1. River flow modeling of the Mekong River Basin A.W. Jayawardena Department of Civil Engineering The University of Hong Kong 21-01-2006

2. Mekong Basin Located 8 º -35 º N and 92 º -110 º E 12th longest river in the world Drainage area 795,500 km 2 Main stream length 4,620 km Introduction Located in Southeast Asia, the Mekong River while providing the much needed water resources for the well being has at times been a potential threat because flooding is a regular event in this region. Simulation of river flows of impending flows/stages at key locations along the river constitute the foundation of an early warning system.

3. LSM VIC-3L model in daily water balance mode Routing Linear reservoir model Optimization MOSCEM-UA algorithm DEM River network & watershed boundary from GTOPO30 DEM Soil FAO soil map with AWAM Vegetation IGBP land cover Forcing Mekong River Commission (MRC) and GDCN for P, Tmax and Tmin with Thiessen polygon Data and Methodology

4. No.Gauge name 1Chiang Saen 2Luang Prabang 3Chiang Khan 5Vientiane 6Nong Khai 7Nakhon Phanom 8Mukdahan 10Pakse Schematic locations of selected stations

5. Objectives Look for potential existence of critical resolution for river flow simulation for the Mekong River basin Investigate the relationship intra- and inter- relationship within the VIC and routing parameters Obtain deeper understanding of the hydrological characteristics of the Mekong Basin Try to improve optimization performance peak flow simulation Study the impacts of different optimization procedures on optimization results

6. Procedure Input processing for meteorological, soil, and vegetation data Model setting up at 5 different spatial resolutions from 2  2  to 0.125  0.125  Operation with the Variable Infiltration Capacity (VIC-3L) macroscale hydrologic model and routing the outputs with linear reservoir method Optimization of the VIC and routing parameters with the Multiobjective Shuffled Complex Evolution Metropolis (MOSCEM- UA) algorithm Inclusion of peak under- and over- estimation treatment (U_O) algorithm into optimization algorithm

7. DEMLandcover Soil type Rainfall Temperate Boundary

8. Thanks.