Heihe River Basin is the second largest inland river basin in China, where water supply service in the upper reach has greater influence on the sustainable development of middle and lower reaches. This study analyzed the influence of land use/land cover change (LUCC) on the water supply service in the upper reach by carrying out scenario simulation. Firstly, we analyzed the LUCC and climate change in the upper reach during 1990–2005; then the water supply service, which was represented by the annual water yield, was estimated with the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. Thereafter three scenarios (precipitation change and LUCC change combined, LUCC change only, and precipitation change only) were established to analyze the impacts of LUCC and precipitation change on the water yield. The results show that the LUCC exerted great influence on water yield, while the impact of precipitation change is even more significant than that of LUCC. Although there are still some uncertainties, the results of this study can still provide valuable reference information for ecological conservation and water resource management in the upper reach of the Heihe River Basin.

Water yield is of great importance to the balance between supply and demand of water resources. The provision of freshwater for Dali is estimated and mapped in 1988, 1995, 2000, 2005 and 2008, using the Integrated Valuation of Environmental Services and Tradeoffs (InVEST) modeling toolset. The stability of water yield’s spatial variation is analyzed by a sorting method. The factors are explored which lead to the change in the relative water yield capacity. The yields at five points in time are compared, and the result of which shows a sharp fluctuation. The water yield curve is of a similar waveform as precipitation. An obvious and relatively stable spatial variation appears for water yield. The highest water yield areas are mainly located in the area where the elevation is high and both the elevation and the slope changes are large, and the main land uses are Shrub Land and High Coverage Grassland. The lowest areas are mainly in the eastern part of Erhai or the surrounding area. Precipitation, construction land expansion and the implementation of policy on land use are the three main factors which contribute to the change of the relative water yield capacity during 1988–2008 in Dali. In the study area, the water yield appears highly sensitive to the change in precipitation. The elasticity coefficient is calculated to illustrate the sensitivity of the water yield to the precipitation. When the elasticity index is larger, the risk of natural disaster will be higher.