Dynamic Effects of Climate and Land Use Policies on Water Yield in Drylands—A Case Study in the Northwest of China

Water yield as an important ecosystem service for mitigating water scarcity in drylands, is quite sensitive to land use and climate change. Evaluating the response of water yield to land use policies in drylands under climate change is conducive to sustainable water resource management. Taking the Hohhot-Baotou-Ordous-Yulin region in the northwest of China as an example, this study used the methods of the InVEST model, trend analysis, comparative experiment, PLUS model to explore the spatial-temporal trends and driving factors of water yield variation, as well as to simulate the future water yield under different land use policy scenarios. The results showed that (1) water yield in the study area fluctuated and increased from 14.14 mm to 46.59 mm during 2000 to 2020, the places with a significant increasing trend of water yield were mainly distributed in the southeast loess hilly area; (2) climate change is the major driving factor of water yield variation with a contribution rate of 85.8–99.6%, but land use change played an increasingly important role in affecting water yield; (3) the Grain-Security-Dominated (GSD) land use policy scenario would generate the highest water yield in 2030 under climate conditions of SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5, while the Regional-Greening-Dominated (RGD) land use policy scenario has the lowest water yield in the future. The results could provide reference for the decision-making process of ecological restoration and land use planning in drylands.