SPATIAL AND SEASONAL VARIATION OF SUSPENDED SEDIMENT LOAD IN THE MEKONG RIVER BASIN

Abstract

Sedimentation is a global environmental problem that has been placing critical impacts of irrigation, agriculture, navigation, fisheries and aquatic ecosystem. The Mekong River Basin (MRB) has recently been suffering from environmental degradation despite its global significance of biodiversity. In this study, the Revised Universal Soil Loss Equation (RUSLE) model was adopted in a GIS framework to assess soil erosion and coupled with a sediment accumulation and routing scheme to simulate suspended sediment load at monthly scale in the MRB. Suspended sediment load (SSL) measurements at nine gauging stations in the MRB, from 1987-2000, were compared with the sediment yield values simulated from the model. The average Nash-Sutcliffe efficiency was 0.64, ranging from 0.14 to 0.94, resulting in a mean coefficient of determination, R 2 = 0.62. Subsequently, reasonable soil erosion distribution in the basin and longitudinal profile and temporal changes of SSL at the monitored sites were assessed. Thus, the results confirmed the derived spatial soil erosion map explicitly in estimates of soil erosion and suspended sediment load in the relatively large river such as the Mekong River.