Water

16 pages, 3128 KB

Open AccessArticle

Dynamic Water-Energy-Carbon Trade-Off Optimization for Heavy Industry Decarbonization via Deep Reinforcement Learning: A UK Case Study

by M. Hassan, M. B. Rasheed, Inam Ullah Khan and K. A. A. Gamage

Water 2026, 18(9), 1112; https://doi.org/10.3390/w18091112 - 6 May 2026

Viewed by 13166

Abstract

In recent years, the industrial decarbonization in the cement sector has introduced secondary environmental impact due to an increase in power and water demand. Deploying carbon capture, utilization, and distributed storage requires an uninterrupted supply of power and water to achieve net-zero targets. [...] Read more.

In recent years, the industrial decarbonization in the cement sector has introduced secondary environmental impact due to an increase in power and water demand. Deploying carbon capture, utilization, and distributed storage requires an uninterrupted supply of power and water to achieve net-zero targets. However, the traditional static optimization algorithms seem insufficient in addressing the high-frequency and dynamic renewable networks. To overcome these issues, this work develops a dynamic water-energy-carbon trade-off optimization model for industrial decarbonization, with the deployment of Carbon Capture, Utilization, and Storage system in the cement sector within a United Kingdom industrial cluster. The key objective is to quantify and control the secondary burden that low-carbon interventions can impose on electricity systems and local water resources. Firstly, the Water-Energy-Carbon problem is treated as a tri-lemma, which is formulated as a continuous Markov Decision Process. Then the optimization problem is solved via a Soft Actor-Critic Deep Reinforcement Learning algorithm under coupled and resource-constrained abstraction inputs. This work further introduces the Water-Carbon Mitigation Penalty Index as a diagnostic metric for measuring the marginal increase in water burden associated with carbon mitigation. The results show that unmanaged distributed carbon-mitigation pathways increase local hydrological stress by 2.15–5.17% relative to baseline operating conditions. Although the proposed algorithm successfully reduces the nexus cost by up to 70.5% and achieves 13.83% carbon reduction by shifting from freshwater abstraction to reclaimed municipal wastewater and by coordinating operation with low-carbon hydropower availability. These results show that dynamic AI-based scheduling can support net-zero transitions while reducing pressure on regional hydro-ecological systems. Full article

(This article belongs to the Section Water-Energy Nexus)

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15 pages, 5244 KB

Open AccessArticle

Occurrence and Seasonal Variability of Cyanotoxins in Mesotrophic and Eutrophic Water Bodies of Central Chile

by Johanna Beltrán, Pablo Pedreros, Guido Carrasco, Silvia Basualto, Oscar Parra and Roberto Urrutia

Water 2026, 18(9), 1111; https://doi.org/10.3390/w18091111 - 6 May 2026

Viewed by 656

Abstract

Cyanotoxins were evaluated in seven water bodies in central Chile (Avendaño, Lo Galindo, Grande de San Pedro, Lanalhue, Vichuquén, Torca, and Llico) from October 2022 to May 2023. Microcystins (MC-RR, MC-YR, MC-LR, MC-LA) and nodularin were quantified by HPLC-DAD, and their relationships with [...] Read more.

Cyanotoxins were evaluated in seven water bodies in central Chile (Avendaño, Lo Galindo, Grande de San Pedro, Lanalhue, Vichuquén, Torca, and Llico) from October 2022 to May 2023. Microcystins (MC-RR, MC-YR, MC-LR, MC-LA) and nodularin were quantified by HPLC-DAD, and their relationships with environmental variables and cyanobacterial abundance were assessed using Spearman correlation and principal component analysis (PCA). Cyanotoxins were detected in six systems, with MC-LR as the dominant congener. The highest concentration (407.5 µg/L) occurred in the mesotrophic Laguna Grande de San Pedro. Correlation analysis showed nodularin positively associated with conductivity (ρ = 0.40, p < 0.05), while microcystins were negatively correlated with temperature (ρ to −0.60, p < 0.05). PCA explained 57.7% of variance, distinguishing toxin patterns along gradients of temperature, pH, conductivity, and N:P ratio. Cyanotoxin occurrence was weakly related to cyanobacterial abundance but consistently associated with low N:P ratios. These findings confirm the presence of cyanotoxin-producing strains in the studied water bodies and highlight the need to integrate nutrient dynamics, cyanobacterial community structure, and multi-congener toxin analysis into monitoring programs. Furthermore, the results demonstrate that mesotrophic systems could represent emerging sources of cyanotoxin production, underscoring the need to improve risk assessment and management strategies. Full article

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

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21 pages, 2693 KB

Open AccessArticle

Enhanced Mass Transfer via Brush Electrode for Significantly Promoted Electrochemical Oxidation of Organic Pollutants

by Kai Wang, Guangsen Xia, Yonggang Jia, Yibao Wang, Lili Zhang, Shaoyan Wang, Xu Chai, Yang Zhou, Lin Cao, Zhibo Cheng, Haiyuan Liu, Maoqiu Ran, Haibo Xu, Yonghong Lu and Zhigang Gai

Water 2026, 18(9), 1110; https://doi.org/10.3390/w18091110 - 6 May 2026

Viewed by 603

Abstract

Electrochemical oxidation (EO) possesses numerous advantages and great potential for organic pollutant degradation. However, traditional plate anodes for EO are limited by pollutant mass transfer, leading to low oxidation efficiency and high energy consumption. Herein, a three-dimensional (3D) polyacrylonitrile-based carbon fiber brush (PAN-CFB) [...] Read more.

Electrochemical oxidation (EO) possesses numerous advantages and great potential for organic pollutant degradation. However, traditional plate anodes for EO are limited by pollutant mass transfer, leading to low oxidation efficiency and high energy consumption. Herein, a three-dimensional (3D) polyacrylonitrile-based carbon fiber brush (PAN-CFB) anode was employed to enhance mass transfer and improve oxidation efficiency. The oxidation capacity of the PAN-CFB anode was compared with those of boron-doped diamond (BDD) and Ti/IrO₂-Ta₂O₅ plate anodes using oxalic acid (OA), phenol, and perfluorooctanoic acid (PFOA) as target pollutants, respectively. Experimental results demonstrated that the 3D PAN-CFB anode exhibits superior direct oxidation capacity compared to BDD and the Ti/IrO₂-Ta₂O₅ plate anode in degrading OA, which is attributed to the significantly enhanced mass transfer of OA toward the brush anode surface. Under a constant current of 400 mA for 240 min, the total organic carbon (TOC) removal from 50 mmol/L OA reached 90.5%, 57.5% and 6.6% for PAN-CFB, BDD and the Ti/IrO₂-Ta₂O₅ anode, respectively, and the energy consumption followed the order of PAN-CFB (5.5~8.9 kWh/kg_TOC) < BDD (11.2~19.3 kWh/kg_TOC) < Ti/IrO₂-Ta₂O₅ (76.1~120.7 kWh/kg_TOC). However, the 3D PAN-CFB anode exhibited poor stability at high potential and failed to promote phenol and PFOA degradation due to the weak direct oxidation capacity toward the two pollutants and the poor generation capacity of reactive oxygen species, associated with its low oxygen evolution potential. Therefore, future efforts should focus on developing stable 3D brush electrodes with a higher oxygen evolution potential to enable non-selective oxidation of a broader range of pollutants. Full article

(This article belongs to the Special Issue Advanced Oxidation Technologies for Water and Wastewater Treatment)

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25 pages, 2189 KB

Open AccessArticle

Regulatory-Aligned Energy Assessment for Wastewater Collection Networks Under the Scope of the UWWTD 2024/3019

by Catarina Jorge, Rita Salgado Brito and Maria do Céu Almeida

Water 2026, 18(9), 1109; https://doi.org/10.3390/w18091109 - 5 May 2026

Viewed by 586

Abstract

The revised EU Urban Wastewater Treatment Directive (UWWTD, EU 2024/3019) expands the scope of the previous directive (Council Directive 91/271/EEC, 1991) by explicitly including combined sewer systems, stormwater discharges, and overflow events while promoting energy neutrality and reducing greenhouse gas (GHG) emissions across [...] Read more.

The revised EU Urban Wastewater Treatment Directive (UWWTD, EU 2024/3019) expands the scope of the previous directive (Council Directive 91/271/EEC, 1991) by explicitly including combined sewer systems, stormwater discharges, and overflow events while promoting energy neutrality and reducing greenhouse gas (GHG) emissions across urban wastewater systems. Although the Directive establishes energy accountability at the system level, it does not define how energy performance in wastewater collection networks should be structured, assessed, or benchmarked, resulting in a significant implementation gap. This paper presents a novel, regulatory-aligned, data-driven framework to organise, analyse, and interpret energy-relevant information in support of UWWTD requirements, with specific focus on wastewater collection networks. Using Portuguese regulator datasets, supplemented with published sources, existing metrics are reorganised into energy-significant dimensions that differentiate structural, excess-driven, operational, and renewable-related components of energy use. The preliminary findings show that available datasets already support a screening-level diagnosis of specific energy intensity, pumping-related energy shares, inflow-driven excess volumes, and associated GHG emissions. However, important gaps remain regarding subsystem disaggregation, hydraulic normalisation, and measurement granularity. The study restructures existing information into a novel audit-compatible framework, proposes additional metrics and measurement requirements, and identifies measures to facilitate UWWTD implementation. Although developed for the Portuguese context, the framework offers a scalable pathway for integrating wastewater collection networks into energy neutrality governance across European Member States. Full article

(This article belongs to the Special Issue Energy Use Assessment and Management in Wastewater Systems)

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22 pages, 3735 KB

Open AccessArticle

Response of Coastal Vegetation to Extreme Precipitation Modulated by Groundwater: A Case Study of Two Extreme Years in the Contemporary Yellow River Delta

by Xiaolan Ji, De Wang, Xinpeng Tian, Xiaoli Bi and Xiaoli Wang

Water 2026, 18(9), 1108; https://doi.org/10.3390/w18091108 - 5 May 2026

Viewed by 748

Abstract

Driven by global warming, increasing extreme precipitation events (EPEs) threaten low-lying coastal ecosystems. This study focused on the contemporary Yellow River Delta and established a continuous framework linking extreme precipitation, groundwater, and vegetation, based on long-term extreme precipitation changes during 1960–2022 and vegetation [...] Read more.

Driven by global warming, increasing extreme precipitation events (EPEs) threaten low-lying coastal ecosystems. This study focused on the contemporary Yellow River Delta and established a continuous framework linking extreme precipitation, groundwater, and vegetation, based on long-term extreme precipitation changes during 1960–2022 and vegetation dynamics during 2001–2022. Using regional precipitation records, groundwater observations from 16 monitoring wells, and five-day kernel normalized difference vegetation index (kNDVI) data, we compared two EPEs that exceeded the 99th-percentile wet-day precipitation threshold and had complete precipitation–groundwater–vegetation observations. Our findings reveal that: (1) extreme precipitation was intensified in the study area, with an R99p trend of 19.1 mm/10 a; (2) vegetation disturbance was stronger and more persistent after the 2019 Lekima event, with a mean post-event kNDVI anomaly of −12.8%, whereas the 2022 Chaba event produced a weaker, later, and more spatially limited negative response; (3) groundwater response was also stronger in 2019, as the proportion of wells with above-surface water levels reached 43.8%, compared with 12.5% in 2022, indicating more extensive and longer-lasting inundation; (4) the shallowest post-event groundwater depth was significantly negatively correlated with kNDVI anomalies (r = 0.579, p < 0.001), and during the 2019 event, the kNDVI fell below about −17% when surface inundation lasted for 6 days. These results indicate that groundwater is a key hydrological link connecting extreme precipitation and vegetation response. This study provides new evidence for the identification and adaptive management of ecological risks in low-lying coastal deltas. Full article

(This article belongs to the Section Oceans and Coastal Zones)

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26 pages, 9037 KB

Open AccessArticle

Measurement-Based Framework for Real-Time Flood Prediction in Small Streams Using Rainfall–Discharge Nomographs and Depth–Discharge Rating Curves

by Tae-Sung Cheong, Seojun Kim and Kang-Min Koo

Water 2026, 18(9), 1107; https://doi.org/10.3390/w18091107 - 5 May 2026

Viewed by 838

Abstract

Small streams exhibit rapid and nonlinear flood responses due to steep slopes, short flow paths, and limited storage capacity, making real-time flood prediction difficult under both computational and data constraints. This study presents a measurement-based flood prediction framework for real-time estimation of flood [...] Read more.

Small streams exhibit rapid and nonlinear flood responses due to steep slopes, short flow paths, and limited storage capacity, making real-time flood prediction difficult under both computational and data constraints. This study presents a measurement-based flood prediction framework for real-time estimation of flood discharge and depth in small-stream basins. Conventional approaches, such as physically based hydrodynamic models, require detailed boundary conditions and high computational cost, while data-driven models often lack physical interpretability. The proposed framework integrates high-frequency monitoring data from the Small-Stream Smart Monitoring System, short-term rainfall nowcasting from the MAPLE system, and nonlinear regression-based hydraulic relationships within a unified operational structure. Rainfall–discharge nomographs and depth–discharge rating curves were developed using a four-parameter logistic regression model based on long-term observations from 12 small streams in Korea. Additional comparisons with alternative regression forms confirmed the suitability of the 4PL model for representing nonlinear hydrological responses. Forecast rainfall was used to estimate discharge, which was subsequently converted to flood depth through calibrated rating curves. For ungauged reaches, depth–discharge relationships were derived using HEC–RAS-based scenario simulations and the Manning equation to enable spatially continuous prediction along stream networks. Model performance was evaluated using independent validation events, showing mean prediction accuracies of approximately 89% for discharge and 90% for flood depth. The framework reduces computational demand by relying on pre-established relationships while maintaining physically interpretable structures. The results indicate that the proposed approach can support real-time flood prediction in small streams under conditions like those examined in this study, although its applicability to other regions requires site-specific calibration and further validation. Full article

(This article belongs to the Section Hydrology)

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27 pages, 2198 KB

Open AccessArticle

Ecosystem Health of Andean–Amazonian Rivers: Integrating Macroinvertebrate Diversity, Microbiological Loads and Chemical Signatures Across Anthropogenic Gradients

by Daniela Alvear-Sayavedra, Daning Montaño-Ocampo, Mariana V. Capparelli, Jorge E. Celi, Marcela Cabrera and Rodrigo Espinosa

Water 2026, 18(9), 1106; https://doi.org/10.3390/w18091106 - 5 May 2026

Viewed by 1378

Abstract

The Western Amazon is a global biodiversity hotspot, yet the Upper Napo River Basin (UNRB) remains understudied regarding aquatic ecosystem health along anthropogenic gradients. We integrated benthic macroinvertebrate assemblages with physicochemical and microbiological indicators across 45 sites to assess ecological quality under four [...] Read more.

The Western Amazon is a global biodiversity hotspot, yet the Upper Napo River Basin (UNRB) remains understudied regarding aquatic ecosystem health along anthropogenic gradients. We integrated benthic macroinvertebrate assemblages with physicochemical and microbiological indicators across 45 sites to assess ecological quality under four impact scenarios: Few Threats (FT, reference sites; n = 6), Crop/Aquaculture (CA; n = 22), Gold Mining (GM; n = 10), and Wastewater Discharge (WD; n = 7). Analysis of 2285 individuals (62 families) revealed clear degradation across the anthropogenic gradient. Reference sites (FT) exhibited high integrity (q₀ = 24.3 families), establishing the regional baseline for Andean–Amazonian freshwater ecosystems. In stark contrast, GM sites showed catastrophic defaunation (q₀ = 9.9 families) coupled with extreme turbidity (1320 ± 1589 NTU) and heavy metal mobilization (Fe: 430 ± 229 µg/L; Cu: 338 ± 128 µg/L), placing these reaches in “Bad” ecological status (Ecological Quality Ratio, EQR ≤ 0.16). Wastewater sites reached critical fecal coliform levels (33,708 ± 58,047 CFU/100 mL)—165-fold higher than FT sites—indicating severe sanitary impairment and community collapse (EQR = 0.28, dominated by Chironomidae at 80%). The application of ASPT (Average Score Per Taxon) and EQR proved essential for detecting functional shifts toward tolerant assemblages even when raw biotic scores appeared moderate. Crop/Aquaculture sites showed intermediate degradation (EQR = 0.37–0.38), reflecting chronic pesticide exposure and habitat loss. We conclude that gold mining and wastewater discharge are the primary drivers pushing the UNRB toward ecological collapse, with GM exerting the most severe impact on aquatic biodiversity. Safeguarding this global freshwater stronghold requires immediate implementation of multimetric biomonitoring, enhanced mining regulation, wastewater treatment infrastructure, and establishment of Indigenous-led fluvial reserves to maintain long-term connectivity. Full article

(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)

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19 pages, 6112 KB

Open AccessArticle

Influence of Longitudinal Aquifer Slope on Hyporheic Exchange and Flow Organization in Bounded Floodplain Aquifer Systems

by Uğur Boyraz and Emin Ayvaz

Water 2026, 18(9), 1105; https://doi.org/10.3390/w18091105 - 4 May 2026

Viewed by 844

Abstract

This study investigates the role of longitudinal aquifer slope in controlling stream–aquifer interaction within bounded floodplain aquifer systems. A series of numerical simulations were conducted to analyze groundwater flow patterns, hyporheic exchange fluxes, and contaminant transport behavior under varying slope conditions. The results [...] Read more.

This study investigates the role of longitudinal aquifer slope in controlling stream–aquifer interaction within bounded floodplain aquifer systems. A series of numerical simulations were conducted to analyze groundwater flow patterns, hyporheic exchange fluxes, and contaminant transport behavior under varying slope conditions. The results showed that increasing slope does not simply enhance hydraulic gradients but fundamentally reorganizes subsurface flow structure. As the slope increases, groundwater flow becomes progressively aligned with the stream, reducing lateral connectivity and confining exchange to a narrow corridor adjacent to the stream. This reorganization leads to the expansion of hydraulically inactive zones and a non-linear response in hyporheic exchange. Exchange flow rates initially increase at low to moderate slopes but decline beyond a threshold at higher slopes, despite higher local gradients. The transition begins at around a 2% slope and becomes pronounced within the range of approximately 3–7%, indicating a shift in flow regime rather than a continuous scaling of interaction intensity. Particle tracking analyses further reveal that slope controls the spatial distribution of contaminant vulnerability. While the overall extent of active transport zones decreases with increasing slope, localized transport potential intensifies near the stream boundary due to higher velocities and reduced residence times. These findings demonstrate that hydraulic gradient magnitude alone is insufficient to characterize stream–aquifer interaction and highlight the importance of flow geometry and connectivity. The results provide a process-based framework for understanding slope-controlled hyporheic exchange and offer insights for improving groundwater vulnerability assessment and management in alluvial systems. Full article

(This article belongs to the Section Hydrogeology)

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29 pages, 9689 KB

Open AccessArticle

Efficient Removal of Ammonium Nitrogen from Aquatic Systems Using Thermally and Alkali-Modified Diatomite and Zeolite

by Gulfairus Bizhanova, Maral Abdibattayeva, Wang Ping, Umut Mussina, Laura Kurbanova, Arman Zhumazhanov, Dana Akhmetzhanova, Ospan Doszhanov, Bekzat Ismukhanbetov, Didar Bolatova and Yerlan Doszhanov

Water 2026, 18(9), 1104; https://doi.org/10.3390/w18091104 - 4 May 2026

Viewed by 880

Abstract

Ammonium nitrogen (NH₄⁺-N) is a key biogenic pollutant in aquatic systems. This study evaluated natural diatomite (Aktobe region) and zeolite (Shankhanai, Zhetysu region) as low-cost, environmentally benign sorbents for NH₄⁺-N removal, and examined the effects of thermal [...] Read more.

Ammonium nitrogen (NH₄⁺-N) is a key biogenic pollutant in aquatic systems. This study evaluated natural diatomite (Aktobe region) and zeolite (Shankhanai, Zhetysu region) as low-cost, environmentally benign sorbents for NH₄⁺-N removal, and examined the effects of thermal (200–750 °C; 450 °C selected) and alkaline (0.5 M NaOH) treatments on their structural, textural and adsorption properties. Materials were characterized by XRD, XRF, FTIR, SEM-EDX and adsorption performance was assessed by kinetic and equilibrium experiments. Specific surface area and pore characteristics were determined from low-temperature nitrogen adsorption–desorption measurements, and the specific surface area was calculated using the Brunauer–Emmett–Teller (BET) method. Thermal treatment at 450 °C increased the specific surface area of diatomite (46.3 m²/g) and pore volume, and subsequent alkaline activation further enhanced adsorption activity. The modified diatomite achieved up to 84.6% removal of NH₄⁺-N with an equilibrium capacity q_max = 1.758 mg/g. Adsorption kinetics were best described by the pseudo-second-order (PSO) model, which may indicate a substantive role of surface chemical interactions. Equilibrium data were fitted with Langmuir and Freundlich models: the modified diatomite fitted Langmuir best (R² = 0.999), which may suggest predominance of a monolayer adsorption mechanism under the studied conditions, whereas natural samples and the zeolite were better described by the Freundlich model, reflecting likely surface energetic heterogeneity. Separation factor values (R_L = 0.068–0.643) indicate favorable adsorption within the investigated concentration range. The point of zero charge (pHpzc) was determined for all sorbents (5.3–6.3), confirming that at pH 7 the surface carries a negative charge favorable for electrostatic attraction of NH₄⁺ cations. Reusability tests over five consecutive adsorption–desorption cycles showed that modified diatomite and modified zeolite retained 93.4% and 92.3% of their initial removal efficiency, respectively, indicating acceptable stability under the applied regeneration conditions. These results demonstrate the potential of alkaline-modified diatomite and zeolite as effective sorbents for ammonium removal from wastewaters, contributing to the mitigation of eutrophication risks. Full article

(This article belongs to the Special Issue Advanced Adsorbent-Based Technologies for Efficient Wastewater Treatment)

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33 pages, 23227 KB

Open AccessArticle

Correcting a Transboundary Aquifer Delineation for the U.S.–Mexico Border Region Based on Hydrogeologic Criteria

by Barry Hibbs and Alfredo Granados-Olivas

Water 2026, 18(9), 1103; https://doi.org/10.3390/w18091103 - 4 May 2026

Viewed by 1083

Abstract

A widely reproduced error in hydrogeologic maps originated from a provisional delineation drawn in the mid-1990s to depict the southern extent of the Mesilla Bolson aquifer along the western margin of the El Paso–Juárez metropolitan area. The delineation was created solely to satisfy [...] Read more.

A widely reproduced error in hydrogeologic maps originated from a provisional delineation drawn in the mid-1990s to depict the southern extent of the Mesilla Bolson aquifer along the western margin of the El Paso–Juárez metropolitan area. The delineation was created solely to satisfy a U.S. Environmental Protection Agency contractual milestone during early binational groundwater inventory efforts and was never intended to represent a final hydrogeologic basin limit. Nevertheless, the outline persisted, became institutionalized in reports, models, management documents, and public imagery, and was ultimately labeled the “Mesilla/Conejos–Médanos Basin Transboundary Aquifer,” where it continues to be treated as a valid transboundary aquifer delineation. This paper documents the origin of the provisional delineation and proposes a revised delineation for the Mesilla/Conejos–Médanos Basin Transboundary Aquifer, based on internationally recognized definitions of transboundary aquifers and groundwater basins, including United Nations frameworks, and established scientific criteria. These criteria include basin-scale geologic and structural controls, hydrostratigraphic continuity, groundwater divides, and permeability contrasts at basin interfaces. Results indicate that the newly defined aquifer delineation falls within Mexico’s much larger administrative Acuífero Conejos–Médanos (0823), a unit that represents groundwater management jurisdiction in Mexico rather than solely a hydrogeologic basin. The proposed transboundary aquifer is defined on hydrogeological principles and does not coincide with either the administrative unit of Mexico or the historic provisional outline that has become widely used by multiple binational entities and by different experts in groundwater science. Full article

(This article belongs to the Section Hydrogeology)

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18 pages, 2668 KB

Open AccessArticle

Fluorescence Properties and Sources of Dissolved Organic Matter in Xinghua River, a Typical Urban River

by Mingyue Li, Yongchao Wang, Shuling Chen, Wenhui Liu, Guodong Chai, Zhongfeng Jiang and Fang Yang

Water 2026, 18(9), 1102; https://doi.org/10.3390/w18091102 - 4 May 2026

Viewed by 870

Abstract

This work focused on the Xinghua River, a typical urbanizing river, to investigate how different anthropogenic activities affect the composition, sources, and environmental impact of dissolved organic matter (DOM) during urbanization. Using fluorescence spectroscopy combined with multivariate statistics, we systematically explored DOM characteristics [...] Read more.

This work focused on the Xinghua River, a typical urbanizing river, to investigate how different anthropogenic activities affect the composition, sources, and environmental impact of dissolved organic matter (DOM) during urbanization. Using fluorescence spectroscopy combined with multivariate statistics, we systematically explored DOM characteristics and their response to urbanization. A total of four fluorescent components were identified, including protein-like components C1 and C3, and humic-like components C2 and C4, with protein-like substances constituting the major fraction of DOM. Fluorescence indices indicated that DOM in the Xinghua River was primarily derived from autochthonous sources (FI > 1.9), with a low degree of humification reflecting the dominance of fresh organic matter input during urbanization. Spatial analysis revealed that from upstream to downstream, the source of DOM gradually shifted from autochthonous dominance to increased allochthonous input, accompanied by increasing trends in both protein-like and humic-like components, indicating an accumulative effect of anthropogenic activities along the river. 2D-COS further revealed that the transformation sequence of DOM components along the flow direction was C3 → C1 → C4 → C2, suggesting that tyrosine/tryptophan-like substances were the most sensitive to anthropogenic disturbance. Redundancy analysis identified total phosphorus (TP), total dissolved solids (TDS), and permanganate index (COD_Mn) as the key environmental factors influencing DOM distribution, highlighting the synergistic regulatory roles of nitrogen and phosphorus nutrients and organic pollution loads on DOM composition. This study not only elucidates the gradient effects of human activities on DOM in the Xinghua River but also provides a scientific basis for water management in urban rivers worldwide, particularly for zone-based control and source-oriented management. Full article

(This article belongs to the Special Issue Water Environment Pollution and Control, 4th Edition)

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17 pages, 6793 KB

Open AccessArticle

Mechanisms of Metal Particle Release from Pipe Scales in Ductile Iron Water Supply Pipelines: Control by Water Quality Parameters

by Yu Chang, Menghao Fang, Qing Lu, Dawei Zhang and Weiying Li

Water 2026, 18(9), 1101; https://doi.org/10.3390/w18091101 - 4 May 2026

Viewed by 808

Abstract

To clarify the control mechanism of water quality parameters on metal particle release from pipe scales in aging ductile iron water supply pipelines (service life > 20 years), this study conducted single-factor experiments to explore the effects of pH, temperature, concentration of humic [...] Read more.

To clarify the control mechanism of water quality parameters on metal particle release from pipe scales in aging ductile iron water supply pipelines (service life > 20 years), this study conducted single-factor experiments to explore the effects of pH, temperature, concentration of humic acid (HA) and Mn²⁺ on Fe, Mn, and Al particle release. Combined with inductively coupled plasma optical emission spectrometry (ICP-OES) for quantitative detection, first-order/second-order kinetic fitting, and X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) characterization, the results showed that an increase in temperature generally promoted the aggregation and sedimentation of metal particles, among which Fe and Mn particles were more sensitive to temperature changes. pH affected the sedimentation process by controlling metal ion speciation and particle surface charge: low pH significantly accelerated pipe scale dissolution, while weakly alkaline conditions prolonged particle suspension time. Low-concentration HA (0.5 mg/L) promoted particle dissolution, whereas high-concentration HA (1.0–2.0 mg/L) extended particle retention time through surface coating. Mn²⁺ concentration exhibited an obvious concentration-dependent effect: the range of 20–50 μg/L enhanced particle suspension stability, while 80–100 μg/L accelerated particle aggregation and sedimentation. The pipe scales mainly consisted of Fe₃O₄, Fe₂O₃, Mn₃O₄, and Al₂O₃, with metal release regulated by the “element complexation–particle aggregation–crystal growth” pathway. Particle sedimentation followed first-order kinetics. Controlling pH at 7.0, temperature < 30 °C, and reducing HA/Mn²⁺ concentrations effectively weakened metal particle migration. This study reveals the coupled effect mechanism of water quality parameters, providing theoretical and technical support for optimizing water quality control and solving the “yellow water” problem. Full article

(This article belongs to the Section Urban Water Management)

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10 pages, 649 KB

Open AccessArticle

Assessing the Performance of a Tubular Solar Still in an Arid Region Using Various Water Types

by Tamadhor Almahmoud, Litty Mary Abraham, Mohammad Abdullah Alolayan and Bader Shafaqa Al-Anzi

Water 2026, 18(9), 1100; https://doi.org/10.3390/w18091100 - 4 May 2026

Viewed by 5498

Abstract

The performance of a tubular solar still in an arid region was evaluated for producing freshwater from various water sources. The water sources fed to the tubular solar still were blowdown from a seawater desalination plant, recovered water from an oil production facility, [...] Read more.

The performance of a tubular solar still in an arid region was evaluated for producing freshwater from various water sources. The water sources fed to the tubular solar still were blowdown from a seawater desalination plant, recovered water from an oil production facility, rejected seawater from a reverse osmosis treatment plant, seawater, and rejected groundwater from a reverse osmosis treatment plant. The TDS for these water sources ranged from 17,210 mg/L for groundwater to 221,710 mg/L for produced water. Compared with other water types, produced water had distinct characteristics: low pH, a petroleum-like odor, and a reddish-brown color. The estimated average production rates were 5.1, 5.9, 6.1, 6.6, and 6.8 L/m²·day for produced water, reverse osmosis-rejected water, desalination plant blowdown, seawater, and reverse osmosis-rejected groundwater. Different TSS designs were examined to determine whether production rates could be improved using tap water. Production increased slightly when a blackened basin, steel mesh, or both were applied as heat-absorption enhancements. Therefore, the tubular solar still without any enhancements was found to be a better option due to its lower cost and simpler design. The composition of the residual salts (65–73%) did not meet the 97% standard set by the FAO. The results of the study are promising for future upscaling projects aimed at enhancing water security in rural areas and arid regions. Full article

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

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17 pages, 2522 KB

Open AccessArticle

A Three-Dimensional Probabilistic Framework for Stability Assessment of Unsaturated Slopes Under Rainfall Infiltration

by Qingguo Wang, Yabing Ma, Mingyang Ren and Heng Liu

Water 2026, 18(9), 1099; https://doi.org/10.3390/w18091099 - 4 May 2026

Viewed by 893

Abstract

Given the escalating impacts of global climate change and extreme weather events, the accurate stability assessment of rainfall-induced landslides necessitates a comprehensive consideration of both seepage processes and the inherent spatial variability of soils. Traditional deterministic and two-dimensional (2D) analyses often fail to [...] Read more.

Given the escalating impacts of global climate change and extreme weather events, the accurate stability assessment of rainfall-induced landslides necessitates a comprehensive consideration of both seepage processes and the inherent spatial variability of soils. Traditional deterministic and two-dimensional (2D) analyses often fail to capture the multi-dimensional kinematic features of slope failures and the stochastic nature of soil heterogeneity, thereby leading to inaccurate risk assessments. This study proposes a three-dimensional (3D) slope reliability analysis framework. Within this framework, a 3D slope geometric model is constructed using GeoStudio 2025.1.0 software, and seepage analysis is conducted by the SEEP3D module. To account for soil spatial variability, the Karhunen–Loève (K-L) expansion method is employed to discretize key shear strength parameters (effective cohesion and effective angle of internal friction). The factor of safety (F_s) is evaluated using the 3D simplified Bishop method, which is then coupled with Monte Carlo simulations to determine the probability of failure (P_f). The results show that rainfall infiltration causes progressive dissipation of shallow matric suction and a significant rise in the groundwater table near the slope toe, resulting in reduced effective stress in the critical resistance zone. As rainfall intensity increases, the F_s decreases approximately linearly from 1.14 to 0.90, whereas the P_f increases nonlinearly from nearly 0 to 98.36%. Under the rainstorm condition, although the F_s remains above unity at 1.063, the corresponding P_f reaches 23%, indicating that deterministic evaluation based only on the F_s may underestimate the actual failure risk. The proposed framework provides a quantitative tool for evaluating rainfall-induced slope instability by integrating transient hydraulic response, three-dimensional spatial variability, and probabilistic reliability assessment. Full article

(This article belongs to the Special Issue Disaster Analysis and Prevention of Dam and Slope Engineering)

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19 pages, 16655 KB

Open AccessArticle

Multivariate Joint Risk Assessment of Small- and Medium-Sized River Flood in Arid and Semi-Arid Regions Based on Vine Copula

by Boyan Sun, Xiaomin Liu, Guoqing Wang, Ping Miao, Kang Xie and Hongli Ma

Water 2026, 18(9), 1098; https://doi.org/10.3390/w18091098 - 3 May 2026

Viewed by 895

Abstract

Flood risk assessment is essential for flood control and disaster mitigation in arid and semi-arid river basins, where conventional univariate and bivariate frequency analyses struggle to capture nonlinear dependence among flood variables and often underestimate extreme synergistic risks. This study focuses on the [...] Read more.

Flood risk assessment is essential for flood control and disaster mitigation in arid and semi-arid river basins, where conventional univariate and bivariate frequency analyses struggle to capture nonlinear dependence among flood variables and often underestimate extreme synergistic risks. This study focuses on the Wulanmulun River Basin in Inner Mongolia and employs long-term observations from the Zuanlongwan and Wangdaohengta hydrological stations. A trivariate D-vine Copula model was constructed to jointly characterize peak discharge, total flood volume, and water level. Optimal vine structures differ between the stations (Qp–H–W and W–Qp–H) and outperform traditional Copula models in representing extreme joint risks. The ternary joint return periods reveal two distinct flood risk transmission modes, “jump” and “accumulation”, and joint exceedance probabilities under low, medium, high, and ultra-high-risk scenarios are 6.4%, 31.95%, 37.64%, and 5.75% at Zuanlongwan, and 4.7%, 35.24%, 45.78%, and 0.53% at Wangdaohengta, indicating concentration in medium-to-high risk ranges. The validation at Longtouguai Station showed an error RSME of 0.0630 and an R² of 0.905, confirming the reliability of the model framework. These results indicate that the proposed framework can effectively capture multivariate flood dependencies and provide a scientific basis for flood control design, risk zoning, and emergency management of small and medium rivers in arid and semi-arid regions. Full article

(This article belongs to the Special Issue "Watershed–Urban" Flooding and Waterlogging Disasters)

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16 pages, 1535 KB

Open AccessArticle

Mulching Improved Soil Water, Plant Growth, and Seed Yield of Sunflower Under Raised Bed–Furrow Irrigation Method

by Zhonglin Wu, Rajesh Kumar Soothar, Habibullah Memon, Farman Ali Chandio and Sher Ali Shaikh

Water 2026, 18(9), 1097; https://doi.org/10.3390/w18091097 - 3 May 2026

Viewed by 1023

Abstract

Plastic film mulching combined with raised bed–furrow irrigation is an effective technique for enhancing the seed yield, oil contents, and plant-level water use efficiency of sunflower cultivation, while also optimizing water footprint. In this study, a field experiment was carried out at the [...] Read more.

Plastic film mulching combined with raised bed–furrow irrigation is an effective technique for enhancing the seed yield, oil contents, and plant-level water use efficiency of sunflower cultivation, while also optimizing water footprint. In this study, a field experiment was carried out at the experimental station of the Department of Irrigation and Drainage during 2023–2024. The trial involved three types of raised bed–furrow irrigation (raised beds with 60, 45, and 30 cm ridges and 30 cm furrows) with and without mulching practices. The results revealed that the treatments combining mulching with raised beds showed higher soil temperature and moisture contents compared to non-mulching treatments. The highest seed yield and oil content were recorded in furrow irrigation with mulching, representing a 35% increase in yield and a 28% increase in oil content compared to the control treatment. Seed yield was positively correlated with oil content. Additionally, the highest plant-level water use efficiency was observed in a raised bed 45 cm in size with mulching, while the highest total water footprints were recorded in a raised bed with a 60 cm ridge and non-mulch treatment, both exceeding the control treatment. It is concluded that sunflower cultivation under mulching combined with raised bed–furrow irrigation significantly enhances crop and water productivity. Full article

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

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26 pages, 12014 KB

Open AccessArticle

The Reliability of SBR System During COVID-19 and Its Impact on Water Quality of a Small Flysch River in Protected Areas

by Ewa Dacewicz, Karol Plesiński and Ewa Łobos-Moysa

Water 2026, 18(9), 1096; https://doi.org/10.3390/w18091096 - 2 May 2026

Viewed by 1003

Abstract

This study assessed the impact of pandemic-related changes in treated wastewater on surface water quality and ecological status of the Raba River within the Natura 2000 site. Particular attention to the reliability of the Kasinka Mała wastewater treatment plant operating in this protected [...] Read more.

This study assessed the impact of pandemic-related changes in treated wastewater on surface water quality and ecological status of the Raba River within the Natura 2000 site. Particular attention to the reliability of the Kasinka Mała wastewater treatment plant operating in this protected area during the two study periods—pre-pandemic (PP) and COVID-19 (CP)—was given. For this purpose, current standard monitoring methods (ecological status of a small flysch stream, existing and potential threats to the Natura 2000 site) and extended monitoring methods (river’s utility values, technological reliability of the treatment plant operating with SBR technology, reliability rating of the river as a sewage receiver) were used. The results indicated that biodegradable carbon compounds (as dissolved and suspended forms) and ammonium nitrogen were the dominant factors determining water quality. Their presence reduced the Raba River’s utility value—determined by what is required of surface water treatment—by at least one class. During the CP, the reliability analysis showed that the river remained in a reduced class for 145 days due to elevated BOD₅ and nearly one-third of the year due to elevated TSS levels. For approximately half of the year, ammonium nitrogen concentrations exceeded the threshold of 1.8 mg·dm⁻³, thereby further reducing the class of water quality. Technological reliability of the WWTP during PP for BOD₅, COD, TSS, NH₄⁺–N, and PO₄⁻³–P was 43%, 100%, 30%, 86%, and 100%, respectively. This means that permitted values of COD and PO₄⁻³–P were maintained. The exceedances of limits concerned BOD₅ (25 mg O₂·dm⁻³ for 208 days), TSS (35 mg·dm⁻³ for 256 days), and NH₄⁺–N (15 mg·dm⁻³ for 51 days). During CP, the technological reliability of the WWTP decreased rapidly for the following pollutants to 5%, 18%, 18%, 30%, and 89%, respectively. This means that permissible concentrations of BOD₅ (25 mg O₂·dm⁻³ for 347 days), COD (125 mg O₂·dm⁻³ for 241 days), TSS (35 mg·dm⁻³ for 299 days), NH₄⁺–N (15 mg·dm⁻³ for 256 days), and PO₄⁻³–P (2 mg·dm⁻³ for 40 days) were exceeded. A two-year monitoring campaign has shown that small flysch rivers receiving treated wastewater may experience prolonged changes in water quality under conditions of increased anthropopressure. Effective ecosystem protection should, therefore, include extended monitoring and stricter management of BOD₅, TSS, and NH₄⁺–N in SBR systems in protected areas. Full article

(This article belongs to the Special Issue Advances in Hydrology and Hydraulics: Integrating Aquatic Biota and River Ecosystem Processes)

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21 pages, 6011 KB

Open AccessArticle

Urban Runoff Pollution Forecasting in the Yangtze River Basin: A Physics-Informed Data-Driven Framework Enhanced with Cluster-Based Transfer Learning

by Yacheng Sun, Yasong Chen, Yuzhen Li, Tingting Li and Wenlong Zhang

Water 2026, 18(9), 1095; https://doi.org/10.3390/w18091095 - 2 May 2026

Viewed by 969

Abstract

Accurate forecasting of urban rainfall-runoff pollution across large river basins is essential for urban water management. However, this task faces formidable challenges due to the scarcity of locally monitored data and the heterogeneity in hydrological and pollution processes. To address these challenges, we [...] Read more.

Accurate forecasting of urban rainfall-runoff pollution across large river basins is essential for urban water management. However, this task faces formidable challenges due to the scarcity of locally monitored data and the heterogeneity in hydrological and pollution processes. To address these challenges, we proposed a novel three-tiered framework comprising (1) functional area clustering using 16-dimensional features to identify zones with shared pollution mechanisms and establish a physical parameter library; (2) a hybrid physics-informed data-driven model integrating SWMM with a Residual-BiLSTM-Multi-Head Attention (RLA) model; and (3) cluster-based transfer learning enabling predictions in data-scarce zones. The framework’s efficacy was demonstrated through a multi-tiered dataset for the Yangtze River Basin. First, a knowledge base comprising 2390 reported rainfall events across 57 functional areas was synthesized to inform the functional clustering and establish a shared physical parameter library. Subsequently, intensive field monitoring from two representative residential areas was used to train and validate the hybrid model. In data-rich zones within a cluster, the model achieved high accuracy (R² > 0.82). For data-scarce zones within the same functional cluster, the model maintained a promising performance (R² > 0.5). This study presents a novel basin-scale framework, with its initial application and preliminary validation in the Yangtze River Basin. Full article

(This article belongs to the Special Issue AI, Machine Learning and Digital Twin Applications in Water, 2nd Edition)

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25 pages, 9140 KB

Open AccessArticle

The Sustainability Challenge of Water Resources in Arid Rural Areas Under Drought Constraints and Increasing Consumption Pressure: A Case Study of the Guercif Plain (Morocco)

by Lamfaddal El Hani, Nir Y. Krakauer, Ridouane Kessabi, Mohamed Belmahi, Jawad Khachab and Abdelouahed Bouberria

Water 2026, 18(9), 1094; https://doi.org/10.3390/w18091094 - 2 May 2026

Viewed by 1131

Abstract

This article analyzes the state of water resources in the Guercif Plain (Morocco) under the combined effects of drought and increasing consumption pressures. The study adopts a quantitative and analytical approach based on climatic and hydrological data, demographic information, and Landsat satellite imagery. [...] Read more.

This article analyzes the state of water resources in the Guercif Plain (Morocco) under the combined effects of drought and increasing consumption pressures. The study adopts a quantitative and analytical approach based on climatic and hydrological data, demographic information, and Landsat satellite imagery. The main findings reveal pronounced rainfall variability with an overall declining tendency, with drought years accounting for approximately 58% of the observation period. This climatic context has been accompanied by strong interannual fluctuations in the discharge of Oued Melloulou, with a slight long-term declining trend, along with a continuous and accelerating groundwater decline in the Tafrata aquifer at an average rate of 0.98 m per year. The analysis also indicates an estimated urban water deficit approaching 77% under peak demand conditions in 2025. Furthermore, NDVI-based analysis of satellite imagery highlights a marked expansion of irrigated areas in the Guercif Plain, increasing from about 2% of the total plain area in 1985 to approximately 9% in 2020. This vegetation expansion is largely associated with irrigation development, suggesting increasing pressure on groundwater resources rather than recovery linked to rainfall conditions. Overall, the findings raise critical concerns regarding the long-term sustainability of water resources and underscore the need for integrated and adaptive water-management strategies under persistent drought conditions. Full article

(This article belongs to the Section Water and Climate Change)

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37 pages, 1376 KB

Open AccessReview

Sustainable Recirculating Aquaculture Systems (RAS): Development and Challenges

by Ayesha Kabir, Abubakar Shitu, Zhangying Ye, Xian Li, He Ma, Gang Liu, Songming Zhu, Jing Zou, Ying Liu and Dezhao Liu

Water 2026, 18(9), 1093; https://doi.org/10.3390/w18091093 - 2 May 2026

Viewed by 2323

Abstract

The recirculating aquaculture system (RAS) marks a significant shift in global aquaculture, transitioning to controlled, land-based production. This review highlights technological advancements that enable the treatment and reuse of over 90% of water, thereby enhancing water quality and production efficiency. These features position [...] Read more.

The recirculating aquaculture system (RAS) marks a significant shift in global aquaculture, transitioning to controlled, land-based production. This review highlights technological advancements that enable the treatment and reuse of over 90% of water, thereby enhancing water quality and production efficiency. These features position RAS as a cornerstone of sustainable seafood production. This review introduces the RAS Readiness Level (RRL) framework which is a novel, structured approach to assess the commercial maturity of emerging RAS technologies. Applying the RRL to six key technological domains (from digital AI systems to biological PHB recovery) reveals a pervasive pilot-scale purgatory where most innovations stagnate at RRL 4–6. It further addresses advanced processes such as membrane bioreactors, denitrification reactors, and the conversion of waste into valuable products. Furthermore, this review addresses persistent challenges, including high energy demand, economic viability, and the accumulation of pathogens. Finally, it focuses on the emergent integration of the Internet of Things (IoT) and artificial intelligence (AI), which are revolutionizing RAS management through data-driven optimization. By synthesizing current innovations, this review envisions a future of intelligent, closed-loop RAS where advanced IoT- and AI-driven technologies optimize water quality and feeding strategies to minimize ecological impact while enhancing sustainability and productivity. Full article

(This article belongs to the Special Issue Advanced Water Management for Sustainable Aquaculture)

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22 pages, 3188 KB

Open AccessArticle

A Binocular Vision Method for Measuring Hydraulic Bulging Deformation of Geomembranes

by Zhuang Zhao, Xi Yang, Canping Jiang, Feng Yi and Haimin Wu

Water 2026, 18(9), 1092; https://doi.org/10.3390/w18091092 - 2 May 2026

Viewed by 937

Abstract

Geomembranes are extensively used for seepage control in the reservoir of pumped-storage power stations due to their superior deformability, ease of construction, and low cost. The deformation behavior of geomembranes under high hydraulic pressure is of great importance for seepage-control design and operational [...] Read more.

Geomembranes are extensively used for seepage control in the reservoir of pumped-storage power stations due to their superior deformability, ease of construction, and low cost. The deformation behavior of geomembranes under high hydraulic pressure is of great importance for seepage-control design and operational safety evaluation. Nevertheless, existing hydrostatic pressure resistance tests cannot effectively measure the hydraulic bulging deformation of geomembranes subjected to water pressure. This study proposes a non-contact binocular vision method to quantify the hydraulic bulging deformation of geomembranes. The method combines underwater camera calibration, image enhancement, stereo matching, triangulation, and three-dimensional reconstruction to achieve both visualization and accurate measurement of geomembrane deformation. After experimental validation and accuracy calibration, the proposed method was preliminary applied to four geomembrane materials, including HDPE, LLDPE, PVC, and TPO, under hydraulic loading. The results show that the measurement error is less than 5% in the large-deformation range under medium and high water pressures. The method can effectively capture the hydraulic bulging behavior of geomembranes and accurately characterize the deformation features of different materials under high hydraulic pressure. This study provides a practical technical approach for underwater deformation measurement of geomembranes and supports seepage-control design and operational safety monitoring. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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28 pages, 4830 KB

Open AccessArticle

Wave Transmission and Ice Drift for Ice Floe Under Waves

by Izmail Kantarzhi and Maksim Afonyushkin

Water 2026, 18(9), 1091; https://doi.org/10.3390/w18091091 - 2 May 2026

Viewed by 769

Abstract

A study was conducted on the interaction of surface gravity waves with a relatively thin, free-floating ice floe compared to the height of the waves. Physical and numerical modeling, as well as analytical research, were used. An overview of scientific works on the [...] Read more.

A study was conducted on the interaction of surface gravity waves with a relatively thin, free-floating ice floe compared to the height of the waves. Physical and numerical modeling, as well as analytical research, were used. An overview of scientific works on the research topic is presented. The physical model consisted of an experimental setup (wave flume) with a wooden plate exposed to gravitational harmonic waves of different lengths and periods. The numerical model is based on calculations performed in the LS-DYNA program, where the fluid was simulated using the Euler–Lagrange method, and solid bodies were considered rigid. Analytical studies use the theory of interaction of small-amplitude waves with floating breakwaters. It is shown that as the wave height increases for conditions of interaction between waves and ice floes of almost identical horizontal dimensions, one end of the floating body sinks into the water, which leads to a significant reduction in the drift speed of the ice floe. Formulas have been obtained that express the ratio of the ice floe’s speed to the wave velocity, as well as the ratio of the height of the incident waves to the height of the transmitted waves, depending on the ratio of the wavelength to the horizontal dimensions of the floating ice floe. Full article

(This article belongs to the Special Issue Recent Advances in Hydraulic Machinery and Its Application in Marine Engineering)

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30 pages, 5996 KB

Open AccessArticle

A Sustainable Teaching Framework for Hydraulic Model Experiment Course: Practice-Oriented Optimization Based on Integrated Unit-Based Instruction

by Dan Liu, Jianyong Hu, Yongye Li, Shiang Mei, Haitao Zhao, Zhenzhu Meng, Cundong Xu, Jinxin Zhang, Jie Jin, Miaoyan Liu, Yuqiang Wang and Wanling Wu

Water 2026, 18(9), 1090; https://doi.org/10.3390/w18091090 - 1 May 2026

Viewed by 972

Abstract

Addressing the challenges of vague ability assessment, delayed teaching adjustment, and fixed cognitive challenge levels in sustainable engineering practice courses, this study proposes a “goal elevation-matrix evaluation-dynamic regulation” tripartite coupled sustainable teaching model. The model employs a value-oriented assessment matrix as the core [...] Read more.

Addressing the challenges of vague ability assessment, delayed teaching adjustment, and fixed cognitive challenge levels in sustainable engineering practice courses, this study proposes a “goal elevation-matrix evaluation-dynamic regulation” tripartite coupled sustainable teaching model. The model employs a value-oriented assessment matrix as the core diagnostic tool, integrating a dual-threshold regulation mechanism and standard iteration strategy within a four-year “design-implementation-diagnosis-iteration” closed loop. Empirical evidence demonstrates that ① a three-tier diagnostic model (overall-module-indicator attainment levels) identifies structural problems of the teaching content and pinpoints the key bottleneck; ② replacing redundant high-scoring modules with basic skill modules eliminates extreme values, improves distribution gradients, and trends to class performance at 75~85%; ③ iterative standard calibration supports progressive student competence development along a “familiar problems → new challenges” pathway. This study provides an empirically validated methodological framework for systematically implementing “scientific rigor, practicality, and appropriate challenge” in engineering practice courses while fostering sustainable engineering literacy. Full article

(This article belongs to the Special Issue Water and Education: Teaching Sustainability, Managing Risks, and Shaping the Future)

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41 pages, 11716 KB

Open AccessSystematic Review

Balancing Groundwater Use and Protection in Coastal Aquifers: A Review of Climate Impacts, Management Strategies, and Governance Approaches

by Cris Edward F. Monjardin, Jerime Chris F. Mendez, Rose Danielle G. Hilahan, Maria Gemma Lou Hermosa, Elmo Jr Z. Almazan and Kevin Paolo V. Robles

Water 2026, 18(9), 1089; https://doi.org/10.3390/w18091089 - 1 May 2026

Viewed by 1188

Abstract

Coastal aquifers are essential freshwater sources for domestic, agricultural, and industrial use, particularly in regions where surface water is limited. However, these systems face growing stress from saltwater intrusion, climate-driven reductions in recharge, sea level rise, and intensified groundwater extraction. This review synthesizes [...] Read more.

Coastal aquifers are essential freshwater sources for domestic, agricultural, and industrial use, particularly in regions where surface water is limited. However, these systems face growing stress from saltwater intrusion, climate-driven reductions in recharge, sea level rise, and intensified groundwater extraction. This review synthesizes recent research on coastal aquifer responses to these pressures, highlighting the interplay between natural hydrogeologic conditions and human-induced demand. Across deltaic and sedimentary systems, studies consistently show declining groundwater levels, the landward migration of saline interfaces, and reduced aquifer buffering capacity, especially in areas with high evaporation and limited recharge. The review also evaluates emerging strategies to preserve coastal groundwater security. Integrated hydrological models, managed aquifer recharge (MAR), optimized abstraction schemes, and remote sensing-based monitoring are advancing adaptive management capabilities. In parallel, policy and nature-based interventions—such as aquifer protection zoning, wetland rehabilitation, and dune system restoration—support long-term resilience by enhancing natural recharge and reducing vulnerability. The overall findings reveal the need for climate-informed and locally tailored groundwater management. Future efforts should prioritize coupling high-resolution climate projections with aquifer system models, evaluating MAR viability in saline-prone environments, and strengthening collaborative governance frameworks to ensure sustainable and equitable use of coastal aquifers. Full article

(This article belongs to the Section Hydrology)

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9 pages, 758 KB

Open AccessArticle

An Assessment of the Suitability of Selected Analytical Procedures Based on EN ISO 10705-2:2001 and EN ISO 10705-3:2024 for the Determination of Somatic Coliphages in Water Intended for Human Consumption

by Marta Bartosik, Renata Matuszewska, Łukasz Mąka and Jolanta Solecka

Water 2026, 18(9), 1088; https://doi.org/10.3390/w18091088 - 1 May 2026

Viewed by 770

Abstract

The objective of this study was to evaluate selected analytical procedures based on EN ISO 10705-2:2001 and EN ISO 10705-3:2024 for the determination of somatic coliphages in 100 mL water samples, taking into account the requirements of Directive (EU) 2020/2184, and to identify [...] Read more.

The objective of this study was to evaluate selected analytical procedures based on EN ISO 10705-2:2001 and EN ISO 10705-3:2024 for the determination of somatic coliphages in 100 mL water samples, taking into account the requirements of Directive (EU) 2020/2184, and to identify a procedure that can be adapted for routine analyses, as well as points at which laboratories may encounter difficulties. The study was conducted on two types of water samples: Type 1, comprising groundwater and treated water, and Type 2, comprising surface water. Samples were collected from water treatment plants at the point of distribution network supply (treated water), deep well intakes, and surface intakes (raw water). The study demonstrated the limited reliability of the procedure when applied to routine analyses. The recovery obtained for the method incorporating the selected modifications under the tested conditions was 72% for Type 1 water samples and 73% for Type 2 water samples. The introduction of legal regulations on the quality of water intended for human consumption, along with the requirement to test a new parameter for operational purposes, can pose a significant challenge for laboratories performing water analyses. Full article

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

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34 pages, 20321 KB

Open AccessArticle

Dynamic Mode Decomposition for Forecasting Flood-Driven Sedimentation at a River Mouth: A Data-Driven Coastal Modelling

by Anıl Çelik, Abdüsselam Altunkaynak and Mehmet Özger

Water 2026, 18(9), 1087; https://doi.org/10.3390/w18091087 - 1 May 2026

Viewed by 816

Abstract

Accurate forecasting of sediment accumulation under extreme hydrodynamic forcing is essential for coastal engineering design and harbor management. This study evaluates the performance of Dynamic Mode Decomposition (DMD), optimized DMD (optDMD), and optimized DMD with stability constraints (optDMDs) for reconstructing and forecasting sediment [...] Read more.

Accurate forecasting of sediment accumulation under extreme hydrodynamic forcing is essential for coastal engineering design and harbor management. This study evaluates the performance of Dynamic Mode Decomposition (DMD), optimized DMD (optDMD), and optimized DMD with stability constraints (optDMDs) for reconstructing and forecasting sediment accumulation height fields at the Dilderesi River mouth under a 50-year return period flood scenario. Sediment height fields generated using Delft3D are represented through reduced-order modal decompositions and the truncation rank is determined based on reconstruction-error analysis. Although all formulations reproduce the training data with negligible error, their predictive behavior differs during temporal extrapolation. Standard DMD exhibits rapid error growth at longer lead times. The optDMD formulation improves short- and intermediate-horizon performance but shows gradual degradation at extended lead times. Optimized DMD with stability constraints provides the most consistent long-horizon forecasts, maintaining high Nash–Sutcliffe efficiency and low RMSE across the full 9 h prediction interval. Examination of the continuous-time eigenvalue distributions and modal dynamics indicates that spectral characteristics of the reduced-order representation govern forecast robustness. The results demonstrate that enforcing spectral stability within reduced-order frameworks substantially enhances morphodynamic forecasting reliability under extreme flood conditions. The proposed approach provides a computationally efficient and physically consistent tool for sediment dynamics prediction in coastal engineering applications. Full article

(This article belongs to the Section Hydrology)

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15 pages, 8832 KB

Open AccessArticle

Formation Mechanisms and Hydrogeochemical Evolution of a Metasilicate-Strontium Rich Mineral Water in a Subtropical Volcanic Terrain, East China

by Guang Li, Jie Guo, Yewei Song and Fengshan Ma

Water 2026, 18(9), 1086; https://doi.org/10.3390/w18091086 - 1 May 2026

Viewed by 785

Abstract

Natural mineral waters hosted in volcanic terrains are globally significant, but the co-enrichment mechanisms of metasilicate and strontium remain poorly understood. Here we investigate a Jurassic volcanic-hosted mineral water source in eastern China using hydrochemical analysis, ¹⁴C dating, stable isotopes, and structural [...] Read more.

Natural mineral waters hosted in volcanic terrains are globally significant, but the co-enrichment mechanisms of metasilicate and strontium remain poorly understood. Here we investigate a Jurassic volcanic-hosted mineral water source in eastern China using hydrochemical analysis, ¹⁴C dating, stable isotopes, and structural analysis. The groundwater is of Ca–Mg–HCO₃ type with slightly alkaline pH (7.44–7.63). Metasilicate (26.4–32.9 mg/L) and strontium (0.40–0.83 mg/L) co-enrichment is governed by plagioclase weathering in a bicarbonate-dominated, weakly alkaline environment where

{S r H C O}_{3}^{+}

ion pairs enhance strontium mobility. Pearson-corrected ¹⁴C ages of 3900–4900 years reveal that millennial-scale residence time is critical for sufficient water-rock interaction and attainment of regulatory thresholds. A conduit-barrier system formed by NW-trending extensional-shear and NNE-trending compressional-shear faults controls groundwater flow paths and residence times, leading to systematic inter-well hydrochemical differentiation. These findings provide a theoretical basis for the genetic identification, potential evaluation, and sustainable management of high-quality mineral water resources in volcanic terrains. Full article

(This article belongs to the Special Issue Hydrogeochemical Characterization and Flow System of Groundwater in Volcanic Aquifers)

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29 pages, 7698 KB

Open AccessArticle

Assessing Flood Vulnerability of Landfills in Southern New Jersey: Incorporating Climate Change and Extreme Weather Impacts

by Rumman Mowla Chowdhury, Cheng Zhang, Kauser Jahan and Julia Renee Thornton

Water 2026, 18(9), 1085; https://doi.org/10.3390/w18091085 - 1 May 2026

Viewed by 934

Abstract

Southern New Jersey faces increasing flood risk due to several factors including rapid development, climate change, and aging infrastructure. This study evaluated the flood vulnerability of two municipal solid waste landfills located in Gloucester and Cumberland Counties. These sites are located near rural [...] Read more.

Southern New Jersey faces increasing flood risk due to several factors including rapid development, climate change, and aging infrastructure. This study evaluated the flood vulnerability of two municipal solid waste landfills located in Gloucester and Cumberland Counties. These sites are located near rural communities that rely on shallow groundwater for drinking water, which may be contaminated by floods. To assess these challenges, this research applies a hydrologic–hydraulic model to evaluate future flood vulnerability at the Cumberland County Improvement Authority (CCIA) landfill and the Gloucester County Solid Waste Complex (GCSWC) landfill. The method uses HEC-HMS and HEC-RAS 2D model simulations with climate-adjusted precipitation data derived from global climate models. Model performance was evaluated using Hurricane Ida (31 August–2 September 2021) by comparing HEC-RAS-simulated inundation extents with independently derived Sentinel-1 SAR flood maps generated in Google Earth Engine. Climate forcing was developed by deriving climate-adjusted 24 h precipitation–frequency (PF) design depths for 50-year and 100-year design storms under the Shared Socioeconomic Pathway (SSP) emissions pathways SSP2-4.5 (moderate) and SSP5-8.5 (high) for mid-century (2025–2050) and late-century (2070–2100) periods. These PF storm totals were converted to rainfall hyetographs using a fixed alternating variability method (AVM) temporal pattern within the coupled HEC-HMS/HEC-RAS modeling chain. Hazard amplification was primarily expressed through lateral inundation expansion and longer persistence of shallow flooding in low-relief operational zones, rather than uniform increases in peak depth across landfill interiors. Across both facilities, the landfill toe and adjacent access corridors were consistently identified as the most sensitive operational areas. Full article

(This article belongs to the Special Issue Advance in Hydrology and Hydraulics of the River System Research 2025)

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23 pages, 4083 KB

Open AccessArticle

Tracing Groundwater Recharge Sources and Controls on Groundwater Quality in a Delineated Aquifer to Support Groundwater Allocation, De Aar, Northern Cape, South Africa

by Lucky Baloyi, Sikelela Mqhayi, Harrison Pienaar, Mxolisi B. Mukhawana, Mike Butler and Thokozani Kanyerere

Water 2026, 18(9), 1084; https://doi.org/10.3390/w18091084 - 1 May 2026

Viewed by 978

Abstract

Groundwater-dependent communities such as De Aar require a better understanding of groundwater systems to ensure sustainable allocation. This study aims to trace recharge sources in unconfined and confined aquifers and identify processes controlling groundwater quality using hydrogeochemistry and environmental tracers. It argues that [...] Read more.

Groundwater-dependent communities such as De Aar require a better understanding of groundwater systems to ensure sustainable allocation. This study aims to trace recharge sources in unconfined and confined aquifers and identify processes controlling groundwater quality using hydrogeochemistry and environmental tracers. It argues that aquifer delineation and hydraulic parameters alone cannot fully identify recharge sources or geochemical processes; integrating them with hydrogeochemistry and environmental tracers provides stronger evidence to support groundwater allocation. To validate the argument, the study integrated hydrogeochemical analysis, stable isotopes, tritium, radon-222, and statistical methods supported by depth-specific groundwater sampling. The results, interpreted using Piper and Gibbs diagrams, PHREEQC modelling, and scatter plots, show that groundwater evolution is mainly controlled by rock–water interaction, ion exchange, evaporation, and mixing processes. Ca–HCO₃ water indicates recent recharge, while Na–Cl water reflects evaporation effects in both unconfined and confined aquifers, with halite dissolution contributing to Na and Cl enrichment. Isotope results indicate that unconfined aquifer water is isotopically enriched and linked to recent recharge, whereas confined aquifer and spring waters are depleted, suggesting recharge from higher elevations through fractured zones. Tritium dating reveals young (<30 years), intermediate (30–50 years), and old groundwater (60–109 years), while radon results indicate active groundwater flow path, particularly along fractures. These findings demonstrate that groundwater recharge is derived from both local meteoric sources and regional contributions, resulting in predominantly fresh groundwater; however, localized quality concerns should be considered for improved water allocation. Full article

(This article belongs to the Section Hydrogeology)

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26 pages, 3479 KB

Open AccessArticle

Sustainable Magnetic Hybrid Biomaterials from Sugarcane Bagasse and Rice Husk for Enhanced Simultaneous Adsorption of Cu(II)-Pb(II) Ions and Aqueous Pollutants

by Iryanti Fatyasari Nata, Chairul Irawan, Abubakar Tuhuloula, Rinna Juwita, Meilana Dharma Putra, Yu-Lin Kuo, Sri Novi Anggraini and Norma Yunita

Water 2026, 18(9), 1083; https://doi.org/10.3390/w18091083 - 30 Apr 2026

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Abstract

Agricultural byproducts cellulose-rich (~40%) sugarcane bagasse (SCB) and rice husk (RH) wastes may be used as fiber sources in biomaterials manufacturing. The hybrid biomass fibers are two kinds of fibers that should generate a biocomposite according to the functions and physical, chemical, and [...] Read more.

Agricultural byproducts cellulose-rich (~40%) sugarcane bagasse (SCB) and rice husk (RH) wastes may be used as fiber sources in biomaterials manufacturing. The hybrid biomass fibers are two kinds of fibers that should generate a biocomposite according to the functions and physical, chemical, and mechanical properties of materials. The biocomposite was synthesized using the solvothermal method. The FeCl₃.6H₂O was dissolved in C₂H₃NaO₂ and C₆H₆O₂ and later heated at 60 °C. The SCB and RH fiber (1:1) are added with HDMA into the mixture, then placed in a Teflon stainless steel autoclave at 200 °C for 6 h. The biocomposite was employed as a green adsorbent to treat wastewater through simultaneous adsorption. The biocomposite had 2.637 mmol g⁻¹ of amine groups, which makes smaller magnetic particles and a high surface area of up to 79%. The pseudo-second-order kinetic model followed the Cu(II) and Pb(II) ions adsorption for 4 h (240 min), and the maximum adsorption capacities were 35.042 mg g⁻¹ and 67.127 mg g⁻¹, respectively, at the pH of 5. The biocomposite not only got rid of metal ions, but it also worked well to get rid of dye, total suspended solids (TSSs), and chemical oxygen demand (COD) as pollutants in wastewater. The biocomposite still worked well after being used four times. Full article

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

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Water, Volume 18, Issue 9 (May-1 2026) – 123 articles

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