Search Results (109)

Understanding groundwater quality in karst environments is essential, particularly in semi-arid regions where water resources are highly vulnerable to both climatic variability and anthropogenic pressures. The Ghar Boumaaza karst aquifer, located in the semi-arid Tlemcen Mountains of Algeria, represents a critical yet understudied water resource increasingly threatened by climate change and human activity. This study integrates hydrochemical analysis, multivariate statistical techniques, and predictive modeling to assess groundwater quality and characterize the relationship between total dissolved solids (TDSs) and discharge (Q). An analysis of 66 water samples revealed that 96.97% belonged to a Ca²⁺–HCO₃⁻ facies, reflecting carbonate rock dissolution, while 3% exhibited a Cl⁻–HCO₃⁻ facies associated with agricultural contamination. A principal component analysis identified carbonate weathering (40.35%) and agricultural leaching (18.67%) as the dominant drivers of mineralization. A third-degree polynomial regression model (R² = 0.953) effectively captured the nonlinear relationship between TDSs and flow, demonstrating strong predictive capacity. Independent validation (R² = 0.954) confirmed the model’s robustness and reliability. This study provides the first integrated hydrogeochemical assessment of the Ghar Boumaaza system in decades and offers a transferable methodological framework for managing vulnerable karst aquifers under similar climatic and anthropogenic conditions. Full article

Rapid socio-economic development and the impact of human activities have exerted tremendous pressure on the groundwater system of the Dawen River Basin (DRB), the largest tributary in the middle and lower reaches of the Yellow River. Hydrochemical studies on the DRB have largely centered on the upstream Muwen River catchment and downstream Dongping Lake, with some focusing solely on karst groundwater. Basin-wide evaluations suggest good overall groundwater quality, but moderate to severe contamination is confined to the lower Dongping Lake area. The hydrogeologically complex mid-reach, where the Muwen and Chaiwen rivers merge, warrants specific focus. This region, adjacent to populous areas and industrial/agricultural zones, features diverse aquifer systems, necessitating a thorough analysis of its hydrochemistry and origins. This study presents an integrated hydrochemical, isotopic investigation and EWQI evaluation of groundwater quality and formation mechanisms within the multiple groundwater types of the central DRB. Central DRB groundwater has a pH of 7.5–8.2 (avg. 7.8) and TDSs at 450–2420 mg/L (avg. 1075.4 mg/L) and is mainly brackish, with Ca²⁺ as the primary cation (68.3% of total cations) and SO₄²⁻ (33.6%) and NO₃⁻ (28.4%) as key anions. The Piper diagram reveals complex hydrochemical types, primarily HCO₃·SO₄-Ca and SO₄·Cl-Ca. Isotopic analysis (δ²H, δ¹⁸O) confirms atmospheric precipitation as the principal recharge source, with pore water showing evaporative enrichment due to shallow depths. The Gibbs diagram and ion ratios demonstrate that hydrochemistry is primarily controlled by silicate and carbonate weathering (especially calcite dissolution), active cation exchange, and anthropogenic influences. EWQI assessment (avg. 156.2) indicates generally “good” overall quality but significant spatial variability. Pore water exhibits the highest exceedance rates (50% > Class III), driven by nitrate pollution from intensive vegetable cultivation in eastern areas (Xiyangzhuang–Liangzhuang) and sulfate contamination from gypsum mining (Guojialou–Nanxiyao). Karst water (26.7% > Class III) shows localized pollution belts (Huafeng–Dongzhuang) linked to coal mining and industrial discharges. Compared to basin-wide studies suggesting good quality in mid-upper reaches, this intensive mid-reach sampling identifies critical localized pollution zones within an overall low-EWQI background. The findings highlight the necessity for aquifer-specific and land-use-targeted groundwater protection strategies in this hydrogeologically complex region. Full article

Karst aquifer systems are highly vulnerable due to their unique underground water flow characteristics, making them prone to contamination and abandonment. This study compares an active karst water source (Ljubija) with a previously abandoned one (Rečica) to assess freshwater quality and water protection risks, especially as water scarcity becomes a concern during dry summer periods. The Ljubija and Rečica catchments, designated as water protection areas (WPAs), were monitored over a year (January–December 2020). Groundwater (GW) and surface water (SW) were analyzed twice a month during both dry and wet periods, adhering to European and national guidelines. An interdisciplinary approach integrated natural and human impact indicators, linking water quality to precipitation, hydrogeography, and landscape characteristics. After Slovene regulation standards (50 mg/L), the Ljubija source demonstrated stable water quality, with low nitrate levels (average 2.6 mg/L) and minimal human impact. In contrast, the Rečica catchment was more vulnerable, with its GW excluded from drinking use since the 1990s due to organic contamination, worsened by the area’s karst hydrogeology. In 2020, its nitrate concentration averaged 6.0 mg/L. These findings highlight the need for improved monitoring regulations, particularly for vulnerable karst water sources, to safeguard water quality and ensure sustainable use. Full article

This study systematically unravels the hydrochemical evolution mechanisms and driving forces in multi-aquifer systems of Qingdao, a coastal economic hub. Integrated hydrochemical analysis of porous, fissured, and karst water, combined with PHREEQC modeling and Positive Matrix Factorization (PMF), deciphers water–rock interactions and anthropogenic perturbations. Groundwater exhibits weak alkalinity (pH 7.2–8.4), with porous aquifers showing markedly higher TDS (161.1–8203.5 mg/L) than fissured (147.7–1224.8 mg/L) and karst systems (361.1–4551.5 mg/L). Spatial heterogeneity reveals progressive hydrochemical transitions (HCO₃-Ca → SO₄-Ca·Mg → Cl-Na) in porous aquifers across the Dagu River Basin. While carbonate (calcite) and silicate weathering govern natural hydrochemistry, evaporite dissolution and seawater intrusion drive severe groundwater salinization in the western Pingdu City and the Dagu River Estuary (localized TDS up to 8203.5 mg/L). PMF source apportionment identifies acid deposition-enhanced dissolution of carbonate/silicate minerals, with nitrate contamination predominantly sourced from agricultural runoff and domestic sewage. Landfill leachate exerts pronounced impacts in Laixi and adjacent regions. This study offering actionable strategies for salinity mitigation and contaminant source regulation, thereby providing a scientific framework for sustainable groundwater management in rapidly urbanizing coastal zones. Full article

The objective of this study is to detect the locations of submarine groundwater discharge (SGD) in the coastal area of the El Jebha region, located in northwestern Morocco. It is hypothesized that this zone is fed by one of the most rain-rich karstic aquifers in Morocco (the Dorsale Calcaire). The region’s geology is complex, characterized by multiple faults and fractures. Thermal remote sensing is used in this study to locate potential SGD zones, as groundwater emerging from karst systems is typically cooler than surrounding ocean water. Landsat satellite imagery was used to assess temperature variations and detect anomalies associated with the presence of freshwater in the marine environment. El Jebha’s geographical location, with a direct interface between limestone and sea, makes it an ideal site for the appearance of submarine groundwater discharges. This study constitutes the first use of Landsat-8/9 thermal-infrared imagery, processed with a multi-temporal fuzzy-overlay method, to detect SGD. Out of 107 Landsat scenes reviewed, 16 cloud-free images were selected. The workflow identified 18 persistent cold anomalies, of which three were classified as high-probability SGD zones based on recurrence and spatial consistency. The results highlight several potential SGD zones, confirming the cost-effectiveness of thermal remote sensing in mapping thermal anomalies and opening up new perspectives for the study of SGD in Morocco, where these phenomena remain rarely documented. Full article

The northern Yucatán Peninsula hosts a complex karstic environment shaped by carbonate platform development and the Chicxulub impact event, making subsurface characterization crucial for geological and hydrogeological studies. This work aimed to resolve the shallow crustal structure and identify major tectonic features that influence karst processes and groundwater dynamics. We applied a rapid 3D gravity inversion method, linear back projection (LBP), to Bouguer anomaly data, combined with Euler deconvolution to map shallow and deep fault systems. The inversion produced a high-resolution density model down to 12.8 km depth, revealing key geological structures. Multilevel thresholding delineated significant low-density basins, notably the Chicxulub crater, as well as buried sedimentary basins. Euler solutions identified fault networks that coincide with areas of intense karstification, particularly in the eastern peninsula. Results highlight the interplay between impact-related tectonics and karst evolution, influencing groundwater flow paths and recharge zones. This study demonstrates the effectiveness of gravity inversion and Euler deconvolution for regional crustal imaging in carbonate platforms and emphasizes the need for further local-scale surveys to investigate coastal aquifer vulnerability and saltwater intrusion processes. Full article

This study assesses the functioning of the karst aquifer system located on the Croatian coast of the Adriatic Sea, where saltwater intrusion often presents a major problem for freshwater supply. We use two years of sensor data collected from two coastal springs to conduct a range of time-invariant and time-variant statistical analyses over various timescales. We perform separate analyses of the within-day and longer-term variation in the data as well as the interactions between the spring levels, salinity, rainfall, and sea levels. Such comprehensive analyses provide a greater understanding into the inner functioning of the intricate, heavily karstified aquifers. Time-invariant time-series analyses of the hourly data indicate that the spring levels and salinity are strongly controlled by sea levels. Furthermore, time-variant wavelet analyses demonstrate that the variation in spring levels in both springs has two modes defined by flow regime. Increases in the delay of the spring response to sea level indicate that aquifer diffusivity decreases in low flow conditions. Analyses facilitated the development of a conceptual model of the karst subsurface in the discharge zone. Using daily data, we constructed a linear mixed model of the spring levels. This model identified long-term sea level changes, rainfall from previous weeks, and seasonal recharge patterns as the primary factors influencing longer-term spring dynamics. Full article

Groundwater is a critical drinking water source in arid regions globally, where reliance on groundwater is highest. However, disparities in groundwater availability, access, and quality pose challenges to water security. This case study employs geostatistical tools, multivariate regression, and clustering analysis to examine the intersection of groundwater level changes (availability), socioeconomic and regulatory factors (access), and nitrate and arsenic contamination (quality) across 1881 groundwater-supplied drinking water service areas in Arizona. Groundwater availability declined over 20-year and 10-year periods, particularly outside designated management areas, with mean annual decline rates ranging from −15.97 to −0.003 m/year. In contrast, increases (0.003 to 13.41 m/year) were concentrated in urban and managed areas. Karst aquifers show long-term resilience but short-term vulnerability. Non-designated areas exhibit mixed effects, reflecting variable management effectiveness. Disparities in groundwater access emerge along various socioeconomic and regulatory lines. Communities with higher Black populations are twice as likely (OR = 2.01, p < 0.001) to experience groundwater declines, while Hispanic/Latino communities have lower depletion risks (OR = 0.92, p < 0.001). Tribal oversight significantly reduces groundwater decline risk (OR = 0.62, p < 0.001), whereas state–primacy areas show mixed effects. Higher female populations correlate with increased groundwater declines, while older populations (65+) experience greater stability. Married-family households and institutional housing are associated with greater declines. Migrant worker housing shows protective effects in long-term models. Rising groundwater levels are associated with higher nitrate and arsenic detection, reinforcing recharge-driven contaminant mobilization. Nitrate exceedance (OR = 1.05) responds more to short-term groundwater changes, while arsenic exceedance persists over longer timescales (OR = 1.01–1.05), reflecting their distinct hydrogeochemical behaviors. Community water systems show higher pollutant detection rates than domestic well areas, suggesting monitoring and infrastructure differences influence contamination patterns. Tribal primacy areas experience lower groundwater declines but show mixed effects on water quality, with reduced nitrate exceedance probabilities; yet they show variable arsenic contamination patterns, suggesting that governance influences availability and contamination dynamics. These findings advance groundwater sustainability research by quantifying disparities across multiple timescales and socio-hydrogeological drivers of groundwater vulnerability. The results underscore the need for expanded managed aquifer recharge, targeted regulatory interventions, and strengthened Tribal water governance to reduce inequities in availability, access, and contamination risk to support equitable and sustainable groundwater management. Full article

Karst water supplies freshwater to approximately a quarter of the global population and plays a crucial role in supporting the socioeconomic development of karst regions. As a key indicator for assessing and managing karst water resources, karstic water storage variation is influenced not only by the complex structure of karst aquifer media but also by the variability in natural precipitation infiltration. Based on the hydrogeological conditions of a typical karst aquifer system in northern China, this study developed a three-dimensional physical experimental setup and established a corresponding groundwater flow numerical model coupled with equivalent porous media and conduits. The factors affecting spring flow recession were investigated from a source–sink perspective. Precipitation events were categorized into two types: those with the same duration but different intensities and those with the same total volume but different intensities. The influence of varying precipitation events on the estimation of karstic water storage variation was quantitatively evaluated using the exponential fitting method, based on the analysis of spring flow recession curves. These findings could provide scientific guidance for the development, utilization, and protection of karst water resources. Full article

Karst aquifers can be highly productive water sources but are vulnerable to contamination by pathogens because of integrated surface and subsurface drainage. Our study focuses on the karstic Royal Spring basin in Kentucky, encompassing urban and agricultural land uses. The city of Georgetown distributes treated water from Royal Spring to over 33,000 customers. We examined E. coli dynamics at Royal Spring from June 2021 through June 2022, assessing variability under wet versus dry weather conditions. We also used quantitative microbial risk assessment (QMRA) to estimate potential health risks from the pathogenic bacterium E. coli O157:H7. E. coli concentrations in weekly water samples varied from 12 to 1732.8 MPN/100 mL, with a geometric mean of 117.2 MPN/100 mL. The mean concentration in wet periods was approximately double that during dry conditions. Because the pathogen was not detected by quantitative PCR (qPCR), we conducted QMRA based on literature data for water treatment plant operations (occupational) and recreational activities near the spring. The median probability of annual infection was 5.11 × 10⁻³ for occupational exposure and 1.45 × 10⁻² for recreational exposure. Uncertainty and sensitivity analyses revealed that health risks were most sensitive to the pathogen/E. coli ratio and ingestion rate. Although the pathogen was not detected by qPCR, the presence of E. coli suggests potential fecal contamination. This highlights the importance of continued monitoring and investigation of different detection methods to better understand potential health risks in karst systems. Full article

As shallow coal resources in China become increasingly depleted, deep coal mining in complex geological areas has become an inevitable trend. However, the technical challenges associated with deep mining are becoming more significant, particularly the issues related to mine water hazards. This study utilized hydrogeological data from the III3 Mining Area in the Zhuxianzhuang Coal Mine, Anhui Province, and employed GMS (Groundwater Modeling System) software to construct a numerical karst water flow model under deep mining conditions. By simulating variations in the flow field, the study verified the drainage potential of the limestone water at the base of Seam 10 and assessed the water conductivity and connectivity of the F22 fault. The following conclusions were obtained: The simulation effectively captured the formation process of the karst water drawdown cone in the study area. The observed water level variations in different monitoring wells aligned well with the engineering reality after validation. The limestone water at the base of Seam 10 in the III3 Mining Area exhibited good transmissivity, weak recharge, and high drainage potential. Although the F22 fault is a normal fault with a maximum displacement of 550 m, offsetting formations from Seam 3 to the Ordovician limestone, its connectivity and water conductivity are poor, exhibiting significant water-blocking properties. The specific capacity (q) ranges from 1.40 × 10⁻⁴ to 3.26 × 10⁻³ m³/(s·m), and the hydraulic conductivity (K) ranges from 2.10 × 10⁻⁵ to 6.80 × 10⁻⁵. Under deep coal mining conditions, the extraction of coal disturbs the underlying limestone, generally resulting in an increase in its permeability coefficient compared to pre-mining conditions. The permeability coefficient (K) from the measured data before mining impact ranged from 0.000067 to 0.0022, while the simulated values after mining impact ranged from 0.0021 to 0.09. Additionally, mining activities affect the hydraulic head, flow rate, and flow paths of the karst water; the floor karst water is easily drainable, effectively reducing water pressure and the inrush coefficient, thus lowering water hazard risks. Although the mining area is affected by the large F22 fault, its water-resisting properties under sufficient drainage conditions prevent direct connectivity between the coal seam and the aquifer, avoiding water hazards. As global coal resources continue to be exploited, deep mining will inevitably become a common trend in coal extraction worldwide. This study develops a hydrogeological model tailored to deep mining under fault conditions, offering a solid theoretical foundation and practical reference for the prevention and management of mine water hazards on a global scale. This advancement contributes to the development of sustainable mining practices across the global industry. Full article

The watershed of the Peixe River lies in central Minas Gerais state, close to Belo Horizonte city, a densely populated area. The area is located in the geological context of Quadrilátero Ferrífero, one of the most prominent mineral provinces in Brazil. To better recognize surface and groundwater availability, some methodologies have been applied to evaluate the minimal surface flow rates, groundwater recharge, and water reserves. The basin includes three main aquifer systems: Cauê (porous and fissured aquifer), related to iron formations; Gandarela, related to karst-fissured rocks; and Cercadinho, related to metapelite rocks. The Cauê aquifer presented the highest effective porosity and hydraulic conductivity. In contrast, the Cercadinho aquitard shows the lowest hydrodynamic parameters. Data between the years of 2004 and 2024 from 21 pumping tests from wells associated with the three aquifer systems were obtained to estimate the respective recharge rate. The recharge was evaluated by numeric recursive filter and recession-curve displacement methods. The recharge results with the numeric filter method showed underestimated values. Regarding the recession-curve displacement method, the results were more consistent with other studies in the surroundings. The average recharge estimated for the basin represents 24% to 54% of annual pluviometry in the hydrological periods of analysis. The recharge data were accounted for in the reserves calculation, including permanent and renewable reserves. Total permanent reserves were estimated to be 3.16 × 10⁹ m³, including the prior aquifer systems of Cauê, Gandarela, and Cercadinho. The total mean renewable reserves of the basin were calculated to be 4.55 × 10⁷ m³/year in the analyzed period. The high BFImax indexes found in baseflow separation, above 90%, suggest a relevant contribution of the karstic Gandarela aquifer on the watershed surface flow. Although in some years it has been concluded that groundwater exploitation outlines the renewable resources availability, in 2024’s scenario, the granted water volume was lower than the estimated availability and reserves. The best methodologies for coupling surface and groundwater are the Weibull distribution for reference surface flows and the recessive-curve displacement for baseflow separations. This research will be a contribution to water resources management strategies for regions with high population growth and water demand increase. Full article

Groundwater is a vital drinking water source, especially in arid regions, sustaining both urban and rural populations. Its quality is influenced by natural (hydrogeological) and human-driven (demographic, policy) factors, which may pose significant public health risks, especially for communities relying on unregulated water supplies. This study addresses critical gaps by examining groundwater vulnerability and contamination disparities, emphasizing their implications for public health and equitable resource management. It analyzes the impact of socio-hydrogeological factors on arsenic and nitrate levels in groundwater-supplied systems in Arizona, U.S. Methods include spatial analysis, ANOVA, multivariate regression, and cluster analysis. Significant disparities in arsenic and nitrate contamination, including exceedances of regulatory limits, were observed across supply types, aquifer characteristics, jurisdictional oversights, and groundwater management areas. Domestic wells and community water systems showed distinct contamination risks. Groundwater vulnerability was influenced by geological differences (karst vs. alluvial aquifers) and regulatory oversight, with Tribal and State systems facing unique challenges and resource needs. Socioeconomic disparities were evident, with minority communities, institutional facilities, rural areas, and specific housing types disproportionately exposed to higher contaminant levels. These findings unveil the intersection of race, socioeconomic status, and public health risks, offering an adaptable framework for addressing similar groundwater challenges in arid and semi-arid regions globally. This study is innovative in its focus on policy distinctions between private and regulated wells, karst and alluvial aquifers, and State and Tribal jurisdictions. It emphasizes the need for targeted vulnerability assessments and remediation strategies that integrate geological, hydrological, and regulatory factors to address risk disparities in vulnerable communities. These environmental inequities underscore the urgent need for stronger regulations and strategic resource allocation to support marginalized communities. The study recommends enhancing monitoring protocols, prioritizing resource distribution, and implementing targeted policy interventions to ensure equitable and sustainable access to safe drinking water in arid regions. Full article

The Prespa–Ohrid lake system in the southwest Balkan region is the oldest permanent lake system in Europe and a global hotspot of biodiversity and endemism. Its smaller component, Lake Macro Prespa (or simply called Prespa), shared by North Macedonia, Albania and Greece has suffered a dramatic water-level fall (nearly 10 m since the 1950s). It was greater in the periods 1987–1993 and 1998–2004 and has further accelerated in the last 5 years. Analysis of satellite images (remote sensing) revealed that over the period 1984–2020 Prespa Lake lost 18.87 km² of its surface (6.9% of its size, dropping from 273.38 km² to 254.51 km²), with a decline in the volume of water estimated as about 54%, even reaching 56.8% in 2022. The environmental status of the lake has also been compromised and the process of its eutrophication is enhanced. The aim of this study is to summarize the current understanding of the diminishing trend in the water level and the factors that have contributed to it. The lake is highly sensitive to external impacts, including climate change, mainly restricted precipitation and increased water abstraction for irrigation. Importantly, nearly half of its outflow is through karst aquifers that feed Ohrid Lake. Of note, the hydrology and especially hydrogeology of the catchment has not been studied in sufficient detail and accurate data for the present state are missing, largely due to a lack of coordinated investigations by the three neighboring countries. However, recent estimation of the water balance of Prespa Lake, elaborated with the consideration of only the natural sources of inflow (precipitation and river runoff) and outflow (evaporation and loss of water through the karst channels) suggested a negative balance of 53 × 10⁶ m³ annually. Our study also offers an estimated projection for the water level in the future in different climate scenarios based on linear regression models that predict its complete loss before the end of the present century. Full article

Water scarcity is a global issue, especially in semi-arid and arid regions where precipitation is irregularly distributed over time and space. Predicting groundwater flow in heterogeneous karst terrains, which are essential water sources, presents a significant challenge. This article integrates geology, hydrology, and water monitoring to develop a pioneering conceptual and numerical model of groundwater flow in the Montes Claros Region (Vieira River Watershed, Brazil). This model was evaluated under various climate change scenarios, considering changes in rainfall, groundwater consumption, and population growth over the current century. The results indicate that a decline in water table levels is inevitable, primarily driven by population growth and high pumping rates rather than rainfall fluctuations. This underscores the urgent need for improved monitoring, model upgrading, and more importantly, targeted water resource management for Montes Claros. Full article