Hydrological Model Soil Water & Assessment Tool (SWAT)

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1 Hydrological Model Soil Water & Assessment Tool (SWAT) SWAT is a simulation catchment runoff based on estimates of daily rainfall and the topography, soils and land cover of each sub-basin. The SWAT software has the capability to investigate nutrient and sediment flows also, but there are insufficient data to establish calibrated models for these at present. Within the Lower Mekong Basin (LMB), the catchment is divided into different sub-basins to simulate this runoff according to hydrological condition and its reference station. Rainfall Climate data Land use and Soil class SWAT Model Configuration Data Input 1-Time Series Rainfall Temperature Relative Humidity Solar Radiation Wind Speed 2- Spatial River system Catchment Land Use/Cover Soil class

2 SWAT Model Configuration for LMB A1 A2 A3 A7 A4 NO AREA SUBBASINS 1 China - Chiangsaen 30 2 Chiangsaen - Luangprabang 60 3 Luangprabang - Vientiane 36 4 Vientiane - Mukdahan 94 5 Mukdahan - Pakse 59 6 Pakse - Kratie Chi upto asothon 62 8 Mun upto Rasi Salai A5 A8 A6

3 Data Input for Hydrological Model Delineation SWAT Model Configuration Land cover Soil class Hydrological Data

4 Flow cumecs Pakse Treng Se Attapeu Se Trung Nghai Se Kontum Sre Ban Don Station Volume Ratio (%) Coefficient of Effeciency Mekong Mainstream Stung Treng Kratie Sekong River Attapeu Sesan River Trung Nghai Kontum Srepok River Cau Ban Don Sre Eakrong Flow Hydrograph, ear ,000 ObsFlow Simunlate flow 60,000 50,000 40,000 30,000 20,000 10,000-1-Jan-85 1-Jan-86 1-Jan-87 1-Jan-88 1-Jan-89 1-Jan-90 1-Jan-91 1-Jan-92 1-Jan-93 1-Jan-94 1-Jan-95 1-Jan-96 1-Jan-97 1-Jan-98 1-Jan-99 1-Jan-00 Date

5 Monthly SWAT Model Output LMB Basin Water ield Monthly SWAT Model Output LMB Basin- Rainfall

6 The SWAT model set up and use is described in various Technical reports given in references including modelling of the Upper Basin and trial applications of Sediment Modelling and updating to SWAT 2005 for the 3S basin. Models and model results from studies are stored in an MRC Knowledge Base which will be available through the Master Catalogue and accessed using the MRC Toolbox. 1. Papers presented at 3 rd SWAT Conference 2005, 1 st SEA SWAT Conference 2009, 2 nd SWAT Conference WUP-A project Volume No.11 Technical Reference Report DSF 620 SWAT and IQQM Models

7 Basin Simulation Model Integrated Quantity and Quality Model (IQQM) The output from SWAT subbasins is routed through the river system, making allowance for control structures such as dams and irrigation abstractions using the IQQM program. Information on daily discharges are generated throughout the system and particularly at the primary outfalls of Kratie on the mainstream and the Great Lake in the Tonle Sap basin including Mekong Delta near river mouth. IQQM Model Configuration Data Input 1-Time Series Rainfall Evaporation Flow (SWAT) Water Use Crop Type Crop Pattern Irrigation Data Hydropower Data 2- Spatial River system Catchment

8 IQQM Model Configuration Inflow data Water consumption (domestic & industrial) Hydropower Dam Irrigation Simulation Junction

9 Calibration results Pakse Treng Se Attapeu Se Trung Nghai Se Kontum Sre Ban Don Sre Eakrong

10 IQQM Model Output - Average Water Demand Legend WATERDMAVG

11 Technical report on SWAT/IQQM model 1. WUP-A project Volume No.11 Technical Reference Report DSF 620 SWAT and IQQM Models

12 Hydrodynamic Model - ISIS A hydrodynamic model, based on ISIS software, is used to simulate the river system downstream of Kratie, including the Tonle Sap and the East Vaico in Viet Nam where wet season flooding extends beyond the LMB boundary. The hydrodynamic model represents the complex interactions caused by tidal influences, flow reversal in the Tonle Sap River and over-bank flow in the flood season with the varying inflows from upstream. Such complexity cannot be modelled by simple routing models. The hydrodynamic model thus uses outputs from the IQQM model for upstream flows under different scenarios, direct runoff from local catchments modelled using SWAT and irrigation water use modelled using IQQM. Salinity is also modelled using the hydrodynamic model. Data Input 1-Time Series Flow Discharge Water Level Rainfall Evaporation 2- Geometries River Section Flood Cell Salinity Control Structure

13 Data Input for Hydrodynamic Model Flow Discharge Rainfall

14 Data Input for Hydrodynamic Model River Section Flood Cell

15 Schematization of Hydrodynamic Model SWAT Inflow in Great Lake IQQM Inflow in Kratie Extended Sections Rainfall over Delta SWAT Inflow in Vaico Flood Cells Salinity Control Sluices Tidal WL as boundary conditions

16 Daily Flow ISIS Model Outputs 10,000 9,000 8,000 7,000 Reverse Flows in Tonle Sap 6,000 5,000 4,000 3,000 2,000 1, ,000-2,000-3,000-4,000-5,000-6,000-7,000-8,000-9,000-10, Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec-00 gfedcb [S2] Prek Dam: Flow Tidal Regime in Mekong Delta

17 ISIS Model Output Annual Flood Sisophon Siem Reap Tbeng Meanchey Ban Long Stung Treng % Battambang Buon Ma Thuot Kampong Thom Pailin Kratie Moung Roessei Kampong Cham % % Pursat Kb0_mfld_00 µ Dac Min Prey Veng % Takhmau VALUE PHNOM PENH Legend Kampong Chhnang Snuol % % Senmonorom No flood Kampong Speu 0-0.5m Takeo m m m Kampot % Long Xuyen m Sihanoukville m m m Krong Kaeb % m Ha Tien m m Kien Luong Rach Gia m >8.0m % Svay Rieng Chau Doc Cao Lanh % % % My Tho Vinh Long Ho Chi Minh City Kilometers Tra Vinh % Can Tho Soc Trang ISIS Model Output Salinity Intrusion % Svay Rieng Takeo Cao Lanh Ho Chi Minh City Chau Doc Vinh Long % Long Xuyen % Kampot Ha Tien Kien Luong Can Tho Legend My Tho Rach Gia Tra Vinh Kb0_msal_98 VALUE Khong man µ 0-1g/L Soc Trang 1-2g/L 2-3g/L 3-4g/L Bac Lieu 4-6g/L 6-10g/L Ca Mau 10-15v 15-30g/L 30-40g/L Kilometers

18 Example reference Technical report on ISIS model 1. WUP-A project Volume No.11 Technical Reference Report DSF 630 ISIS Models

19 1- Example of the study on Mekong water resources development planning by using above modeling tool World Bank

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21 1- Example of BDP Scenarios BDP2