Discharge Estimation of a Tidal River with Reverse Flow: Case of the Chao Phraya River, Thailand

Abstract

The aims of this research are to investigate the hydrodynamics in the downstream part of a tidal river and to rapidly estimate the discharge in the case of the lower Chao Phraya River, Thailand. During flood tide, the depth of the maximum velocity shifts toward the river bottom, whereas during ebb tide, the maximum velocity is located near the water surface. The discharge can be estimated from the area and the mean velocity, which is obtained from the entropy parameter and measurement of maximum velocity. When the entropic linear relationship is assumed to be constant for a station, the estimated discharge is lower than the measured value at flood tide, and in contrast, the estimated discharge is somewhat higher than the measured value at ebb tide. To get a highly reliable value of discharge estimation, the variation in location of maximum velocity with flood and ebb tides must be considered, especially where the location of measurement has a strong influence from tides.