Future water resource changes in the Yangtze River Basin under the influences of climate change and human activities

The Yangtze River Basin is the largest basin in China, covering an area of 1.8 million square kilometers and possessing very abundant water resources. The water resources in this basin play a crucial role in the ecological environment and socio-economic development. Understanding the future hydrological changes in the Yangtze River Basin is crucial for China's water resource allocation and planning. However, many studies have indicated that, under the influence of complex climate change and intense human activities, the hydrological cycle in the Yangtze River Basin has become more complex. This research utilized a distributed hydrological model to investigate the hydrological changes in the Yangtze River Basin during the historical period (1961-2019) and the future period (2021-2100). Historical observed data and CMIP6 data are used to drive the model. Meanwhile, machine learning methods are applied to process the output results of the hydrological model, simulating the impact of human activities within the corresponding regions. The results indicate that, during the historical period, machine learning methods could enhance the simulation accuracy of areas which are significantly influenced by human activities. The historical data show that, despite an upward trend in precipitation in the historical period, the runoff at the main hydrological stations of the Yangtze River mainstream continues to decline due to increasing evapotranspiration. Under future conditions, the total runoff in the Yangtze River Basin will further decrease compared with historical runoff, intensifying water resource risks within the basin and posing new challenges for water resource management.