geoinformatics for inter b asin water transfer assessment: … · 2008-04-01 · basin to the ganga...

Geoinformatics for Inter B asin Water Transfer Assessment: A study in parts of Ganga –

Brahmaputra Basin, Eastern India

Niladri Gupta

March, 2008

Course Title: Geo-Information Science and Earth Observation

for Environmental Modelling and Management

Level: Master of Science (Msc)

Course Duration: September 2006 - March 2008

Consortium partners: University of Southampton (UK)

Lund University (Sweden) University of Warsaw (Poland) International Institute for Geo-Information Science and Earth Observation (ITC) (The Netherlands)

GEM thesis number: 2006-20

Geoinformatics for inter basin water transfer assessment: A study in parts of Ganga

– Brahmaputra basin, Eastern India

by

Niladri Gupta Thesis submitted to the International Institute for Geo-information Science and Earth Observation in partial fulfilment of the requirements for the degree of Master of Science in Geo-information Science and Earth Observation for Environmental Modelling and Management Thesis Assessment Board Chairman: Dr. Ir. C.A.J.M. (Kees) de Bie External Examiner: Dr. Ir. C.M.M. (Chris) Mannaerts Internal Examiner: Prof. Petter Pilesjö Supervisor: Mr. Ulrik Martensson Supervisor: Dr. B.H.P. (Ben) Maathuis

International Institute for Geo-Information Science and Earth Observation Enschede, The Netherlands

Disclaimer This document describes work undertaken as part of a programme of study at the International Institute for Geo-information Science and Earth Observation. All views and opinions expressed therein remain the sole responsibility of the author, and do not necessarily represent those of the institute.

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Abstract

Fresh water availability and demand is unequally distributed over time and space. Availability of fresh water has more or less remained constant despite natural temporal fluctuation (Gupta and Zaag, 2007); the demand for clean water is ever increasing. With increasing demand of water, surpassing the supply, an integrated water resource management approach is required to balance environmental, social and economic considerations in the decision making process. Inter basin water transfer (IBWT) is one such approach which is being carried out in various countries of the world with varying environmental and social implication. The Interlinking of Rivers (ILR) project is one such alternative being planned in India. The present research is undertaken with the background of the ILR project focussing on two links between the Brahmaputra and Ganga basin. An assessment of the IBWT program in some of these tributaries of the Brahmaputra and the Ganga River in the eastern part of India covering the district of Jalpaiguri, West Bengal, India is carried out using Geoinformatics as a tool, IRS LISS III and LANDSAT TM data are used to generate thematic maps (landuse, geomorphology, drainage and geology) with an aim of carrying out multi-criteria analysis (MCA), considering physical and socio-economic suitability, to locate potential reservoirs to store water as well as delineating optimal canal route for transferring the water from the Brahmaputra basin to the Ganga basin for further transportation to the water deficit regions of India. Shuttle Radar Topography Mission (SRTM) dataset of near global coverage averaged to 90 m resolution is used as an input for elevation information for the MCA as well as for estimating reservoir capacity and reservoir extent using a neighbourhood function of ILWIS as an iterative propagation process. The reservoir locations and an assumed discharge of water are then used to set about some dimensioning of the proposed link canal and the optimal routing to transfer the water. As assessment of the utilization of the available water for irrigation and human consumption has been done considering assumed losses due to evaporation, conveyance and reduction in reservoir capacity taking into account the characteristics of the rivers in the study area which carries a lot of sediment load. The research is a stepping stone for a future pre-feasibility study in this region using similar techniques but with more detailed dataset for the proposed links in the ILR plan and to find the feasibility of the proposed project.

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Acknowledgements

I would like to express my thanks to the European Union and the Erasmus Mundus consortium (University of Southampton, UK, Lund University, Sweden, Warsaw University, Poland and ITC, The Netherlands) for awarding me the scholarship to undertake this course in four European countries. It has been a lifetime experience for me. I would like to thank my primary supervisors Prof. Petter Pilesjo and Mr. Ulrik Martensson of Lund University, Sweden for their continuous support, guidance and useful suggestions during writing and finalisation of this thesis. I gained a lot of experience and honoured to have the opportunity to work with them. I would also like to thank them for their support and hospitality during my stay in Sweden. I am most grateful to my second supervisor Dr. Ben Maathuis for his continuous guidance to bring the research into shape. I gained a lot of scientific experience from him and I am grateful to him for his contribution to this research. I was overwhelmed by his patience and the encouragement that he gave me from the beginning of the work until the production of the thesis. My special thanks to Mr. Sanjoy Nag, Sr. Scientist and Dr. Parthasarathi Chakrabarti, Chief Scientist, Department of Science & Technology, Govt. of West Bengal for their invaluable support and suggestions during my field work and primary database generation. I would like to extend my gratitude to Prof. Peter Atkinson, Prof. Andrew Skidmore, Prof. Katarzyna Dobrowska, Dr. Andre Kooiman, Dr. Karin Larsson, Ms. Steff Webb, Ms. Eva Kovacs and Ms. Jorein Terlouw for their support and hospitality during my stay in the four hosting countries. My best wishes to my classmates from around the globe and the lovely people whom I met in the four countries for sharing their friendship and knowledge during the last one and half years in Europe. Finally my deepest gratitude to my parents for their support and encouragement during my stay away from home.

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Table of contents

1. Introduction ................................................................................................ 10 1.1. Background of the Problem........................................................................10 1.2. Problem Statement ..................................................................................... 13 1.3. Research Objectives and Questions............................................................ 17 1.4. Hypothesis.................................................................................................. 18 1.5. Research Stages.......................................................................................... 19 1.6. Limitations of the study.............................................................................. 20

1.6.1. Socio - Political................................................................................. 21 1.6.2. Overall Assessment .......................................................................... 21 1.6.3. Data Quality...................................................................................... 22

2. Literature Review....................................................................................... 23 2.1. Terrain Analysis and Remote Sensing as a tool for reservoir site selection .

.................................................................................................................... 23 2.2. Elevation data processing routines in support of reservoir site selection ... 26 2.3. Hydrological characteristic of the main drainage in the study area............ 27 2.4. Limitations of water transfer and possible consequences........................... 32 2.5. Summary .................................................................................................... 33

3. Materials and Methods ............................................................................... 35 3.1. Study area................................................................................................... 35

3.1.1. Basin Characteristics ........................................................................ 35 3.1.2. Geomorphology ................................................................................ 36 3.1.3. Geology ............................................................................................ 39 3.1.4. Landuse / Landcover / Infrastructure................................................ 42

3.2. Satellite Data, Maps and Ancillary Data used ............................................ 42 3.3. Methodology .............................................................................................. 43

3.3.1. Terrain Analysis and Reservoir Site Location.................................. 44 3.3.2. Reservoir Volume / Reservoir Capacity Estimation ......................... 46 3.3.3. Criteria for Optimal Routing............................................................. 49

3.4. Field Work.................................................................................................. 49 3.5. Summary .................................................................................................... 50

4. Results and Discussions ............................................................................. 51 4.1. Results of Post Field Analysis.................................................................... 51

4.1.1. Terrain Analysis / Multi Criteria Analysis Results ........................... 51 4.1.2. Reservoir Volume / Capacity Estimation Based on Iterative

Numerical Propagation Method........................................................ 56 4.1.3. Optimal Route Selection of Link Canal............................................ 68

4.2. Assessment of IBWT.................................................................................. 71

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4.3. Limitations of the Methodology................................................................. 73 4.4. Summary .................................................................................................... 74

5. Conclusions and Recommendations........................................................... 76 5.1. Specific Conclusions .................................................................................. 76 5.2. Limitations of Research.............................................................................. 78 5.3. Recommendations ...................................................................................... 80

References ................................................................................................................ 82 Online Resources:..................................................................................................... 85 Appendices ............................................................................................................... 86

Appendix – A (Landuse Map and Rain Gauge Data)........................................... 86 A1: Rainfall data from rain gauge station at Jalpaguri town, Jalpaiguri , West Bengal, India (unnamed Government Report, 2000). ...................................... 86 A2: Rainfall data from rain gauge station at Alipurduar town, Jalpaiguri, West Bengal, India (unnamed Government Report, 2000). ...................................... 87 A3: Rainfall data from rain gauge station at Hasimara town, Jalpaiguri, West Bengal, India (unnamed Government Report, 2000). ...................................... 87 A4: Rainfall data from rain gauge station at Banarhat town, Jalpaiguri, West Bengal, India (unnamed Government Report, 2000). ...................................... 87 B5: Landuse / Landcover map of the study area, Jalpaiguri district, West Bengal, India.................................................................................................... 88

Appendix – B (Reservoir Capacity Estimation) ................................................... 89 B1: Areal extent of reservoir for different dam heights on tributary of R. Jaldhaka superimposed on IRS P6 LISS III, Nov. 2005 data. ......................... 89 B2: Areal extent of reservoir for different dam heights on R. Murti superimposed on IRS P6 LISS III, Nov. 2005 data. ........................................ 89 B3: Areal extent of reservoir for different dam heights on R. Torsa superimposed on IRS P6 LISS III, Nov. 2005 data. ........................................ 90 B4: Areal extent of reservoir for different dam heights on R. Kaljani superimposed on IRS P6 LISS III, Nov. 2005 data. ........................................ 90 B5: Areal extent of reservoir for different dam heights on tributary of R. Jaldhaka (upstream) superimposed on LANDSAT TM, Nov. 1991 data. ....... 91 B6: Reservoir Storage Capacity Curve for different dam heights on tributary of R. Jaldhaka (upstream) as derived from Digital terrain model. ....................... 91 B7: Areal extent of reservoir for different dam heights on R. Torsa (upstream) superimposed on LANDSAT TM, Nov 1991 data. ......................................... 92 B8: Reservoir Storage Capacity Curve for different dam heights R. Torsa (upstream) as derived from Digital terrain model............................................ 92 B9: Areal extent of reservoir for different dam heights on R. Raidak superimposed on IRS P6 LISS III, Nov 2005 data. ......................................... 93

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B10: Reservoir Storage Capacity Curve for different dam heights R. Raidak as derived from Digital terrain model. ................................................................. 93 B11: Areal extent of reservoir for different dam heights on R. Sankosh superimposed on LANDSAT TM, Nov 1991 data. ......................................... 94 C12: Reservoir Storage Capacity Curve for different dam heights R. Sankosh as derived from Digital terrain model. ............................................................. 94

Appendix – C (Water Utilisation) ........................................................................ 95 D1: Estimated water utilisation for irrigation and human consumption in 3 scenarios considering 10% reduction of reservoir capacity and 10 % loss due to evaporation and conveyance. ...........................................................................95 C2: Estimated water utilisation for irrigation and human consumption in 3 scenarios considering 20% reduction of reservoir capacity and 10 % loss due to evaporation and conveyance. ...........................................................................96 C3: Estimated water utilisation for irrigation and human consumption in 3 scenarios considering 30% reduction of reservoir capacity and 10 % loss due to evaporation and conveyance. ...........................................................................97 C4: Estimated water utilisation for irrigation and human consumption in 3 scenarios considering 40% reduction of reservoir capacity and 10 % loss due to evaporation and conveyance. ...........................................................................98

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List of figures

Figure 1-1 Ganga -Brahmaputra-Meghna basin (Rahaman, 2005)........................... 14 Figure 1-2 Corridor for Canal linkage in Indian Territory (Siliguri Chicken Neck).14 Figure 1-3 Proposed inter basin water transfer schemes in the Himalayan component (http://www.nwda.gov.in)......................................................................................... 15 Figure 1-4 Map showing the trend of structural elements in the study area ............. 16 Figure 2-1 Baseline information required for potential reservoir site location (Bose and Gupta, 2003). ..................................................................................................... 24 Figure 2-2 Activity Flow Chart (Bose and Gupta, 2003). ........................................ 26 Figure 3-1 Location of the Study Area in the state of West Bengal, India. .............. 36 Figure 3-2 Field photograph showing some of the geomorphological characters of the study area (AFP = Active Flood Plain, RT = River Terrace, and Mid Altitude Intermediate Fan)...................................................................................................... 37 Figure 3-3 Major Rivers and their tributaries in the study area ................................ 38 Figure 3-4 Lineaments identified from IRS P6 LISS III data of 15th Nov 2005 and DEM generated from SRTM data (90 m resolution) superimposed on geology of the study area.................................................................................................................. 40 Figure 3-5 Overall research methodology. ............................................................... 44 Figure 3-6 Methodology for terrain analysis and potential reservoir site location ... 47 Figure 3-7 Flooded area of reservoir detected using topography and connectivity operator (Fazlur Rahman, 1994)............................................................................... 47 Figure 3-8 Methodology for reservoir map creation and volume calculation from DEM using iterative propagation method (Fazlur Rahman, 1992)........................... 48 Figure 4-1Composite Suitability Map of Potential Reservoir Sites generated using Multi criteria............................................................................................................. 53 Figure 4-2Location of reservoirs (Scenario 1) based on multi criteria analysis and hydrological character of the drainage of the area....................................................54 Figure 4-3 Location of reservoirs (Scenario 2 and 3) based on elevation information of the area from SRTM (90 m resolution) data. ....................................................... 55 Figure 4-4 Numerical example of iterative propagation process to determine reservoir extent. Reservoir level is assumed to be 50 (Fazlur Rahman, 1994). ........ 57 Figure 4-5 Drainage map and catchment boundaries of rivers of the study area derived from SRTM Version 3 data of 90 m resolution (http://srtm.csi.cgiar.org.) using ILWIS 3.3 (ITC, 2001) ................................................................................... 58 Figure 4-6 Areal extent of reservoir for different dam heights on R. Teesta superimposed on IRS P6 LISS III data..................................................................... 59 Figure 4-7 Reservoir storage capacity curve for different dam heights on R. Teesta as derived from digital elevation model. .................................................................. 59

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Figure 4-8 Reservoir storage capacity curve for different dam heights on Jaldhaka tributary as derived from digital elevation model.....................................................60 Figure 4-9 Reservoir storage capacity curve for different dam heights on R. Murti as derived from digital elevation model........................................................................ 60 Figure 4-10 Reservoir storage capacity curve for different dam heights on R. Torsa as derived from digital elevation model. .................................................................. 61 Figure 4-11 Reservoir storage capacity curve for different dam heights on R. Kaljani as derived from digital elevation model. .................................................................. 61 Figure 4-12 Estimated dimensions of the proposed link canal ................................. 69 Figure 4-13 Map showing the proposed canal route superimposed on landuse / landcover. ................................................................................................................. 70 Figure 4-14 Estimated irrigated area if the water was used only for irrigation in 3 scenarios considering full capacity and subsequent reduction of reservoir capacity (10% , 20%, 30% and 40%) due to siltation and 10 % loss due to evaporation and conveyance together. The first bar (solid black) indicates the irrigated area without considering any loss in all the 3 scenarios. ............................................................... 72 Figure 4-15 Estimated irrigated area in 3 scenarios considering reduction of reservoir capacity (10% , 20%, 30% and 40%) due to siltation and 10 % loss due to evaporation and conveyance together using 40% of the available water for the purpose of irrigation. ................................................................................................ 72 Figure 4-16 Estimated number of days the water will last for a rural population of 12.34 million with a consumption of 70 litres / day or an urban population of 6.4 million with a consumption of 135 litres/day in 3 scenarios considering reduction of reservoir capacity (10%, 20%, 30% and 40%) due to siltation and 10 % loss due to evaporation and conveyance together....................................................................... 73

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List of tables

Table 1 Reservoir Location criteria based on terrain analysis (Yusof and Baban, 2000)......................................................................................................................... 25 Table 2 Details of major river basin in study area....................................................28 Table 3 Gradient of major rivers in the study area (Physiographic region wise)...... 30 Table 4 Mean annual sediment load of major rivers of study area. .......................... 30 Table 5 Calculated peak discharge of rivers in study area........................................ 32 Table 6 Rivers in Brahmaputra and Ganga basin. .................................................... 35 Table 7 Morphostratigraphic Units of West Bengal (GSI unpublished report). ....... 41 Table 8 Data used for generation of thematic maps. ................................................ 43 Table 9 Key Criteria for dam site selection and the underlying condition considered for different thematic information used for MCA. ................................................... 45 Table 10 Initial results during field work for terrain analysis / multi criteria analysis................................................................................................................................... 50 Table 11 Mean, median and standard deviation of rainfall data at four recording stations of the study area. ......................................................................................... 62 Table 12 Water availability in 1st Scenario............................................................... 64 Table 13 Water availability in 2nd Scenario. ........................................................... 65 Table 14 Water availability from each reservoir in 1st Scenario considering different transfer rates. ............................................................................................................ 66 Table 15 Water availability from each reservoir in 2nd Scenario considering different transfer rates. ............................................................................................................ 66 Table 16 Water availability in 3rd Scenario. ............................................................. 67 Table 17 Water availability from each reservoir in 3rd Scenario considering different transfer rates. ............................................................................................................ 68 Table 18 Estimated dimensions of the proposed link canal using reiterative method (Mannaerts, 1992)..................................................................................................... 69

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Abbreviations

ASTER Advanced Spaceborne Thermal Emission and Reflection

Radiometer CVP Central Valley Project DEM Digital Elevation Model GBM Ganga – Brahmaputra-Meghna GIS Geographic Information System GSI Geological Survey of India GTOPO Global Topographic Data G-DEM Global Digital Elevation Model IBT Inter Basin Transfer IBWT Inter Basin Water Transfer ILR Inter Linking of Rivers ILWIS Integrated Land and Water Information System IRS Indian Remote Sensing Satellite IWRM Integrated Water Resource Management LISS Linear Imaging Self Scanner MCA Multi Criteria Analysis NWDA National Water Development Agency RL Reduced Level SOI Survey of India SRTM Shuttle Radar Topography Mission TA Terrain Analysis TM Thematic Mapper TMLC Teesta – Mahananda Link Canal USD United States Dollar UTM Universal Transverse Mercator WGS World Geodetic System

GEOINFORMATICS FOR INTER BASIN WATER TRANSFER ASSESSMENT

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1. Introduction

1.1. Background of the Problem

Fresh water availability and demand is unequally distributed over time and space. Availability of fresh water has more or less remained constant despite natural temporal fluctuation (Gupta and Zaag, 2007); the demand for clean water is ever increasing. In some areas of the world, especially regions of high population density and intense economic activity, the demand has overtaken the supply. Gupta (2007) has considered Allan’s (2003) view, who argued that with increasing demand of water, surpassing the supply, an integrated water resource management approach is required to balance environmental, social and economic considerations in the decision making process rather than conventional technique of “hydraulic mission” to increase water use efficiency and enable the society to achieve sustainability and optimise economic return on water. Gupta (2007) has also pointed out that in river basins where demand outstrips supply, new sources of water has to be found out either by desalinising sea water or transferring water from a neighbouring basin where it is in surplus by Inter Basin Transfer (IBT) which is becoming a dominant solution. Inter Basin Water Transfer (IBWT) has been undertaken in different countries with various environment and socio-economic implications for instance in USA, China and Russia. India is a sub-continent of grand scale and as a result challenges it faces are also of grand scale. The water resources are unequally distributed due to unequal spatial and temporal distribution of rainfall. This leads to drought in some part of the country while flood creates havoc in other parts. Providing water during droughts and preventing floods in seasons of excess availability has always been a challenge. The Indian River system which forms the lifeline of the country can be divided into two components – the Himalayan components which have the water source in the glaciers of the Himalayas as well as the monsoon rains while the other is the peninsular component with water source mainly from the monsoon rains. This leads to surplus water in the Himalayan component and partial deficit in the peninsular component especially during the dry season. India receives about 4000 billion m3 of water as precipitation (NCIWRDP, 1999), but a major part of this is received in the


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Himalayan catchment comprising the Ganga – Brahmaputra – Meghna (GBM) basin as a result of which the north-eastern part of the country has more precipitation than the southern or the western parts (Bandyopadhyay and Perveen, 2003). This results in inundation of agriculture fields in areas of high precipitation and water scarcity and crop failures in the areas of low precipitation. This has led to formulation of various laws and policies from historical times.

Water laws in India dating back to 4000 years or more reflect both the changes brought by Muslim and British invaders on one hand and traditional Hindu laws on the other. Thus a dichotomy exists between laws in paper and the laws that are followed (Singh, 1991; Gupta and Zaag, 2007). Though traditional focus has been on small scale community management, but new management methods are required due to increasing population pressure, industrialization and subsequent globalisation. In India water is a state subject according to the 1945 Indian constitution. Interstate controversies over water sharing have led to various acts on Water dispute. But due to vastness of the country and unequal distribution of rainfall and water supply India’s first national water policy was framed in 1987 and subsequently amended in 2002 which states that: ‘‘Utilisable water resources need to be increased using non- conventional methods for utilization of water such as inter basin transfers, artificial recharge of ground water and desalination of brackish or sea water along with traditional water conservation practices like rainwater harvesting, including roof-top rainwater harvesting. Promotion of frontier research and development, in a focused manner for these techniques is necessary’’ (Article 3.2 of the National Water Policy, 2002). The national water policy in Article 3.5 also points to a national perspective to undertake such inter basin water transfer. The logic behind the policy of water transfer is based on the view that surplus water in some river basin if transferred to water deficit basins can permanently solve the problems of drought and water scarcity (Bandyopadhyay and Perveen, 2003). This gave the go ahead to the National Water Development Agency (NWDA) to explore inter basin water transfer linking the Himalayan rivers and the peninsular rivers to reach a balance of water resources. The NWDA studies came up with 30 possible links, 14 in the Himalayan component and 16 in the Peninsular component which bears some reflection on an early proposal in 1972 by K.L. Rao for the National Water Grid (http://www.nwda.gov.in) and in 1977 by Captain Dastur for the Garland Canal Project, which were shelved due to lack of feasibility, desirability and viability (Chakrabarti, 2004).


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The main aim of Interlinking of River (ILR) project in India is to reduce regional imbalance in the availability of water over entire country and the major objective is to increase irrigation potential for increasing food grain production and mitigate floods and drought in the country besides the following specific benefits (Postel and Richter, 2003):

• Irrigation of 34 million hectares of land.

• Potable water for rural & urban areas and industrial water-supply.

• 34,000 MW power generations through hydroelectric generators.

• Inland navigation through the network of rivers.

• Ecological up gradation and increased tree farming.

• Sizeable employment generation.

• National integration. The total cost of the project as estimated in 2002 is to the order of 122.7 billion USD (Goyal, 2003). This led to a major debate between scientific community and the political sphere. Till date no technical pre feasibility or feasibility study has been undertaken or made public for open professional assessment of many major links specially those of the Ganga and Brahmaputra basin (the two major river basins in India). Floods are a recurring phenomenon in these two river basins and thus have surplus water resources. If these water resources can be tapped by storing in reservoirs, then transferring these excess water resources from these two basins to other parts of the country via link canals, significant reduction in regional imbalances can be achieved. A link between the rivers Teesta, a tributary of the river Brahmaputra and the Mahananda, a tributary of the river Ganga already exists. Two barrages one each on the river Teesta and the river Mahananda acts as reservoirs for the excess water resources available in these two rivers and is used both for irrigation and hydroelectric power generation. The existing canal called the Teesta – Mahananda Link canal (TMLC), can be used as a link between the proposed link canals in the Brahmaputra basin and the eastern part of the Ganga basin in the ILR project for further transportation to the peninsular India in the south. The politicians on the other hand are trying to reap the benefit on the advantages the project is likely to bring without throwing light on questions like: Will such linking actually prevent drought? Or merely transfer drought? What will be the extent of displacement and provision for rehabilitation? Is there really a surplus of water? Are there any alternatives (small scale) rather than the grand scale engineering work? Besides the above socio-economic aspects, the terrain condition and the basin characteristics (geomorphology, geology and structure) are important aspects of the


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ILR project as India has a varied terrain condition from the north to the south. Even if the economics permit the other questions that need to be answered are: Are the terrain conditions suitable enough to undertake such transfer? What will be the amount of water available? What types of structures are required and their possible locations to undertake such transfer? What is the effect of the transfer on the environment of the exporting, transporting and receiving basins? Another major issue that need to be addressed is the consequence of such a transfer and to find the optimal route of the canals. Thus the ILR project needs to be looked at from a multi disciplinary approach. Studies related to feasibility of the projects from terrain analysis point of view, amount of excess water available in a river basin, environmental impact, financial obligation and social impact need to be done. The scope of this work mainly aims to assess the amount of water available (i.e. volume) for transfer, the physical conditions for location of reservoirs as well as the area affected by temporal storage in parts of the Brahmaputra and the Ganga basin in eastern part of India.

1.2. Problem Statement

The Ganga and the Brahmaputra are two major river basins in India with surplus water and flooding is a perennial problem in this region. These two river basins in regional scale is a part of larger Ganga – Brahmaputra – Meghna basin. Part of these 3 river basin falls within present Bangladesh (Figure 1-1). According to Secretary General, International Commission for Irrigation and Drainage and Secretary, Task Force, Interlinking of Rivers, Govt. of India (Thatte, 2007) , the annual water availability per capita in the Brahmaputra basin is 18,400 m3 which is the maximum amongst all Indian rivers. The linking of rivers in the Brahmaputra basin and eastern part of Ganga basin will lead to an additional water availability of 43 billion m3 from the Brahmaputra basin and 38 billion m3 from the Ganga basin which can be stored behind dams for transfer through the link canals between the two catchments for further transportation to the peninsular India. Linking these two rivers can be done either through Bangladesh or through the narrow stretch in the Indian Territory (Figure 1-2), the so called Siliguri chicken neck (Purkayastha, 2003). The first option has been rejected by Bangladesh government.


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Figure 1-1 Ganga -Brahmaputra-Meghna basin (Rahaman, 2005).

Figure 1-2 Corridor for Canal linkage in Indian Ter ritory (Siliguri Chicken Neck).

The ILR project of the National Water Development Agency has planned the linking of the rivers also in terms of the Himalayan component (14 links) and peninsular component (16 links). Amongst the 14 links stated in the Himalayan component of the ILR project, the tributaries of the eastern part of Ganga and the Brahmaputra

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basin can be linked by one of the two stated links in the ILR plan as seen in Figure 1-3.

• Link No 10. Manas – Sankosh – Teesta – Ganga.

• Link No 11. Jogighopa – Teesta –Farakka (alternate).

Figure 1-3 Proposed inter basin water transfer schemes in the Himalayan component (http://www.nwda.gov.in).

These two components of the ILR plan pass through the Himalayan foothill region which is structurally controlled. The important structural elements are the (Figure 1-4):

• E-W trending faults/ lineaments parallel to the Himalayan trend.

• Transverse faults trending N-S, NW-SE/NE-SW running across the Himalayan trend.

Geological studies carried out in this region indicate the presence of these faults and lineaments and few amongst these faults and lineaments are proved to be active in geologically recent times while a few others are presumed to be active. If a fault is active then geodetic levels on either side of the fault tend to change. Studies in this area indicate changes in height above mean sea level at various points to the east and west of the bifurcation of river Torsa after taking into consideration the human error and slight change in location of points of measurement of Reduced Level (RL) values.

10

N Not to Scale


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Figure 1-4 Map showing the trend of structural elements in the study area

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Thus the neotectonic network of transverse and parallel faults / lineaments to the Himalayan trend is considered to be a major contributor to the instability of this region (Das and Chattopadhyay, 1993). Any movement or adjustment along these structural elements will have an effect on river geomorphology of the area. Eroded materials from uplifted area are deposited in the down faulted depressions leading to aggradation and shifting of rivers. This shifting nature of the rivers in this region can be observed in the river Teesta which is part of the above two links (see also Figure 1-3). Thus a very high mean annual rainfall in this region along with the above factors is also one of the primary causes of flood in this region over ages. Similar situation exist in the Ganga River which at places has a lateral shift of about a kilometer in one rainy season. Considering these facts the question of how the link is to be designed comes into centre stage. How the alignment of the canals should be planned so as to take into account the river’s changing characteristics and the surrounding terrain condition? Besides the above factors related to the terrain characteristics another aspect that should be taken into account is the location of the reservoirs to obtain a considerable storage capacity. Last but not the least; can the resources from the river be harvested by maintaining the natural gradient as pumping is too expensive? Both the Ganga and the Brahmaputra basin are shared by Bangladesh, Bhutan and Nepal with Bangladesh being on the downstream end of the system. As a result of this, issue of water sharing between riparian countries will be an important aspect if the ILR project is undertaken in this basin, but it is outside the scope of this work.

1.3. Research Objectives and Questions

The main objective is to undertake an assessment of inter basin water transfer using geoinformation as a source for generating inputs for terrain analysis and multi criteria analysis to figure out potential sites for reservoir location. The research also aims at calculating storage capacity of those reservoirs using elevation data of Shuttle Radar Topographic Mission (SRTM) as one of the inputs and consequences of the storage viz. water available for irrigation, human consumption and other purposes based on some assumptions of precipitation, discharge and also considering losses during transfer as well as decrease in reservoir capacity due to sedimentation. The research also intents to delineate an optimal route of the link similar to the two links mentioned in the ILR plan for transferring the stored water based on the reservoir location as well associated terrain condition to enable joining to the existing Teesta – Mahananda Link Canal (TMLC). The following specific objectives and the research questions are:


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Specific Objective Research Questions

1) To study the geomorphology, geology, landuse and drainage characteristics of the area using multi temporal and multi sensor satellite data.

1) What are the relevant geomorphological, geological, landuse and drainage characteristics for IBWT in the study area?

2) To find suitable reservoirs site(s) and determine the available storage capacity in the major tributaries traversing the study area using a numerical method and available DEM data.

2a) Is it possible to calculate storage capacity at a particular location using an iterative numerical propagation method and available DEM data? 2b) Can elevation information from SRTM Version 3 (http://srtm.csi.cgiar.org.) data be used for reservoir site characterization?

3) To find the possible alignment(s) of the link canal(s) for the inter basin water transfer.

3a) What are the possible routings of the link canal(s)? 3b) On what criteria are the alignments of the link canal(s) being proposed in the research? Is it possible to quantify the possible scenarios in terms of canal dimensioning? 3c) Which alignment is the most optimal for connecting the proposed reservoirs in the research?

4) To evaluate the possible consequences of the stored water (volume) in terms of usage assuming a definite discharge, losses during transportation and decrease in reservoir capacity.

4) What are the consequences or different scenarios of the usage of the volume of water available for transfer in the study area?

1.4. Hypothesis

Terrain analysis – H0: If thematic data and elevation data are used separately for terrain analysis

both of them individually can locate the potential reservoir sites accurately. H1: If thematic data is merged with elevation data for terrain analysis, the

derived data can locate the potential reservoir sites accurately.


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The null hypothesis may be reasoned as follows: To locate potential reservoir site accurately the knowledge of both structural features (e.g. slope aspect lineaments and faults) and non structural features (e.g. geomorphology, drainage and landuse / landcover) of that particular area should be known. The thematic data gives information of only non structural features and the elevation data provides information about structural features. Therefore, if separately used, the thematic data and elevation data cannot indicate the accurate locations of the potential reservoir site. The alternative hypothesis may be reasoned as follows: As thematic data has no elevation information so usage of thematic data in conjunction with elevation data can be appropriate in locating potential reservoir sites in a terrain. 2. Reservoir Capacity Estimation – H0: SRTM data is not appropriate for reservoir capacity estimation. H1: Reservoir capacity can be determined by iterative propagation method

using SRTM data. The null hypothesis may be reasoned as follows: SRTM Version 3 data (http://srtm.csi.cgiar.org.) is a near global dataset averaged to 90 m resolution and may not represent the actual terrain configuration. Radar reflective surface takes into account natural vegetation and manmade artefacts, so true ground elevation are not accurately represented in the SRTM data (http://srtm.csi.cgiar.org.). Thus reservoir capacity of potential reservoir sites may not be correctly determined using this data. The alternative hypothesis may be reasoned as follows: SRTM Version 3 data (http://srtm.csi.cgiar.org.) can be used as an input for an iterative propagation method for a first assessment for reservoir characterization and capacity estimation.

1.5. Research Stages

The research is being carried out in the following phases:


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1. The first phase includes literature review on inter basin water transfers undertaken in various parts of the world and the criteria on the basis of which those transfers is undertaken. Some study is also undertaken on flood models and reservoir site selection process using DEM data. This phase also included framing of research objective, research question and preparation of field work including satellite data collection and pre-processing.

2. The second phase includes field work in India for about 5 weeks (Sept – Oct

2007) covering the district of Jalpaiguri in the northern part of the state of West Bengal, India. Some thematic data (landuse, geomorphology, geology, drainage) were also generated at the Geoinformatics and Remote Sensing Cell, Department of Science & Technology, Govt. of West Bengal, India as a part of their internal project. The field work also involved ground truthing of the thematic maps as well as site visits to some potential reservoir locations and probable corridor of link canal to have a first hand knowledge of prevailing terrain condition.

3. The third phase undertakes terrain analysis / multi-criteria (TA/MCA) analysis

using various thematic maps viz. geology, geomorphology, drainage, landuse, generated in the second phase and DEM derived from SRTM Version 3 data (http://srtm.csi.cgiar.org.) to locate potential reservoir sites on the main tributaries of the Brahmaputra river viz. R. Jaldhaka, R. Torsa, R. Raidak and R. Sankosh. An iterative propagation method for determination of storage capacity of the potential reservoirs is also undertaken to delineate the best suitable reservoir sites to assess the potential volume available for abstraction. The optimal canal route based on reservoir location and associated terrain condition is also determined in this phase with an ultimate aim of integrating it with the existing TMLC.

4. The last phase aims to look at the consequences of the abstraction and transfer

of water available in relation to overall catchment and runoff using catchment baseline data available for usage in irrigation or human consumption. Some assumptions regarding discharge, consumption, transfer loss and reduction in reservoir capacity over time are considered to assess the above consequences.

1.6. Limitations of the study

The inter basin water transfer assessment in the study area is not free of limitations. The limitations are both technical and socio-political. A discussion has been undertaken on the above limitations in the study area.


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1.6.1. Socio - Political

In a developing country like India, infrastructure projects generally give rise to a lot of socio-political controversies which mainly arises from the track record of the government and project developers from the past. Past river valley projects like Bhakra, Hirakud, Pong and Gandhisagar have displaced 3.3 to 5.0 million people and a large percentage of this displaced people have not yet been resettled properly (Thakkar, 2007). Thus a mammoth project like ILR is likely to bring out this aspect of displacement of population from a section of the social and political sphere. This aspect is one of the major limitations of this study and has not been taken into consideration. Another aspect which has come up is the financial implication of this project which is ¼ of India’s annual GDP. Such huge cost implication will result in borrowing from foreign funding agencies which might result in the country falling into a debt trap. The project is also likely to bring a boon to corruption. Besides estimates show that about 18 billion USD are required alone for completion of existing water resources project in India with many languishing due to lack of funds (Postel and Richter, 2003). Another major limitation of this project, especially in the study area is that most of the rivers in THE Ganga – Brahmaputra basin are transboundary rivers and implementation of a project of diverting huge amount of water needs a lot of legislation between sharing countries before implementation of the project. Reservoir construction is likely to affect valleys of neighbouring upstream countries like Nepal and Bhutan. Thus the socio-political limitation of this study is mainly concentrated around displacement cost, financial implication and addressing of transboundary water sharing issues which are already in place from past project experience in this region.

1.6.2. Overall Assessment

The overall assessment of inter basin transfer is always a multidisciplinary one. It requires involvement of earth scientists, environmentalist, social scientist, planners, engineers and financial experts. The scope of this research is only limited to terrain analysis for suitable reservoir site selection using thematic maps generated from multispectral satellite data and estimating reservoir capacity at potential reservoir site. It also looks at the consequence of the water available and the optimal route through which it can be transferred. A water transfer canal already exists between


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the Brahmaputra and the Ganga basin from the River Teesta to the River Mahananda. The optimal route of the proposed canal aims at transferring the water from tributaries of the Brahmaputra to this already existing canal of the Teesta barrage project in the study area. Thus the present study looks at only a fraction of an overall inter basin water transfer assessment / feasibility study.

1.6.3. Data Quality

SRTM data is used as elevation data for terrain analysis as well as an input for the iterative propagation method for reservoir capacity estimation. SRTM Version 3 data (http://srtm.csi.cgiar.org.) is a global data with a resolution of 90m. Moreover radar data estimates ground elevation by means of time of travel of the signal between sensor, target and back to sensor. The C-band frequency used is as for example opaque for dense vegetation. Thus presence of canopy cover / human artefacts over ground surface at these locations gives a wrong estimation of ground elevation. Studies have indicated that SRTM data do not represent a surface properly due to its coarse resolution. Though SRTM data is less precise than topographic data available in state or regional level, but state or regional level elevation data compiled from different sources when integrated for a large river basin incorporates a lot of uncertainty (Haase and Frotscher, 2005). Thus SRTM data can be considered as a better option for application in large river basin as it is a seamless data available in a global scale. Moreover topographic data is restricted in many countries of the world including the study area in India. In such cases global data like SRTM data are useful to carry out hydrological modelling in large river basins. .


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2. Literature Review

Inter basin water transfer requires harnessing of water resources in a sustainable and equitable manner so that minimum damage is inflicted to the environment as well as the society as a whole (Dasmunsi, 2005). As a part of this inter basin water transfer, assessment needs to be undertaken on the terrain characteristics, review of the tools for such assessment for instance remote sensing and GIS, data processing techniques, drainage characteristics of the study area and possible limitations and consequences of such water transfer. The literature review looks into these aspects of the study.

2.1. Terrain Analysis and Remote Sensing as a tool for reservoir site selection

Reservoir is a constructed area where water is accumulated and dam is a structure which holds back the water (Brassington, 1995). Therefore, during site selection examination of both the dam site as well as the reservoir site is required. Though the engineering considerations are one of the major aspects in reservoir and dam site location but after the United Nations Conference on Environment and Development in 1972, focus has shifted on local and regional environment as well as social impact of proposed reservoir locations (Baban and Wan-Yusof, 2003). This requires handling of a large dataset in an effective system which will assist decision makers (Baban and Flannagan, 1998). Remote Sensing and GIS is one such system which have the ability to handle, analyse and manipulate huge data sets pertaining to reservoir site selection. Besides, it also enables decision makers to have a regional view of the potential sites in a shorter time frame (Baban, 1999). Remote sensing gives a synoptic view of the terrain and helps in identification of geological structures; geomorphological landscape and landuse / landcover pattern which when incorporated in a GIS framework enables decision makers to have several alternatives and scenarios indicating the most suitable and less suitable locations for development (Albers, Dobbins et al., 1991). In reservoir site selection, determination of the areal extent of the reservoir is the most important criteria. This requires knowledge of the physiographic configuration of the potential reservoir and dam site. The physiographic configuration can be


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obtained from various spatial and aspatial dataset (Bose and Gupta, 2003) which include baseline information as can be seen from Figure 2-1.

Figure 2-1 Baseline information required for potential reservoir site location (Bose and Gupta, 2003).

An integrated approach involving study of all principal environmental features like topography, geomorphology, lithology, soil, hydrology /drainage pattern and landuse has been suggested in a landscape approach of terrain classification but geomorphology holds the main key in terrain classification using remote sensing technology (van Zuidam and van Zuidam-Cancelado, 1985).Thus spatial baseline information needs to be generated through terrain analysis and classification with morphogenetic approach (Meijerink, 1988) using Remote Sensing data. Remote Sensing and Geographical Information Systems is the most modern tool for generation of the aforesaid spatial data with temporal changes. Subsequent integration and analysis of the non spatial data along with spatial data help to conclude on "strategic datasets" (i.e. Geoinformation). This enables to give emphasis on type of engineering work that should be carried out (Chakrabarti, 2000). While selecting sites for reservoir the important terrain criteria which need to be taken into consideration includes topography, hydrology, geology, soil, land use/land cover, road network in association with socio-economic and environmental factors (Murphy, 1977; Gismalla and Bruen, 1996). Studies undertaken in Malaysia


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for potential reservoir location based on terrain characters involve multi criteria analysis which is indicated in Table 1:

Table 1 Reservoir Location criteria based on terrain analysis (Yusof and Baban, 2000).

Criteria Consideration

The dam and reservoir site must:

(1) not be located in or within settlement areas Safety

(2) be on granite and/or metamorphic rock Safety

(3) avoid forest reserved areas Resources/Environment

(4) avoid high grade agricultural land value areas Resources/Environment

(5) be at an altitude of between 25-90 m Hydraulic/ Economic

(6) be on a gentle slope of 0o-11o Environmental/Safety

(7) have a sufficient surface area to provide the necessary volume

Consumption/Economic

The thematic layers for the criteria generated through remote sensing technique were overlaid in a GIS environment using Boolean method to find suitable and unsuitable reservoir sites (Yusof and Baban, 2000). It has been found that spatial multi criteria analysis helps in identifying alternatives or options in reservoir site selection with systematic spatial evaluation (Malipa, 2005). Thus studies undertaken indicate that geoinformation gathered from remote sensing satellites in association with topographic data and other ancillary data can be utilised for generation of various thematic maps using visual or digital classification techniques supported by ground truthing. This thematic information can be used for terrain classification using multi criteria analysis techniques in a GIS environment along with non spatial datasets to provide vital information regarding 'vulnerable land units' for geotechnical adjustment (through structural means) and social adaptations (non-structural means) as depicted in Figure 2-2. This type of work flow methodology enables in identification of potential locations of engineering structures.


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2.2. Elevation data processing routines in support of reservoir site selection

Elevation data in the form of digital elevation models / digital terrain models is a representation of the topography. This is responsible for surface flow and accumulation and thus form the most important data input for various hydrological models (Wechsler, 2006). Till date various elevation data have been applied in different hydrological models but most of them are restricted to watershed delineation, morphometric analysis, flood inundation modelling, water level fluctuation, sediment erosion and deposition (Wechsler, 2006). But a very few studies have attempted to quantify or evaluate reservoir capacities, reservoir site selection within large river basins. The basic reason for this is data availability and data quality as these are very critical issues in case of transboundary or large river basins (Haase and Frotscher, 2005).

Multi-date satellite

Data

Ancillary Data (Topographic

Maps, Ancillary data & Reports)

Visual / Digital Interpretation of the images (including updation of existing data)

Preparation of Thematic maps (Drainage, Geomorphology, Landuse / Landcover,

Infrastructure) supported by ground truthing

Terrain analysis &

classification using mutli

criteria analysis(Meijerink, 1988)

Study of theme maps in combination with related aspatial attributes

Framing of decision rule for purpose oriented dataset generation

GIS Environment

Socio-

economic databse

Geotechnical adjustment Social Adaptation

Figure 2-2 Activity Flow Chart (Bose and Gupta, 2003).


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One of the major challenges of elevation data processing is to derive sound parameter sets of terrain and derive hydrological data from it for modelling purpose. The major researches still under process are in the area of uncertainties associated DEM error, derived topographic parameters and associated algorithms, grid cell resolution, DEM interpolation, modification of terrain surface for hydrological application (Lacroix and Martz, 1999; Sun, Ranson et al., 2003; Haase and Frotscher, 2005; Ludwig and Schneider, 2006; Wechsler, 2006). Literature related to elevation data processing routines for reservoir characterization using SRTM data is rare as similar works have been done with a different dataset, approach and technique. Flood modelling has been undertaken by processing elevation data (DEM) in a GIS system and creating simulation model of various scenarios of dyke failure and flood inundation at different river stages in Meghna Dhonagoda irrigation project area in Bangladesh (Fazlur Rahman, 1992). Similar elevation data processing techniques has also been undertaken in evaluating impact of urbanisation in Dhaka city, Bangladesh on storm water runoff and drainage (Maathuis, Mannaerts et al., 1999). In both these cases elevation information from DEM has been used and modified to find the extent of spread of water in various case scenarios of failure of dyke of different dimension and expected urbanization trend respectively. The present research follows the similar procedure, where elevation information would be used to determine reservoir capacity by creating various scenarios of different dam heights on the river bed by modifying the DEM in a GIS environment instead of flood inundation by creating various scenarios of failure of dykes of different dimension or change in urban sprawls.

2.3. Hydrological characteristic of the main drainage in the study area

A river channel at any location reflects upon the geomorphology, geology, hydrology and climate of the drainage basins that may be extended hundreds of kilometers upstream. The present shape, size and pattern of a stream or a river is the outcome of short and long term changes of various factors influencing its morphology. One of the various factors influencing river morphology is the hydrological characteristics, which include both discharges of water in the channel as well as sediment load being carried by the river from the upstream areas (unnamed government report, 2000). The river system in the study area (Figure 3-3) can be divided into two systems, one belonging to the Brahmaputra river system and another to the Ganga river system though the major part of the study is concentrated to the Brahmaputra river system, a


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small part of the Ganga river system falls (The Mahananda) in our study area for IBWT. The major rivers in study area within the Brahmaputra river system are:

1. The Teesta and its tributaries 2. The Jaldhaka and its tributaries 3. The Torsa and its tributaries 4. The Raidak and its tributaries

The review will focus on hydrological characteristics of these main rivers. The details of the major drainage basins in the study area are described in Table 2 (unnamed government report, 2000).

Table 2 Details of major river basin in study area.

River Basin Total Catchment

(km2) Area in Study area

(km2) % in study area

Teesta 12,159.00 3225 27 Jaldhaka 5020.00 3753 75 Torsa 6407.00 2367 37 Raidak 5502.00 807 15

The origin of all the above major rivers are the glaciers and lakes in Sikkim, Tibet and Bhutan and they flow through the Himalayas into the sub-Himalayan region of West Bengal, India a part of which falls in the study area. The rivers then flow through the piedmont zone into the alluvial plains. These alluvial rivers are classified as stable, depositing and eroding as per the sediment load. Generally they have a tendency to deposit at the banks or bed and eroding the stream bed at different geomorphic divisions (Biswas, 2000). The easily recognizable stream pattern is braided and at few sections meandering. The braided streams have islands of sediments, sometimes with permanent vegetation but they are part of the one of the many single large channels in a multiple channel system on an alluvial surface (Dasgupta, 1993). Studies have been undertaken on the planform nature of the rivers in the study area based on discharge of water, type of sediment load and the channel slope. The degree of meandering or sinuosity has also been related to sediment load as well as the percentage of clay and silt in the bed material load of the rivers. The main hydrological characters of each of the four major rivers in the study area are explained below (unnamed government report, 2000):


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Teesta River: The River is unique in its complex and diverse drainage characteristics. The catchment has a complex hydrographic network of branching streams and its temporal variation in flow manifests watershed characteristics which influence its runoff. After the river reaches the plains it incorporates outfalls from various tributaries which carry a huge amount of silt along with sand and deposition of silt is a common phenomenon during slack flow which cause shifts in its courses.

Jaldhaka River: This river has two distinct characteristics, in the upper reaches it passes through gorges and steep slopes causing extensive erosion and as a result when it reaches the foothills and the plains carries with it a huge sediment load. The sediment load which it carries from the hills is deposited in the plains increasing the height of river bed leading to spreading of the river laterally. This leads to changing characteristics of the river course.

Torsa River: The river course is very unstable and has a problem of heavy bank erosion followed by inundation. It has changed it course several times within a 20 km stretch in the west – east direction in the study area. The silt load in this river is heavy during the floods and the cross – section changes every season with a tendency of aggrading bed. The silt deposited in the bed also increases the bed level every year causing inundation and the river has a tendency to get wider by eroding banks due to rising sediment deposits. The main problem arises after the river enters the sub-Himalayan region in the study area. The river is characterized by a number of spill channels which during flood times exceeds their carrying capacity resulting in inundation of adjoining areas. The excessive silt load leads to the inherent braiding character of the streams.

Raidak River: This river is more or less stable and the sediment load in the stream is not excessive and does not increase the carrying capacity, as a result of which the river does not have a migrating nature. It has a number of distributaries two of which joins the river Torsa to the west and the other joins river Sankosh to the east. Till date to harness these alluvial rivers for irrigation, flood management and other water management schemes studies have been undertaken to analyse the hydrological characteristics to understand the behaviour of these major rivers in


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terms of channel slope variation, sediment load, aggradation and degradation. The channel slope varies depending on the terrain characteristics. The study area covers mainly the piedmont zone and parts of the active plain. The gradient of the major rivers in this physiographic regions are shown in Table 3 (unnamed government report, 2000). The basic source of sediments in these rivers is erosion of land surface and to some extent erosion of beds. The sediment load, due to flat slopes of river, is deposited in the river beds forcing the river to have a braided character to find equilibrium condition of discharge, velocity, sediment load and slope. Table 4 (unnamed government report, 2000) shows the mean annual sediment load of the five major rivers in the study area.

Table 3 Gradient of major rivers in the study area (Physiographic region wise).

Serial No.

Rivers Piedmont Zone

(%) Active Plain

(%)

1 Teesta 0.20 0.05 2 Jaldhaka 0.30 0.03 3 Torsa 0.62 0.02 4 Raidak 0.74 0.04

Table 4 Mean annual sediment load of major rivers of study area.

Serial No.

Rivers Million m3

1 Teesta 3.16 2 Jaldhaka 2.68 3 Torsa 1.52 4 Raidak 2.55 5 Sankosh 2.58

Studies have also found that the changing characteristics of these rivers is due to difference in discharge, sediment load, sediment size and slope leading to aggradation and degradation of the river bed. Section of the five major rivers have been studied at multiple locations and it has been observed that average depth of deposition and scour in Teesta varies from + 1 to -18 cm while it is very high in case of Jaldhaka, Torsa and Raidak I (one of the branches of Raidak) which varies from + 6 to + 72 cm, - 17 to + 72 cm and - 10 to 76 cm respectively. Another branch of Raidak, Raidak II has no deposition or scour in the last 15 years while for Sankosh it is about - 165 cm, though the above values are indicative of the hydrologic character of the rivers in the study area (unnamed government report, 2000).


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The changing courses of the rivers in this region are also due to neo-tectonic activities in the interfluve region of Teesta, Jaldhaka and Torsa Rivers. Studies in this region indicate evidence of parallel transverse faults and neotectonic movements along these faults controlling the topography and as a result the drainage pattern of this region. Fault scraps present in this region give rise to various geomorphological, hydrological and physical expressions which result in shifting of rivers on the side of the upfaulted barrier and fanning out on the down faulted side as found at Gorumara where a 20 m scarp face acts as a barrier at the downstream end of the N-S flowing Indong river which changes course abruptly to the east along the scarp trend to meet the Murti river which also has an identical characteristics. The extension of the scarp can be traced into the westward bend of the Jaldhaka river. Thus the barrier which is visually perceptible at Gorumara appears to be continuous on both east and west direction. Observations show that the point of bifurcation of Torsa River is due to the lineament present which is actually a fault. Microtopographic features and records of change of altitude through a period of 30 years results in incision of rivers or splaying out. Thus neotectonic network contributes to instability of the rivers and is one of the reasons for flooding in the region (Das and Chattopadhyay, 1993). The river flow discharge is another important aspect of the hydrological characteristics of drainage. Studies have also been carried out on this aspect also at some strategic locations on the major rivers in the study area and the results are

summarized in Table 5 (unnamed government report, 2000).

As the above rivers are Transboundary Rivers so measured discharge data are not readily available. The peak discharge data in Table 5 are calculated by Dickens formula which gives reasonable result when tested in several basins of North Bengal (Anon, 1972).

Q = CA0.75……………………………. (1)

Where A = catchment area in kilometer square

C = constant depending upon several factors affecting peak discharge. (Anon, 1972) The value of C = 11.5 for North Bengal catchment (Anon, 1972; Dey, 1983).


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Table 5 Calculated peak discharge of rivers in study area.

Calculated peak discharge Serial No.

River Discharge

Calculation Site m3 / sec

1 Teesta Jalpaiguri 20,190 2 Jaldhaka Nagrakata 3,740 NH 31 crossing 8,850 3 Torsa Hashimara 12,690 4 Raidak Bhutanghat 13,240

2.4. Limitations of water transfer and possible consequences

Presently, inter basin water transfers contribute to around 540 Х 109 m3 per year i.e. 14% of all global withdrawals and an additional 940 Х 109 m3 per year is under proposal stages (ICID, 2005). All this together form only a quarter of all water withdrawals by 2025 and so is not considered a significant phenomenon in terms of water resource management. But inter basin water transfer from one catchment area to another has effects both on the donor and the recipient basin. In addition there are limitations of these programs depending on geo-environmental and socio-economic condition of the area. A review has been undertaken on the possible consequences and limitations from various projects that has been carried out or is in process in countries like Russia, USA and China. Experiences of water transfer projects like Central Valley Project (CVP) and Aral Sea Project in countries like USA and Russia or erstwhile USSR respectively have shown possible consequences and limitations thereof (Liu and Ma, 1983; Micklin, 1988; Changming, 1998; Garone, 2004). The major impact is generally found to occur to the ecology of the donor basin. In the CVP it has been found that the delta region where the fresh and saline water mixture takes place, has increased salinity due to low fresh water outflows during dry season due to excessive use of water in the upstream area. These results in sea water intrusion causing problems to farmers, urban communities and wildlife at the downstream end in Contra Costa water district. There has been a change in fish habitat due to less water availability or saline water availability. Loss of wetlands due to low water supply led to a drastic reduction in migratory species resulting in a change in the biodiversity of the area. In areas of water availability excessive irrigation has led to increase in water logging and subsequent salinity causing serious damage. The region also has the problem of increase in concentration of naturally occurring selenium resulting in toxicity to local species as well as deaths (Garone, 2004).


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Similar disastrous effect has been observed due to diversion of water from Aral Sea to support cotton growing industry by the erstwhile Soviet government between 1960 and 1987. This has led to drying up of the lake to two-thirds of its volume, bringing former fishing and agricultural communities depended on it for survival to a verge of death and suffering. Besides human suffering, the environmental degradation created a vast wasteland of glaring white sand blowing into agricultural fields, contaminating the earth and forcing farmers to compensate for declining output by putting more pesticides and fertilizers into the soil poisoning it even more (Micklin, 1988). The south – north water transfer scheme in China which is under planning stage, also focuses on similar problems in the donor and transporting regions. Studies have indicated that the donor region which is economically most developed is likely to have negative impact related in terms of sea water intrusion. It has also been indicated that storage facilities and transfer canals may cause rise in aquifer in regions of high water table leading to secondary salinity of soil. It may have adverse effect on fish population and aquatic life on ponds in the route of the canal, decline in flow in rivers may affect the delta region downstream affecting fisheries and urban population (Liu and Ma, 1983; Changming, 1998). Similar problems have been found or have been predicted in other water transfer projects (Blasco, Marguez et al., 1999; Ballestero, 2004; Azevedo, Porto et al., 2005). Thus the above studies indicate that the consequences and limitations of these water transfer schemes are mostly related to water availability and usage in donor, transfer and receiving basins along with environmental and socio-economic impact. Experts in this field have acknowledged that there may not be any real surplus of water (International Joint Commission, 2000) though deficit or shortage is definitely there. Thus an Integrated Water Resources Management (IWRM) plan is required for balanced and equitable sharing of water as well as sharing of benefits. IBWT transfer programs needs to be assessed for sustainability in terms of better designs, operation rules and governance structures.

2.5. Summary

Thus studies from various literature sources indicate that terrain analysis is an important aspect in reservoir site selection process and it has been considered for reservoir site selection in Malaysia and Tanzania. Multi criteria analysis is one of the major components of this potential reservoir location selection process. Elevation data is also a major component but not many studies have been undertaken related to


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reservoir characterization using SRTM data. The drainage characteristics of the study area indicate presence of neotectonic activities which ultimately control the changing river characteristics and the sediment load content of the rivers. The neotectonics also control the geomorphology and physiography of the region which also contributes to the drainage character. Past studies indicate that similar inter basin water transfer programmes have resulted in disaster. Environmental factors besides socio-political factors are a major concern for future projects in countries like USA, China and Russia.


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3. Materials and Methods

3.1. Study area

The study area for the inter basin water transfer assessment in the present research was located in the Jalpaiguri district of the state of West Bengal in the eastern part of India (Figure 3-1). It is located between 26° 16' and 27° 0' North Latitude and 88° 4' and 89° 53' East longitude covering an area of about 6190 sq. km. The study area is bounded by the foothills of the Himalayas to the North and North West and alluvial plain of the Ganga and Brahmaputra Rivers to the south and east respectively. The climatic condition varies from cold in the northern part to warm and humid in the southern part. Maximum temperature during the summer months is around 39°C while minimum temperature is around 4°C in the winter months. The annual rainfall is also not evenly distributed. The mean annual rainfall varies from 3160 mm in the monsoon season (May – October) to 201 mm in the non-monsoon period (November – April) (unnamed government report, 2000). The study area encompasses parts of the Ganga and the Brahmaputra basin as seen in Table 6; Figure 3-3. River Mahananda is the only major river of the Ganga basin within the study area and the Teesta, Jaldhaka, Torsa, Raidak and Sankosh are the major rivers of the Brahmaputra basin within the study area.

Table 6 Rivers in Brahmaputra and Ganga basin.

Brahmaputra basin Ganga basin

River Teesta

River Jaldhaka River Torsa River Raidak

River Sankosh

River Mahananda

3.1.1. Basin Characteristics

The Teesta Barrage Project and the Mahananda Barrage Project are two important multi-purpose river valley projects in these two river basins and exemplifies inter sub basin water transfer between the Teesta sub basin of the Brahmaputra basin and the Mahananda sub basin of the Ganga basin through a link canal connecting the two


36

rivers over the water-divide in between the two sub basins (Figure 3-3). The excess water in the Teesta sub basin is stored in a reservoir and transferred to the Mahananda sub basin via the Mahananda barrage for irrigation at crucial stage of crop production in Mahananda sub basin. The water is used for other purpose i.e. power generation. The existing canal could be utilized or upgraded as a part of the of the ILR project plan for transferring water from the Brahmaputra basin to the Ganga basin for onward transfer to water deficit area in other parts of the country.

Figure 3-1 Location of the Study Area in the state of West Bengal, India.

A discussion about the terrain characteristics, landuse / landcover and infrastructure is undertaken in the following sections.

3.1.2. Geomorphology

Geomorphologically the area is a part of the Teesta, Jaldhaka and Torsa interfluve belt of North Bengal. Locally the northern part of the area is called ‘Duars’ and is part of the piedmont plains at the foothills of the Himalayas. This gradually grade into alluvial plains further south. The piedmont region is dissected by the major rivers and their tributaries under consideration in this research. The northern part of the area is characterized by fan in fan morphology (Figure 3-2) and the ancient deposits are fluvioglacial in origin as evidenced by huge boulders. Later stage fluvial activities can be observed in the form of terraces where cobble to clay size materials do appear. Rill and gully erosion over a long period of time produced a dissected undulatory surface in the deposits. In the alluvial plains levees, back swamps and ox-bow lakes are dominant comprising mainly of recent sediments. The area was


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distinctly different from overall pattern of the frontal Himalayas and manifested by absence of E-W trending large rivers like the Ganga to the west and the Brahmaputra to the east. Instead, huge fans and floodplains evolved out of southerly flowing rivers like the Teesta and the Mahananda (Das and Chattopadhyay, 1993). Occurrence of salt glands of mangroves in the Siwalik Himalayas to the north of the study area indicated occasional encroachment of an arm of the Bay of Bengal up to this far north (Dasgupta, 1986). With retreat of glacier and expected sea level rise and subsequent upliftment resulted in growth of an extensive quaternary fluvial deposit. The area could be classified into the following geomorphological subdivisions from the north to the south (see also Figure 1-4)

• Denudational Hills

• High Altitude Proximal Fan

• Mid Altitude Intermediate Fan

• Low Altitude Distal Fan

• River Terraces

• Active Flood Plain

Mid Altitude Intermediate Fan

RTAFP

Mid Altitude Intermediate FanMid Altitude Intermediate Fan

RTAFP

Figure 3-2 Field photograph showing some of the geomorphological characters of the study area (AFP = Active Flood Plain, RT = River Terrace, and Mid

Altitude Intermediate Fan).


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Figure 3-3 Major Rivers and their tributaries in the study area

Fig

ure

3-3

Maj

or R

iver

s an

d th

eir

trib

utar

ies

in th

e st

udy

area

.


39

3.1.3. Geology

Geologically the piedmont zone which forms the northern part of the study area could be grouped into 5 morphostratigraphic units based on oxidation index, colour of sediments in the weathering zone and colour of the top soil (Das and Chattopadhyay, 1993). The morphostratigraphic units arranged in order of superposition can be seen in Table 7. In the piedmont zone, the two oldest formations the Samsing and the Matiali terminate either abruptly along piedmont scarp (Figure 3-4) or lobe out gradually into the south. These two formations were confined within the Himalayan arc. To the south of the piedmont zone in the study area, they were overlapped by Chalsa formation followed by Baikanthapur formation. The Chalsa formation was extensive near flanks of the Himalayan arc between the Jaldhaka and the Torsa River in the east and the Mahananda to the west. Between the Mahananda and the Jaldhaka, the Chalsa formation was overlapped by Baikanthapur formation which extended southward into Bangladesh. The Shaugaon formation was a recent fluvial terrace deposit which can be observed on the flanks of the rivers of the area. The materials of the younger fans contain reworked material of the older formation which were carried downstream and were deposited far away from the mountains and so range in size from cobbles to sand and clay. The coarse material of the piedmont zone graded into finer material of the flood plain.

G

EO

INF

OR

MA

TIC

S F

OR

INT

ER

BA

SIN

WA

TE

R T

RA

NS

FE

R A

SS

ES

SM

EN

T

40

F

igur

e 3-

4 Li

neam

ents

iden

tifie

d fr

om IR

S P

6 LI

SS

III d

ata

of 1

5th

Nov

200

5 an

d D

EM

gen

erat

ed fr

om S

RTM

dat

a (9

0 m

re

solu

tion)

sup

erim

pose

d on

geo

logy

of t

he s

tudy

ar

ea.

N


41

Table 7 Morphostratigraphic Units of West Bengal (GSI unpublished report).

The study area is influenced by tectonic activities prevalent from the Pliocene to the recent time, which took place in the eastern Himalayas (Haller, 1980). The northern part of the study area was characterized by alluvial fan deposit which coalesces to form the piedmont zone. The area was traversed by a number of transverse faults and faults parallel to the Himalayan arc. The evidence of faulting could be found in the piedmont scarp which were at a high angle and cut across a number of rivers which had a linear shift in their course at those sections. Similarly availability of younger formation (Chalsa Formation) north of older formation (Matiali formation) also indicated presence of scarp face and tectonic activity where the southern block was uplifted. The major faults and / or lineaments are indicated in Figure 3-4.

Quaternary Landform

Geology Colour of Top soil

Weathering Zone

Geological Age

Year BP

Shaugaon Formation

Allu

vial

Fan

Mat

eria

l

No soil cover Unoxidized Present day to Late Holocene

Erosional Unconformity

Baikunthapur Formation

Black soil cover

Unoxidized Late to Middle

Holocene

Chalsa Formation A

lluvi

al F

an

Mat

eria

l

Brown soil cover

Yellow coloured sediment

Early Holocene to

Late Pliestocene

Upliftment and Erosion

0.1

1 m

illio

n to

Pre

sen

t

Matiali Formation

Allu

vial

Fan

Mat

eria

l

Red soil cover

Orange coloured sediment

Early Holocene to

Late Pliestocene

Upliftment and Erosion

Samsing / Taljhora

Formation Allu

vial

Fan

Mat

eria

l

Chocolate soil cover

Red coloured sediment

Middle to Early

Pliestocene 1.8

mill

ion

– 0

.12

6 m

illio

n


42

3.1.4. Landuse / Landcover / Infrastructure

The study area could be subdivided into two physiographic division’s viz. the piedmont zone to the north and the alluvial plain to the south. The landuse and landcover of the study area (see Appendix A5) also reflected the terrain characteristics. The northern part was mainly covered by dense forest with occasional degraded forest and tea gardens in the hills and the fan lobe areas whereas the southern part was covered by agricultural activities varying from one seasonal crop to two crops a year with occasional scrub lands. There were very few large urban centres in the study area amongst which Jalpaiguri, Maynaguri and Alipurduar being the major ones. The rural settlements in the study area had a scattered arrangement and comprise of small concentrations. The tea was a major cash crop of this region and tea gardens were sometimes found to encroach forest reserves. The study area was the only connection between the main parts of India to the north eastern part and thus was strategically very important. The area was crisscrossed by national highway No.31 and national rail link.

3.2. Satellite Data, Maps and Ancillary Data used

Table 8 shows the various data used for the generation of the thematic maps for the multi criteria analysis. The maps were generated in 1:50000 scale with the projection system UTM Zone 45 and both datum and ellipsoid as WGS 84. Geological input was taken from Geological Survey of India (GSI) quadrangle map (1:250,000 scale) and other published literature of GSI. SRTM Version 3 data (http://srtm.csi.cgiar.org.) averaged to 90m resolution was used as source of elevation information and was available from internet resources as elevation data are restricted in India and Survey of India (SOI) elevation data was unavailable.


43

Table 8 Data used for generation of thematic maps.

3.3. Methodology

As part of scientific research a methodology has been formulated taking into account the problem, aim, objective, data available, technological knowhow and its implementation. Though locating a dam and fixing canal alignments can be done by various methods, it depends on drainage characteristics and varying terrain condition and appropriate technology for a particular environmental condition. Details of the work / approach to be undertaken are represented in the form of flow diagram in Figure 3-5. The methodology had been subdivided into 3 sections. The Stage - I deals with the terrain analysis for potential reservoir site location. Thematic maps were generated from available remote sensing data and a multi criteria analysis was undertaken using the thematic information for locating the potential reservoir sites. Stage – II dealt with reservoir volume / storage capacity estimation in a GIS framework where SRTM data was used as the input for an iterative numerical propagation method to find out spatial extent of reservoir and statistics related to reservoir capacity. The last and final section i.e. Stage - III of the methodology dealt with locating the preferable canal routes for transferring the water from the potential reservoirs with an ultimate

Name / Type

Source Purpose / Use Comments / Limitations /

Quality

LANDSAT TM

ITC Comparative study

30 m resolution, 1990

IRS 1D LISS III & IRS P6 LISS III satellite data

DST, Govt. of WB, India For preparation and updating of thematic layer

23.5 m resolution, for personal use only

SRTM Data (http://srtm.csi.cgiar.org.) DEM, Slope and Aspect Map

Averaged 90 m resolution global dataset

Geological Map

GSI Geology Map 1:10,00,000 scale


44

aim of joining the new canal to the already existing canal system between Teesta and Mahananda sub basin.

Figure 3-5 Overall research methodology.

3.3.1. Terrain Analysis and Reservoir Site Location

The methodology for locating potential reservoir sites takes into account both the physical suitability and the socio-economic suitability. Available IRS 1D LISS III, IRS P6 LISS III and LANDSAT TM data in association with SOI topo map and other ancillary data were processed using visual or digital classification technique to


45

generate pre field thematic maps pertaining to geomorphology, landuse / landcover and drainage of the area in 1:50,000 scale. The geology map was generated by scaling up available GSI geological map of 1:250,000 scale to 1:50,000 scale and updating it from available satellite data. The generated pre field thematic maps were then validated by ground truthing to generate the final geomorphology, geology, drainage and landuse / landcover map. These thematic maps were used for physical suitability for potential reservoir site selection and were used as input for multi criteria analysis. The transport network and the village map were derived from SOI topo map and updated from available satellite data. These were used as socio-economic suitability inputs for the multi criteria analysis. The detailed methodology is indicated in Figure 3-6. Two GIS based approaches can be undertaken for terrain analysis / multi criteria (TA / MCA) analysis for evaluation of spatial features and suitable locations of potential reservoirs (Malipa, 2005):

1. A subjective knowledge driven approach which emphasizes on expert knowledge in subject matter.

2. A data driven approach based on objective criteria and weighting. In the present case a data driven approach was followed as it gives adequate decision support information to make a judicious choice of the section of the river where the potential dam and the reservoir is to be located as given in Table 9.

Table 9 Key Criteria for dam site selection and the underlying condition considered for different thematic information used for MCA.

Thematic Layer Criteria for dam site selection Underlying condition

Settlement Not to be located near or within 1 Km settlement area

Safety (to avoid flooding)

Transport Network Not to be located within 1 km of major roads or railroad

Safety (to avoid flooding and disruption of communication)

DEM To be located above 110 m elevation

New canal alignment is to be connected to the existing Teesta – Mahananda linkcanal.


46

Table 9 Contd…………………

Thematic Layer Criteria for dam site selection Underlying condition

Slope To be located in a slope < 12% Hydraulic condition / Stability

Structure To be located at a distance > 500 m of an existing lineament /fault scarp

Stability

Drainage Preferably on river bed To have sufficient reservoir capacity

Geomorphology To be located avoiding low altitude fan / alluvial plain

Hydraulic condition / Stability

Landuse / Landcover

To be located avoiding agriculture land and tea garden

Resources / Environment

3.3.2. Reservoir Volume / Reservoir Capacity Estimation

On availability of the potential reservoir sites from Stage – I of the methodology a dam was created at each individual potential reservoir location taking into consideration dam height, free board and designed water level. In reality, inundation was likely to occur in the upstream portion of the river channel behind the dam where the area has an elevation less than the dam height. The dam marked at a particular location of the potential reservoir sites were converted into raster and then integrated with the available DEM data i.e. SRTM Version 3 (http://srtm.csi.cgiar.org.) data. The SRTM data was already pre-processed of the data voids and was a seamless elevation dataset of 5 by 5 degree tile. To determine the areal extent of the reservoir a neighbourhood connectivity function of ILWIS (ITC, 2001) was used which helps to find all neighbouring pixels connected in the DEM having an elevation lower than or equal to the specified water level of the reservoir behind the dam (Fazlur Rahman, 1992; Brouwer, 1994; Maathuis, Mannaerts et al., 1999). Using this technique the areal extent of the reservoir was mapped at the potential reservoir locations (Figure 3-7).


47

RS Data: Geocoded IRS P6 LISS III (2006)IRS 1D LISS III (2001)LANDSAT TM (1990)

SOI Toposheet (1:50000 scale)Ancillary Data

Visual Interpretation and / digital classification

Preparation of pre-field thematic maps in 1:50000 scale viz. geomorphology, geology, drainage, landuse

Ground Verification and / data collection

Preparation of Administrative and Transport Network

Updation

Final Geomorphology Map

Final Geology Map

Final Drainage Map

Final Land use / Land cover Map

Final Village Map

Final Transport Map

Multi criteria analysis

Terrain analysis & classification

Physical SuitabilitySocio-economic

Suitability

Potential sites of reservoirs

Figure 3-6 Methodology for terrain analysis and potential reservoir site location

Figure 3-7 Flooded area of reservoir detected using topography and connectivity operator (Fazlur Rahman, 1994).


48

Reservoir depth was calculated by subtracting the elevation values contained in the DEM from the respective reservoir water level. The reservoir volume or capacity was then determined by integrating the reservoir depth value of each pixel over the total inundated area. Based on the output of the neighbourhood function the preferred dam locations are selected. The detailed methodology is shown in Figure 3-8.

Figure 3-8 Methodology for reservoir map creation and volume calculation from DEM using iterative propagation method (Fazlur Rahman, 1992).


49

3.3.3. Criteria for Optimal Routing

After fixing the positions of the probable reservoir sites based on the dam height and reservoir storage capacity estimation, the possible canal alignment was decided on the basis of the gradient of the terrain for movement of water in direction of gravity. The ultimate aim was to join the proposed canal to the already existing Teesta - Mahananda link canal. Other important criteria that were taken into consideration were the fan lobes of the region for fixing canal alignment as cutting canals through the lobes would not always be feasible. Based on the storage capacity, a transfer rate was fixed from each reservoir based on the number of days a certain transfer rate could be maintained which should be sufficiently long to accommodate the dry season’s lower Q (discharge) in flow. A dimension of the proposed link canal was planned based on transfer rate from each reservoir to the main link canal. The calculation was carried out assuming normal flow depth in a rectangular channel by a reiteration process using the Secant’s method (Mannaerts, 1992).

3.4. Field Work

The field work was carried out with technical support from the Geoinformatics and Remote Sensing Cell, Department of Science & Technology, Govt. of West Bengal, India for a period of 5 weeks in September and October 2007 and was divided into three phases.

Phase – I Pre-field thematic maps of the area were generated with the help of multi temporal satellite imagery of IRS 1D LISS III, IRS P6 LISS III and LANDSAT TM data along with thematic maps and other ancillary data. The task involved preparation of pre-field geomorphology, drainage and landuse / landcover map and drainage map using visual or digital image classification technique. The associated database and classification scheme were fixed in line with the National Natural Resources Information Program of the Department of Space, Govt. of India. Check points were fixed for areas where the tone, texture and ancillary information was not sufficient enough to delineate geomorphological and landuse / landcover unit boundaries.

Phase – II This phase of the field work included site visits of the check points to corroborate the actual ground scenario for mapping the problematic units. Some site visits of the potential reservoir locations were also undertaken (see Figure 3-3). During the site visit it was observed that some of the potential reservoir sites included reserved forest or tea plantation areas in terms of landuse of the area though


50

geomorphologically it was mid altitude fan and topography wise a probable site for a reservoir. So during TA / MCA the landuse would have a lower weightage though the geomorphology or drainage of the area would have a higher weightage. In other locations though the topography seem to be best suited for a reservoir location but structurally it was on a fault surface and thus would have less weightage in TA / MCA. As the rivers in the study area were transboundary rivers so measured discharge data were restricted and unavailable. Some calculated (estimated) discharge data for the major rivers under consideration in the study area were available from government sources.

Phase – III The final phase included finalisation of the initial theme maps required for terrain analysis with technical support from Geoinformatics and Remote Sensing Cell, Department of Science & Technology, Govt. of West Bengal, India. The initial data generated during the field work are indicated in Table 10.

Table 10 Initial results during field work for ter rain analysis / multi criteria analysis.

3.5. Summary

The chapter gives an overview of the materials and methods used for the research. A description about the various terrain characteristics of the study area was given. The images used for the initial mapping purpose were also indicated. The section describes the methodologies of terrain analysis and reservoir characterization and capacity estimation. The field work approach was also discussed.

Thematic maps

Source Purpose /

Use

Comments / Limitations /

Quality

Drainage

Geomorphology

Geology

Landuse / Landcover

Transport Network

Administrative

IRS P6 LISS III 15 Nov, 2005 IRS 1D LISS III 20 Feb 2000 LANDSAT TM 14 Nov and 21 Nov 1991, SOI Topo Map, GSI Geology Map, Village Map

Multi – criteria analysis / Terrain analysis for potential reservoir site selection

1:50000 scale [Database generated as part of an internal project of Deptt. of Science & Technology, Govt. of West Bengal, India]


51

4. Results and Discussions

4.1. Results of Post Field Analysis

The post field phase included the finalisation of the thematic maps (see also Table 10) generated from the satellite data and other available ancillary data. The data was then used as an input along with elevation information from SRTM Version 3 dataset for the terrain analysis / multi criteria analysis to find out suitable locations for the dams in the study area (see Section 4.1.1). The potential reservoir sites were then tested with the neighbourhood classification technique to delineate the extent of the reservoir and determine the reservoir volume or reservoir capacity (see Section 4.1.2). This phase also included finalisation of the reservoir sites and demarcating the optimal route of the link canal (see section 4.1.3). An assessment of the IBWT is also undertaken in this chapter. It includes possible usage of the water available at a given transfer rate. It also deals with scenarios of loss of reservoir capacity and loss of water during conveyance / evaporation (see section 4.2). The final part of this section deals with the limitations of the methodology used for the above analysis and the effects on the results (see section 4.3).

4.1.1. Terrain Analysis / Multi Criteria Analysis Results

The terrain analysis and the multi criteria analysis were undertaken considering two factors, the physical suitability and the socio-economic suitability. The inputs for the physical suitability included the landuse map, the geomorphology map, the geology map, the structural map, the slope map and the DEM. The socio-economic suitability inputs included the settlement map and the transport network map. The MCA involved raster analysis in which all the input maps were converted into raster. Weightage was given to each individual geomorphic unit ranging from 0 to alluvial plain and 3 to mid altitude intermediate fan in a scale of 0-4 for the 5 major geomorphic unit. Similarly, out of the 15 landuse classes 5 major classes were considered which is likely to be affected by the reservoir, where agricultural land has a weightage of 0 while river bed has a weightage of 5 in a scale of 0-5. BOOLEAN operation was operated on elevation and slope information where the condition given was; all the reservoirs are to be located above 110 m contour and a slope of 0-12%. A set of maps were then generated by crossing the above raster maps using BOOLEAN operation where the pixel values which conformed to the criteria (see Table 9) were given a value of 1 (suitable) and the pixel values which did not meet


52

the criteria where given a value of 0 (unsuitable) to find the physically suitable location for dams. Similarly, to find the socio-economic suitability a distance buffer was created around the road and the settlement locations (as per Table 9). The areas within the buffer were considered as 0 (unsuitable) and those outside the buffer were considered as 1 (suitable). The outcome was presented in the form of Composite Suitability map as depicted in Figure 4-1 prepared. The next step was to locate the potential dam and reservoir location using both the suitability map and the hydrological character of the study area which was shown in Figure 4-2.

As seen in Figure 4-1and Figure 4-2, one of the five sites was not suitable based on the multi – criteria analysis (Dam 3), but a dam was proposed and reservoir volume estimation was undertaken. As the multi criteria analysis included the landuse theme and on either side of the river the main landuse category was forest, so the site was unsuitable based on the weightage of the forest class. But if we look only at the slope and the drainage character, the site was suitable and so the site was chosen for reservoir capacity estimation in the first scenario. Similarly the Dam A, though was suitable according to the multi-criteria analysis, does not give enough reservoir capacity when the estimation was undertaken by the iterative propagation method. In the second and third scenario (Figure 4-3) the reservoir locations were based only on elevation data as the locations were outside the planned study area and due to time constrain no thematic information could be generated. Thus the methodology followed agreed with the alternate hypothesis that only elevation data can be used for reservoir characterization but for TA / MCA both thematic information as well as elevation information is required for reservoir characterization.


53

Figure 4-1Composite Suitability Map of Potential Reservoir Sites generated using Multi criteria

Fig

ure

4-1

Com

posi

te s

uita

bilit

y m

ap o

f pot

entia

l rese

rvoi

r si

tes

gene

rate

d us

ing

mul

ti cr

iteria

ana

lysis

.


54

Figure 4-2Location of reservoirs (Scenario 1) based on multi criteria analysis

and hydrological character of the drainage of the area

Fig

ure

4-2

Loca

tion

of r

eser

voirs

(S

cena

rio 1

) ba

sed o

n m

ulti

crite

ria a

naly

sis

and

hydr

olog

ical

ch

arac

ter

of th

e dr

aina

ge o

f the

are

a.

G

EO

INF

OR

MA

TIC

S F

OR

INT

ER

BA

SIN

WA

TE

R T

RA

NS

FE

R A

SS

ES

SM

EN

T

55

Fig

ure

4-3

Loca

tion

of r

eser

voirs

(S

cena

rio 2

and

3) ba

sed

on e

leva

tion

info

rmat

ion

of th

e ar

ea fr

om SR

TM

(90

m r

esol

utio

n)

data

.

N


56

4.1.2. Reservoir Volume / Capacity Estimation Based on Iterative Numerical Propagation Method

The TA /MCA were used to locate the potential reservoir sites in the study area. A total of five sites were found. The existing barrage on the river Teesta was considered as a potential location to determine reservoir capacity and to test the iterative propagation method and was visualized with the existing reservoir as can be seen in the IRS P6 LISS III multispectral data. Besides the river Teesta potential reservoir locations were also found on the tributary of the river Jaldhaka, the river Murti, the river Torsa and the river Kaljani. At each of these locations the iterative propagation method was applied based on a neighbourhood function of ILWIS (ITC, 2001). The neighbourhood function helps to find the topographically connected areas in conjunction with a connectivity operator. A cell was marked behind the dam and an algorithm looked for all neighbouring cells of the marked cell with an elevation lower or equal to the specified reservoir water level. The cells that satisfy the above condition were marked. The process again started comparing the neighbouring cells of the newly marked cells with the reservoir level and selected the connected cells with equal or lower elevation to the reservoir level. This iterative process continued till no more connected cells having elevation less or equal to the level used were marked as flooded. A numerical example of the iteration with propagation is shown in Figure 4-4. The reservoir extent and reservoir capacity were determined for three different levels of the dam and three reservoir extent maps were created for each of the potential reservoir site in the given time constraint. The catchment area of the rivers or the tributaries from the dam locations were determined from the drainage map generated from the DEM (Figure 4-5) as the available drainage data of the study area formed only a part of the total catchment from the dam location. Use was made of the DEM hydroparameterization module of ILWIS (ITC, 2001). At catchment outlet the dam location was used during the catchment merge operation to obtain the catchment area upstream of the dam. Figure 4-6 shows the reservoir extent at different dam levels on the river Teesta. In Figure 4-7, Figure 4-8, Figure 4-9, Figure 4-10 and Figure 4-11 the calculated volumes of the reservoir at different ground elevation or DEM interval on the river Teesta, the tributary of river Jaldhaka, the river Murti and the river Kaljani were plotted. A near linear relationship was found between the dam height and the reservoir capacity and therefore no intermediate levels were calculated (see R2 in the Figures 4-7 to 4-11). Thus with increasing dam height there


57

was increase in reservoir volume / reservoir capacity as shown by the regression equations in the figures indicated above.

Figure 4-4 Numerical example of iterative propagation process to determine reservoir extent. Reservoir level is assumed to be 50 (Fazlur Rahman, 1994).


58

Figure 4-5 Drainage map and catchment boundaries of rivers of the study area derived from SRTM Version 3 data of 90 m resolution (http://srtm.csi.cgiar.org.) using ILWIS 3.3 (ITC, 2001)

Fig

ure

4-5

Dra

inag

e m

ap a

nd c

atch

men

t bou

ndar

ies

of riv

ers

of th

e st

udy

area

der

ived

from

SR

TM

Ver

. 3 da

tase

t of 9

0 m

re

solu

tion

(http

://sr

tm.c

si.c

giar

.org

.) u

sing

ILW

IS 3

.3 (

ITC

, 200

1).


59

Figure 4-6 Areal extent of reservoir for different dam heights on R. Teesta superimposed on IRS P6 LISS III data.

Dam 1 - R. Teesta

y = 76.903x - 831.46

R2 = 0.9324

0100200300400500600700800900

1000

12 14 16 18 20 22 24

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

.m.)

Figure 4-7 Reservoir storage capacity curve for different dam heights on R. Teesta as derived from digital elevation model.

Volume Linear Volume


60

Dam 2 - R. Jaldhaka Tributary

y = 1.1728x - 12.819

R2 = 0.94770

5

10

15

20

25

10 12 14 16 18 20 22 24 26 28

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

.m.)

Figure 4-8 Reservoir storage capacity curve for different dam heights on Jaldhaka tributary as derived from digital elevation model.

Dam 3 - R. Murti

y = 3.5822x - 40.428

R2 = 0.9573

0

5

10

15

20

25

12 14 16 18

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu .m

.)

Figure 4-9 Reservoir storage capacity curve for different dam heights on R. Murti as derived from digital elevation model.




61

Dam 4 - R. Torsa

y = 0.5849x - 5.1638

R2 = 0.9999

y = 0.5849x - 5.1638

R2 = 0.99990

1

2

3

4

8 9 10 11 12 13 14 15 16

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

.m.)

Figure 4-10 Reservoir storage capacity curve for different dam heights on R. Torsa as derived from digital elevation model.

Dam 5 - R. Kaljani

y = 1.3082x - 10.645

R2 = 0.980

1

2

3

4

5

6

7

8 9 10 11 12 13 14

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

.m.)

Figure 4-11 Reservoir storage capacity curve for different dam heights on R. Kaljani as derived from digital elevation model.

Similar reservoir extent maps were also generated for three different dam heights at the other four potential locations (Appendix B1 – B4). The runoff was assumed to be 50 % of the mean annual precipitation. The mean annual precipitation was considered the same for all the catchments and was equal to the mean of the mean annual precipitation of four stations (Appendix A1 – A4) in the study area which was 3517 mm. The mean, median and standard deviation of the recorded yearly rainfall at the four measuring stations in the study area is given in Table 11. The present Teesta barrage in the area has a transfer rate of about 30 m3 / (available from




62

inscription on stone tablet beside the canal during field work), which amounts to around 946 million m3 annually. Total runoff available (considering 50% of mean annual precipitation of the study area as runoff) was about 15360 million m3. Thus total volume being transferred was about 6% of the total runoff. Table 12 indicates the volume of water available through runoff, the maximum storage capacity and percentage of runoff being utilized for storage in each of the five reservoirs in the first scenario. Assuming 20 m3 / sec of water transfer from the rest of the 4 reservoirs in Scenario 1 (transfer rate of Teesta being taken as 30 m3 / sec) the daily water available for transfer was about 50 m3 /sec and it was found that there would be water supply for only 225 days with the total available reservoir capacity of 972 million m3. An assessment of water availability from each of the four proposed reservoirs was carried out and can be seen from Table 14. If 5 m3 / sec of water was taken out from the other 4 reservoirs to meet the total 50 m3 / sec transfer rate, they might not have enough storage capacity. Considering IBWT, where a continuous supply of water was required to meet requirement in various sectors such as irrigation, power and human consumption with an assumed transfer rate of 50 m3 /sec, two more scenarios were tested. In Scenario 2, two of the existing reservoirs on tributary of the river Jaldhaka and on the river Torsa were relocated upstream at the boundary of the study area and one of the reservoirs on the river Kaljani was discarded. Similar reservoir extent maps and storage capacity curves (Appendix B5 – B8) were also generated for the two new dams with different dam heights.

Table 11 Mean, median and standard deviation of rainfall data at four recording stations of the study area.

Rain Gauge Station

Minimum Rainfall

Maximum Rainfall

Mean Annual Rainfall

Median STDEV

Jalpaiguri 2278.00 5148.00 3534.94 3415.00 696.92

Alipurduar 2508.20 5016.80 3751.37 3655.80 836.85

Hasimara 1859.51 4859.30 3358.75 3391.75 896.82

Banarhat 2512.10 4826.60 3421.69 3302.38 689.48

Table 13 indicates volume of water available through runoff, the maximum storage

capacity and percentage of runoff being utilized for storage in each of the four reservoirs in the second scenario. All the assumptions were same as considered in Scenario 1. In this case it was found that with an assumed water transfer of 50 m3 / sec, the stored water would be able to supply water for a maximum of 276 days. An


63

assessment of water availability from each of the four proposed reservoirs was carried out as can be seen from Table 15. A Scenario 3 was then tested where two more reservoirs were decided upon at two new locations on the river Raidak and the river Sankosh. Both the rivers flow through the study area, but within the study area no suitable reservoir site was found during TA / MCA. The new reservoirs were located on these two rivers further upstream but outside the study area. Besides being outside the study area, the reservoir extended over the international boundary. In this case it was found that with an assumed transfer rate of 50 m3 / sec the stored water would be able to supply water for a maximum of 345 days which comes almost to an annual availability. Appendix B9 – B12 shows the reservoir extent at different dam levels on the river Raidak and the river Sankosh and the storage capacity curves generated at these two locations. Table 16 indicates volume of water available through runoff, the maximum storage capacity and percentage of runoff being utilized for storage in Scenario 3 when 6 reservoirs were constructed. The assessment of water availability from each of the six proposed reservoirs can be seen in Table 17. The transfer rate of each of the six reservoirs indicated that the reservoirs behind Dam 1 on the river Teesta could supply water for alomost a year with the present transfer rate of Teesta canal, while Dam 4 and Dam 6 could supply water at a transfer rate of more than 5 m3 / sec. Dam 5 could supply water on a continuous basis if the transfer rate was considered as 3m3 / sec, while Dam 2 and Dam 3 could supply water almost round the year with a combined transfer rate of 5 m3 / sec. It was found that in all the scenarios the percentage of runoff being stored for transfer from each reservoir does not exceed more than 8 % of the total available water from runoff which was about 2% more than the actual scenario (6 % of runoff being transferred from present Teesta reservoir @ a transfer rate of 30 m3 / sec). This indicated that the natural flow of the river downstream would not be hampered to a huge extent. Only exception in this case was the reservoir behind Dam 2 on the tributary of the river Jadhaka, which was about 22.5%. In this case as the reservoir and the dam were located in one of the several tributaries of the main river Jaldhaka, the water available downstream in the main river would not be affected to a great extent as the other tributaries would be feeding the main river. The above results indicated that storage capacity and reservoir extent could be determined from DEM using an iterative propagation method in ILWIS (ITC, 2001). Moreover, the DEM used for reservoir characterization was generated from SRTM Version 3 data (http://srtm.csi.cgiar.org.), and thus it could be said that SRTM data is effective for a preliminary reservoir site characterization.

G

EO

INF

OR

MA

TIC

S F

OR

INT

ER

BA

SIN

WA

TE

R T

RA

NS

FE

R A

SS

ES

SM

EN

T

64

Tab

le 1

2 W

ater

ava

ilabi

lity

in 1

st S

cena

rio.

Dam

N

o.

Riv

er

Sub

-bas

in

Cat

chm

ent A

rea

from

Dam

(m

2 )

Mea

n A

nnua

l P

reci

pita

tion

(mm

)

Run

off*

(m

m)

vol./

area

(m

3 /m2 )

Vol

ume

of w

ater

av

aila

ble

thro

ugh

runo

ff (m

3 )

max

sto

rage

(m

3 ) %

of

runo

ff

1

Tee

sta

Tee

sta

87

3441

0219

1

535

9460

369

9

201

9240

0

5.9

9

2

Jald

hak

a T

ribu

tary

7

488

2880

0

13

1681

5444

2

043

6300

1

.55

3

Mu

rti

Jald

hak

a 1

527

9840

0

26

8695

986

2

134

3500

7

.94

4

To

rsa

3

897

0841

52

68

5302

2481

3

604

500

0

.05

5

Kal

jan

i T

ors

a 9

727

1888

35

17.0

0

17

58.5

0

1.7

6

17

1052

614

6

577

200

3

.85

To

tal R

eser

voir

Cap

acity

in m3

9721

5390

0

To

tal w

ater

req

uire

men

t /

day

@ 5

0 m3

4320

000

Ava

ilab

ility

(in

day

s)

225

* A

ssum

ed r

unof

f as

50%

of

mea

n an

nual

pre

cipi

tation

G

EO

INF

OR

MA

TIC

S F

OR

INT

ER

BA

SIN

WA

TE

R T

RA

NS

FE

R A

SS

ES

SM

EN

T

65

Tab

le 1

3 W

ater

ava

ilabi

lity

in 2

nd S

cena

rio.

Dam

N

o.

Riv

er

Sub

-bas

in

Cat

chm

ent A

rea

from

Dam

(m

2 )

Mea

n A

nnua

l P

reci

pita

tion

(mm

)

Run

off*

(m

m)

vol./

area

(m

3 /m2 )

Vol

ume

of w

ater

av

aila

ble

thro

ugh

runo

ff (m

3 )

max

sto

rage

(m

3 ) %

of

runo

ff

1

Tee

sta

Tee

sta

87

3441

0219

1

535

9460

370

9

201

9240

0

5.9

9

2

Jald

hak

a T

ribu

tary

(U

pst

rea

m

new

lo

catio

n)

12

7761

300

2

246

6824

6

51

0624

00

22

.73

3

Mu

rti

Jald

hak

a

15

2798

400

2

686

9599

0

21

3435

00

7.9

4

4

To

rsa

(Up

stre

am

n

ew

loca

tion

)

To

rsa

37

6178

5802

35

17.0

0

17

58.5

0

1.7

6

66

1510

0332

1

955

6640

0

2.9

6

To

tal R

eser

voir

Cap

acity

in m3

1188

1647

00

To

tal w

ater

req

uire

men

t /

day

@ 5

0 m3

4320

000

Ava

ilab

ility

(in

day

s)

275

* A

ssum

ed r

unof

f as

50%

of

mea

n an

nual

pre

cipi

tation


66

Table 14 Water availability from each reservoir in 1st Scenario considering different transfer rates.

Dam No. River Q out per day (m3/s)

No. of days

1 Teesta 30 355

2 Jaldhaka Tributary 2 118

3 79 5 47 3 Murti 2 124 3 82 5 49 4 Torsa 2 21 3 14 5 8 5 Kaljani 2 38 3 25 5 15

Table 15 Water availability from each reservoir in 2nd Scenario considering different transfer rates.

Dam No. River Q out per day (m3/s) No. of days

1 Teesta 30 355 2 Jaldhaka Tributary

(Upstream new location)

2 296

3 197 5 118 3 Murti 2 124 3 82 5 49 4 Torsa (Upstream new

location) 5 453

G

EO

INF

OR

MA

TIC

S F

OR

INT

ER

BA

SIN

WA

TE

R T

RA

NS

FE

R A

SS

ES

SM

EN

T

67

Tab

le 1

6 W

ater

ava

ilabi

lity

in 3

rd S

cena

rio.

Dam

No.

R

iver

S

ub-b

asin

C

atch

men

t Are

a fr

om D

am (

m2 )

Mea

n A

nnua

l P

reci

pita

tion

(mm

)

Run

off*

(m

m)

Vol

/are

a (m

3 /m2 )

Vol

ume

of w

ater

av

aila

ble

thro

ugh

runo

ff (m

3 )

max

sto

rage

(m

3 ) %

of

runo

ff

1

Tee

sta

Tee

sta

87

3441

0219

1

535

9460

369

9

201

9240

0

5.9

9

2

Jald

hak

a T

ribu

tary

(U

pst

rea

m n

ew

loca

tion

)

12

7761

300

2

246

6824

6

51

0624

00

22

.73

3

Mu

rti

Jald

hak

a

15

2798

400

2

686

9598

6

21

3435

00

7.9

4

4

To

rsa

(Up

stre

am

new

lo

catio

n)

To

rsa

37

6178

5802

6

615

1003

32

19

5566

400

2

.96

5

Rai

dak

(O

uts

ide

area

) R

aid

ak

45

9031

4546

8

072

0681

28

10

7786

700

1

.34

6

San

kosh

(O

uts

ide

area

) S

anko

sh

95

9817

2980

35

17.0

0

17

58.5

0

1.7

6

16

8783

8718

4

19

2496

500

1

.14

Tot

al R

eser

voir

Cap

acity

in m

3

14

8844

7900

Tot

al w

ater

req

uire

men

t / d

ay @

50

m3

4320

000

Ava

ilabi

lity

(in d

ays)

34

5

* A

ssum

ed r

unof

f as

50%

of

mea

n an

nual

pre

cipi

tation


68

Table 17 Water availability from each reservoir in 3rd Scenario considering different transfer rates.

Dam No. River Q out per day (m3/s)

No. of days

1 Teesta 30 355 2 Jaldhaka Tributary

(Upstream new location)

2 296

3 197 5 118 3 Murti 2 124 3 82 5 49 4 Torsa (Upstream

new location) 5 453

5 Raidak (Outside area)

3 416

5 250 6 Sankosh (Outside

area) 5 446

4.1.3. Optimal Route Selection of Link Canal

The route selection of the proposed link canal had an ultimate aim of merging with the existing Teesta – Mahananda Link Canal. Based on this aim an optimal route was found taking into consideration slope, roughness and the terrain character especially the mid altitude intermediate fan which was avoided as far as possible. Though landuse of the area should be a consideration especially the forest areas, the tea gardens and the agricultural land while fixing the link, but the location of the reservoirs did not give an alternate option of avoiding the above landuse categories (Fig 4-13). As the total transfer rate was assumed to be 50 m3 / sec and the existing TMLC had a carrying capacity of about 30 m3 / sec; the rest of the reservoirs would contribute about 20 m3 / sec. Keeping this into consideration a transfer rate of 6 m3 / sec was considered for the first section with input from the river Sankosh to the proposed link canal, a 4 m3 / sec additional transfer rate was added to the second section from the river Raidak while a 5 m3 / sec transfer rate was added to each of the third and fourth section of the canal from the river Torsa and a combined transfer from the river Murti and the tributary of the river Jaldhaka respectively. The section five of the canal had a transfer rate of 50 m3 / sec with an input of 30 m3 / sec from


69

the river Teesta. A schematic diagram of the link canal and the transfer from each reservoir on the rivers of the study area are given in Figure 4-12. Based on the transfer rate from each reservoir a canal dimensioning was undertaken using a reiterative process by calculating normal flow depth in a rectangular channel using Secant’s method (Mannaerts, 1992). The estimated dimension of the proposed link canal is given in Table 18. An average flow velocity of 1 m3 / sec was maintained in the proposed link canal.

Figure 4-12 Estimated dimensions of the proposed link canal

Table 18 Estimated dimensions of the proposed link canal using reiterative method (Mannaerts, 1992).

Canal Sections Section 1 Section 2 Section 3 Section 4 Section 5

Factors Transfer Rate (m3/s) 6 10 15 20 50

Manning Roughness (n) 0.04 0.04 0.04 0.04 0.04

Slope m/m 0.002 0.0017 0.00125 0.001 0.00055

Width of Canal m 3 4 5 6 9

Flow depth m 1.99 2.31 2.81 3.16 5.25

Flow Velocity m/s 1.01 1.08 1.07 1.05 1.06

G

EO

INF

OR

MA

TIC

S F

OR

INT

ER

BA

SIN

WA

TE

R T

RA

NS

FE

R A

SS

ES

SM

EN

T

70

F

igur

e 4-

13 M

ap s

how

ing

the

prop

osed

can

al r

oute

supe

rimpo

sed

on la

ndus

e / l

andc

over

.


71

4.2. Assessment of IBWT

An assessment of the utilization of the water available in the above 3 scenarios were undertaken. The assumptions behind this assessment were as follows:

1. 2 mm depth of water per day was required for irrigation purpose based on a requirement of 2 cm in a 10 day cycle.

2. 70 - 135 litres of water was required by each person every day varying from rural to urban areas respectively (http://mahawssd.gov.in).

The assessment also considered loss of water due to evaporation and during conveyance which was assumed to be a total of 10%, though in reality the loss would vary with changing seasons, climatic conditions and aging of the canal. Four scenarios of reduction of reservoir capacity were considered varying from 10 % to 40% over a period of time as we have seen in earlier studies and available literature (Das and Chattopadhyay, 1993; Dasgupta, 1993) that the rivers of the study area carry a lot of sediments. As the reservoirs were located in the piedmont zone so a lot of siltation was expected resulting in reduction of reservoir capacity over time. Figure 4-14 shows the usage of the available water only for irrigation after considering full utilization without any loss and also utilization considering reduction of reservoir capacity as well as loss due to evaporation and conveyance. Figure 4-15 and Figure 4-16 shows the usage of 40% of the available water for irrigation and 20% of the available water for human consumption respectively. It was assumed that 2 mm/day water was required for irrigation given a 2 cm requirement in a 10 day cycle and 70 litres/day water utilization for rural population and 135 litres/day for urban population (http://mahawssd.gov.in) as it was unlikely that in reality water stored and transferred in an IBWT project would be used solely for one of the above purposes. The results indicated that if water was available at a discharge rate of 50 m3 /sec then a total of 4.32 million m3 water would be available daily. If 40 % of the available water was used for irrigation a total of 2160 km2 area would be served daily and if 20% of it was used for human consumption, then utilizing 70 litres per day, 12.34 million people would be served and if 135 litres per day requirement is considered 6.4 million people would be served.


72

10

0%

10

0%

10

0%

10

% +

10

%

10

% +

10

%

10

% +

10

%

20

% +

10

%

20

% +

10

%

20

% +

10

%

30

% +

10

%

30

% +

10

%

30

% +

10

%

40

% +

10

%

40

% +

10

%

40

% +

10

%

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

1 2 3

Scenarios

Irrig

ated

Are

a (m

illio

n sq

. km

.)

Figure 4-14 Estimated irrigated area if the water was used only for irrigation in 3 scenarios considering full capacity and subsequent reduction of reservoir capacity (10% , 20%, 30% and 40%) due to siltation and 10 % loss due to evaporation and conveyance together. The first bar (solid black) indicates the irrigated area without considering any loss in all the 3 scenarios.

10

% +

10

%

10

% +

10

%

10

% +

10

%

20

% +

10

%

20

% +

10

%

20

% +

10

%

30

% +

10

%

30

% +

10

%

30

% +

10

%

40

% +

10

%

40

% +

10

%

40

% +

10

%

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1 2 3

Scenarios

Irrig

ated

Are

a (m

illio

n s

q. k

m.)

Figure 4-15 Estimated irrigated area in 3 scenarios considering reduction of reservoir capacity (10% , 20%, 30% and 40%) due to siltation and 10 % loss due to evaporation and conveyance together using 40% of the available water for the purpose of irrigation.


73

10

% +

10

%

10

% +

10

%

10

% +

10

%

20

% +

10

%

20

% +

10

% 20

% +

10

%

30

% +

10

%

30

% +

10

%

40

% +

10

%

40

% +

10

%

40

% +

10

%

30

% +

10

%

0

50

100

150

200

250

300

1 2 3Scenarios

No.

of D

ays

of W

ater

Ava

lab

ility

Figure 4-16 Estimated number of days the water will last for a rural population of 12.34 million with a consumption of 70 litres / day or an urban population of 6.4 million with a consumption of 135 litres/day in 3 scenarios considering reduction of reservoir capacity (10%, 20%, 30% and 40%) due to siltation and 10 % loss due to evaporation and conveyance together.

The results also showed a decreased availability in each scenario due to reduction in reservoir capacity and loss during transportation and due to evaporation. Though the water in a real world scenario would be used for many other purposes beside irrigation and human consumption such as power generation and industrial use, a preliminary assessment was undertaken only for the major purposes mentioned above (See Appendix C).

4.3. Limitations of the Methodology

No methodology could be free of limitations. This was because all factors that operate in a natural system cannot be taken into consideration using a single methodology. The present methodology used to undertake the assessment of the inter basin water transfer had the following main limitations amongst others:

1. The TA / MCA considered only some of the factors required for site selection such as slope, drainage network, geomorphology, geology, structure and landuse for physical suitability and village locations and transport network for socio-economic suitability. But in reality other factors like drainage category, drainage discharge, soil type, soil character were


74

required in the multi-criteria assessment. Weightage needed to be assigned to each of the categories in individual factors to get a more realistic result for site selection of reservoirs.

2. The SRTM data used as an input for elevation information was averaged to

90 m resolution and was a global dataset. This type of data set is very useful when undertaking a preliminary assessment for reservoir characterization using the iterative propagation method in a regional scale. But if we consider the individual potential reservoir locations then elevation information of much high resolution needed to be procured to undertake a better assessment of reservoir capacity. Thus SRTM data having low resolution may under determine slope steepness (Wu, Li et al., 2007) of adjacent cell thus resulting in over or under estimation of reservoir capacity. The present methodology did not consider the uncertainties related to elevation information and the effect of radar reflective surface.

3. The alignment of the link canal did not consider the slope factor as well as

the terrain condition in detail. The proposed alternatives were the representation of a methodology with limited ground data.

4. The assessment of the utilization of the water available was based on

certain assumptions of water transfer. The reservoir capacity determined by the iterative propagation method had limitations in itself as mentioned earlier. Thus the actual availability in the study area could not be determined. Moreover, the transfer volume was also assumed and utilization was considered only for irrigation and human consumption. But in reality there were other utilization purposes of the water and thus a detailed assessment could not be undertaken. But the methodology was a preliminary representation of how the assessment should be carried out if actual needs are available.

4.4. Summary

Thus the results or outputs of the applied methodologies based on the available data and the analysis undertaken indicated that the above methodologies could be used very effectively for a preliminary site selection of potential reservoirs, delineation of reservoir extent, estimation of reservoir capacity and assessment of the utilization of the available water. The thematic layer generated using multi spectral and multi temporal satellite data in 1:50,000 scale were very effective in site selection though


75

more information related to river width, river discharge, soil type and character were required for a more realistic spatial multi criteria analysis. The results also indicated that SRTM data of 90 m resolution was very useful dataset for slope estimation as well as characterization of the reservoir. A preliminary assessment of the canal routing could also be undertaken using the thematic and elevation information. But limited availability of river related data as well as limited scope and uncertainties of coarse resolution elevation data brings in an inherent limitation to the methodologies undertaken and the resulting outputs.


76

5. Conclusions and Recommendations

Inter basin water transfer is being considered a dominant solution to cope with the deficit of water in some major river basins of the world. The ILR project is one such plan which is under consideration. This thesis developed an approach to undertake a preliminary assessment of such a water transfer using geoinformatics as a tool. TA / MCA are considered as the method to identify potential reservoir location. SRTM data is used as an input for elevation information to determine reservoir capacity. An optimal route of the canal is also proposed along with an estimated canal dimension and benefits of the transferred water volume are also determined. Based on the research questions the following specific conclusions are summarised below:

5.1. Specific Conclusions

1. The relevant geomorphological, geological, landuse and drainage characteristics for IBWT in the study area.

Multispectral satellite data can be used to map the relevant geomorphology as well as geology, landuse and drainage of the study area to be used as input for TA / MCA to locate potential reservoir sites. The above thematic information cannot be used independently for reservoir site selection. Elevation and slope data in association with the above thematic information is best suited for locating potential reservoir sites. Thus the relevant terrain units from the above thematic maps and elevation information is significant for locating potential reservoir sites and undertaking IBWT in the study area. This corroborates similar studies being undertaken for reservoir site selection or check dam location, though the source of elevation information was from sources other than SRTM data (Malipa, 2005). But the present research could be used as a preliminary effort for undertaking TA / MCA in a large river basins. More data needs to be collected and more thematic information is required to generate more precise potential reservoir site locations.


77

2. Calculation of storage capacity of reservoir using iterative propagation method and reservoir site characterization using SRTM data.

The research used SRTM Version 3 data (http://srtm.csi.cgiar.org.) as an input for reservoir characterization and capacity estimation. For a given dam height, water level and free board it is possible to determine reservoir extent and reservoir volume. An iteration function of ILWIS (ITC, 2001) can be used very effectively for this purpose. A map is created indicating one pixel in the future reservoir area. Using neighbourhood function the pixel acts as the starting point for the calculation. Iteration with propagation is used until no changes in pixel value are observed which enables to find the reservoir area. Volume can then be calculated by crossing the flooded map with elevation map having the dam height information. This process can be repeated for different dam heights to find the maximum storage capacity for a particular dam location. Thus this method is effective along with input from SRTM Version 3 data (http://srtm.csi.cgiar.org.) for reservoir characterization. This iteration with propagation has been used in studies related to flood inundation modelling due to dyke failure (Fazlur Rahman, 1992) and storm water surges in urban areas (Maathuis, Mannaerts et al., 1999). The present study has used the same methodology but instead of estimating the extent of flood inundation due to dyke failure or storm water surge it estimates the reservoir extent on the upstream side of dam modelled on a river channel and the volume of water that can be stored. Though the studies by Rahman and Maathuis used elevation information from contour maps and spot heights respectively and used an interpolation algorithm to generate a DEM of the area, the present research uses SRTM Version 3 data (http://srtm.csi.cgiar.org.) as source of elevation information because the area covered is a large river basin and high resolution elevation data for such a big area is unavailable. The data is a averaged 90 m global dataset and the voids has been filled by interpolative technique in TOPOGRID algorithm of Arc/Info which is based on established algorithms of Hutchinson (1988; 1989), which use contour data (and stream and point data if available) to produce hydrologically sound DEM (http://srtm.csi.cgiar.org). Thus it can be said that SRTM data is effective in undertaking reservoir characterization and volume calculation. More research using field data collected by GPS survey or other local


78

elevation information of much higher resolution is required for better characterization of the potential reservoir sites.

3. Optimal canal routing and dimensioning

The optimal route of the canal to link those reservoirs can also be determined by taking into account the elevation, slope and the terrain character including geomorphology and landuse of the study area. The optimal canal route is a representation of the possible route decided based only on the above criteria. But a more detailed study is needed for optimal routing of the link canal as well as proper dimensioning of the canal. Detailed topographic information is required as the channel slope of the proposed canal should not be more than 1 m to 2 m / km. The reiterative process used (Mannaerts, 1992) indicates that to maintain a flow velocity of about 1 m3 / sec, the channel slope should not exceed 2 m / kilometre. This can be corroborated with the available transfer rate and flow depth of the existing TMLC in the study area with an assumed Manning roughness (n) of 0.04 though it is higher than Manning roughness of an open channel with gravel bottom and concrete sides (0.033) or an open channel of only concrete (0.12) (Chow, Maidment et al., 1988).

4. Assessment of the utilization of the available water.

In this research, assessment has been carried out for utilization of the available water for irrigation and human consumption taking into consideration loss due to evaporation, conveyance and reduction in reservoir capacity. It can be concluded that these type of assessment enables to estimate water utilization in different scenarios of water availability which are prevalent in a real world. Moreover, the assessment is undertaken in the background of inter basin water transfer; it is very much relevant to have an idea about the possible usage of water in such water transfer programs. These water transfer programs are implemented to compensate water deficit in the areas of irrigation, human and industrial consumption besides other possible uses such as hydro power generation and navigation.

5.2. Limitations of Research

1. Multi criteria analysis requires more input information for a better weightage allocation to have a more precise site selection. The present research has a restricted supply of database related to hydrological characteristics of the rivers of the study area. The rivers are transboundary


79

rivers and as a result data is unavailable to the author. Thus the multi criteria analysis output may not precisely locate the potential reservoir sites. Some reservoir characterization is undertaken outside the study area in the third scenario for availability of water throughout the year. In these cases no thematic information is available. The reservoirs are located using only elevation information.

2. For reservoir characterization SRTM Version 3 data of resolution 3 arc

second i.e. 90m by 90m (http://srtm.csi.cgiar.org.) is used which is more precise than other global datasets such as GTOPO30 of 30 arc second resolution i.e. 1km by 1 km and may well suit for a preliminary reservoir characterization. But for a better estimation and reservoir characterization more high resolution dataset is required which is not available for this research.

3. The assessment of water usage is based on certain assumptions of discharge

and rainfall in the catchment and water utilization. As the catchment of most of the rivers in the study area extend into other adjoining countries like Bhutan and Nepal, so rainfall data is not available. The mean annual rainfall from four measuring stations in the study area has been considered for estimating runoff. As the study is undertaken with the ILR project as the background, so information is not available for the water requirement as this project is at a very initial stage of implementation especially considering the proposed links in the study area. Thus the assessment is undertaken based on some of the probable utilization of water in these types of projects.

4. The study only looks into the potential site selection, reservoir

characterization, optimal routing and an assessment of the utilization of the available water. The ecological factors like habitat defragmentation due to canal routing through reserve forest, large scale excavation, destruction of forest, response of the study area (sub Himalayan region) to such large scale infrastructure project is not considered. No estimation has been undertaken about the possible flow reduction and projected water yield due to changing climatic conditions in the near future. No assessment has been undertaken about the socio-economic and political effect of an inter basin water transfer program and last but not the least no assessment has been done about transboundary water issues as all of the suitable rivers in the study area are shared with countries like Nepal, Bhutan and Bangladesh.


80

5.3. Recommendations

The above research shows the procedure of how a preliminary assessment for inter basin water transfer needs to be followed. Based on the research methodology followed and the limitation of the research the following recommendations are proposed for future scopes of this study.

1. Incorporation of more thematic layers for the multi criteria analysis and allocation of appropriate weightage is necessary based on the scope of the project and the terrain character of the study area. This will enable better site selection of the potential reservoir sites considering all factors related to physical and socio-economic suitability.

2. SRTM Version 3 (http://srtm.csi.cgiar.org.) data is effective in preliminary

reservoir characterization but utilization of high resolution data is needed for a more precise characterization of the reservoirs, volume estimation and optimal canal routing. Data like G-DEM (30 m resolution) from ASTER Stereo which will be available from 2009 (http://www.ersdac.or.jp/GDEM/E/2.html) is one such high resolution data which can be used as the elevation input for the present research. This creates a lot of scope for future development in this field.

3. No hydrological information is known of the study area. So more

information needs to be available especially related to the river discharge (Q) and siltation. The river discharge information will enable to assess the water availability in the rivers to overcome shortfall in dry seasons. The siltation data is useful to assess the siltation potential to calculate reservoir capacity reduction over time. They are very critical as the suitable sites are all in active flood plains. Information related to actual water requirement in different sectors such as irrigation, human consumption, industrial use, power generation needs to be collected for a better assessment of the use of the stored water in reservoirs of the study area. This will ultimately enable to undertake a prefeasibility assessment of the water transfer program.

4. The information can be used as input into a preliminary cost-benefit

analysis, to get an idea of the whole IBWT as proposed by the Government of India.


81

The author wish to conclude by saying that inter basin water transfer programs incorporates a lot of issues besides reservoir site selection, capacity estimation, canal routing and the consequences related to utilization of the available water. The above research is just a stepping stone for a more detailed study. The research generates sufficient scope for future development considering the above recommendations and various limitations of data availability and restricted scope of this work.

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82

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APPENDICES

86

Appendices

Appendix – A (Landuse Map and Rain Gauge Data)

A1: Rainfall data from rain gauge station at Jalpaguri town, Jalpaiguri , West Bengal, India (unnamed Government Report, 2000).

Year Total Rainfall

of the year (in mm)

Year

Total Rainfall of the year (in mm)

1974 3839.00 1991 5148.70

1975 3445.00 1992 3392.00

1976 2531.00 1993 4520.00

1977 3377.00 1994 2376.10

1978 2278.00 1995 3265.10

1979 3140.00 1996 3200.00

1980 3415.00 1997 2883.40

1981 2824.00 1998 4729.90

1982 2804.00 1999 4255.50

1983 3462.00 2000 4029.20

1984 4343.00 2001 3754.80

1985 3384.00 2002 3265.27

1986 3818.20 2003 3918.10

1987 3798.50 2004 3276.90

1988 4171.00 2005 2891.90

1989 4495.70 2006 2649.71

1990 3971.05

APPENDICES

87

A2: Rainfall data from rain gauge station at Alipurduar town, Jalpaiguri, West Bengal, India (unnamed Government Report, 2000).

Year Total Rainfall

of the year (in mm)

1986 2508.20

1987 4540.00

1988 5016.80

1989 3162.60

1990 3622.60

1991 3886.00

1992 2793.20

1993 3655.80

1994 2696.00

1995 4936.80

1996 3887.30

1997 2888.40

1998 4743.60

1999 4395.40

2000 3537.80

A3: Rainfall data from rain gauge station at Hasimara town, Jalpaiguri, West Bengal, India (unnamed Government Report, 2000).

Year Total Rainfall

of the year (in mm)

1993 3916.10

1994 2512.10

1995 3317.00

1996 3226.00

1997 2969.75

1998 4826.60

1999 3287.75

2000 3318.25

A4: Rainfall data from rain gauge station at Banarhat town, Jalpaiguri, West Bengal, India (unnamed Government Report, 2000).

Year Total Rainfall

of the year (in mm)

1994 1859.51

1995 3391.75

1996 3250.75

1997 2977.43

1998 4859.30

1999 3406.45

2000 3766.05

AP

PE

ND

ICE

S

88

B5:

Lan

duse

/ La

ndco

ver

map

of t

he s

tudy

are

a, J

alpaigu

ri di

stric

t, W

est B

enga

l, In

dia

APPENDICES

89

Appendix – B (Reservoir Capacity Estimation)

B1: Areal extent of reservoir for different dam heights on tributary of R. Jaldhaka superimposed on IRS P6 LISS III, Nov. 2005 data.

B2: Areal extent of reservoir for different dam heights on R. Murti superimposed on IRS P6 LISS III, Nov. 2005 data.

APPENDICES

90

B3: Areal extent of reservoir for different dam heights on R. Torsa superimposed on IRS P6 LISS III, Nov. 2005 data.

B4: Areal extent of reservoir for different dam heights on R. Kaljani superimposed on IRS P6 LISS III, Nov. 2005 data.

APPENDICES

91

B5: Areal extent of reservoir for different dam heights on tributary of R. Jaldhaka (upstream) superimposed on LANDSAT TM, Nov. 1991 data.

B6: Reservoir Storage Capacity Curve for different dam heights on tributary of R. Jaldhaka (upstream) as derived from Digital terrain model.

Dam 2 New - R. Jaldhaka Tributary (Upstream)

y = 1.4049x - 33.754

R2 = 0.9959

0

10

20

30

40

50

60

30 40 50 60 70

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

. m.)


APPENDICES

92

B7: Areal extent of reservoir for different dam heights on R. Torsa (upstream) superimposed on LANDSAT TM, Nov 1991 data.

B8: Reservoir Storage Capacity Curve for different dam heights R. Torsa (upstream) as derived from Digital terrain model.

Dam 4 New - R. Torsa (Upstream)

y = 5.2371x - 129.97

R2 = 0.99920

50

100

150

200

250

40 50 60 70

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

. m.)


APPENDICES

93

B9: Areal extent of reservoir for different dam heights on R. Raidak superimposed on IRS P6 LISS III, Nov 2005 data.

B10: Reservoir Storage Capacity Curve for different dam heights R. Raidak as derived from Digital terrain model.

Dam 5 - R. Raidak

y = 3.0462x - 67.458

R2 = 0.98120

20

40

60

80

100

120

20 30 40 50 60

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu .m

.)


APPENDICES

94

B11: Areal extent of reservoir for different dam heights on R. Sankosh superimposed on LANDSAT TM, Nov 1991 data.

C12: Reservoir Storage Capacity Curve for different dam heights R. Sankosh as derived from Digital terrain model.

Dam 6 - R. Sankosh

y = 6.3261x - 127.55

R2 = 0.98960

50

100

150

200

250

20 30 40 50 60

Dam Height (m)

Res

ervo

ir C

apac

ity (

mill

ion

cu

.m.)


AP

PE

ND

ICE

S

95

App

endi

x –

C (

Wat

er U

tilis

atio

n)

D1:

Est

imat

ed w

ater

util

isat

ion

for

irrig

atio

n an

d hu

man

con

sum

ptio

n in

3 s

cena

rios

cons

ider

ing

10%

redu

ctio

n of

res

ervo

ir ca

paci

ty a

nd 1

0 %

loss

due

to e

vapo

ratio

n an

d co

nve

yanc

e.

Scenario

Vol. Available (m3)

Present Volume (m3)

Irrigation (mm/day)

Area which can be irrigated per day

(million km2) using

the full capacity for irrigation

40% of the capacity for Irrigation (m

3)


(million km2)

Human Consumption (Liters/day)

20 % of capacity for Human consumption

(m3)

Population served (in million)

No. of days of water supply

1

97

215

390

0

77

772

312

0

0.3

9

31

108

924

8

0.1

6

15

554

462

4

18

0

2

11

881

647

00

9

50

531

760

0

.48

3

80

212

704

0

.19

70

1

90

106

352

1

2.3

4

22

0

3

14

884

479

00

1

19

075

832

0

2

.00

0.6

0

47

630

332

8

0.2

4

13

5

23

815

166

4

6.4

0

27

5

AP

PE

ND

ICE

S

96

C2:

Est

imat

ed w

ater

util

isat

ion

for

irrig

atio

n an

d hu

man

con

sum

ptio

n in

3 s

cena

rios

cons

ider

ing

20%

redu

ctio

n of

res

ervo

ir ca

paci

ty a

nd 1

0 %

loss

due

to e

vapo

ratio

n an

d co

nve

yanc

e.

Scenario

Vol. Available (m3)

Present Volume (m3)

Irrigation (mm/day)


(million km2) using



3)


(million km2)



(m3)



1

97

215

390

0

68

050

773

0

0.3

4

27

220

309

2

0.1

4

13

610

154

6

15

8

2

11

881

647

00

8

31

715

290

0

.42

3

32

686

116

0

.17

70

1

66

343

058

1

2.3

4

19

3

3

14

884

479

00

1

04

191

353

0 2

.00

0.5

2

41

676

541

2

0.2

1

13

5

20

838

270

6

6.4

0

24

1

AP

PE

ND

ICE

S

97

C3:

Est

imat

ed w

ater

util

isat

ion

for

irrig

atio

n an

d hu

man

con

sum

ptio

n in

3 s

cena

rios

cons

ider

ing

30%

redu

ctio

n of

res

ervo

ir ca

paci

ty a

nd 1

0 %

loss

due

to e

vapo

ratio

n an

d co

nve

yanc

e.

Scenario

Vol. Available (m3)

Present Volume (m3)

Irrigation (mm/day)


(million km2) using



3)


(million km2)



(m3)



1

97

215

390

0

58

329

234

0

0.2

9

23

331

693

6

0.1

2

11

665

846

8

13

5

2

11

881

647

00

7

12

898

820

0

.36

2

85

159

528

0

.14

70

1

42

579

764

1

2.3

4

16

5

3

14

884

479

00

8

93

068

740

2.0

0

0.4

5

35

722

749

6

0.1

8

13

5

17

861

374

8

6.4

0

20

7

AP

PE

ND

ICE

S

98

C4:

Est

imat

ed w

ater

util

isat

ion

for

irrig

atio

n an

d hu

man

con

sum

ptio

n in

3 s

cena

rios

cons

ider

ing

40%

redu

ctio

n of

res

ervo

ir ca

paci

ty a

nd 1

0 %

loss

due

to e

vapo

ratio

n an

d co

nve

yanc

e.

Scenario

Vol. Available (m3)

Present Volume (m3)

Irrigation (mm/day)


(million km2) using



3)


(million km2)



(m3)



1

9

72

153

900

4

86

076

950

0

.24

1

94

430

780

0

.10

9

72

153

90

11

3

2

11

881

647

00

5

94

082

350

0

.30

2

37

632

940

0

.12

70

1

18

816

470

1

2.3

4

13

8

3

14

884

479

00

7

44

223

950

2.0

0

0.3

7

29

768

958

0

0.1

5

13

5

14

884

479

0

6.4

0

17

2