The impact of water resources development on water levels of the Mekong
Partners and support•Funding: Critical Ecosystem Partnership Fund, University ofCanterbury•In-country partners: Conservation International, Mekong RiverCommission• Collaborators: M. of Environment, Aalto University, EIA LtdFinland, Research Development International, University ofWashington
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
Question 1:HOW HAS HISTORICAL WATER RESOURCESDEVELOPMENT (UP TO 2010) AFFECTED THEHYDROLOGY OF THE MEKONG AND TONLE SAP?
Dams≤ 2010 Period Number Active (Mm3) Total (Mm3) Pre 1991 9 7,853 11,609 Up to 2010 39 29,912 48,669
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
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?
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%
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)
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
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
Mean number of days between high andlow 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
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)
Water Level fluctuations from Chiang Sean to Mukdahan 200 Pre 1991 Post 1991 180 160Annual Water Level Fluctuations 140 120 CS 100 LP 80 VT MH 60 40 20 0 1960 1970 1980 1990 2000 2010
Water Level Fluctuations from Pakse to Prek Kdam 200 Pre 1991 Post 1991 180 160Annual Water Level Fluctuations 140 120 PS 100 ST 80 PK 60 40 20 0 1960 1970 1980 1990 2000 2010
Impact of Mun and Chi Basin -irrigation -hydropower (Pak Mun) 200 180 PSAnnual Water Level Fluctuations 160 ST 140 PK 120 100 80 60 40 20 0 1960 1980 2000
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?
Question 2:HOW WILL FUTURE DEVELOPMENT ANDOPERATION OF DAMS IN KEY TRIBUTARIES IMPACTFLOWS IN THE MEKONG AND DOWNSTREAM?
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
Key questions from the case study1. 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
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 2BXepian-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
Methodology Issues Model engine Outputs IPCC emission scenarios Global Circulation Models A2 and B2Climate change - Projected rainfall, temp, wind speed, solar radiation PRECIS Downscaling Model Resolution from 318 x 318 km was downscaled to 22 x 22 kmRiver flows Simulated flows at the dam SWAT sites Hydrological ModelHydropower Regulated flowsdevelopment and HEC-ResSimoperation Reservoir Operation Model Energy production 3
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
700049 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
Simulated Operation Scenarios1. Seasonal Variation: Max. energy2. Full supply: Ecologically friendly3. Low Supply: Flood control 7
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 20Flow 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
116 Individual dam 114 Cascade dam 3.Impact of the cascade dams 112 305 300 c) Xekong 4 Cascade impact Flood controlReservoir 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
6,000 Anual 4,000 Cambodia-Viet Nam boundaryImpact of climate change on extreme events 2,000 0 Sesan river 1 10 100 1000 Return period (years) 1000Climate change will significantly 30,000increase the magnitude and ND-BL:1986-2005 25,000frequency of extreme flood and ND-A2: 2010-2049 Anual peak flow (m 3/s) ND-B2: 2010-2049drought events. 20,000 15,000This 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
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 0Stung Treng -1000 3S All dams -2000 LMB Mainstream dams Kratie -3000 LMB Definite future Chinese dams -4000 500line flows 0 -5000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec -500 15
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
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 AprFlood extent Flood extent changes changes during dry during dry season season (+30%): (-10%): 0 25 50 100 0 25 50 100 Kms Kms
Landscape PatternsIs there a relationship between land use/land cover and seasonal flooding and can we use this to project future changes?
Landscape Patterns Flood duration rules (months) average year Rainfed 0-1 habitats Transitional 1-5 habitats Seasonally 5-8flooded 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)
Field PatternsHow are vegetation, soils, and water qualitypatterns related to habitats and hydrology?
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
Vegetation responses to flooding rice paddies Open water
Implications of hydrological change: Max water level Reduction in Extent of flood pulse Extent ofpermanent water caused by floodplain hydropower Min water level
Aquatic Primary ProductionHow do changes in water level and habitat impact primary production? Production andlandscape modelling procedures: Total production (tnC/km2) 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0
Changes in Aquatic Primary Production Total annual changeClimate change Hydropower Climate change + hydropower -11% to -18% -33 % - 33% to -41%
Impacts to faunaHow can we quantify potential impacts to fauna caused by hydrological disruptions?
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
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
Understanding other impacts1. Continue supporting management and research activities2. Links to aquatic foodweb3. Links to livelihoods4. Trade-offs between ecosystem services and development
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