Search Results (283)

Reusing and recycling treated wastewater is a sustainable approach to meet the growing demand for clean water, ensuring its availability for both current and future generations. Wastewater can be treated in such advanced ways that it can be used for industrial operations, recharging groundwater, irrigation of fields, or even manufacturing drinkable water. This strategy meets growing water demand in water-scarce areas while protecting natural ecosystems. Treated wastewater is both a resource and a challenge. Though it may be nutrient-rich and can increase agricultural output while showing resource reuse and environmental conservation, high treatment costs, public acceptance, and contamination hazards limit its use. Proper treatment can reduce these hazards, safeguarding human health and the environment while enhancing its benefits, including a stable water supply, nutrient-rich irrigation, higher crop yields, economic development, and community resilience. On the one hand, inadequate treatment may lead to soil salinization, environmental degradation, and hazardous foods. Examining the dual benefits and risks of using treated wastewater for agricultural irrigation, this paper investigates the complexities of its use as a valuable resource and as a potential hazard. Modern treatment technologies are needed to address these difficulties and to ensure safe and sustainable use. If properly handled, treated wastewater reuse has enormous potential for reducing water scarcity and expanding sustainable agriculture as well as global food security. Full article

The hydrochemical characteristics and evolution mechanisms of groundwater are critical for accurately understanding the input–output budget of hydrochemical constituents in pristine groundwater. However, few studies have analyzed the changes in mineral precipitation and dissolution equilibrium along the groundwater flow path, especially in arid regions. This study integrated hydrochemical analysis, stable isotopes, and inverse hydrochemical modeling to identify groundwater recharge sources, hydrochemical evolution, and controlling mechanisms in an arid endorheic watershed, northwestern China. A stable isotope signature indicated that groundwater is primarily recharged by high-altitude meteoric precipitation and glacial snowmelt. The regional hydrochemical type evolved from HCO₃·Cl-Ca·Mg·Na types in phreatic aquifers to more complex HCO₃·Cl-Ca·Mg Na and HCO₃·Cl-Na Mg types in confined aquifers and a Cl-Mg·Na type in high-salinity groundwater. The dissolution of halite, gypsum, calcite, K-feldspar, and albite was identified as the primary source of dissolved substances and a key factor controlling the hydrochemical characteristics. Meanwhile, hydrochemical evolution is influenced by cation exchange, mineral dissolution–precipitation, and carbonate equilibrium mechanisms. Inverse hydrochemical modeling demonstrated that high-salinity groundwater has experienced intensive evaporation and quantified the transfer amounts of associated minerals. This study offers deeper insight into hydrochemical evolution in the Golmud River watershed and elucidates mineral transport and enrichment mechanisms, providing a theoretical basis for investigating hydrochemical metallogenic processes. Full article

To provide safe drinking water in contaminated hydrogeological environments, it is essential to have precise geochemical information on contamination hotspots. In this study, Geographic Information System (GIS) and multivariate statistics were utilized to analyze the spatial patterns, occurrence, and major factors controlling uranium (U) concentrations in groundwater. The global and local Moran’s I indices were utilized to detect hotspots and cool spots of U distribution. The substantial positive global Moran’s I index (at a p-value of 0.05) revealed a geographical pattern in U occurrences. The spatial clusters displayed patterns of drinking water source with U concentrations below and above the WHO limit, categorized as “regional U cool spots” and “regional U hotspots”, respectively. Spatial autocorrelation plots revealed that the high–high potential spatial patterns for U were situated in the northeastern region of the study area. As the order of queen’s contiguity increased, prospective low–high spatial patterns transitioned from the Faridkot district to the Muktsar district for U. Further, the multivariate statistical analysis methods such as correlation and principal component analysis (PCA) plots revealed substantial positive associations (p-value < 0.05) between U and total dissolved solids (TDS), salinity (SL), bicarbonate (HCO₃⁻), and sodium (Na) in groundwater from both shallow and deeper depth, indicating that these water quality parameters can significantly influence the occurrence of U in the groundwater. The output of the random forest model shows that among the groundwater parameters, TDS is the most influential variable for enrichment of U in groundwater, followed by HCO₃⁻, Na, F⁻, SO₄²⁻, Mg, Cl⁻, pH, NO₃⁻, and K concentrations. Additionally, the results of health risk assessment indicate that 47.86% and 41.3% of samples pose risks to children and adults, respectively, due to F⁻−contamination. About 93.49% and 89.14% of samples pose a risk to children and adults, respectively, due to U contamination, whereas 51.08% and 39.13% of samples pose a risk to children and adults, respectively, from NO₃⁻ contamination. The current data indicates an urgent need to create cost-effective and efficient remediation techniques for groundwater contamination in this region. Full article

The coastal zone presents complex hydrodynamic interactions among inland groundwater, reservoir water, and intruding seawater, with important implications for ecosystem functioning and water quality. However, the relative roles of hydraulic connectivity and seawater-driven salinity gradients in shaping microbial communities at the aquifer–reservoir interface remain unclear. Here, we integrated hydrochemical analyses with high-throughput 16S rRNA gene sequencing to investigate bacterial community composition, assembly processes, and co-occurrence network patterns across groundwater_in (entering the reservoir), groundwater_out (exiting the reservoir), and reservoir water in a coastal system. Our findings reveal that seawater intrusion exerts a stronger influence on groundwater_out, leading to distinct chemical profiles and salinity-driven environmental filtering, whereas hydraulic connectivity promotes greater microbial similarity between groundwater_in and reservoir water. Groundwater samples exhibited higher alpha and beta diversity compared to the reservoir, with dominant taxa such as Comamonadaceae, Flavobacteriaceae, and Rhodobacteraceae serving as indicators of seawater intrusion. Community assembly analyses showed that homogeneous selection predominated, especially under strong salinity gradients, while dispersal limitation and spatial distance also contributed in areas of reduced connectivity. Key chemical factors, including TDS, Na⁺, Cl⁻, Mg²⁺, and K⁺, strongly shaped groundwater communities. Additionally, groundwater bacterial networks were more complex and robust than those in reservoir water, suggesting enhanced resilience to salinity stress. Collectively, this study demonstrates that salinity gradients can override the effects of hydraulic connectivity in structuring bacterial communities and their networks at coastal interfaces. Our findings provide novel microbial insights relevant for understanding biogeochemical processes and support the use of microbial indicators for more sensitive monitoring and management of coastal groundwater resources. Full article

A vital step for any hydrochemical assessment is properly carrying out quality assurance and quality control (QA/QC) techniques to evaluate data confidence before performing the assessment. Understanding the processes governing groundwater evolution in coastal aquifers is critical for managing freshwater resources under increasing anthropogenic and climatic pressures. This study reassesses the hydrochemical and isotopic data from the Deep Confined Aquifer System (DCAS) in the Jiangsu Coastal Plain, China, by firstly applying QA/QC protocols. Anomalously high Fe and Mn concentrations in several samples were identified and excluded, yielding a refined dataset that enabled a more accurate interpretation of hydrogeochemical processes. Using hierarchical cluster analysis (HCA), principal component analysis (PCA), and stable and radioactive isotope data (δ²H, δ¹⁸O, ³H, and ¹⁴C), we identify three dominant drivers of groundwater evolution: water–rock interaction, evaporation, and seawater intrusion. In contrast to earlier interpretations, we present clear evidence of active seawater intrusion into the DCAS, supported by salinity patterns, isotopic signatures, and local hydrodynamics. Furthermore, inconsistencies between tritium- and radiocarbon-derived residence times—modern recharge indicated by ³H versus Pleistocene ages from ¹⁴C—highlight the unreliability of previous paleoclimatic reconstructions based on unvalidated datasets. These findings underscore the crucial role of robust QA/QC and integrated tracer analysis in groundwater studies. Full article

Wetlands play a crucial role in water purification, climate regulation, and biodiversity conservation. However, the Xianghai wetlands (situated in Tongyu County, Jilin Province, China) have experienced severe ecological degradation due to natural factors and unsustainable human activities, leading to declining groundwater levels and intensified salinity issues. To address these problems, this study aims to optimize ecological water replenishment strategies for the Xianghai nature reserve by integrating groundwater numerical simulation, surrogate modeling (convolutional neural network–long short-term memory neural network, CNN-LSTM), and intelligent optimization algorithms (Particle Swarm Optimization, PSO). During the design of the water replenishment scheme, the objective function maximizes the replenishment volume while considering the secondary salinization of soil in the reserve and its surrounding areas as a constraint. The results show that the surrogate model established using the convolutional neural network–long short-term memory neural network achieved high accuracy, with R² values of 0.9996 and 0.9962 and MREs of 0.0023 and 0.0089 for training and validation sets, respectively; Compared to the random replenishment scheme, the optimized water replenishment scheme significantly reduces secondary salinization. After 10 years water replenishment, the optimized scheme exhibited a 2 km² reduction in the salinized area compared to the randomized scheme, with the degree of salinization being reduced from moderate to mild. This method improves ecological sustainability and can be adapted to meet local water use demands. This simulation-optimization method provides an effective approach for designing water replenishment schemes that address secondary salinization. Full article

This study was conducted in the Harran Plain within the framework of the Southeastern Anatolia Project (GAP) in Türkiye to evaluate the vulnerability of groundwater to contamination, with a special emphasis on the high salinity conditions attributed to agricultural and rural practices. The region is notably challenged by salinization resulting from intensive irrigation and insufficient drainage systems. The DRASTIC framework was used to assess groundwater contamination vulnerability. The DRASTIC framework parameters were numerically integrated using both the original DRASTIC framework and its modified version, serving as the basis for subsequent predictive analytics and soft computing model development. The primary aim was to determine the most effective predictive model for groundwater contamination vulnerability in salinity-affected areas. In this context, various models were implemented and evaluated, including artificial neural networks (ANNs) with varied hidden layer configurations, four different regression-based methods (MARS, TreeNet, GPS, and CART), and three classical regression analysis approaches. The modeling process utilized 24 adjusted vulnerability indices (AVIs) as target variables, with the dataset partitioned into 58.34% for training, 20.83% for validating, and 20.83% for testing. Model performance was rigorously assessed using various statistical indicators such as mean absolute error, root mean square error, and the Nash–Sutcliffe efficiency coefficient, in addition to evaluating the predictive AVIs through spatial mapping. The findings revealed that the ANNs and TreeNet models offered superior performance in accurately predicting groundwater contamination vulnerability, particularly by delineating the spatial distribution of risk in areas experiencing intensive agricultural pressure. Full article

Groundwater is the main source of water for both domestic and agricultural use in arid regions. This study assessed the hydrogeochemical characteristics and suitability of groundwater for drinking and irrigation in Kenya’s Ewaso Ng’iro–Lagh Dera Basin. A total of 129 borehole groundwater samples were collected and analyzed for pH, electrical conductivity (EC), total hardness, and major ions. The groundwater was found to be mostly neutral to slightly alkaline and ranged from marginal to brackish in salinity. The dominant water type is Na-HCO₃, with the ionic order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > Cl⁻ > SO₄²⁻ > NO₃⁻. Mineral saturation indices indicate that the water is undersaturated with gypsum and anhydrite but is saturated with calcite, dolomite, and aragonite. Groundwater chemistry is primarily influenced by ion exchange, the mixing of fresh and paleo-saline water, and rock weathering processes. The water quality index (WQI) reveals that 80.5% of groundwater is suitable for drinking. The rest have high levels of sodium, EC, and bicarbonate. Thus, they are not suitable. The irrigation water quality index (IWQI) places most samples in the moderate-to-severe restriction category due to high salinity and sodicity. These findings highlight the importance of properly treating groundwater before use. Full article

Groundwater is a critical freshwater resource, yet its quality is increasingly threatened by anthropogenic activities, particularly in urbanized regions. This study employs geospatial analysis to evaluate the spatiotemporal variability of groundwater quality across 11 Watershed Management Areas (WMAs) in northern New Jersey, from 1999 to 2016. Using specific conductance (SC) as a proxy for salinity, we applied Ordinary Kriging interpolation to estimate SC values in unmonitored locations, leveraging data from 295 shallow wells within the New Jersey Ambient Groundwater Quality Monitoring Network. The results reveal significant spatial heterogeneity in groundwater quality, strongly associated with land use and road density. The Northeast water region, characterized by high urbanization and extensive road networks, exhibited the poorest water quality, with salinity levels exceeding the 750 μS/cm threshold for freshwater in WMAs such as Lower Passaic (WMA-4) and Hackensack (WMA-5). In contrast, the Northwest region, dominated by agricultural and undeveloped land, maintained better water quality. Temporal analysis showed a worrying decline in freshwater coverage, from 80% in 1999–2004 to 74% in 2014–2016, with deicing salts and aging sewer infrastructure identified as major contamination sources. The study highlights the efficacy of Kriging and GIS tools in mapping groundwater quality trends and highlights the urgent need for targeted water management strategies in vulnerable regions. These findings provide policymakers and stakeholders with actionable insights to mitigate groundwater degradation and ensure long-term freshwater sustainability in northern New Jersey. Full article

With an increasingly more urbanised global population, surface water and groundwater resources are being/have become outpaced by growing demand. The oceans could address this pertinent scarcity issue, once their high-salinity content is removed. Water desalination could thus be a crucial pathway towards addressing global water scarcity. However, conventional desalination is known to be highly energy-intensive, with limited scalability and potentially significant negative environmental impacts. Multi-criteria Decision Making (MCDM) presents a novel approach towards sustainable water desalination based on sustainability-related criteria. The Fuzzy Analytical Hierarchy Process (FAHP) was implemented to determine the most optimal small-scale, modularised, and remote reverse osmosis (RO) desalination plant configurations. Twelve configurations were assessed, based on four plant capacities (50, 100, 150, and 200 m³/day) and three diesel-to-solar photovoltaic energy configurations (100–0%, 75–25%, and 60–40%). The hybridised diesel-to-solar configurations were generally ranked higher, particularly when less reliant on diesel, and at small(er) capacities, in terms of the criteria: sustainability, overall efficiency, and standalone potential while maintaining competitive costs. This can likely be attributed to their relatively lower fuel and energy consumption and associated costs. Further research should aim to consider additional criteria, such as battery cost, as well as life cycle assessments that include transportation-related costs/emissions. Full article

Large-scale inter-basin water transfer is an important means to alleviate the pressure on water resources in water shortage regions. However, the long-term impacts of inter-basin transfers on the regional water–salt balance and associated land productivity remain poorly understood, especially in salt-affected arid environments. To fill this gap, the core objective of this study was to reveal the implications of inter-basin water transfer on soil salinity and sodicity and the crop yield response under different irrigation practices. We conducted a case study on the Karamay irrigation district (KID), an artificial oasis with a 30-year history of inter-basin water transfer in northwestern China, using trend and correlation analyses, water–salt balance analyses, and salt-controlled yield reduction functions as well as field comprehensive measurements over 1996–2023. The results indicate that soil salinity and sodicity profiles, overall, exhibited a clear vertical stratification under both the early and late crop growing stages, and the degree of the soil salinization was decreasing, and the area of non-saline land was increasing significantly from 1996 to 2023 in the KID. Owing to the lack of salt-washing water and the poor irrigation water quality, the water-saving irrigated farmland was in the slight salt-aggregating state in the topsoil layer, while the other soil layers were in the salt-expelling or salt-equilibrating state in the KID. The profile distribution and exchange fluxes of soil salinity and sodicity are mainly characterized by climate, irrigation, and groundwater dynamics, as well as the plant salt tolerance, soil properties, and agronomic management which also influence the soil salt accumulation. With the transformation of irrigation schemes from traditional flood irrigation to modern water-saving irrigation during 1996–2023, the impact of soil salinity on relative crop yields has been substantially reduced in the KID, especially for salt-sensitive crops. This revealed that optimizing the drainage facilities, precise field irrigation and fertilization measures, and rational crop selection and agronomic practices are vital for high-quality development in the KID. Capitalizing on these research findings, we would provide effective directives for maintaining the sustainability of agricultural development in other similar inter-basin water transfer zones in the world. Full article

Inland saline wetlands in the Ebro Basin (Spain) are protected by international regulations but are also threatened by the expansion of animal farms. We studied the input–output budgets of N from animal farms in four catchments of wetlands in the central Ebro Basin designated as Nitrate Vulnerable Zones. We used the N produced in animal farms as inputs and the N extracted by the crops on which manures and slurries are applied as outputs in each catchment. The balances considered the regulations concerning the slope of land where animal excreta may be applied and the doses of application. At a detailed scale, we applied the Water Erosion Prediction Program (WEPP) to the Farnaca catchment to assess the runoff and nutrients arriving to its wetland. While the Bujaraloz-Sástago basin showed a high excess of N load, in the Gallocanta basin, N extraction by crops was significantly higher than the N produced by the animal farms. Despite this lack of surplus of N from animal excreta, the groundwaters in the Gallocanta catchment are polluted by nitrates. The emphasis on N from animal farms in plans to prevent water pollution is missing the role of mineral fertilizers as the sources of pollution in basins with small N loads from animal farms. Agricultural plots in the Farnaca catchment produce significant amounts of sediments and nutrients that eventually pollute the wetland. Modelling approaches at detailed scales are required to assess the flows of materials to individual wetlands. Full article

This study investigated soil salinization processes in the Pavlodar region of Kazakhstan by comparing key soil parameters—namely, electrical conductivity (EC), pH, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) under irrigated and non-irrigated conditions across different agro-climatic zones and soil types (Haplic Chernozems, Haplic Kastanozems). The focus was on understanding the effects of irrigation and natural factors on soil salinization. Statistical analysis, including descriptive statistics and significance testing, was employed to evaluate differences between soil types, locations, and management practices. The research revealed secondary salinization (EC > 2 dS/m, ESP > 15%) in the topsoil of irrigated Haplic Kastanozems soils in the central Aksu district. This degradation was markedly higher than in non-irrigated plots or irrigated Haplic Chernozems in the northern Irtysh district, highlighting the high vulnerability of Haplic Kastanozems soils under current irrigation management given Aksu’s climatic conditions, which are characterized by high evaporative demand (driven by summer temperatures) and specific precipitation patterns that contribute to soil moisture deficits without irrigation. While ESP indicated sodicity, SAR values remained low. Natural factors, including potentially saline parent materials and likely shallow groundwater dynamics influenced by irrigation, appear to contribute to the observed patterns. The findings underscore the need for implementing optimized irrigation and drainage management, particularly in the Aksu district, potentially including water-saving techniques (e.g., drip irrigation) and selection of salt/sodicity-tolerant crops. A comprehensive approach integrating improved water management, agronomic practices, and potentially soil amendments is crucial for mitigating soil degradation and ensuring sustainable agriculture in the Pavlodar region. Further investigation including groundwater monitoring is recommended. Full article

Rapid urbanization and climate change are the driving forces behind changing the urban landscape and affecting natural resources and the environment, particularly in the megacities of arid regions. Many of these cities face an acute water crisis leading to over-exploitation of groundwater resources. This over-exploitation has led to the depletion of aquifers, land infertility, saline intrusion, land subsidence, and harm to hydrological ecosystems. Globally, numerous studies have documented the potential of groundwater recharge (GWR) using GIS and remote sensing techniques. However, its practical application in a landscape context for sustainable urban and regional development is underexplored. In this study, we developed the landscape-based GWR concept by conducting a case study of Karachi city (Pakistan). We took physical landscape (surface and sub-surface) features and groundwater recharge potential as a base for design and planning to improve groundwater recharge and urban landscape. Moreover, we highlighted the added values of this approach besides recharging the depleted ground hydrological conditions and improving the urban landscape condition (i.e., social–ecological inclusiveness, sustainable future development, and interdisciplinary collaboration). The results indicated a negative impact of urbanization on groundwater recharge, especially in the alluvial zones and river valleys, underscoring the need for a spatial approach to safeguard GWR and guide development. Through this study, we propose that landscape-based GWR can be one of the potential solutions not only for the critical water crisis faced by rapidly urbanizing arid megacities but also for improving the overall quality of life and urban landscape. Furthermore, this holistic approach toward groundwater recharge can guide future urban development patterns, preservation of high groundwater recharge potential sites, and evolution toward sustainable development in arid regions where groundwater is the most significant yet vulnerable resource. Full article

Fluoride-enriched geothermal groundwater poses chronic health risks (e.g., dental and skeletal fluorosis) through prolonged exposure; nevertheless, hydrochemical-driven factors and the genetic mechanism of fluoride enrichment in such systems remain inadequately identified. This study employed hydrochemical characterization, isotopic tracing, and health risk models to elucidate the genetic mechanism of fluoride-enriched geothermal groundwater. The key findings reveal the following. (1) Geothermal groundwater (Cl-Na type; TDS 90–345 mg/L; pH 6.25–7.42) contrasts with alkaline river water (pH 7.48–8.05; SO₄-Na/HCO₃-Na) and saline seawater (TDS 23.9–28.2 g/L). Stable isotopes (δD, δ¹⁸O) confirm atmospheric precipitation recharge with an elevation of 69–635 m. (2) The Self-Organizing Map algorithm categorized 30 geothermal samples into three groups: Cluster I—low temperature and pH, high TDS; Cluster II—high temperature, low F⁻ concentration; and Cluster III—low TDS, and high pH and F⁻ concentration. (3) Fluoride enrichment in Cluster III originated from the evaporite/fluorite dissolution under alkaline conditions and cation exchange interactions, while the inhibition of CaF₂ dissolution by reverse cation exchange limited the accumulation of F⁻ in Cluster II and Cluster III samples. (4) Health risks disproportionately affect children (80% high risk) and women, necessitating pre-use defluorination. Full article