN data were made available as raw data only to a limited

extent. Some data were supplied in the form of graphs only. PTAN data covered a

relatively high frequency consistent time series, while DLH-SU and LIPI covered larger

parts of the lake, albeit with lower or incidental monitoring frequency.

The DLH-SU data set is the most extended one of these three sources. With respect to

the required water quality parameters based on Chapman (1996), only a low number is

missing (hardness, conductivity, sodium, potassium, calcium cyanide, arsenic and

selenium, organic solvents, phenols, pesticides, surfactants). Probably, only the organic

contaminants (solvents, phenols, pesticides) are of any relevance to Lake Toba, compared

to the Chapman guideline. The PTAN and LIPI data sets are less ‘complete’ with respect

to their set of water quality parameters.

High frequency data (monthly or more) give more insight into lake functioning. Lower

frequency data (often at more locations) are useful for long term trends. In the quantitative

assessment of lake functioning, the PTAN dataset proved to be very useful. The dataset

covers a period of about 10 years at 4 locations near Samosir Island. The DLH-SU and

LIPI data, although of lower frequency, were useful as supporting data to verify whether

measured data values by PTAN were consistent across the lake.

To improve the analysis of lake stratification, better meteorological data are required. The

meteorological station at Medan airport is 80 km North of Lake Toba, whereas the

mountain range and the ridge of the caldera shield the lake from direct influence of wind.

Therefore, two on-lake meteorology stations, preferably with on-line internet connection

(hourly data at least), one in the central basin north and the other in the central basin south

of Samonsir peninsula would greatly reduce the uncertainty regarding the physical

conditions and analyses of events or anomalies such as shown in Figure 6.20.

The hydrology and water balance of Lake Toba hint at potential water sources explaining

the lake’s cooler deep water. To improve the hydrothermal analysis (especially with

respect to the upwelling events), more information on these sources is required. For this,

dissolved gases such as CO2 and CH4 and their sources need to be observed. In case of

high concentrations of dissolved CO2, this gas may reduce the lake’s stability with turnover

events, such as in Lake Nyos in Cameroon, West Africa. CH4 would enhance its stability.


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10.3.2 Towards a water quality monitoring plan for Lake Toba

For the design of an effective water quality monitoring program, three pillars are

important: 1) system knowledge, 2) information needs (with a focus on management

decisions), and 3) technical possibilities.

For pillar 1, the analysis in this report shows that eutrophication is the most important process threatening water quality in Lake Toba, for which various causes and effects should be monitored. Additional elements could be included as well to better understand lake functioning. In Table 9.3 and Table 9.4 in-lake water quality variables are listed, together with a suggested sampling frequency for a signal, exploratory and statistical function of Lake Toba. In addition to currently monitored parameters, dissolved gases such as CO2 and CH4 and their sources need to be monitored. In view of tourism and recreational water use, microbiological indicators such as coliform bacteria and pathogens need to be included in a regular monitoring plan as well.

System knowledge of Lake Toba can be further improved by development of a dynamic

model. This long-term goal can ensure consistent monitoring for quantitative analysis,

combined with a good definition of the parameters that need to be monitored.

The Reference Group and other stakeholders together shape the information needs (pillar

2), ideally by forming a dedicated monitoring working group. For the integration of data

collection, it is important to coordinate institutions, streamline methods, include spatial and

bathymetric stratification, and establish database management, preferably central and

open source. Collaboration between research centers, universities and other institutions

around Lake Toba is required for successful implementation of an integrated monitoring

program. This can be supported with a grant and research funding program.

For pillar 3, it is relevant to expand the technical monitoring capabilities. For lake

stratification: better meteorological data should be collected. Two on-lake meteorological

stations preferably with on-line internet connection, one in the central basin north and the

other in the central basin south of Samonsir peninsula would greatly reduce the

uncertainties on physical conditions. A LoRa mesh network could be set up to relay data

from sensors and measuring stations to a data server.

The investments needed to set up an integrated water quality monitoring plan and suggestions for monitoring efforts to be included in the plan, are summarised in Table 10.2, based on Table 9.2.



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Table 10.2, Summary of investment costs for an integrated water quality monitoring plan. Minimal Intermediate High

Monitoring working group 280 561 1,966

Water quality analysis 5,228 26,974 53,227

Other measurements 1,490 4,501

Meteorology stations and fixed

sensors (incl. CAPEX) 13,513 16,323 27,027

Mapping, surveys and

research 1,418 2,836 5,592

Total (million IDR/year) 20,439 48,184 92,313

Total for 2018-2022 (million

IDR) 102,195 240,920 461,565

US$ equivalent (000/year) 1,515 3,571 6,841

US$ equivalent for 2018-

2022 (000) 7,573 17,853 34,203

10.4 Water quality management

Various measures can be designed to reduce the nutrient load into Lake Toba and

stimulate natural purification processes. In the next sections, combined scenarios of

mitigating measures are proposed for those drivers that produce the highest loads of

nutrients: aquaculture, livestock and domestic wastewater. Additional measures on other

drivers may further reduce nutrient loadings and improve Lake Toba’s environment. A

rough indication of budget requirements has been added for various scenarios of

interventions.

10.4.1 Potential of interventions

Based on the relative inputs of nutrients, aquaculture (68% of total phosphorous), livestock

manure (19%) and domestic wastewater (11%) have been identified as the starting point

for mitigating measures. Individual measures are discussed in more detail below.

However, only when various measures are combined in an integrated approach can

effective reductions in nutrient loads be achieved. In chapter 8, four scenarios have been

introduced that were applied to each of the three major drivers of water quality. These

correspond to a baseline scenario for comparison and a low, intermediate and high

investment scenario, briefly summarized below. Table 10.3 shows an overview of the exact

numbers and percentages applied in each scenario.

Scenario A

This is the baseline scenario, without any interventions. For aquaculture the current

production level is maintained at 84,800 tons of fish per year with a Food Conversion Ratio

(FCR) of 1.9.


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Scenario B

This is the low scenario, with limited interventions in wastewater management. For

aquaculture, in absence of any measures, the production level is assumed to grow to a

maximum level of 106,000 tons with a Food Conversion Ratio (FCR) of 1.9. For

wastewater a slow implementation of the currently planned water and sanitation program

is assumed, in which the number of people with access to on-site sanitation (such as septic

tanks or latrines) increases from 0% in 2018 to 66% in 2022 and 94% in 2042.

Scenario C

This is the intermediate scenario, with interventions in aquaculture, livestock and

wastewater management. For aquaculture, the one remaining license is not renewed and

will expire naturally. There will be increasing pressure on fish farmers without licenses.

This will result in assumed production levels of 64,000 tons in 2018, 50,000 tons in 2022

and 10,000 tons in 2042. For the management of livestock manure, biogas conversion is

promoted, resulting in 1% conversion of manure into biogas in 2018, 20% in 2022 and

40% in 2042. For wastewater the currently water and sanitation program is implemented

as planned. Thus the number of people with access to on-site sanitation (such as septic

tanks or latrines) increases from 50% in 2018 to 85% in 2022 and 94% in 2042. In addition,

limited investments in off-site sanitation supply 2% of the population with a sewerage

system in 2022 and 6% by 2042.

Scenario D

This is the high scenario, the most optimistic one, with interventions in aquaculture,

livestock and wastewater management. For aquaculture, an active reinforcement policy

ensures that a production level of 10,000 tons is reached from 2022 onwards. In addition,

better feeding practices allow for a better food conversion ratio of 1.2. For the management

of livestock manure, biogas conversion is promoted more actively, resulting in 5%

conversion of manure into biogas in 2018, 30% in 2022 and 60% in 2042. For wastewater

the water and sanitation program is accelerated with additional funding. The number of

people with access to on-site sanitation (such as septic tanks or latrines) increases from

50% in 2018 to 69% in 2022 and then drops to 50% in 2042. In 2022 31% of the population

is connected to a central sewerage system, growing to 50% in 2042.

Figure 10.2 shows the impact of the combined scenarios on phosphate loads across the

four compartments. In the next sections, more detail is provided on the nature and broader

context of proposed interventions to reduce nutrient emissions into Lake Toba.



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Figure 10.2, Four investment scenarios with their impacts over time on the total total phosphorous (P) loads

into the whole Lake Toba (as one compartment). See Table 10.3Table 10.3 for an overview of the

applied input values.

Table 10.3, Overview of four investment scenarios to reduce nutrient loads into Lake Toba.

Driver Scenario A

baseline

Scenario B

low

Scenario C

intermediate

Scenario D

high

Aquaculture

Extrapolation

of current

situation

Growth to maximum Gradual reduction of

production


production

2018

2022

2042

848,00 tons

FCR 1.9

106,000 tons, FCR 1.9 64,000 tons, FRC 1.9

50,000 tons, FCR 1.9

10,000 tons, FCR 1.9

64,000 tons, FRC 1.2

10,000 tons, FCR 1.2

10,000 tons, FCR 1.2

Livestock Extrapolation

of current

situation

Extrapolation of current

situation

Conversion of manure

into biogas

Conversion of manure into

biogas

2018

2022

2042

1% conversion

20% conversion

40% conversion

5% conversion

30% conversion

60% conversion


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Driver Scenario A

baseline

Scenario B

low

Scenario C

intermediate

Scenario D

high

Wastewater No intervention

Slow implementation

Implementation as

planned

Accelerated implementation

2018

2022

2042

On-site: 50%

On-site: 50%

On-site: 50%

On-site: 50%



On-site: 50%



On-site: 50%



Tourists/

year

Business as

usual

Business as usual Best case Best case

2018

2022

2042

1,802,200

2,059,000

2,307,000

1,802,200

2,059,000

2,307,000

1,802,200

2,212,000

3,410,300

1,802,200

2,212,000

3,410,300

10.4.2 Reducing nutrient loads from aquaculture

While an integrated approach to water management is required for Lake Toba, water quality cannot be improved without reducing the current production of aquaculture. Four scenarios have been modelled to compare the impacts of low, intermediate and high levels of investments on the nutrient loading within Lake Toba. Interventions in aquaculture (Table 10.4) include: aiming for a gradual reduction of fish production under the intermediate scenario C and an accelerated, more rigorous approach under the high scenario D. In the modelling of nutrient outputs, these two options are compared to a baseline scenario (maintaining current production of 84,800 tons) and a growth scenario (B), in which production increases to 106,000 tons.

Table 10.4, Summary of targets and total estimated investment costs for the period 2018-2022 to reduce nutrient

loads from aquaculture into Lake Toba, in intermediate C and high D scenarios. C. Intermediate D. High

Target

production in 2022

FCR

50,000 tons

1.9

10,000 tons

1.2

Infrastructure 0 50

Institutional

Coordination 200 400

Law Enforcement 150 300

Training 2,400 12,000

Market Development 500 4,000

Information 6,450 17,400

Total (in million IDR) 9,700 34,150

US$ equivalent (000) 719 2,531

10.4.3 Managing livestock manure

The main source of pollution from livestock is manure. It can be used as organic fertilizer in

agriculture and as renewable energy source (biogas). The major recommendation for reducing

nutrient loads from livestock manure is to promote biogas production. Table 10.5 summarises

the targets and costs of biogas interventions for the period 2018 to 2022.



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loads from livestock manure into Lake Toba, in intermediate C and high D scenarios.

C. Intermediate D. High CAPEX OPEX CAPEX OPEX

Target Conversion of manure into biogas (%)

20%

0%

Infrastructure 5,340 1,026 7,440 1,433

Institutional 2,800 4,400

information 3,750 5,500

Subtotal 5,340 7,576 7,440 11,333

Total (in million IDR) 12,916 18,773

US$ equivalent (000, split) 396 561 551 840

US$ equivalent (000, total) 957 1,391

10.4.4 Wastewater management

The major recommendation for reducing nutrient loads from domestic wastewater (including

from tourists) is to speed up the implementation of the current national sanitation strategies.

Funding has been reserved for these strategies, though this may only be sufficient for a

relatively slow implementation process, as included under the low scenario B. The more

ambitious targets for the intermediate C and high D scenarios are provided in Table 10.6,

together with the required investments between 2018 and 2022. Institutional and information

aspects are included in the operational costs that are given as total over 5 years.


loads from domestic wastewater into Lake Toba, in low B, intermediate C and high D scenarios.


CAPEX OPEX CAPEX OPEX CAPEX OPEX

Targets

Peak tourist numbers 343114 368623 368623

Access to

On-site and community-based

systems

Centralized systems

66%

1%

85%

2%

69%

31%

Infrastructure

On-site systems (individual septic

tanks, community-based systems

and IPLT)

636,000 89,180 1,154,000 116,531 370,000 93,566

Medium centralized 95,000 10,925 236,000 18,655 3,693,000 240,932

Subtotal 731,000 100,105 1,390,000 135,185 4,363,000 334,498

Reserved 730,472 100,105 730,472 100,105 730,472 100,105

Extra investment required (106 IDR) 528 0 659,528 35,081 3,632,528 234,393

Total (million IDR) 529 694,610 3,866,922

US$ equivalent (000, split) 39 0 48,872 2,600 269,176 17,369

US$ equivalent (000, total) 39 51,472 286,545


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176

10.4.5 Total investment costs for mitigating measures

As the graphs in chapter 8 showed, interventions in livestock and wastewater management have limited impacts on total nutrient loads in Lake Toba. An integrated approach with a rigorous reduction of aquaculture is required to significantly improve water quality in the lake. The total costs for each driver are summarized in Table 10.7 and



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Table 10.8, resulting in total investments for each scenario. Note that under scenario B, the only interventions are in domestic wastewater, while aquaculture production is allowed to grow in this scenario. Total rounded investment costs for the first five years (2018-2022) would be, in the low scenario B: IDR 529 million (US$ 39,000) for water quality management alone or IDR 103 billion (US$ 7.6 million) including monitoring. In the intermediate scenario C the costs would be IDR 717.2 billion (US$ 53.0 million) without, and IDR 958.1 billion (US$ 70.8 million) with monitoring. The five year costs of the high scenario D would be IDR 3,919.8 billion (US$ 290.5 million) for the most effective reduction in nutrients; combined with an aspirational water quality monitoring program the total costs would be IDR 4,381.4 billion (US$ 324.7 million).

Table 10.7, Summary of targets and total estimated costs for a low B, intermediate C and high D level of investment

to improve water quality in Lake Toba for the period 2018-2022 (in million IDR).


CAPEX OPEX34 CAPEX OPEX CAPEX OPEX

Targets

Fish production 106,000 50,000 tons 10,000 tons

Conversion of manure into biogas 20% 30%

Peak tourist numbers 343,114 368,623 368,623

Access to


systems

Centralized systems

66%

1%

85%

2%

69%

31%

Investments

Aquaculture 9,700 34,150

Livestock 5,340 7,576 7,440 11,333

Wastewater35 528 0 659,528 35,081 3,632,528 234,393

Subtotal 528 0 664,868 52,357 3,639,968 279,876

Water quality management B. Low C. Intermediate D. High

Total (CAPEX + OPEX in million IDR)

for 5 years 529 717,225 3,919,845


Total (million IDR) for 5 years 102,195 240,920 461,565

Total water quality management

and monitoring (million IDR) 102,724 958,145 4,381,410

34 Operational expenses for five years from 2018 to 2022. 35 For wastewater management, net required investments (minus reserved funds) are listed.


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178

Table 10.8, Summary of targets and total estimated costs for a low B, intermediate C and high D level of investment

to improve water quality in Lake Toba for the period 2018-2022 (in 000 US$ equivalents).


CAPEX OPEX CAPEX OPEX CAPEX OPEX

Targets

Fish production 106,000 50,000 tons 10,000 tons

Conversion of manure into biogas 20% 30%

Peak tourist numbers 343,114 368,623 368,623

Access to


systems

Centralized systems

66%

1%

85%

2%

69%

31%

Investments

Aquaculture 719 2,531

Livestock 396 561 551 840

Wastewater36 39 0 48,872 2,600 269,176 17,369

Subtotal 39 0 49,268 3,714 269,727 20,739

Water quality management B. Low C. Intermediate D. High

Total (CAPEX + OPEX in 000US$) for

5 years 39 52,982 290,466


Total (000 US$) for 5 years 7,573 17,853 34,203

Total water quality management

and monitoring (000 US$) 7,612 70,834 324,669

10.4.6 Mitigation options and effects on eutrophication

Changes in emissions have been modelled for the most contributing drivers aquaculture,

livestock and wastewater. The resulting nutrient concentrations in the lake have been

calculated based on a budget model approach. This approach does not take into account the

complexity of physical and biogeochemical processes, nor their variability in time and space.

Therefore, they do not account for long-term effects that could be aggravating (because of

accumulation effects) or improving (because of natural purification processes) the water quality

status of the lake. More detailed research is required to increase understanding of the long

term effects and processes affecting water quality in Lake Toba.

In the figures below the cumulative impact of the four combined scenarios on nutrient loads is presented, together with the resulting long-term concentrations for the whole lake and each of the four lake compartments. The scenarios are summarized in Table 10.3, while Figure 10.3 gives an overview of the four compartments. The displayed concentrations represent equilibrium concentrations on the basis of input data for 2018, 2022 and 2042. It may take tens of years to achieve each of these equilibrium states (Figure 7.13). Limits for oligotrophic and mesotrophic state have been indicated for nitrogen at 350 and 650 μg/l respectively, and for phosphorous at 10 and 30 μg/l (based on Nürnberg, 1996; Table C.2 in Annex C.3). Figure 8.12 shows the results for the whole lake and Figure 8.13 for the four compartments. The graphs show loads and long-term concentrations by compartment at fixed scales to enable comparisons between compartments.

36 For wastewater management, net required investments (minus reserved funds) are listed.



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179

Figure 10.3, Overview of the four compartments of Lake Toba in which the intervention scenarios have been

applied.

Figure 10.4, Projected impacts of four intervention scenarios (summarized inTable 10.3) on total loads and resulting

long-term concentrations of nitrogen (left) and phosphorous (right) for the whole of Lake Toba.


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180

Figure 10.5, Projected impacts of four intervention scenarios (summarized in Table 10.3) on total loads and

resulting long-term concentrations of nitrogen (left) and phosphorous (right) across four compartments

North, S1, S2, and S3 of Lake Toba (according to Figure 10.3).



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Without any interventions (scenarios A and B), nutrient concentrations will continue to rise,

leading to a long-term eutrophic state in the northern and southern compartment S1 for

phosphate and mesotrophic for nitrogen. The southern compartments S2 an S3 would remain

mesotrophic for phosphorous and oligotrophic for nitrogen. Substantial reductions in nutrient

loads, concentrations and trophic state can only be achieved in the two scenarios with reduction

of aquaculture: the intermediate C and high D scenarios.

For nitrogen (N), compartments S2 and S3 would remain oligotrophic in all scenarios. In the

northern compartment, increased loads under A and B would result in long-term concentrations

above the oligotrophic limit of 350 µg/l. This is mainly because of the loads from aquaculture

(Table 8.6 and Figure 8.5). In the smallest southern compartment S1, only scenario D would

lead to long-term concentrations below the limit for oligotrophic state, and scenario C in 2042,

with a maximum aquaculture production of 10,000 tons/year.

For phosphorous, the situation is different. For the lake as a whole, none of the scenarios would

eventually lead to an oligotrophic state. However, the effects differ significantly across the

compartments. In southern compartments S2 and S3, phosphorous loads from 2022 onwards

in scenario D would eventually bring the total phosphorous concentrations from a mesotrophic

level down to just below the oligotrophic limit of 10 µg/l. Concentrations in the northern

compartment N would slowly go down below the limit for a mesotrophic state, based on the

loads in 2022 and 2042 in scenarios C, and all years in scenario D.

Compartment S1 is the smallest and also the most problematic in terms of water quality.

Because of the intensive use with high population densities and livestock, the loads lead to very

high long-term concentrations. In scenario C and D aquaculture is halted completely, but loads

from livestock and wastewater each bring the long-term phosphorous concentration to levels

above the oligotrophic limit of 10 µg/l (Figure 8.7 and Figure 8.11). Combined, these loads lead

to a long-term mesotrophic state for phosphorous, even under scenarios C and D.

Only when mitigating measures in all sources: aquaculture, livestock and domestic loads are

applied, under the high scenario D, can the oligotrophic limit eventually be reached in

compartments S2 and S3. For the lake as a whole and in the northern compartment, the

mesotrophic limit will be feasible. For compartment S1 additional measures will be needed.

10.5 Investments for impact

While an integrated approach to water management is required for Lake Toba, water quality

cannot be improved without reducing the current production of aquaculture. Four scenarios

have been modelled to compare the impact of low, intermediate and high levels of investments

assumed to impact the nutrient loading within Lake Toba.

Only by reducing aquaculture in the lake to a total production level of 10,000 tons or less can

water quality in the lake be expected to improve, with long-term concentrations dropping below

the oligotrophic limit. This means that in the small compartment S1, no aquaculture is allowed

at all. Aquaculture can be reduced by further limiting licenses through coordination and

increasing law enforcement, supported by training in alternative livelihoods such as organic

farming and fisheries. The estimated total costs over five years would be IDR 9.7 billion (US$

719,000) under an intermediate scenario, gradually bringing down fish production, and IDR

34.2 billion (US$ 2.5 million) under a high investment scenario to reach the target of 10,000

tons of fish per year in 2022, limited to Haranggoal Bay and smallholders around the lake.


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Crucial to the success of these measures is the political commitment to not renew expired

licenses and implement more stringent regulations to ensure compliance.

Interventions in livestock manure and domestic wastewater management can reduce nutrient

loads to further strengthen the impact of measures in aquaculture. This is particularly important

in the northern compartment and in the smallest southern compartment S1. In these

compartments the long-term concentrations of phosphorous would reach levels above the

oligotrophic limit of 10 µg/l in N and the mesotrophic limit of 30 µg/l in S1, even without any

aquaculture.

The stimulation of conversion of livestock manure into biogas would require IDR 12.9 billion

(US$ 957,000) under an intermediate scenario, aiming for 20% conversion in 2022 and IDR

18.8 billion (US$ 1.4 million) under a high investment scenario resulting in 30% conversion. For

wastewater management, current national sanitation strategies could be accelerated,

accelerating the construction of individual and community-based on-site systems, based on

septic tanks. An intermediate scenario would provide 85% of the population in the catchment

area of Lake Toba with septic tank systems by 2022, for an extra investment of IDR 694.6 billion

(US$ 51.5 million), while a high investment scenario would provide access to centralized sewer-

based systems for 31% of the population for IDR 3,866.9 billion (US$ 286.5 million).

Investments in sanitation have a limited impact on nutrient reductions, but would make Lake

Toba more appealing to tourists.

For the smallest compartment S1, that is currently in a eutrophic state, urgent measures are

needed to reduce nutrient loads. Under the intermediate, high and alternative scenarios no

aquaculture is allowed in this compartment from 2042 in the intermediate scenario C and from

2022 in the high D and alternative E scenarios. The remaining drivers of eutrophication in this

compartment are nutrient loads from livestock and domestic wastewater. A dedicated survey

could identify the most important point and non-point sources of pollution around this

compartment, to target specific measures.

The targeted oligotrophic status can only be achieved through an integrated management plan

under a high investment scenario for three of the four compartments. Total net investment costs

for this scenario would be IDR 3,919.8 billion (US$ 290.5 million). The impacts of these

interventions on long-term nutrient concentrations would be different for each of the

compartments. In the southern compartments S2 and S3 the long-term phosphorous

concentrations would be around the oligotrophic limit of 10 µg per litre from 2022 onwards. In

the northern compartment, these concentrations would be just avove the limit. In the smallest

and most intensively used compartment (S1, west of Samosir), even high investments without

any aquaculture activities, would bring the long-term concentrations above the mesotrophic

limit of 30 µg per litre. The intermediate scenario, at a cost of IDR 717.2 billion (US$ 53.0

million) for the first five years, would get close to these results only in 2042. In 2022 the

intermediate scenario would not reach long-term oligotrophic concentrations for phosphorous

in any of the compartments.

A combination of options could be a cost-efficient approach, through selecting high investment

interventions for aquaculture and livestock, together with the intermediate interventions for

wastewater. This would be justified as the investments in sanitation have a relatively limited

impact on nutrients, even though it would make the area more appealing. The total costs over

five years of such an alternative combination (E, Table 10.9) would be IDR 747.5 billion (US$

55.4 million), a reduction of IDR 3.17 billion (US$ 235 million) as compared to the high scenario



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D, while the impacts on water quality would still be high because of the strong reduction in

aquaculture (Figure 10.6 and Figure 10.7).

Table 10.9, Summary of targets and total estimated costs for an alternative E level of investment to improve water

quality in Lake Toba for the period 2018-2022.

E. Alternative

(in million IDR)

E. Alternative

(in 000 US$)

CAPEX OPEX CAPEX OPEX

Targets

Fish production 10,000 tons

Conversion of manure into biogas 30%

Peak tourist numbers 368,623

Access to

On-site and community-based systems

Centralized systems

85%

2%

Investments

Aquaculture (high) 34,150 2,531

Livestock (high) 7,440 11,333 551 840

Wastewater37 (intermediate) 659,528 35,081 48,872 2,600

Subtotal 666,968 80,564 49,423 5,970

Water quality management

Total (CAPEX + OPEX) for 5 years 747,533 55,393


(high, total for 5 years) 461,565 34,203

Subtotal water management and monitoring 666,968 542,129 49,423 40,173

Total

1,209,098

89,596

37 For wastewater management, net required investments (minus reserved funds) are listed.


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Figure 10.6, Nutrient loads of total nitrogen (left) and total phosphorous (right) resulting from a high D and

alternative E scenario to reduce nutrient emissions from aquaculture, livestock manure and wastewater, in

Lake Toba as a whole.

Figure 10.7, Projected impacts of three intervention scenarios (summarized in Table 8.14) on total loads and

resulting long-term concentrations of nitrogen (left) and phosphorous (right) in Lake Toba as a whole.

A comprehensive water quality monitoring program is required to determine long-term trends

in Lake Toba and inform an adaptive management approach. This should be based on

collaboration aligned with institutional responsibilities and free open source data sharing. When

combining the existing activities of the main water quality monitoring institutions, a

comprehensive approach can be achieved, encompassing signal, exploratory and statistical

functions. This should include regular sampling and analysing a range of variables for

background monitoring and depth profiles, at no less than forty stations distributed across the

lake. It is estimated to cost a minimum of IDR 102 billion (US$ 7.6 million) for a total of five

years, while an aspirational program building on latest technologies and involving stakeholders

is estimated to cost around IDR 462 billion (US$ 34.2 million).



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Sustained political commitment across all levels of government and sectoral coordination

among different stakeholders is essential to realising the government’s agenda for improving

the water quality and tourism value of Lake Toba. Such an approach needs to be supported by

a water quality and waste load monitoring program to continuously assess the impact of

interventions under the integrated management plan. This enables adaptive actions during

implementation. Together, the proposed interventions and monitoring plan would guide the

integrated management of water quality in Lake Toba and support the contribution of Lake

Toba to the economic and social development of Indonesia and serve as an example for the

management of other lake basins.


Developing a Roadmap for Improving Water Quality of Lake Toba Tourist Destination, Indonesia –

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Lake Kivu; East Africa. PloS One 10(3): e0121217. DOI 10.1371/journal.pone.0121217

RPJMN, 2014. Rencana Pembangunan Jangka Menengah Nasional (RPJMN) 2015-2019.

Kementerian Perencanaan Pembangunan Nasional/ Badan Perencanaan

Pembangunan Nasional (Ministry of National Development Planning / National

Development Planning Agency).

Rustini, A.H., Lukman, and Iwan Ridwansyah, 2014. Estimation 2-dimensional flow pattern in

Lake Toba. Research Center for Limnology-LIPI. Limnotek 21 (1): 21-29

Ruttner, F., 1931, Hydrographische und hydrochemische Beobachtungen auf Java, Sumatra

und Bali, Arch. Hydrobiol. Suppl. 8: 197–454.

Schmid, M., Halbwachs, M., & Wehrli, B., 2005. Weak mixing in Lake Kivu: new insights indicate

increasing risk of uncontrolled gas eruption. Geochemistry 6(7). DOI

10.1029/2004gc000892

Schmid, M., Tietze, K., & Halbwachs, M., 2003. How hazardous is the gas accumulation in

Lake Kivu? Arguments for a risk assessment in light of the Nyiragongo volcano eruption

of 2002. Acta Vulcanologica 15(1-2): 115–122.

Sene, K. J., Gash, J., & McNeil, D. D., 1991. Evaporation from a Tropical Lake - Comparison

of Theory with Direct Measurements. Journal of Hydrology 127(1-4): 193–217.

Sianipar, I. R. H. 2011. Studi Deskriptif Gondang Sabangunan dalam Upacara Kematian

Saurmatua pada Masyarakat Batak Toba di Kota Medan. Medan: Universitas

Sumatera Utara. Available from http://repository.usu.ac.id/handle/123456789/29021



Final Report

A-5

A-5

Sitanggang, R., 2017. Illegal logging rusak DTA Danau Toba. Medan Bisnis Daily 11 Nov.

2017. Available from

http://www.medanbisnisdaily.com/news/read/2017/11/11/326098/illegal-logging-

rusak-dta-danau-toba/

Soeprobowati, T. R., 2015. Integrated Lake Basin Management for Save Indonesian Lake

Movement. Procedia Environmental Sciences 23: 368–374. DOI

10.1016/j.proenv.2015.01.053

Tilley, E. et al, 2008. Compendium of Sanitation Systems and Technologies, Swiss Federal

Institute of Aquatic Science and Technology (EAWAG), Dubendorf, Switzerland.

Times Indonesia, 2016. "Danau Toba Tercemar Limbah." Times Indonesia, August 1. Available

from https://m.timesindonesia.co.id/read/129651/20160801/192108/danau-toba-

tercemar-limbah/

Toba Tilapia, 2016. Toba Tilapia. Powerpoint presentation August 29, 2016.

TTPS, 2009. Sanitation system and technolog options (originally in Indonesian Opsi Sistem

dan Teknologi Sanitasi). Jakarta, Indonesia: Government of Indonesia. Technical

Team for Sanitation Development (TTPS), led by Bappenas, in collaboration with the

World Bank’s Water and Sanitation Program - East Asia and the Pacific (WSP-EAP).

UNEP, 2004. Guidelines on Municipal Wastewater Management. The Hague: UNEP/GPA

Coordination office, The Hague. United Nations Environment Programme.

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Program (USDP), January 2015, USDP-R-PIU.T-10083-2. Available from

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Verdegem, M., 2013. Nutrient discharge from aquaculture operations in function of system

design and production environment. Reviews in Aquaculture 5: 158-171.

Vernimmen, R., 2015. Hydrological analysis and modelling of the Toba-Asahan River Basin,

Indonesia. Report for the BWRMP project. Deltares.

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Forum. Available from http://reports.weforum.org/travel-and-tourism-competitiveness-

report-2017/

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Young, O. R., 2002. The institutional dimensions of environmental change: fit, interplay and

scale. MIT Press, Cambridge, Massachusetts, USA.

Zomer, R. J., Trabucco, A., Bossio, D. A., & Verchot, L. V., 2008. Climate change mitigation: A

spatial analysis of global land suitability for clean development mechanism

afforestation and reforestation. Agriculture, Ecosystems & Environment 126(1): 67-80.


– Final Report


A-6

A Stakeholder consultation process

A.1 Reference Group

Table A.1, Members of the Reference Group for the Water Quality Road Map for Lake Toba.

Institution/

Institusi

Name/

Nama

Position/

Posisi

Office/

Jabatan

Menko

Maritim

Dr. Rahman

Hidayat

Director/

Asisten Deputi

Department for Navigation, Fisheries

and Tourism Infrastructure/Departemen

Infrastruktur Pelayaran, Perikanan, dan

Pariwisata

PUPR-BPIW Hadi Sucahyono Head/ Kepala Center for Strategic Areas/Pusat

Pengembangan Kawasan Strategis

Menko

Maritim

Velly Asvaliantina,

M.Eng.Sc

Head/ Kepala Sector Nautical and Tourism

Infrastructure/Bidang Infrastruktur

Pariwisata Bahari

PUPR-BPIW Raymond Tirtoadi Repres/ Wakil Center for Strategic Areas/Pusat

Pengembangan Kawasan Strategis

LIPI Dr. Fauzan Ali Head/ Kepala Center of Limnology/Pusat Penelitian

Limnologi

LIPI Dr. Ir. Lukman

MSi.

Research/

Peneliti

Center of Limnology/Pusat Penelitian

Limnologi

BPPT Dr. Ir. Rudi

Nugroho, M.Eng.

Director/

Directur

Center for Environmental

Technology/Pusat Teknologi

Lingkungan

BPPT Prof. Dr. Titin

Handayani

Repres/ Wakil Center of Environmental

Technology/Pusat Teknologi

Lingkungan

KLHK Dr. Budi

Kurniawan

Repres/ Wakil Directorate for Water Pollution

Control/Direktorat Pengendalian

Pencemaran Air

KLHK Hermono Sigit Repres/ Wakil Directorate for Watershed and Aquatic

management/Direktorat Pengendalian

Kerusakan Perairan Darat

DLH-SU Dr. Ir. Hj. Hidayati Head/ Kepala Provincial Environment Agency North

Sumatra) /Badan Lingkungan Hidup

Sumatra Utara

BWS-S2 Baru Panjaitan Head/ Kepala Basin Management Center Sumatra II/

Balai Wilayah Sungai Sumatera II

BWS-S2 Novita R Section Head/

Kepala Seksi

Operation and Maintenance/Operasi &

Pemeliharaan

BOPDT Arie Prasetyo Head/ Kepala The Lake Toba Tourism Area

Management Authority/Badan Otorita

Pariwisata Danau Toba



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A-7

A-7

A.2 Meetings

A.2.1 Stakeholder meetings

Various group meetings have taken place during the project so far (Table A.2). Two NetMap

exercises were performed at the end of the two rounds of stakeholder meetings that took place

from 1 to 17 May and from 1 to 14 June. Minutes of meetings are grouped separately as

deliverable 6 (for internal use only).

Table A.2, Stakeholder meetings for WQ Roadmap in 2017.

Date Place Participants Topic

March 16 Jakarta Reference Group Kick off meeting

May 10 Jakarta Reference Group Inception

May 17 Jakarta Reference Group and

additional key

stakeholders

Presentation of initial stakeholder mapping

Discuss draft Legal, Institutional, and

Political Economy Assessment

First NetMap exercise

June 14 Laguboti,

North

Sumatra

Reference Group

Local level

participants

Second NetMap exercise

Presentation of initial findings Lake and

Catchment Assessment

August 7 Jakarta Reference Group Presentation and discussion of final Lake

& Catchment Assessment

August 24 Medan,

North

Sumatra

Reference Group

Local level

participants

Presentation of final Lake & Catchment

Assessment

Presentation of preliminary

recommendations

September

28

Jakarta Reference Group Draft recommendations


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A-8

A.2.2 Individual meetings

Various individual meetings and semi-structured interviews have been held as part of the

process of information collection for the WQ Roadmap.

Table A.3, Overview of meetings and interviews in 2017.

Name Institutions date team members

Bp. Fauzi BPDAS - Forestry 18-20 March JanJaap

Bp. Gunawan, Bp.

Giovandi Siahaan

PLTA Renun 22 March JanJaap, Henni,

Hanny, Satrio

Ibu Hidayati, Ibu Bayu

Nasution, Bp. Umanda

LH Province North

Sumatera

23 March Team

Ibu Made Sumiarsih Min. PUPR Central

Reservoirs (including lake)

25 April Bouke and Henni

Bp. Samsuhari, Ibu Inge Min. LHK 25 April Bouke and Henni

Bp. Mees Krimpen, Bp.

Amrizal, Bp. Dhanang

Wuryandoko, Bp. Arief

USDP 25 April Bouke and Henni

Bp. Wisnu, Bp. Ludfie ATR - BPN 18 May JanJaap and

Henni

Bp. Yosi Sukmono Bappeda North Sumatra 5 June Arina and Henni

Bp. Kusriadi replace by

Ibu Dolphin

Cipta Karya North

Sumatra

6 June Arina and Henni

Ibu Retno KKP (Perikanan) North

Sumatra


Bp. Indra, Bp. Hendro LH Sampah North

Sumatra


Bp. Bonar Tampubolon,

Bp. Dipman, Bp. Sirait,

Bp. Simanjuntak

PDAM Tirtonadi Waste

water treatment plant

division (field officer)


Bp. Wisnu ATR - BPN 21 June JanJaap, Henni,

Nata



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B-1

B-1

B Detailed description of Lake Toba

B.1 Bathymetry

Lake Toba is formed in the caldera of the Toba Volcanic Complex. It is the largest volcanic lake

in the world. The deepest parts of the lake are approximately 500 meters deep (Table B.1).

Table B.1, Dimensions of Lake Toba (source QGIS/Open Streetmap).

Dimension Value

Perimeter 240 km

Longest diagonal 90 km

Longest width 30 km

Water surface area 1 124 000 000 m2

Lake water volume 256 200 000 000 m3

Mean depth 227 m

Maximum depth 505 m

Figure B.1 shows the lake area and the depth contour lines. Samosir Island is clearly visible in

the middle, more or less dividing the lake in two bigger parts to the north and south. In the

Southern part two relative shallower areas to the West and East can be identified and in the

middle a deep section can be seen. Originally, the island was a peninsula, but when a sluice

gate was constructed in the west and the narrow isthmus was cut, it became an island. The

strip of water to the west between Samosir and the main land is narrow and shallow; in the

model this became the southern compartment S1.

Figure B.1, Bathymetry of Lake Toba (Source: Lake Toba atlas, BWRMP-TOBA)


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B-2

B.2 Hydrological and administrative boundaries

The catchment area of Lake Toba and the Asahan River completely lies in the Province of

North Sumatra. There are several kabupaten that border the lake (Figure B.2):

• Samosir (Island and to the West), by far the largest land surface;

• Toba Samosir to the South East;

• Tupanuli and Humbang Hasundutan to the South West,

• Karo and Dairi to the North;

• Simalungun to the North East.

Figure B.2, Lake Toba Area (TBA) related districts/kabupaten: Dairi, Humbang Hasundutan, Karo, Pakpak Barat,

Samosir, Simalungun, Tapanuli Utara, and Toba Samosir.

In only two districts Lake Toba covers more than 25 percent of the kabupaten area (Samosir

(84%) and Toba Samosir 36%), while in the other kabupaten Lake Toba covers a far smaller

area. Pakpak Barat is part of the TBA, but does not drain into the lake. Therefore in calculations

of interventions only seven kabupaten are considered. Downstream from the water level

regulating dam at Siruar, the Asahan River flows through Kabupaten Asahan.

B.3 Soil

The soil in the region is typical for weathered volcanic areas. The geology of the Toba volcanic

lake has unique features (Chesner, 2012). The soils that have formed from the lava are

generally susceptible to erosion, which is important in the modelling of surface runoff.



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B-3

B-3

Within the catchment area four main soil types are found (Figure B.3). East of Lake Toba the

soil is a complex of lithosol and regosol that is highly sensitive to erosion, with podsilik brown,

sensitive to erosion, in the southeast. The west side of the lake mainly has the same brown

podzolic soils and on Samosir Island the majority of the soil is of the brown forest soil type that

is somewhat sensitive to erosion (Damage Control Directorate of Aquatic Ecosystems, 2017).

These are classified as follows:

- Light Clay (classification nr 2) - Clay Loam (classification nr 5) - Loam (classification nr 9) - Loamy Sand (classification nr 11)

These soil types in the hydrodynamic model determine the run-off rates and to estimate

groundwater flows. The data are very coarse, but sufficient for this rapid assessment.

Figure B.3, Soil types around Lake Toba.

B.4 Climate

The precipitation regime in the region is typical for the humid tropics and characterized by a

major wet season from August through to November and a minor wet season from March to

May. The months in between are transition-months with varying precipitation, never below 50

mm per month (Table B.2). The average yearly precipitation in the region during the period

2003-2016 amounts to approximately 2,850mm/year. However, within the short time series

significant differences in total precipitation from year to year can be seen (Figure B.4). In the

driest year (2005) total precipitation was only 2,198mm, while in the wettest year (2011) a total

of 3,489mm rain fell in the region. The period 2003-2016 (14 years) is too short to draw

conclusions on climatic trends.


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B-4

Table B.2, Monthly precipitation rates for the period 2003-2016 (source: Vernimmen, 2015)

Figure B.4, Total annual precipitation around Lake Toba from 2003 till 2016.

For this rapid assessment on the catchment hydrology with the purpose to draft a roadmap to

improve the water quality of Lake Toba, it suffices that the annual precipitation rate in the area

fluctuates significantly and there is a significant difference between the total amount of

precipitation in dry and wet years.

The temperature at Parapat, on the eastern shore of Lake Toba is stable, with an annual average of 21.5 degrees Celcius for the period 2006 to 2016 (Table B.3).

month 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Average

1 137 130 57 113 145 133 108 179 189 102 278 117 213 92 142

2 189 191 81 106 69 89 149 160 178 273 280 114 90 136 150

3 375 270 212 149 170 271 355 201 281 178 129 122 191 80 213

4 325 267 190 293 334 331 312 255 330 422 279 295 259 176 291

5 247 143 144 268 268 179 195 149 260 237 250 212 260 226 217

6 255 124 108 151 149 167 137 212 144 114 125 147 129 184 153

7 215 388 188 132 212 224 230 321 159 234 146 70 131 181 202

8 146 187 190 194 215 307 367 276 586 334 311 493 346 176 295

9 434 487 206 227 286 296 350 372 310 319 294 209 221 239 304

10 423 389 349 248 402 427 497 233 514 315 422 331 136 255 353

11 341 347 243 212 345 214 263 446 352 393 341 266 338 339 317

12 191 210 230 176 146 167 198 245 186 244 329 301 173 282 220

Total 3278 3131 2198 2268 2740 2805 3160 3049 3489 3164 3183 2674 2484 2366 2856



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B-5

B-5

Table B.3, Monthly mean temperatures in Parapat for the period 2006-2016 (source: Meteorological, Climatological,

and Geophysical Agency (BMKG) , 2016)

Year

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2006 20,8 21,4 22,0 21,7 21,7 21,7 22,2 22,2 21,1 21,1 20,7 20,8

2007 21,1 21,0 21,3 21,6 22,1 21,7 21,7 21,3 21,6 20,7 21,3 20,6

2008 21,2 21,0 20,3 21,0 21,7 21,3 21,2 21,3 21,3 20,9 21,3 20,9

2009 20,4 21,0 21,2 21,9 22,6 22,3 22,1 21,9 21,8 21,7 21,2 21,1

2010 21,3 22,2 21,7 22,0 22,8 22,4 21,5 22,2 21,2 22,0 21,3 21,0

2011 20,5 20,7 21,2 21,7 22,0 22,2 22,4 21,4 21,7 21,3 21,3 21,0

2012 21,2 21,1 21,2 21,4 22,3 22,2 21,5 21,7 21,8 21,1 21,5 21,0

2013 21,4 20,6 22,1 22,3 22,3 22,3 22,1 22,2 21,6 21,8 21,0 21,2

2014 20,5 21,6 21,8 21,3 21,8 23,1 22,7 21,5 21,3 21,4 21,2 20,8

2015 20,9 21,0 21,4 21,3 21,5 21,3 21,8 21,2 21,5 21,2 21,0 21,3

2016 21,8 21,4 22,6 22,5 22,3 22,1 21,8 22,7 22,4 22,7 21,5 21,5

Average

21,0 21,2 21,5 21,7 22,1 22,1 21,9 21,8 21,6 21,4 21,2 21,0

Potential reference evaporation was based on the global 1 x 1 km CGIAR-PET monthly data

set (available from: http://www.cgiar-csi.org; Zomer et al., 2008). The data is based on the

Hargreaves model. This model performed almost as well as the Penman-Monteith model, but

required less parameterization, with significantly reduced sensitivity to error in climatic inputs

(Hargreaves and Allen, 2003). Average annual reference evaporation for the Toba-Asahan river

basin was computed at 1,556 mm.

B.5 Water level

The objective of the regulating dam is to manage Toba outflow to the Asahan River in such a

way that the Toba Lake water levels are within the range required for various uses on site and

downstream. Hence the Asahan flow needs to meet downstream requirements, i.e. sufficient

for electric power generation and other downstream uses, and must at the same time avoid

flood damage along downstream sections of the Asahan River.

The water level of Lake Toba can be operated through variation of the outflow through the

regulating gate at Siruar. In principle, the water level is kept between 905.25m and 902.50m

above sea level. This is done with a release that varies between 90 and 140m3/s to the

downstream Asahan River (Figure B.4).

http://www.cgiar-csi.org/


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B-6

Figure B.5, Monthly averaged discharges at the Siruar Regulating Dam, the Siguragura Dam and the Tangga Dam

(expressed in m3/s) for the period 1957 to the present (source: PT Inalum)

Figure B.5 shows the end-of-month Toba Lake water level (in meters above mean sea level /

MSL) from the year 1975 to the present (source: PT Inalum). The figure illustrates that given

runoff from the surrounding slopes and Samosir Island, the inflow from PLTA Renun (since

1993), water consumption around Toba Lake, and precipitation on and evaporation from the

lake, the Siruar Dam is operated since the early 1980’s in such a way that Lake Toba water

levels do not exceed the maximum water level and does not fall below the minimum desired

water level. This is done in order not to interrupt the intensive use the Toba Lake shoreline for

fishing, boating, aquaculture, and recreational activities, and to not cause damage to the related

infrastructure like port facilities or shore protection. Only during May, June and July 1998, the

level dropped below the minimum water level (to a minimum of 902.28m above sea level), and

consequently, the discharge via the Siruar Regulating Dam was reduced. If the water level

comes close to the maximum level of 905.5m more water is released, to keep the level from

rising too high. Above this level certain settlements are flooded. The extra water is released

through the spillways of the structures in the cascade, and cannot be used for hydropower

generation.

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

Jan-55 Jan-60 Jan-65 Jan-70 Jan-75 Jan-80 Jan-85 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15

Monthy averaged discharge Siruar Regulating Dam (m3/s)

Monthly averaged Siguragura discharge turbines + spillway (m3/s)

Monthly averaged Tangga discharge turbines + spillway (m3/s)



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B-7

B-7

Figure B.6, End of month Toba Lake water level (in meters above mean sea level / MSL) from 1975-2015 (source:

PT Inalum).

902.0

902.5

903.0

903.5

904.0

904.5

905.0

905.5

906.0

Jan-55 Jan-60 Jan-65 Jan-70 Jan-75 Jan-80 Jan-85 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15

End of month Lake Toba water level (m+MSL)



Final Report

C-1

C-1

C Background on functioning of lakes

C.1 Theory of residence time

A consequence of the large water body and the relative small outflow is the long residence time

of the water in Lake Toba. The concept of water residence time (or turnover time) is particularly

important. The residence time of lakes may range from a few days to many tens of years, or

even to a century or more. A simple form of residence time can be calculated by dividing the

lake volume by the outflow (Chapman, 1996). Lake Toba’s theoretical residence time is

approximately 80 years:

(256,200,000,000𝑚3) (100 𝑚3 𝑠⁄ × (60 × 60 × 24 × 365)) = 81.2 𝑦𝑟⁄

The residence time as calculated above is however purely theoretical, because it is based on

the assumption of homogeneous mixing of the lake. Stratified lakes (such as Lake Toba) have

a much longer residence time than the theoretical value (Meybeck, 1995).

Why is the concept of residence time important? The potential recovery time of a lake through

replacement of polluted lake water by clean inflowing water, depends on it. If Lake Toba

becomes polluted with a soluble toxic element, and the source of the pollution is eliminated, it

will take much more than 80 years to remove the polluted water and replace it with non-polluted

water. However, since the residence time in deeper layers may be longer, 80 years’ recovery

time is likely an optimistic estimate. The lake recovery may only be faster if natural water quality

processes within the lake itself are able to decompose the water pollution. Figure C.1 shows

the relation between the scale of water bodies, the recovery time and the reversibility of the

lake system’s state. Lake Toba borders on the category of ‘Irreversible’.

Figure C.1, Schematic representation of the scale of water bodies, recovery time and reversibility of water quality

issues. (Source: Chapman, 1996)

C.2 Theory of biochemical processes

A simplified view of the biogeochemical processes in lakes is shown in Figure C.2. Nutrients

enter the system via river discharges and run-off, or from aquaculture. There they may be taken

up by algae. Algae produce oxygen through photosynthesis, while they consume oxygen


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C-2

through respiration. This results in a daily oxygen variation, with oxygen concentrations

increasing during daytime and decreasing during night time. When the algae die, they change

into detritus, which settles into the deeper lake layers. The detritus may accumulate in the

hypolymnion or at the bottom. There, it could be mineralized back into inorganic nutrients. Since

the mineralization process consumes oxygen, this decreases the oxygen concentrations in the

deeper layer of the lake. Also, fermentation processes may lead to the local accumulation of

methane or carbon dioxide.

Figure C.2, A simplified overview of biogeochemical processes in a lake.

In deep lakes, such as Lake Toba, algal growth is typically limited by light. This is because of

the large epilimnion depth over which the algae are being mixed. During their travels over the

epilimnion they experience light conditions that are on average too small to result in a positive

production flux. Occasionally, however, the depth over which the algae are being mixed is

decreased, due to a change of the (primary or secondary) thermocline depth. Once the light

limitation is removed, an algal bloom may occur. Therefore, the thermocline depth is a key

factor determining the occurrence of algal blooms. Also, thermocline depth determines the

volume over which the nutrients are diluted. Because of its (twofold) importance, thermocline

depth is a key factor.

The peak biomass concentration of the algal bloom is determined by the availability of nutrients.

Nutrient addition from run-off (land activities) and direct input from aquaculture, can lead to

higher nutrient concentrations in the upper layer above the thermocline. This may thus lead to

higher algal biomass in the event of an algal bloom.

Nutrient addition in the form of organic waste however may sink to the hypolimnion, where it is

mineralized, thus leading to higher nutrient concentrations and lower oxygen concentrations

mainly in the deep layers of the lake. Once arrived in the deeper layers, these nutrients will not

directly affect the epilimnion anymore. Since the volume of the hypolimnion is so large, the

increase in nutrient concentration may increase very slowly, at a pace that only becomes visible

when assessed over large periods of time.



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C-3

C-3

Although the nutrient loading of the hypolimnion does not affect the epilimnion directly, it does

entail some risks. During mixing events, for example, nutrients from the hypolimnion may be

returned to the epilimnion. This may support larger algal biomass peaks. Also, when the

hypolimnion is anoxic, the oxygen concentrations in the epilimnion may drop substantially

during a mixing event. This may have large impact on all biology in the epilimnion, and in some

cases even lead to mass mortality events. Even worse may be events of mixing during which

large amounts of CO2 are brought up, which in Lake Nyos suffocated 1,746 people and 3,500

livestock in nearby towns and villages (Giggenbach, 1990).

C.3 Trophic level classification

A qualitative classification based on trophic level is shown in Table C.1 (Chapman, 1996;

Nürnberg, 1996). These classes are basically a continuous range of nutrient concentrations

and associated biomass production (Carslson, 1977).

Table C.1, Lake classification based on trophic level (Chapman, 1996; Nürnberg, 1996)

Classification Description

Oligotrophic

lakes

Lakes of low primary productivity and low biomass associated with low

concentrations of nutrients (N and P). In temperate regions the fish fauna is

dominated by species such as lake trout and whitefish. These lakes tend to

be saturated with O2 throughout the water column.

Mesotrophic

lakes

These lakes are less well defined than either oligotrophic or eutrophic lakes

and are generally thought to be lakes in transition between the two

conditions. In temperate regions the dominant fish may be whitefish and

perch.

Eutrophic lakes Lakes which display high concentrations of nutrients and an associated high

biomass production, usually with a low transparency. In temperate regions,

the fish communities are dominated by perch, roach and bream. Such lakes

may also display many of the effects which begin to impair water use.

Oxygen concentrations can get very low, often less than 1 mg/l in the

hypolimnion during stratification.

Hypereutrophic

lakes

Lakes at the extreme end of the eutrophic range with exceedingly high

nutrient concentrations and associated biomass production. In temperate

regions the fish communities are dominated by roach and bream. The use of

the water is severely impaired as is described below. Anoxia or complete

loss of oxygen often occurs in the hypolimnion during stratification.

Dystrophic

lakes

These are organic rich lakes (humic and fulvic acids) with organic materials

derived by external inputs from the watershed.

The quantitative boundaries of nutrient and chlorophyll concentrations with which to define the

trophic levels vary a bit between scientists and organizsations (Table C.2). Some classifications

are based on more variables, including for example Secchi depth and oxygen (Table C.3). BLH-

SU uses the KLH (2009) boundaries. Most boundaries are similar, although the KLH nitrogen

boundaries are relatively high, with the oligotrophic-mesotrophic boundary of 650 µg total N per

litre being almost twice the value of the other boundaries. This may provide a reason to use the

other boundaries instead. However, changing to different boundaries should be supported by

all stakeholders. Additionally, Chapman (1996) provides nutrient levels including Secchi disk

values. Also, he differentiates between mean annual values for chlorophyll an absolute

maximum and Secchi disk an absolute minimum (Table C.3).


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C-4

Table C.2, List of total P, N and Chl-a concentrations (µg/l) for different trophic states. In this report the cut-off

values proposed by Nürnberg (1996, highlighted in yellow) have been applied.

Variable Oligotrophic-

mesotrophic

Mesotrophic-

eutrophic

Eutrophic-

hypereutrophic

Reference

P 10 30 100 Nürnberg (1996)

15 25 100 Forsberg and Ryding (1980)

10 25 100 Jones and Knowlton (1993)

10 30 100 KLH (2009)

N 350 650 1,200 Nürnberg (1996)

400 600 1,500 Forsberg and Ryding (1980)

300 500 1,200 Jones and Knowlton (1993)

650 750 1,900 KLH (2009)

Chl a 3.5 9 25 Nürnberg (1996)

3 7 40 Forsberg and Ryding (1980)

3 7 40 Jones and Knowlton (1993)

2 5 15 (hyp. > 200) KLH (2009)

Table C.3, Nutrient levels, biomass and productivity of lakes for trophic classes (Chapman, 1996).

Trophic

category

Mean total

phosphorou

s (mg m-3)

Annual

mean

chlorophyl

l (mg m-3)

Chlorophyl

l maxima

(mg m-3)

Annual

mean Secchi

disc

transparenc

y (m)

Secci disc

transparenc

y minima

(m)

Minimu

m

oxygen

(%sat)1

Ultra-

oligotrophic

4 1 2.5 12.0 6.0 <90

Oligotrophic 10 2.5 8 6.0 3.0 <80

Mesotrophic 10-35 2.5-8 8-25 6.0-3.0 3.0-1.5 40-89

Eutrophic 35-100 8-25 25-75 3.0-1.5 1.5-0.7 40-0

Hypereutrophi

c

100 25 75 1.5 0.7 10-0

1 The percentage saturation in bottom waters depending on mean depth.



Final Report

D-1

D-1

D Background on DPSIR

The Driver, Pressure, State, Impact, Response (DPSIR) concept is developed to help systematic analysis of complex issues and to streamline insight and appropriate responses within large groups of stakeholders. It is a flexible scheme assists decision-makers in many steps of the decision process (Figure D.1). DPSIR was initially developed by the Organisation for Economic Co-operation and Development (OECD) and is in use by the US-EPA, United Nations (UNEP), and European Environmental Agency (EEA). This scheme relates human activities to the state of the environment, identifies (often negative) impacts and formulates responses. Table D.1 lists the definitions that describe the elements in DPSIR38.

Figure D.1, Driver, Pressure, State, Impact, Response (DPSIR).

Table D.1, Descriptions for Driver, Pressure, State, Impact and Response (source: EPA)

Element Description

Driver Drivers are the social, demographic and economic developments in societies and

the corresponding changes in life styles, overall levels of consumption and

production patterns. In particular, Drivers are often defined as socio-economic

sectors that fulfil human needs for

• food,

• water,

• shelter,

• health,

• security,

• and culture.

Driving forces can originate and act globally, regionally or locally.

38 For more information about systems thinking and the DPSIR concept, see

https://archive.epa.gov/ged/tutorial/web/html/index.html.

https://archive.epa.gov/ged/tutorial/web/html/index.html


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D-2

Element Description

Pressure Drivers function through human activities which may intentionally or

unintentionally exert Pressures on the environment. Human activities that exert

pressure include:

• Land use changes

• Resource consumption

• Release of substances

• Physical damage through direct contact

Pressures depend on the kind and level of technology involved in source

activities, and can vary across geographic regions and spatial scales.

State The pressures exerted by society may lead to unintentional or intentional

changes in the State of the ecosystem. Usually these changes are unwanted and

are seen as negative (damage, degradation). The pressures exerted by society

may directly impact the ecosystem, such as harvesting or dredging, or may be

transported and transformed through a variety of natural processes to indirectly

cause changes in ecosystem conditions.

The State is the condition of the abiotic and biotic components of the ecosystems

in a certain area in terms of:

• Physical variables - the quantity and quality of physical phenomena such

as temperature or light availability

• Chemical variables – the quantity and quality of chemicals such as

atmospheric CO2 concentrations or nitrogen levels

• Biological variables – the condition at the ecosystem, habitat, species,

community, or genetic levels, such as fish stocks or biodiversity

Impact Changes in the quality and functioning of the ecosystem have an Impact on the

welfare or well-being of humans through the provision of ecosystem services.

Ecosystem goods and services are ecosystem functions or processes that

directly or indirectly benefit human social or economic drivers, or have the

potential to do so in the future.

Ecosystem processes benefit humans through

• Provisioning of food, timber, water

• Regulation of air quality, water quality, or disease

• Cultural benefits including aesthetic or recreational value

• Indirect supporting processes that maintain the ecosystem

The value of ecosystem services depends on human need and use (e.g., market

value).

Response Humans make decisions in Response to the impacts on ecosystem services or

their perceived value. Responses are actions taken by groups or individuals in

society and government to prevent, compensate, ameliorate or adapt to changes

in the state of the environment by seeking to:

• Control drivers or pressures through regulation, prevention, or mitigation

• Directly maintain or restore the state of the environment

• Deliberately “do nothing”

Decision making processes occur at a variety of scales, from individuals to local

management to federal government.



Final Report

E-1

E-1

E Institutional assessment

For the institutional or political economy assessment to be useful for practitioners, the World

Bank approach (Fritz et al., 2014) has been applied. This consists of the following steps:

1. Start with a diagnosis of the specific problem and identify dysfunctional patterns;

2. Analyse why the observed patterns are present, covering three dimensions:

a) Relevant structural factors that influence stakeholder positions

b) Existing institutions, including institutional dysfunctions that channel behaviour

c) Stakeholder interests and constellations

3. Identify ways forward.

The stakeholder assessment/mapping and legal, institutional and political economy

assessment are interlinked, as presented in the three key types of factors that are commonly

considered in governance and political economy analysis (Figure E.1).

Figure E.1, Three clusters of drivers (Fritz et al. 2009).



Final Report

F-1

F-1

F Overview of relevant legislation

F.1 List of laws in English

Acts 1. Act No. 5 of 1990 on the Conservation of Biological Natural Resources and its

Ecosystem

2. Act No. 41 of 1999 on Forestry

3. Act No. 26 of 2007 on Spatial Planning

4. Act No. 32 of 2009 on Environmental Protection and Management

5. Act No. 23 of 2014 on Regional Government

Government Regulation 6. Government Regulation No. 82 of 2001 on Water Quality Management and Water

Pollution Control

7. Government Regulation No. 44 of 2004 on Forest Planning.

8. Government Regulation No. 45 of 2004 on Forest Protection

9. Government Regulation No. 26 of 2008 on National Spatial Planning.

10. Government Regulation No. 42 of 2008 on Forest Planning.

Presidential Regulation 11. Presidential Regulation No. 81 of 2014 on spatial planning of Lake Toba and its

surrounding

12. Presidential Regulation No. 49 of 2016 on the Management Authority of Lake Toba

Tourism Area

Presidential Decree 13. Presidential Decree No. 32 of 1990 on Protected Areas Management

14. Presidential Decree No. 2 of 2014 on the addition of Jasa Tirta 1 Company’s working

area in Toba Asahan river, Serayu Bogowonto River and Jrantunseluna river.

Ministerial Regulation 15. Ministry of Health Regulation No. 416/1990 on the requirements of Water Quality

Supervision.

16. Ministry of Health Regulation No. 907 of 2002 on the Requirements and Supervision of

Drinking Water Quality.

17. Ministry of Environment Regulation No. 111 of 2003 on the Guidance of Requirements

and Licensing Procedures along with the Guidance on Waste Disposal to Water and

Water Sources.

18. Ministry of Environment Regulation No. 28 of 2009 on the capacity of pollution load on

Lake and Reservoir Water.

19. Ministry of Public Work and Public Housing Regulation No. 4 of 2015 on River Area

Criteria and Stipulation

20. Ministry of Public Work and Public Housing Regulation No. 9 of 2015 on Water

Resources Utilization.

21. Ministry of Public Work and Public Housing Regulation No. 10 of 2015 on Planning and

Technical Planning of Water Governance and Irrigation system.

22. Ministry of Public Work and Public Housing Regulation No. 28 of 2015 on the stipulation

of River border line and Lake border line


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F-2

23. Ministry of Public Work and Public Housing Regulation No. 37 of 2015 on the license

of Water and/or Water sources use.

24. Ministry of Environment and Forest Regulation No. 68 of 2016 on Water Waste Quality

Standard.

25. Ministry of Public Work and Public Housing Regulation No. 4 of 2017 on the

implementation of Domestic Water Waste Management system.

North Sumatra Governor Regulation 26. North Sumatra Governor Regulation No. 30 of 2008 on the Management Coordination

Board of Lake Toba ecosystem area.

27. North Sumatra Governor Regulation No. 1 of 2009 on the water quality standard of

Lake Toba in North Sumatra Province.

28. North Sumatra Governor Regulation No. 18 of 2009 on the Preservation Coordination

Board of Lake Toba ecosystem area.

North Sumatra Governor Decree 29. North Sumatra Governor Decree No. 062.05/255/K/2002 on the Preservation

Coordination Board of Lake Toba ecosystem area.

30. North Sumatra Governor Decree No. 614/468 of 2008 on the formation of Asahan -

Toba watershed Management Forum

31. North Sumatra Governor Decree No 188.44/209/KPTS/2017 on Lake Toba trophic

status

32. North Sumatra Governor Decree No. 188.44/213/KPTS/2017 on the Capacity of Lake

Toba pollution load and carrying capacity for Fisheries cultivation.

Regional Regulation No. 7 of 2003 on North Sumatra Spatial Planning is currently (July 2017)

being updated and still in the process of legalization in the Governor’s office.

F.2 List of laws in Bahasa Indonesia

Undang-Undang

1 Undang-Undang Nomor 5 Tahun 1990 tentang Konservasi Sumber Daya Alam Hayati

dan Ekosistemnya;

2 Undang-Undang Nomor 41 Tahun 1999 tentang Kehutanan;

3 Undang-Undang Nomor 32 Tahun 2004 tentang Pemerintahan Daerah;

4 Undang-Undang Nomor 26 Tahun 2007 tentang Penataan Ruang;

5 Undang-Undang Nomor 32 Tahun 2009 tentang Perlindungan dan Pengelolaan

Lingkungan Hidup.

Peraturan Pemerintah

6 Peraturan Pemerintah Nomor 82 Tahun 2001 tentang Pengelolaan Kualitas Air dan

Pengendalian Pencemaran Air;

7 Peraturan Pemerintah Nomor 44 Tahun 2004 tentang Perencanaan Kehutanan;

8 Peraturan Pemerintah Nomor 45 Tahun 2004 tentang Perlindungan Hutan;

9 Peraturan Pemerintah No. 26 Tahun 2008 tentang Rencana Tata Ruang Wilayah

Nasional;

10 Peraturan Pemerintah No. 42 Tahun 2008 tentang Perencanaan Kehutanan;



Final Report

F-3

F-3

Peraturan Presiden

11 Perpres No. 81/2014 – Peraturan Presiden No. 81 Tahun 2014 tentang Rencana Tata

Ruang Kawasan Danau Toba dan sekitarnya

12 Perpres No. 49/2016 – Peraturan Presiden No. 49 Tahun 2016 tentang Badan Otorita

Pengelola Kawasan Pariwisata Danau Toba

Keputusan Presiden

13 Keputusan Presiden Nomor 32 Tahun 1990 tentang Pengelolaan KawasanLindung;

14 Keppres No. 2/2014 – Keputusan Presiden Nomor 2 Tahun 2014 tentang Penambahan

Wilayah Kerja Perusahaan Umum (PERUM) JASA TIRTA I di Wilayah Sungai Toba

Asahan, Wilayah Sungai Serayu Bogowonto, dan Wilayah Sungai Jratunseluna

Peraturan Menteri

15 Peraturan Menteri Kesehatan Nomor 416/1990 tentang Syarat- Syarat Pengawasan

Kualitas Air;

16 Keputusan Menteri Kesehatan Nomor 907 Tahun 2002 tentang Syarat dan Pengawasan

Kualitas Air Minum;

17 Keputusan Menteri Negara Lingkungan Hidup Nomor 111 Tahun 2003 tentang Pedoman

mengenai Syarat dan Tata Cara Perijinan serta Pedoman Pembuangan Limbah ke Air

dan Sumber Air.

18 Peraturan Menteri Negara Lingkungan Hidup Nomor 28 Tahun 2009 tentang Daya

Tampung Beban Pencemaran Air danau dan/atau Waduk;

19 Peraturan Menteri PUPR Nomor 4 tahun 2015 tentang Kriteria dan Penetapan Wilayah

Sungai

20 Peraturan Menteri PUPR Nomor 9 tahun 2015 tentang Penggunaan Sumber Daya Air

21 Peraturan Menteri PUPR Nomor 10 tahun 2015 tentang Rencana dan Rencana Teknis

Tata Pengaturan Air dan Tata Pengairan

22 Peraturan Menteri PUPR Nomor 28 tahun 2015 tentang Penetapan Garis Sempadan

Sungai dan Garis Sempadan Danau

23 Peraturan Menteri PUPR Nomor 37 tahun 2015 tentang Izin Penggunaan Air dan/atau

Sumber Air

24 Peraturan Menteri Lingkungan Hidup Kehutanan Nomor 68 Tahun 2016 tentang Baku

Mutu Air Limbah

25 Peraturan Menteri PUPR Nomor 4 Tahun 2017 tentang Penyelenggaraan Sistem

Pengelolaan Air Limbah Domestik

Peraturan Gubernur Sumatera Utara

26 Peraturan Gubernur Sumatera Utara No. 30 tahun 2008 tentang Badan Koordinasi

Pengelolaan Ekosistem Kawasan Danau Toba

27 Peraturan Gubernur Sumatera Utara Nomor 1 Tahun 2009 tentang Baku Mutu Air Danau

Toba di Provinsi Sumatera Utara;

28 Peraturan Gubernur Sumatera Utara Nomor 18 Tahun 2009 tentang Badan Koordinasi

Pelestarian Ekosistem Kawasan Danau Toba.


– Final Report


F-4

Keputusan Gubernur Sumatera Utara

29 Surat Keputusan Gubernur Sumatera Utara Nomor 062.05/255/K/2002 tentang Badan

Koordinasi Pelestarian Ekosistem Kawasan Danau Toba.

30 Surat Keputusan Gubernur Sumatera Utara No. 614/468 tahun 2008 tentang

Pembentukan Forum Pengelolaan Daerah Aliran Sungai Asahan – Toba

31 Surat Keputusan Gubernur Sumatera Utara Nomor 188.44/209/KPTS/2017 tentang

Status Trofik Danau Toba

32 Surat Keputusan Gubernur Sumatera Utara Nomor 188.44/213/KPTS/2017 tentang Daya

Tampung Beban Pencemaran dan Daya Dukung Danau Toba untuk Budidaya Perikanan

Peraturan Daerah Nomor 7 Tahun 2003 tentang Rencana Tata Ruang Wilayah Provinsi

Sumatera Utara is currently (July 2017) being updated and still in the process of legalization in

the Governor’s office.



Final Report

G-1

G-1

G Water quality data PJT1

Perusahaan Umum Jasa Tirta, or Perum Jasa Tirta 1 (PJT1) is the national corporation for

basin management, responsible for Toba Asahan and other river basins. PJT 1 has recently

started monitoring water quality at 20 sites in the Toba Asahan basin (Figure 3.4), together with

the Sepuluh Nopember Institute of Technology, Surabaya. The water quality data from these

sampling locations were not available at the time of the modelling yet, but have been included

here for comparison. Table G.1 shows the values of several parameters measured at the

sampling stations displayed in Figure 3.4.

Table G.1, Results of water quality (in mg/l) at 8 points by PJT1 in 2016 and 2017.

Para

mete

r

Wate

r q

ua

lity

sta

nd

ard

Location

date

Refe

ren

ce

po

int

Bakkara

Nain

gg

ola

n

Hil

ir D

an

au

Sim

alu

ng

un

Sip

iso

-pis

o

Dair

i

To

mo

k

DO

May ‘16 4 6.6 6.6 - 4.8 5.4 5.2 4.3 4.7

Sep ‘16 4 - - - 7.5 6.6 6.4 6.5 5.6

Jan ‘17 4 5.6 5.6 5.5 5.0 5.5 4.8 5.1 5.2

Apr ‘17 4 5.6 5.2 5.4 5.3 5.4 5.1 4.9 5.1

Jul ‘17 4 4.9 4.2 4.0 4.0 4.8 4.2 4.0 4.0

BO

D

Mei ‘16 3 5.1 3.9 - 3.8 9.2 4.9 9.4 9.0

Sep ‘16 3 - - - 3.2 3.1 3.2 3.4 3.2

Jan ‘17 3 6.5 5.5 13.6 6.3 4.7 4.3 4.9 12.0

Apr ‘17 3 3.89 6.91 2.54 3.20 3.59 4.75 2.01 3.54

Jul ‘17 3 5.55 4.55 4.80 6.35 6.30 7.35 4.45 4.75

CO

D

Mei ‘16 25 17.28 7.70 - 7.04 21.23 13.10 22.30 20.27

Sep ‘16 25 - - - 7.15 9.32 8.62 8.95 8.51

Jan ‘17 25 23.08 23.56 38.91 21.17 14.12 12.34 14.80 37.62

Apr ‘17 25 14.37 29.63 8.30 13.02 12.67 12.94 7.56 14.66

Jul ‘17 25 18.22 17.32 15.37 16.31 17.40 16.39 12.92 14.48



Final Report

H-1

H-1

H Methodology of stakeholder assessment

H.1 Theoretical framework

H.1.1 Stakeholder roles and functions

In accordance with the Indonesian water law39 as laid out in the Strategic Plan (Pola) and River

Basin Plan (Rencana), five important stakeholder roles can be identified (Figure H.1):

Figure H.1, Stakeholder roles as identified in the 2013-2015 TKPSDA process.

1. Regulator – the government, creating an enabling environment for efficient and effective

water resource management (WRM). This is called the “regulator” function because the

main instruments employed are laws and regulations to guide the activities of other parties

involved in WRM including management and monitoring of water quality.

2. Coordinator – the stakeholder that must achieve a balance between the other functional

categories to ensure sustainable utilization and preservation of resources as well water

safety (protection from the destructive power of water). Coordination also involves non-

water organizations whose activities have a direct or indirect impact on water resources,

such as Kementerian Lingkungan Hidup dan Kehutanan (KLHK, the Ministry of

Environment and Forestry) for conservation and pollution control; Kementerian Energi dan

Sumber Daya Mineral (ESDM, the Ministry of Energy and Mineral Resources) for licensing

of groundwater abstraction; and Badan Pertanahan Nasional-Kementerian Agraria dan

Tata Ruang/ (BPN-ATR, the National Land Agency at the Agrarian and Spatial Planning

Ministry) for flood management through spatial planning and land-based infrastructure.

3. Operator – institutions in charge of the daily operation of infrastructure assets to manage

and monitor water resources, including water quality. In most basins, the operator function

is carried out at provincial and district-level government level.

39 Water Resources Law 7/2004 and Regulation 4/2008 have expired in 2015. The new law and regulation are still in the

process of being formally approved by parliament. For this section, the concept text has been used.


– Final Report


H-2

4. Developer – any party involved in the development of physical infrastructure that offers

protection from or enables the utilization of water, or protects water as a resource in terms

of quantity and quality. Examples include dams, levees, irrigation canals, water supply or

sewage treatment facilities, aqueducts, and sewers. Generally, this function is carried out

by (semi-) government or publicly-owned organizations such as Pengelolaan Sumber Daya

Air (PSDA, water resources management), Perusahaan Daerah Air Minum (PDAM, the

regional water supply company), and Perusahaan Umum Jasa Tirta (PJT, national

corporation for basin management).

5. User – large-scale users of water as well as individual users, e.g., individual farmers. Large-

scale users may in turn represent individual consumers. Relevant examples are water

supply companies, irrigation systems, and hydropower plants. The users comprise not only

government or state-owned enterprises but also private organizations such as breweries,

bottlers, and paper mills.

This stakeholder concept proved very effective in the stakeholder processes of Kementerian

Pekerjaan Umum Dan Perumahan Rakyat, (PUPR, the Ministry of Public Works and Housing)

and has been widely accepted in Indonesia. The concept is especially strong when combined

with the “expected/appointed role/responsibility” of the different stakeholders in the process -

in this case, the relation/role/responsibility for the WQ roadmap for Lake Toba. Interestingly, in

the Indonesian water law, no strict distinction is made between water quality monitoring and

water quality management. In the roles of regulator and operator water quality management

and monitoring are mentioned together as two aspects of one responsibility.

For each key point and non-point source of pollutants, however, the key stakeholders and the

legal, institutional and PE context are different. The legal and institutional setting may be similar

for each of the water quality interventions as it does not depend much on the different sets of

treatment measures. For implementation and maintenance of most of the WQ measures, the

lower level administrative Kecamatan (sub-district) level is crucial, and thus it is important to

determine the role of these local administrations. A total of 46 Kecamatan are included in the

assessment (Figure H.2).



Final Report

H-3

H-3

Figure H.2, Lake Toba Area related sub-districts (kecamatan).

H.1.2 Social network analysis

Social network analysis defines and analyses the relationships that organizations or individuals

have with each other by focusing on the positions and structural patterns of the actors. It can

highlight which stakeholders are important for influencing policy, initiating actions or facilitating

information and knowledge transfer. The analysed network perspectives can improve the

effectiveness of a network (intra-organizational or inter-organizational) by identifying points of

misalignment and accelerating collaboration in the right places. It can also help determine

whether certain organizations and functions are achieving the connectivity required for desired

results and identify and track intervention strategies if they are not. Network analysis can also

highlight top performers in a network and determine reasons for success and replication factors

for low performing actors. Some key characteristics of the network map (NetMap, see below)

are the ability to i) identify who the stakeholders are, together with their roles and relationships

with each other; ii) identify misalignment in the communications between stakeholders; iii)

identify a potential leading champion in water quality monitoring and management; and iv)

prioritize actions based on the highest negative influences in water quality management.

The NetMap exercise is only effective if the right stakeholders are present to map as

comprehensively as possible the stakeholders and flows. The resulting social network analysis

maps represent a subjective reality. For example, during the exercise, the participant who

represented the Basin Management Center Sumatra II (BWS Sumatera II) was actively

involved and participating, showing his keen interest in the WQ Roadmap for Lake Toba. Thus,

it may be shown in the NetMap that BWS Sumatera II had many more connections or linkages

compared to the linkages of other actors, while in reality this may be the same.


– Final Report


H-4

Hence, it is difficult to achieve quantitative results with social network analysis. However, just

because the map does not represent an objective reality, it does not mean that stakeholders

are not making decisions and acting based on that reality. The network map should be seen as

a starting point for the understanding social landscape connectivity. The social network analysis

produces an important map to guide governance interventions. Moreover, the process provides

an important opportunity for reflection. The discussions that arise from the act of producing the

maps are an essential part of the learning process. It is, therefore, important to record

reflections and be cognizant of what has been learned during the process and also what

knowledge gaps still exist.

The process gives an opportunity to the participants to think about their own programs and

initiatives related to the lake management. For instance, at the second exercise, the provincial

and district services were prompted to think about who they should go to for direction, advices

and guidance on their planned activity.

H.2 Methods and tools

H.2.1 NetMap

The relationships between actors influencing the management of Lake Toba’s water quality

were defined and analysed with NetMap. The stepwise approach in NetMap (Figure H.3) was

elaborated into specific questions that would help increase understanding of the positions and

structural patterns of the stakeholders around Lake Toba.

Figure H.3, The six stages of mapping social network analysis in NetMap.

The specific guiding questions used in the stakeholder meetings were:

1. Who influences the water quality monitoring and management in Lake Toba?

2. Who are the stakeholders involved?

3. What are the types of links and how strong? (Authority, Funding, Information, Advice,

Advocacy, Pressure, Friendship)

4. How much interest do the stakeholders have in the issue?

5. How much influence do the stakeholders have?

The first question is defined as ‘who influences,’ rather than ‘who should be involved’. This

helps to identify those stakeholders that may have positive as well as negative impacts on the

water quality management. In the identification of stakeholders, all participants brainstorm

together and then create categories according to functions and roles.

Two NetMap exercises have been organized with two different groups to define and analyse

the relationships between actors influencing the management of Lake Toba’s water quality. The

1. Define Question

2. Identify Actors

3. Allocate Links

4. Assign Interest

5. Assign Influence

6. Input data



Final Report

H-5

H-5

first net map exercise was conducted in Jakarta on May 17, 2017 with the reference group,

where about 20 representatives actively participated in the process. The second net map

exercise was done in Laguboti, North Sumatra on June 14, 2017, with both the reference group

and participants at the local level, including representatives from provincial and district

agencies, local NGOs, the private sector, and local communities. The second net map exercise

was based on the result of the first net map exercise. There were about 50-60 participants at

this meeting. The involvement of the reference group and the participants in both meetings

provided an opportunity for a participatory approach. It allowed reflection and discussion on

many elements of the management of Toba Lake Water Quality, and contributed to a broader

understanding of the dynamics in the management of water quality in Toba.

To identify the actors that are involved in Lake Toba water quality management, a brainstorm

on paper was held with all the actors, after which some categories were created. Alll the

stakeholders with a similar role were put in the social landscape of Lake Toba in the same

category. These categories include: national government agencies, sub-national government

agencies, non-governmental organizations, local communities, academic institutions, and the

private sector.

Subsequently, the stakeholder names were written on post-it notes; each category of

stakeholders was assigned a single post-it notes colour. The list of stakeholders was confirmed

by the participants of the reference group and continued to be added throughout the exercise.

In the resulting map, red represents national government agencies, orange represents

subnational government agencies, purple represents non-governmental organization, green

represents local communities, pink represents academic institutions, and blue represents the

private sector and state-owned enterprises.

These post-it notes were then put on a dry-erase glass wall (Figure H.4). Once the actors and

actor groups had been defined, two important flow types were identified between the actors

relevant to Lake Toba water quality: authority and information (or coordination). These flows

were then drawn on the glass wall. Blue-coloured flows represent authority and red flows

represent information (or coordination). Formality of flows was represented with solid lines for

formal flows and dotted lines for the informal ones. Influence of the actors was determined by

the size of the circle of each actor. During the discussion, the participants also identified

stakeholders that have negative interests. The data were then entered into NodeXL and further

analysed.


– Final Report


H-6

Figure H.4, NetMap Exercise with the Reference Group

There are many stakeholders who influence the water quality management of Lake Toba.

During the NetMap exercises, the participants were asked to think about the sources of

pollutants and the influencers in Lake Toba (such as aquaculture, wastewater, water supply,

solid waste, agriculture, erosion reduction, hydropower, and road infrastructure). Once they

started to think about these pollutant sources, they added and considered more actors

throughout this exercise.

Results from the collaborative NetMaps were analysed in NodeXL Basic software to produce a

quick perception of the social network visual. Node XL is fairly straightforward since it is an

add-on to the Excel program. Information can be copy-pasted from a previous Excel document

or written directly into the Node XL template. The sheets are organized separately for “Edges”

and “Vertices.” The headings of the columns are self-explanatory. NodeXL is user-frienly with

actors as input in a landscape on the “Vertices” sheet, and the relationships on “Edges” sheet.

Users can easily adjust the visual properties of the Vertices and Edges: the color, shape, width,

style, and visibility of each “Edge” and “Vertice” to show groups or similar interactions (Figure

H.5). Data can be shown as a circle or a vertical sine wave—each providing new perspectives

on connectivity between actors.



Final Report

H-7

H-7

Figure H.5, Example of stakeholder map visualisation (NetMap) in NodeXL software.

H.3 Stakeholder perceptions

H.3.1 Observations from NetMap discussions

Participants in the discussions on the NetMaps had many observations and suggestions that

are summarized below.

The discussions and resulting NetMaps illustrate that management of water quality in Lake

Toba is complex and dynamic. It also shows that to foster a change or intervene in the pollutant

control management, there are different sets of actors involved. For example, to enact change

in agriculture waste, the Agriculture District Services (or Dinas Pertanian) should be involved

because they could coordinate and give guidance to the Agriculture Communities (or

Komunitas Tani), while to manage pollutant loads from aquaculture, it has to go through

Fisheries Services (or Dinas Perikanan).

The maps show that the actors with many hubs (highly connected network) are mostly at the

central level. However, participants indicated that the many linkages connected to the actors

do not necessarily translate into a similar number of programs by each actor. Participants

indicated in the discussion that, in principle, the sub-national government should have more

roles in influencing management decisions of Lake Toba water quality (compared to the

national government). This is shown once interest and influence was assigned to the actors.

The participants agreed to assign sub-national actors with the highest influence, which is

reflected in Figure 4.1 and Figure 4.2 by the size of the circles.

At the second exercise at local level, the participants proposed to adjust the map by separating

the levels of actors at the subnational level into provincial level and district level. This was done

to better visualize the connection between levels, and where gaps could potentially exist. The

second map shows that there are few connections at the sub-national levels (both at the

provincial and district levels, but especially at the district levels), to the rest of the actors on the

map. It also seems that many of their connections are mostly with other governmental entities,


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and rarely with the private sector, academia, or others. It becomes more apparent that the sub-

national government, especially at the district level, often works in isolation – there is little

collaboration between agencies in different sectors, nor between various levels. Thus, this

might confirm findings from the first exercise, that the central level actors appear to be more

vocal and in practice, are more involved in terms of the management of Lake Toba.

Not shown in the maps are the assigned interests of the actors in relation to the water quality

management of Lake Toba. During the discussion, the participants brought up some of the

actors that may have very little interest in improved water quality management or pollution

control. They mentioned: aquaculture farmers (PT Aquafarm Nusantara, PT Suri Tani Pemuka),

hotel owners and household owners, agriculture and livestock farmers, forest enterprises, as

the biggest negative influencers (or polluters) of the water quality of the Lake Toba. Others

such as miners, lake transportation actors were also mentioned as having negative influence,

but with less prominent influence as the former actors.

There are many coordinating bodies (Forum DAS, TKPSDA, and BKEPDT) to manage the

water quality of Toba but the map does not show any clear leader or champion. These

coordinating bodies are also initiated by the central ministries and/or provincial governors, with

little focus given at the district levels, even though they were intended to accommodate district

services as well. In addition to these coordinating bodies, there are many hubs (or connections)

between actors, but no leading actors who supervise the management. The hubs indicate the

potential of these actors to be the champions of change toward the better management of Lake

Toba water quality. However, the hubs do not directly translate to the many initiatives by these

actors. Rather, they show that there are flows of information in the actors, but initiatives are still

lacking, especially from the sub-national level. The participants at both exercises confirm the

need to have a clear leader and champions. It is important to note that a champion or

management leader ideally has a capacity and linkage to many different types of institutions

and at different levels.

Many of the civil society organizations (CSOs), such as Yayasan Pencinta Danau Toba

(YPDT), WALHI, Alusi Tao Toba, KSPPM, and local communities, represented through

DAERMA (Local Fishermen’s Association), expressed that often when their aspirations are not

well-received by the district services, they would go directly to the relevant ministries at the

national level. It might be worth to explore the CSOs’ potential to guard the management

process of Lake Toba or be an agent of change, considering their active participation and

monitoring on the issue, and their close relationships (formal and informal) with different kinds

of stakeholders. From the discussion at the second workshop, the CSOs emerged as having

been engaging with each other as well as with the local communities, and as having been

pressuring many changes to the government and to private sector as well.

H.3.2 Summary of stakeholder comments

According to the stakeholders, good regulations are available but not always coordination, while

implementation is not being monitored systematically. These have to be followed up by clearer

guidance to be easy implemented (example: Spatial Plan in Province level has to followed up

by Spatial Plans in District level or to be elaborate in technical and implementing guidance).

Communication of new regulations could also be improved. Monitoring in implementation of

regulations has to be enforced and could be done by overlaying actual conditions and

requirements in regulation. Instruction letters would be useful for this and help guide program

implementation (especially in putting budget for implementation; example SSE Home Affairs).



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A contribution factor would be to base the issuance of permits on technical recommendations

by relevant district agencies.

During the interviews conducted with provincial and national institution as part of this

assessment, various stakeholders (in particular PU and forestry) indicated that broad

cooperation and acceptance of the recommendations by the Districts is required for successful

implementation of the WQ Roadmap. This includes clear support and direction by the Ministry

of Home Affairs, which has the mandate and authority to give direction to the Districts. Since

1998, most of the proposed programs and interventions lacked this support, according to the

stakeholders. Key members of the Reference Group consider this lack of local linkage and

embedment (with also no “active” agreement on the National level with the Ministry of Home

Affairs) as one of the main “dysfunctional features” or “bottlenecks” for the implementation of

their different well-formulated and urgently-required programs to safeguard and improve the

environment and water quality of Lake Toba.

Similarly, while officially (de jure; chapter 3) institutions have a mandate in water quality, in

reality (de facto; chapter 0) institutions with clear mandates do not necessarily have the most

impactful program. As a result, there is an institutional gap as no organization acts as a leader

in water quality management: not in monitoring, and not in implementation. Community-based

organizations could play a role, but need adequate support.



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I-1

I Comprehensive list of stakeholders involved in Lake Toba water quality

Table I.1 presents all stakeholders, identified during the stakeholder consultation process,

that use or influence Lake Toba. Those marked as regulator and/or operator, play a role

in water quality monitoring.

Table I.1, Institutions with a stake in Lake Toba, along with their roles (members of the Reference Group are

marked in yellow).

Institutions/ lembaga

stakeholder role

Regu

lato

r

Opera

tor

Develo

per

Coord

inatio

n

User

NATIONAL

Coordinating Min. of Maritime Affairs R C

Coordinating Min. of Economy R

Min. of Tourism R C

Min. of Home Affairs (cq DG Regional Development) R

National Planning Agency/Bappenas (Sub Dit. River, Coastal, Reservoir, Lake)

R C

Min. of Finance R

Min. of Environment and Forestry R

Min. of Agraria and Spatial Planning R

Min. of Public Works and Housing R O D

- Development Body Region Infrastructure (BPIW) R C

- Dit. Gen Human Settlements - PPLP R

- Dit. Gen of Bina Marga R

- Dit.Gen Water Resources (cq Dit Rivers and Coastal) R

- Center of Dam/reservoir (cq Lake, Situ, Embung division)

R D C

- Center of raw water and ground water R

- BWS Sumatera II R O D

- Center Research of Water Resources R

Min. of Transportation R

Min. of Marine Affairs and Fisheries R

Min. of Energy and Mineral Resources R

Min. of Manpower R

Min. of Aparatur State Utilization (bureaucracy reform) R

Secretary of Cabinet/Presidential Chief of Staff office R

Min. Of Agriculture R


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stakeholder role

Regu

lato

r

Opera

tor

Develo

per

Coord

inatio

n

User

Min. of Industry R

LIPI Research Center of Limnology R

BPPT R

Min. State Own – PJT1 O

Badan Meteorologi Klimatologi & Geofisika (BMKG) O

Badan Nasional Penanggulangan Bencana (BNPB) R O

Badan Otorita Pariwisata Danau Toba O D C U

PROVINCE

Governor of North Sumatra R

Regional Planning Agency/Bappeda Prov R C

Prov. Forestry R O

Prov. Environmental Services R O C

Prov. Water Resources Services R O

Prov. Human Settlements TR Services R O

Land Cadaster/bpn atr Prov R O

Prov. Services of Transportation R O

Prov. Agriculture R O

PPL (Petani Penyuluh Lapangan) O

Prov. Fisheries services R

PPL (Penyuluh Lapangan Perikanan) O

Prov.. Tourism Services R O

Badan Penanggulangan Bencana Daerah (BPBD) O

Badan Pengelola Geopark Kaldera Danau Toba O C U

KABUPATEN/DISTRICTS (8)

Head of District R

Regional Planning Agency/Bappeda Kab. R C

Kab. Forestry R O

Kab. Environmental Services R O C

Kab. Water Resources Services R O

Kab. Human Settlements TR Services R O

Land Cadaster/bpn atr District R O

Kab. Services of Transportation R O

Kab. Agriculture R O

PPL (Petani Penyuluh Lapangan) O

Kab. Fisheries services R



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stakeholder role

Regu

lato

r

Opera

tor

Develo

per

Coord

inatio

n

User

PPL (Petani Penyuluh Lapangan) Perikanan O

Kab. Tourism Services R O

STATE OWNED, private sector, civil society, NGO

Perhutani O U

Masyarakat Adat (Batak) U

AMAN (Aliansi Masyarakat Adat Nasional) U

WALHI North Sumatra U

Yayasan Pencinta Danau Toba U

Community Masyarakat Peduli Danau U

Forum Komunikasi Danau Toba U

KSM (Kelompok Swadaya Masyarakat) U

PKK (Pembinaan Keluarga Sejahtera) U

Forest communities (upstream conservation) U

Other NGOs (KSPPM, Alusi Tao Toba, Hutan Rakyat Institute)

U

Fishermen’s Association (DAERMA) + others U

Tourism communities U

Rivers communities U

Universities/Perguruan Tinggi – USU (North Sumatra University) - UNIMED, Nomensen - Universitas Simalungun

U

URI (University Rhode Island) U

Electricity company: INALUM + PLN + others U

Bajradaya Sentranusa (BDSN) U

Industrial group/area industry U

TPL (Toba Pulp Lestari) U

PT Aquafarm Nusantara U

Suri Tani U

Kelompok Tani U

Kelompok Pembudidaya Ikan U

Asosiasi Peternak U

Irrigation Commission/Komisi Irigasi U

WUA/Group WUA/Federation WUA U

Komunitas transportasi air U

Penambang Galian C U

DMO Toba U

Public Water Supply Company/PERPAMSI - PDAM U

Coordination Body


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stakeholder role

Regu

lato

r

Opera

tor

Develo

per

Coord

inatio

n

User

Coordinating Body on Capital investment/BKPM C

National Water Resources Council/Dewan Sumber Daya Air Nasional

C

Provincial Water Resources Council/Dewan Sumber Daya Air Provinsi

C

BKPEDT C

Basin Council/Tim Koordinasi Pengelolaan Sumber Daya Air Wilayah Sungai

C

Forum DAS (Daerah Aliran Sungai) C



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J Detailed methodology lake assessment

J.1 Sumatra Spatial Model

J.1.1 Introduction

Strong demographic changes and increasing economic activities over the next (25) years

will stretch available resources of land, water and environment on many Indonesian islands

to the limit. Settlement and non-adapted land-use practices up to now have had a strong

impact on many sectors. For the water sector adverse impact on runoff, such as higher

peak flows and lower low flows, are being experienced, resulting in increased flooding and

shortages in water supply. For agriculture, the high demand for new urban land will result

in a loss of valuable irrigated land. In these circumstances, an effective protection through

zoning and regulation will be necessary to protect the interest of different sectors and

allocate urban development to less harmful locations. For water such conservation policy,

via a spatial zoning policy, should prevent further degradation of water resources and

upgrade as much as possible existing adverse conditions.

The spatial law Nr 26 (2007), with its orientation to sustainable resource management and

protection provides a framework to develop and implement spatial planning within

Indonesia (Figure J.1). For example for the water sector, the New Spatial law specifically

addresses conservation specifies as a minimum target of maintaining 30% of forest in each

water catchment area (DAS). Similar land claims or zoning policies are being specified for

other sectors like agriculture, forestry, housing, and environment. The Ministry of

Agriculture has adopted law nr. 41 (2011) on food security. The land requirements from

relevant sectors should be integrated in the spatial plans as many regions in Indonesia

suffer from a shortage of suitable land resources.


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Figure J.1, Land use according to Rupa Bumi (BIG).

The basis for the land use data in the Sumatra Spatial Model is the Peta Rupa Bumi

Indonesia from BIG (Figure J.2). This dataset however is often out of date and in practice

corrections have been made for the paddy fields (based on the 2010 Peta Audit Baku

Sawah from the Ministry of Agriculture) and the urban area (Google Maps). In particular, it

was found that some of the categories near Lake Toba needed correction to get

representative starting situation for the land use per village (desa).

If large land claims are developed for a sector then this will have strong impact on other

land consuming sectors (e.g. urbanization will grow at the expense of other sectors). To

analyse these effects a quantitative approach is needed that models spatial changes in

population, employment, urban land-use and associated changes in land-use. Such a

spatial model, the Sumatra Spatial Model, is presented here.



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J-3

Figure J.2, Lake Toba Region Spatial Plan (Presidential decree 81/2014).

The first version of the spatial model was developed for the island of Java: the Java Spatial

Model or JSM. JSM 1 was first developed under the BWRMP project in 2001-2002 and

further developed in the “Space and Water” project (2006-2008), see also Vernimmen

(2015). The latter is a spatial planning initiative covering all of Java, to support integration

of spatial planning with water resources planning, and JSM 1 proved its usefulness there.

Coverage of whole Java is necessary to reflect the migration flows on Java. In the 6Ci

project for the ADB the model has been updated to JSM 2.0, 2.1 and 2.2. The spatial

model provides internally consistent future projections of:

• The spatial distribution at village level of the population and employment;

• The urban area growth needed to accommodate human activities; and

• The land-use changes caused by the urban area growth.

JSM provides in particular a consistent projection of urban/rural land-use with important

consequences for total water demand, water quality and ecology, based on:

• Socio-economic projection of population/employment at district (kabupaten) level based on economic growth scenarios,

• Spatial allocation of population and land-use for Java at village (desa) level,

• Calculation of impacts, such as water demands, and pollutant emissions at different geographic levels (the River Basin Territories or parts thereof; Water districts; province; districts, sub-districts and villages). The calculation is based on existing Ministry of Public Works (MPW) guidelines for river basin studies.

In 2015 and 2016 the spatial model was applied to Sumatra (SSM) in the Sumatra Water

Resources Strategic Study and to Sulawesi in the Sulawesi Water Resources Strategic

Study (SulSM).


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J.1.2 Land use changes

The on-going transformation of non-urban area into urbanized land is the result of

developments in spatial markets like the housing market, labour market or transport

market. These markets change under influence of several interacting driving forces;

important drivers are demographic and socio-economic drivers. A good understanding of

these drivers, how they are going to develop and differ among regions, is important for

predicting future urban land-use. Demographic drivers are especially important to project

future residential land demand. Key drivers for additional urban land-use are:

• Domestic land use change is caused by: o Population growth; o Household size reduction; o Increasing use of land resources per household as wealth grows.

• Municipal and industrial land use is caused by: o Economic growth; o Employment growth; and o Change in economic structure

These drivers of land use steer the design of the Sumatra Spatial Model (Figure J.3). The

key design principles are:

• Two step approach to capture the different spatial trends of centralization at an interregional (kabupaten) level and suburbanization (or decentralization) within a region (desa level);

• The modelling is dynamic and uses time steps of one year; this reflects the incremental nature of spatial changes and enables to model the time path dependency of developments;

• Key feature of the model is its spatial detail, the model is capable of calculating the impacts on the spatial distribution of residents/employment and associated land-use changes of different socio-economic (or demographic) scenarios and/or policies at the level of desa units.



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Figure J.3, Overview of the Sumatra Spatial Model, as originally applied to Java.

J.2 Modules and variables

The model consists of three modules (Figure J.4):

Module 1: Regional module

• Calculates at district (kabupaten) level population growth and migration. Sum of population of all districts on the island (Sumatra) is kept equal to available official (BPS/BAPPENAS) population projections and economic growth scenarios.

Module 2: Land-use allocation module

• Allocates space demand at kabupaten level to desa level based on preferences of residents and zoning policy.

Module 3: Spatial development & water resources indicators

• Land-use changes at different administrative levels

• Water resources impacts

• Agricultural and food supply impacts

• Ecological Impacts

Spatial Plan

Kabupaten

Socio-economic

model

Desa land

allocation model

Start population,

employment, GDP

Postprocessor

impact indicators

Drivers:

Java population. Growth etc

Start land

use data

Input

parameters

Kabupaten results

Desa results

Impacts

Administrative regionWatersheds

Water districts

etc

Tim

e l

oop


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Figure J.4, Application concept for the Sumatra Spatial Model.

J.2.1 Regional or Socio-economic sub-model

The socio-economic sub-model handles the projections of population and industrial

activities. It uses four model sectors: population, employment, housing and industry. The

idea is that these sectors represent the major urban development processes. Between the

three economic sectors (agriculture, industry and services) there are various feedbacks

that influence the rates of change within the sectors. The distribution of the (growing)

population depends on the attractiveness of an area (e.g. number of available jobs) and is

constrained by limited resources (e.g. land). These two assumptions mean that growth is

limited in the end by available land.

The different model sectors are related to each other, values for model variables in one

sector will affect the values of model variables in other sectors. For example construction

of new industrial structures will result in more jobs. New jobs will attract people from

outside the region and the immigration will increase. A larger population size will result in

a higher demand for housing and construction of new houses will be the result. This growth

loop will be limited by the availability of land.

The sub-model predicts population developments (growth & migration) at the district

(kabupaten) level, based on a basic linkage between economic developments and

population developments. Explanatory variables are developments in gross regional

product, employment, regional features (e.g. land availability) and proximity. Key data



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source for calibration of this sub-model is the Dalam Angka data and Census 1990/2000

data of BPS. This has been collected for the time period 1990-2010. At district (kabupaten)

level census 2010 data were obtained for calibration.

The regional model consists of a simple shift/share procedure to allocate province level

economic growth scenarios over the districts. A more elaborated procedure (shift/share in

combination with regional explanatory variables) calculates the population developments

for each of the districts and explains the differences in development between the districts.

J.2.2 Spatial allocation sub-model

The spatial allocation sub-model predicts how the calculated growth of activities of the

social-economic sub-model is spatially distributed within the study area and what the

resulting land-use changes are. The allocation model distributes the land demand of the

social-economic model to different parts within the region. The available land in the

different areas (cells) will be subject of inventory and the attractiveness of this area for the

land demanding activities. The available land for the allocation process depends on the

land-use in the area. The attractiveness of an area for a specific activity is a combination

of the characteristics of the area and the preferences of the activities. This parameter is

called the attractiveness potential of an area. Every time step the new activities are

allocated to the areas. After the allocation the new situation will be stored in the database

and will function as starting point of the next time step. An overview of the applied

attractiveness criteria is given below:

1. Accessibility: In almost all spatial models the accessibility of a spatial unit plays an

important role in the allocation of functions. Good accessible areas are attractive as location for residential and industrial land use. The accessibility criterion gives a value for how far it is from the center of a cell to the closest main road. The accessibility is normally calculated as the average time needed to travel from inside the desa to the main road. Due to lack of time and available data the indicator is based on four accessibility classes.

2. Access to work: This indicator represents the accessibility of work from a certain

location. In other words are there enough jobs within a reasonable travel time. This requires a travel time matrix from a transport model. The Lake Toba model does not use this indicator.

3. Proximity (gravity criterion): This criterion is a parameter for the distance of an area to

urban and economic activities. This criterion refers to spatial regularities as movement-minimization and the tendency to agglomerate. The idea behind this criterion is that an area close to urban or economical centers is more attractive than an isolated area that is far away (see the example of Java in Figure J.5). This is similar to attractive forces of high density mass or gravity. Variables included in this criterion are the distances between areas, the number of inhabitants and jobs in the area.


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Figure J.5, Example of proximity indicator for Java.

4. Planning zones, governmental influence: Planning zones are spatial zones defined by

the government where specific land-use plans or restrictions exist. The knowledge of which area is in which planning zone can be obtained with an overlay analysis. The importance of a planning zone for a land demanding function can be managed in the weight set. For example an area within the zone where industrial development is allowed will have a positive value for this criterion in the allocation of new industries. Restriction of urban development, e.g. for reasons of food security, will have a negative value for the attractiveness for housing.

5. Land price and land development cost: Due to limitations in available data the indicator

is based on six classes. Each class represents a group of land price and land development costs. This indicator is a proxy for land suitability for urbanisation.

6. Attractivity or aesthetic value: The indicators mentioned above result in the attractivity

indicator for each desa. By giving each indicator a weight and making a weighed summation the attractivity for each desa for housing and industry is calculated.

J.2.3 Postprocessor for space, water and agricultural indicators

This sub-model calculates indicators as inputs to Basin Water Resources Management

Planning and other sectoral resources impact assessments. It is described in more detail

in the next section. Outputs of the sub-model are:

A. Spatial indicators (directly from the allocation module):

• Population and population density

• Fraction of areas by land use class

B. Water demands:

• Domestic Municipal and Industrial demand (DMI)

• Irrigation

C. Wastewater emissions (BOD):

• Domestic, Municipal and Industrial emissions

• Irrigated paddy



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D. Biodiversity:

• Mean species abundance (MSA) loss due to urbanisation

E. Rice, vegetable and palawija crop production, consumption and self-sufficiency

J.3 Spatial results by compartment and year

Table J.1, Overview of spatial results in 2018, 2022 and 2042 for Lake Toba as a whole.

Variables Whole Lake

2018 2022 2042

Metropolitan population 0 0 0

Large town population 0 0 0

Medium town population 0 0 0

Small town population 0 0 0

Kecamatan city population 42,468 43,547 46,896

Desa population 438,622 475,637 585,531

Employment 209,528 223,243 338,761

Households 118,610 129,903 173,747

Housing (ha) 10,964 12,155 16,628

Other buildings (ha) 1,534 1,751 4,105

Rainfed paddy (ha) 0 0 0

Technical Irrigated Paddy (ha) 17,188 17,062 16,443

Semi-technical Irrigated Paddy (ha) 11,459 11,374 10,962

Other agriculture (ha) 80,397 79,876 77,480

Grass/Other (ha) 10,871 10,748 10,243

Shrub (ha) 54,168 53,950 52,831

Forest (ha) 62,406 62,305 61,795

Ponds (ha) 0 0 0

Plantation (ha) 32,627 32,407 31,403

Water (ha) 3,575 3,575 3,575

Total urban area (ha) 12,497 13,906 20,732

Total irrigated paddy area (ha) 28,647 28,436 27,405

Sum of remaining area available for land use change (ha) 197,534 196,125 189,299

Total area (ha) 294,052 294,052 294,052

Total population 481,090 519,184 632,426

HouseAreaNeeded (ha) 0 0 0

IndustryAreaNeeded (ha) 0 0 0

HouseAreaVacated (ha) 0 0 0

IndustryAreaVacated (ha) 0 0 0


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Table J.2, Overview of spatial results in 2015, 2018, 2022 and 2042 for two compartments of Lake Toba.

Variables North South

2018 2022 2042 2018 2022 2042

Metropolitan population 0 0 0 0 0 0

Large town population 0 0 0 0 0 0

Medium town population 0 0 0 0 0 0

Small town population 0 0 0 0 0 0

Kecamatan city population 19,138 19,770 21,740 23,330 23,777 25,155

Desa population 124,803 137,582 175,930 313,819 338,055 409,600

Employment 65,208 69,478 105,950 144,321 153,765 232,812

Households 35,522 39,133 53,465 83,089 90,770 120,282

Housing (ha) 3,712 4,323 6,635 7,252 7,832 9,992

Other buildings (ha) 521 622 1,693 1,012 1,130 2,411

Rain-fed paddy (ha) 0 0 0 0 0 0

Technical Irrigated Paddy (ha) 2,187 2,156 2,012 15,001 14,905 14,431

Semi-technical Irrigated Paddy (ha)

1,458 1,438 1,341 10,001 9,937 9,621

Other agriculture (ha) 21,592 21,331 20,188 58,805 58,545 57,292

Grass/Other (ha) 2,938 2,847 2,485 7,933 7,901 7,758

Shrub (ha) 17,330 17,218 16,652 36,838 36,732 36,180

Forest (ha) 27,005 26,933 26,565 35,401 35,373 35,229

Ponds (ha) 0 0 0 0 0 0

Plantation (ha) 3,632 3,522 3,061 28,995 28,885 28,342

Water (ha) 1,626 1,626 1,626 1,949 1,949 1,949

Total urban area (ha) 4,233 4,945 8,329 8,264 8,961 12,404

Total irrigated paddy area (ha) 3,645 3,594 3,353 25,002 24,842 24,052

Sum of remaining area available for land use change (ha)

53,089 52,378 48,994 144,445 143,748 140,305

Total area (ha) 90,217 90,217 90,217 203,835 203,835 203,835

Total population 143,941 157,352 197,670 337,149 361,831 434,756

HouseAreaNeeded (ha) 0 0 0 0 0 0

IndustryAreaNeeded (ha) 0 0 0 0 0 0

HouseAreaVacated (ha) 0 0 0 0 0 0

IndustryAreaVacated (ha) 0 0 0 0 0 0



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Table J.3, Overview of spatial results in 2015, 2018, 2022 and 2042 for four compartments of Lake Toba:

North and South 1.

Variables N S1

2018 2022 2042 2018 2022 2042





Kecamatan city population 19138 19770 21740 4844 4960 5317

Desa population 124803 137582 175930 35847 38672 47115

Employment 65208 69478 105950 20666 22026 33413

Households 35522 39133 53465 10130 11094 14791

Housing (ha) 3712 4323 6635 1021 1088 1337

Other buildings (ha) 521 622 1693 174 190 362


Technical Irrigated Paddy (ha) 2187 2156 2012 944 942 930

Semi-technical Irrigated Paddy (ha) 1458 1438 1341 629 628 620

Other agriculture (ha) 21592 21331 20188 11600 11551 11302

Grass/Other (ha) 2938 2847 2485 1543 1539 1518

Shrub (ha) 17330 17218 16652 5652 5632 5529

Forest (ha) 27005 26933 26565 10784 10782 10772

Ponds (ha) 0 0 0 0 0 0

Plantation (ha) 3632 3522 3061 1404 1400 1383

Water (ha) 1626 1626 1626 130 130 130

Total urban area (ha) 4233 4945 8329 1195 1278 1700

Total irrigated paddy area (ha) 3645 3594 3353 1573 1569 1551


53089 52378 48994 18598 18515 18093

Total area (ha) 90217 90217 90217 33946 33946 33946

Total population 143941 157352 197670 40691 43632 52432






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Table J.4, Overview of spatial results in 2015, 2018, 2022 and 2042 for four compartments of Lake Toba:

South 2 and South 3.

Variables S2 S3

2018 2022 2042 2018 2022 2042





Kecamatan city population 3668 3761 4035 14818 15056 15804

Desa population 160417 171956 203774 117555 127426 158712

Employment 83023 88394 132849 40631 43345 66550

Households 39572 43081 56103 33388 36595 49387

Housing (ha) 3606 3942 5152 2624 2802 3503

Other buildings (ha) 445 514 1271 394 426 779


Technical Irrigated Paddy (ha) 6731 6687 6475 7326 7276 7026

Semi-technical Irrigated Paddy (ha)

4488 4458 4317 4884 4851 4684

Other agriculture (ha) 40560 40376 39507 6645 6618 6483

Grass/Other (ha) 4403 4382 4289 1987 1981 1951

Shrub (ha) 25401 25327 24939 5785 5773 5712

Forest (ha) 18151 18132 18031 6465 6459 6427

Ponds (ha) 0 0 0 0 0 0

Plantation (ha) 6699 6668 6520 20892 20817 20440

Water (ha) 1589 1589 1589 231 231 231

Total urban area (ha) 4051 4456 6422 3018 3228 4282

Total irrigated paddy area (ha) 11219 11146 10792 12210 12127 11710


81817 81411 79445 44031 43821 42767

Total area (ha) 112591 112591 112591 57297 57297 57297

Total population 164086 175717 207809 132372 142482 174515







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J.4 Calculation of nutrient concentration trajectories

Total nitrogen (TN) and total phosphorous (TP) concentrations are calculated in a simple

budget model approach. In this model the total nutrient concentration in a water body is

determined by the loading, the lake’s area and mean thermocline depth, the flushing rate,

and the fraction of nutrients retained in the water column:

C = L / (Q + k * A * d)

In which:

C = the calculated concentration (µg/l)

L = the nutrient load as calculated in the section above (µg/d)

Q = outflow (m3/d)

k = retention rate (1/d)

A = surface area (m2)

d = thermocline depth (m)

The above budget model is a modification of the models in previous Lake Toba carrying

capacity studies (Oakley 2015; LIPI, EPANS, CFM, 2014). Ultimately this budget model

approach stems from the widely used empirical model of Dillon & Rigler (1974), developed

to predict the response of aquatic ecosystems to increases in P loadings.

The outflow varies between 90 and 140 m3/s (Vernuimmen, 2015; section 2.2.1; Annex

B.5). In the model, this value is set at 110 m3/s; a combination of long term average and

extrapolation of trends. On the total volume of Lake Toba, the exact value of outflow has

minimal impact on the resulting concentrations. The effect is the same in the

compartments.

Figure J.6, The effect of changing lake outflows on concentrations of total phosphorous (P) in Lake Toba, for

the whole lake compartment.

Note that the budget model approach is an over-simplification of reality, which does not

take into account the complexity of physical and biogeochemical processes, nor their

variability in time and space. The model does therefore not provide any system


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understanding, nor provides any predictions about future changes in physical or

biogeochemical processes. The compartment approach addressesat least some of the

spatial variability present in Lake Toba. Also, the sensitivity for the thermocline depth is

explored. For more precise computations and predictions, it is recommended to use a 3D

ecosystem model.

J.5 Comparison to LIPI data

Results from the Sumatra Spatial Model were compared to findings from LIPI, such as

their 2010 study that describes the trophic state of 19 different measuring points along the

coast line of Lake Toba. The state is determined by measuring a series of parameters:

Total Organic Matter (TOM), Dissolved Organic Matter (DOM), Phosphate Organic Matter

(POM), Total Nitrogen (TN), Dissolved Oxygen, Temperature (Suhu), pH, and Conductivity

(LIPI 2013; Figure J.7). The values in the table of Figure J.7 correspond well with the PTAN

figures.

Figure J.7, LIPI data set 2010. Various parameters measured at 19 different locations in April of 2010. See

table on the right for values of different measurements (Figure provided by LIPI).

Another study conducted by LIPI in 2013 that TN concentrations measured in 2013 vary between 0.075 and 0.374 mg/l (Figure J.8), which corresponds well with the amounts mentioned in chapter 6. Station 7 and 8 (with concentration of 0.238 and 0.302 mg/l) are those closest to the measuring points of PTAN.



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J-15

Figure J.8, LIPI data set 2013. Various parameters measured at 19 different locations in August and October

of 2013 (Figure provided by LIPI).

14

13

15

16

11 12

10

17

18

19

9 1

2

8 6

Asa

han 3 4

7 5



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K-1

K Available data and their quality

K.1 Data collected from stakeholders

Many stakeholders provided data relevant for this study, such as catchment-wide GIS data on

land use, population statistics, agricultural statistics or lake monitoring data such as nutrient

concentrations, water transparency and chlorophyll concentrations. Table K.1 summarizes the

data, collected from the stakeholders, which have been included in the lake and catchment

assessment.

In environmental monitoring data fall in three functional categories, or levels, with significant

differences in monitoring effort:

1. Monitor environmental status (signal function)

2. Explain environmental phenomenon (exploratory)

3. Scientific, statistically sound analysis or modelling The usability of data differs per topic, question, or focus. Therefore, the general usability indicator was assigned per topic: trophic status, water balance, hydrodynamic modelling (3D), estimating nutrient inputs form the catchment and lake activities (nutrient loading), lake carrying capacity, and estimating catchment erosion load (erosion).

Table K.2 shows - data usability assessment for the available reference group data, inthe three

functional categories identified in the inception report. As much as possible and pending approval by data owners, the various data and literature collected in the course of this assignment are made available to the Reference Group. In that way, all participants can benefit from the aggregated and collective data.



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K-3

Table K.1, Overview of types of data collected by stakeholders of Lake Toba. The cells marked green depict data received by the consultant (in any form).



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K-5

Table K.2, Data assessment based on three functional categories (1) signal function; (2) exploratory data; (3)

statistically conclusive. The assessment is given for overall and for 6 applications. Not all data may apply to

all applications.


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K-6

K.2 Completeness of the data sets

To assess the completeness of the water quality data sets collected by the institutions

described in section 3.3, the data have been compared to the monitoring guideline set up by

Chapman (1996). His table indicates the water quality parameters that are relevant for various

issues (Table K.3). The marks indicate the likelihood that the concentration of the parameter

will be affected. If so, it is more important to include the variable in a monitoring program.

Variables stipulated in local guidelines or standards for a specific water use should be included

when monitoring that specific use. Of main interest to the underlying assessment are the

‘background monitoring’ and ‘aquatic life and fisheries’ (highlighted columns).

Table K.3, Selection of variables for assessment of water quality in relation to non-industrial water use (adapted

from: Chapman, 1996). Rating x to xxx: low to high likelihood that the concentration will be affected and low

to high importance to include the variable in a monitoring program. Background monitoring

Aquatic life and fisheries

Drinking water

sources

Recreation and health

Agriculture

Irrigation Livestock watering

General parameters

Temperature xxx xxx

x

Colour xx

xx xx

Odour

xx xx

Suspended solids xxx xxx xxx xxx

Turbidity/transparency x xx xx xx

Conductivity xx x x

x

Total dissolved solids

x x

xxx x

pH xxx xx x x xx

Dissolved oxygen xxx xx x

x

Hardness

x xx

Chlorophyll a x xx xx xx

Nutrients

Ammonia x xxx x

Nitrate/Nitrite xx x xxx

xx

Phosphorous or phosphate xx

Organic matter

TOC xx

x x

COD xx xx

BOD xxx xxx xx

Major ions

Sodium x

x

xxx

Potassium x

Calcium x

x x

Magnesium xx

x

Chloride xx

x

xxx

Sulphate x

x

x



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K-7

Background monitoring

Aquatic life and fisheries

Drinking water

sources

Recreation and health

Agriculture

Irrigation Livestock watering


Fluoride

xx

x x

Boron

xx x

Cyanide

x x

Trace elements

Heavy metals

xx xxx

x x

Arsenic & selenium

xx xx

x x


Oil and hydrocarbons

x xx xx x x

Organic solvents

x xxx

x

Phenols

x xx

x

Pesticides

xx xx

x

Surfactants

x x x

x


Feacal coliforms

xxx xxx xxx

Total coliforms

xxx xxx x

For this study the Chapman table has been adapted and filled with water quality parameters

have been measured by DLH-SU, LIPI, and PTAN (Table K.4). For each variable, crosses

indicate whether a certain parameter was considered relevant (according to the Chapman

(1996) guideline) for background monitoring and/or aquatic life, but was not present in one of

these three data sets. All parameters for which data were available were highlighted.

Table K.4, Data availability of DLH-SU, LIPI and PTAN, with indication of relevance (according to the Chapman

guidelines). When x is used, the variable is not present in the data set.

BLH-SU LIPI PTAN

Variable locations

time frequency locations

time frequency

locations

time frequency

General parameters

Temperature 18-28 2006-2016

1-2 per year

12 2009 once 4 2006-2017

monthly

Colour xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/-

Odour 18-28 2006-2016

1-2 per year

Suspended solids 18-28 2006-2016

1-2 per year

xxx/xxx

xxx/xxx

xxx/xxx xxx/xxx

xxx/xxx xxx/xxx

Turbidity/transparency

18-28 2006-2016

1-2 per year

12 2009 once 4 2006-2017

monthly

Conductivity xx/x xx/x xx/x xx/x xx/x xx/x xx/x xx/x xx/x

Total dissolved solids 18-28 2006-2016

1-2 per year

-/x -/x -/x -/x -/x -/x

pH 18-28 2006-2016

1-2 per year

12 2009 once 4 2006-2017

monthly

Dissolved oxygen 18-28 2006-2016

1-2 per year

xxx/xx xxx/xx xxx/xx 4 2006-2017

monthly


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K-8

TOC: Total organic carbon

BOD: Biochemical oxygen demand

COD: Chemical oxygen demand

Hardness -/x -/x -/x -/x -/x -/x -/x -/x -/x

Chlorophyll a 18-28 2006-2016

1-2 per year

12 2009 once 4 2006-2017

monthly

Nutrients

Ammonia 18-28 2006-2016

1-2 per year

x/xxx x/xxx x/xxx 4 2006-2017

monthly

Nitrate/Nitrite 18-28 2006-2016

1-2 per year

12 2009 Once 4 2006-2017

monthly

Phosphorous or phosphate

18-28 2006-2016

1-2 per year

12 2009 once 4 2006-2017

monthly

Organic matter

TOC 18-28 2006-2016

1-2 per year

xx/- xx/- xx/- 4 2006-2017

monthly

COD 18-28 2006-2016

1-2 per year

xx/xx xx/xx xx/xx xx/xx xx/xx xx/xx

BOD 18-28 2006-2016

1-2 per year

xxx/xxx

xxx/xxx

xxx/xxx xxx/xxx

xxx/xxx

xxx/xxx

Major ions

Sodium x/- x/- x/- x/- x/- x/- x/- x/- x/-

Potassium x/- x/- x/- x/- x/- x/- x/- x/- x/-

Calcium x/- x/- x/- x/- x/- x/- x/- x/- x/-

Magnesium 18-28 2006-2016

1-2 per year

xx/- xx/- xx/- xx/- xx/- xx/-

Chloride 18-28 2006-2016

1-2 per year

xx/- xx/- xx/- xx/- xx/- xx/-

Sulphate 18-28 2006-2016

1-2 per year

x/- x/- x/- x/- x/- x/-


Fluoride

Boron

Cyanide -/x -/x -/x -/x -/x -/x -/x -/x -/x

Trace elements

Heavy metals 18-28 2006-2016

1-2 per year

-/xx -/xx -/xx -/xx -/xx -/xx

Arsenic & selenium -/xx -/xx -/xx -/xx -/xx -/xx -/xx -/xx -/xx


Oil and hydrocarbons 18-28 2006-2016

1-2 per year

-/x -/x -/x -/x -/x -/x

Organic solvents x/- x/- x/- x/- x/- x/- x/- x/- x/-

Phenols x/- x/- x/- x/- x/- x/- x/- x/- x/-

Pesticides xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/- xx/-

Surfactants x/- x/- x/- x/- x/- x/- x/- x/- x/-


Feacal coliforms

Total coliforms

Pathogens



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K-9

Table K.4 shows that currently the DLH-SU data set is the most comprehensive data set of the

three. Only few of the relevant parameters are missing (hardness, conductivity, sodium,

potassium, calcium cyanide, arsenic and selenium, organic solvents, phenols, pesticides,

surfactants), of which for Lake Toba probably only the organic contaminants (solvents, phenols,

pesticides) are of relevance. The PTAN and LIPI data sets are less ‘complete’ with respect to

their set of parameters, as compared to the Chapman guideline.

K.3 Spatial and temporal distribution of data

The spatial vertical distribution of the 3 datasets confirms the different purposes of the data

collection. Both DLH-SU and LIPI aim to cover the whole lake. DLH-SU focusses on parameters

near the shore, probably connected to local pollutant sources and LIPI on characterizing the

lake itself by selecting only mid-lake monitoring points. PTAN is focusing on their aquaculture

farms and has one reference point. For whole lake monitoring on level 2 or 3, the combination

of DLH-SU and LIPI monitoring locations seems a good and non-overlapping match.

As for horizontal distribution (profiles), the DLH-SU data set does not contain depth information,

but a safe assumption would be that samples are taken directly below the water surface, in the

upper epilimnion. Both the LIPI and PTAN data do contain depth profiles; for 100 and 200m

depth, respectively. For the lake assessment, the profile data up to at least 200 m depth are

necessary, especially on temperature and oxygen to fully cover the transition of epilimnion to

the hypolimnion.

The temporal distributions of the data sets vary. PTAN data are most consistent, with monthly

data. DLH-SU monitors 1 to 2 times a year, consistent with their level 1 aim. LIPI data covers

2009 only, though more unpublished data might be present. For level 2 and 3, monthly data

can be regarded as the minimum requirement.99


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L Additional recommendations livestock

L.1 Steps in managing livestock manure

The various costs listed in Table 8.8 for the promotion of biogas production are detailed

below in Table L.1.

Table L.1, Activities proposed for the upscaling of conversion of livestock manure into biogas around Lake

Toba.

step activity category

1 Coordination with kabupaten and other institutions Institutional

2 Assign university to prepare criteria of proposal, design,

evaluation criteria

Information

3 Conduct data collection of livestock owners and numbers of

animals

Information

4 Short course Institutional

5 Site visit and comparative study (high scenario only) Information

6 Development of brochures, information campaign Information

7 Recruit field workers Infrastructure

8 Implementation of pilot biogas plants for smallholders Infrastructure

9 Implementation of pilot biogas plants for big companies Infrastructure

10 Output-based approach for replication Infrastructure

11 Assign university for monitoring and evaluation of the pilot Information

12 Additional training Institutional

L.2 Promotion of biogas production

The promotion of biogas production can be accelerated by various measures. For

instance:

1. Incentives for increased biogas use of solid manure should be created, such as

o Funding for technology development of dry fermentation.

o Funding for technology development of increasing degradation of solid

biomasses via efficient re-treatments.

o Support for co-digestion of slurry and solid manure.

2. Manure-based biogas plants utilising wastes and by-products as co-substrates should

be given priority in subsidy systems and permission processes.

o Energy crops utilisation should be regionally justified so as to avoid harmful

consequences for the environment and competition with food and feed

production.



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3. Manure-based biogas plants with clear plans to optimise the entire manure

management chain before and after the plant should be given priority in subsidy

systems and permission processes.

o Proper solutions for substrate collection, plant design and operation, and

storage, spread and potential post-processing of the digestate require

development to avoid pollution-swapping between different steps.

4. Energy efficient use of the biogas produced should be a key criterion for the

environmental permit and the financial support system.

o The best local utilisation of the biogas energy needs to be determined already

in the planning phase of the biogas plant.

L.3 Sustainable manure management

Additional considerations can be formulated to support Sustainable Manure

Management40: 1. There is an urgent need to raise the awareness of proper manure management. In

particular the possible effects on spreading of livestock diseases to humans, animals.

2. Legislation should be put in place to prevent discharge of animal manure (including

liquids) to surface waters (irrigation and drainage channels, rivers, ponds and lakes).

3. Considering the lack of a sustainable future for livestock production in urban

environments, the development, or continuation, of livestock rearing in the vicinity of

urban areas should be discouraged.

4. Development and adaptation of technologies for effective manure management should

be undertaken, as appropriate for local livestock production systems, and should be

accompanied by the introduction of legislation for effective uptake of technologies.

5. Surveys of current practices of manure application within crop production systems

should be undertaken, and the effects of manure applications on crop yield and soil

quality should be studied. The use of manure as a source of organic matter in poor

and degraded soils should be given attention by farmers, extension personnel and

those persons responsible for land management.

6. Animal manure management lies at the interface between animal production, soil

science and plant production. In order that animal manure is used effectively as a

resource and, therefore, not a source of pollution, there is a need to enhance

cooperation between researchers, legislators and NGOs from these fields. A systems

approach will encourage the integration of animal, soil and plant components, thereby

facilitating effective manure management.

7. An integrated system for the use of organic manure and inorganic fertilizers offers the

greatest potential for the sustainable management of manures while minimizing

40 Adopted from “Guidelines for Sustainable Manure Management in Asian Livestock Production Systems”; IAEA-

TECDOC-1582; May 2008


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L-12

environmental pollution and developing confidence amongst farmers in the use of

animal manures.

8. The integrated use of animal manures, in combination with inorganic fertilizers, is likely

to result in increases in crop and forage production, resulting in economic benefit for

farmers, as well as environmental benefits.

9. The development of pilot/demonstration farms (incorporating appropriate levels of

technology) is felt to be an effective way of promoting positive messages on manure

management at the local level.

10. Development of decision support software can assist in manure management system

design and in improved understanding of nutrient fluxes following manure application.

This technology can be very effective in the promotion and uptake of sound manure

management practices.

11. Training courses on nutrient budgets and improved manure management practices

should be designed and an initial test-run conducted for possible wider dissemination.

12. Based on current understanding and experience, a number of information

sheets/pamphlets, on ‘best practices’ of manure management should be prepared and

distributed, for use by extension workers and farmers.

13. The initiation of programs to reward farmers for carrying out sustainable manure

management activities is felt to be a particularly useful strategy. This is believed to be

an effective way of motivating other farmers to adopt ‘best’ manure management

practices.



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M Background information wastewater interventions

This annex provides more details on domestic wastewater (sewage), with special attention

to the tourism industry, as additional background to and elaboration of section 8.4.

M.1 Background and approach

The initial input for the inventory of the existing and planned infrastructure related to

sewage is based on the sanitation strategies (e.g. BPS, SSK, MPS) for each of the

kabupaten in the catchment. These documents have been prepared in most kabupaten in

the framework of the PPSP41 supported by the Urban Sanitation Development Program

(USDP42) and its predecessors. Experience and lessons learned in these programs, as

well as work done by the BWRMP (e.g. as presented in the report Laporan Kualitas, Air

WS Toba Asahan Provinsi Sumatera Utara; TA – BWRMP WISMP 2; October 2015), steer

the identification of interventions and assess issues and developments for successful

implementation (e.g. the comprehensive, multi-faceted program at local level).

In the light of the RPJMN 2015-2019 and as an input for the PPSP-2, USDP prepared an

assessment of the country wide (domestic) wastewater funding and facilities required in

the period of 2015-201943 (and beyond). The database that was developed for this

assessment was adapted (scaled down) to the Lake Toba catchment area and updated

with population figures and developments according to the Sumatra Spatial Model.

In the USDP various interventions are proposed and these serve as a basis for the

proposed investments. The selection of type of WWT facilities is based on the approach

explained in the Buku Referensi (TTPS, 2009). This approach aims to reduce the risk to

health and environment at the lowest costs. Thus, in urban areas with high population

densities and high exposure levels, on-site systems (septic tanks) are no longer preferred

and off-site systems with improved performance (removal efficiencies) are selected, which

is a general applied approach (UNEP, 2004). In Table M.1 the selection criteria are listed

to determine the most suitable type of sanitation facility.

41 The National Accelerated Sanitation Development for Human Settlements Program or Program Nasional

Percepatan Pembangunan Sanitasi Permukiman (PPSP) is a national program launched by the government

of the Republic of Indonesia for the development of integrated sanitation, from national to local level, by

involving all stakeholders from government and non-government parties (http://www.ppsp.info/). 42 The Urban Sanitation Development Program (USDP) is a technical support project, within Accelerated

Sanitation Development for Human Settlements Program or Program Percepatan Pembangunan Sanitasi

Permukiman (PPSP). USDP took a role to facilitate and further strengthen GoI institutions at the national,

provincial and, indirectly, at the local level to be involved in implementing the program. Funded by Embassy of

the Kingdom of the Netherlands, USDP supports over 400 cities and regencies throughout Indonesia with

technical, institutional and health related services (http://www.usdp.or.id/). 43 Sanitation Needs Assessment 2015-2019; USDP, January 2015, USDP-R-PIU.T-10083-2


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Table M.1, Selection criteria for wastewater facilities per type of area features.

BPS

criteria

Residential

pop.density

(pp/ha)

General

description

Type of WWT

system

Examples of

system

Rural < 100 Rural areas On-site systems Septic tank

Rural >100 Peri urban Community based IPAL communal/

MCK

Urban < 25 Very Low density

urban areas

On-site systems Septic tank

Urban 25-100 Low density

urban areas

Existing houses on-

site; New

developments off-

site

Existing: septic

tanks; New

developments:

IPAL Kawasan

Urban 100-250 High density

urban areas

off-site systems IPAL Kawasan

Urban >250 off-site systems IPAL Terpusat

Specific considerations:

• Country wide BPS 2010 data show that in urban areas nearly a quarter (23%) of poor

households practice open defecation (in the non-poor areas this was 7%). Around lake

Toba the reported percentage open defecation lies around 30% (except for Karo:

12%). Many of the areas where urban poor live could qualify for an off-site system.

However, this is not considered the most feasible options. This is because

o off-site systems require a certain amount of water available to transport the

solids, which is not likely to be the case, as often proper water provision is

lacking as well;

o areas are often temporary or concern non-legal houses, and;

o both willingness and availability to pay for operation for this group of

households is very limited44.

For these households, temporary facilities (either MCK or IPAL communal) are a more

appropriate solution. During a general renovation/rehabilitation of such areas, a more

structural solution (e.g. off-site system) can be considered. When putting the 2018-

2042 period in perspective these households are assumed to be connected to off-site

systems.

• In this assessment, an off-site (IPAL Terpusat) system is only proposed if:

o The indicated urban and population density values apply;

o The number of households connected in one Kab/Kota to this system exceed

10,000 (equivalent to 50,000 people);

o the GDP per indicated Kab/Kota reaches a value of 3,000 US$ (based on 2010

BPS value and expectedly 3,500 US$ by 2015), following Bappenas’ findings

on sustainability of large off-site systems in other developing countries;

44 It is, however, a political decision to apply a ‘polluter pays’ principle.



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o In case the two latter conditions are not met, one or more IPAL Kawasans are

proposed instead of an IPAL Terpusat. Possibly these systems could be further

connected in the long-term future.

• Existing urban conditions:

o Many of the urban on-site systems do not comply with the definition of a septic

tank and are more like pit latrines or leach pits (Cubluks) (Kearton et al., 2013).

The result is that there is still a lot of leakage of polluted water to the

groundwater;

o In addition, often the septic tank overflow is connected (together with the

greywater) to the drainage system that eventually discharges to the surface

water (WSP, 2013);

o In both of these situations human health as well as the quality of surface and

groundwater in urban areas are jeopardized.

• The approach to convert from existing systems to future “improved” systems in urban

cases is as follows: In order to improve the urban health and environmental conditions,

the described existing conditions should eventually be minimized. This entails (1) the

removal of poorly performing septic tanks that pollute the ground- and surface water

and connect to a sewerage collection system, and (2) interception and treatment of

the effluent septic tank water and greywater before it reaches the surface water.

o The former activity is to be best performed when renovations in the households

are taking place and requires active campaigning and socialization of the

individual households in line with the development of the sewer

system/interceptor system.

o The second activity, which aims to intercept and treat the water before being

discharged to surface water is best started from a location just before

discharge point and then gradually moving upstream to locations closer to the

house.

o Thus, eventually, part of these households will be connected to off-site

systems (even though they are already counted as “improved”). In this

assessment, it is estimated that in a 20 year time period half (50%) of the

existing urban population currently recorded as having a septic tank/cubluk will

be connected to an off-site system. For the first 5 years (2018-2022) this value

is only 5%.

Septic tanks and community based systems require regular desludging. However,

households in rural areas with low densities (<25 pp/ha) do not require this and IPLT’s will

only serve the households served by a septic tank and community based systems in urban

areas and higher density rural areas. The minimum size of an IPLT is 10,000 people,

whereas the maximum sizes is 200,000 people. If there are more people that require an

IPLT a second one will be constructed.

Applied cost figures:

An analysis was carried out to determine the investment (CAPEX) and operational costs

(OPEX) for wastewater collection and treatment facilities (Figure M.1). A distinction is

made between investment figures for existing and new developing areas. In new to be

developed areas costs for sewer works are expectedly lower and, if planned properly,


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M-16

these works can be done in conjunction with the general new area development. In this

assessment, the costs for sewer systems for new areas are expected to be reduced by

50%45 compared to the investments in an existing area. The cost for the wastewater

treatment Plant (WWTP) itself is expected to be the same either way.

Cost figures for off-site systems were updated from the Waste Water Management

Investment Roadmap46 which was drafted for the ADB funded City Wide Sanitation

Investment Program.

Figure M.1, Applied unit rates for indicated wastewater facilities.

Legislation

In theory, there are many regulations and incentives to manage wastewater (see also

section 3.4. For example, the standard on wastewater management is outlined in

Ministerial Regulation of KLHK No. 68/2016. Ministerial Regulation of PUPR No. 4/2017

was issued regarding the implementation of domestic waste water management system.

Until now, the Districts of the area surrounding Lake Toba have a tendency to follow

directives from the Ministry of Home Affairs. However, in the instruction letter from the

Minister of Environment and Forestry that determines the water quality classification of

Toba, the Ministry of Home Affairs was not copied. So far, the Districts have not shown

45 Based on data of the Dutch situation it is found that more than half of the costs of the sewer system in

existing areas are related to the opening and closing of existing roads/pavements. In new

developments, the opening up of the streets is not relevant and the construction of pavement is

considered part of the general development and a 50% factor for sewer system development is applied. 46 City Wide Sanitation Investment Program, Waste Water Management Investment Roadmap; Asian

Development Bank, May 2016; BE1344/R001/MvK/Indo



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M-

any commitment to wastewater collection and treatment. For more information on relevant

legislation, see section 3.4.

M.2 Investment scenarios

For the intermediate scenario C, the intervention type selection is done according to national

guidelines, with 85% Minimum Service Standards and 15% Basic sanitation in 2022 and 100%

Minimum Service Standards in 2042 (Figure M.2). In the high scenario D the level 100%

Minimum Service Standards is reached in 2022, combined with off-site systems for core tourist

areas. Table M.2 shows for each of the scenarios the number of new wastewater systems to

be constructed until 2022 and 2042.

Figure M.2, Indicative development of new wastewater systems in the period 2018-2022 for the intermediate

scenario C.


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Table M.2, New wastewater systems targeted for 2022 and 2042 in the intermediate and high investment

scenarios.

on-site CBS IPLT IPAL Kawasan

Intermediate scenario C

2022 22,845 644 16 15

2042 40,718 1,446 26 31

High scenario D

2022 24,593 276 17 92

2042 33,666 379 25 206

The costs presented in section 8.4 are total costs based on unit cost per person; however, these cost need to be covered from different sources. These budgets need to come from both private and public sources. And the public sources can be subdivided into national and local level as well is by department (i.e public works and ministry of health. Finally, the cost includes hardware (i.e. physical measures) and software (i.e. advocacy/socialization and studies/design). The following table shows how the budget is divided (% allocated) by government level and department.

Table M.3, Budget division by government level and department – Wastewater On-site CBS IPAL Kawasan

Activity div % source* div% source* div% source*

Studies

-Master plan

0.25 N_PU_S

-LARAPAMDAL,FS

0.25 Lo_PU_S

Design

-guidelines

1 N_PU_S 1 N_PU_S

-detailing

4 U_S 3 N_PU_S

Campaign Advocacy, Socialization

-General 5 N_AE_S 2 N_PU_S 0.5 Lo_AE_S

-kabkot 5 Lo_AE_S 4 Lo_AE_S 2 Lo_AE_S

Land acquisition

11 U_La 3 Lo_La

Construction activities

-House connection 9 U_H 24 U_H 13 Lo_PU_H

-Sewer; IPLT for onsite

1 N_PU_H 22 N_PU_H 43 N_PU_H

-Treatment 80 U_H 32 N_PU_H 34 N_PU_H

All 100

100

100

Notes: Level: N=national, Lo=local (Provincial and/or kab/kot), U=user Department: PU = Public works (or construction), AE= Advocacy and Empowerment (=Ministry of health) Type: S= Software; H= Hardware, La=Land

The IPLT and communal system can be financed by the central government providing that

the municipalities have met the “readiness criteria”, e.g. land availability and institutional

set-up. As above mentioned, land availability is a challenging issue (cultural significance).

One solution to reduce the challenge is by developing a regional system where one

infrastructure will serve several municipalities. A regional system is more attractive for the

central government (MPWH) to finance. The institutional issue can be solved by assigning



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19

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PDAM Tirtanadi in Parapat to be responsible for the sludge management and for that

purpose it needs to be supported by a provincial regulation. Table M.4 shows how the budget is divided by government level and department for the base scenario. A large part of the cost (~30%) is allocated to the users/community.

Table M.4, Budget by government level and department in the intermediate scenario C for wastewater.

period Origin of funds WWT IDR

Total 25 years (2018-

2042)

Investments

National 1,779 Billion

Local gov't (Kabkot+Prov) 259 Billion

users/community 1,041 Billion

total 3,079 Billion

OPEX 48,768 Million/y


2022)

Investments

National 774 Billion


users/community 493 Billion

total 1,389 Billion



2022)

Investments national division

Infra (Public works) 688 Billion

Design and studies (PU) 20 Billion

CA /instit. (Health +

Bangda)

66 Billion

total 774 Billion


2022)

Investments local division (prov/Kabkot)




Bangda)

49 Billion

total 122 Billion

Table M.5 shows how the budget is divided by government level and department for the high scenario D. The total budget is remarkably higher; however, the cost for the users and community is about 40% that of the intermediate scenario. This is the result of the shift from community-based systems to IPAL Kawasan.

Table M.5, Budget by government level and department in the high scenario D for wastewater.



2042)

Investments



– Final Report


M-20

Local gov't (Kabkot+Prov) 1,380 Billion


total 8,056 Billion



2022)

Investments




total 4,362 Billion


period Division national WWT


2022)

Investments (national division)

Infra (Public works) 3,046 Billion



Bangda)

110 Billion

total 3,318 Billion


2022)

Investments local division (prov./Kabkot)




Bangda)

99 Billion

total 733 Billion

Supply chains would be different for each of the scenarios. Figure 8.9 shows a potential supply chain for Parapat, and Figure M.3, Figure M.4, and Figure M.5 suggest supply chains for the low B, intermediate C, and high D investment scenarios, respectively.

Figure M.3, Supply chain for low investment scenario B (after Tilley et al. 2008).

User


Transportation /

Conveyance

Centralized


Recycled

sludge

Effluent to

river / lake

Ground

water

Public

toiletSeptic Tank (ST)

Sludge

TruckSTP (IPLT)

Infiltration

area

Items

Infrastructure

Finance CSR or Local Government LG / Province Central Gov.

Regulation Set the performance of the public toilet

Local governmentInstitutionEnv agency to

monitorLocal private sector or LG agency



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Figure M.4, Supply chain for intermediate investment scenario C (after Tilley et al. 2008).

Figure M.5, Supply chain for high investment scenario D (after Tilley et al. 2008).

M.3 Parapat

For the concrete suggestion for improvement of the existing sewerage system in Parapat, a separate cost assessment was made. Concrete suggestions for the existing sewerage system in Parapat are: a. Repair the existing sewer line, either fully (best scenario) or at least in the

commercial area (intermediate scenario);

b. Additional sewer line to receive more customer;

c. Improve the process in the existing WWTP. d. Connect effluent of septic tank to the sewer line at a later stage (part of the IPAL

Kawasan system).

e. Design additional IPAL Kawasan

f. Construct additional IPAL Kawasan

User


Transportation /

Conveyance

Centralized


Recycled

sludge

Effluent to

river / lake

Ground

water

WC / toilet Septic Tank (ST)Sludge

TruckSTP (IPLT)

Infiltration

area

Items

Infrastructure

Sewer line

1st

stage

2nd

stage

WWTPEffluent to

river / lake

Finance Customer LG / Province Central Gov.

Regulation Standard ST – Connect to sewer

PDAM Tirtanadi to manageInstitutionEnv agency to

monitor

User


Transportation /

Conveyance

Centralized


Recycled

sludge

Effluent to

river / lake

WC / Toilet Sewer line WWTP

Items

Infrastructure

Finance CustomerProvince /

Central GovCentral Gov.

Regulation Obligation to connect & fee

PDAM Tirtanadi or Local GovernmentInstitutionEnv agency to

monitor

Customer for house connection

LG for branch sewer


– Final Report


M-22

g. Construct reliable public toilet including the below-structure (septic tank) at tourism

hotspots;

Table M.6, Three investment scenarios for wastewater management at the existing wastewater treatment

plant in Parapat.

Total costs (US$) for Parapat

Low Intermediate High

Infrastructure

a. Repair existing sewer lines in Parapat

150,000 750,000

b. Additional sewer line to receive more customers

2,700,000

c. Improve the process in the wastewater treatment plant

,.000,000

d. Connect effluent of septic tank to the sewer line (at a later stage)

80,.000

e. Construct reliable public toilet including the below-structure (septic tank)

150,000

Institutional

f. Local regulation for customers to connect to sewer

25,000

g. Enforce the hotels and restaurants to connect to sewer

20,000

h. Prepare local regulation to construct septic tank in accordance to technical standard

20,000

i. Assign PDAM Tirtanadi for O&M 5,000

j. Assign responsible institution for the operation of the public toilet

5,000

Information

k. Open contact with private companies

5,000

l. Set the performance of the public toilet

5,000

Total of each scenario (US$) 215,000 950,000 7,470,000

M.4 Institutional recommendations on wastewater management47

47 Largely based on City Wide Sanitation Investment Program (2016).



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M.4.1 General considerations

Sanitation development in the Lake Toba catchment cannot operate in a vacuum.

Implementation of the Wastewater Management Investment Roadmap (City Wide

Sanitation Investment Program, 2016), especially with regards to the further planning and

implementation of physical infrastructure will inevitably need to be aligned with the national

planning and budgeting procedures. National targets will need to be translated in the

planning and budgeting at provincial and local levels and reflected in the strategic planning

of the concerned provincial and local government departments, for which mechanisms are

in place.

Beside planning and budgeting the required infrastructure, which essentially need to be

undertaken at local levels, it is acknowledged that a successful achievement of higher

levels of access to improved waste water management needs to go hand in hand with

(sometimes drastic) policy reforms. In addition, in view of the ambitious targets set,

Government is facing a serious capacity gap, especially in having sufficient skilled and

experiences officials at all levels of government and in all technical and non-technical

agencies required to deal with sanitation development in a professional way and in

planning as well as implementation. This also holds true for the national consultancy

sector. Capacity building and training is a key subject of on-going programs in the

sanitation sector that indeed receives the necessary attention. However, it will take time

before this will bear fruit, for instance in terms of skills development for local administrators

and the availability of newly graduated sanitation engineers able to join government

agencies or consultancy firms.

Local governments need to understand the implications of the targets set by the central

government for their own situation and that ‘business as usual’ in planning and budgeting

for improving sanitation is no longer adequate. It is important that local government officials

are properly advocated and are made aware that they must step up (i) their own financing

for sanitation development, and (ii) get actively engaged in sourcing external funding. The

financing modalities and especially the readiness criteria of such external funding sources

should be fully understood and taken into account in planning and budgeting.

For the higher investments in infrastructure, for which external funding from central and/or

provincial government would be available it is important for local governments to first

comply with the readiness criteria; hence plan and allocate funds for that with priority.

These would typically include (i) Master and Feasibility planning; (ii) Meeting social and

environmental safeguards if co required (impact assessments); (iii) Land acquisition; (iv)

Detailed engineering designs; and (v) Ensuring community awareness and participation.

All this should be undertaken first and budgets allocated accordingly.

M.4.2 Policy actions

Successful sanitation development has to go hand in hand with reform of the sector.

Institutional and procedural related aspects to sanitation development at national and local

level, including legislation and regulatory provisions need to be addressed in concrete

actions. Table M.7 and Table M.8 present an overview of recommended policy actions at

national and local level, respectively. Actions marked with ‘Immediate’ should be

addressed in 6 to 12 months, actions marked with ‘Short-term” in the coming 1 to 2 years.


– Final Report


M-24

Table M.7, Recommended policy actions at national level to support implementation of the Wastewater

Management Investment Roadmap (City Wide Sanitation Investment Program, 2016).

Priority Area Immediate Actions

6 – 12 months

Short-term Actions

1 – 2 years

Strengthen National Regulation, Oversight and Monitoring

Secure a Joint Ministerial Regulation on the effectiveness of programs and activities for development of sanitation and water supply

Outline the establishment of a National Sanitation Development Council charged with coordinating legislation and regulation and overseeing and monitoring performance of local governments

Secure regulation on asset transfer and local sanitation management (post construction)

Outline the establishment of a National Sanitation Management Board charged with coordination of and managing sanitation investments

Secure Bappenas regulation on the management and organization of Nawasis to ensure that it becomes the data source for sector monitoring and fund allocation;

Develop and/or strengthen Sewerage and Septage Management Laws outlining obligations, mandates and implementation arrangements

Balance Investments Develop program(s) for improving on-site sanitation at scale

Include tertiary sewerage and household connection in basic designs, including costing

Allocate resources (financial and human) for faecal sludge management

Develop and implement investment program for medium-scale sewerage systems (IPAL Kawasan, for up to 5,000 hh connections)

Improve Funding Clarify funding source related readiness criteria and build capacity at local government levels to receive funding

Reform and remove legal barriers to subsidizing improved on-site sanitation for low income and disadvantaged households and facilitate practical and affordable mechanisms for financial support

Prioritize and provide funding for measures directly increasing access levels (no regret measures)

Remove regulatory barriers for putting in place cost reflective pricing schemes and sustained tariff collection mechanism

Align national faecal sludge management programs with improving on-site sanitation

Improve Standards Review and develop improved national standards for access to improved waste water management covering the entire service chain (section M.2) and in line with international criteria



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6 – 12 months

Short-term Actions

1 – 2 years

Intensify inclusion of social aspects

(Re-)develop and promote behaviour change communication packages and strengthen delivery modalities

Restructure Capacity Building and Training

Decentralize responsibilities for operational implementation of CBT

Finance CBT through ministries involved with sanitation development

Engage education and training institutes in developing appropriate course curricula on sanitation planning, implementation and management

Improve Monitoring and Evaluation

Optimize the use of the National Water and Sanitation Information System (Nawasis)

Table M.8, Recommended policy actions at local level to support implementation of the Wastewater



6 – 12 months

Short-term Actions

1 – 2 years

Strengthen local regulation

Develop standard template and promulgate Govenor Regulations or Decrees on the position of the provincial Roadmap

Review and develop improved Standard Operation Procedures for wastewater and sludge treatment facilities

Develop standard template and promulgate Mayoral/Regental Regulations or Decrees on the position of the district SSK/MPS as input for local planning

Develop and adapt local regulations for putting in place cost reflective pricing schemes and sustained tariff collection mechanism

Develop standard template and promulgate a Mayoral/Regental Regulation or Decree on the establishment of a wastewater management organisation

Balance Investments Allocate local resources for improving on-site sanitation at scale

Allocate local resources (financial and human) for faecal sludge management

Allocate local resources and implement investment program for medium-scale sewerage systems (IPAL Kawasan, for up to 5,000 hh connections)

Improve Funding Align local funding for faecal sludge management programs with improving on-site sanitation

Establish subsidy schemes for improved on-site sanitation for low


– Final Report


M-26


6 – 12 months

Short-term Actions

1 – 2 years

income and disadvantaged households

Improve Standards Adhere to national standards but consider local conditions and local regulations

Develop and implement

M.4.3 Technical assistance

Apart from recommended technical assistance (TA) support in the fields of national and local regulations, finding a right balanced investment regime and to improve national codes, standards and permitting modalities for each of the investment packages, or combinations thereof, will require external support in scoping, planning and preparatory studies, and design, tendering and construction supervision of civil works. Technical assistance could be financed directly by the central, provincial, or local governments or through Bilateral Grants, dedicated technical assistance Grants or Loans, or technical assistance provided as part of bigger investment loans of international financing institutions (IFI). Table M.9presents an overview of recommended technical assistance, together with a suggested funding source.

Table M.9, Modalities and funding options for technical assistance in implementation of the Wastewater


Description of technical assistance Proposed Funding Souce

Timeframe

Strengthen national and local regulations

1.1 Assist national government with the development and establishment of a dedicated National Sanitation Development Council and National Waste Water Management Board

Bilateral Grant Short to medium term

1.2 Review and recommend strengthening or new national legislation

Bilateral Grant Short term

1.3 Develop standard/templates for local regulations and modalities for enforcement

Bilateral Grant Immediate

1.4 Review and recommend improvements on current permitting systems and their enforcement

Bilateral Grant Short term

Balance investments

2.1 Assist LGs developing and establishing faecal sludge management, align this with improved on-site sanitation including the formation of a dedicated waste water management organisation with a practical institutional development trajectory developed and implemented

Bilateral Grant or IFI TA Loan

Immediate



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Description of technical assistance Proposed Funding Souce

Timeframe

2.2 Assist national and local governments establishing a pilot or a broader program for planning and implementing medium-scale sewerage systems (IPAL Kawasan)


Immediate

Improve standards

3.1 Review and recommend improvements to national codes and standards

Bilateral Short term

Improve Implementation

4.1 Review and improve advocacy programs and their dissemination modalities

Bilateral Grant Immediate

4.2 Assist LGs with Master Plan, Feasibility Studies, EIAs, Resettlement, DED, Tendering and Construction Supervision

TA Loan or tied to IFI Loan Programs or Projects

Immediate to short term

Capacity Building and Training

5.1 Design HRM of waste water management organisations


Immediate

5.2 Design a dedicated capacity building program for waste water management organisations


Immediate

Monitoring and Evaluation

6.1 Improve Nawasis and strengthen utilization at provincial and local levels

Bilateral Immediate

To ensure adequate allocations for sanitation development, funding possibilities could be

explored to reallocate funds from other sectors; and increase borrowing from international

financing agencies; and pursue sanitation infrastructure development as a preventive

public health measure. The latter would make it eligible for funding under the 10% budget

earmarked for public health from provincial and local budgets. The sector itself has scope

to further develop cost recovery through charging service fees. At a national level, the

revenue could be increased through introducing new or revised ‘sanitation related’ taxes

or levies.

M.4.4 Other recommendations

Summarizing, planning and coordination between major stakeholders in sanitation

development could be improved by establishing an independent, responsible body at

catchment level to effectively regulate sanitation development, that is also charged with

monitoring performance against minimum service standards. The ‘Urban Waste Water

Framework’ (Figure M.6) can be adapted to the situation in the Lake Toba area. This

framework integrates the various drivers of domestic waste water management into a

comprehensive urban waste water management scheme. Together, the independent body

and the framework can create and maintain an enabling environment that embraces

regulatory conditions in a strong institutional setting.


– Final Report


M-28

Figure M.6, Urban Waste Water Management Framework.

In addition to the issues mentioned above, a “National Law on Sanitation” should be

drafted, approved and promoted. This would facilitate urgent decision making on a number

of legal/regulatory aspects related to sanitation development mentioned in Table M.7 and

Table M.8. At the beginning of the process, institutional roles and responsibilities need to

be clarified, including the establishment of and capacity building for a ‘wastewater

management unit’ in charge of catchment-wide sanitation services; development of all

components of the sanitation service chain (figures in section M.2), followed by the

handover of assets built and managed by different agencies to the agency ultimately in

charge of wastewater management.

Wastewater regulations must be established, promoted and enforced, requiring among

others:

• Existing and new households to connect to sewerage systems, where they exist;

• Households to build improved on-site sanitation in areas without sewerage;

• Institutionalization of facilities for faecal sludge management and mechanisms for

regular emptying of septic tanks;

• Payment of tariffs or contributions to infrastructure construction (improved on-site

sanitation or connection to sewer) or operation (sewerage and/or emptying services).

As part of the promotion and improvement of the balance of investments (Table M.7 and

Table M.8) it is crucial to include smaller infrastructure and faecal sludge management,

acknowledging that more than 90% of wastewater management is on-site and in need of

substantial investments to ensure compliance with environmental standards. In planning,

design and construction, tertiary sewers and household connections must be given equal

emphasis as wastewater mains and treatment facilities. Where tertiary networks and

household connections are not part of the main project funding, then as a minimum

requirement they must be included in the overall system design to optimize it and to better

enable local government to plan and budget for their construction.

A common issue of septic tanks is that these are not always built in accordance with the

technical standard, i.e. not watertight. This contributes to ground water pollution and may

contaminate wells and create health risks. To support the achievement of the sanitation

coverage target, for the last few years the Ministry of Public Works and Housing (MPWH)

c.q. Directorate General of Human Settlements has launched an “output based program”.

Under this program the municipal that provides standard septic tanks to households can

get reimbursed from the central government.



Final Report

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In the preparation of practical phased sanitation investment plans, the full-service chain

for both on-site and sewerage systems must be addressed (see figures in section M.2).

Adopting a step-wise approach to investment will facilitate efficient spending, matched to

demand. In this respect it is wise to use up and optimize idle capacity of existing off-site

systems and sludge treatment facilities (IPLT) first. Existing sewerage systems and sludge

treatment facilities can be rehabilitated and expanded to more households.

Additional recommendations:

Improve codes and standards and related technical aspects

• Improve minimum service standards for access to improved sanitation, sewerage

and faecal sludge management.

• Ensure national standards cover entire sanitation service chains and can be easily

adopted at a local level.

• Improve national codes and standards for on-site systems, sewer connections,

treatment and reuse.

• Allow for multi-year contracting of facilitators and services providing consultants.

• Improve construction quality, operations and maintenance.

Pay appropriate attention to social aspects

• Develop behaviour change communication packages and institutionalize advocacy

mechanism.

• Inform the public of wastewater standards, targets and responsible agencies so they

understand their rights and increase demand on local governments.


– Final Report


M-30

Focused capacity building

• Accept limited effectiveness and impact of formal training, and shift to coaching

instead.

• Identify subject areas for which sufficient capacity development can only come

through increased numbers of graduates from the regular education system.

• Decentralize responsibility for operational implementation of capacity building and

training.

• Finance capacity building and training from the ministries involved with sanitation

development.

Improve and further institutionalize monitoring and evaluation

• Optimize the use of the National Water and Sanitation Information System (Nawasis)

as decision support system.

• Arrange for institutional embedding of Nawasis.

• Collect and collate information and undertake performance assessments of off-site

and on-site waste water management systems.

• Include monitoring of system performance with the aim to check meeting minimum

service standards and upload performance contracts with utilities into Nawasis.



Final Report

N-1

N-1

N Other sectors

N.1 Solid waste

N.1.1 Approach and background

Currently, the management of solid waste is under Environmental District Services according

to the Government Regulation no.18/2016 (see section 3.4). This is a structural change from

previously operation under City Planning and Sanitation District Services, which has not been

fully implemented yet and is not functioning properly. The district governments have not

established any formal arrangement for waste management and currently there are no formal

final garbage disposal sites (TPA) or areas. Unlike for wastewater, there are no directives for

reaching a certain solid waste coverage target. On a national level (Bappenas) priority is given

to improvement of the urban solid waste situation for the period 2015-2019. No additional

infrastructure is proposed for rural areas. Without such directives given from the Ministry of

Home Affairs to the Districts, there seems to be a reluctance and lack of motivation from the

Districts to implement improvement actions on solid waste treatment.

Solid waste management is one of the basic local government services that need to involve the

communities. It is included in the Sanitation Strategy for Districts and Cities (or SSK) prepared

by the assembled city sanitation working groups (POKJA Sanitasi). The community,

represented by KSM, is responsible for collecting the garbage from the source to the

intermediate collecting point (TPS). From that point to the final disposal site (TPA) should be

under the responsible local government agency. In practice, the local communities use the

‘open dumping method’.

At the moment, solid waste might not contribute much to the water quality degradation of Lake

Toba and therefore the impacts have not been modelled. However, this may be different in the

future with more people. Moreover, lack of good solid waste management is bad for tourism.

As with (domestic) wastewater, the PPSP-2 USDP prepared an assessment of the country wide

solid waste funding and facilities required in the period of 2015-2019 (and beyond) for the

RPJMN 2015-2019. The database that was developed for this assessment was adapted

(scaled down) to the Lake Toba catchment area and updated with population figures and

developments according to the Sumatra Spatial Model. Tourism development has been

accounted for.

For MSW two activities have been distinguished. The first one deals with collection, transfer and transport systems of solid waste and the second one deals with the final treatment or disposal of solid waste. Table N.1 shows the proposed developments as per current policies based on (1) urban and rural features, (2) time of developments and (3) population densities for these activities.


– Final Report


N-2

Table N.1, Planned interventions for MSW.

Type Rural Urban

Implementation Only after 2022 2018-2022 2023-2042

Density (pp/ha) <25 >25 <100 >100 <100 >100

Collection no yes yes yes

Disposal no yes Kab/Kota without

TPA

Build new TPA in

Kab/Kota with

already existing TPA

3R

(50% of people

targeted)

Home

compost

At TPS

(decentral)

level

At TPS

(decentral)

level

Central level

in Kab/Kota

without TPA

At TPS/

community

level

Central level

in Kab/Kota

without TPA

Note:

Because of a low success rate with 3R community based systems operated by the community;

a different operating system (e.g. operated by the dinas kerbersihan) should be considered to

sustain these facilities

Specific considerations for rural areas:

In line with the view of Bappenas, the priority lies on improvement of the urban situation for the

medium term. No additional infrastructure is proposed for rural areas per national policy.

However, in the longer term the higher dense rural population will be served by MSW

infrastructure as well. In this assessment, a rural area is classified as high density when the

residential population is more than 25 pp/ha (based on the expected 2027 situation). Thus, for

all rural areas with lower densities no collection or landfills will be developed in the short and

long term. However, in this assessment promotion of 3R and home composting for these areas

is included after 2022.

Specific considerations for landfills:

In order to identify the investment costs, it is expected that collection is done by motor sampah

and transfer takes place in a TPS-III with containers from where it is transported by Armroll

truck. Waste is finally disposed of in a sanitary landfill. Landfill development follows a stepwise

approach. This means that in the first phase the land for the complete period until 2042 is

purchased. Further, a first cell with a lifetime of 5 years and the facilities are constructed (office,

weighing bridge, vehicles, leachate treatment plant). After the first five years, an extension is

developed, again with a lifetime of 5 years. However, offices and leachate treatment plants only

require some minor upgrading. Thus, the second phase of the landfill development has lower

specific costs than the first development.

Specific considerations for 3R:

In PPSP (2010-2014) 3R (Reduce, Reuse, Recycle) is promoted. 3R includes the recovery and

processing of organic waste into compost and recovery of plastics, paper and other reusable

products like glass, timber, and metals. Data provided by PU shows that by the end of 2013

310 3R community based stations were constructed48. Figure N.1 shows that for rural areas

with residential population densities below 25 pp/ha after 2020 composting at a household level

is promoted. For higher densely rural populated areas, communal composters at the level of a

TPS station are proposed. In all cases, there is direct potential for reuse. Also for lower dense

(<100 pp/ha) populated urban areas communal composters at the TPS level and direct reuse

are proposed. Based on the current experience with communal 3R stations, which show a

48 Data are obtained from RINCIAN per SATKER 2013 provided by the Ministry of Public Works



Final Report

N-3

N-3

rather low (about 30% mentioned only) success rate only, the management of these systems

should be with the a dinas, rather than a community. For the high dense urban areas, a

centralized 3R facility is proposed. Recently larger scale 3R systems are being introduced and

tested, like in Banda Aceh, Bima and Cijantung. These systems consist of a recoverable waste

separation step (plastics and papers), a digestion step and a composting step. The refuse is

finally disposed of in a landfill. In this assessment, a differentiation is made between centralized

3R stations that (1) apply composting only, and (2) that apply digestion followed by

composting49. Plastic and glass recovery is applied in both types of centralized 3R facilities. In

order to come to a 20% waste reduction that is finally disposed in a TPA, the waste of about

30% of the population needs to be processed via 3R.

Figure N.1, Specific investment prices (CAPEX in IDR) per type of area (urban/rural) and management (3R or rural).

The unit running cost figures (OPEX) for the described cases are presented in Figure N.2.

49 Several pilots are currently taking place in Indonesia with this type of treatment system. Advantage of this

approach is that besides the production of compost, also biogas is produced, which, if centrally and in

sufficiently large quantities produced, can act as a source of energy. This however requires higher

investment costs. In this assessment it is assumed that half of the central 3R systems apply digestion and

composting, whereas the other half applies only composting besides the plastic and glass separation.


– Final Report


N-4

Figure N.2, Specific running costs (in IDR) per type of area (urban/rural) and management (3R or rural) – figures in

brackets are revenue.

N.1.1.1 Existing Facilities

Table N.2 shows the existing facilities for solid waste disposal in the 7 kabupaten surrounding Lake

Toba. None of the landfills is designed or constructed as a proper sanitary landfill; all are operated

as open dumping.

Table N.2, Existing facilities for solid waste disposal.

Kabupaten # TPA* Remarks

Tapanuli Utara 0 units

Toba Samosir 2 units TPA at kec. Laguboti: area of 2 ha, operating from 2001

TPA at kec. Ajibata: area of 0.2 ha, operating from 2005

Both are operated as open dumping.

Simalungun

Dairi 1 unit TPA at kec. Berampu: area of 4 ha, operating as open dumping.

Humbang Hasundutan 1 unit TPA Saitnihuta: operating as open dumping.

Samosir 2 units TPA at kec. Simanindo

TPA at kec. Ronggor Nihuta.

Both are operated as open dumping.



Final Report

N-5

N-5

Kabupaten # TPA* Remarks

Karo 3 units 1. Nang Belawan 2. Keriahen 3. Tongging

No special design (just a field with open dumping practice).

* Tempat Pemrosesan Akhir – Solid waste landfill

N.1.2 Investment scenarios

N.1.2.1 Infrastructure

For solid waste two scenarios are considered; an intermediate scenario that follows the national

policy, a low scenario that envisages a more realistic, slower, rate of implementation, and an

accelerated scenario that reaches 100% coverage by 2022. Table 8.12 shows for each of the

scenarios the access to domestic waste collection and disposal or 3R facilities. For the

intermediate scenario, the criteria for the type selection are applied across the Lake Toba area

as envisaged in Figure N.3. For the accelerated scenario, map is presented in Figure N.4.

Figure N.3, Development of solid waste systems in the period 2018-2022 for the intermediate scenario C.


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Figure N.4, Development of solid waste systems in the period 2018-2022 for the high scenario D.

N.1.2.2 Institutional Improvements could be made with commitment from regional leaders, aiming at improving solid waste management to support tourism in Lake Toba. The province could lead the development of a regional waste management program, together with the seven kabupaten draining into the lake. Concrete suggestions for Lake Toba:

a. Contract private sector(s) for transporting the solid waste;

b. Manage the waste sorters working at the TPA

c. Facilitate work for the waste sorters, making it easier to collect recyclable material

at the TPA.

d. Facilitate the community (through PKK) to start “at home composting”

e. Facilitate the community (through PKK) to establish “bank sampah”

One way to attract the attention of the regional leaders is by correlating it with tourism instead of with health.

N.1.2.3 Costed scenarios Table N.3 shows details of the investment required to reach 80% collection/treatment urban – none for rural by 2022 and 100% collection/treatment urban + rural by 2042. Total coverage does not reach 100% because some rural areas do not qualify for collection/disposal even in the long term. Also given is the yearly OPEX required for operation and maintenance of the systems. Note that currently an estimated 0% of population's waste is disposed of in a sanitary landfill; costs are based on prices of TPA sites constructed by 2013



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Table N.3, Solid waste intervention targets and investment cost in the intermediate scenario C (in IDR).

Sub-sector MSW

System IDR Collection

activities

Final disposal and

3R facilities

Total MSW

New Investments (2018-

2042)

Billion 157 869 1,025

targets access to safe

waste disposal

0-4 years (2018-2022) 12% 12% 12%

5-10 years (2023-2027) 92% 94% 92%

11-15 years (2028-2032) 92% 95% 92%

16-25 years (2033-2042) 93% 95% 93%

Investment planning

Inv.: 0-4 y (2018-2022) Billion 8 120 128

Inv.: 5-10 y (2023-2027) Billion 116 460 576

Inv.: 11-15 y (2028-2032) Billion 11 125 136

Inv.: 16-25 y (2033-2042) Billion 22 164 186

OPEX: at 4 y Million/y 14,254 4,139 18,393




Table N.4 shows the investment required to reach 100% collection/treatment urban + rural by 2022 and onward. In this case 100% coverage is reached because the type selection for low density rural areas is overruled. Also given is the yearly OPEX required for operation and maintenance of the systems. Currently an estimated 0% of population's waste is disposed of in a sanitary landfill; costs are based on prices of TPA sites constructed by 2013

Table N.4, Solid waste intervention targets and investment for the high investment scenario D (in IDR).

Sub-sector MSW


activities

Final

disposal

and 3R

facilities

Total MSW

New Investments (2018-

2042)

Billion 157 885 1,042

targets access to safe

waste disposal

0-4 years (2018-2022) 100% 100% 100%

5-10 years (2023-2027) 100% 100% 100%

11-15 years (2028-2032) 100% 100% 100%


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Sub-sector MSW


activities

Final

disposal

and 3R

facilities

Total MSW

16-25 years (2033-2042) 100% 100% 100%

Investment planning

Inv.: 0-4 y (2018-2022) Billion 113 295 408

Inv.: 5-10 y (2023-2027) Billion 10 156 167

Inv.: 11-15 y (2028-2032) Billion 11 171 182

Inv.: 16-25 y (2033-2042) Billion 22 262 284





The cost presented in the above tables are total costs based on unit cost per person; however, these cost need to be covered from different sources. These budgets need to come from both private and public sources. And the public sources can be subdivided into national/local level as well is by department (i.e public works and ministry of health. Finally, the cost includes hardware (i.e. physical measures) and software (i.e. advocacy/socialization and studies/design). Table N.5 shows how the budget is divided (% allocated) by government level and department. This is elaborated in Table N.6 for the intermediate scenario C and in Table N.7 for the high scenario D. For the summary Table 8.13, the total of mobilized funds in a low investment scenario B serve as reserved funds.

Table N.5, Budget division by government level and department – Solid waste

Activity Collection-transfer-

transport

Treatment

div% source* div% source*

Studies

-Master plan 3 N_PU_S 1.5 N_PU_S

-LARAPAMDAL,FS 1 Lo_PU_S 1 Lo_PU_S

Design

-guidelines 2 N_PU_S 2 N_PU_S

-detailing 2 Lo_PU_S 3 Lo_PU_S

Campaign Advocacy,

Socialization

-General 1 N_AE_S 0.5 N_AE_S

-kabkot 2 Lo_AE_S 1 Lo_AE_S

Land acquisition 10 Lo_La 20 Lo_La

Construction/procurement

activities

53 Lo_PU_H 55 N_PU_H

(civil)

-Collection/Treatment 26 U_H

(collection)

16 Lo_PU_H(

Elec&mec

h)



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All 100

100

Notes: Level: N=national, Lo=local (Provincial and/or kab/kot), U=user Department: PU = Public works (or construction), AE= Advocacy and Empowerment (=Ministry of health) Type: S= Software; H= Hardware, La=Land

Table N.6, Budget by government level and department for the intermediate scenario C on solid waste.


Total 25 years (2018-2042) Investments




total 1,025 Billion



National 74 Billion



total 128 Billion


Total 4 years (2018-2022) Investments (national division)



CA /instit. (Health + Bangda) 2 Billion

total 74 Billion

Total 4 years (2018-2022) Investments local division (prov./Kabot)




total 52 Billion

Table N.7, Budget by government level and department for the high investment scenario D on solid waste.






total 1,042 Billion







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total 408 Billion


Total 4 years (2018-2022) Investments national division




total 188 Billion

period Division Local (prov./Kabkot) WWT

Total 4 years (2018-2022) Investments local division (prov./Kabot)




total 192 Billion

N.1.3 Conclusions and recommendations

• Cost for solid waste management is 12%-30% of wastewater cost (depending on

wastewater type selection);

• Difference in total cost (until 2042) between the national targets (base scenario) higher

targets (accelerated scenario) on Lake Toba catchment is negligible;

• Applying higher targets results in a shift of cost to an earlier period (until 2022);

• Main burden of solid waste management cost lies with local and national government.

Even more so than domestic wastewater, solid waste has a limited direct effect on the water

quality of Lake Toba. However, as with wastewater, aspects such as health, wellbeing and

environmental amenities make it necessary to address proper disposal of solid waste—in

particular in the light of tourism development.

N.2 Erosion reduction

N.2.1 Background

The unsustainable conversion of forests surrounding Lake Toba into other types of land use,

and associated illegal logging and land and forest fires, have led to a decrease in Lake Toba’s

water quality, among others because Toba stream water and surface runoff have stimulated

the growth of algae. While community wastes and waste waters also contribute, the unique

combination of major and minor nutrients, trace elements, and natural organic compounds

released by the erosion of Toba watersheds together stimulate the algal growth. Erosion

control, forest rehabilitation, and better land-use management are therefore critical to maintain

the health of Lake Toba.

Many regulations have been issued by the national and subnational governments over the

years to solve the problems associated with erosion. These regulations are often related to the



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national targets and initiatives on restoration, such as the National Movement for Rehabilitation

(GN-RHL/Gerhan) launched in 2003 and the One Billion Trees program launched in 2011. The

current national target is to rehabilitate up to 5.5 million hectares of ‘critical land’ nationally by

2019. In many of those initiatives, Lake Toba appears on the list of priority areas. The visits of

the President or the Minister of Environment and Forestry to Lake Toba are often accompanied

by ceremonial tree planting and speeches about the importance of rehabilitating the forests

surrounding the lake.

The planning and execution of erosion control and reforestation have mainly been the domain

of the national and sub-national government agencies and implemented in a top-down

approach. As a sign of mistrust, a few weeks after the President and his entourage did a

ceremonial tree planting near the shore of Lake Toba, some villagers uprooted the trees

because those do not belong to the species that the locals wanted to plant in the area. This is

emblematic of the problem with many restoration projects in Indonesia, whereby there is little

sense of ownership by the locals as they are not involved in the decision-making process.

The Save Indonesian Lake Movement (‘Germadan’) in 2009 (see section 3.4) for Lake Toba

attempts to review all the regulations related to Lake Toba and analysed the gaps in the overall

management of Lake Toba, including its surrounding. The Ministry of Environment and

Forestry, together with the Provincial Forest Service, is now implementing a reforestation

program. In this program, members of the community are invited to manage 10 hectares of

forest, for which they get permission to plant 1 hectare with whatever trees they want. The

stakeholders expressed fears that the GERMADAN is at risk of becoming yet another review

or planning document with little impact or no implementation because it does not legally bind

the stakeholders mentioned in the document to conduct certain actions.

Another problem is the potentially contradictory regulations and actions that would work against

the erosion control and reforestation efforts. For example, the edict issued by President Jokowi

to establish a special authority to revive and manage Lake Toba’s tourism industry (PP No.

49/2016) contains a section about re-zoning some areas surrounding the lake currently

classified as “protected forest” into other uses in a fast-tracked process. This fast-track

approach could possibly bypass some due process needed before the legal status of forest

estates can be altered. Further, a weak law enforcement process has let illegal logging to take

place in the forests near Lake Toba, including in protected forest areas. If unchecked, large-

scale illegal logging could greatly undermine the efforts to restore forests in the Toba

landscape.

N.2.2 Investment scenarios Several interventions would reduce erosion in Lake Toba’s catchment area. Below various suggestions are made, some of which would have optimal effects, while others can be considered the bare minimum. In Table 8.14 these are summarised with approximate costs and an indication of total budget for each of the two scenarios.

N.2.2.1 Infrastructure

Healthy forests act as a filter to keep pollution out of water. Strong roots anchor soil against

erosion and material on the forest floor helps absorb nutrients and sediment. But when forests

are disturbed and degraded, sediment flows into streams and pollutes water.


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Natural infrastructure approaches can mitigate and prevent further damage in watersheds.

Establishing conservation zones, engaging in agroforestry and other sustainable forestry

practices and regulating road development can help. Figure N.5 compares the costs of grey

infrastructure with green infrastructure such as watershed conservation, forestation, and

wetlands in the United States. Green infrastructure is less costly than investing in water filtration

plants or improving wastewater treatment plants and systems.

Figure N.5, Investment costs for natural infrastructure and gray infrastructure.

While cost-benefit analyses of restoration and establishing “natural infrastructure” for the

catchment of Lake Toba have not been done yet, several studies on restoration in Indonesia

suggest that the costs to restore degraded landscapes are relatively small (Table N.8). The

cost to restore through the community forestry scheme, which would allow local communities

to develop agroforestry and agro-tourism, appears to be lower than other schemes. Indeed, a

study conducted by World Resources Institute Indonesia and World Agroforestry Center

(ICRAF) in the Musi Watershed of South Sumatra suggests that all restoration interventions,

including agroforestry, rehabilitation, natural regeneration, yield relatively high benefit to cost

ratios and internal rates of return, with agroforestry emerging as the best option economically

(unpublished document).



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Table N.8, Standard costs per hectare for forest rehabilitation and restoration strategies (FAO, 2016).

Strategy Standard costs (US$/ha) Sources

Industrial timber plantation (HTI) and

community-based timber plantation (HTR)

666-12,111 MOF (2009)

Community forestry scheme (HKm) 60 Arlan (2013)

Deposit for mining reclamation 1,500-2,000 Sunandar (2013)

Restoration ecosystem 1,400 Arlan (2013)

In addition to conducting natural restoration, building several simple structures, e.g.

containment dam and gully plugs in the upper watershed, controller dam and terraces in the

central part of the watershed, and infiltration wells in the lower watershed can go a long way in

the effort to reduce erosion. Further, such structures could help prevent natural disasters

(floods and landslides) and protect vital buildings located downstream. Additional analyses will

help determine where and how many of such structures need to be built in the catchment of

Toba so that the costs could be estimated. According to Ministry of Forestry’s guideline on the

rehabilitation program, the unit costs for building structures that could reduce erosion in

Sumatra range from US$ 278 to 17,863 (Table N.9).

Table N.9, Standard costs per unit of physical/grey infrastructures built to reduce erosion (Ministry of Forestry,

2013)

Structure to be built Cost/unit in 2012 (US$)

Containment dam 2,506

Controller dam 17,683

Infiltration well 383

Gully plug 278

Concrete suggestions for Lake Toba:

a. Natural infrastructure: construct and restore nature-based solutions such as forests and

wetlands.

b. Construct grey infrastructure to reduce erosion, such as containment dams, checkers,

gully plugs, and terraces on or around steep slopes.

c. Restore degraded lands in the catchment, taking into account ecological, socio-political,

economic, and cultural aspects, to improve both forest cover and people’s livelihoods.

N.2.2.2 Institutional

The social forestry scheme and customary forest scheme, which are essentially community-

managed forests schemes, could be explored as an alternative of managing the forests around

Lake Toba. In Indonesia’s medium term development plan, the government targeted 2.5 million

hectares of forests allocated for communities each year. The Ministry of Environment and

Forestry has established the Indicative Map of Social Forestry Area (Figure N.6). The task is

now to develop this indicative map into a definitive social forestry area. This scheme could

potentially reduce erosion since it could increase the forest cover in degraded areas or critical

lands, while at the same time the community could receive benefits of forests products from

directly managing the land. The cost per hectare to implement the community forestry scheme

is only about US$ 60, lower than other restoration strategies (Figure N.5 and Table N.9). In

addition to social forestry, the government could consider synchronizing and expanding the

various planting activities that are conducted by private companies around Lake Toba, often as

part of corporate social responsibility schemes.


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In the implementation of these interventions, it is important to pay attention to the business

models for different types of restoration strategies. For example, the agroforestry and agro-

industry that could be developed in Toba will need various on-farm and off-farm support, e.g. a

factory for processing the commodities, or a formal body from the government acting as a

middleman to buy and sell the products, which will help in regulating the price. A feasibility

study conducted by the research center of the Ministry50 does show the benefits of developing

agroforestry in North Sumatra. For example, the net present value/NPV (as of 2013) of coffee

agroforestry was US$ 1,000/ha, while the NPVs for rubber and benzoin agroforestry were US$

787/ha and US$ 434/ha respectively. Differentiating products across districts could also help.

“One Kecamatan One Product” has been introduced in Lebak, Banten in 2001 and could serve

as a lesson learned area. The concept can be translated into “One Kabupaten One Product” in

Lake Toba area. To select the right commodities in certain appropriate locations, academic and

research institutions, such as the Indonesian Tropical Fruits Research Institute (Balai Pelatihan

Tanaman Buah Tropika) under the Ministry of Agriculture can be engaged.

Figure N.6, Indicative area of social forestry around Lake Toba.

To support this, expanding and strengthening agricultural extension services will help the

government in developing agro-industry and agro-tourism near Lake Toba. Technology

transfer, knowledge dissemination, outreach activities to farmers, farmer-to-farmer exchange,

and farmer field schools need to be conducted or organized by government agencies, with

assistance from experienced NGOs. Based on the government’s guideline for extension

services, the monthly operational cost for one extension service staff is ~ US$ 31 (Ministry of

Forestry, 2013). Ideally, there would be one extension service staff per village. One of the

primary goals of such services is to ensure the adoption of sustainable planting processes,

especially for onion and potato, which will help conserve the environment while improving the

agricultural yield and, hopefully, farmers’ income.

50 http://www.worldagroforestry.org/sea/Publications/files/paper/PP0342-14.pdf



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d. Introduce and develop agro-industry and agro-tourism with strong community

involvement, encompassing all parts of the value-chain, as part of efforts to improve

people’s livelihoods while reducing the extent of critical/degraded lands.

e. Encourage local communities to adopt best planting practices so as to reduce erosion

and avoid detrimental impacts of fertilizers and business-as-usual planting practices.

f. Strengthen both the regulations and institutional aspects of restoration, especially for

restoration through social forestry/customary forest schemes and partnerships with

private sector (via corporate social responsibility schemes)

N.2.2.3 Information

Monitoring from the National Land Agency (or BPN) and from the Ministry of Agrarian and

Spatial Planning should be made tighter in relation to land conversion (land use change from

protection forest to other use), as referred to Presidential Regulation No. 81/2014. At the

provincial lev

el, the monitoring effort should be synchronized with the provincial spatial plan (RTRW).

Monitoring could also be done by the Ministry of Environment and Forestry that oversees the

forest moratorium policy. The Ministry has launched the “Indicative Map for Forest Moratorium”

to halt granting new licenses for forest concession on primary forests and on peatland. Tight

monitoring on forest concessions inside the Lake Toba Water Catchment Area is therefore

essential to prevent non adherence to the policy on the ground. Further, areas in the realm of

the Lake Toba Tourism Area Management Authority (BOPDT) require further study, such as a

strategic environmental assessment, before any rezoning can be conducted. Close monitoring

on their rezoning activity is also needed.

Global Forest Watch Water (GFW Water) is a free global database and interactive mapping

tool designed to help identify deforestation risks to watersheds and opportunities for natural

infrastructure solutions. The tool can help downstream beneficiaries, financing and

development institutions, civil society and research groups apply natural infrastructure as one

of their strategies to enhance water security and improve watershed management. In South

Sumatra, for example, the provincial government is working on incorporating Global Forest

Watch into the provincial government’s situation room room at a cost of around US$ 50,000

(personal communication). A similar initiative could be set up by the provincial government of

North Sumatra.


g. Adapt Global Forest Watch Water for use in North Sumatra.

h. Monitor closely land-use conversion around Lake Toba utilizing the various tools

available to reduce illegal deforestation.


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N.2.2.4 Costed scenarios

Table N.10, Summary of measures for erosion control and total costs of two different scenarios.

Measure Costs

Best

scenario

Minimal

scenario

Infrastructure

i. Natural infrastructure (reforestation) 1,150

US$/ha

x

j. Erosion control structures x

k. Restoration of degraded lands x

Institutional

l. Develop agro-industry and agro-

tourism

x

m. Promote best planting practices 859 US$/ha

n. Strengthen regulations and

institutional aspects

x

Information

o. Adapt GFW Water x

p. Monitor land-use conversion x

N.2.2.5 Impacts

Upstream forests, wetlands, and other “natural infrastructure” play a critical role in the supply

of clean water downstream. They stabilize soil and reduce erosion, regulate water flow to

mitigate floods and droughts, and purify water. In the 2010 Java Water Resources Strategic

Study (JWRSS) by Deltares and Royal Haskoning, the on-site benefits of reforestation and

improved agriculture have been calculated as 4.43 and 1.58 million rupiahs annually per

hectare, respectively. In the case of Lake Toba, it is expected that restoration through various

means will make the area more attractive for tourists, and hence would yield relatively high

benefits.

developing a roadmap for improving water quality of lake toba …p3tb.pu.go.id/uploads_file/world...

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