Continuous monitoring and sustainable management of industrial groundwater: A three-decade hydrological analysis in a riverbank alluvial plain, Japan

Study region: Tonami Plain aquifer system along the Sho River, central Japan, a typical riverbank alluvial plain with sand-gravel deposits and intensive industrial groundwater use. Study focus: This study quantifies the impacts of industrial groundwater extraction (≈50% of total regional use) on aquifer dynamics and surface water-groundwater interactions, using a 33-year (1991–2023) dataset combined with hydrological diagnostics and Random Forest-SHAP analysis. It aims to identify pumping-driven changes in flow paths, recharge processes and hydrochemical stability, and propose sustainable groundwater management guidance for the region. New hydrological insights for the region: Precipitation contributes 34.5% (0.76 m/yr) to groundwater recharge, including 8.5% direct infiltration and 26% mountainous lateral inflow. Industrial pumping causes up to 5 m drawdown in deep aquifers, exerts negative impact on downstream groundwater and river discharge, and induces hydraulic gradient reversals that trigger shallow-to-deep inter-aquifer leakage. This leakage reduces shallow aquifer recharge and may drive nitrate migration to deep aquifers, while the dominant Ca-HCO₃ hydrochemical facies remains stable. Industrial Group IV pumping nears sustainable recharge limits, and Group III has aquifer recovery potential with targeted management. The refined water management and an upstream–downstream integrated framework is proposed, with replicable value for global riverbank alluvial plain groundwater management under climate and anthropogenic pressures.