The document discusses a study analyzing the impacts of historical and future water resource development in the Mekong River basin. The objectives are to quantify changes from historical development, estimate changes from future development in tributaries, and evaluate impacts on the Tonle Sap's productivity and fauna. It finds that historical development, primarily dams, have significantly changed water levels and the hydrology of the Mekong and Tonle Sap. Future development of dams in key tributaries is projected to further impact downstream flows in the Mekong basin. Hydropower operation rules, cascade dam effects, and climate change uncertainties could also influence energy production and flows.

2. Partners and support
•Funding: Critical Ecosystem Partnership Fund, University of
Canterbury
•In-country partners: Conservation International, Mekong River
Commission
• Collaborators: M. of Environment, Aalto University, EIA Ltd
Finland, Research Development International, University of
Washington

3. Objectives
• Quantify historical changes from water
resources development in the Mekong
• Estimate changes from future development in
tributaries
• Evaluate impact on the Tonle Sap productivity
and fauna

4. Question 1:
HOW HAS HISTORICAL WATER RESOURCES
DEVELOPMENT (UP TO 2010) AFFECTED THE
HYDROLOGY OF THE MEKONG AND TONLE SAP?

5. Pre 1991
Dams

6. Dams
≤ 1995

7. Dams
≤ 2000

8. Dams
≤ 2005

9. Dams
≤ 2010
Period Number Active (Mm3) Total (Mm3)
Pre 1991 9 7,853 11,609
Up to 2010 39 29,912 48,669

10. Pre and Post 1991
Hydrological changes
• Key indicators of change (Δ):
– Seasonal changes in water levels
– Yearly average water level raising and falling rates
– Changes in days between high and low water level
– Number of water level fluctuations per year
• All these factors affect:
– Habitat availability
– Reproduction
– Migration

11. Δ Seasonal changes in water levels
• Hydropower
wet season water levels
dry season water levels
• Irrigation
dry season
• Climate change (complex)
dry season ??
wet season ??
What months are more affected?

12. 1960-1990 vs. 1991-2010
Seasonal changes in water levels
100%
Chiang Sean (CS)
Vientiane (VT)
80%
Mukhadam (MH)
Pre to post 1991 change in
Pakse (PS)
60%
Stung Treng (ST)
Water Level
Prek Kdam (PK)
40%
20%
0%
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
-20%

14. Δ Yearly average water level raising
and falling rates (m/day)
• Raising rate: Water
Irrigation level
flood control operations Time
Climate change (higher intensity storms)
• Falling rate:
Hydropower operations (retention in reservoir)
Downstream water retention
(more water in Mekong river, low falling rate from Tonle Sap)

15. Difference between pre and post 1991
Raising and falling rates
Location Raising rate Falling rate
(% change) (% change)
CS 2 42
LP -3 18
VT -3 15
MH -8 5
PS -21 5
ST -8 12
PK -23 -11
Diminished Tonle Sap flood pulse

16. Δ Days between high and low water
level
• Number of days between high and low levels
Days
Water
level
Time
• Potential causes of change:
Dam operations (store in wet season – controlled release in dry season)
Large climate change phenomenon

17. Mean number of days between high and
low Water levels – pre vs. post 1991
180
Mean number of days between high and
170
160
low water levels
Post 1991
150
140
Pre 1991
130
120
CS LP VT MH PS ST PK
Significant variance

18. Δ Water level fluctuations
• number of times the water level changed from
rising to falling or vice versa over the year.
4
Water Level (m)
3
2
1
0
day 1 day 2 day 3 day 4 day 5 day 6 day 7 day 8
Water resources operations (hydropower, flood control, irrigation)

19. Water Level fluctuations from Chiang Sean to Mukdahan
200
Pre 1991 Post 1991
180
160
Annual Water Level Fluctuations
140
120
CS
100 LP
80 VT
MH
60
40
20
0
1960 1970 1980 1990 2000 2010

20. Diminishing effect of upper Mekong
dams
200
180 CS
Annual Water Level Fluctuations
160 LP
140 VT
120 MH
100
80
60
40
20
0
1960 1980 2000

21. Water Level Fluctuations from Pakse to Prek Kdam
200
Pre 1991 Post 1991
180
160
Annual Water Level Fluctuations
140
120
PS
100
ST
80 PK
60
40
20
0
1960 1970 1980 1990 2000 2010

22. Impact of Mun and Chi Basin
-irrigation
-hydropower (Pak Mun)
200
180 PS
Annual Water Level Fluctuations
160 ST
140 PK
120
100
80
60
40
20
0
1960 1980 2000

23. Conclusions
• Significant changes have happened in water levels.
• Water resources development is primarily responsible
(some potential effects of CC and ice melting).
• Tributary development is a key driver of change.
• Other points:
– Sediment, nutrients, and other changes have also occurred
(more analysis needed).
– How long until we observe effects on productivity?

24. Question 2:
HOW WILL FUTURE DEVELOPMENT AND
OPERATION OF DAMS IN KEY TRIBUTARIES IMPACT
FLOWS IN THE MEKONG AND DOWNSTREAM?

25. Case study: 3S Basin
• Significant flow contribution to the
Mekong river (17-20%)
• Hydropower development is
accelerating
• A transboundary river basin shared
between Lao PDR, Cambodia and
Viet Nam
• Provides an important contribution of
aquatic biodiversity and ecosystem
services: fish, habitats, and migration
routes
2

26. Key questions from the case study
1. Which has the greatest effect on downstream flow
changes: climate change or hydropower development?
2. How will hydropower operation rules impact flows and
energy production?
3. How will cascade dams impact flows and energy
production?
4. How will uncertainty in climate change modelling affect
flows and energy production?
5. How will Mekong mainstream flows be affected?
6

27. 20,000
18,000 Installed capacity
16,000 15,450
14,697
14,000
12,000
MW
10,000
8,000 6,363
6,000 Total
3,642
4,000 2,721
2,000 Proposed
Ongoing
0
UMB mainstrem LMB mainstream 3S basin
dams dams
00 32,000
Installed capacity Active storage
00 28,000 26,328
00 15,450
14,697 23,193 Total
24,000
00 20,125
20,000
00
Storage (mcm)
00 16,000
Proposed
00 6,363 12,000
00 Total
Kratie 3,642 8,000 5,226 6,203
00 2,721
4,000
00 Proposed Ongoing
Ongoing
0 0
UMB mainstrem LMB mainstream 3S basin UMB mainstrem LMB mainstream 3S basin
dams dams dams dams

28. Schematic of hydropower
development
Xe Kong 5
Lao PDR Viet Nam Duc Xuyen
Dak E Mule
Xe Kaman 4B
Xe Kong 4 Boun Tua Sran
Upper Kontum
Xe Kaman 3 Tra Khuc River
Xe Kong 3Up Xe Kaman 4A
Quang Ngai Province
(Out side Mekong Basin)
Houay Lamphan Plei Krong
Boun Kuop
Xe Katam
Xe Namnoy 5 Xe Kaman 2B
Xepian-Xe Namnoy Xe Kaman 2A
Yali
Xe Kaman 1
Xe Kong 3Down Se San 3 Dray Hilnh 1 & 2
Xe Kaman-Sanxay
Houayho
Se San 3A Se Pok 3
Xe Xou
Nam Kong 2 Se San 4
Xepian diversion dam Se Pok 4
Se San 4A
(No energy production) Nam Kong 1 Nam Kong 3
Prek Liang 2 Se San River
Se Kong River Prek Liang 1 Lower Se Pok 4
O Chum 2
(too small-not to be modelled)
Lower Se San 3
Cambodia
Lower Se San 2 Se Pok River Lower Se Pok 3
& Se Pok 2
Existing
Under construction Tonle Sap and
Proposed Mekong Delta
Mekong River

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

30. SWAT model HEC-ResSim model

31. Simulated scenarios
Baseline Climate change Hydropower CC+HD
scenario scenarios development Scenarios
scenarios
•Observed •A2 (5 GCMs) and B2 •Definite future and •All dams with A2
climate Scenarios All dams scenarios and B2 scenarios
•1986-2005 •2010-2049 •1986-2005 •2010-2049
•No dams •No dams
4

32. 7000
49
6000 1. Climate change or hydropower
ND-BL: 1986-2005
ND-A2: 2010-2049
Average monthly flow (m 3/s)
ND-B2: 2010-2049
5000
development?
4000
3000
2000
Hydropower: dry season flows increase by 95.7% and wet season flows
1000
decrease by 25 % from the baseline condition
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
7000 7000
DMST-B2: 2010-2049
Baseline:
ND-BL: 1986-2005 Baseline:
ND-BL: 1986-2005
6000 1986-2005
DF-BL: 1986-2005 6000 1986-2005
ND-A2: 2010-2049
Average monthly flow (m 3/s)
Average monthly flow (m 3/s)
DMST-BL: 1986-2005 ND-B2: 2010-2049
5000 5000
4000 Full HP 4000
A2 climate
development
3000 3000
2000 2000
1000 1000 B2 climate
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

33. Simulated Operation Scenarios
1. Seasonal Variation: Max. energy
2. Full supply: Ecologically friendly
3. Low Supply: Flood control
7

34. 2.Impact of operation rules
8,000
Outlet of the 3S basin
7,000 140 120
Energy (GWh/day)
120 108
6,000 100
80
59
60
5,000 40
20
Flow m3/s
0
4,000 Seasonal Low High
variation supply supply
3,000 Operation scenarios
2,000
Baseline scenario (no dams)
Seasonal variation operation (default)
1,000
High supply operation
Low supply operation
0
1-Jan
1-May
1-Apr
1-Jun
1-Feb
1-Sep
1-Oct
1-Mar
1-Jul
1-Aug
1-Dec
1-Nov

35. 116 Individual dam
114 Cascade dam
3.Impact of the cascade dams
112
305
300 c) Xekong 4
Cascade impact Flood control
Reservoir level (m. msl)
295
290 Conservation
285
280
275
270 Inactive
Individual dam
265
Cascade dam
260
12.0
Reservoir operation
10.3 Individual dam
Energy production (GWh/day)
10.0 Cascade dam
8.0 7.2
6.8
6.0
4.7 4.9 4.9
4.0
2.0
Energy production
0.0
Lower Sesan 2and Srepok 2 Lower Srepok 3 Xekong 4

36. 4.Uncertainty in climate change
modeling

37. Effect of climate change on energy
production

38. 6,000
Anual
4,000
Cambodia-Viet Nam boundary
Impact of climate change on extreme events 2,000
0
Sesan river
1 10 100 1000
Return period (years)
1000
Climate change will significantly 30,000
increase the magnitude and ND-BL:1986-2005
25,000
frequency of extreme flood and ND-A2: 2010-2049
Anual peak flow (m 3/s)
ND-B2: 2010-2049
drought events. 20,000
15,000
This will affect; 10,000
 Dam design criteria 5,000 Cambodia-Lao PDR boundary
Sekong river
 Dam operation i.e. flood control 0
1 10 100 1000
Return period (years)
10

39. 5. Effect on Mekong mainstream flows.
3000 “Potential downstream impact on
Kratie
Tonle Sap and Mekong delta”
Deviation from average baseline flows (m 3/s)
2000
1000
0
Stung Treng
-1000
3S All dams
-2000
LMB Mainstream dams
Kratie
-3000 LMB Definite future
Chinese dams
-4000
500
line flows
0
-5000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
-500
15

40. Key messages
 Impact of hydropower >> climate change
…and it might happen sooner.
 Flow alteration will lead to downstream impacts and
transboundary conflicts.
 Location, size, and operation of dams is critical.
 Need to understand other environmental ramifications –
sediment, nutrients, food web, biodiversity
 Coordination and cooperation among developers and
transboundary countries are necessary to minimize the
impact and maximize basin benefits
Maximize Maximize
Hydropower
Benefits
?? Basin
Benefits

41. What happens downstream?

42. Question 3:
HOW WILL FUTURE DEVELOPMENT AND CLIMATE
CHANGE IMPACT THE TONLE SAP’S ECOSYSTEM
PRIMARY PRODUCTIVITY AND FAUNA?

43. Research Overview

44. Expected changes in the Tonle Sap
Climate change and hydropower impacts on an average year
11
10 rvmpa
rvcca
9 rvgia
8 rvnca
A1b models + hydropower
7
masl
observed average
6 Hydropower
5
4
3
2
1
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Flood extent Flood extent
changes changes
during dry during dry
season season
(+30%): (-10%):
0 25 50 100 0 25 50 100
Kms Kms

45. Landscape Patterns
Is there a relationship between land use/land
cover and seasonal flooding and can we use
this to project future changes?

46. Landscape Patterns
Flood duration rules
(months)
average
year
Rainfed
0-1
habitats
Transitional
1-5
habitats
Seasonally
5-8
flooded habitats
Gallery forest 9
Open lake 10-12
Habitat code
Gallery Forest (GF)
Open Water (OW)
Rainfed habitats (RF)
0 15 30 60
Seasonally flooded habitats (SF) Kms
Transitional habitats (T)

47. Habitat Cover Changes
Habitat code
Gallery Forest (GF)
Open Water (OW)
Rainfed habitats (RF)
0 15
Seasonally flooded habitats (SF)
Transitional habitats (T)
Climate Baseline(A1b scenario)
Change map
Hydropower
Hydropower + climate change

48. Field Patterns
How are vegetation, soils, and water quality
patterns related to habitats and hydrology?

49. Field Patterns
– 8 transects, 7-16 km long – Cattle, fire, deforestation
– 77 sites,100 m2 each – Hydrology parameters:
– Vegetation and soils during dry • flood duration from map
season • water depth in wet season
– Water quality during wet season – Multivariable statistics

50. Vegetation responses to flooding
rice paddies Open water

51. Implications of hydrological change:
Max water level
Reduction in
Extent of flood pulse Extent of
permanent
water
caused by floodplain
hydropower
Min water level

52. Aquatic Primary Production
How do changes in water level and habitat impact
primary production?
Production and
landscape modelling
procedures: Total production (tnC/km2)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0

53. Changes in Aquatic Primary Production
Total annual change
Climate change Hydropower Climate change +
hydropower
-11% to -18% -33 % - 33% to -41%

54. Impacts to fauna
How can we quantify potential impacts to fauna
caused by hydrological disruptions?

55. Impacts to fauna
– Infered species information from – Assign habitat types where each
literature species is likely to be during each of
– When and where do they eat and 4 seasons
reproduce? – Link database to habitat maps

56. Habitat maps and changes
(a) water snakes
1:1,600,000
±
Settlements Settl
Settl
baseline
Settlements base
base
Settlements
gain
baseline gain
gain
baseline
loss loss
loss

57. Understanding other impacts
1. Continue supporting management and research
activities
2. Links to aquatic foodweb
3. Links to livelihoods
4. Trade-offs between ecosystem services and
development

58. Future work
• Continue 3S basin modelling:
– Update hydropower projects data
– Improve channel routing, individual/cascade
reservoir operations, and optimization
– Land use change
– Sediment and nutrient transport modelling
• Payment for ecosystem services
– Identification of potential pilot site in the 3S basin
– Improve downstream ecosystem valuation

59. Questions?
Contacts:
Tom Cochrane (tom.cochrane@canterbury.ac.nz)
Thanapon Piman (gamekung2@yahoo.com)
Mauricio Arias (mauricio.arias@canterbury.ac.nz)
www.mekongflows.org