The document analyzes the combined effects of climate change and hydropower development on the flows of the Sekong, Sesan, and Srepok rivers in the Mekong basin, highlighting concerns over aquatic biodiversity and the dependence of local populations on river resources. It concludes that hydropower development has a more significant impact on river flows than climate change, which can exacerbate extreme weather events but may be managed through large storage dams. The study emphasizes the need for coordinated efforts across borders to address the resulting downstream impacts and potential conflicts.

1. Combined Impact of Climate Change and Hydropower Development
on Flows of the Sekong, Sesan and Srepok (3S) Rivers LOGO
in the Mekong Basin
Dr. Thanapon Piman, Dr. Tom Cochrane and Mauricio Arias
University of Canterbury
Department of Civil and Natural Resources Engineering
IWA World Congress on Water, Climate and Energy 2012
13-18 May 2012, Dublin, Ireland
1

2. 3S Basin
 Driven by “tropical monsoon”:
Complex hydrology
 A transboundary river basin in Lao
PDR, Cambodia and Viet Nam
 Hydropower development is
accelerating: Energy demands
 An important contribution of
aquatic biodiversity and
ecosystem services: fish,
habitats, and migration routes
 About 500,000 people are highly
depend on river flows, natural
resources and ecosystem services
2

3. Methodology
Issues Model engine Outputs
ECHAM4 IPCC emission scenarios
Global Circulation Model A2 and B2
Climate change - Projected rainfall, temp, wind
PRECIS speed, solar radiation
Downscaling Model Resolution from ∼318 x 318 km
was downscaled to ∼22 x 22 km
River flows SWAT Simulated flows at the
Hydrological Model dam sites
Hydropower HEC-ResSim Regulated flows
development Reservoir Operation Model
and operation Energy production
3

4. Simulated scenarios
Baseline Climate change Hydropower CC+HD
scenario scenarios development Scenarios
scenarios
•Observed climate •A2 and B2 Scenarios •Definite future and •All dams with A2
All dams scenarios and B2 scenarios
•1986-2005 •2010-2049
•1986-2005 •2010-2049
•No dams •No dams
4

5. Simulated scenarios
A2 compared with scenario B2:
Lao PDR Lao PDR
•higher CO2 concentrations
•a larger human population
•greater energy consumption
A2 •more change in land use
•scarcer resources
B2 •less diverse applications of
technology
Climate change Definite future All dams
scenarios Hydropower development scenarios
5

6. Key questions from the study
• How does climate change affect rainfall patterns?
• Which has the greatest effect on downstream flow changes:
climate change or hydropower development?
• Does the effect of climate change cancel the effect of
hydropower development?
• How does climate change affect energy production and
hydropower operation?
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7. Answer 1
% Change of annual rainfall from baseline
Spatial analysis shows
that climate change
impact annual rainfall
patterns in 3S sub-
basins.
%change from
baseline in most sub-
basins varies ±20%
A2 scenario B2 scenario
7

8. Answer 2
7000
49
ND-BL: 1986-2005
6000 ND-A2: 2010-2049
s
)
3
/
ND-B2: 2010-2049
5000
Full hydropower development coupled with energy focused
4000
operation in the 3S Rivers system has the greatest effect on
3000
downstream flow changes.
2000
m
A
w
h
n
v
a
g
o
y
r
e
t
(
f
l
Outlet: dry season flows increase by 95.7% and wet season
1000
flows decrease Jun Jul 25Sep Octfrom the baseline condition
0
Jan Feb Mar Apr May
by Aug % Nov Dec
7000 7000
ND-BL: 1986-2005 DMST-B2: 2010-2049
ND-BL: 1986-2005
6000 DF-BL: 1986-2005 6000 ND-A2: 2010-2049
s
s
)
)
3
/
DMST-BL: 1986-2005
3
/
ND-B2: 2010-2049
5000 5000
4000 4000
A2
Full HP development
3000 3000 B2
2000 2000
m
m
A
w
w
A
h
n
h
n
y
o
a
v
g
y
o
g
a
v
r
e
r
e
t
(
f
(
f
t
l
l
1000 1000
Definite future
0 0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
7000 8

9. 2000
Answer 3
m
w
A
h
n
y
o
g
a
v
r
e
(
f
t
l
1000
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
7000
The impact of climate change is 6000
ND-BL: 1986-2005
DMST-A2: 2010-2049
low compared to redistributed
DMST-B2: 2010-2049
s
)
flows from the wet to dry
3/
5000
season by hydropower 4000
operation. Full HP development+
A2 climate change
3000
Climate change will not
cancel out the flow alterations 2000
m
w
A
h
n
induced by hydropower
y
o
g
a
v
r
e
(
f
t
l
1000 Full HP development+
development in the 3S Basin. B2 climate change
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
9

10. Answer 4
The A2 and B2 climate change 160
18,000
ND-BL:1986-2005 136 A2 CC
scenarios have little impact on 16,000
ND-A2: 127
2010-2049 126
14,000
energy generation. 120 ND-B2: 2010-2049
s
)
3/
B2 CC
12,000
Climate change will significantly 10,000
80 66 Baseline
increase the magnitude and 8,000
frequency of extreme flood and 6,000
40
m
W
w
A
4,000
G
o
k
p
u
n
drought events but these impacts can
e
a
E
(
f
d
h
n
l
a
y
g
r
e
)
(
/
2,000 Cambodia-Viet Nam boundary
be attenuated by hydropower 0
0
Srepok river
DF-BL DMST-BL DMST-A2 DMST-B2
operations of the large storage dams. Definite
1 future
Full HP Full HP Full HP
1986-2005 development development 2010-20491000
10 100
1986-2005 2010-2049 development
Return period (years)
with with
A2 Climate B2 Climate
16,000 change change
ND-BL:1986-2005
14,000
ND-A2: 2010-2049
12,000 ND-B2: 2010-2049
s
)
3/
10,000 10

11. Key messages
 The effect of hydropower development on flows is much
greater than climate change and it might happens sooner.
 Increase frequency and magnitude of extreme events from
climate change should be considered to prioritize
mitigation measures.
 Flow alteration from climate change and hydropower
development will lead to downstream impacts and
transboundary conflicts: Need platform for coordination,
cooperation and sharing information.
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12. Acknowledgements
 Mekong River Commission: data and information
 The Critical Ecosystem Partnership Fund: a joint
initiative of Conservation International, l’Agence
Française de Développement, the Global Environment
Facility, the Government of Japan, the MacArthur
Foundation and the World Bank. A fundamental goal is
to ensure civil society is engaged in biodiversity
conservation.
Please visit
www.mekongflows.org
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