3rd Mekong Forum on Water, Food & Energy 2013. Presentation from Session 9: Managing the impacts of dams across cascades.

1. people  science  environment  partners
Universidade Estadual
do Oeste do Paraná
MANAGING FISH PASSAGE
THROUGH LARGE DAMS
from 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
Contact: e.baran@cgiar.org

2. 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

3. FISH IN THE SESAN AND 3S BASINS

4. 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

5. Large Cyprinids
esp. Bangana, Labeo
Medium-sized Cyprinids
esp.
Scaphognathops, Mekongina, Labeo
, Bangana, Cirrhinus
Black species
esp. Channa, Clarias
Spawning in
tributaries
Medium-sized Cyprinids
esp. Scaphognathops, Mekongina,
Labeo, Bangana, Cirrhinus
Large Probarbus
(Spawning)
Small Cyprinids
esp. Henichorhynchus, Nemacheilus,
Paralaubuca, Labiobarbus, Cirrhinus
Small Cyprinids
esp. Henichorhynchus, Paralaubuca,
Labiobarbus, Cirrhinus
Migration
Upstream
Large Pangasiids
Large Pangasiids
MAY
JUN
JUL
Migrations in the 3S
AUG
SEP
OCT
NOV
Downstream
DEC
JAN
FEB
MAR
APR

6. 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

7. LOWER SESAN 2 DAM IN CAMBODIA

8. Srepok River
Sesan River
Sesan River
8

9. View of the reservoir
Spillway
Height
Length
Installed capacity
Mean annual energy
Tailrace
channel
45m
7,729 m
400MW
2,311.8 GWh

10. 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

11. 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.

12. FISH PASSAGE OPTIONS IN GENERAL

13. 1) Natural bypass channels
Work up to about 10m.
3) Vertical slot fish passes
Work up to about 30m.
2) Pool fish passes
Work up to about 10m.
4) Weir-type passes
Work up to about 30m

14. 6) Fish locks
7) Fish lifts
Work up to about
30m.
Work up to 6070m.

15. FISH PASSAGE OPTIONS IN SOUTH AMERICA:
ITAIPU DAM

16. Brazil
Paraguay
Itaipu Dam
Second largest installed
capacity (14,000 MW) after the
Three Gorges Dam's
Largest operating dam
(91.6 TWh in 2009)
Length 7,919 m
Height 196 m
Longest and highest fish
passage in the world

18. Fish passage built
in 2002, 20 years
after the dam.
10 km long
120 m high
1 natural channel,
4 fish ladders,
4 artificial lakes for
fish to rest.

19. Fish pass opening
730m long fish ladder; lake 4
1.6 km long fish ladder; lake 3
Lake 2
Lake 1; 521m long fish ladder
200m long fish ladder
6.8 km long river

21. Slope: 1.3% mean slope
Water current: 1.4 m.s-1 mean flow velocity
Discharge: 10 to 12 m3.s-1 year round
116 fish species recorded in the fish pass; biomass
dominated by a few excellent swimmers

22. A POSSIBLE FISH PASS FOR LOWER SESAN 2 DAM

26. C2
C1
A
B

28. 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.

29. 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.

30. CONCLUSIONS

31. 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