The safety of groundwater resources in coastal areas is related to the sustainable development of the national economy and society. Seawater intrusion is a serious problem threatening the groundwater environment in coastal areas. Climate change, tidal effects and groundwater exploitation may destroy the balance between salt water and fresh water in coastal aquifers, leading to seawater intrusion. The threat of seawater intrusion has attracted close attention, especially in the coastal areas of northern China, and the accuracy and efficiency of seawater intrusion monitoring need to be improved. The aim of this study was to fill the blanks in seawater intrusion research in the coastal aquifer of the Daqing River Catchment, northeastern Liaodong Bay, China, and determine the extent and evolutionary characteristics of seawater intrusion in this area. In this study, historical chloride concentration data were used to trace the evolution of the salinization, and electrical resistivity tomography (ERT) was used to supplement the data in areas with limited hydrochemical data and to detect the saltwater/freshwater interface, especially in the area near the Xihai Sluice. The results show that seawater intrusion in the Daqing River Catchment is mainly caused by overexploitation of groundwater. Since 2012, strict controls have been placed on the groundwater exploitation rate, and the chloride concentration of 250 mg/L has receded year by year, with saltwater being significantly reduced by 2018. The Daqing River plays an important role in the saltwater distribution. The Xihai Sluice, located in the lower reaches of the Daqing River, intercepts and controls the seawater intrusion in a certain range by raising the level of fresh groundwater to intercept and control saltwater intrusion within a certain range. The research results also confirmed that a combination of geophysical and geochemical methods is of great value in studying seawater intrusion, especially in areas with limited available hydrochemical data. A monitoring network with ERT instruments and wells should be established to collect regular measurements of the electrical resistivity distribution, as well as the groundwater level and chemical composition.

The precise prediction of water inflow in tunnels is a key aspect of civil engineering. It is directly related to the progress of construction, the stability of caverns and the safety of construction personnel. Currently widely used calculation methods include the empirical formula method, the analytical method and the numerical simulation method. In situations where the geological conditions are complex and the boundary conditions are irregular, numerical simulation methods have clear advantages. However, there are still discussions about the rationality, accuracy and applicability of the definition of tunnel boundary conditions in numerical simulation methods. Based on the Groundwater Model System (GMS10.7) software, we investigate the feasibility of using the DRAIN module to describe tunnel boundaries and calculate water inflow. By comparing it with traditional empirical formulas, the feasibility of the method is verified, and the error is about 8%. In addition, this method is applied to predict the water inflow in the construction of an underground pumping station under complex geological conditions and the prediction is compared with the measured water inflow, and the error is about 20%. This article explains the physical meaning and the value method of the relevant parameters of the DRAIN module, providing basic support for the prediction of water inflow in tunnels.

Tunneling in structurally complex, tectonically active regions such as southwest China poses significant environmental risks to groundwater, especially in heterogeneous karst fault systems where conventional prediction methods often fail. This study innovatively coupled MODFLOW’s STREAM package (for simulating karst conduit networks) and DRAIN package (for tunnel inflow prediction) within a 3D groundwater model to assess hydrogeological impacts in complex mountainous terrain. The simulations show that an uncased tunnel lining causes significant groundwater changes under natural conditions, with predicted inflows reaching 34,736 m³/d. Conventional cement grouting (permeability: 1 × 10⁻⁵ cm/s; thickness: 10 m) mitigates the effects considerably and reduces the inflows in the tunnel sections by 27–97%. Microfine cement grouting (5 × 10⁻⁶ cm/s; 10 m thickness) further improves performance by achieving a 49–98% reduction in inflows and limiting the reduction in spring discharge to ≤13.28%. These results establish a valid theoretical framework for predicting groundwater impacts in heterogeneous terrain and demonstrate that targeted seepage control—particularly grouting with microfine cement—effectively protects groundwater-dependent ecosystems during infrastructure development.

Three-dimensional numerical simulation of subsurface flow dynamics in karst conduits at dam sites represents a pivotal component of hydrogeological research, essential for unraveling the intricate behavior of water movement within karstified terrains. This study introduces a novel approach for accounting for the presence of karst conduits and presents a comprehensive three-dimensional flow simulation for the dam site of the Jingxian Pumped Storage Hydropower Plant. This method reduces mesh division, simplifies calculations, and improves model convergence. The findings reveal that the numerical model adeptly captures the declining groundwater levels within the study area, with enhanced precision achieved through the utilization of COMSOL’s Line Mass Source feature. By representing leakage tunnel cylinders as edges, the model significantly improves meshing efficiency, circumventing the computational burden associated with the explicit resolution of intricate geometric details. In the absence of remedial measures, the simulation predicts that groundwater will preferentially drain downstream via two distinct leakage pathways at the dam’s base, presenting a potential threat to the structural integrity and operational stability of the project. To address this risk, the implementation of robust seepage control measures is imperative. Once these measures are established, the dam is expected to function as an effective hydraulic barrier, ensuring the long-term stability and operational efficacy of the hydropower plant.