Daily‐Resolution Modelling of Surface Water–Groundwater Interaction Under Multiple Human Activities in a Riparian Zone

ABSTRACT Surface water–groundwater interaction (SGI) is a crucial process for the water cycle, and its remarkable heterogeneity is increasingly shaped by intensifying anthropogenic influences. Understanding the impact of human activities on the SGI is crucial for improving the accuracy of hydrological forecasting and achieving sustainable water resource management. This study chose the riparian zone of the South Canal in the Haihe Basin, China as the research area. The SkyCoMuS groundwater model was chosen to simulate water cycle processes under different human activities, including ecological water replenishment (EWR), irrigation policy adjustments, and pumping. Four simulated scenarios were designed, and the flux and direction of SGI were analysed to illuminate the impacts of human activities. The results indicate that irrigation policy adjustments are a crucial factor influencing groundwater storage and SGI dynamics in the study area, leading to a decrease in groundwater pumping volume ranging from 6.1% to 33.8%. Overexploitation of the confined aquifer increased the hydraulic gradient between aquifers, which in turn indirectly accelerated the decline of phreatic water storage through leakage. Accounting for the prioritisation of pumping reductions among multiple aquifers could potentially improve the recovery efficiency. The SGI generated daily‐scale responses to the EWR, with the direction and flux of the SGI varying with fluctuations in EWR intensity. The EWR for the South Canal increased the phreatic water recharge by 9.4%, and the average distance of the phreatic water table response to the EWR was approximately 3 km. Irrigation water source substitution is more effective than water‐saving measures in restoring groundwater storage and enhancing SGI intensity because the infiltration of external water sources increases net groundwater recharge. When EWR is combined with irrigation policy adjustments and pumping controls, the combined effects of reduced pumping volume and increased recharge, which include streamflow infiltration and irrigation return flow, are more likely to achieve the restoration of groundwater storage and baseflow. These results provide valuable guidance for water resource management measures in the South Canal basin and other water‐scarce regions.