Managing fish passage through large dams

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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: e.baran@cgiar.org

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

FISH IN THE SESAN AND 3S BASINS

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

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

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

LOWER SESAN 2 DAM IN CAMBODIA

8

Sesan River

Srepok River

Sesan River

LSS

2 D

am

SpillwayTailracechannel

View of the reservoir

Height 45mLength 7,729 mInstalled capacity 400MWMean annual energy 2,311.8 GWh

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

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.

FISH PASSAGE OPTIONS IN GENERAL

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

Work up to about 30m.

6) Fish locks 7) Fish lifts

Work up to 60-70m.

FISH PASSAGE OPTIONS IN SOUTH AMERICA:

ITAIPU DAM

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

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.

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

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

A POSSIBLE FISH PASS FOR LOWER SESAN 2 DAM

C2

C1

A

B

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.

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.

CONCLUSIONS

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