Characterizing the drought events in Yangtze River basin via the insight view of its sub-basins water storage variations

Abstract

Yangtze River Basin (YRB) is the most important strategic base of water resources in China, which has the characteristics of complex terrain and unbalanced water distribution in spatial and temporal domain. Drought events have occurred frequently in this basin due to the influence of global climate change and human activities. In this context, it is critical to formulate drought policies based on the characteristics of drought events in different sub-basins. Based on the latest HUST-Grace2020 model released by Huazhong University of Science and Technology, we calculate the terrestrial water storage anomaly (TWSAs) in YRB during January 2003 to July 2016, and combine water storage deficit index (WSDI) with a modified run theory to extract precisely drought events in terms of sub-basins. On this basis, the characteristics of drought events are identified in different sub-basins and different seasons. Subsequently, the links between drought events and topography as well as climate factors are explored in the YRB. The results indicate that: (1) Soil moisture storage anomaly (SMSA) is the uppermost component (41%) of TWSA but the largest contributor (59%) to TWSA trend is groundwater storage anomaly (GWSA). Precipitation is the main factor affecting the composition and trend of TWSC. (2) Eight drought events (one severe level, four moderate level and three mild level) are extracted across YRB and the most severe event can be monitored in each sub-basin which begins from May 2006 to August 2007. (3) The frequency of drought events is higher in the lower region of YRB, but serious drought events are more likely to occur in the source region of YRB. (4) Droughts are more frequent in summer and winter, while severe and extreme situations mainly occur in autumn. (5) Drought severity in the YRB is positively correlated with topography, and drought events are influenced by El Niño, especially in the downstream YRB. This study sheds a theoretical basis for drought early warning of different levels in YRB across the various sub-basins.