Response of total runoff to climate change in arid Northwest China

Abstract:

Abstract：Water availability is of primary importance to domestic water use and agricultural production in arid Northwest China. Approximately 80% of total water supply comes from the surface water that is contributed mostly by snow and glacier meltwater in Xinjiang Uygur Autonomous Region in 2016. Therefore, improving the understanding of spatiotemporal variability in runoff and its response to future climate change is of great significance to water resources allocation and management over this region. A distributed hydrological model, the Community Water Model (CWatM) was used in this study, with a glacier melt module incorporated. The simulated river discharge using input data of a coarse resolution (e.g., ~5 arcmin or ~9 km at the equator) does not seem unreliable. We coupled CWatM with a glacier-snow module, refined the process of water holding and refreezing, and differentiated the precipitation phase using the double temperature threshold method. The improved modeling framework is termed as the CWatM-Glacier and Snow (CWatM-GS). In addition, we increased the spatial resolution of input data (e.g., land cover, soil, topography, lakes, reservoirs, GW, water demand, and routing) up to ~30 arcsec (~ 1 km at the equator) to improve the performance of the model. Results show that the daily simulated river discharge from CWatM-GS has largely improved compared with that from the original model in Northwest China during 2000–2016. Last, we projected total runoff in Northwest China during 2020–2050, derived its spatiotemporal dynamics under different climate change scenarios (i.e., RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5), and explored the primary drivers behind the variability (e.g., temperature rising or changes in precipitation). This study provides implications for decision making in flood hazard mitigation and water resources management in Northwest China, exemplifying quantification of water availability and its response to future climate in arid regions globally.

Key words: CWatM-GS; total runoff; glacier; future projections