Human activities reshape the drought regime in the Yangtze River Basin: a land surface-hydrological modelling analysis with representations of dam operation and human water use

Understanding the evolution of drought is of great significance to water resources management especially for the Yangtze River Basin that is home to 400 million people. However, this has been a scientific challenge due to the lack of a modelling framework to accurately reconstruct the drought regime and identify its driving factors in a comprehensive way. Here, we employ a coupled land surface-hydrologic model with explicit parameterizations of anthropogenic activities to investigate the drought characteristics of the Yangtze River Basin under climate change and human activities. Two numerical simulation experiments were first set up to reconstruct the long-term terrestrial water storage (TWS) variations of the Yangtze River Basin with and without human activities, respectively, and a water storage deficit index (WSDI) is then introduced to quantify the impact of human activities on the drought regime in the Yangtze River Basin. The results show that our TWS simulations taking account of human activities are in good agreement with the GRACE data for the Yangtze River Basin in both space and time. Reservoirs play a significant role in the TWS variations during the past decades. The terrestrial water storage drought is exacerbated by the human water withdrawal before 2009, and alleviated by the reservoirs after 2009. The correlations between Standardized Precipitation Index (SPI) and WSDI with taking account of human activities are smaller than that without taking account of human activities. The propagation time from meteorological drought to terrestrial water storage drought is shortened by the human water withdrawal and extended by the reservoirs. By reconstructing the terrestrial water storage anomaly (TWSA) in the Yangtze River Basin from 1981 to 2018, our findings could reveal the impact of human activities on terrestrial water storage anomaly and the attribution analysis of drought characteristics, providing support for the efficient utilization of water resources in the basin.