Sedimentation
Although the large amount of sediment in the Tonlé sap Lake basin is a natural phenomenon, rapid rates of development and resource exploitation has caught the attention of observers who fear the basin itself is in danger of filling with sediment. These fears were first reported by local people living lakeside that noticed some areas becoming shallower. With increased sedimentation, already vague transit routes between capital and regional centers would likely be shut down altogether and may restrict the migration of fish into the lake.
Although the large amount of sediment in the Tonlé sap Lake basin is a natural phenomenon, rapid rates of development and resource exploitation has caught the attention of observers who fear the basin itself is in danger of filling with sediment. These fears were first reported by local people living lakeside that noticed some areas becoming shallower. With increased sedimentation, already vague transit routes between capital and regional centers would likely be shut down altogether and may restrict the migration of fish into the lake.
Because sediment contains nutrients that fuel food webs, the Tonlé sap is actually benefitting from the influx. Sediment-bound phosphorus serves as food for phytoplankton through higher plants, and research has shown that the metabolizing of the chemical contributes to food abundance and quality. Internal nutrient cycling, therefore, plays an essential role in productivity of a floodplain. The nutrients bound to suspended sediments are important for the Tonle sap system, particularly to maintain its long-term sustainability.
The reversal of the Tonlé sap river's flow also acts as a safety valve to prevent flooding further downstream. During the dry season (December to April) the Tonlé sap Lake provides around 50% of the flow to the Mekong Delta in Vietnam.
The lake occupies a depression created due to the geological stress induced by the collision of the Indian subcontinent with Asia. In recent years, there have been concerns from scientists about the building of high dams and other changed hydrological parameters in southern China and Laos that has threatened the strength and volume of the reverse flow into Tonle sap, which in turn decreases nesting, breeding, spawning, and feeding habitats in floodplain, which results in adverse impacts on fish productivity and overall biodiversity.
