Evaluating the Effects of Climate Changes and LUCC on the Hydrological Processes Using Soil and Water Assessment Tool Models in Wangkuai Reservoir Watershed in China

Comprehensive management of lake water's quality and quantity from river eco-hydrological aspect has become an increased concern in terms of lake water ecology and environment; Baiyandian is the biggest natural lake and an important eco-function area in North China. However, due to the sharp decrease of water quantity from upstream basin, ecological and environmental problems have occurred in this lake, including frequent drying up, water pollution, and the extinction of valuable species. In this study, a small catchment the Wangkuai reservoir watershed which is located in the upstream Baiyangdian was selected as the research area. Using 3S topography and land use data as inputs for a distributed hydrological process model (SWAT), we simulated the water cycle process in Wangkuai reservoir based on changes in climate and land use-land. We elementarily analyzed the main cause of the sharp decrease of water flow in the small watershed Wangkuai Reservoir. The results of the research showed that, in the 50 years between 1958 and 2007, the ten-year average runoff decreased by 75.04%; from 1985 to 2007, warming and drying climate trend decreased the average annual runoff by 64.22%; from 1985 to 2007, the area of wood land in this watershed decreased by 13.27%, grass land and farmland increased by 4.89% and 26.15%, respectively; the contribution rate of climate changes and land use-land cover changes to the decrease of runoff were about 60% and 40%, from which we could see that climate change was the main cause of the decrease of runoff. This research could provide reference for water resource management and water environment protection of Wangkuai Reservoir.