Mekong Forum on Water, Food and Energy. 2012. Presentation from Session 7: Dams, Livelihoods and Flows

1. Jory Hecht, Matthew McCartney & Guillaume Lacombe

2. Assessing Mekong dam impacts
• Reservoir storage in Mekong basin
expected to increase by an order of
magnitude from 2010-2022
• Significant debate about the
implications of additional storage
on river flows and the implications
for peoples’ livelihoods and well-
being

3. Tradeoffs
Key
Objective
Optimise
Variables
Overall Benefit
Decisions
Constraints
Impacts
•Livelihoods
•Health
•Biodiversity
Irrigated Domestic Floodplain Recession Floodplain
Fisheries
Agriculture Water Supply Hydropower Industry products Agriculture Grazing
Legislation
• local/national laws Dam operation Development drive
options • political imperatives
• international obligations
Water availability Social/economic Desired ecosystem
• hydrological regime Engineering condition
• reservoir storage conditions • present/future condition
• outlet structures • livelihoods adaptation to
dams

4. Nam Ngum 1 Dam, Lao PDR
 First large hydropower dam in Lao PDR Nam Ngum
(1972), now at 155 MW Nam Song
Nam
Song Ban Na
 Largest tributary reservoir in Mekong Div. Luang Stn.
(7 km3 active storage, 404 km2 area)
Nam
Ban Lik
 Increased dry season flows provide Hinheup
Stn.
downstream irrigation opportunities
Nam Nam Leuk
Ngum 1
 Diversions from Nam Song and Nam Res.
Leuk, two adjacent watersheds Nam Mang
Tha Ngon Nam Ngum
 New dams upstream of NN1 reduce
seasonal water level fluctuations Mekong
pre-2010 schematic diagram

5. Nam Ngum Flow Distribution
10000
Estimated inflow Releases
Discharge (m3/s)
1000
100
10
1987 1989 1991 1993 1995 1997 1999 2001 2003 2005
Flood frequency at NN1 (1987-2005) Flood frequency with dam
7000 3500
3000 1987-2005
6000
Discharge (m3/s)
1996-2005
Discharge (m3/s)
5000 2500
4000 2000
3000 1500
2000 1000
1000 500
0 0
1 10 100 2 5 10 20 50
Return Period (yrs) Return Interval

6. BELOW NN1 DAM NN1 + BAN HINHEUP THA NGON STN.
30 30 30
Dry season Wet season Dry season Wet season Dry season Wet season
25 25 25
W
/ 20 20 20
Flow (billion m3)
O 15 15 15
10
D 10 10
A 5 5 5
M
0 0 0
30 30 30
W Dry season Wet season Dry season Wet season Dry season Wet Season
25 25 25
I
T 20 20
Flow (billion m3)
20
H
15 15 15
D 10 10 10
A
5 5 5
M
0 0 0

7. Nam Theun-Hinboun Project, Lao PDR
Nam Kading
• Commissioned in 1998 Nam Kading
THPC
Dam Outflow
• Dam with live storage less than one Nam
Hinboun
day of the mean annual flow Headpond
impounds water from Nam Theun Inflow
• Water diverted to 220-MW
powerhouse in Nam Hinboun basin Mekong
Nam
Gnouang
through tunnel at up to 110 m3/s Res.
during study period
Nam
Theun 2
• Now 440 MW, 220 m3/s with Xe Bang Fai
expansion of THPC project
• Nam Theun 2 Reservoir filled in Nam Theun
2008

8. Nam Kading Flow Distribution
100,000
Inflow with u/s stations Outflow to Nam Kading Minimum release requirement
10,000
1,000
Discharge (m3/s)
100
10
1
0
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Average dry season flow (Dec-May)
200
Estimated inflow
Discharge (m3/s)
150
Outflow to Nam Kading
100
50
0
2001 2002 2003 2004 2005 2006 2007
Hydrologic Year (Jun-May)

9. Effects of Diversions on Nam Hinboun basin
1000 Nam Hinboun discharge
CS16 CS10 Maximum THPC discharge
800
Discharge (m3/s)
600
400
200
0
2008 2009 2010 2011
120 Sample time series of dry season releases
100
Discharge (m3/s)
80
60
40
Powerhouse
releases
20
0
5-Apr-09 6-Apr-09 7-Apr-09 8-Apr-09 9-Apr-09 10-Apr-09 11-Apr-09 12-Apr-09

10. Conclusions
 Dams significantly alter the downstream flow
regime (and other fluxes, nutrients and
sediment), which in turn has ecological
impacts
 The response of ecosystems is varied and
complex and currently difficult to predict
 Changes in ecosystems affect livelihoods and
well-being of people living downstream
 Changes in flow provide both constraints and
opportunities for those living downstream
 The environmental and social impacts the
new dams in the Mekong will have
consequences for many decades

11. THANK YOU