Search Results (110)

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

Geological storage is an integral element of the green energy transition. Geological formations, such as aquifers, depleted reservoirs, and hard rock caverns, are used mainly for the storage of hydrocarbons, carbon dioxide and increasingly hydrogen. However, potential adverse effects such as ground movements, leakage, seismic activity, and environmental pollution are observed. Existing research focuses on monitoring subsurface elements of the storage, while on the surface it is limited to ground movement observations. The review was carried out based on 191 research contributions related to geological storage. It emphasizes the importance of monitoring underground gas storage (UGS) sites and their surroundings to ensure sustainable and safe operation. It details surface monitoring methods, distinguishing geodetic surveys and remote sensing techniques. Remote sensing, including active methods such as InSAR and LiDAR, and passive methods of multispectral and hyperspectral imaging, provide valuable spatiotemporal information on UGS sites on a large scale. The review covers modelling and prediction methods used to analyze the environmental impacts of UGS, with data-driven models employing geostatistical tools and machine learning algorithms. The limited number of contributions treating geological storage sites holistically opens perspectives for the development of complex approaches capable of monitoring and modelling its environmental impacts. Full article

The efficacy of water resource management and protection hinges on a profound understanding of the controlling factors and regulatory mechanisms that shape groundwater chemistry within aquifers. Despite this, our comprehension of how groundwater chemistry and ion sources vary across diverse aquifer types remained limited. To bridge this gap, our study conducted a detailed hydrochemical and statistical investigation of porous, fissured, and karst aquifers. By applying multivariate statistical techniques, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), the hydrochemical characteristics and main ion sources of each aquifer type, as well as distinct controlling factors and regulation patterns, were determined. Notably, evaporation predominantly affected the hydrochemistry of porous aquifers, whereas mineral dissolution and rock weathering processes played a pivotal role in shaping the groundwater evolution of fissured and karst aquifers. HCO₃⁻ and SO₄²⁻ are the most common anions of all types, while Na⁺ is dominant in porous and fissured aquifers and Ca²⁺ is dominant in karst aquifers. The most common hydrochemical types identified were HCO₃-Ca·Mg (accounting for approximately 56.84%) and SO₄·Cl-Na (constituting approximately 21.75%). PCA results revealed that lateral recharge from fissured aquifers in hilly regions into the groundwater of porous aquifer, and wastewater discharge and agricultural fertilizer application, significantly impact the groundwater chemistry across all three aquifer types. It is worth noting that the dissolution of carbonate minerals, often influenced by human activities, had a profound effect on the hydrochemistry of each aquifer. Conversely, the dissolution of evaporitic minerals affected groundwater chemistry primarily through cation exchange processes. In summary, the hydrochemical characteristics of these aquifer types were predominantly shaped by a complex interplay of mineral dissolution, cation exchange, evaporation, and anthropogenic activities, with notable contributions from fissured aquifer recharge and pollution. These insights were critical for informing national-level strategies for groundwater resource protection and management. 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

Simulation experiments are a crucial method for investigating overburden failure, strata movement, and strata control during coal mining. However, traditional similar materials struggle to effectively monitor internal damage, fracturing, and dynamic development processes within the strata during mining. To address this issue, carbon fibers were introduced into the field of similar material simulation experiments for mining. Leveraging the excellent conductivity and the sensitive feedback of resistivity changes in response to damage of this composite material enabled real-time monitoring of internal damage and fracture patterns within the mining strata during similar simulation experiments, leading to the development of a carbon fiber similar simulation composite material with damage self-sensing properties. This study found that as the carbon fiber content increased, the evolution patterns of the electrical resistance change rate and the damage coefficient of the similar material tended to coincide. When the carbon fiber content in the similar material exceeded 2%, the electrical resistance change rate and the damage coefficient consistently exhibited synchronized growth with identical increments. A similar simulation experiment revealed that after the completion of workface mining, the thick sandstone aquifer did not develop significant cracks and remained stable. In the early stages of mining, damage rapidly accumulated at the bottom of the thick aquifer, approaching the failure threshold. In the middle layers, a step-like increase in the damage coefficient occurred after mining reached a certain width, while the top region was less affected by mining activities, resulting in less significant damage development. The research findings offer new experimental insights into rock layer movement and control studies, providing theoretical guidance for the prediction, early warning, and prevention of dynamic disasters in mines with thick key layers. Full article

Natural recharge in karst aquifers is a key component of global water resources, yet its estimation remains challenging due to the complexity of karst hydrogeological processes. The recharge assessment deserves special consideration, especially in the current global climate and sustainability challenges. This study poses a methodology to appraise natural recharge rates in karst aquifers worldwide, drawing on climatic and geological data. In this regard, this study applies a methodology previously developed by two of the authors, in which natural recharge over large areas is considered a fixed fraction of precipitation, which varies according to different lithologies of similar hydrogeological behavior (hydro-lithological units). Given that carbonate rocks are known to have the highest recharge rate relative to precipitation (34.3%), the method builds on existing karst and average precipitation maps to calculate worldwide recharge in karst aquifers. Recharge is appraised at 4,381,063.7 hm³/yr, which represents 34.5% of the global groundwater resources, a percentage that indicates the importance of karst in this regard. Based on maps of recharge values worldwide, this study highlights the importance of carbonate aquifers when compared with assessments of the world’s groundwater resources made by international institutions or other types of aquifers. The method is contrasted with other ways of assessing groundwater resources used in diverse regions of Europe. The impact of different climate change scenarios on the natural recharge of these karst aquifers has also been analyzed. Thus, under a climate change scenario in 2050, it is estimated that natural recharge will be reduced by about 10%. Full article

Morocco’s Témara Plain relies heavily on its aquifer system as a critical resource for drinking water, irrigation, and industrial activities. However, this essential groundwater reserve is increasingly threatened by over-extraction, seawater intrusion, and complex hydrogeochemical processes driven by the region’s geological characteristics and anthropogenic pressures. This study aims to assess groundwater quality and its vulnerability to pollution risks and map the spatial distribution of key hydrochemical processes through an integrated approach combining Geographic Information System (GIS) techniques and multivariate statistical analysis, as well as applying the DRASTIC model to evaluate water vulnerability. A total of fifty-eight groundwater samples were collected across the plain and analyzed for major ions to identify dominant hydrochemical facies. Spatial interpolation using Inverse Distance Weighting (IDW) within GIS revealed distinct patterns of sodium chloride (Na-Cl) facies near the coastal areas with chloride concentrations exceeding the World Health Organization (WHO) drinking water guideline of 250 mg/L—indicative of seawater intrusion. In addition to marine intrusion, agricultural pollution constitutes a major diffuse pressure across the aquifer. Shallow groundwater zones in agricultural areas show heightened vulnerability to salinization and nitrate contamination, with nitrate concentrations reaching up to 152.3 mg/L, far surpassing the WHO limit of 45 mg/L. Furthermore, other anthropogenic pollution sources—such as wastewater discharges from septic tanks in peri-urban zones lacking proper sanitation infrastructure and potential leachate infiltration from informal waste disposal sites—intensify stress on the aquifer. Principal Component Analysis (PCA) identified three key factors influencing groundwater quality: natural mineralization due to carbonate rock dissolution, agricultural inputs, and salinization driven by seawater intrusion. Additionally, The DRASTIC model was used within the GIS environment to create a vulnerability map based on seven key parameters. The map revealed that low-lying coastal areas are most vulnerable to contamination. Full article

Uncovering the characteristics of groundwater pollution and its driving mechanisms are crucial for maintaining its ecological functions. This study focuses on hydrochemical changes and their driving factors in groundwater from different aquifers in industrial zones, taking Zibo City, Shandong Province, China, as the research area. During the dry and flood seasons of 2022, samples of phreatic water in pore media (17 sites) and karst confined water (23 sites) were collected and monitored. Piper trilinear diagrams, Gibbs diagrams, ion ratio diagrams, and a principal component analysis (PCA) were used for in-depth analyses. Pore phreatic water had higher excess rates of Na⁺, Cl⁻, and NO₃⁻ than karst confined water, which indicated a greater degree of human impact compared with karst confined water. The main hydrochemical type was HCO₃·SO₄-Ca, but in the dry season, pore phreatic water shifted to HCO₃·SO₄·Cl-Ca. The ion ratios and PCA indicated that the groundwater quality was mainly controlled by water–rock interactions and industrial activities. In the flood season, pore phreatic water was influenced by evaporite dissolution, industrial activities, and domestic sewage, while in the dry season, it was affected by halite and carbonate weathering dissolution and domestic sewage. Karst confined water was controlled by water–rock interactions and industrial activities in both seasons. The findings reveal that the key drivers of groundwater quality displayed significant differences depending on the aquifer type and seasonal variations. As such, customized approaches are essential to efficiently address and counteract the decline in groundwater quality. Full article

This study investigates groundwater flow patterns in a landslide area above the settlement of Koroška Bela in NW Slovenia using a series of tracer tests with sodium chloride (NaCl) and fluorescein (uranine). The tracer experiments, using a combination of pumping tests and continuous groundwater observations, reveal two distinct groundwater flow horizons within the landslide body: a prevailing shallower flow within highly permeable gravel layers and a slower deep flow in the weathered low-permeability clastic layers. Uranine injections suggest longer retentions, indicating complex hydrogeological conditions. Groundwater is recharged by the infiltration of precipitation and subsurface inflow from the upper-lying carbonate rocks. In the upper landslide, highly permeable gravel layers accelerate flow, especially during heavy rainfall, while downstream interactions between permeable gravel and less permeable clastic materials create local aquifers and springs. These groundwater dynamics significantly influence landslide stability, as rapid infiltration during intense precipitation events can lead to transient increases in pore water pressure, reducing shear strength and potentially triggering slope movement. Meanwhile, slow deep flows contribute to prolonged saturation of critical failure surfaces, which may weaken the landslide structure over time. The study emphasizes the region’s geological heterogeneity and landslide stability, providing valuable insights into the groundwater dynamics of this challenging environment. By integrating hydrogeological assessments with engineering measures, the study provides supportive information for mitigating landslide risks and improving groundwater management strategies. Full article

Due to the complex reservoir types and strong heterogeneity of fractured–vuggy reservoirs with aquifers, evaluating such reservoirs’ dynamic reserves and aquifer size is challenging. This paper established a segmented elastic-drive material balance equation based on the material balance principle by combining the functional relationships among the crude oil volume factor, crude oil compressibility, and formation pressure. The PELT algorithm was used to segment the water invasion stages, and nonlinear least squares fitting was employed to determine the rock compressibility, dynamic reserves, and aquifer size of fractured–vuggy reservoirs. This study shows that production in fractured–vuggy reservoirs with aquifers can be divided into three stages: no water invasion, initial water invasion, and full water invasion. Rock compressibility and dynamic reserves can be calculated using production data from the no water invasion stage, while the aquifer size can be determined from data in the water invasion stage. Influenced by connectivity and production regulations, aquifers may not be fully affected by pressure waves, causing the aquifer size to increase gradually until stabilization. Compared with numerical simulation data, the method presented in this paper achieves errors of 0.34%, 0.67%, and 1.19% for rock compressibility, dynamic reserves, and aquifer size, respectively. Full article

As the global economy moves toward net-zero carbon emissions, large-scale energy storage becomes essential to tackle the seasonal nature of renewable sources. Underground hydrogen storage (UHS) offers a feasible solution by allowing surplus renewable energy to be transformed into hydrogen and stored in deep geological formations such as aquifers, salt caverns, or depleted reservoirs, making it available for use on demand. This study thoroughly evaluates UHS concepts, procedures, and challenges. This paper analyzes the most recent breakthroughs in UHS technology and identifies special conditions needed for its successful application, including site selection guidelines, technical and geological factors, and the significance of storage characteristics. The integrity of wells and caprock, which is important for safe and efficient storage, can be affected by the operating dynamics of the hydrogen cycle, notably the fluctuations in pressure and stress within storage formations. To evaluate its potential for broader adoption, we also examined economic elements such as cost-effectiveness and the technical practicality of large-scale storage. We also reviewed current UHS efforts and identified key knowledge gaps, primarily in the areas of hydrogen–rock interactions, geochemistry, gas migration control, microbial activities, and geomechanical stability. Resolving these technological challenges, regulatory frameworks, and environmental sustainability are essential to UHS’s long-term and extensive integration into the energy industry. This article provides a roadmap for UHS research and development, emphasizing the need for further research to fully realize the technology’s promise as a pillar of the hydrogen economy. Full article

The radiological impact of radionuclide transport via groundwater pathways at the Wolsong Low- and Intermediate-Level Waste (LILW) Disposal Center was estimated by considering site-specific characteristics, including hydrogeology, geochemistry, and land use. Human intrusion scenarios, such as groundwater well development, were analyzed to evaluate potential pumping volumes and radionuclide migration pathways. Particular attention was given to the hydrological and geochemical aspects of radionuclide transport, with a focus on local aquifer heterogeneity, flow dynamics, and interactions with engineered barriers and surrounding rock formations that delay radionuclide migration through sorption and other retention mechanisms. Sorption coefficients (K_d), calibrated using site-specific geochemical data, were incorporated to ensure realistic modeling of radionuclide behavior. A hierarchical approach integrating scenario screening, particle tracking techniques, and mass transfer modeling was employed. Numerical simulations using FEFLOW ver. 7.3 and GoldSim ver. 14.0 software provided insights into near-field and far-field transport phenomena under well pumping conditions. The results revealed distinct spatial flux behaviors, where carbon-14 (¹⁴C) dominated near-field flux due to its high inventory, while technetium-99 (⁹⁹Tc) emerged as the primary dose contributor in the far-field flux, owing to its anionic nature and limited sorption capacity. Additionally, under high-pH conditions near concrete barriers, cellulose degradation into isosaccharinic acid was identified, enhancing radionuclide mobility through complex formation. These findings underscore the importance of site-specific sorption and speciation parameters in safety assessment and highlight the need for accurate geochemical modeling to optimize waste placement and ensure long-term disposal safety. The outcomes provide valuable insights for optimizing waste placement and contribute to the development of evidence-based safety strategies for long-term performance assessment. Full article

The sustainable management of groundwater in the Jimma area is complicated by a lack of comprehensive studies on its chemical makeup and the geochemical processes influencing its hydrochemistry. This research aims to fill that gap by examining 51 groundwater samples from various sources, including deep groundwaters, shallow groundwaters, hand-dug well groundwaters, surface waters, and springs within the area primarily consisting of complex volcanic rocks. The goal is to describe the hydrogeochemical characteristics and determine the key processes affecting groundwater composition in this volcanic area. The study identifies clear patterns in cation and anion concentrations. For deep groundwaters, the average cation concentration is ranked as Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, while shallow groundwaters, hand-dug well groundwaters, surface waters, and springs show a ranking of Ca²⁺ > Na⁺ > Mg²⁺ > K⁺. The major anions are typically ordered as HCO₃⁻ > NO₃⁻ > Cl⁻ > SO₄²⁻. The quantitative hydrogeochemical analysis indicates that the freshwater types in the region are primarily Ca-HCO₃ and Ca-Mg-HCO₃, with some highly mineralized Na-HCO₃ waters also detected. The weathering of silicate minerals mainly drives the geochemical processes affecting groundwater chemistry. An increase in mineralization, suggested by saturation indices, points to a longer residence time underground, with deep groundwaters exhibiting the highest saturation levels and springs the lowest. This mineralization is especially significant for Mg-silicates and carbonates. Stability diagrams for feldspar minerals further demonstrate groundwater evolution along flow paths, revealing that shallow systems are in equilibrium with minerals like gibbsite, whereas deeper systems achieve stability with albite, Ca-montmorillonite, and microcline. Higher CO₂ levels (10^−1.5 to 10^0.5 atm), likely from mantle-magma degassing, add more HCO₃⁻ to the deeper aquifers. This study offers the first thorough characterization of the groundwater composition in the Jimma area and provides important insights into the Jimma area’s hydrogeochemical development, establishing a basis for enhanced groundwater management within this intricate volcanic aquifer system. Full article

Geothermal energy is a crucial component contributing to the development of local thermal energy systems as a carbon-neutral and reliable energy source. Insights into its availability derive from knowledge of geology, hydrogeology and the thermal regime of the subsurface. This expertise helps to locate and monitor geothermal installations as well as observe diverse aspects of natural and man-made thermal effects. Temperature measurements were performed in hydrogeological boreholes in south-western Poland using two methods, i.e., manual temperature logging and optical fibre distributed temperature sensing (OF DTS). It was assumed the water column in each borehole was under thermodynamic equilibrium with the local geothermal gradient of the subsurface, meaning rocks and aquifers. Most of the acquired results show typical patterns, with the upper part of the log depending on altitude, weather and climate as well as on seasonal temperature changes. For deeper parts, the temperature normally increases depending on the local geothermal gradient. The temperature logs for some boreholes located in urban agglomerations showed anthropogenic influence caused by the presence of infrastructure, the urban heat island effect, post-mining activities, etc. The presented research methods are suitable for applications connected with studies crucial to selecting the locations of geothermal installations and to optimize their technical parameters. The observations also help to identify zones of intensified groundwater flow, groundwater inrush into wells, fractured and fissured zones and many others. Full article

The Qinglian River plays a significant role in China’s national water conservation security patterns. To clarify the relationship between hydrogeochemical properties and groundwater quality in this karst-fissure aquifer system, drilling data, hydrochemical parameters, and δ²H and δ¹⁸O values of groundwater were analyzed. Multiple indications (Piper diagram, Gibbs diagram, Na⁺-normalized molar ratio diagram, chloro-alkaline index 1, mineral saturation index, and principal component analysis) were used to identify the primary sources of chemicals in the groundwater. Silicate weathering, oxidation of pyrite and chlorite, cation exchange reactions, and precipitation are the primary sources of dissolved chemicals in the igneous-fissure water. The most relevant parameters in the karst water are possibly from anthropogenic activities, and other chemicals are mostly derived from the dissolution of calcite and dolomite and cation exchange reactions. Notably, the chemical composition of the deep karst water from the karst basin is mainly influenced by the weathering of carbonate and cation exchange reactions and is less affected by human activities. The hydrogeochemical properties of groundwater in the karst hyporheic zone are influenced by the dissolution of carbonates and silicates, evaporation, and the promotion effect of dissolution of anorthite or Ca-containing minerals. Moreover, the smallest slope of the groundwater line from the karst hyporheic zone among all groundwater groups revealed that the mixing effects of evaporation, isotope exchange in water–rock interaction or deep groundwater recharge in the karst hyporheic zone are the strongest. The methods used in this study contribute to an improved understanding of the hydrogeochemical processes that occur in karst-fissure water systems and can be useful in zoning management and decision-making for groundwater resources. Full article