Effect of Large Scale Dams on Hydrological Regime in the Chao Phraya River Basin, Kingdom of Thailand

Abstract

The purpose of this paper is to evaluate the effect of the human activities on water resourcesand hydrological cycle. The Chao Phraya River basin was selected for this study. The Chao Phraya River basin, the largest basin in Kingdom of Thailand is located in central and northern part of Thailand. This basin has two large-scale dams named Bhumibol Dam across the Ping River and Sirikit Dam across the Nan River. This large storage dams are beneficial to the country for generatingelectricity and discharging water for the irrigation project areas and flood mitigation on both banks of the Ping, Nan and the Chao Phraya rivers.
There is no the long-term increase and decrease tendency of the precipitation. As the results of comparing the annual change of monthly runoff before and after dam construction, the minimum runoff increased and the maximum runoff degreased.
As the results of spectrum analysis using FFT, after the Bhumibol dam was constructed, the daily runoff in Nakhon Sawan had period characteristics in 3.5days and 7days and the released water from the Bhumibol dam had period characteristics in 2.5days, 3.5 days and 7days. Dam operation effected on the hydrological cycle considerably.