With rapid urbanization, intensified agricultural activities, and industrialization, groundwater resources are increasingly threatened by pollution. Industrial wastewater discharge and the extensive use of agricultural fertilizers in particular, have had substantial impacts on groundwater quality. This study examines 18 groundwater samples collected from the main urban area of Yibin City to assess hydrochemical characteristics, spatial distribution, source attribution, water quality, and human health risks. Statistical analysis reveals significant exceedances in TDS, NO₃⁻, Mn, and As levels in groundwater, with elevated concentrations of B as well. Isotopic analysis identifies atmospheric rainfall as the primary recharge source for groundwater in the area, with water–rock interactions and limestone dissolution playing key roles in shaping its chemical composition. Applying the Entropy-Weighted Water Quality Index (EWQI) for a comprehensive water quality assessment, the study found that 94.44% of groundwater samples were rated as “good”, indicating relatively high overall water quality. Deterministic health risk assessments indicate that 72.22% of the groundwater samples have non-carcinogenic health risks below the threshold of 1, while 66.67% have carcinogenic health risks below 1.00 × 10⁻⁴. Monte Carlo simulations produced similar results, reinforcing the reliability of the health risk assessment. Although the study area’s groundwater quality is generally good, a significant human health risk persists, underscoring the need to ensure the safety of drinking and household water for local residents. This study provides a valuable reference for the rational management and remediation of groundwater resources.

Water inrush is one of the most serious phenomena threatening the safety of tunnel construction. The West Qinling 1# tunnel, as the major section of the Bailong River diversion project, traverses a complicated karst area and would be faced with a water inrush disaster. Based on geological and hydrogeological conditions, the Finite element subsurface flow system software is used to simulate and predict the development of the natural seepage field and dredging construction conditions of the seepage field on the West Qinling 1# tunnel area. The prediction results show that the groundwater level will drop up to 113.9 m under dredging construction conditions, with an impact radius of up to 11.5 km. Seepage field evolution and water influx were simulated under two conditions of construction plugging construction, respectively. The prediction results show that the groundwater level in the middle part of tunnel 1# is 112.68 m depth without blocking condition with an influence range of 10.5 km. The maximum water volume per unit length of the karst cave increases to 4.32 m³/d·m. In the plugging condition, the influencing scope does not significantly reduce, but the extent of the impact is greatly weakened. The groundwater level generally dropped at 10–25 m depth and the karst cave section unit length of the maximum water volume of 0.83 m³/d·m in the rainy season. The achievements of this study would provide a vital reference for the prevention of water inrush in karst tunnel construction.

Health risks associated with groundwater deterioration have become increasingly prominent worldwide. Accurate assessment of human health risks associated with groundwater is a critical component of groundwater development and utilization, particularly in large metropolitan areas with high water resource demands. In our study, 37 groundwater samples were collected from the main urban areas of Chongqing, the largest city in southwest China, to identify the groundwater driving factors and their associated human health risk. The primary hydrochemical facies in the study area is Ca–HCO₃. Groundwater hydrochemistry is primarily controlled by silicate weathering, carbonate (dolomite and calcite) dissolution, and anthropogenic activities such as industrial and agricultural activities. The hazard index (HI) caused by NO₃⁻ and NO₂⁻ was higher than the safety standard and exhibited potentially noncarcinogenic risk for children in the north and the west of the study area. The KDE-based Monte Carlo simulation method showed a high reliability in human health risk assessment, with all mean values of the original dataset falling within their corresponding 95% confidence intervals (CIs) of generated data. The achievement can provide valuable insights for groundwater risk mitigation and resource management in Chongqing’s main urban areas, as well as in other metropolitan regions worldwide.