Water availability is at the core of sustainable socioeconomic development and ecological conservation along with global climate and land use changes, especially in the areas that experience water problems. This study investigated the impacts of land use change on surface runoff and water yield with scenario-based land use change in the upper and middle reaches of the Heihe River Basin, the second largest inland river basin in the arid region of northwestern China. Firstly, three land use structure scenarios were established, with different water utilization ratio levels (low-level, middle-level and high-level water utilization ratios). Then the spatial pattern of land uses was simulated with the Dynamic of Land System (DLS). Thereafter, the simulated land use data were used as the input data to drive the Soil and Water Assessment Tool (SWAT) model, keeping other input data unchanged to isolate the land use change impacts on surface runoff and water yield. The results showed that the forestland and grassland will expand along with the increase in water utilization ratio. The quick-response surface runoff would decrease significantly due to forest and grassland expansion, which may cause an overall decreasing trend of the water yield. This indicated the unreasonable allocation of water resources may exert negative impacts on the water yield even if the water utilization ratio is increased; therefore, water resources should be reasonably allocated for different land use demand, which is critical for sustainable development. The results of this study will be informative to decision makers for sustainable water resource and land management when facing land use change and an increasing demand for water resources in the Heihe River Basin.
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