Drivers and characteristics of groundwater drought under human interventions in arid and semiarid areas of China

Groundwater drought is a significant type of hydrological drought and manifests as abnormal groundwater shortages as a result of prolonged drought propagation. This type of drought typically exhibits a longer duration than meteorological and agricultural droughts and can be severe in arid and semiarid regions. Human activities like pumping can further complicate the detection and characterization of groundwater drought. This study used long-term groundwater level monitoring data from 1991 to 2018 for the Yinchuan region to calculate a standardized groundwater level index and applied hierarchical clustering and the run theory to assess groundwater drought. Additionally, the relationship between groundwater and meteorological/agricultural droughts were investigated, and the factors driving groundwater drought were analyzed. Based on the results, regional groundwater droughts are becoming increasingly severe. In this study, there are regional differences in the trends of the standardized groundwater level index, which could be divided into three clusters (C1, C2, and C3). Wells in C2 are located near the Yellow River and show a shorter groundwater drought duration (mean value: 3.16 months), which means that these wells can recover from drought more quickly than those in the other clusters. Meteorological and agricultural droughts show a weak correlation with groundwater drought (with average cross-correlation coefficients of 0.03 and 0.25, respectively), and human activities most likely were the causes of regional groundwater droughts. Thus, a comprehensive understanding of regional groundwater droughts should consider human activities, in addition to the geographical location and natural environments. This research establishes a scientific foundation for managing regional groundwater resources and offers novel insights for future groundwater drought studies in the context of human activities.