Effect of Water Withdrawal on Hydraulics and Morphology of Pumduang River, Thailand

Abstract

The HEC-6 river morphological mathematical model is applied to predict the effect of water withdrawal from the Pumduang River on its water surface and bed profiles. The river is situated in the Surat Thani province in the south of Thailand. The HEC-6 model is calibrated and verified based on field data. After the model calibration and verification, the HEC-6 is applied to predict the effect of water withdrawal on changes in water level and bed level of the river. The predicted changes are compared with the results of a physical movable bed hydraulic model of scale 1:60. The agreement is found to be satisfactory. The equilibrium river bed and water surface profiles are determined for the annual average flow and the 2-, 10-, 25- and 100-year return period floods for the cases with and without water withdrawal. The water withdrawal of 16 percent of the average annual discharge of the Pumduang river is found to have no endangering effect on the flow and morphological condition of the river