Responses of the water-yield ecosystem service to climate and land use change in Sancha River Basin, China

Water supply is a key ecosystem service, directly influencing sustainable development of the social economy and ecological systems. Climate and land use change are two important factors that affect water supply. Since the 1990s, China has implemented a series of land use policies, such as the grain-for-green program, which have significantly changed land use patterns. However, the effect of global climate change on water resources in China is growing, resulting in water shortages and deterioration of the aqueous environment. In this context, China's land use change, concurrent with the impacts of climate change on regional water resources, has become an issue worthy of discussion. This work analyzed the effect of land use and climate change on water yield in 1990 and 2010 using the Sancha River Basin as a case study. The variations in water yield in Sancha River Basin were simulated using the water-yield module in the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model for three scenarios. The first scenario incorporated land use and climate change into the model in accordance with actual conditions. The second scenario was a simulation without climate change, and the third was without land use change. Water yield in Sancha River Basin increased by 17% between the two time periods in the actual scenario. In the scenario without climate change, land use conversions led to a 0.46% reduction in water yield. In the scenario without land use change, climate change led to a 17.50% increase in regional water yield due to precipitation. The impact of rainfall change on the Sancha River Basin water yield was as high as 97.44% while that of land use change was only 2.56%. This study shows that the grain-for-green program has negatively impacted water yield. Furthermore, to improve the ecological environment of the river basin, a comprehensive scheme for controlling water and soil erosion should be implemented according to the actual variation in water yield. This would give full consideration to the utility of water resources.