Download Enhancement of MRC Modelling Tools in the 3S Basin to Improve

Enhancement of MRC Modelling Tools in the 3S Basin
to Improve Transboundary River Basin Management
No Dam-BL: 1986-2005
6000
Average monthly flow (m3/s)
:
No dams under the following climate scenarios were compared:
•No Dam-BL: no dams under baseline climate
•No Dam-A2: no dams under future climate (A2 scenario)
•No Dam-B2: no dams under future climate (B2 scenario)
The basin contributes up to 20% of annual water
flows to the Mekong mainstream and provides an
important contribution of aquatic biodiversity and
ecosystem services to the downstream (Tonle Sap
Lake and Mekong Delta), especially with regards
to fish habitats (rapids, deep pools and sand bars)
and migration routes.
5000
No Dam-B2: 2010-2049
4000
3000
2000
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
7000
No Dam-BL: 1986-2005
Average monthly flow (m3/s)
6000
Hydropower development under the maximum energy production
rule were also compared:
•Definite Future-BL: definite future dams under baseline climate
•All dams-BL: all dams operating under baseline climate (1986-2005)
•All dams-A2: all dams operating under future climate (A2 scenario)
•All dams-B2: all dams operating under future climate (B2 scenario)
Presently, the basin is threatening by accelerating
hydropower development and extreme events
from climate change. There are currently nine
operating dams, 11 projects under construction
and 21 other planned projects with a total installed
capacity of 6,400 MW and a total active storage of
26,328 106 m3. The total active storage is
comparable to the existing and ongoing dam
development in the Upper Mekong basin in
China.
No Dam-A2: 2010-2049
1000
Key outcomes: Climate change results in less flows Jun.Aug. and greater flows Sep.-Nov.; a clear shift of the peak
flows by about a month. No significant change in dry season.
5000
Definite Future-BL
All dams-BL
4000
3000
2000
1000
0
Key outcomes: Dams will modify the average monthly flow
distribution dramatically by decreases wet season flows and
increases dry season flows. The operation of full
hydropower development under climate change conditions
changes monthly flow patterns by a similar magnitude as all
dams without climate change, but a slight shift in monthly
peak flows occurs.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
7000
No Dam-BL: 1986-2005
6000
Average monthly flow (m3/s)
The 3S Basin drains an area of 78,650
•Viet Nam (38%),
•Cambodia (33%),
•Lao PDR (29%).
km2
7000
Climate change and hydropower development
impact on flow regimes
The Srepok, Sesan, and Sekong (3S) Basin
5000
All dams-A2: 2010-2049
All dams-B2: 2010-2049
4000
3000
2000
1000
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
12,000
Storage (mcm)
10,000
6,363
6,000
Total
4,000
2,721
3,642
Proposed
Ongoing
0
UMB mainstrem dams
Proposed
5,000
20,000
16,000
12,000
8,000
6,203
4,000
2,000
6,000
Ongoing
0
UMB mainstrem dams
3S basin
4,000
120
Operations to maximize energy production
by storing excess flows in the wet season
to allow for an increase in potential power
generation in the dry season, results in the
largest modification of seasonal flow
patterns. Keeping water level at the full
reservoir level all times to act like a run-ofriver type scheme (Ecological Operation)
results in minimum changes to baseline
flow patterns. However, this operation will
reduce energy production by half compared
with the maximize energy operation
108
120
100
80
60
59
40
20
0
Energy
max. op.
Flood
cont. op.
Ecological
operation
3,000
2,000
Baseline scenario (no dams)
Energy maximizing operation
Ecological operation
Flood control operation
3S basin
1,000
0
Objectives of study
Jan
To enhance MRC modelling tools to quantify the potential impact of hydropower development ,
operations, and climate change on flow regimes. Potential flow changes are presented and used to
discuss consequence impacts and transboundary implications.
Modelling tools
MRC-SWAT modelling
The Soil and Water Assessment Tool (SWAT) model set up by
the MRC was chosen for simulating natural flows in the 3S
Basin. The model is a part of the MRC Decision Support
Framework and ToolBox for the Lower Mekong Basin planning.
The model was calibrated and verified with observed flow data
from 1986 to 2006. Furthermore, the model was used to
assess flow changes from the projected climate change
scenarios.
UC-HecResSim modelling
The simulated natural flows of each sub-basin from the
SWAT model under observed and projected climate were
then used as inputs to the HEC-ResSim hydropower and
reservoir simulation model set up by the University of
Canterbury (UC). The model was used to simulated
regulated flows and power production for various
hydropower operation rules and development levels. HECResSim was also added to the MRC ToolBox.
Potential changes in flows from hydropower development
and climate change scenarios were compared against a
baseline scenario (BL) without hydropower power projects.
Feb Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Dec
2,000
Transboundary implications
Existing dam operations in the Sesan River
have already caused high fluctuations of
water levels downstream, changes in water
quality, a major decline of fish populations
and species. The simulations show that
hydropower development and operation will
change the seasonal flow patterns at the
country boundaries significantly from the
baseline conditions and also cause water
level changes in the Mekong mainstream.
Nov
Wet
Flow (m3/s)
8,000
20,125
140
Dry
1,600
1,200
800
400
Lao PDR
0
500
Baseline Definite Future All dams
Wet
2
300
200
0
Baseline Definite Future All dams
Wet
Dry
4,000
3
3,000
Viet Nam
2,000
1
1,000
750
0
Baseline Definite Future All dams
Change in flow regimes from full hydropower
development and climate change in the 3S
Basin is of great concern because it will
impact habitat and livelihood downstream by
reducing wetland areas in the flood season,
submerging sandbars, changing river
morphology, and altering river bank
vegetation. These changes, together with
alteration of fish migration routes and
sediment flows, could lead to a subsequent
level of decrease of ecological and fish
productivity in the Tonle Sap and in the
Mekong Delta
Dry
400
100
5,000
Flow (m3/s)
MW
14,000
Impact of dam operations
Outlet of the 3S basin
7,000
Total
Flow (m3/s)
24,000
23,193
26,328
Wet
Cambodia
4
Flow (m3/s)
28,000
Energy (GWh/day)
16,000
Active storage
Installed capacity
15,450
Flow (m3/s)
18,000
8,000
32,000
20,000
Dry
600
450
300
150
0
Baseline Definite Future All dams
The assessment of changes in flows and water levels is essential, but it is only an initial step to
examine impacts from hydropower development. Coordination and cooperation among countries is
essential to build a comprehensive understanding of the importance of economic, environmental and
social values and assets of the basin to provide more comprehensive strategic options for dam
development and operation as well as to prepare climate change adaptation plan.