Recharge of Shallow Groundwater in Alluvial Aquifers in the Humid Region of Central China: A Case Study of the Zishui Plain in the Dongting Lake Area

The Dongting Basin in central China has experienced increasing pressure on water resources due to intensified industrial and agricultural activities and increasingly frequent droughts. Therefore, reliable estimates of groundwater recharge are essential for evaluating the sustainability of groundwater resources in this region. An integrated approach combining the water table fluctuation (WTF), groundwater age, and chloride mass balance (CMB) was applied to estimate groundwater recharge in the Quaternary aquifer of the Zishui Plain, a sub-basin of the Dongting Basin. The mean recharge values derived from these methods were 268.2, 226.2, and 167.03 mm/year, respectively. The corresponding mean R/P ratios were 19.4%, 16.5%, and 12.2%. Differences between the recharge estimates reflect methodological differences among the three approaches and suggest that lithology, river seepage, and human activities contribute to the observed spatial variability in groundwater recharge. The WTF method generally produced the highest recharge estimates, whereas the CMB and groundwater age methods tended to provide lower estimates because of their respective methodological limitations. The integrated application of these methods may provide a more comprehensive assessment of groundwater recharge and may serve as a useful reference for groundwater management in the Dongting Basin.