a concerted effort to save tana -...
TRANSCRIPT
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A Concerted Effort to Save Tana
GLOBAL COALITION FOR LAKE TANA RESTORATION
Prepared by:
Dr. Solomon Kibret Chair, Global Coalition for Lake Tana Restoration University of California, Irvine United States
November 2017
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Acknowledgement
This project was partly financially supported by Gojjam Global Alliance of Canada and Gojjam
Global Alliance US. A number of people and institutions participated in this work. Drs. Abeyou
Wale and Yihun Dile, members of the Scientific Committee of the Global Collision for Lake Tana
Restoration, analyzed satellite images. Members of the Geospatial Center of Bahirdar
University, namely Zinabu Getahun, Minyichil Alemu and Meleket Yibabie, helped in the data
collection in the field. Members of the Amhara Regional Environmental Bureau such as Dr
Belayneh Ayele, Mezgebu Asres, and Negash Atinafu participated in drafting the strategic
roadmap.
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Background
Lake Tana is the largest lake in Ethiopia, accounting 50% of the country’s freshwater resources.
It is approximately 84 km long and 66 km wide, with a maximum depth of 14 m and a surface
elevation of 1,788 m above sea level. Its surface area ranges from 3,000 to 3,500 km²
depending on season. The lake is fed by several rivers, with 97% of the water coming from four
major rivers: Gilgel Abay, Ribb, Gumara and Megech. The annual inflow to the lake is estimated
to be 4,986 Mm3 per year. The plains surrounding the lake (i.e. the Dembiya, Fogera and Kunzila
plains in the north, east and southwest, respectively) form extensive wetlands favorable for
large- and small-scale agriculture. As a result of the high heterogeneity in habitats, the lake and
surrounding riparian areas support high biodiversity and are listed in the top 250 lake regions of
global importance for biodiversity.
Lake Tana hosts 65 fish species – a quarter of which are endemic to the lake. Among them, it is
home for eighteen species of barbus fish (i.e. of the Cyprinidae family) and the only extended
cyprinid species flock in Africa. Other common fish species include tilapia (Oreochronmis
niloticus) and catfish (Clarias gariepinus). A study in 1996 identified 217 bird species around the
lake, with a minimum of 20, 000 water birds. The lake shore is also characterized by its
extensive papyrus (Cyprus papyrus). Over 4 million people are estimated to live in the lake
catchment and at least 15 000 people are believed to live on the 37 islands in the lake
The lake has tremendous socioeconomic benefits to the country. The major economic benefits
include irrigation, hydropower generation, tourism and fishery. Several monasteries located in
the lake’s islands have historical and religious assets. Studies show that the lake basin has an
irrigation potential of 517,500 hectares of land. The potential fish production of Lake Tana is
estimated to be 13 000 tons per annum. However, its current production is only about 1000
tons per year. Recent studies indicated a serious decline in fish stocks due to the spread of
water hyacinth around fish spawning grounds.
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Current threats of Lake Tana
Water hyacinth, Eichhornia crassipes Martius (Pontederiaceae) is an exotic free-floating
perennial plant that is native to South America. It is one of the fastest growing plants known.
Water hyacinth is considered as an invasive species. If not controlled, it will rapidly and
thoroughly cover entire surfaces of lakes and ponds – dramatically impacting water flow,
blocking sunlight to native submerged plants, and depleting the oxygen in the water - often
choking aquatic animals such as fish. Major economic impacts caused by invasion of water
hyacinth include interference with navigation, irrigation and power generation, and fishery.
Water hyacinth is an aggressive invader and can form thick mats. Dense mats of this plant can
also provide ideal mosquito breeding habitats. It is very important to control water hyacinth
before the entire water surface is covered. Recent data have clearly showed that Lake Tana is
critically infested with this weed and the aquatic biodiversity of the lake is extremely at risk.
In 2011, water hyacinth was officially recognized as one of the top ten ecologically dangerous
and worst invasive weeds infesting Lake Tana. Unpublished literature indicated that about
20,000 hectares of the north-eastern shore of the lake was estimated to be infested with water
hyacinth. Likewise, a team of researchers from Bahir Dar University reported that about one-
third of the shoreline (128 km length) of the lake was invaded by water hyacinth in 2014.
According to gray the literature, the estimated coverage of the weed doubled in just two years.
As a consequence, the lake has lost 75% of its fish production in recent years. This clearly shows
the pressing threats of the weed on the lake’s environment and aquatic life.
Currently Lake Tana has faced serious ecological threats that affected its aquatic biodiversity.
Pollution, sedimentation and water hyacinth infestation are the major threats to the lake. In
October 2017, Global Coalition sent technical personnel to the area to study the current status
of water hyacinth and identify control measures to eliminate the weed and restore a healthy
ecosystem. A five-year strategic roadmap was also drafted together with the Regional
Environmental Bureau.
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Findings from the Global Collation for Lake Tana
A team of researchers from the Global Coalition for Lake Tana Restoration (a US-registered not-
for-profit initiative) and Geospatial Center of Bahirdar University spent a number of days in
September-October 2017 around Lake Tana assessing the extent of water hyacinth coverage
and assessing economic and ecological impacts of the weed on the environment. Using hand-
held GPS, the distribution of water hyacinth was determined. The results of the study indicated
that a total of 5,037 hectares of the shoreline were infested by water hyacinth as of October
2017. The infested area covers the northern, northeastern and eastern shores of the Lake that
stretches 140 km (Fig 1).
Fig 1. Current distribution of water hyacinth in the northern, northeastern and eastern
shorelines of Lake Tana, October 2017.
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A total of 20 kebeles have been infested with water hyacinth in the northern, northeastern and
eastern parts of Lake Tana (Table 1). These parts of the lake are known for agriculture and
fishery. A number of rivers enter the Lake Tana in these sections of the lake. Consequently,
large loads of sediment and dissolved nutrient washed away from upstream Tana catchment
enter the lake through these rivers. Due to the presence of high dissolved nutrient such as
nitrogen and phosphorus, river mouths have become favorable habitats for water hyacinths.
The irony is that river mouths are important breeding grounds for fish, where the weed will
impede its very existence. The presence of massive mats of water hyacinths will block sunlight
and oxygen to the aquatic habitat which will significantly affect the fish population. A recent
study indicated that the fish population in the Lake Tana basin decreased by up to 75% in the
recent years. Perhaps, the emergency of the weed contributed to this remarkable fish stock
decline.
Table 1. Coverage of water hyacinth by kebele around Lake Tana, Oct 2017.
No Zone Woreda Kebele Weed coverage in ha
Status*
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South Gondar
Dera Mitsili 260 High Fogera Wagetera 155 Intermediate
Nabega 326 High
Libo Kemkem
Tezamba 540 High
Kab 348 High Agid 132 Intermediate Kirigna 18 Low
2 North Gondar
Gondar Zuria Mitriha Aba Warka 195 Intermediate Firka Dangure 133.5 Intermediate Sheha Gomene 33.5 Low Lemba 398 High
East Dembia
Jarjar 339 High
Tana Woina 903 High
Adisge Dinge 187 Intermediate
Achera 756 High
Seraba Dablo 591 High West Dembia
Dahna Wawa 18 Low
Gorgora 13.2 Low
Abrjeha 14.6 Low
Mange 15.2 Low Grand total 5,037 * Status is defined as follows: >200 ha High; 100-200 ha intermediate; <100 ha low
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Moreover, studies show that water bodies covered with water hyacinth are subjected to about
eight times higher water loss than an open water. This resulted in more evaporation in the
wetland where the weed exists. Perhaps, the drying of the wetlands of Dera and Fogera
woredas may be related to the presence of this weed. Our findings have indicated that tens of
thousands of households have lost their livelihood because of the invasion of water hyacinth.
Unless appropriate measure is taken the impact will get worse on the local livelihood, national
economy and aquatic ecosystem around Lake Tana.
Among the 20 kebeles that are infested by water hyacinths, just four of them (Tana Woina,
Achera, Seramba and Tezamba) accounted for 55% of the total weed coverage around the lake
(Table 2). Generally, nine kebeles are considered as highly infested (>200 ha/kebele) and five
kebeles are infested at intermediate level (100-200 ha/kebele) whereas six kebeles are infested
at low level (<100 ha/kebele) (Fig 2). Satellite images indicated that the weed were expanding
at a rate of 13 ha per day during the rainy season (June- September) (Fig 3), mainly due to poor
planning and management of manual campaigns. During these campaigns, people were not
trained about weed removal procedures and designated sites were not arranged for disposal of
the harvested weed. Most of the harvested weeds were left at the edge of the shoreline
subjected to be washed away by rain – which then dispersed the weed to a wide area as the
weed also propagates vegitatively through its detached stolon.
Fig 2. Relative density of water hyacinth across Lake Tana, Oct 2017
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Our study revealed the tremendous impact of water hyacinth on the functions of the Lake and a
well-designed weed management approach is required to stop the weed from covering the
entire lake. Satellite images showed that water hyacinth infested areas are very shallow and
this understanding is important in selecting appropriate water harvesting machines based on
local context. Based on the findings of this study, experts from the Regional Environment
Bureau, Global Coalition and Bahirdar University drafted a five-year action plans that need to
be done in order to eliminate the weed and restore a healthy ecosystem.
Fig 3. Periodic increase of the water hyacinth mat around Lake Tana, based on high
resolution satellite images (Note the difference in coverage between satellite data) (Wale et
al, GCLR Scientific team)
Fig 4. Water depth of areas infested with water hyacinth generated from satellite images
(note shallow areas of the lake are currently affected by the weed) (Wale et al, GCLR
Scientific team)
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What need to be done?
The Amhara National Regional State Regional Environmental Bureau in collaboration with
Global Coalition and Bahirdar University has drafted a five-year strategic document that maps a
detailed plan of actions needed to eliminate the weed and rehabilitate the degraded
environment of the lake’s catchment. The strategies identified short-term and long-term action
plans. A total of 3 million USD is required to implement all activities planned for the next five
years.
Short-term plan
The short-term plan aims creating a strong capacity at regional and local level and implement
water hyacinth elimination activities across Lake Tana within the next one to one-and-half
years. The cost for short-term activities is USD 700,000.
a) Capacity building: In the short-term, a special Unit called “Water hyacinth control and
management Unit” will be structured at the Regional Environmental Bureau. This Unit
will lead and coordinate all activities around Lake Tana. This Unit will support and work
closely with local NGOs and other stakeholders to achieve the anticipated goals of the
strategic document. Highly trained professionals (including experts of aquatic plant,
environment, GIS and M&E) will be hired. The Unit will also have kebele coordinators in
each of the 20 infested kebeles. Kebele coordinators will be trained locally and ensure
the implementation of action plans at local scale. In addition, international trainers with
a great deal of experience in water hyacinth control in Africa and elsewhere in the world
will be engaged to train experts at governmental and non-governmental agencies who
are working to address Lake Tana’s challenges.
b) Water harvesting machines: three water hyacinth harvesting machines are needed to
work in northern, northeastern and eastern parts of the lake. Daily operational,
maintenance and manpower costs are calculated. Conveying belts that extend from the
water body to the dry land are also required to unload the harvested water hyacinth
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from the machines and transport it to the shoreline. Carts and trucks will then transport
the harvested weed from the shoreline to the designated disposal area (large pits)
prepared away from the water body. The weed currently existing in twelve highly
infested kebeles (of the total 18) will be removed using these machines.
c) Manual removal: For health and practicality reasons, manual weed removal are
confined to only a few kebeles which are with low risk of schistosomiasis and practically
possible.
d) Grass plantations: Local studies indicated that endegenous grass species help avoid
water hyacinth expansion due to their ability to absorb excessive nutrients from the
water. In areas where water hyacinth is removed, such grasses will be planted and
maintained in order to create conditions unfavorable for the weed.
e) Waste water management system: A well-studied waste water management system
will be implemented around Lake Tana in order to reduce dangerous waste water
influent into the lake catchment.
f) Operational researches: Areas of knowledge gap will be identified by the Scientific
Committee and researches will be conducted to understand the mechanism of water
hyacinth propagation and distribution. Environmental variables that contribute to
favorable conditions for water hyacinth development will also need to be assessed well.
The effect of control measures will also be periodically assessed and approaches will be
revised accordingly. Biological control measures are still in “study” phase and this needs
to continue until we understand their impact on the environment.
Long-term
i) Environmental rehabilitation: The environment of Lake Tana has deteriorated due to
high rates of deforestation and increased agricultural practices. Afforestation programs
are needed to restore the forests of the catchment. Planting endegenous plants and
protecting deforestation is critical to rehabilitate the degraded environment and reduce
soil and nutrient erosions upstream of the lake.
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ii) Ecosystem payment: Regulations will be drafted to charge ecosystem payments from
beneficiaries operating businesses around Lake Tana. This helps to generate income for
environmental management activities. Such incomes help reinforce wastewater and
environmental management activities around the lake’s catchment. Businesses will be
trained to be environmentally friendly.
iii) Improving fish productions: New policies and regulations are needed to protect illegal
fishery and maintain a healthy fish habitats. Periodical trainings and discussions will be
conducted with the fishery community to help them contribute in maintaining a healthy
aquatic environment.
iv) Improving agricultural practices and livestock management: Improved agricultural
practices are required to reduce soil erosions. New technologies and agricultural
practices that fit the area traditional and cultural assets will be implemented and such
practices will help manage the environment better. Improved livestock management
will be practiced to avoid overgrazing which facilitates soil erosion.
Monitoring and evaluation
Monthly, quarterly and annual field and satellite data will be collected and analyzed by an M&E
Team composed of experts from the Global Coalition, Bahirdar University and international
universities. Time-series satellite images will be analyzed to monitor the status of water
hyacinth and environmental factors around Lake Tana. These reports will be discussed with the
Regional and Federal Environment Bureaus in Ethiopia. In addition, the reports will be publicly
available on the Global Coalition website for anyone interested to follow-up the work. Global
Coalition will host symposiums annually to discuss M&E findings with Chapters formed in each
state and country across US, Canada, Europe and Australia. The Board of Trustees of the Global
Coalition will oversee overall activities of the Coalition and partners working to address the
current challenges of Lake Tana. The Coalition aims to be open, transparent and participatory in
decision-making and directions it takes while managing and providing technical, material and
financial supports to the work done around Lake Tana.
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Picture: Water hyacinth mat in Achera, Dembia Woreda, Ethiopia (Oct 25, 2017)