Managing fish passage through large dams
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Transcript of Managing fish passage through large dams
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people Ÿ science Ÿ environment Ÿ partners
MANAGING FISH PASSAGE THROUGH LARGE DAMSfrom Itaipu (Brazil) to Lower Sesan 2
(Cambodia) Eric BARAN, Pelle GÄTKE, Sergio MAKRAKIS, Maristela MAKRAKIS, Timo RÄSÄNEN, SARAY Samadee, Helio Martins FONTES Jr.
3rd Mekong Forum on Water, Food and Energy, Hanoi, Viet Nam, 19-21 November 2013
Universidade Estadual
do Oeste do Paraná
Contact: [email protected]
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OUTLINE
Fish in the Sesan and 3S Basins
Lower Sesan 2 Dam in Cambodia
Fish passage options in general
Fish passage options in South America: Itaipu dam
A possible fish pass for Lower Sesan 2
Conclusion
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FISH IN THE SESAN AND 3S BASINS
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Biodiversity in the 3S system
o 329 fish species = 42% of all Mekong species (basin area =10% of the Mekong)
o 17 endemic species found nowhere else in the world
o 5 endangered fish species (Red List)
Fish migrations in the 3S
o 89 migratory fish species belonging to 15 families.
o Sesan River: at least 41 migratory species contributing 60% of the total catch
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Small Cyprinidsesp. Henichorhynchus, Paralaubuca,Labiobarbus, Cirrhinus
JAN FEB MAR APRMAY JUN JUL AUG SEP OCT NOV DEC
Upstream
Downstream
Migration
Small Cyprinidsesp. Henichorhynchus, Nemacheilus, Paralaubuca, Labiobarbus, Cirrhinus
Large Cyprinidsesp. Bangana, Labeo
Large Probarbus (Spawning)
Medium-sized Cyprinidsesp. Scaphognathops, Mekongina, Labeo, Bangana, Cirrhinus
Spawning in tributaries
Black species esp. Channa, Clarias
Large Pangasiids Large Pangasiids
Medium-sized Cyprinidsesp. Scaphognathops, Mekongina, Labeo, Bangana, Cirrhinus
Migrations in the 3S
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Fish consumption in the 3S
Fisheries Administration 2013 study :
o People in mountains and plateaus consume on average 52.3 kg of fish and other
aquatic animals per person and per year
o Out of this, inland fish represent
26.5 kg/person/year
o Migratory species = 58% of the fish
diet of “Mountains and plateaus”
people
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LOWER SESAN 2 DAM IN CAMBODIA
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8
Sesan River
Srepok River
Sesan River
LSS
2 D
am
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SpillwayTailracechannel
View of the reservoir
Height 45mLength 7,729 mInstalled capacity 400MWMean annual energy 2,311.8 GWh
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Conclusions of the LSS 2 EIA executive summary about fisheries “Impacts on fish will be severe as many species are migratory (around 66%) and their passageway through the project area will be blocked by the dam. This will also have impacts downstream of the dam into the Mekong River and potentially also the Tonle Sap Lake”
PEC and KCC 2008, Executive Summary
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Plans about a fish pass at Lower Sesan 2 site
“Due to geographical condition and economical feasibility, no fish pass will be installed in the Sesan 2 HPP. This means that the proposed dam will totally block upstream migration of fish. Probably a fish pass of more than 15 meters high could not accommodate numerous migrating fish species of the Mekong Basin.”
PEC and KCC 2008, section 3.11.
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FISH PASSAGE OPTIONS IN GENERAL
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1) Natural bypass channels
Work up to about 10m.
2) Pool fish passes
Work up to about 10m.
3) Vertical slot fish passes
Work up to about 30m.
4) Weir-type passes
Work up to about 30m
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Work up to about 30m.
6) Fish locks 7) Fish lifts
Work up to 60-70m.
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FISH PASSAGE OPTIONS IN SOUTH AMERICA:
ITAIPU DAM
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Itaipu DamParaguay
Brazil
Second largest installed capacity (14,000 MW) after the Three Gorges Dam's
Largest operating dam (91.6 TWh in 2009)
Length 7,919 mHeight 196 m
Longest and highest fish passage in the world
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Fish passage built in 2002, 20 years after the dam.
10 km long120 m high
1 natural channel, 4 fish ladders, 4 artificial lakes for fish to rest.
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6.8 km long river
Lake 1; 521m long fish ladder
Lake 2
1.6 km long fish ladder; lake 3
730m long fish ladder; lake 4
Fish pass opening
200m long fish ladder
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Slope: 1.3% mean slopeWater current: 1.4 m.s-1 mean flow velocityDischarge: 10 to 12 m3.s-1 year round116 fish species recorded in the fish pass; biomass dominated by a few excellent swimmers
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A POSSIBLE FISH PASS FOR LOWER SESAN 2 DAM
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C2
C1
A
B
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Path B would be 13 km long. It would start 9.8 km downstream and would reach the reservoir about 5.5 km away from the spillway. The average slope would be 0.15%, i.e. quite passable for most species. that path would require digging a 5.5 km long canal connecting two natural streams, between altitudes of 99 and 90 meters.
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Flow modeling shows that:
- the water consumed by the fish pass would reduce water availability at power plant by 0.6% (best case scenario) to 1.2 % (worst case scenario) maximum
- the water consumed by the fish pass would reduce power production by 0.6% (best case scenario) to 1.1 % (worst case scenario) maximum.
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CONCLUSIONS
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o Fish resources are abundant in the 3S system and important to Cambodian people
o The Lower Sesan 2 project has hastily dismissed fish passage mitigation options
o New options for fish passage at high dams can be learnt from South America
o A fish pass using natural streams could allow connecting the reservoir to the downstream river without modifying the dam design
o The pass would consume at most 1.2% of the reservoir water
Such potential calls for a detailed feasibility study