2021 Volume 12 Issue 2 Pages 201-208
Land use-land cover changes (LULCC) brought by increasing population and food demand could affect not only the fluxes of water, sediment, contaminants and energy, but also ecological, physical and socioeconomic aspects in the environment. In this study, the Soil and Water Assessment Tool (SWAT) model was used to examine the effects of LULCC on hydrological processes of Stung Sangkae catchment in Tonle Sap Basin, Cambodia. The performance of the model was evaluated through uncertainty sensitivity analysis, calibration, and validation. The time series of LULCC were used to estimate the streamflow and the water balance in the catchment based on five interval years (1998, 2003, 2008, 2013, and 2018). From 1998 to 2018, the coverages of forest land, wetland, and the paddy rice decreased by 5.1%, 1.4%, and 1.2%, respectively. The forest land and wetland were converted into cultivated land with an increase of about 7.6% over the study periods. These changes resulted in significant variations of water balance (2000-2018) namely: i) an increase of average annual surface runoff (SURFQ) by 10 mm; ii) 3 mm reduction of the average annual lateral flow (LATQ); iii) 6.2 mm reduction of the average annual groundwater (GW); iv) reduction of the average annual evapotranspiration (ET) by 0.97 mm; and v) an increase of average annual water yield by 0.9 mm. On a monthly basis, the model results had shown a reasonable agreement with the observed values as shown by the coefficient of determination (R2) = 0.41, Nash Sutcliff efficiency (NSE) = 0.40, and percent of bias (PBIAS) = 0.34. Based on the validated water discharge and water balance results in 2018, LULCC have impacted the environmental sustainability, especially the streamflow that caused flooding at the downstream watershed due to decline in forest cover at the watershed.
