Avoidance, Enhancement and Mitigation Avoidance measures Enhancement measures Mitigation measures. Review and collect existing data

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1 1. To develop a complete database on baseline conditions for the LMB, particularly the Mekong Delta (floodplains of Viet Nam and Cambodia). 2. To quantitatively assess impacts of proposed mainstream hydropower projects on the downstream system including (i) the flow regime, (ii) transport of sediments and nutrients, (iii) biodiversity, (iv) water quality, (v) fisheries, (vi) navigation, and(vii) related socio-economic issues. 3. To facilitate achieving consensus on the results of impact assessment of the proposed mainstream hydropower projects on the Mekong Delta and determine avoidance, mitigation and enhancement measures through close consultation with relevant stakeholders. 1

2 Outputs: Water Quantity and Quality Mike Custumized Inception PhaseInception Identification of objectives, scope Impact assessment methodology Plan and Implementation Arrangements Baseline Assessment Phase Baseline data collection and surveys Linking water-related models to other sectors Linking bio-physical models to socio-economic values Development of assessment framework and indicators Additional Studies Impact Assessment Phase Linking models, EIA framework for each sector Scenario formulation Scenario simulation Impact assessment for each sector Evaluation and prioritization of avoidance measures Avoidance, Enhancement and Mitigation Avoidance measures Enhancement measures Mitigation measures Review and collect existing data SWAT MikeBasin Agriculture Navigation Fisheries Economy MIKE11 MIKE21C Bio-Diversity Nutrients Sediment Livelihoods Additional studies 2

3 Input data Land cover Soil type DEM Water demands Meteorology Hydrology (Q,H) SWAT Tributaries MIKE BASIN Q(t), Se(t), N(t) Structure Sediments River network Water Quality Cross-section Salinity Q(t), H(t), Se(t), N(t) MIKE 21/Ecolab Delta (Tonle Sap) East Sea MIKE 21 MIKE 11/ Ecolab Mainstream MIKE 21C/Ecolab (Reservoirs) MIKE11/ Ecolab Coastal MIKE 21/ Ecolab Q(t), Se(t), N(t) Q(t), H(t), Se(t), N(t) Q(t), H(t), Se(t), N(t) Q(t), H(t), Se(t),N(t),Sa(t) Q(t), H(t), Se(t),N(t),Sa(t) 3

4 No. Nodes Number 1 Flow to Mike11 Model Flow from SWAT Hydropower 37 4 Water Demands Irrigation Linking 125 Model Calibration: ; Verification:

5 1. Mainstream Model (Cheang Sen- Kratie): km of length cross-sections - 11 Mainstream Dams 2. Delta Model canals cross-sections - More than 100 structures (dams, gates, sluices) 9 Mike 11 Mainstream 5

6 Mike 11 Mainstream 11 Template copyright # 6

7 Mike 11 Delta Model Setup: 2253 river branches 2928 river cross-sections 100 strutures Mike11 ST 7

8 Mill Tons/year Sediments - Silt SanaKham Luang Prabang Pak Beng Xayabuly Paklay SangThong_Pakchong Bankum LatSua Sambor StungTreng GA1 - Cumulative Deposition Silt GA1 - Transport Silt Baseline Transport Silt 30 Baseline Transpoirt Clay , , , ,000 1,000,000 1,200,000 1,400,000 1,600,000 1,800,000 2,000,000 Sediment Distribution on the Delta Study of the Impacts of Mainstream Hydropower on the Mekong River 8

9 Mike11 AD Baseline Salinity. 9

10 No Name of dam Full Supply Level (FSL) in masl MIKE21C Model domain length (Km) 1 Pakbeng Luang Prabang Xayabury Paklay Sanakham Pakchom Bankum Latsua Donsahong Stung Treng NA (Spill way Sill: 40, crest :59) Sambor 40/ Total (km) Lưới cong tuyến tính Pak Beng 10

11 Model Setup: km 2 Grid size: 100 x 300 m Number of cells: X: 900 Y:

12 Regional Mike 21 HD FM (DHI Singapore) Regional Mike 21 SW (DHI Singapore) 12

13 Local Mike21 HD & SW model Model Calibration Moritoring Stations Time-Series Vũng Tàu Qui Nhơn Bintulu (Malaixia) Cendering (Malaixia) Currimao (Philipin) Côn Đảo 2007 Phú Quí 2007 An Thuận Bến Trại Gành Hào Mỹ Thạnh Ông Đốc Vàm Kênh Kolak (Thái Lan) Phú Quốc

14 Template copyright # 1. Baseline Scenario: Impacts of LMB Hydropower cascade; combinations of dams covering different levels of impacts; operations and dambreak 3. Cumulative impact with others: Chinese cascade of reservoirs, hydropower development in tributaries, water abstraction/ diversion in the catchments, basin changes (hydrology and water demands) climate change etc. 4. Assessing levels of impacts of development activities to the Mekong Delta 14

15 Inception Baseline Assessment Impact Assessment Additional Studies Avoidance, Enhance-ment and Mitigation 30 15