Preliminary assessment of hydraulic connectivity between river water and shallow groundwater and estimation of their transfer rate during dry season in the Shidi River, China

Understanding the relationship between surface water and groundwater is important for the integrated management of water resources in arid regions. In the present study, the connectivity of river water and shallow groundwater along the Shidi River, China is estimated using a connectivity index, as well as analyses of hydrochemistry and isotopic signature. The three approaches for hydraulic connectivity assessment were compared and discussed. An end member mixing analysis was performed to estimate the contribution ratios of local precipitation, river leakage and groundwater lateral inflow to the total groundwater recharge along the river. The results show that medium connectivity is identified in all reaches of the river (upstream, midstream and downstream). Water table depth and river channel sediments are the major factors responsible for the spatial variation of the hydraulic connectivity. The CI approach can be adopted to generate preliminary assessment results of hydraulic connectivity, while the physiochemical and isotopic approaches should be used as a tool for results validation and verification. Groundwater lateral inflow is the most important recharge source of groundwater along the river, while river leakage only accounts for 18.4-27.0 % of the total recharge. This study is meaningful in integrated water resources management in arid regions and the methods used in this study can be adopted by other scholars in similar studies.