Author(s): Butsawan Bidorn, Stephen A. Kish, Joseph F. Donoghue, Komkrit Bidorn, Ruetaitip Mama
Linked Author(s): Butsawan Bidorn
Keywords: Sediment transport, dam, suspended load, bed load, human activities.
Abstract: The sediment transport characteristics and long-term trends of total sediment loads of the Nan River, which is the major sediment supply source to the Chao Phraya River, have been studied to evaluate the effects of the construction of the Sirikit Dam on sediment reduction in the Nan and Chao Phraya River system. Survey data include river cross sections, flow velocities, suspended sediment concentration, and bed load transport. Additionally, historical data on river discharge and suspended sediment load at two hydrological stations (Stations N. 1 and N. 7) operated by the Royal Irrigation Department (RID) during the period 1923-2012 are utilized to estimate the suspended sediment loads transported at the upstream and downstream of the Sirikit Dam. Based on river surveys of the Nan River during the period 2011-2013 and on historical data observed by the Royal Irrigation Department over six decades, total sediment loads of the river can be calculated. Results of this study reveal that suspended sediment loads at upstream and downstream the Sirikit Dam have a strong correlation with river discharge, and the relationships can be represented by power equations with coefficients of determination more than 0. 93. It also appears that the bed-to suspended load ratio of the Nan River varies in a narrow range between 0 and 0. 14. Time series of total sediment load at the upstream and downstream the dam over the past six decades show slight increasing trends on the Nan River. Additionally, significant reduction in the total sediment yield of the Nan River occurs during the 1976-1993 related to a drought period. Then, total sediment loads on the Nan River significantly increase during 1995-2012 as a result of flood events, which occur more frequently during the past two decades. Therefore, existing of the Sirikit Dam may not be a direct cause of a 60-85% sediment reduction on the Chao Phraya River as suggested by previous studies
Year: 2017