National-scale modelling analysis of drought characteristics and propagation under anthropogenic impacts in largest basins of China

Understanding the drought evolution under changing environment is crucial to sustainable water management, especially for China where there are increasing anthropogenic activities. However, the extent to which human intervention affects the drought regime across China remains unclear. Here, we employ a national-scale land surface-hydrological model with representations of human water management and dynamic land use to investigate the impact of human activities on the drought regime across the largest river basins of China. We first identify the meteorological droughts and hydrological droughts of these basins using Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI), respectively. Then, two controlled simulation experiments, namely the human altered scenario and the natural scenario, are designed to analyze the human impact on the frequency, severity, duration, recovery time, and recovery rate of hydrologic droughts, and the relationship between meteorological and hydrological droughts. Results indicate that the SSI variations under human impacts can be well simulated by the model, with a correlation coefficient ranging from 0.78 to 0.93. The basins in northern China generally sees a decrease in the number of drought events but an increase in the severity, duration, recovery time and recovery rate of hydrological droughts, and the average propagation time from meteorological droughts to hydrological droughts under the human impacts. For basins in southern China, the impact of human activities on the drought regime is similar to that of northern basins but to a lesser extent, possibly due to the larger streamflow in the south which diminishes the impact of human activities.