Search Results (1,976)

Machine learning (ML) has evolved into an indispensable tool for uncovering hidden patterns and deducing correlations. Currently, ML is having a profound impact on the field of groundwater resources and environment research by enhancing predictive accuracy and optimizing management strategies. In this study, we conducted a bibliometric review using CiteSpace and a global-scale analysis of ML methods applied to groundwater resources and quality based on 1326 records. The findings suggest that ML applications in groundwater resources and water environment research are still in their infancy compared with other environmental science fields. This paper then provides a systematic summary of the specific applications of machine learning methodologies within groundwater research, focusing primarily on the prediction of groundwater levels and water quality, along with the extraction of feature importance. Furthermore, a comparison was made of the pros and cons of several prevalent ML techniques used in groundwater level and water quality studies, with an emphasis on the significance of aligning data with models during the application of ML. Finally, the challenges encountered by ML tools in groundwater research were addressed, along with opportunities for the future. The significant potential of employing ML methodologies in groundwater is proposed to make the invisible visible. Full article

Numerical simulation is an effective method for studying groundwater flow and heat transfer in geothermal energy projects. Describing the characteristics of thermal plumes is important for operational planning of geothermal energy projects. In contrast to shallow geothermal system, the injection temperature differs significantly from the natural temperature of thermal reservoir in high-temperature geothermal projects, which leads to changes in fluid density and dynamics viscosity. The purpose of this paper is to investigate the impacts of temperature-induced changes in density and dynamics viscosity on simulation. The Enhanced Geothermal System (EGS) in North Jiangsu Basin, China, is taken as a case project. Based on the theory of groundwater flow and heat transfer in porous-fracture dual medium, a numerical model of EGS is established to predict the thermal performance. The density and the dynamics viscosity in the model were set as either constant or temperature-dependent to simulate the hydraulic head and temperature of the production well. The influence of temperature-induced changes in density and dynamics viscosity on the simulation was quantitatively studied. The results show that temperature-induced change in dynamics viscosity has a greater impact on the simulation, with deviation in hydraulic head exceeding 20% if the dynamics viscosity is assumed constant. The temperature-dependent variation in viscosity should be incorporated into the simulation process to improve the accuracy of the calculation. In practice, EGS projects should maximize the temperature differential between produced and injected water. The increased viscosity of lower-temperature circulation water extends its residence time within the system, thereby facilitating more thorough heat extraction. This research enhances our understanding of the role of the temperature in groundwater flow and heat transfer within EGS. Full article

This article presents the results of a field study conducted in 2022 on groundwater outflows located at the edge of the Kashubian Lake District and the Reda-Łeba Proglacial Stream Valley in northern Poland. The recharge of numerous springs was found to occur from the first aquifer, locally supported by a deeper aquifer connected to the first one near the bowl of Lubowidzkie Lake. Groundwater drainage occurs by gravity. It is relatively abundant for young glacial areas and averages 82 dm³·s⁻¹, making the springs capable of acting as a drinking water reservoir. This assessment is based on major ions and nutrients only; microbiological and trace-organic/metal analyses are required before any drinking-water designation. Spring water is important in the lake’s supply, accounting for 18.0% of the total inflow to the basin. The hydrochemical characteristics of these waters keep the lake in ecological balance. The waters from the springs are characterized by little variation in chemical composition, with the Ca-HCO₃ hydrochemical type. They represent young infiltration waters associated with direct recharge from precipitation (the average age of the water is 60 years). Currently, low nitrate and chloride suggest limited agricultural and urban influence, but phosphate levels and observed human activities warrant caution. Forest management is gradually developing in its catchment, which may result in a reduction of the spring yield and a deterioration of their quality in the future. This may result in a disturbance of the hydrological balance of structures hydraulically connected to spring recharge and to groundwater inflow (river, lake). Although the springs studied are local hydrological phenomena, their functioning and the need for protection are closely linked to global challenges in the field of sustainable development. This primarily concerns the protection of groundwater-dependent ecosystems and, more broadly, water security and increased resilience to climate change. Full article

Underground concrete structures are exposed to a multi-ion groundwater and seepage–leakage coupling environment for a long time, and it is difficult to observe visually, which makes it difficult to accurately characterize important boundary conditions and defect states, resulting in significant time-varying and spatially differing characteristics of the concrete deterioration process. Therefore, its durability assessment and life prediction are significantly different from those of above-ground structures. Aiming at the complex prediction problem of limited service information of underground concrete, this paper summarizes and combs the evolution process of underground concrete life prediction methods, and puts forward the evolution process of five generation prediction frameworks: from a deterministic mechanism model (Gen-1) to a multi-physical field coupling model (Gen-2), a probabilistic reliability framework (Gen-3), a data-driven and physical information fusion method (Gen-4) and then to a digital twin framework for online update and system integration (Gen-5). Differently from the traditional review by model category, this paper reveals the internal logic of life prediction from single life point values to time-varying risk assessment from the perspective of the transformation of prediction targets and problem structures. Based on the comparison of typical underground service environments, it is further shown that the key constraints of prediction ability are usually derived from insufficient observability and limited parameter identifiability, as well as model structure errors introduced by deterioration mechanism switching and local defects, rather than physical model complexity. On this basis, this paper proposes the selection idea of life prediction methods for different underground scenes, emphasizing measurable characterization, hierarchical verification and hierarchical calculation as the core, and effectively connecting the mechanism model, uncertainty analysis, data update and operation and maintenance decisions. In this paper, the life prediction of underground concrete is redefined as a dynamic evaluation process embedded in the whole life management of infrastructure, which provides a theoretical framework and research direction for the construction of a reliable and deployable life prediction system of underground concrete. Full article

Numerical simulations quantify the transient impacts of implementing green infrastructure (GI) grass swales on unconfined aquifer storage and groundwater-surface water interactions around the Red Butte Creek (RBC) of Utah, USA. The Red Butte Creek Watershed (RBCW) transitions from undeveloped mountainous National Forest land to downstream urbanized areas within Salt Lake Valley (SLV). This reconnaissance-level study demonstrates that increasing stormwater infiltration in urbanized areas during the rainy months (April-June) can, until at least the subsequent March, (a) enhance aquifer recharge and support sustainable groundwater yields; and (b) improve surface water availability. Simulations predict hydrologic impacts of aquifer recharge resulting from hypothetical grass-swale implementation within a 704-acre area located around RBC. The employed model, HyperRBC, is an adaptation of a United States Geological Survey (USGS) transient numerical flow, MODFLOW, model implementation for SLV. Adaptations involved (a) uniformly refined horizontal discretization of seven aquifer layers within a sub-area encompassing parts of RBCW and an adjacent watershed; (b) updated input data; and (c) MODFLOW’s Streamflow-Routing (SFR) package to simulate RBC flow and aquifer-stream seepage. Model predictions indicated that by the end of next March: (a) about 3% of the GI-induced recharge would remain within the unconfined aquifer in the HyperRBC area; (b) 66.6% of the recharge would flow northward into the downgradient continuation of the unconfined aquifer; and (c) 30.3% would discharge to nearby stream and river. In summary, predicted hydrologic changes due to the short-term GI-induced recharge highlight increased groundwater availability within and outside the study area for at least the subsequent 12 months, including high-water-demand summer. These findings show the importance of GI in interim environmental management and in enhancing the effective use of water resources. Full article

The Yellow River Delta, a young alluvial plain in China, is experiencing severe land subsidence that threatens its ecological security and sustainable development. However, the driving mechanisms of this subsidence exhibit strong spatial heterogeneity, which traditional global models fail to capture. This study integrates high-precision subsidence measurements from Sentinel-1A imagery and SBAS-InSAR technology (2017–2023) with multi-source environmental factors (topography, geology, land use, precipitation) to propose a Spatially Adaptive Ensemble Learning Model with feature selection (SA-GSE). The model concatenates predictions from base learners (CatBoost, XGBoost, Random Forest) with spatial features (e.g., distance to salt pans, local topographic variance) to form meta-features, which are then input into a multilayer perceptron meta-learner. Through 5-fold spatial cross-validation, SA-GSE learns spatially dynamic base-model weights, implicitly adapting to regional variations in subsidence drivers. The model achieves an R² of 0.7810 and RMSE of 40.55 mm/yr on the test set, outperforming individual base models and ordinary stacking. Residual spatial autocorrelation is substantially reduced, with SA-GSE yielding the lowest Moran’s I (0.0334, p = 0.206) among all evaluated models, confirming effective capture of spatial heterogeneity. Driving force analysis reveals that distance to salt pans is the most important predictor (permutation importance: 0.4456), underscoring the dominant role of brine extraction-induced aquifer compaction. Lagged precipitation importance (0.3191) exceeds that of current precipitation (0.2453), indicating a recharge lag effect. SHAP interaction analysis uncovers a nonlinear “precipitation decoupling” mechanism in salt pan areas, where high precipitation paradoxically exacerbates subsidence. The resultant map of predicted subsidence rates highlights elevated rate zones in the northern salt pans and along the Guangli River. While the map does not represent a full risk assessment—as it does not include exposure or vulnerability—it provides a spatially explicit estimate of hazard likelihood. This ensemble framework yields novel perspectives on subsidence drivers in heterogeneous regions and can support land subsidence prevention and groundwater management planning. Full article

Given the challenges posed by high groundwater levels, thick sand layers, and strong permeability in water-rich sandy strata, cut-off walls often fail to fully isolate the hydraulic connection between the inside and outside of a foundation pit. As a result, dewatering inside the pit—especially from confined aquifers—can cause significant external groundwater drawdown and subsequent ground settlement. Using a deep excavation conducted in Xiamen as a case study, this study developed a two-dimensional hydro-mechanical coupled finite element model to systematically investigate the effects of various dewatering scenarios and soil permeability coefficients on surface settlement around the pit, and to reveal settlement patterns induced by dewatering and excavation in such strata. Field monitoring data were incorporated to validate the numerical model, ensuring accuracy and reliability. Key findings include the following: (1) Dewatering contributes to over 76% of the total settlement at each stage, with confined drawdown being the dominant factor, implying that dewatering optimization should take priority over controlling excavation rate. (2) Under confined dewatering, the settlement influence zone extends beyond 80 m, far exceeding the extension caused by excavation alone; thus, monitoring and protection ranges must be adjusted dynamically. (3) The horizontal permeability of sand shows a nonlinear positive correlation with settlement, and this sensitivity grows with depth, highlighting the need for accurate permeability determination and stricter controls in deep excavations within water-rich sand layers. From an engineering perspective, these findings underscore the importance of prioritizing confined aquifer dewatering management, dynamically expanding settlement monitoring zones, and rigorously characterizing permeability profiles to mitigate excessive ground settlement and protect adjacent infrastructure. Full article

Coastal construction projects often require excavation below the water table, where tidal variability and urban infrastructure generate complex groundwater conditions. This study presents a numerical simulation of water table dynamics in a coastal urban area of Mazatlán, México, influenced by tidal forcing, a lake, and an impermeable seawall. Six critical scenarios were modeled using MODFLOW 6 and ModelMuse interface, covering the period from November 2023 to April 2024. The scenarios correspond to astronomical tide events during the new moon phase, when maximum and minimum tide levels occurred within 24 h. These conditions are related to the highest piezometric levels observed in field. Model calibration was based on 18 field observations collected at 09:00, 12:00, and 15:00 across the selected dates. Model outputs closely matched the field observations, with a root mean square error (RMSE) of 0.056 m, and a mean absolute error (MAE) of 0.049 m. Although the differences are minimal, they reflect short-term variability and limited fluctuation during calibration. However, the full monitoring period showed groundwater levels ranging from −0.10 to 0.53 m above mean sea level (masl), emphasizing the importance of understanding short-term dynamics. This modeling approach supports construction planning, helping to anticipate risks and promote better and informed construction practices. Full article

This study investigates the role of longitudinal aquifer slope in controlling stream–aquifer interaction within bounded floodplain aquifer systems. A series of numerical simulations were conducted to analyze groundwater flow patterns, hyporheic exchange fluxes, and contaminant transport behavior under varying slope conditions. The results showed that increasing slope does not simply enhance hydraulic gradients but fundamentally reorganizes subsurface flow structure. As the slope increases, groundwater flow becomes progressively aligned with the stream, reducing lateral connectivity and confining exchange to a narrow corridor adjacent to the stream. This reorganization leads to the expansion of hydraulically inactive zones and a non-linear response in hyporheic exchange. Exchange flow rates initially increase at low to moderate slopes but decline beyond a threshold at higher slopes, despite higher local gradients. The transition begins at around a 2% slope and becomes pronounced within the range of approximately 3–7%, indicating a shift in flow regime rather than a continuous scaling of interaction intensity. Particle tracking analyses further reveal that slope controls the spatial distribution of contaminant vulnerability. While the overall extent of active transport zones decreases with increasing slope, localized transport potential intensifies near the stream boundary due to higher velocities and reduced residence times. These findings demonstrate that hydraulic gradient magnitude alone is insufficient to characterize stream–aquifer interaction and highlight the importance of flow geometry and connectivity. The results provide a process-based framework for understanding slope-controlled hyporheic exchange and offer insights for improving groundwater vulnerability assessment and management in alluvial systems. Full article

Groundwater contamination by dissolved metals and metalloids in the Chiang Mai Basin is an important drinking-water concern, yet the coupled depth patterns, hydrogeochemical controls, composite contamination status, and screening-level health implications have not previously been assessed in an integrated basin-scale framework. This study evaluated 120 groundwater samples from alluvial wells classified by depth as shallow (≤30 m, n = 40), intermediate (31–60 m, n = 35), and deep (>60 m, n = 45). Samples were analyzed for nine dissolved metals and metalloids (Fe, Mn, As, Cd, Pb, Cr, Zn, Hg, and Se) together with pH, Eh, and total dissolved solids (TDS). The highest exceedance frequencies were observed for Fe (72.5% of samples, >0.3 mg/L acceptability threshold), Mn (65.0%, >0.08 mg/L), and As (45.8%, >10 μg/L). Fe and Mn increased significantly with depth, whereas As was enriched in deep wells but showed no statistically significant depth dependence. Pearson correlation and principal component analysis consistently identified a dominant redox-associated component in which Fe, Mn, and As covaried negatively with Eh, supporting redox-sensitive co-enrichment in deeper groundwater. Contamination factors calculated relative to selected global groundwater background values were >6 for all seven evaluated metals (Fe, Mn, As, Cd, Pb, Cr, and Zn), and the overall pollution load index (PLI) was 9.11, with the highest depth-specific PLI in deep wells (10.42). These indices are interpreted here as background-relative screening tools rather than stand-alone regulatory measures. A screening-level ingestion risk assessment identified arsenic as the dominant toxicological driver, with hazard quotients (HQ) of 1.97 for adults and 4.60 for children, and an estimated lifetime cancer risk (LCR) of 8.87 × 10^–4. The results support targeted monitoring of deeper wells, routine screening for As and Mn, and treatment strategies that can address the co-occurring Fe–Mn–As assemblage in alluvial groundwater. Full article

Sustainable groundwater management represents a main goal for the future in the context of climate change and increasing anthropogenic pressure. In recent decades, intrinsic vulnerability assessment and risk mapping have been established as some of the most important tools for groundwater preservation, but they have also shown limitations due to their static nature and their failure to account for the inherent uncertainty of hydrogeological parameters. This study proposes an innovative hybrid framework that integrates traditional overlay-index methodology (SINTACS Release 5) with stochastic numerical modeling to assess groundwater contamination risk and evolve it into a dynamic time-dependent tool. This methodology was applied to a case study of the Lapisina Valley phreatic aquifer (Northeastern Italy), a strategic area for drinking water supply. Numerical simulations were implemented to reproduce groundwater flow using the MODFLOW-NWT code. To address parametric uncertainty, 237 stochastic realizations of the modeling domain were generated using the Latin Hypercube Sampling method, randomizing hydraulic conductivity values. Advective transport was simulated through forward particle tracking using the MODPATH code, starting from the identified and classified hazard sources within the study area. Assuming the absence of attenuation during transport allowed for a conservative worst-case scenario. The result was the definition of a probabilistic contaminant propagation factor, a time-dependent indicator that quantifies the probability of pollution arrival to a specific discrete portion of the domain. This probabilistic factor was combined with three indexes commonly utilized for risk assessment (the intrinsic vulnerability index, hazard index, and value of the resource) to generate four contamination risk maps representing different timestep scenarios (5, 10, 20, and 50 years) after the arrival of a hypothetical contaminant in the saturated zone. This approach transforms risk mapping from being a useful but static snapshot to a predictive dynamic framework. Full article

Groundwater–surface water interactions in volcanic hydrogeological systems represent a key process in river dynamics and were preliminarily investigated along a river draining the southern sector of the Sabatini Mountains (central Italy) using an integrated hydrogeological and geochemical approach. Serial discharge measurements, combined with physico-chemical parameters, major ions, stable oxygen isotopes, and radon analyses, reveal marked spatial variability in river–aquifer exchanges along distinct river reaches. The Arrone River exhibits clear differences between upstream, intermediate, and downstream sections, reflecting the relative influence of localized anthropogenic inputs, diffuse groundwater discharge from the volcanic aquifer, and subsurface flow contributions. Upstream reaches are characterized by pronounced modifications in discharge and chemistry, whereas intermediate and downstream reaches show progressive groundwater influence, resulting in distinct geochemical signatures and changes in water quality. Correlation and cluster analyses identify reach-specific processes controlling water composition and support the recognition of gaining and mixed river conditions under varying hydrological regimes. These results constrain a conceptual model in which river behavior is governed by spatially heterogeneous groundwater inflows, modulated by seasonal discharge dynamics and local human pressures. This study highlights the importance of reach-scale investigations for understanding SW–GW interactions in volcanic settings and provides transferable insights relevant to groundwater-dependent river systems. Full article

Physicochemical and microbiological parameters are important indicators of drinking water quality. This study assessed the quality of groundwater used for drinking in four regions of Kosovo at 16 locations using an integrated assessment framework that combined physicochemical, microbiological, and Water Quality Index (WQI) approaches. The results reveal substantial spatial variability in water quality. While most physicochemical parameters remained within recommended limits, elevated values of total dissolved solids (up to 2792.5 mg/L), electrical conductivity (up to 2768.5 µS/cm), nitrate (up to 60.75 mg/L), and phosphate (up to 0.875 mg/L) were observed at several locations, indicating localized hydrogeochemical and anthropogenic influences. Dissolved oxygen levels were generally low (0.68–5.49 mg/L), reflecting limited aeration conditions in groundwater systems. Microbiological analysis revealed critical contamination, with Escherichia coli concentrations up to 299.9 CFU/100 mL, and all sampling sites exceeded permissible limits, indicating widespread fecal pollution and rendering the groundwater unsafe for direct consumption. WQI assessment further confirmed this condition, where 93.75% of locations were classified as medium quality using the NSF-WQI method, whereas the WA-WQI method categorized 68.75% of samples as poor and 6.25% as very poor. The novelty of this study lies in the integrated evaluation of hydrogeochemical processes and microbiological contamination using dual WQI methods and multivariate statistical analysis, providing a comprehensive understanding of groundwater degradation pathways. The findings are significant for policymakers, environmental managers, and public health authorities, highlighting the urgent need for groundwater treatment, improved sanitation infrastructure, and sustainable water resource management strategies in vulnerable regions. Full article

Seventy-one percent of the Earth’s surface is covered by water, with groundwater being one of the most important natural resources globally. In Purba Medinipur, the population growth rate has surged to ~0.75% per annum, outpacing that of West Bengal, due to agricultural and industrial development. Urbanization has led to an increase in the built-up area by 139.10% per annum, which has reduced the percolation of water into the groundwater table. Currently, 72% blocks are affected by salinity. Groundwater quality parameters such as pH, total dissolved solids (TDS), turbidity, iron, manganese, total hardness, and chloride were assessed over three seasons—pre-monsoon, monsoon, and post-monsoon—using 326 data points from 2015 to 2022. Turbidity and iron are the primary concerns for groundwater quality, contributing to pollution. Other parameters, including TDS and total hardness, were approaching acceptable limits across all seasons. Since 2021, turbidity has exceeded permissible limits during the pre-monsoon season, resulting from the dissolved minerals and seawater intrusion. The arithmetic weighted groundwater quality index has shown an increasing magnitude over time, indicating a decline in drinking water quality by 2030. The pre-monsoon season exhibits the most severely affected groundwater quality. Principal component analysis indicated that TDS and chloride are the major contaminants during the pre-monsoon, confirming seawater intrusion. In other seasons, metals like iron, TDSs, and manganese are significant contaminants. The hydraulic barriers, subsurface dams, and hybrid treatment can be adopted in the study area to abate the increasing groundwater quality concentration both on a yearly and seasonal basis. Full article

Permeability anisotropy, which is widely present in natural soil deposits, plays an important role in controlling groundwater flow patterns and ground deformation during deep excavation dewatering. However, isotropic assumptions are still commonly adopted in engineering practice, making it difficult to accurately capture realistic subsurface hydraulic conditions. In this study, a deep foundation pit of a metro station in Jinan, China, is taken as a case study. A three-dimensional excavation–dewatering model incorporating permeability anisotropy is established using PLAXIS 3D to systematically investigate the influence of the permeability ratio (Kx/Kz) ranging from 0.1 to 10 on the seepage field evolution, dewatering influence radius, ground surface settlement, and consolidation time history. The results indicate that increasing permeability anisotropy promotes a fundamental transition of the seepage regime from vertically concentrated recharge to laterally dominated radial flow. Correspondingly, the dewatering influence radius exhibits a pronounced non-monotonic response to Kx/Kz, decreasing significantly with increasing permeability ratio and reaching a minimum at approximately Kx/Kz ≈ 5, followed by a slight rebound. Meanwhile, surface settlement profiles evolve from a localized concentration pattern to a widely distributed form as permeability anisotropy increases, accompanied by a remarkable outward expansion of the settlement influence zone. Both the magnitude and spatial distribution of settlement show high sensitivity to variations in permeability anisotropy. Based on these findings, a three-stage conceptual seepage structure model accounting for permeability anisotropy is proposed, characterized by vertically dominated flow, a transitional competition regime, and horizontally dominated flow. The staged evolution of seepage structures is shown to govern the non-monotonic variation in the dewatering influence radius and the spatial–temporal response of ground settlement. The results indicate a dual-scale influence mechanism of permeability anisotropy on dewatering-induced hydro-mechanical behavior, providing a theoretical basis for refined dewatering design and environmental impact assessment in deep excavation projects. Full article