A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Water Engineering and Management

Thesis (M.Eng.) - Asian Institute of Technology, 2007

Most of computer models for simulation and prediction of sediment transport in rivers and reservoirs are one-dimensional. Although truly two- or three-dimensional models are available, they require extensive field data for calibration and may be difficult to apply. A quasi-two dimensional model for water and sediment routing is an effective tool for solving river engineering problems. This thesis provides a brief description of the systematic and integrated approach based on well established sediment transport equations and the Bureau Reclamation's Generalised Stream Tube model for Alluvial River Simulation (GSTARS 2.1 ). Changes in elevations of bed profile and various cross sections within Son La reservoir were modeled using GSTARS 2.1. The model predicted a reduction in reservoir storage capacity of 46.1 % after 100 years operation of Son La reservoir. In term of reduction in annual energy generation, deposition of sediment in the Son La reservoir, would decrease the annual energy by 0.4, 1.2, 5.6, 10.3, and 12.3 % for 10, 20, 50, 80, and 100 years, respectively. Based on results of flushing model by using RESCON model, the Son La reservoir should be flushed at the beginning of wet season (June) of each year. By maintaining the reservoir water level at 175 m MSL, for 5, 10, and 15 days complete drawdown with flushing discharge at least 2500, 1500, and 1000 m3/s respectively, the volume of flushed sediment is equal to the annual inflow of sediments 54.9 10^6 tons.