Spatiotemporal dynamics of groundwater in Henan Province, Central China and their driving factors

Groundwater serves as an important resource for human sustenance and advancement. However, its depletion has emerged as a pressing concern in Central China accompanying with rapid urbanization. To counteract the acute water scarcity, China initiated an extensive project known as the South-to-North Water Diversion (SNWD), spanning over 1,400 km. Despite the project’s magnitude, the precise impacts of both the SNWD and climate variability on regional groundwater dynamics remain uncharted. In this study, we examine groundwater fluctuations and their influencing factors in Central China between 2003 and 2021. Our findings reveal a substantial decline of 5.8 % annually in the mean groundwater drought index (GWI) from 2003 to 2014, signifying a critical phase of groundwater depletion. This reduction was predominantly driven by the joint influence of rapid urban development (accounting for 37.9 %) and diminished precipitation (28.4 %), with a high explanatory power (R2 = 0.97). Contrastingly, from 2014 to 2021, enhanced precipitation and water transferred through the SNWD led to a 3.5 % yearly increase in GWI, highlighting a recent recovery of groundwater levels. These factors individually contributed 39.2 % and 7.0 % respectively towards this recovery (R2 = 0.91). Notably, precipitation emerged as the principal determinant shaping both long-term and short-term groundwater variations. Extreme precipitation events, in particular, were shown to swiftly and significantly recharge groundwater reserves. For instance, an extreme precipitation event in July 2021 elevated the GWI by 50 % compared to that of July 2020. Collectively, a blend of strategies including mitigating urbanization pressures, sustaining water diversions through the SNWD, and adapting to potential increases in extreme precipitation events due to global warming are proving instrumental in restoring groundwater resources in central China.