Solomon B. Gebre

1
Potential Experience of Dams in Ethiopia

• Solomon B. Gebre
• Project Manger
• Design of (four) dams in Lake Tana Sub-basin
  Project

2
Outline of the Presentation

• Country Background
• Water Resources
• Potential Status of Development
• Irrigation
• Hydropower
• Water Supply
• Existing dams
• Lessons To be Learnt (Two Case Studies)
• Dams under construction
• Future for dams
• Local Context
• Regional Context

3
Country Background

• One of the 10 Nile Riparian Countries
• Population - 72.4 Million in 2004
• Growth rate - 2.3 per annum
• Population by 2016 96 Million
• Total Land Area - 1.104 x 106 Km2
• Socio-economy
• Agriculture is the dominant sector
• Largest Livestock population in Africa
• Per Capita income 90 -100 USD
• Water Supply coverage ca.35
• Electricity coverage ca.

4
Water Resources

• 12 River Basins
• Total Surface water Potential of 122 BCM
• Renewable ground water Potential of 2.6 BCM
• About 97 of the surface water drains to
  neighbouring countries
• Water Tower
• Contribution to Nile Water ca. 86

5
Primary x-ics of Water Resources

• Extreme interannual Intra-annual variability
• Droughts
• 19 periods of widespread severe food shortages
  in the past 100 yrs alone
• Spatial variability of rain flow
• Rainfall mainly in the highlands
• Lowlands are arid to semi-arid
• International nature of its most significant
  water resources

6
Potential Status of WR Development

• Hydropower
• Pot. Economical - 160 GWh or 30,000 MW
• Developed ca. 800 MW
• lt 3
• Irrigation
• Pot. Economical 2.7 Million ha
• Developed ca. 290,000 ha
• 10.8
• Water Supply coverage
• (Recent estimate by the MoWR)
• Overall 47
• Urban 80
• Rural - 41

7
Justification for Dams

• Low level of development
• Food security of its peoples
• Access to Safe drinking water supply
• Access to affordable electricity supplies
• Resources of the country (Land, Water, Labour)
• Water resources are highly variable (spatially
  and temporally)
• Dams are required to safeguard its people against
  the ill-effects of recurrent drought and bring
  about development
• Regional development specially by tapping the
  countrys huge Hydropower Resources for the
  regional market

8
Existing dams

• Authors compilation from various sources
• gt 50 Large dams ( According to ICOLD
  Classification (2003))

• FAO - Aquastat Database 2006
• 10 Large dams

greater than 15 m in height from base to crest,
or storage capacity exceeding 3 million cubic
meters for heights between 5 and 15 m
9
Important Large Dams in Ethiopia
N Name of dam Major basin Yr. Completed Height (m) Initial Capacity (x103 CM) Purpose
1 Abasamuel Awash 1939 22.00 65 000 HP
2 Alwero Baro Akobo 1995 16.00 74 600 IRR
3 Angereb Tekeze 1991 34.00 5 300 WS
4 Dire Awash 1999 46.00 19 000 WS
5 Finchaa Blue Nile 1973 25.00 650 000 HP,IRR
6 Gafarsa Awash 1955 17.00 7 000 WS
7 Gilgel Gibe Omo-Gibe 2004 41.00 839 000 HP
8 Koka Awash 1960 42.00 1 860 000 HP,IRR,FP
9 Legadadi (Main) Awash 1979 40.00 38 000 WS
10 Legadadi (Subsidiary) Awash 1979 22.00 4 000 WS
11 Melka Wakena Wabeshebele 1988 40.00 750 000 HP
12 Midimar Tekeze 1996 33.00 10 000 WS
13 Chara Chara Blue Nile
1996 9 9,100,000
Regulation
Inoperative since 1970 Only the dam
construction has been completed CM Cubic
Meters
HP-Hydropower, IRR-Irrigation WS-Water
Supply, FP-Flood Protection
10
Microdams

• Small dams (micro-dams) constructed for
  irrigation supply are concentrated in the
  Northern Amhara and Tigray regional states.
• Construction took place b/n 1995 2000
• 64 Dams in Tigrai Region
• 28 are large dams according to ICOLD
  classification
• 14 dams in Amhara Region
• 12 are large dams according to ICOLD

11
Performance of the Microdams

• According to a study in 2006 (Tefera B.), out of
  the 14 microdams in Amhara
• Only one of the 14 dams is functioning according
  to the plan of implementation
• hydraulic problems (16.7),
• hydrological problems (41.7),
• sedimentation problems (33.3),
• seepage failures (58.3), and
• structural failures (8.3).

• According to a study in 2003 (VLIR), out of the
  64 microdams in Tigrai
• Only 18 dams had no problems
• 24 dams have seepage problem
• Nine dams have sedimentation problems
• 13 dams have both sedimentation seepage
  problems

12

• Damaged spillway (Hydraulic failure)

• Syphon used to offtake water b/c of clogging of
  the intake

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Common Problems encountered in Microdams

• Common problems identified include
• Overtopping due to inadequate spillway capacity
  flood estimation problem
• Seepage through foundation, abutments and
  reservoir area site selection problem
• Cracking or structural failure geotechnical
  problem
• Less inflow in the reservoir hydrological
  analysis problem
• Sedimentation- design problem and lack of
  watershed Mgt.
• Lack of proper maintenance and rehabilitation
  work
• The rush in implementation without adequate
  investigation in all aspects
• Problems identified should give a good lesson for
  future building of similar dams.

17
Dams under construction
N Name of dam River basin Expected year of completion Dam Ht. (m) Purpose
1 Tendaho Awash 2008 40  
1 Tendaho Awash 2008 40 Irrigation of ca. 60,000ha 
2 Kesem Awash 2008 90  
2 Kesem Awash 2008 90 Irrigation of ca. 20,000 ha 
3 Koga Abbay 2007 21 Irrigation of ca. 7000 ha
4 Tekeze Tekeze 2011 185 Hydropower of 300 MW, irrigation d/s of 60,000 ha
           
5 Gilgel Gibe II Omo-Gibe 2008 21 Hydropower of 420 MW
6 Gibe III   2011 240  
6 Gibe III Omo-Gibe 2011 240 Hydropower of 1870 MW
Construction to begin soon
18
Dams Under Construction

• Koga Dam

• Basin Blue Nile
• Purpose Irrigation Ca. 7000ha
• Project includes integrated WSM on 22,000ha
• Dam height 21m
• Embankment Dam
• Reservoir storage
• Reservoir area 1400 ha
• Financed by AfDB

19
Dams under construction contd
Kesem Dam

• Basin Awash
• Multipurpose dam
• Dam ht. 90m
• Embankment Dam
• Irrigation 20 30,000 ha of sugar cane
• Hydropower under study
• Problems due to faults and artesian hot spring at
  dam foundation
• Financed by ETH. Govt

20
Dams under construction Contd
Tendaho Dam

• Basin Awash
• Irrigation dam
• Dam ht. 40m
• Embankment Dam
• Reservoir storage 1.86 BCM
• Irrigation 60,000 ha of sugar cane
• Financed by Eth. Govt
• When Kesem Tendaho Projects start operation
  sugar production will increase fivefold

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Dams versus the Environment

• Impact of dams on the Environment

• Impact of Environment on Dams

• Reservoir sedimentation due to land degradation
• Nutrient accumulation

• Physical, biological and socio-economic impacts
  of dams

22
Koka Dam Reservoir Sedimentation Its Impacts
(Eyasu E. 2003)

• Sediment deposited in the reservoir
• (over the past 40 years) 494 Mm3
• Average annual sedimentation rate 12 Mm3 or
  2115 t/km2 
• Loss of storage volume from designed storage
  capacity
• a) Designed storage capacity 1,667 Mm3
• b) Current storage volume 1,186 Mm3
• c) Loss of storage volume 481 Mm3
•  
•  
• Remedial measures to reduce reservoir siltation
•  
• Sediment removal options
• Flushing Unacceptable downstream impacts
• Dredging Cost Very expensive US 8 9 per m3
  This means US3.9 Billion for Koka dam
• Disposal
• Other Engineering solutions
• Raising the dam
• Interbasin transfer of the river flow
• This will have serious social environmental
  problems

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• Loss of power generation capacity
• c) Energy equivalent of per m3 of water 0.266
  KWh
• d) Energy equivalent of 481 Mm3 of lost volume
  128 Million KWh
• e) Price per KWh 0.473 Eth. Birr
• f) Total money value of lost power generation
  capacity
• 128 X 106 KWh X 0.473 Eth. Birr/KWh 60.5
  Million Birr or 7.5 Million USD
•  Other secondary but important impacts are
• loss of Reservoir capacity to regulate water
  supply for irrigation and flood control services
  downstream.
• which in turn resulted in breakage of dikes and
  flooding of sugar plants and down stream towns.
• Severe flood hazards have become a common
  phenomenon in the downstream of Awash basin.

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Experience from Gilgel Gibe Dam

• found on the Gibe River in the Omo-Gibe River
  basin
• built for the purpose of hydropower.
• Rock fill dam with bituminous upstream facing
• Maximum height of 41m with a total storage
  capacity of 91 MCM
• The generation capacity of the plant is 184 MW
  (three 61.3MW units)
• Firm capacity 640GWH
• started in 1997
• commissioned in 2004.
• financed by the World Bank the Government of
  Ethiopia.

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• Category "A" Environmental Impact Classification
  due to some major environmental and social issues
• the involuntary resettlement of 706 households
  (ca. 5,000 people)
• loss of 300 ha of riparian forest for wildlife
• altered downstream flow of 16 km of the Gilgel
  Gibe river,
• and increased habitat for water-borne disease
  vectors
• resettlement was completed two years ahead of
  impounding, 4 years ahead of completion of civil
  works.
• resettlement cost was estimated at US4,600 per
  household

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• post-resettlement assessments carried out in Dec.
  2005
• the resettlement program was indeed carried out
  according to the RAP in line with World Bank
  Guidelines
• Positive Indicators
• the quality of the new houses is superior to the
  old houses
• walking distance to health centers as well as
  schools has been considerably reduced
• Underperformance indicators
• the average yield level for all types of crops
  has been reduced by 54,
• the number of livestock owned by the resettled
  household has been reduce by 72
• social infrastructure such as schools, health
  clinics, and water points are in poor condition
  and in need of immediate maintenance

27
Conclusions Drawn from The Post-Resettlement
Assessment

• In spite of some underperformance, all
  indications point to the fact that the PAPs are
  better off now than prior to the resettlement
  effort
• This has shown that with proper planning and
  implementation, it is possible to develop strong
  resettlement efforts
• In resettlement matters, this project was the
  first one in the history of Ethiopia to carry a
  constitutional resettlement under the New
  Constitution
• The Bank has also acknowledged (June 2001) the
  project as good practice.

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Planned dams

• At present, the feasibility study and detail
  design of at least 12 large dams for irrigation
  development in four river basins is underway
• When implemented, these dams will have a
  potential to irrigate well over 150,000 ha
• MoWR has planned at least 20 power projects
  involving large dams with an aggregated power
  generation capacity of over 10000 MW which are at
  various levels of study
• Four of these projects involve the construction
  of large dams on the main Blue Nile River.
• When implemented, these projects will enable
  Ethiopia to export environmentally friendly power
  to its neighbors and Nile Basin riparian
  countries.

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Regional projects under NBI

• Projects accepted by the NBI Council of Ministers
  consist of 4 hydropower and 4 irrigation projects

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Dams in Lake Tana Sub-basin
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IN CONCLUSION

• Ethiopias Path to Survival Development
• Depends to a large extent on
• Developing available resources (Land, Water
  Labour)
• Which requires
• Investing in Water Infrastructure
• where
• Dams are at the heart of this investment
• However
• Good governance of dams is a pre-requisite for
  sustainable development