Impact Assessment of Land Cover Change on Hydrology and Suspended Sediment in an Upland Watershed of Mekong River Basin in Cambodia, Using ArcSWAT

Abstract

Prek Te is a catchment located eastern upland of Cambodia where land cover has drastically changed from the last ten years due to agricultural and soci-economic development. Using a distributed hydrological model in SWAT which integrated with Geography Information System, the streamflow and potential suspended sediment loss of Prek Te River basin were computed. The temporal variation of these parameters was analyzed for three different land cover conditions (1989, 2000 and 2014) where the region underwent significant change especially in forest cover. Particularly, dense forest cover slightly decreased from 47% in 1989 to 45% in 2000 and rapidly decreased to 23% in 2014. This change in land cover caused peak flow of the river in rainy season to increase by 30% but reduced dry season flow by about 10%. Moreover, the average annual surface runoff increased by about 23% in comparison to the average annual surface runoff in 2000. The average annual sediment yield in 2000 was estimated to be 97,700 tons and increased to about 310,000 tons in 2014. Therefore, changes in land cover for the last ten years have caused the increase two times in annual suspended sediment loss from the Prek Te watershed. It can be concluded therefore that the loss in dense forest cover could have resulted in the increase surface runoff, decrease infiltration capacity, decrease in soil water storage and lower groundwater recharge rate in Prek Te watershed. The results of this study showed that land cover plays a significant role in changing basin hydrology and sediment loss, which warrants the need to define best land resource management option in order to keep river basin healthy.

Keywords: ArcSWAT, Hydrology, Land cover, Potential soil loss, Prek Te watershed