Groundwater Evolution Mechanisms Driven by Ecological Water Replenishment in the Jialu River: Insights from Physical Simulation and Inverse Geochemical Modeling

High Resolution Image Download MS PowerPoint Slide Ecological water replenishment (EWR) is a critical measure for mitigating urban groundwater overdraft and improving aquatic environments. However, the transient hydrochemical evolution and water–rock interaction mechanisms driven by EWR infiltration remain poorly understood at the microscale. This study combined 2D sand-tank physical simulations with PHREEQC inverse geochemical modeling to investigate the spatiotemporal evolution of groundwater in the Zhengzhou section of the Jialu River. The results indicated that EWR significantly altered the redox conditions and solute composition of the aquifer. pH and DO fluctuated, whereas Eh and TDS generally decreased. Specifically, dissolved oxygen (DO) exhibited a biphasic response, whereas the oxidation–reduction potential (Eh) and total dissolved solids (TDS) declined. Major ions showed distinct phasic responses: Ca 2+ and Mg 2+ initially increased and then decreased, whereas Na + displayed an inverse trend, quantitatively suggesting that carbonate dissolution and forward cation exchange jointly controlled the hydrochemical evolution. Spatially, hydrochemical responses significantly attenuated with increasing distance from the infiltration source and burial depth. Mechanistic analysis and inverse modeling consistently indicated that groundwater evolution was controlled by the dissolution of carbonates and evaporites, accompanied by intense Na–Ca cation exchange. This study provides quantitative insights into the microscopic mechanisms of EWR-driven groundwater evolution and offers a scientific basis for groundwater quality regulation in water-receiving areas of the South-to-North Water Diversion Project.