Impacts of land use/cover change on water balance by using the SWAT model in a typical loess hilly watershed of China

Land use/cover change (LUCC) plays a key role in altering surface hydrology and water balance, finally affecting the security and availability of water resources. However, mechanisms underlying LUCC determination of water-balance processes at the basin scale remain unclear. In this study, the Soil and Water Assessment Tool (SWAT) model and partial least squares regression were used to detect the effects of LUCC on hydrology and water components in the Zuli River Basin (ZRB), a typical watershed of the Yellow River Basin. In general, three recommended coefficients (R² and E_ns greater than 0.5, and P_bias less than 20%) indicated that the output results of the SWAT model were reliable and that the model was effective for the ZRB. Then, several key findings were obtained. First, LUCC in the ZRB was characterized by a significant increase in forest (21.61%) and settlement (23.52%) and a slight reduction in cropland (–1.35%), resulting in a 4.93% increase in evapotranspiration and a clear decline in surface runoff and water yield by 15.68% and 2.95% at the whole basin scale, respectively. Second, at the sub-basin scale, surface runoff and water yield increased by 14.26%–36.15% and 5.13%–15.55%, respectively, mainly due to settlement increases. Last, partial least squares regression indicated that urbanization was the most significant contributor to runoff change, and evapotranspiration change was mainly driven by forest expansion. These conclusions are significant for understanding the relationship between LUCC and water balance, which can provide meaningful information for managing water resources and the long-term sustainability of such watersheds.