Continuous drainage during tunnel construction significantly alters groundwater circulation processes in karst regions. To elucidate the dynamic mechanisms by which tunnel drainage influences water exchange between the karst matrix and conduits, this study employs MODFLOW-CFPv2 to construct a coupled matrix–conduit groundwater flow model for a deep tunnel in a typical karst area of Panzhou City, southwest China. The model performed well in both borehole groundwater-level calibration and independent spring discharge evaluation, with Pearson correlation coefficients of 0.98 and 0.89, respectively. Key findings reveal: (1) Tunnel excavation reverses flow direction at the matrix–conduit interface within 30 days, establishing a new dynamic equilibrium after approximately 390 days; (2) Water exchange exhibits phased nonlinear evolution, with the total exchange rate decreasing by an average of approximately 3000 m3 day−1 after stabilization, and a more pronounced suppression of conduit-to-matrix recharge; (3) Under the assumed post-support reduction in tunnel-aquifer hydraulic connectivity, groundwater levels remained 1.5–2.0 m below the natural baseline during the simulated recovery period, while the number of active CFPv2 conduit nodes with effective matrix–conduit exchange flux decreased by 3–6, corresponding to approximately 5
The aim of this article is to provide a methodology for characterising and quantifying water origin and transfer in karst aquifers during storm events, using physicochemical signatures from high-frequency records of variables describing the transfer of dissolved and suspended particulate matter. Descriptors of the physicochemical time series is computed, including electrical conductivity (EC), turbidity, and water fluorescence. The study site is the Fontaine de Nîmes observatory (southern France), which is located in an urban Mediterranean environment. On the basis of 27 major storm events, a seasonal storm event typology based on hydrological conditions dedicated to Mediterranean regions is proposed. A cross-analysis to identify the origin of water turbidity by means of information on all physicochemical variables is carried out: pre-event and event water contributions (EC), intensity of sediment mobilisation (first derivative of discharge), unsaturated zone contribution, and wastewater origin (water fluorescence). A quantitative approach using end-member mixing analysis (EMMA) made it possible to differentiate the contributions of the karst compartments, showing the predominance of water from the saturated zone in spring flows, even during the largest events. The main results show that storm events with the highest turbidity peaks mobilise pre-event and event waters, which are characterised by relatively “young” residence time during high water levels period. Storm events with lower turbidity are characterised by pre-event waters with seasonally variable residence time. Overall, this paper highlights the benefit of high-resolution multiparameter monitoring to better characterise the rapid dynamics of dissolved and particulate transfers in karst aquifers.
Calco-carbonic reactive transport controls the dissolution of limestone by carbonic acid, a key process shaping the hydraulic and geochemical evolution of carbonate aquifers. Quantitative understanding of the coupling between flow, transport, and chemical reactions is essential for predicting karstification under variable hydraulic gradients, CO_2 partial pressures, and pH. To support model validation, laboratory experiments were conducted in a 1 m ^2 vertical karst-fracture analog with variable aperture, representing a simplified hydrogeologic fracture domain. Numerical simulations reproduced these experiments under controlled discharge, CO_2 concentration, and acidity. The coupled reactive transport models capture feedbacks between forced convection, diffusion, and density variations, linking reactive interface dynamics with evolving flow fields. Simulated and measured calcium and carbonate ion concentrations showed good agreement, indicating that diffusive transport at the water–limestone interface primarily limited dissolution. Insights from the combined modeling and experimental framework refine laboratory-scale design, improve interpretation of dissolution kinetics, and strengthen the basis for upscaling to field-scale carbonate aquifers. The results enhance prediction of permeability evolution, flow-path development, and CO_2 - H_2O -rock interactions in karst systems.
Confined aquifers are considered to be protected from surface contamination, yet intensive abstraction and long-term land-use pressures may alter their quality, especially in coastal areas. This study characterises the hydrochemistry of the multilayered confined aquifer system of the lower Friulian Plain (NE Italy), where groundwater is extensively exploited and locally affected by anthropogenic stressors. The study combines hydrochemical data from 1996 to 2025 from the monitoring activity of Regional Environmental Protection Agency of Friuli Venezia Giulia (ARPA FVG) and new samples collected in 2024–2025, compiling 1210 samples from 103 wells. The aim is to determine how recharge sources, residence time, and human activities control groundwater quality. Hydrochemical families were identified using major ions, redox-sensitive species, organic micropollutants, stable oxygen isotopes, and multivariate statistics. Three groundwater families were recognised: submodern waters, with hypoxic conditions, low to absent contaminant load and likely associated with recharge dating back to the late Würmian glacial period; modern-pristine waters, which are characterised by oxidising conditions, are SO42−-rich, and show low to absent NO3− and pesticide concentrations; and modern-impacted waters, which are similar to the latter but display elevated NO3− concentrations, lower pH values, and detectable anthropogenic contaminants. Long-term trends indicate that although NO3− concentrations are overall stable or slightly decreasing in shallow aquifers, slowly increasing trends occur in deeper wells and near the margins of the NO3− plume, suggesting downward and lateral migration of impacted modern groundwater. Cl− concentrations show no increasing trends in coastal wells, indicating no evidence of active seawater intrusion.
Clogging of groundwater abstraction wells typically occurs when dissolved Fe and Mn in groundwater precipitate on well components, causing yields to decline. In Finland, well clogging is severe, as the soil is high in Fe and Mn, and a lack of oxygen is typical in clay-covered Quaternary sedimentary aquifers. A new approach to well rehabilitation involving a combination of mechanical and chemical treatment was applied in four groundwater abstraction wells located in unconfined, postglacial, Quaternary sedimentary deposits in Finland. According to X-ray fluorescence (XRF) analyses, the clogging precipitates were composed of Fe2O3, SiO2, MnO and P2O5. Both mechanical and chemical rehabilitation significantly improved the yields (68−6692
