Simulation and classification of the impacts of projected climate change on flow regimes in the arid Hexi Corridor of Northwest China

Traditional assessment approaches of climate change on flow regimes usually focus on flow magnitude and cannot capture the overall variation of flow regimes (e.g., variability, frequency, duration, timing, and rating). The Hexi Corridor, which is a typical arid and semiarid region in Northwest China, was selected as the study area. Streamflows were simulated by an integrated water system model in a historical period (1985-2005) and three future periods (2030s, 2050s, and 2070s). Twenty-nine global climate models were picked from the Coupled Model Intercomparison Project Phase 5 based on projection performance, and the high (RCP85) and intermediate (RCP45) ranges of Representative Concentration Pathways were selected for future scenario analysis. All the streamflows were characterized in detail by flow regime metrics, including the magnitude, variability, and frequency of the overall flow events. The regional impacts of climate change were assessed and clustered into several similar spatial patterns. Results showed that the projected climate change would sensibly increase the magnitudes of average and low flows (75th percentile), as well as the frequencies of low and high flows (25th percentile), but decrease the flow variability. By contrast, it would not sensibly change the magnitude of high-flow events. The flow regime variations of all scenarios and periods were clustered into three robust classes (highly, moderately, and slightly impacted classes) in the entire region. The flow regimes would be highly and moderately impacted in the middle stream and downstream with large-sized and semidesert catchments but slightly impacted in the upper and middle streams with small-sized and montane vegetation catchments. The impacted classes will sensibly vary at most stations in different future periods because of the spatial differences of climate change. This study would provide scientific support to implement the integrated adaptive water resource management for climate change at regional scales in the arid Hexi Corridor.