Long-term evolution patterns of groundwater depth and lagged response to precipitation in a complex aquifer system: Insights from Huaibei Region, China

Abstract This study examines the spatiotemporal variability of shallow groundwater in the Huaibei Region, Anhui Province, with a focus on factors such as precipitation, human extraction, and historical overexploitation. Multiple time-series analyses, including the Sen and Mann–Kendall trend tests and Morlet wavelet analysis, are employed to assess groundwater trends and their relationship with precipitation, aiming to support sustainable water resource management. Findings reveal a general trend of “initial increase followed by decrease” in groundwater depth across the region, with varying rates of decline from north to south. A dominant 35-year cycle in groundwater depth is identified, with an oscillation center in the 1990s to early 2000s. Wavelet coherence analysis reveals a significant periodic resonance between groundwater depth and precipitation, with lag effects exhibiting spatial variations. The study offers insights into the temporal characteristics of groundwater trends and the increasing lag effects of precipitation on groundwater levels from north to south, geographically. This study systematically reveals the temporal scale characteristics of groundwater evolution and the spatial variability of the lag effect of precipitation, providing important references for the scientific management of shallow groundwater in overexploited areas and supporting the development of regional water resource management strategies. The findings offer direct decision-making support for water resource authorities, planning agencies, agricultural sectors, and environmental protection departments in Anhui Province and the Huaibei Region, while also holding practical value for broader application in other groundwater overexploitation zones across East China and the entire country.