Search Results (741)

The Hajdúhát loess plateau in eastern Hungary has no perennial watercourse and overlies a drought-sensitive shallow aquifer, so irrigation supply security and allocation both constrain production. We coupled a dry-2018/wet-2020 MIKE Hydro River model of the East Main Canal (EMC) with a seventeen-year (2009–2025) MIKE SHE groundwater model, and a decision-support layer that couples conveyed-water allocation across sectors with a ranking of management responses. Calibration attains Moriasi Very Good bias-and-balance skill (mean |PBIAS| 1.59%/0.86%), with a head MAE of 1.431 m over 132 wells, and continuous validation reproduces measured discharge to within −7.7% bias over 2022–2025. Growing-season evapotranspiration (448 mm) exceeds precipitation (309 mm), leaving a 314 mm unsaturated-zone deficit; the dry-year canal terminus shows 34 of 92 no-flow days and a sustainability index of 0.09, against 0.34 when wet. A reconciled reach × sector balance and an isolating hydraulic test show the deficit is an allocation problem, not a conveyance limit. A Leopold/analytic-hierarchy-process ranking favors priority-ordered allocation over new capacity, and, in a two-objective time–quantity allocation, re-timing 8.57 × 10${}^6$ m${}^3$ of fish-pond filling into winter would remove the spring deficit without new infrastructure. Dry-year supply is thus a problem of allocation and timing as much as of capacity. Full article

Identification of recharge sources in the Mekelle area is controversial, as some studies indicate that precipitation is the only source of recharge, while others indicate the existence of inter-catchment/inter-basin groundwater transfers with the possibility of intermediate-to-regional flow system recharge sources. The objectives of this study were, therefore, to identify the sources of recharge, quantify the groundwater recharge and develop a local meteoric waterline (LMWL) for the Mekelle area using the stable isotopic compositions (δ¹⁸O and δ²H) of rainwater. To that end, 13 precipitation, 34 groundwater, and two surface water samples were analyzed for δ¹⁸O and δ²H signatures. Accordingly, the local meteoric water line (LMWL: δ²H = 6.78 δ¹⁸O + 9.83) was developed from ten monthly accumulated precipitation samples and three rainfall event samples. Moreover, the spatial variations in the isotopic compositions of the groundwater with respect to the LMWL showed the existence of three zones/groups with different groundwater flow conditions, namely, shallow, intermediate, and deep flow systems. Two groundwater recharge sources were also identified from the dual-isotope slope of the groundwater isotope lines with respect to the LMWL. Furthermore, the groundwater recharge was estimated to be 49 mm/year using the chloride mass balance (CMB) method. Full article

Landfill leachate circuits that operate without discharge, by recirculating aerated leachate onto the waste mass, are widespread in South-East Europe, yet their long-term behaviour is rarely documented with sample-level data. This study reports a six-year (2020–2025) seasonal monitoring campaign at a sanitary landfill in northern Serbia (alluvial aquifer of the Sava River, transboundary Danube basin) and re-examines it with a transparent multivariate protocol. Seventy-two leachate samples (collection well, aeration lagoon, sedimentation lagoon; n = 24 each, 30 parameters), 28 realised surface-water campaigns, and six years of groundwater summaries were evaluated by principal component analysis/factor analysis (PCA/FA, Varimax normalized), hierarchical cluster analysis, PERMANOVA, non-parametric paired tests and, for benchmarking, supervised machine learning. The pooled leachate model (n = 72; 21 variables; KMO = 0.700; Bartlett χ² = 956, p < 0.001) retained four factors by parallel analysis, explaining 61.6% of total variance; after rotation the factors accounted for 27.7%, 14.3%, 10.4%, and 9.3%. Factor 1 grouped organic load with particle-reactive metals (COD, BOD₅, Fe, Ni, Cr, As, Zn), Factor 2 a reduced sulfur–fluoride–BTEX signature, Factor 3 temperature-driven nitritation, and Factor 4 a nitrate–manganese redox contrast. Crucially, paired campaign-by-campaign comparison showed no removal of the dominant pollutants along the circuit. Median COD, BOD₅ and NH₄-N were not lower in the sedimentation lagoon than in the collection well, while pH rose from 8.08 to 8.75 (p < 0.001); only Cu, Pb, NO₃-N, and NO₂-N decreased significantly. The circuit therefore homogenises and concentrates dissolved load rather than removing it. Downstream surface water was significantly enriched in electrical conductivity (+110 µS/cm), total dissolved solids, NH₄-N, and NO₂-N relative to upstream (Wilcoxon, p < 0.05), and groundwater showed episodic conductivity up to 12,760 µS/cm and NH₄-N up to 102 mg/L. Cytotoxicity (MTT) confirmed biological relevance, with MRC-5 viability falling to 37% after 24 h exposure to 50 vol.% groundwater (Pw3) versus 60% in A549 cells. A random-forest classifier separated circuit units far better than PCA-based discrimination (76.4% versus 54.2% cross-validated accuracy) and distinguished the 2020–2021 pandemic period from 2022–2025 with 94.2% accuracy, a period effect also confirmed by PERMANOVA (R² = 7.2%, p < 0.001). The results indicate that closed-loop recirculation without an engineered discharge barrier transfers, rather than eliminates, contaminant load, and that after-care of such systems requires mass-balance monitoring and polishing treatment. Full article

The Weibei Plain, characterized by its complex stratified aquifer system and extensive brine resources, faces severe groundwater salinization. Unraveling the precise evolutionary mechanisms of diverse hydrochemical types across varying depths and geomorphological zones remains a significant challenge. This study synthesizes a multi-batch hydrochemical dataset with multi-isotopic tracers (δ²H, δ¹⁸O, δ¹¹B, δ⁸¹Br, δ³⁷Cl) to establish a comprehensive groundwater evolutionary model from the piedmont plain to the coastal marine plain. The results indicate distinct hydrochemical zonation governed by geographic geomorphology and historical marine transgressions. Salinization in transitional waters is primarily driven by physical mixing and reverse cation exchange rather than extreme evaporative fractionation. Crucially, isotopic mass balance definitively reveals that deep brine (depth > 60 m) originates not from modern seawater intrusion, but from the extreme surface evaporation of ancient paleo-seawater. This paleo-brine underwent profound isotopic exchange during its gravity-driven downward migration, evidenced by intense clay mineral adsorption (yielding extreme δ¹¹B enrichment up to 64.42‰) and secondary evaporite dissolution. Furthermore, the regional cone of depression formed by intensive brine extraction has profoundly altered deep hydrodynamics, inducing overflow and membrane ultrafiltration across massively thick clay aquitards. This process distinctly drives the isotopic fractionation observed in deep brackish waters. The analysis process in this study combines the isotope method with the regional geomorphological zoning, which can provide a reference for the analysis of groundwater evolution characteristics in other coastal aquifers. Full article

While continuously promoting agricultural water-saving and efficiency improvement, Ningxia is confronted with problems such as deepening groundwater tables and growing ecological vulnerability. Exploring the trade-off relationships and their evolutionary characteristics between socioeconomic development and water resource carrying capacity, as well as between water use efficiency improvement and groundwater-ecosystem maintenance, is of great significance for coordinated water resource governance in arid irrigation districts. Based on time-series data covering 2000–2024, this paper establishes a DPSIR evaluation model and constructs a progressive quantitative analytical framework coupling the entropy-weight-Tapio decoupling, rate-scissors difference and PLS-SEM models. During the study period, the growth rate of the response (R) dimension (13.76%) was far higher than that of the state (S) dimension (3.23%) from 2011 to 2020, confirming the objective existence of dual trade-offs. The two categories of trade-offs underwent a three-stage evolution of “latent-intensified-remediation”, showing the counter-intuitive feature of “effective total-volume control alongside continuous groundwater table deepening”. Hidden transmission barriers were identified for 2008–2016 (θ₁, θ₂ dropped to 0.46–1.32°): the transfer of water-saving dividends to industry caused groundwater extraction to rise rather than fall to a certain extent. PLS-SEM analysis reveals that structural lock-in acts as the core inhibiting factor for ecological protection. The total effect of socioeconomic development on ecology reaches 0.921, whereas structural lock-in produces a chained negative mediating effect of −0.192 by suppressing water use efficiency. Improvement in water use efficiency presents dual characteristics of overall ecological gain and localized groundwater-recharge loss. It can be concluded that engineering-only water-saving measures cannot balance water-intake reduction and recharge deficits. It is necessary to simultaneously advance low-water-consumption cropping-pattern restructuring, rigid enforcement of the 2.5 m ecological groundwater table threshold, and the substitution mechanism for saved-water volume between industry and agriculture, so as to build a coordinated “water-saving-recharge-ecology” regulation system. Full article

Central Asia is a global climate-change hotspot where future water availability remains uncertain, as hydrological forcing data are ambiguous and observations provide limited constraints on model parameters. We reassessed future runoff changes in the glacierized Ala-Archa basin by reducing model equifinality with a multi-objective calibration strategy that explicitly incorporates winter low-flow runoff, total runoff, snow cover fraction, and glacier mass balance. The calibrated model was used to project annual and seasonal river discharge under four Shared Socioeconomic Pathways. Results indicate a transition from a nival–glacial to a more pluvial-driven runoff regime. Rising temperatures advance the melt season, increase the proportion of liquid precipitation, and shift peak runoff from July to June. Although glacier and snowmelt contributions decline substantially as cryospheric storage shrinks, total annual runoff decreases only modestly by the late 21st century. This muted annual response reflects compensating effects from increased rainfall and a sustained rise in summer baseflow. Improved low-flow calibration suggests that increased groundwater recharge can partly offset meltwater losses, leading to a less severe summer discharge reduction than previously reported. Neglecting low-flow constraints may therefore overestimate future water scarcity in glacier-fed catchments. Full article

This study proposes a hybrid computational model for diagnosing such biases using groundwater observation data across Kazakhstan. The analytical dataset included 2402 georeferenced observations, including 492 natural springs from OpenStreetMap (OSM), 109 boreholes from OSM, and 1801 spatially filtered pseudo-absence observations. Springs and boreholes together formed 601 positive groundwater observations, while pseudo-absence samples represented a spatially filtered background level rather than confirmed groundwater absence. Each observation was characterized by 89 environmental predictors extracted from Google Earth Engine. The proposed hybrid observation source bias index (HOSBI) combines a normalized robust effect size based on the median absolute value of the Cliff delta, multivariate distribution divergence quantified using RBF-MMD, and spatially confirmed source distinctiveness. These components were assigned fixed weights of 0.40, 0.35, and 0.25 to emphasize statistical and distributional data while maintaining spatial validation. Spatial cross-validation achieved a balanced accuracy of 0.855 for distinguishing OSM sources from OSM wells and 0.846 for separating positive observations from background pseudo-absences. Climate showed the strongest source-related bias (HOSBI = 0.923), while Sentinel-1 SAR contributed the most to the contrast between positive and background data (HOSBI = 0.923). The proposed framework provides an interpretable and replicable preliminary assessment of source bias in heterogeneous geospatial datasets. Full article

This study assessed the effects of groundwater interacting with aggregate produced from steel slag, used as a ballast material in a waterproofing system protecting the road surface under high groundwater table conditions. Field investigations were carried out, with hydrochemical analyses of groundwater and water draining through the structure, mineralogical characterisation of the slag, and geochemical modelling using the PHREEQC programme with inverse modelling. The results showed that water flow through the slag aggregate caused strong alkalisation of the solution and changes in the concentrations of Ca, Mg, Na, Cl, sulphates and carbonate components. Inverse modelling enabled the identification of eight acceptable mass balance models. The main primary phases involved in the transformations were larnite, merwinite, mayenite, halite and, locally, slag glass. Their dissolution contributed Ca, Mg, Al, Si, Na and Cl to the solution. The increases in Na and Cl concentrations were interpreted primarily as the result of an external influx of road salt, rather than as an intrinsic property of the slag. The secondary products were dominated by amorphous silica, calcite, ettringite and brucite, indicating silica removal, carbonation, sulphate fixation and the partial immobilisation of Mg. The results confirm that slag aggregate remains geochemically active in contact with groundwater; however, simultaneous carbonation and secondary mineralisation favour the gradual stabilisation of the water–slag system. Full article

At Yuehai Lake, China, managed Yellow River diversion maintains open water while imposing a persistent hydraulic boundary on the shallow aquifer. We combined water balance, zonal Darcy estimation, a calibrated regulated-stage groundwater model, particle tracking, major ions, and stable isotopes. Yellow River diversion supplied 93.7% of quantified external inflows. Zonal Darcy and model leakage were 2.39 and 2.47 × 10⁶ m³ a⁻¹. Across the monitored stage range (1105.96–1106.42 m), modeled leakage was 2.41–2.53 × 10⁶ m³ a⁻¹; alternative upper-aquifer structures produced 1.91–3.02 × 10⁶ m³ a⁻¹ without reversing exchange or eliminating the mound. Particles from 441 lakebed cells moved a median 24.5 m over 1065 d, indicating slow near-shore advection. Selected-screen isotopes were consistent with evaporatively enriched lake-water influence, whereas major ions showed a distinct west–east shift from Ca–Mg–HCO₃ toward Na–SO₄ and Na–Cl facies. Yuehai Lake therefore functions as a regulated losing lake. Its salinity pattern likely reflects lake leakage, agricultural return flow, soil-salt mobilization, background saline groundwater, and restricted drainage. Management should integrate lake-stage, groundwater-flow, and salinity monitoring. Full article

Inland rivers in arid regions are important water resources that support ecosystem stability and human activities. This study comparatively investigated the hydrochemical characteristics, controlling factors, and irrigation suitability of six glacier-fed inland rivers along the southern margin of the Tarim Basin using hydrochemical analysis, Gibbs and Piper diagrams, ion-ratio analysis, principal component analysis (PCA), and PHREEQC inverse mass-balance modeling. The six rivers exhibited distinct hydrochemical characteristics despite their common origin in the Kunlun Mountains. Carbonate weathering dominated the Bostan and Nur rivers, while the Kaxi River exhibited relatively stable hydrochemical characteristics mainly associated with rock weathering. In contrast, evaporite dissolution and evaporative concentration exerted stronger influences on the Uruksayi and Buzang rivers, which also showed more pronounced longitudinal variations in major ion concentrations. The Keriya River showed an overall transition from silicate-weathering-dominated conditions in the upper reaches toward stronger evaporite dissolution and evaporative concentration downstream. PHREEQC inverse mass-balance modeling suggested that halite dissolution, gypsum dissolution, dolomite dissolution, calcite precipitation, and cation exchange contributed to the hydrochemical evolution of the Keriya River. Several abrupt variations in ion concentrations were observed along the river courses, suggesting that localized processes, including tributary mixing, groundwater inputs, or potential anthropogenic influences, may contribute to these hydrochemical changes. PCA extracted two principal components explaining 86.0% of the total variance. PC1 (70.5%) represented overall ion enrichment and mineralization, whereas PC2 (15.5%) reflected carbonate-related hydrochemical variations. Irrigation suitability assessment showed that all rivers exhibited low sodium hazards, while salinity was the main factor limiting irrigation suitability in the middle and lower reaches of the Keriya River and in the Uruksayi and Buzang rivers. This study improves the understanding of hydrochemical evolution and water quality assessment of arid inland rivers and provides scientific support for sustainable water resource management and oasis ecosystem protection in the southern Tarim Basin. Full article

Agricultural systems face heightened risks from extreme weather events and water insecurity. Producers commonly use irrigation ponds to secure or improve crop yields. The hydrology and storage efficiency of irrigation ponds in the Willamette Valley, Oregon, USA, are not well understood. This study evaluated the hydrological interactions of a tile-drain-fed irrigation pond. A water balance approach was applied over the irrigation season using weather data, evaporation estimates, metered irrigation withdrawals, and bathymetry analysis for pond stage–volume estimates to quantify water budget components. Irrigation withdrawals were the largest output, with 75% of effective pond storage utilized, followed by evaporation (24.5%). Evaporation far exceeded precipitation over the same period. The unaccounted-for proportion of the water balance was negligible, indicating that net drain tile inflows and groundwater exchange had a minimal impact on seasonal irrigation water availability and seepage losses. This study provides an example for measuring water balance components and assessing water input–output relationships of an irrigation pond within a headwaters stream and catchment (<5 ha) of an important agricultural corridor in the Pacific Northwest region in the USA. The study methodology can be replicated in other similar agricultural areas with irrigation ponds worldwide. Findings from this study can be used by farmers, irrigation districts, and other stakeholders to better inform irrigation planning and water management decisions for similar site conditions. Full article

The increasing accumulation of industrial solid waste and worsening groundwater pollution pose significant environmental challenges. This study introduces a Si-Ca-Fe-based ceramsite from solid wastes with exceptional Cd adsorption capacity. A comprehensive investigation was conducted on the phase evolution, adsorption properties, and underlying mechanisms of the synthesized ceramsite. The findings revealed that the optimum sintering temperature for the ceramsite, characterized by austenite and pyroxene, was 1140 °C, which balanced mechanical strength and Cd adsorption capacity. Remarkably, the ceramsite (6.0 g) was immersed in 5 L of a Cd(NO₃)₂ solution for 21 h under initial conditions (pH = 7 and temperature = 20 °C), and the ceramsite exhibited a notable Cd adsorption capacity of 5.47 mg/g (initial Cd concentration: 53.42 mg/L), with a maximum theoretical capacity of 9.32 mg/g according to the Langmuir isotherm. An in-depth analysis of adsorption kinetics, phase composition, and EDS data indicated that the primary adsorption mechanism was the zero-valent iron (ZVI) corrosion-driven reaction. This ZVI formed in situ under reducing conditions during the ceramsite’s preparation and subsequently aided in the precipitation of Cd(OH)₂. Additionally, the honeycomb structure of the ceramsite, containing fine pores (approximately 2–5 μm), enhanced physical adsorption via capillary action, further improving Cd removal. These insights offer a robust foundation for crafting efficient, solid waste-derived ceramsite tailored for heavy metal extraction from polluted water, presenting a compelling approach to concurrent waste recycling and environmental remediation. Full article

The Dongting Basin in central China has experienced increasing pressure on water resources due to intensified industrial and agricultural activities and increasingly frequent droughts. Therefore, reliable estimates of groundwater recharge are essential for evaluating the sustainability of groundwater resources in this region. An integrated approach combining the water table fluctuation (WTF), groundwater age, and chloride mass balance (CMB) was applied to estimate groundwater recharge in the Quaternary aquifer of the Zishui Plain, a sub-basin of the Dongting Basin. The mean recharge values derived from these methods were 268.2, 226.2, and 167.03 mm/year, respectively. The corresponding mean R/P ratios were 19.4%, 16.5%, and 12.2%. Differences between the recharge estimates reflect methodological differences among the three approaches and suggest that lithology, river seepage, and human activities contribute to the observed spatial variability in groundwater recharge. The WTF method generally produced the highest recharge estimates, whereas the CMB and groundwater age methods tended to provide lower estimates because of their respective methodological limitations. The integrated application of these methods may provide a more comprehensive assessment of groundwater recharge and may serve as a useful reference for groundwater management in the Dongting Basin. Full article

To address the challenge of balancing food production, groundwater protection, and economic sustainability in agricultural systems, this study developed a novel multi-objective optimization framework integrating an Extreme Learning Machine (ELM)-based surrogate model. An irrigation–fertilization–economy (IFE) model was established to evaluate region-specific agricultural adjustment strategies under four scenarios: baseline adjustment, flexible restructuring, production reduction and profit-oriented expansion scenarios. The optimization results were subsequently used to assess the impacts of agricultural production regulation on groundwater nitrate concentrations in the study area. The results showed that the IFE model consistently favored the conversion from wheat to maize cultivation across all regions, because maize requires less irrigation and fertilizer inputs while maintaining relatively high net profits. However, the optimal strategies varied among regions: Pingdu and Jiaozhou showed greater economic potential for production expansion, whereas regions with lower economic potential were more suitable for reducing high-input crop cultivation. During the 2020–2030 prediction period, nitrate concentrations exhibited substantial interannual variations. Reducing the overall production scale shifted nitrate concentrations approximately 6% closer to the 30–50 mg/L range over the decade, but this limited environmental benefit was accompanied by substantial short-term economic losses. Considering both environmental impacts and economic viability, the optimization results suggest that moderate agricultural expansion could be acceptable provided that environmental burdens are effectively managed. Full article

Soil and groundwater contamination across multiple plots in industrial parks is an important environmental management challenge. Because plots often differ in contamination characteristics and remediation requirements, remediation decision-making needs to generate sustainability-oriented alternatives that account for explicit management preferences and trade-offs among carbon emissions, remediation duration, and cost. Although technology screening for individual contaminated plots has been widely investigated, how to use plot-level screening results to support the selection of multi-plot remediation alternatives under multiple objectives remains insufficiently addressed. This study developed a preference-guided multi-objective decision framework for selecting remediation alternatives in contaminated industrial parks. The framework first generates cross-plot remediation alternatives by assigning one feasible technology to each plot and removes alternatives that violate technological compatibility or project-level engineering constraints. It then identifies Pareto non-dominated alternatives using NSGA-II, retains preference-consistent alternatives through LO-based filtering, and selects the final recommendation using ideal-point distance comparison. The framework was applied to a five-plot contaminated industrial park in northern China. Compared with the LO and NSGA-II benchmarks, the hybrid NSGA-II–LO model selected less imbalanced alternatives that retained the preferred-objective advantage while improving the balance among the remaining objectives. The results show that management priorities can substantially affect remediation technology allocation across plots and that preference screening can support the adjustment of remediation alternatives when low-carbon targets, remediation schedules, or budget constraints change. This study provides an operational decision framework for translating plot-level technology screening into sustainability-oriented multi-plot remediation decision-making. Full article