water Article Did the Construction of the Bhumibol Dam Cause a Dramatic Reduction in Sediment Supply to the Chao Phraya River? Matharit Namsai 1,2, Warit Charoenlerkthawin 1,3, Supakorn Sirapojanakul 4, William C. Burnett 5 and Butsawan Bidorn 1,3,* 1 Department of Water Resources Engineering, Chulalongkorn University, Bangkok 10330, Thailand;
[email protected] (M.N.);
[email protected] (W.C.) 2 The Royal Irrigation Department, Bangkok 10300, Thailand 3 WISE Research Unit, Chulalongkorn University, Bangkok 10330, Thailand 4 Department of Civil Engineering, Rajamangala University of Technology Thanyaburi, Pathumthani 12110, Thailand;
[email protected] 5 Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA;
[email protected] * Correspondence:
[email protected]; Tel.: +66-2218-6455 Abstract: The Bhumibol Dam on Ping River, Thailand, was constructed in 1964 to provide water for irrigation, hydroelectric power generation, flood mitigation, fisheries, and saltwater intrusion control to the Great Chao Phraya River basin. Many studies, carried out near the basin outlet, have suggested that the dam impounds significant sediment, resulting in shoreline retreat of the Chao Phraya Delta. In this study, the impact of damming on the sediment regime is analyzed through the sediment variation along the Ping River. The results show that the Ping River drains a mountainous Citation: Namsai, M.; region, with sediment mainly transported in suspension in the upper and middle reaches. By contrast, Charoenlerkthawin, W.; sediment is mostly transported as bedload in the lower basin. Variation of long-term total sediment Sirapojanakul, S.; Burnett, W.C.; flux data suggests that, while the Bhumibol Dam does effectively trap sediment, there was only a Bidorn, B.