Water

22 pages, 36819 KB

Open AccessArticle

Research on Pressure Fluctuation and Vortex Evolution Characteristics in Pump-Turbine Under Load-Rejection Condition

by Lei Deng, Wenfu Han, Yuhao Yan, Xuezhi Zhou and Zhengwei Wang

Water 2026, 18(14), 1748; https://doi.org/10.3390/w18141748 - 19 Jul 2026

During load rejection in pumped-storage power stations, the rotational speed of the pump-turbine increases abruptly. The consequent structural deterioration of the internal flow induces high-amplitude hydraulic excitations, posing a serious threat to the operational stability of the unit. This study investigates a Francis [...] Read more.

During load rejection in pumped-storage power stations, the rotational speed of the pump-turbine increases abruptly. The consequent structural deterioration of the internal flow induces high-amplitude hydraulic excitations, posing a serious threat to the operational stability of the unit. This study investigates a Francis pump-turbine to elucidate its flow evolution and instability mechanisms during load rejection. The fluid is modeled as weakly compressible water to capture finite pressure wave propagation. Dynamic mesh simulates guide vane closure, while vortex identification and short-time Fourier transform analyze transient pressure pulsations. The results indicate that the transient process can be sequentially divided into four typical stages—turbine mode, turbine-braking mode, reverse-pump mode, and return-to-turbine mode—to account for the most critical periods during the load rejection transient. The unit exhibits the poorest stability near the maximum rotational speed (443.34 r/min), where flow reversal and the full development of vortex structures significantly amplify fluctuations in hydraulic thrust. The vaneless space is identified as the primary source of pressure pulsations, whose characteristics are dominated by rotor–stator interaction mechanisms, and such disturbances decay rapidly in the downstream direction. Under turbine-braking and reverse-pump conditions, vortex rings, backflow, and asymmetric vortex structures generated within the spiral casing collectively contribute to the severe deterioration of the internal flow field quality. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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23 pages, 2731 KB

Open AccessArticle

Experimental and Numerical Study of Flow over the Weir–Flume Combination Facility

by Fan Yang, Gang Ling, Jichao Yang, Hui Wang, Yuxiang Ba, Xingjiao Yu, Wene Wang and Xiaotao Hu

Water 2026, 18(14), 1747; https://doi.org/10.3390/w18141747 - 19 Jul 2026

Abstract

The weir–flume combination facility is a type of river flow-measurement structure consisting of a flow weir and a Crump weir, designed to integrate flow measurement and upstream backwater regulation, while incorporating a central flume intended to provide a potential passage for aquatic organisms. [...] Read more.

The weir–flume combination facility is a type of river flow-measurement structure consisting of a flow weir and a Crump weir, designed to integrate flow measurement and upstream backwater regulation, while incorporating a central flume intended to provide a potential passage for aquatic organisms. This study proposes a novel combined weir–flume structure and systematically validates its hydraulic performance through integrated physical experimentation and high-fidelity numerical simulation. Laboratory tests across a flow range of 5–79 L/s revealed longitudinal water surface profiles and Froude number (Fr) distributions. The study findings show that: (1) As the flow increases, the flow regime of the combination facility transitions from flume flow to weir flow, with the critical transition point at a relative water depth of 0.885. (2) The RNG k-ε turbulence model in Flow-3D software (v11.2, Flow Science, Inc., Santa Fe, NM, USA) effectively simulates the flow movement in the weir–flume combination facility, with water depth simulation results closely matching the measured values, and the maximum relative error not exceeding 5%. (3) The Fr and flow velocity in the weir–flume combination facility first increase and then decrease along the length, forming a large, thin water layer area downstream of the facility, where both Fr and flow velocity reach their maximum values. (4) Flow measurement formulas for flume flow and weir flow are obtained through data fitting, with relative errors between the calculated values and measured flow rates being less than 3%. The present study focuses on the hydraulic performance and flow measurement capability of the proposed facility. Although the structural configuration is intended to facilitate ecological passage, its ecological effectiveness was not evaluated and requires further investigation in future studies. Full article

(This article belongs to the Special Issue Advanced Technology in Agricultural Water-Saving Irrigation)

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57 pages, 9897 KB

Open AccessReview

Electro-Driven Membrane Separations for Sustainable Bio-Based Chemical Recovery: Energetics, Selectivity Engineering, Scale-Up Challenges, and Industrial Translation

by Akeem Adeyemi Oladipo

Water 2026, 18(14), 1746; https://doi.org/10.3390/w18141746 - 18 Jul 2026

Abstract

The economic viability of circular biorefineries is fundamentally constrained by the energetic and thermodynamic limits of conventional downstream processing. This critical review examines the paradigm shift toward electro-driven membrane separations, establishing them not merely as alternative filtration devices, but as active, programmable electrochemical [...] Read more.

The economic viability of circular biorefineries is fundamentally constrained by the energetic and thermodynamic limits of conventional downstream processing. This critical review examines the paradigm shift toward electro-driven membrane separations, establishing them not merely as alternative filtration devices, but as active, programmable electrochemical interfaces. Moving beyond classical bulk-desalination models, the analysis elucidates the complex reactive-transport physics governing bio-based chemical recovery, where localized pH modulation, electrostatic gating, and field-induced speciation dictate molecular discrimination. The manuscript critically benchmarks the inescapable macro-scale thermodynamic tradeoff among interfacial selectivity, volumetric productivity, and specific energy consumption (kWh/kg). Furthermore, it evaluates the integration of active 2D nanoconfined materials (e.g., MXenes) and rigorously critiques the severe performance degradation modes—specifically electro-biologically coupled fouling and anodic oxidation—that paralyze industrial scale-up. Ultimately, this review outlines a strategic mandate for the fully electrified biorefinery, where continuous in situ product recovery, artificial intelligence-guided module design, and autonomous cyber-physical control systems converge to eliminate legacy thermal unit operations and seamlessly integrate biomanufacturing with decarbonized electrical grids. Full article

(This article belongs to the Special Issue Advanced Membrane Technologies for Recovery of Bio-Based Chemicals from Aqueous Systems)

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29 pages, 6239 KB

Open AccessArticle

SPEI-Based Drought Frequency, Intensity, and Duration from CMIP6 Models Under SSP1-2.6 and SSP5-8.5 Across Tropical–Subtropical Monsoon Asia

by Maochou Liu, Wenxiang Wu, Ziyi Zhang, Xinshuai Ren, Ke Wang, Jiahui Cheng, Bo Yang and Jin Geng

Water 2026, 18(14), 1745; https://doi.org/10.3390/w18141745 - 18 Jul 2026

Abstract

Tropical–subtropical monsoon Asia faces pronounced hydroclimatic change under future warming, yet the regional patterns and emission scenario dependence of drought risk remain unclear. Using a 14-member CMIP6 multi-model ensemble from the NEX-GDDP-CMIP6 dataset, we assessed drought evolution under SSP1-2.6 and SSP5-8.5 (2015–2100). Combining [...] Read more.

Tropical–subtropical monsoon Asia faces pronounced hydroclimatic change under future warming, yet the regional patterns and emission scenario dependence of drought risk remain unclear. Using a 14-member CMIP6 multi-model ensemble from the NEX-GDDP-CMIP6 dataset, we assessed drought evolution under SSP1-2.6 and SSP5-8.5 (2015–2100). Combining the 3-month Standardized Precipitation Evapotranspiration Index (SPEI-3) with event-based run theory and Mann–Kendall trend analysis, we evaluated four complementary drought dimensions: annual mean SPEI, frequency, intensity, and duration. Regional drought area was used as a spatial diagnostic of extent. A persistent west-to-east moisture gradient characterizes present-day conditions: chronic deficits prevail in southwestern China, southern Myanmar, and Thailand, whereas southeastern China and the equatorial belt maintain relative surpluses. This contrast intensifies through the century, with negative SPEI anomalies deepening by 0.2–0.4 units and chronic drought zones expanding into previously marginal areas. Under SSP1-2.6, no metric shows statistically significant trends. By contrast, SSP5-8.5 produces robust drying, with 8.0% of the area showing significant SPEI declines and up to 30.9% exhibiting significant intensification. Scenario-driven increments affect 89–99.7% of the area across all indicators, confirming that higher emissions systematically elevate drought frequency, persistence, and severity. Scenario uncertainty surpasses model structural uncertainty first for intensity (2067), then area (2078), duration (2079), and frequency (2090), reflecting earlier model convergence on the forced thermodynamic shift than on threshold-dependent frequency counts. Stringent mitigation consistent with the Paris Agreement can largely stabilize regional moisture regimes, whereas continued high emissions will drive pervasive drought intensification across one of the world’s most populous and biodiverse forest regions. Full article

(This article belongs to the Special Issue Drought Risk and Human Vulnerability Under Climate Change: Assessment Frameworks for Water Security and SDGs)

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56 pages, 2301 KB

Open AccessReview

Machine Learning-Driven Multi-Source Remote Sensing for Surface Water Quality Retrieval: Progress and Prospects

by Qiquan He, Dunliang Wang, Fangfang Ji, Lin Zhu, Rui Li, Ting Tian, Qing Zhang, Yueyue Tao and Miao He

Water 2026, 18(14), 1744; https://doi.org/10.3390/w18141744 - 18 Jul 2026

Abstract

Surface water quality is critical to ecosystem health and sustainable development, yet conventional monitoring falls short of spatiotemporally continuous assessment. Remote sensing coupled with machine learning has become a powerful paradigm for large-scale quantitative retrieval of water quality parameters (WQPs). This review examines [...] Read more.

Surface water quality is critical to ecosystem health and sustainable development, yet conventional monitoring falls short of spatiotemporally continuous assessment. Remote sensing coupled with machine learning has become a powerful paradigm for large-scale quantitative retrieval of water quality parameters (WQPs). This review examines the progress and prospects of machine-learning-driven multi-source remote sensing for surface WQP retrieval. A systematic literature review following PRISMA 2020 guidelines, covering 437 Web of Science Core Collection publications (2000–2025), reveals exponential growth, with China and the United States contributing 70.3% of total output. A critical synthesis covers four dimensions: (1) characteristics and fusion strategies of satellite, airborne, and ground-based remote sensing data; (2) modeling features of traditional machine learning (SVR, RF, GBDT), deep learning (CNN, RNN, Transformer), and hybrid approaches; and (3) retrieval advances for optically active versus non-optically active parameters—the former approaches operational readiness while the latter remains constrained by weak indirect spectral correlations; and (4) uncertainty sources and mitigation strategies across the data–model–parameter chain. Five key challenges are identified: limited model generalizability, insufficient physical interpretability, optical heterogeneity and parameter coupling, scarce in situ data, and multi-source fusion bottlenecks. Five future directions are proposed—transfer learning, physically informed explainable machine learning, non-optically active parameter retrieval, benchmark dataset development, and intelligent multi-source fusion—offering a roadmap toward operational surface water quality monitoring. Full article

(This article belongs to the Special Issue AI-Driven Multi-Process Synergy in Watershed Systems: Intelligent Diagnosis for River–Lake Ecology)

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23 pages, 10103 KB

Open AccessArticle

Catchment Controls of the Hydrochemistry of High-Altitude Lakes in the High Tatra Mountains (Slovakia)

by Kristína Hrivnáková, Jiří Kopáček and Juraj Hreško

Water 2026, 18(14), 1743; https://doi.org/10.3390/w18141743 - 18 Jul 2026

Abstract

Catchment characteristics significantly influence water composition in pristine mountain lakes, receiving similar atmospheric deposition. We analysed these relationships for 20 subalpine and alpine catchment–lake systems in the High Tatra Mountains (Slovakia), using a comprehensive new dataset of detailed catchment characteristics and mean water [...] Read more.

Catchment characteristics significantly influence water composition in pristine mountain lakes, receiving similar atmospheric deposition. We analysed these relationships for 20 subalpine and alpine catchment–lake systems in the High Tatra Mountains (Slovakia), using a comprehensive new dataset of detailed catchment characteristics and mean water chemistry from 2021 to 2024. Redundancy analysis indicated that catchment characteristics explained 47% of the spatial variability in lake hydrochemistry. The most influential parameters were land cover (20%), terrain slope (11%), lake-to-catchment area ratio (8%), and bedrock geology (8%). Cation concentrations were dominated by Ca²⁺, while anions were dominated by HCO₃⁻. Concentrations of Na⁺, K⁺, Cl⁻, dissolved organic carbon (DOC), and total organic nitrogen (TON) were higher, while NO₃⁻ was lower, in lakes with greater soil and vegetation cover in catchments. Concentrations of Na⁺, K⁺, Mg²⁺, Ca²⁺, HCO₃⁻, Cl⁻, SO₄²⁻, silicon (Si), and DOC decreased with increasing altitude, whereas Na⁺, K⁺, SO₄²⁻, NO₃⁻, NH₄⁺, and Si increased with catchment slope. Catchment bedrock geology affected K⁺, SO₄²⁻, and Si concentrations in lake water. More than 50% of the observed variability remained unexplained, indicating that additional climatic and hydrological drivers may influence lake hydrochemistry and represent important directions for future research. Full article

(This article belongs to the Section Water Quality and Contamination)

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30 pages, 1088 KB

Open AccessReview

Research Trends in Wastewater Treatment for Sustainable Environmental Management of the Black Sea Basin—A Bibliometric Analysis

by Elena Bisinicu, Elena Ristea and Luminita Lazar

Water 2026, 18(14), 1742; https://doi.org/10.3390/w18141742 - 18 Jul 2026

Abstract

The Black Sea is a semi-enclosed basin that has experienced significant environmental degradation driven by nutrient enrichment and pollution from insufficiently treated wastewater discharges. While previous reviews have focused primarily on ecological impacts and eutrophication dynamics, no bibliometric study has systematically examined the [...] Read more.

The Black Sea is a semi-enclosed basin that has experienced significant environmental degradation driven by nutrient enrichment and pollution from insufficiently treated wastewater discharges. While previous reviews have focused primarily on ecological impacts and eutrophication dynamics, no bibliometric study has systematically examined the representation of wastewater treatment technologies within this literature. This review addresses that gap, providing the first bibliometric synthesis to jointly analyse environmental research trends and wastewater treatment technology development in the Black Sea basin. A total of 1002 peer-reviewed publications indexed in the Web of Science Core Collection between January 2000 and March 2026 were analysed using a Preferred Reporting Items for Systematic Reviews and Meta-Analyses-based framework to examine research trends, thematic clusters, and geographic distribution. A targeted subset of 101 publications directly addressing wastewater treatment technologies was extracted for detailed technological classification. The results reveal a clear increase in research output over the past two decades, with eutrophication, nutrient enrichment, and water-quality degradation as dominant themes. Geographic analysis shows that Türkiye (n = 383), Russia (n = 232), and Romania (n = 129) are the leading contributors, with riparian countries accounting for 83.8% of publications. However, only 101 of the 1002 publications (10.1%) directly address wastewater treatment technologies, with most studies focused on conventional WWTP infrastructure (75.2%) and biological nutrient removal (22.8%). Advanced treatment technologies and nature-based solutions each represent only 3.0% of the wastewater subset. These findings are consistent with a meaningful gap in the regional evidence base for technological approaches to reducing nutrient inputs to the Black Sea, though it should be noted that publication volume alone cannot fully characterise the state of technological development in the region, as it is also shaped by funding structures, disciplinary traditions, and indexing practices. Nevertheless, expanding research on innovative and sustainable wastewater treatment technologies could play an important role in improving wastewater management and supporting long-term ecosystem recovery. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

26 pages, 979 KB

Open AccessArticle

Study on the Release Patterns of Chemical Oxygen Demand from Sediments in Typical Eutrophic Shallow Lakes on Plateaus

by Shiqi Peng, Wen Chen, Junlei Wang, Ao Li, Jingyi Chen, Naiming Zhang and Li Bao

Water 2026, 18(14), 1741; https://doi.org/10.3390/w18141741 - 18 Jul 2026

Abstract

Lake eutrophication and water quality deterioration are increasingly jeopardizing both ecological integrity and human health. As a typical eutrophic shallow lake on plateaus, Yilong Lake currently faces the primary issue of excessive COD_Cr levels. Through systematic sampling and analysis, as well as [...] Read more.

Lake eutrophication and water quality deterioration are increasingly jeopardizing both ecological integrity and human health. As a typical eutrophic shallow lake on plateaus, Yilong Lake currently faces the primary issue of excessive COD_Cr levels. Through systematic sampling and analysis, as well as static release of COD_Cr from sediment experiments, we have categorized the release process of COD_Cr and identified factors that are highly correlated with COD by using RDA and random forest analyses. The aim is to investigate the release patterns of COD_Cr in Yilong Lake, explore the primary factors influencing COD_Cr, and understand the causes of water quality pollution in the lake. The principal findings of this study are as follows: the static release of COD_Cr from sediment experiments was conducted to estimate the COD_Cr release flux from the sediments of Yilong Lake using Fick’s first law, and the release process was divided into three stages: initial release, intermediate adsorption, and late equilibrium. The RDA results indicate that SedpH and SedTP are positively correlated with both COD_Cr and COD_Mn; COD_Mn is statistically most closely related to SedAP; and COD_Cr exhibits the strongest synergy with SedpH. The random forest model output demonstrates that BOD₅ is the factor most highly correlated with COD_Cr, followed by SedAP. The results of the submerged plant humic degradation experiments show that the organic matter released during the humic degradation process of submerged plants has a significant impact on COD_Cr in water bodies, and that algal activity also affects COD_Cr. These findings provide a scientific basis for environmental protection and pollution control in Yilong Lake and similar lakes. Full article

(This article belongs to the Special Issue Advances in Plateau Lake Water Quality and Eutrophication)

24 pages, 9716 KB

Open AccessArticle

The Influence of Water Accumulation in Open Pits on the Stability of Boundary Coal–Rock Pillars

by Junhai He, Cunjin Lu, Yongqiang Zhang, Hui Zhao and Jinpeng Xu

Water 2026, 18(14), 1740; https://doi.org/10.3390/w18141740 - 18 Jul 2026

Abstract

To reveal the influence of water accumulation in open pits on the stability of boundary coal–rock pillars, this study investigates a boundary coal–rock pillar between an underground coal mine and an adjacent open pit in western China. Coal–rock physical property tests, hydrochemical analysis, [...] Read more.

To reveal the influence of water accumulation in open pits on the stability of boundary coal–rock pillars, this study investigates a boundary coal–rock pillar between an underground coal mine and an adjacent open pit in western China. Coal–rock physical property tests, hydrochemical analysis, permeability tests, and theoretical calculations of water-resisting coal–rock pillars were conducted to examine seepage channel formation, physical property changes, and stability evolution under long-term water accumulation. The results show that the mechanical strength of coal and rock specimens decreases under the saturated state. The uniaxial compressive strength of rock specimens decreases by 8.75–50.64%, while that of No.2⁻² and No.3⁻¹ coal specimens decreases by 17.72% and 25.01%, respectively. The tensile strength decreases by 24.59–59.11%, and the shear strength decreases by 4.36–45.96%. The hydraulic conductivity of intact specimens is mostly 10⁻⁴~10⁻³ m/d, whereas that of fractured specimens increases to 10⁻³~10⁻² m/d. The calculated width of water-resisting coal pillars increases by 19.7~21.9% under long-term water accumulation. Long-term water accumulation in the open pit changes the external hydraulic boundary of the boundary coal–rock pillar, allowing water to migrate inward along bedding planes, joints, primary fractures, mining-induced fractures, and coal seam pores. This process promotes the connection of pre-existing pore–fracture structures and seepage channel formation, weakens particle cementation and structural-plane shear resistance, and reduces the structural integrity, bearing capacity, and water-resisting capacity of the coal–rock pillar. Therefore, the stability deterioration of boundary coal–rock pillars is a continuous process involving channel formation, sustained seepage, strength degradation, enhanced pore–fracture connectivity, permeability enhancement, and further stability reduction. Full article

(This article belongs to the Section Hydrogeology)

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26 pages, 8415 KB

Open AccessArticle

CNN-LSTM for Roof-Water-Inrush Risk Zoning with Edge Deployment

by Tao Yang, Quanxin Wang, Jie Zhang, Dong Liu, Haifei Lin, Yiming Zhang, Longqian Zhang and Shuqi Zhang

Water 2026, 18(14), 1739; https://doi.org/10.3390/w18141739 - 17 Jul 2026

Abstract

Reliable roof-water-inrush risk zoning in coal mines remains difficult under small-sample conditions because geological, hydrogeological, and mining-induced factors interact nonlinearly, and field labels are often derived from engineering evidence rather than complete accident records. This study aims to develop and preliminarily validate a [...] Read more.

Reliable roof-water-inrush risk zoning in coal mines remains difficult under small-sample conditions because geological, hydrogeological, and mining-induced factors interact nonlinearly, and field labels are often derived from engineering evidence rather than complete accident records. This study aims to develop and preliminarily validate a deployment-oriented workflow for case-specific roof-water-inrush risk-zone classification in the No. 4⁻³ coal seam of Shiyangou Coal Mine, Shaanxi Province, China. A total of 100 spatial evaluation samples were compiled using eight indicators grouped into water-resisting capacity, water-supply intensity, water-conducting pathways, mining-induced disturbance, and rock-mass integrity. The Safe-Zone and Risk-Zone labels were generated from mine-water-prevention documents, borehole and hydrogeological evidence, abnormal goaf-water information, and expert engineering judgment. A lightweight CNN-LSTM model was trained with leakage-controlled data splitting, early stopping, L2 regularization, gradient clipping, and model-capacity control. Because the inputs are static or quasi-static spatial indicators, LSTM was used only as a gated feature-dependency module for CNN-derived feature sequences, and its necessity was examined using ablation and feature-order perturbation tests. In repeated stratified five-fold cross-validation, the model achieved mean accuracy, F1-score, and AUC values of 0.792 ± 0.108, 0.633 ± 0.111, and 0.829 ± 0.097, respectively. On an independent prediction dataset, the accuracy and AUC were 0.750 and 0.743, respectively. After ONNX export, STM32CubeMX evaluation indicated 68,962 B Flash and 3252 B RAM consumption. These results indicate the preliminary feasibility of embedded roof-water-inrush risk-zone classification for this specific mine case. However, the findings do not demonstrate cross-mine transferability; further validation using external datasets, independent labels, and field deployment records is required. Full article

(This article belongs to the Special Issue Advances in Machine Learning for Flood Prediction and Water Risk Management)

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23 pages, 21383 KB

Open AccessArticle

Failure Mechanism and Key Support Techniques for Large-Span Junctions Influenced by Water Seepage in Interbedded Strata: A Case Study

by Zhili Su, Xun Liu and Genshui Wu

Water 2026, 18(14), 1738; https://doi.org/10.3390/w18141738 - 17 Jul 2026

Abstract

With intensifying mineral resource extraction, groundwater ingress in large cross-sectional intersection roadways near aquifers is becoming increasingly common. Disturbances from roadway excavation and mining may induce fractures connecting to aquifers and a series of related adverse hydrogeological effects, posing severe challenges to surrounding [...] Read more.

With intensifying mineral resource extraction, groundwater ingress in large cross-sectional intersection roadways near aquifers is becoming increasingly common. Disturbances from roadway excavation and mining may induce fractures connecting to aquifers and a series of related adverse hydrogeological effects, posing severe challenges to surrounding rock stability control of such excavations. Large-span roadway intersections in water-bearing sandstone–mudstone interbedded weak strata are frequently subjected to severe instability, bringing great challenges to the design of roadway supports. A typical large-section intersection roadway from a mine in Xinjiang is taken as the research object. Systematic research is carried out via field investigation, numerical modeling and field testing. Results show that the original aquiclude structure of sandstone–mudstone interbeds is destroyed by excavation disturbance. Mudstone strength degradation induced by sandstone pore water migration is confirmed as the core cause of surrounding rock instability. Surrounding rock deformation increases rapidly with the rise in mudstone moisture content, and obvious sudden change characteristics are presented when the water content approaches saturation. A collaborative support strategy with waterproofing as the core is proposed. Targeted drainage, high-reliability zoned support and anti-corrosion measures for support components are set as supporting measures. The proposed strategy is verified to perform well in field industrial tests. Waterproof measures, waterproof anchoring agents, anchor cable grouting and high-performance anchor-mesh-cable shotcreting support are integrated in the strategy. Surrounding rock deformation can be effectively controlled and a good application effect is achieved. The proposed support system is also applicable to roadway projects in metal and non-metal mines with similar geological conditions. Full article

(This article belongs to the Topic Control Mechanisms and Technological Applications for Surrounding Rock in Deep Mine Roadways)

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33 pages, 9767 KB

Open AccessArticle

Climate Change and Climatic Water Balance in Brandenburg (Germany): Seasonal Drying and Hydro-Climatic Stress Under Multi-Model Climate Projections to 2100

by Mohamed Ali Mohamed, Rainer Hentschel and Winfried Riek

Water 2026, 18(14), 1737; https://doi.org/10.3390/w18141737 - 17 Jul 2026

Abstract

Climate change is expected to alter hydro-climatic conditions and water availability across Central Europe, with important implications for vegetation and land-use systems. This study assesses projected changes in climatic water balance (CWB), hydro-climatic stress indicators, and their relationship with root-zone soil moisture in [...] Read more.

Climate change is expected to alter hydro-climatic conditions and water availability across Central Europe, with important implications for vegetation and land-use systems. This study assesses projected changes in climatic water balance (CWB), hydro-climatic stress indicators, and their relationship with root-zone soil moisture in Brandenburg, Germany. Four regional climate model realizations under RCP4.5 and RCP8.5 were analyzed for 2006–2100. Air temperature (tas), precipitation (pr), reference evapotranspiration (ET₀), and CWB were evaluated together with indicators describing drought frequency, water-deficit magnitude, aridity, and standardized CWB anomalies. All model realizations project substantial warming, exceeding +2 °C under RCP8.5 by the late century. While annual precipitation remains relatively stable, vegetation-period precipitation decreases and evaporative demand increases, resulting in increasingly negative growing-season CWB. Projected vegetation-period CWB changes range from −22 to −139 mm between near-future and far-future periods. Hydro-climatic stress indicators consistently show increasing seasonal water limitation. Comparisons between CWB and root-zone soil moisture reveal significant positive relationships (p < 0.001), although explanatory power remains low (R² < 0.14). Despite differences in the magnitude of projected changes, all model realizations agree on the direction of change, indicating a robust signal of increasing growing-season drying. These findings highlight the importance of seasonal hydro-climatic indicators for assessing future drought risk and ecosystem water availability. Full article

(This article belongs to the Special Issue Water-Soil-Vegetation Interactions in Changing Climate)

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21 pages, 8298 KB

Open AccessArticle

Dynamic Numerical Assessments of Risk Control Strategies: Case Study in a Pb-Zn Tailing-Pond-Impacted Aquifer

by Xueyong Wu, Lizhi Tong, Shuting Wang, Xuekui Niu, Longzhen Ding, Luwen Zhuang and Weihua Zhang

Water 2026, 18(14), 1736; https://doi.org/10.3390/w18141736 - 17 Jul 2026

Abstract

The long-term release of heavy metals from inactive tailing ponds poses a persistent threat to groundwater quality, yet the effectiveness of commonly employed risk control measures—such as anti-seepage liners and chemical stabilization—remains insufficiently evaluated under realistic field conditions. This study aims to assess [...] Read more.

The long-term release of heavy metals from inactive tailing ponds poses a persistent threat to groundwater quality, yet the effectiveness of commonly employed risk control measures—such as anti-seepage liners and chemical stabilization—remains insufficiently evaluated under realistic field conditions. This study aims to assess the effectiveness of risk control strategies at a Pb Zn mine tailing pond in Yunnan Province, China. A dynamic 2D numerical pollutant transport model was developed, calibrated, and validated against observed hydraulic heads and metal concentrations from monitoring wells within the study aquifer. The calibrated model showed good agreement with field measurements. Simulation results indicate that anti-seepage liners alone are insufficient to ensure compliance with the Class III standards of the Chinese Groundwater Quality Standards, even under ideal conditions where all leaching from the tailing pond is prevented. In contrast, a combined strategy—chemical stabilization reducing Pb leaching from historically contaminated soils (initial Pb: 183 µg L⁻¹) by at least 70%, together with anti-seepage systems reducing infiltration flux by over 94.4%—would be sufficient to restore groundwater quality to within regulatory limits. Full article

(This article belongs to the Topic Environmental Pollutant Management and Control)

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36 pages, 2370 KB

Open AccessReview

Climate Change and Water Resources: A Comprehensive Review of Impacts, Adaptation Strategies, and Resilience Frameworks

by Lucian Dordai, Marius Roman, Cecilia Roman and Anca Becze

Water 2026, 18(14), 1735; https://doi.org/10.3390/w18141735 - 17 Jul 2026

Abstract

Freshwater resources constitute a fundamental component of coupled natural–human systems, underpinning ecosystem functioning, biogeochemical cycling, and socio-economic development. Anthropogenic climate change (i.e., climate change attributable to human activity, as distinct from natural climatic variability), driven primarily by greenhouse gas emissions and land-use change, [...] Read more.

Freshwater resources constitute a fundamental component of coupled natural–human systems, underpinning ecosystem functioning, biogeochemical cycling, and socio-economic development. Anthropogenic climate change (i.e., climate change attributable to human activity, as distinct from natural climatic variability), driven primarily by greenhouse gas emissions and land-use change, is exerting significant pressure on the global hydrological cycle, resulting in increased hydroclimatic variability, intensification of extreme hydrometeorological events, and progressive degradation of freshwater quality and availability. This review synthesizes recent scientific evidence on climate-induced impacts on water systems together with emerging adaptation and resilience strategies. The analysis is based on a systematic assessment of 100 peer-reviewed studies indexed in the Web of Science Core Collection (2010–2025) and synthesized following a PRISMA-informed (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) narrative review protocol. Beyond confirming well-established trends in precipitation regimes, cryospheric decline, increasing evapotranspiration, and the growing frequency of droughts and floods, this review quantifies the magnitude of these changes across the reviewed literature, including an approximately 134% increase in flood-related disasters since 1980 and a 29% increase in drought duration since 2000. More importantly, it provides an integrated synthesis that links physical climate impacts with adaptation strategies and socio-ecological resilience frameworks within a unified analytical perspective, thereby complementing previous domain-specific reviews that have generally examined these dimensions separately. Prominent adaptation pathways identified across the reviewed literature include nature-based solutions, integrated water resources management frameworks, and the deployment of digital water technologies. In parallel, resilience is increasingly conceptualized as the adaptive capacity of socio-hydrological systems to absorb disturbances, reorganize, and transform under changing climatic conditions. The findings highlight the need to strengthen integrated and cross-sectoral water governance, enhance climate-informed decision-making, and expand monitoring and data infrastructures to improve long-term water security and socio-ecological resilience under accelerating climate change. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Water Resources: Assessment and Modeling, 3rd Edition)

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16 pages, 19862 KB

Open AccessArticle

Ice Cover and Phytoplankton Dynamics Are Linked to Carbon and Nitrogen Cycling and Burial at an Anoxic Lake Huron Sinkhole

by Cecilia M. Howard, Diana Velazquez, Kathryn I. Rico and Nathan D. Sheldon

Water 2026, 18(14), 1734; https://doi.org/10.3390/w18141734 - 17 Jul 2026

Abstract

Records of recent past climate provide an essential window into understanding how changing climate influences environments and ecosystems such as lakes, which provide essential resources and services. Sediment carbon and nitrogen chemistry can offer insight into productivity and biochemistry, and anoxic sediments in [...] Read more.

Records of recent past climate provide an essential window into understanding how changing climate influences environments and ecosystems such as lakes, which provide essential resources and services. Sediment carbon and nitrogen chemistry can offer insight into productivity and biochemistry, and anoxic sediments in particular can often preserve short-term changes in these signals. We used a decade-long compilation of sediment and environmental data from Middle Island Sinkhole, an anoxic sinkhole in Lake Huron, to investigate their interannual variability. We found that seasonal and annual changes in local ice season, chlorophyll, and precipitation influenced the amount and isotopic composition of carbon reaching and being recycled within the sediments. Carbon and nitrogen signals reflected the year or season of sample collection in sediments as deep as 12 cm, while the shallowest sediments were dominated by the influence of microbial mats. Our findings demonstrate that seasonal dynamics in surface water in this part of the Great Lakes are leading to increased export of organic carbon and nitrogen into sediments, but that in situ sediment processes may make teasing out short-term changes from sediment cores difficult even in an anoxic setting. These results emphasize the importance of winter conditions as a driver of short-term lacustrine carbon and nitrogen cycling in sediments and the water column. Full article

(This article belongs to the Special Issue Carbon Storage in Lake Sediments Under Climate Change)

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23 pages, 972 KB

Open AccessArticle

Water Quality Assessment of the Uvac River (Serbia) Using the Water Pollution Index (WPI): Relevance for Protected Area Sustainability and Tourism

by Dragana Milijašević Joksimović, Dejana Jakovljević, Tamara Jojić Glavonjić, Jovana Brankov and Ana Milanović Pešić

Water 2026, 18(14), 1733; https://doi.org/10.3390/w18141733 - 17 Jul 2026

Abstract

Although water resources are very significant natural assets of protected areas, the increasingly intensive tourism development in national parks and nature reserves brings them under constant anthropogenic pressure. Therefore, the analysis of water quality and pollution in them is of great importance. This [...] Read more.

Although water resources are very significant natural assets of protected areas, the increasingly intensive tourism development in national parks and nature reserves brings them under constant anthropogenic pressure. Therefore, the analysis of water quality and pollution in them is of great importance. This study evaluates the water quality of the Uvac River (Serbia) at the Priboj hydrological station using the Water Pollution Index (WPI), based on physicochemical data for the period 2021–2023. As part of the WPI methodology, C_i/S_i ratios between mean annual parameter concentrations and reference values for Class I (excellent water quality status) were analyzed. For seasonal analysis, C_i/S_i between seasonal parameter concentrations and reference values for Class I were calculated. Relationships between WPI and selected water-quality parameters were also analyzed. Annual WPI values ranged from 0.89 to 0.99, indicating stable Class II water quality throughout the study period. Seasonal analysis showed occasional shifts to Class III during autumn and winter, associated with increased organic matter and nutrient inputs. Correlation analysis revealed strong relationships between WPI and TOC, BOD₅, and COD_Mn, while moderate correlations with ammonium, suspended solids, and phosphorus compounds suggest the influence of nutrient inputs and hydrological conditions. Full article

(This article belongs to the Special Issue Environmental and Anthropogenic Influences on Freshwater Biodiversity and Ecosystem Health)

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20 pages, 33075 KB

Open AccessArticle

Regional Reservoir Assessment Using Sr and δ²H-δ¹⁸O Isotopes in Jinlun, Taiwan

by Yi-Chi Chen, Po-Kuei Chen, Pei-Jyuan Gao, Wen-Dar Tai, Kai-Chun Fan, Yen-Che Liao and Yin-Lung Han

Water 2026, 18(14), 1732; https://doi.org/10.3390/w18141732 - 17 Jul 2026

Abstract

Geothermal energy is a low-carbon baseload renewable energy that plays a key role in global energy transition. Jinlun of Taitung is a region with high potential for geothermal energy. However, sustainable resource utilization requires a comprehensive understanding of fluid sources, recharge mechanisms, and [...] Read more.

Geothermal energy is a low-carbon baseload renewable energy that plays a key role in global energy transition. Jinlun of Taitung is a region with high potential for geothermal energy. However, sustainable resource utilization requires a comprehensive understanding of fluid sources, recharge mechanisms, and circulation systems. This study integrated δ¹⁸O, δD, ⁸⁷Sr/⁸⁶Sr and elemental geochemistry to clarify the underlying hydrogeochemical mechanism and develop an underground fluid circulation model for Jinlun. The water compositions indicate that water–rock interactions are the dominant control on fluid chemistry. Hydrogen and oxygen isotope analysis revealed a geothermal water recharge elevation of 1321–1478 m, slightly higher than that of hot spring water (951–1459 m). The natural recharge amount of a corresponding area was approximately 13.57 × 10⁶ t/yr. A strontium isotope mixing model indicated that the fluids were affected by three end members of deep geothermal water, shallow groundwater, and seawater. Shallow groundwater had a contribution rate of 92–98% to noncoastal hot spring water and up to 81% to geothermal water. The coastal hot spring was most affected by seawater at 48%. Rainwater infiltrated into E2 to form shallow groundwater. Some of the infiltrated water reached a deep circulation into the M3 layer and formed deep-source thermal water. Overall, this study establishes a hydrogeochemical model for Jinlun and provides scientific foundation for geothermal well design and sustainable resource management. Full article

(This article belongs to the Special Issue Advances in Hydrology and Water Resources Management for Sustainable Futures)

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21 pages, 3009 KB

Open AccessArticle

Climate Effects on Water Chemistry in Acid-Sensitive Catchments

by Rolf D. Vogt, Marianne Stave Sekkenes, Magnus D. Norling, Kari Austnes, Heleen A. de Wit and Øyvind Kaste

Water 2026, 18(14), 1731; https://doi.org/10.3390/w18141731 - 17 Jul 2026

Abstract

Substantial declines in acidifying emissions across Europe have led to pronounced chemical recovery of Norwegian surface waters. In recent decades, however, changes in water chemistry have increasingly coincided with climate change, complicating the attribution of observed trends to individual drivers. This study assesses [...] Read more.

Substantial declines in acidifying emissions across Europe have led to pronounced chemical recovery of Norwegian surface waters. In recent decades, however, changes in water chemistry have increasingly coincided with climate change, complicating the attribution of observed trends to individual drivers. This study assesses whether ongoing climate change has produced detectable effects on freshwater chemistry in Norway and how these effects vary among catchments with differing sensitivities to acidification. In this study, the Model of Acidification of Groundwater In Catchments (MAGIC), which is based on current understanding of the processes governing acid–base chemistry in soils and waters, was used to simulate the effects of declining acid deposition. Deviations between observed and modelled water chemistry were provisionally interpreted as climate-related effects. However, these residuals may also reflect model or parameter uncertainty and other unaccounted-for processes. The analysis draws on long-term monitoring data (1986–2022) from 59 acid-sensitive Trend Lakes distributed across Norway, together with four Field Research Stations (1986–2020) representing contrasting hydroclimatic and biogeochemical conditions. Temporal trends were evaluated using the Mann–Kendall test and Sen’s slope estimator, while relationships between inferred climate effects and climatic variables were examined using Pearson’s correlation analysis. Across the Trend Lakes, inferred climate effects were predominantly positive for acid-neutralising capacity (ANC) and weathering-derived cations, suggesting that climate change may contribute to accelerated chemical recovery, particularly in catchments less sensitive to acidification. The inferred climate effects varied substantially among the Field Research Stations. Higher temperatures were generally associated with enhanced recovery, possibly through intensified silicate weathering, whereas increased precipitation and runoff appeared to dampen recovery. Overall, the results suggest that climate change exerts a measurable influence on freshwater chemistry in Norway, although the magnitude and direction of the response are strongly modulated by catchment-specific characteristics. While previous studies have identified climate-related influences on individual chemical variables, quantitative attempts to separate climate- and acid-deposition-related effects across a large number of acid-sensitive catchments remain rare. Here, we use deviations between observed water chemistry and MAGIC simulations of acid deposition recovery as a screening approach to investigate whether climate-related signals can be detected at the national scale and whether these signals vary among catchments with differing sensitivities to acidification. Full article

(This article belongs to the Special Issue Climate, Water, and Soil, 2nd Edition)

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24 pages, 1808 KB

Open AccessArticle

The Impact of Marine Economic Innovation and Development Policy on Marine Economic Resilience

by Ning Han, Feiyang Sun, Zhenshun Tu and Yao Xu

Water 2026, 18(14), 1730; https://doi.org/10.3390/w18141730 - 17 Jul 2026

Abstract

Amid rising global economic uncertainty and frequent external shocks, strengthening marine economic resilience has become a core priority for coastal nations to stabilize industrial supply chains and achieve sustainable marine development. China’s traditional resource-driven marine economy faces persistent structural bottlenecks, including homogeneous industrial [...] Read more.

Amid rising global economic uncertainty and frequent external shocks, strengthening marine economic resilience has become a core priority for coastal nations to stabilize industrial supply chains and achieve sustainable marine development. China’s traditional resource-driven marine economy faces persistent structural bottlenecks, including homogeneous industrial structure, low value addition and weak risk resistance. As a landmark national policy for sustainable marine economic growth, the Marine Economic Innovation and Development Policy (MEIDP) has been piloted in 15 coastal cities across two batches, yet its causal impact on marine economic resilience remains under systematic evaluation. Using panel data of 51 Chinese coastal cities from 2008 to 2023, this study employs a multi-period difference-in-differences approach with supporting analyses to systematically evaluate the MEIDP’s impact on marine economic resilience, as well as its moderating mechanisms and heterogeneous patterns. The key findings are threefold. First, the MEIDP significantly improves coastal cities’ marine economic resilience, and this positive effect remains stable after multiple robustness tests. Second, public health emergencies exert a significant positive moderating effect, where the industrial support capacity and risk-resilience foundations established through policy implementation function more effectively under shock conditions, thereby amplifying the enhancement of resilience. Third, the policy effect shows prominent heterogeneity, being more pronounced in high-tourism cities and the Northern Marine Economic Circle, while statistically insignificant in low-tourism cities and the Southern Marine Economic Circle. This study enriches the theoretical framework of marine economic policy evaluation and provides empirical evidence from a major developing country for global marine governance, confirming that marine policies that promote innovation are an effective path to strengthen economic risk resistance. In light of these findings, we propose targeted policy recommendations to steadily enhance overall marine economic resilience. Coastal regions should deepen marine policies that promote innovation to bolster industrial upgrading and technological empowerment, adopt differentiated schemes aligned with local industrial foundations and resource endowments, promote marine industrial diversification and chain extension to reduce structural vulnerability, and improve public risk response mechanisms to strengthen the counter-cyclical buffering capacity of the marine economy. Full article

(This article belongs to the Special Issue Governance of the Marine Ecological Environment and High-Quality Blue Development)

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