Groundwater Overexploitation and Water Quality Degradation in a Typical Inland River Basin of the Agro‐Pastoral Ecotone in Northern China

ABSTRACT Groundwater is the primary freshwater source in semiarid regions, yet intensive overextraction and water quality deterioration increasingly threaten agricultural production and ecological sustainability. The Angulinao Endorheic Basin (AEB) in northern China has experienced rapid irrigation expansion, wetland degradation, and severe lake desiccation over recent decades. In this study, we integrated long‐term climate and hydrology records, land‐use dynamics, hydrochemical data, and regional groundwater resource balance calculations to quantify groundwater availability, quality evolution, and supply–demand relationships. Results indicate that mean annual groundwater recharge is approximately 1.04 × 10 8 m 3 , whereas sustainable groundwater exploitation is limited to 4.16 × 10 7 m 3 year −1 . Projections suggest that by 2030, groundwater demand will exceed sustainable supply by 2.86 × 10 6 m 3 year −1 in normal hydrological years and up to 9.83 × 10 6 m 3 year −1 in dry years. Groundwater quality exhibits pronounced spatial heterogeneity: 55% of irrigated areas exceed nitrate (NO 3 − ) standards and 17% exceed fluoride (F − ) thresholds. Discharge zones are characterized by elevated total dissolved solids (TDS), NO 3 − , Fe, and Mn, reflecting combined geological controls and anthropogenic inputs, whereas elevated F − concentrations are primarily associated with strong evaporation processes. These findings reveal critical risks associated with continued groundwater overextraction and quality degradation and emphasize the urgent need for integrated groundwater management strategies to ensure long‐term water security and ecosystem resilience in semiarid endorheic basins.