Sediment and suspended solids are highly dynamic in time and space in Tonle Sap Lake (TSL). Sediments also play critically important roles in the lake’s geomorphology and biogeochemistry and sustain its productive ecosystem. The majority of the sediment grain is fine silt and clay (>60% in mass), and the median sediment grain size (D50) is mostly 5–8 μm in the lake and on its floodplains. Suspended solids have a large spatiotemporal variation in concentration ranging from 1 to 752 mg/L. This wide range is caused by seasonal variations in water level and sediment load inputs from the Mekong River and the surrounding tributaries of TSL. The largest sediment flux to the lake is observed in August, when almost 2.5 MT of suspended solids are transported from the Mekong, through the Tonle Sap River and into the lake, of which approximately 80% is trapped mainly by the shore zone and floodplain. Thus, the lake and its floodplain work as a sink of suspended solids in the wet season (high-water period) and as a source in the dry season (low-water period) because the water level controls the effect of wind-driven turbulence on resuspension.
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