Impacts of Climate and Land Use/Cover Change on Streamflow Using SWAT and a Separation Method for the Xiying River Basin in Northwestern China

A better understanding of the effects of climate change and land use/cover change (LUCC) on streamflow promotes the long-term water planning and management in the arid regions of northwestern China. In this paper, the Soil and Water Assessment Tool (SWAT) and a separation approach were used to evaluate and separate the effects of climate change and LUCC on streamflow in the Xiying River basin. The SWAT model was calibrated by the hydro-meteorological data from 1980–1989 to obtain the optimum parameters, which were validated by the subsequent application to the period between 1990–2008. Moreover, streamflow under several scenarios with different climate change and land use conditions in 1990–2008 and 2010–2069 were further investigated. Results indicate that, in the period of 1990–2008, the streamflow was dominated by climate change (i.e., changes in precipitation and temperature), which led to a 102.8% increase in the mean annual streamflow, whereas LUCC produced a decrease of 2.8%. Furthermore, in the future period of 2010–2039, the mean annual streamflow will decrease by 5.4% and 4.5% compared with the data of 1961–1990 under scenarios A2 and B2, respectively, while it will decrease by 21.2% and 16.9% in the period of 2040–2069, respectively.