Assessment of land use and climate change effects on hydrology in the upper Siem Reap River and Angkor Temple Complex, Cambodia

Siem Reap River plays a crucial role in maintaining the stability of the Angkor Temple Complex and the livelihoods of the people in the basin. Land use and land cover (LULC) have changed considerably over the last few decades, as well as climatic regime, and these, in turn, have an influence on streamflow. The objective of this study was to assess the potential impacts of future LULC and climate change on streamflow upstream from the Angkor Temple Complex. LULC maps, classification of LULC units, and projections of change were developed using Maximum Likelihood Supervised Classification and the Land Change Modeler (LCM). Artificial neural network (ANN) downscaling was applied to downscale precipitation and temperatures. The Soil and Water Assessment Tool (SWAT) was applied to assess the effects of future LULC and climate change within the upper Siem Reap catchment. The Mann-Kendall test was employed to detect any potential trends within the current and future (modelled) streamflow. The results indicate that there would be reduction of streamflow at seasonal and annual timescales, under every scenario. The annual average streamflow was reduced −69%, −63% and −75% under the Representative Concentration Pathway (RCP) scenarios RCP 2.6, RCP 4.5 and RCP 8.5 respectively. It seems that there is a sufficient water supply to sustain the Angkor Temple Complex under the current LULC and climate regime, but there would be an insufficient water supply under every future modelled scenario. Moreover, trends in groundwater levels must be taken into account, because growing population will inevitably influence groundwater balance and surface water which could potentially threaten the stability of Angkor Wat Temple, a UNESCO World Heritage Site.