Water resource spatiotemporal pattern evaluation of the upstream Yangtze River corresponding to climate changes

The hydrological cycle is sensitive to the driving forces of climate change. Thus, impact assessment of climate change on water resources from the past to the present is of grave concern for basin management. In this study, water resource spatiotemporal patterns exposed to IPCC scenarios A2 and B2 in the upstream Yangtze River are assessed. Statistically downscaled precipitation and temperature are analyzed. Rainfall-runoff processes are modeled using a distributed hydrological model. Results show that the historical downscaled precipitation and temperature are consistent with observations. Mean air temperature increased for both scenarios. Precipitation generally declined over the region. Runoff is predicted to decrease in most rivers, especially in the wet season, and the variation of hydrographs is obvious. An increase in temperature likely caused the reduction of precipitation leading to the consequent rise of evapotranspiration and decline of surface water and groundwater recharge. Generally, surface water and ground water recharge declined faster in the A2 scenario than B2. Water resources will be in a considerable heterogeneous pattern driven by climate changes. Precipitation, surface water generation, and groundwater recharge share identical spatiotemporal patterns but are predicted to show larger spatial variation in future decades. B2 shows a larger future spatial variation, which may add risks for local droughts and floods. This paper emphasizes the evolution of spatiotemporal variations of water resources from 1999 to 2099 associated with discussions on implications and uncertainties in the upstream Yangtze River region.