Author(s): Butsawan Bidorn; Matharit Namsai; Warit Charoenlerkthawin; Komkrit Bidorn

Linked Author(s): Butsawan Bidorn

Keywords: Sediment load; Human activities; Water management; Sediment reduction; Riverine sediment variation

Abstract: This study aims to assess sediment variability on the Chao Phraya (CP) River delivery to the CP coast. Historical river flow and suspended sediment data recorded by the Royal Irrigation Department during 1931-2019 and sediment data observed at 17 locations along the CP River in 2020 were used to study a degree of variability in sediment loads along the CP River. The non-parametric Mann-Kendall test was used to study river discharge and sediment load trend along the river. Results from this study indicate that average river discharge decreased downstream due to water diversion by the CP diversion dam for irrigation purposes. Based on statistical analysis of the river flow and sediment data over 20 years during 1976-1996, the average river discharge upstream of the CP diversion dam was 20,000 MCM without statistical increasing or decreasing trends and reduced to almost half downstream the dam. Meanwhile, the average sediment load reduced from 5.6 Mt/y upstream the dam to 0.88 Mt/y downstream. The Chao Phraya Dam seems to be a major factor responsible for the significant change in sediment load in the CP River. Analysis of recent data reveals that the average rate of river flow and sediment load upstream during the past decade was less than previously by about 4% but the sediment load decreased significantly to 2.8 Mt/y. However, average river discharge and sediment load in the lower reach of the CP River downstream the dam ranged 11000-13450 MCM/y and 1.09-1.15 Mt/y.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0943-cd

Year: 2023