Water

30 pages, 16884 KB

Open AccessArticle

Evaluating the Long-Term Effectiveness of Marsh Terracing for Conservation with Integrated Geospatial and Wetland Simulation Modeling

by Nick Carpenter, Laura Costadone and Thomas R. Allen

Water 2025, 17(18), 2769; https://doi.org/10.3390/w17182769 - 18 Sep 2025

Abstract

Coastal marshes provide essential ecosystem services, yet they are vulnerable to anthropogenic stressors and climate change, particularly sea level rise (SLR). Restoration approaches like marsh terracing have emerged as nature-based strategies to enhance resilience and reduce habitat loss. This study applies the Sea [...] Read more.

Coastal marshes provide essential ecosystem services, yet they are vulnerable to anthropogenic stressors and climate change, particularly sea level rise (SLR). Restoration approaches like marsh terracing have emerged as nature-based strategies to enhance resilience and reduce habitat loss. This study applies the Sea Level Affecting Marshes Model (SLAMM) to assess the potential of marsh terraces to mitigate future losses, while also examining the model’s limitations, including its assumptions and capacity to reflect complex marsh processes. A geospatial approach was used to generate 3D representations of terraces through morphostatic modeling within digital elevation models (DEMs). Under a no-restoration scenario, SLAMM projections show that all marshes analyzed are at risk of total loss by 2100. In contrast, scenarios including terracing demonstrate a delay in net marsh loss, extending the persistence of key marsh habitats by approximately a decade. Although marsh degradation remains likely under high SLR conditions, the results underscore the utility of marsh terraces in prolonging habitat stability. Additionally, the study demonstrates the feasibility of integrating restoration features like terraces into DEMs and wetland models. Despite SLAMM’s simplified erosion and accretion assumptions, the model yields important insights into restoration effectiveness and long-term marsh dynamics, informing more adaptive, forward-looking coastal management strategies. Full article

(This article belongs to the Special Issue New Insights into Sea Level Dynamics and Coastal Erosion)

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19 pages, 1545 KB

Open AccessArticle

Study on an Evaluation Model for Regional Water Resource Stress Based on Water Scarcity Footprint

by Lu Qiao, Xue Bai, Yan Bai, Jialin Liu, Lingsi Kong and Lan Zhang

Water 2025, 17(18), 2768; https://doi.org/10.3390/w17182768 - 18 Sep 2025

Abstract

Under the multiple pressures of intensifying global climate change disruption and rapid economic growth, China has become one of the countries facing the most serious water scarcity problems. Based on the ISO 14046 standard and the framework of water scarcity footprint theory, this [...] Read more.

Under the multiple pressures of intensifying global climate change disruption and rapid economic growth, China has become one of the countries facing the most serious water scarcity problems. Based on the ISO 14046 standard and the framework of water scarcity footprint theory, this study will break through the static limitations and lack of dimensions of traditional characteristic factors (i.e., water stress) and construct a water stress evaluation index system that combines nature, economy, and society. The results indicate that in recent years, regional water stress in China has exhibited significant spatiotemporal variations and spatial clustering, primarily driven by composite factors, with an overall decreasing trend. Among them, Shanghai is the highest-pressure area and Shaanxi is the lowest-pressure area, which is mainly due to the spatial projection of the coupling effect of multi-dimensional factors. In addition, the obstacle degree analysis method shows that indicators such as the utilization rate of water resource development constitute cross-regional constraints. To this end, all regions should make efforts to regulate and control the water use structure, introduce water-saving technologies, and strengthen water-saving publicity according to their needs. Therefore, this study not only provides a scientific basis for in-depth understanding of the distribution law and influencing mechanism of water stress but also provides an important reference for the rational allocation and sustainable use of water resources by upgrading the characteristic factors to system control signals. Full article

(This article belongs to the Section Water Use and Scarcity)

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16 pages, 671 KB

Open AccessArticle

Prevalence and Resistance Patterns of Campylobacter spp. and Arcobacter spp. in Portuguese Water Bodies

by Igor Venâncio, Inês Martins, Rodrigo M. Martins, Mónica Oleastro and Susana Ferreira

Water 2025, 17(18), 2767; https://doi.org/10.3390/w17182767 - 18 Sep 2025

Abstract

Campylobacter spp. and Arcobacter spp. are recognized etiological agents of gastroenteritis worldwide. While poultry is their best-known reservoir, human exposure can also occur via environmental pathways, particularly through contaminated water sources, which play a significant role in their transmission dynamics. In addition to [...] Read more.

Campylobacter spp. and Arcobacter spp. are recognized etiological agents of gastroenteritis worldwide. While poultry is their best-known reservoir, human exposure can also occur via environmental pathways, particularly through contaminated water sources, which play a significant role in their transmission dynamics. In addition to their pathogenicity and widespread environmental prevalence, increasing antibiotic resistance has contributed to the global emergence of multidrug-resistant strains, hindering effective treatment. Here, the distribution and antibiotic resistance potential of Campylobacter spp. and Arcobacter spp. isolates collected from water bodies in Portugal were investigated. Water samples were collected from rivers, their tributaries, and springs, at 25 sites over a six-month period. Campylobacter spp. were isolated from 13.3% of the samples, whereas Arcobacter spp. were detected in 57.6% of the samples. Of the 27 isolated Campylobacter isolates, 44.0% were resistant to at least one antibiotic, while only one strain exhibited a multidrug-resistant (MDR) phenotype. In contrast, 98.9% of the 177 Arcobacter isolates were resistant to at least one antibiotic, with 15.8% classified as MDR. These findings contribute to the surveillance of Campylobacter spp. and Arcobacter spp., highlighting the critical role of aquatic environments in their epidemiology and supporting the need to incorporate waterborne transmission pathways into integrated surveillance and control strategies within the One Health framework. Full article

(This article belongs to the Special Issue Evaluation of Microbiological Indicators for Water and Wastewater Treatment and Reuse)

21 pages, 4834 KB

Open AccessArticle

A Displacement Monitoring Model for High-Arch Dams Based on SHAP-Driven Ensemble Learning Optimized by the Gray Wolf Algorithm

by Shasha Li, Kai Jiang, Shunqun Yang, Zuxiu Lan, Yining Qi and Huaizhi Su

Water 2025, 17(18), 2766; https://doi.org/10.3390/w17182766 - 18 Sep 2025

Abstract

Displacement monitoring data is essential for assessing the structural safety of high-arch dams. Existing models, predominantly based on single-model architectures, often lack the ability to effectively integrate multiple algorithms, leading to limited predictive performance and poor interpretability. This study proposes an ensemble learning [...] Read more.

Displacement monitoring data is essential for assessing the structural safety of high-arch dams. Existing models, predominantly based on single-model architectures, often lack the ability to effectively integrate multiple algorithms, leading to limited predictive performance and poor interpretability. This study proposes an ensemble learning framework for dam displacement prediction, combining Hydraulic–Seasonal–Temporal model (HST), Random Forest (RF), and Bidirectional Gated Recurrent Unit (BiGRU) models as base learners. A stacking strategy is employed to enhance predictive accuracy, and the Grey Wolf Optimizer (GWO) is used for hyperparameter optimization. To improve model transparency, the Shapley Additive Explanations (SHAP) algorithm is applied for interpretability analysis. Extensive experiments demonstrate that the proposed ensemble model outperforms individual models, achieving a Root Mean Squared Error (RMSE) of 0.2241 and a Coefficient of Determination (R²) of 0.9993 on the test set. The SHAP analysis further elucidates the contribution of key variables, providing valuable insights into the displacement prediction process and offering a robust technical foundation for arch dam safety monitoring and early risk warning. Full article

(This article belongs to the Special Issue Hydraulic Engineering Applications of Artificial Intelligence, Deep Learning, and Digital Twin Technology)

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26 pages, 4713 KB

Open AccessArticle

Impacts of the Degree of Heterogeneity on Design Flood Estimates: Region of Influence vs. Fixed Region Approaches

by Ali Ahmed, Mohammad A. Morshed, Sadia T. Mim, Ridwan S. M. H. Rafi, Zaved Khan, Rajib Maity and Ataur Rahman

Water 2025, 17(18), 2765; https://doi.org/10.3390/w17182765 - 18 Sep 2025

Abstract

In regional flood frequency analysis (RFFA), the formation of homogeneous regions is commonly regarded as a necessary condition for reliable regional flood estimation. However, achieving true homogeneity is often challenging in practice. This study investigates the formation of homogeneous regions by applying two [...] Read more.

In regional flood frequency analysis (RFFA), the formation of homogeneous regions is commonly regarded as a necessary condition for reliable regional flood estimation. However, achieving true homogeneity is often challenging in practice. This study investigates the formation of homogeneous regions by applying two region delineation approaches—fixed regions and the region-of-influence (ROI) method—accompanied by the widely used heterogeneity measure (H₁) proposed by Hosking and Wallis. The analysis utilizes data from 201 stream gauging stations across southeast Australia, evaluating a total of 1211 candidate regions. The computed H₁-statistics range from 13 to 30 for fixed regions and from 6 to 30 for ROI-based regions, indicating a consistently high level of heterogeneity across the study area. This suggests that the assumption of homogeneity may not be realistic for many parts of southeast Australia. Moreover, regression equations developed for regional flood estimation yield absolute median relative errors between 29% and 56%, with a median of 39% across return periods from 2 to 100 years. These findings underscore the limitations of relying solely on homogeneity in regional flood modelling and highlight the need for more flexible and robust approaches in RFFA. The outcomes of this research have significant implications for improving flood estimation practices and are expected to contribute to future enhancements of the Australian Rainfall and Runoff (ARR) national guidelines. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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18 pages, 2624 KB

Open AccessArticle

Comparative Assessment of Different Electrode Combinations for Phosphate Removal from Onsite Wastewater via Electrocoagulation

by Arif Reza, Xiumei Jian, Fanjian Zeng and Xinwei Mao

Water 2025, 17(18), 2764; https://doi.org/10.3390/w17182764 - 18 Sep 2025

Abstract

Phosphorus (P) discharge from onsite wastewater treatment systems (OWTSs) poses a significant threat to water quality, contributing to eutrophication in nutrient-sensitive aquatic environments. In treated effluents, P predominantly exists as orthophosphate (PO₄³⁻), a highly bioavailable and reactive form that requires [...] Read more.

Phosphorus (P) discharge from onsite wastewater treatment systems (OWTSs) poses a significant threat to water quality, contributing to eutrophication in nutrient-sensitive aquatic environments. In treated effluents, P predominantly exists as orthophosphate (PO₄³⁻), a highly bioavailable and reactive form that requires targeted removal. This study evaluates the performance of electrocoagulation (EC) as a polishing step for PO₄³⁻ removal from OWTS effluents using 12 anode/cathode combinations comprising aluminum (Al), iron (Fe), magnesium (Mg), and stainless steel (SS). Key operational parameters, including treatment time, mixing speed, current density, pH, and initial PO₄³⁻ concentration, were systematically investigated when synthetic denitrified effluent (20 mg P/L) was treated. Based on the performance, the four most effective electrode combinations (Al/Al, Al/Mg, Fe/Al, and Mg/Mg), along with a commercial benchmark (Fe/Fe), were further tested under extended hydraulic retention times (up to 48 h) in both synthetic and real (denitrified) wastewater. To date, none of the studies have systematically evaluated all possible anode/cathode combinations involving multiple electrode materials under uniform operational conditions. The Al/Al and Mg/Mg EC systems achieved rapid and high PO₄³⁻ removal efficiencies (>95%), while Mg-based systems demonstrated sustained performance over prolonged treatment durations, especially in real wastewater. Bimetallic pairs such as Al/Mg and Fe/Al exhibited synergistic effects through enhanced coagulant generation and pH stabilization. The results indicated that PO₄³⁻ removal efficiency was strongly influenced by electrode material selection, hydrodynamic conditions, and wastewater compositions, underscoring the need to design EC systems based on site-specific water quality conditions in OWTSs. Full article

(This article belongs to the Special Issue Application of Electrochemical Technologies in Wastewater Treatment)

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22 pages, 6378 KB

Open AccessArticle

LU-Net: Lightweight U-Shaped Network for Water Body Extraction of Remote Sensing Images

by Chengzhi Deng, Ruqiang He, Zhaoming Wu, Xiaowei Sun and Shengqian Wang

Water 2025, 17(18), 2763; https://doi.org/10.3390/w17182763 - 18 Sep 2025

Abstract

Deep learning-based water body extraction methods generally focus on maximizing accuracy while neglecting inference speed, which can make them challenging to apply in real-time applications. To address this problem, this paper proposes a lightweight u-shaped network (LU-Net), which improves inference speed while maintaining [...] Read more.

Deep learning-based water body extraction methods generally focus on maximizing accuracy while neglecting inference speed, which can make them challenging to apply in real-time applications. To address this problem, this paper proposes a lightweight u-shaped network (LU-Net), which improves inference speed while maintaining comparable accuracy. To reduce inference latency, a lightweight decoder block (LDB) is designed, which employs a depthwise separable convolution structure to accelerate the decoding process. To enhance accuracy, a lightweight convolutional block attention module (LCBAM) is designed, which effectively captures water-specific spectral and spatial characteristics through a dual-attention mechanism. To improve multi-scale water boundary extraction, a structurally re-parameterized multi-scale fusion prediction module (SRMFPM) is designed, which integrates multi-scale water boundary information through convolutions of different sizes. Comparative experiments are conducted on the GID and LoveDA datasets, with model performance assessed using the MIoU metric and inference latency. The results demonstrate that LU-Net achieves the lowest GPU latency of 3.1 MS and the second-lowest CPU latency of 36 MS in the experiments. On the GID, LU-Net achieves the MIoU of 91.36%, outperforming other tested methods. On the LoveDA datasets, LU-Net achieves the second-highest MIoU of 86.32% among the evaluated models, which is 0.08% lower than the top-performing CGNet. Considering both latency and MIoU, LU-Net demonstrates commendable efficiency on the GID and LoveDA datasets across all compared networks. Full article

(This article belongs to the Section New Sensors, New Technologies and Machine Learning in Water Sciences)

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28 pages, 11202 KB

Open AccessArticle

Enhancing Streamflow Modeling in Data-Scarce Catchments with Similarity-Guided Source Selection and Transfer Learning

by Yuxuan Gao, Rupal Mandania, Jun Ma, Jack Chen and Wuyi Zhuang

Water 2025, 17(18), 2762; https://doi.org/10.3390/w17182762 (registering DOI) - 18 Sep 2025

Abstract

Accurate streamflow modeling in data-scarce catchments remains a significant challenge due to the limited availability of historical records. Transfer Learning (TL), increasingly applied in hydrology, leverages knowledge from data-rich catchments (sources) to enhance predictions in data-scarce catchments (targets), providing new possibilities of hydrological [...] Read more.

Accurate streamflow modeling in data-scarce catchments remains a significant challenge due to the limited availability of historical records. Transfer Learning (TL), increasingly applied in hydrology, leverages knowledge from data-rich catchments (sources) to enhance predictions in data-scarce catchments (targets), providing new possibilities of hydrological predictions. Most existing TL approaches pre-train models on large-scale meteoro-hydrological datasets and show good generalizability across multiple target catchments. However, for a specific target catchment, it remains unclear which source catchments contribute most effectively to the accurate prediction. Including many irrelevant sources may even degrade model performance. In this study, we investigated how source catchment selection affects TL performance by employing similarity-guided strategies based on three key factors, i.e., spatial distance, physical attributes, and flow regime characteristics. Using the CAMELS-GB dataset, we conducted comparative experiments by pre-training the networks with different ranked groups of the source catchments and fine-tuning them on three target catchments representing distinct hydrological environments. The results showed that carefully selected small subsets (fewer than 40, or even as few as 10) of highly similar catchments can achieve comparable or better TL performance than using all 668 available source catchments. All three target catchments yielded better NSE results from source catchments with closer spatial proximity and more consistent flow regimes. The TL performance of physical attribute similarity-based selection varied depending on the attribute combinations, with those related to land cover, climate, and soil properties leading to superior performance. These findings highlight the importance of similarity-guided source selection in hydrological TL. In addition, they demonstrate ways to reduce computational costs while improving modeling accuracy in data-scarce regions. Full article

(This article belongs to the Special Issue Computer Modelling Techniques in Environmental Hydraulics and Water Resource Engineering)

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20 pages, 2066 KB

Open AccessArticle

Oxidic Substrate with Variable Charge Surface Chemically Modified for Copper Ion Adsorption from Aqueous Solutions

by José G. Prato, Fernando Millán, Iván Ríos, Marin Senila, Erika Andrea Levei, Luisa Carolina González and Enju Wang

Water 2025, 17(18), 2761; https://doi.org/10.3390/w17182761 - 18 Sep 2025

Abstract

The presence of toxic elements in drinking water poses important risks to human health. Among the diverse methodologies available to remove these elements from water, adsorption methods are among the most effective; however, many adsorbent materials are either costly, not widely available, or [...] Read more.

The presence of toxic elements in drinking water poses important risks to human health. Among the diverse methodologies available to remove these elements from water, adsorption methods are among the most effective; however, many adsorbent materials are either costly, not widely available, or difficult to handle. This work focuses on the application of a new natural geologic material, named “V” material, to prepare an adsorbent substrate applied to water treatment, using its adsorption properties to remove metallic species from aqueous media. The geologic material is a thermally and mechanically resistant material, composed basically of quartz, iron and aluminum oxides, with amphoteric properties. A granular medium or substrate was prepared via thermal treatment using three granulometric fractions of the material: the smaller fraction, less than 250 μm, named the fine fraction, VFF; from 250 μm to 425 μm, named the medium fraction, VMF; and from 425 μm to 1200 μm, named the gross fraction, VGF. The experiments were carried out on both alkaline-treated and non-treated substrates, named activated and non-activated substrates, respectively. The BET and external surface, as well as the pore volume, increased significantly after the calcination process. The adsorption isotherms pointed to a strong interaction between metallic ions and activated substrates, in contrast to the non-activated substrate, which showed much less affinity. This type of isotherm is associated with specific adsorption, where the adsorption occurs chemically between Cu²⁺ ions and the substrate surface, basically composed of amphoteric metallic oxides. The adsorption data fit fairly well to the Freundlich and Langmuir models, where the K values are higher for activated substrates. According to the Freundlich K values, the copper adsorptions on the activated substrates were higher: 5.0395, 3.9814 and 4.2165 mg/g, compared with 0.3622, 1.8843 and 0.4544 mg/g on non-activated substrates. The pH measurements showed the production of 0.56 and 0.10 μmol H⁺ during the adsorption reaction on the activated substrate, following the theoretical model for the chemisorption of transitional metals on amphoteric oxides. These results show the potential applicability of this kind of substrate in retaining transitional metals from polluted drinkable water at low cost. It is environmentally friendly, non-toxic, and available for rural media and mining-impacted regions. Full article

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

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20 pages, 5217 KB

Open AccessArticle

A²DSC-Net: A Network Based on Multi-Branch Dilated and Dynamic Snake Convolutions for Water Body Extraction

by Shuai Zhang, Chao Zhang, Qichao Zhao, Junjie Ma and Pengpeng Zhang

Water 2025, 17(18), 2760; https://doi.org/10.3390/w17182760 - 18 Sep 2025

Abstract

The accurate and efficient acquisition of the spatiotemporal distribution of surface water is of vital importance for water resource utilization, flood monitoring, and environmental protection. However, deep learning models often suffer from two major limitations when applied to high-resolution remote sensing imagery: the [...] Read more.

The accurate and efficient acquisition of the spatiotemporal distribution of surface water is of vital importance for water resource utilization, flood monitoring, and environmental protection. However, deep learning models often suffer from two major limitations when applied to high-resolution remote sensing imagery: the loss of small water body features due to encoder scale differences, and reduced boundary accuracy for narrow water bodies in complex backgrounds. To address these challenges, we introduce the A²DSC-Net, which offers two key innovations. First, a multi-branch dilated convolution (MBDC) module is designed to capture contextual information across multiple spatial scales, thereby enhancing the recognition of small water bodies. Second, a Dynamic Snake Convolution module is introduced to adaptively extract local features and integrate global spatial cues, significantly improving the delineation accuracy of narrow water bodies under complex background conditions. Ablation and comparative experiments were conducted under identical settings using the LandCover.ai and Gaofen Image Dataset (GID). The results show that A²DSC-Net achieves an average precision of 96.34%, average recall of 96.19%, average IoU of 92.8%, and average F1-score of 96.26%, outperforming classical segmentation models such as U-Net, DeepLabv3+, DANet, and PSPNet. These findings demonstrate that A²DSC-Net provides an effective and reliable solution for water body extraction from high-resolution remote sensing imagery. Full article

(This article belongs to the Section New Sensors, New Technologies and Machine Learning in Water Sciences)

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10 pages, 1275 KB

Open AccessArticle

Quantify Mercury Sulfide in Sediments for Bioavailability Assessment

by Yuch-Ping Hsieh and Glynnis Bugna

Water 2025, 17(18), 2759; https://doi.org/10.3390/w17182759 - 18 Sep 2025

Abstract

While studies have shown that heavy metal sulfides in sediments are not bioavailable, most of them are acid-extractable (AE) and inseparable from non-sulfides in sediments. Exceptions were found recently that mercury and copper sulfides precipitated in sediments are non-AE because they are exclusively [...] Read more.

While studies have shown that heavy metal sulfides in sediments are not bioavailable, most of them are acid-extractable (AE) and inseparable from non-sulfides in sediments. Exceptions were found recently that mercury and copper sulfides precipitated in sediments are non-AE because they are exclusively bi-sulfides. Therefore, quantifying mercury sulfide in sediments is possible for bioavailability assessment. To illustrate the application of this new approach for mercury bioavailability assessment, we quantified the distribution of mercury sulfide in sediments of the Apalachicola Bay, North Florida, USA. We extracted sediment cores and determined the total mercury, non-sulfide mercury, and sulfide mercury as well as the total sulfides, bulk density, and organic matter. The results showed that the mercury in the top 45 cm sediments were, on average, 13.3 ± 5.4 ng/cm³, of which 97.1 ± 2.5% were sulfide. The potentially bioavailable (non-sulfide) mercury was on average only 0.28 ± 0.22 ng/cm³ (2.9% of the total mercury). The total mercury and sulfide mercury were significantly correlated with the organic matter, which were dictated by the discharge pattern of the river input. This study demonstrates that aquatic sediments accumulate terrestrial mercury, and sulfidic sediments sequester most of it as sulfide. This new approach for mercury bioavailability assessment is simple yet chemically rigorous. Full article

(This article belongs to the Special Issue Geochemistry and Removal of Heavy Metals and Other Pollutants in Water)

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20 pages, 9228 KB

Open AccessArticle

Comparative Analysis of Household Agricultural Practices and Groundwater Quality in Two Transylvanian Communes: Ceanu Mare (Cluj County) and Chețani (Mureș County), Romania

by Nicolae-Leontin Petruţa, Ioana Petruţa, Ioana Monica Sur, Ramona Bianca Şonher, Timea Gabor, Tudor Andrei Rusu and Tiberiu Rusu

Water 2025, 17(18), 2758; https://doi.org/10.3390/w17182758 - 18 Sep 2025

Abstract

This study provides a comparative analysis of agricultural practices, water resource management, and environmental risks in two rural communes of Transylvania, Romania—Ceanu Mare (Cluj County) and Chețani (Mureș County). Data were collected in June 2025 through structured questionnaires administered to 430 households in [...] Read more.

This study provides a comparative analysis of agricultural practices, water resource management, and environmental risks in two rural communes of Transylvania, Romania—Ceanu Mare (Cluj County) and Chețani (Mureș County). Data were collected in June 2025 through structured questionnaires administered to 430 households in Ceanu Mare and 184 households in Chețani, representing over 30% and 20% of the total households, respectively. The research examines the structure of agricultural activity, use of fertilizers and pesticides, irrigation methods, and the local perception of pollution and subsidy programs. Both communes exhibit small-scale, household-based agriculture, but notable differences exist: Ceanu Mare demonstrates higher use of chemical inputs and environmental awareness, while Chețani relies more on organic fertilizers and private wells for irrigation. In addition to survey-based data, the study incorporates direct chemical analysis of household well water, assessing concentrations of nitrate (NO₃⁻), nitrite (NO₂⁻), ammonium (NH₄⁺), and pH levels as indicators of groundwater quality and public health risk. The results reveal that NO₃⁻ remained below the 50 mg/L standard in all wells, while NO₂⁻ approached or slightly exceeded 0.50 mg/L in a few Ceanu Mare villages, underscoring the vulnerability of shallow wells to diffuse agricultural inputs and sanitation deficits. The study also characterizes the main agrochemical compounds used and discusses their potential impacts on water and soil quality, emphasizing nitrate leaching, phosphate runoff, and the persistence of pesticide residues as major risks. These findings underscore the necessity of integrated management strategies, regular monitoring of groundwater quality, and targeted policy interventions to ensure sustainable rural development and environmental protection in similar Central and Eastern European contexts. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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18 pages, 2852 KB

Open AccessArticle

Manganese(II) Enhanced Ferrate(VI) Pretreatment: Effects on Membrane Fouling and Pollutants Interception

by Chengbiao Xu, Lu Wang, Jun Ma and Yulei Liu

Water 2025, 17(18), 2757; https://doi.org/10.3390/w17182757 - 18 Sep 2025

Abstract

To mitigate membrane fouling in the ultrafiltration process of surface water, this study focused on the source water from the Songhua River, systematically investigating the efficacy and mechanism of combined ferrate(VI) (Fe(VI)) and manganese(II) (Mn(II)) pretreatment in controlling ultrafiltration membrane fouling. Emphasis was [...] Read more.

To mitigate membrane fouling in the ultrafiltration process of surface water, this study focused on the source water from the Songhua River, systematically investigating the efficacy and mechanism of combined ferrate(VI) (Fe(VI)) and manganese(II) (Mn(II)) pretreatment in controlling ultrafiltration membrane fouling. Emphasis was placed on analyzing the impacts of pretreatment on membrane fouling performance, physicochemical properties of influent and effluent, membrane surface characteristics, and interfacial interactions. The results showed that the combined pretreatment with Fe(VI) and Mn(II) outperformed individual pretreatments and the untreated group significantly. When Fe(VI)/Mn(II) was 2/3, the normalized flux reached 0.66, a 35% increase compared to the untreated group; meanwhile, the pollutants retention was enhanced to 41.5%, with reversible and irreversible fouling resistances reduced by 75% and 77%, respectively. At this optimal ratio, the reaction products of Fe(VI) and Mn(II) coagulation acted as the core mechanism. It enhances pollutant particle repulsion, reduces particle size to form a loose structure, leading to a porous, hydrophilic membrane surface fouling layer with low roughness, thus minimizing membrane pore blockage. The combined pretreatment maintained a repulsive total interaction energy between pollutants and the membrane throughout the process, significantly reducing irreversible adsorption, which further verified the effectiveness of fouling mitigation. This study demonstrated that combined Fe(VI)/Mn(II) pretreatment at a molar ratio of 2:3 could efficiently control ultrafiltration membrane fouling by regulating pollutant characteristics and interfacial interactions, providing a theoretical basis and technical support for advanced treatment of surface water. Full article

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

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28 pages, 3006 KB

Open AccessArticle

Surface Water–Groundwater Interactions in a Sahelian Catchment: Exploring Hydrochemistry and Isotopes and Implications for Water Quality Management

by Issoufou Ouedraogo, Marnik Vanclooster, Frederic Huneau, Yuliya Vystavna, Seifu Kebede and Youssouf Koussoubé

Water 2025, 17(18), 2756; https://doi.org/10.3390/w17182756 - 17 Sep 2025

Abstract

The Sahel Transboundary Taoudéni Basin, covering about 20% of Burkina Faso, hosts vital aquifers critical for water security and development. Effective groundwater monitoring is essential for sustainable resource management. In the Kou sub-basin, groundwater quality assessment is increasingly important. This study integrates hydrochemistry, [...] Read more.

The Sahel Transboundary Taoudéni Basin, covering about 20% of Burkina Faso, hosts vital aquifers critical for water security and development. Effective groundwater monitoring is essential for sustainable resource management. In the Kou sub-basin, groundwater quality assessment is increasingly important. This study integrates hydrochemistry, water stable isotopes (δ¹⁸O, δ²H), GIS, and multivariate statistics to understand subsurface geochemical processes. A total of 48 samples—43 groundwater and 5 surface water—were analyzed for 19 hydrochemical parameters and isotopes. In surface water, δ¹⁸O ranged from −5.96‰ to −5.09‰, and δ²H from −37.65‰ to −29.15‰. In groundwater, δ¹⁸O ranged from −5.93‰ to −4.39‰, and δ²H from −34.62‰ to −25.05‰. The spatial distribution of δ¹⁸O and δ²H was mapped using inverse distance weighted (IDW) interpolation in ArcGIS 10.8. A δ²H vs. δ¹⁸O plot showed groundwater values clustered near the Global Meteoric Water Line, indicating minimal evaporation during recharge. Groundwater chemistry was dominated by Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > NO₃⁻ > Cl⁻ > SO₄²⁻. Key hydrogeochemical processes include water–rock interaction (leaching, weathering, ion exchange) and anthropogenic pollution. Isotopic signatures reveal heterogeneous recharge sources and aquifer connectivity. These findings enhance the understanding of water sources and geochemical processes in the Kou basin, supporting informed groundwater resource management. Full article

(This article belongs to the Special Issue Soil and Groundwater Quality and Resources Assessment, 2nd Edition)

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30 pages, 8476 KB

Open AccessArticle

A Pragmatic Multi-Source Remote Sensing Framework for Calcite Whitings and Post-Wildfire Effects in the Gadouras Reservoir

by John S. Lioumbas, Aikaterini Christodoulou, Alexandros Mentes, Georgios Germanidis and Nikolaos Lymperopoulos

Water 2025, 17(18), 2755; https://doi.org/10.3390/w17182755 (registering DOI) - 17 Sep 2025

Abstract

The Gadouras Reservoir, Rhodes Island’s primary water source, experiences recurrent whiting events—milky turbidity from calcium carbonate precipitation—that challenge treatment operations, with impacts compounded by a major 2023 wildfire in this fire-prone Mediterranean setting. To elucidate these dynamics, a pragmatic, multi-source monitoring framework integrates [...] Read more.

The Gadouras Reservoir, Rhodes Island’s primary water source, experiences recurrent whiting events—milky turbidity from calcium carbonate precipitation—that challenge treatment operations, with impacts compounded by a major 2023 wildfire in this fire-prone Mediterranean setting. To elucidate these dynamics, a pragmatic, multi-source monitoring framework integrates archived Sentinel-2 and Landsat imagery with treatment-plant records (2017–mid-2025). Unitless spectral indices (e.g., AreaBGR) for whiting detection and chlorophyll-a proxies are combined with laboratory measurements of turbidity, pH, total organic carbon, manganese, and hydrological metrics, analyzed via spatiotemporal Hovmöller diagrams, Pearson correlations, and interrupted time-series models. Two seasonal whiting regimes are identified: a biogenic summer mode (southern origin; elevated chlorophyll-a; water temperature > 15 °C; pH > 8.5) and a non-biogenic winter mode (northern inflows). Following the wildfire, the system exhibits characteristics that could be related to possible hypolimnetic anoxia, prolonged whiting, a ~50% rise in organic carbon, and a manganese excursion to ~0.4 mg L⁻¹ at the deeper intake. Crucially, the post-fire period shows a decoupling of AreaBGR from turbidity (r ≈ 0.233 versus ≈ 0.859 pre-fire)—a key diagnostic finding that confirms a fundamental shift in the composition and optical properties of suspended particulates. The manganese spike is best explained by the confluence of a wildfire-induced biogeochemical predisposition (anoxia and Mn mobilization) and a consequential operational decision (relocation to a deeper, Mn-rich intake). This framework establishes diagnostic baselines and thresholds for managing fire-impacted reservoirs, supports the use of remote sensing in data-scarce systems, and informs adaptive operations under increasing climate pressures. Full article

(This article belongs to the Special Issue Remote Sensing of Spatial-Temporal Variation in Surface Water)

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22 pages, 3981 KB

Open AccessArticle

Combined Efficacy of Silver, Copper, and Hypochlorite Ions for Vector Control of Juvenile Aedes aegypti in Household Water Storage Containers

by Sydney S. Turner, James A. Smith, Karin Brett, Patrick I. Hancock, Sophie L. Howle, Victoria Cecchetti, Lorin M. Bruno, Julia Davis and Clay Ford

Water 2025, 17(18), 2754; https://doi.org/10.3390/w17182754 - 17 Sep 2025

Abstract

This study evaluates the larvicidal effects of three common water disinfectants, silver (AgNO₃), copper (CuSO₄·5H₂O), and hypochlorite (NaOCl) ions. The treatments were combined at 40–50% of their recommended drinking water guidelines and tested against late first instar [...] Read more.

This study evaluates the larvicidal effects of three common water disinfectants, silver (AgNO₃), copper (CuSO₄·5H₂O), and hypochlorite (NaOCl) ions. The treatments were combined at 40–50% of their recommended drinking water guidelines and tested against late first instar and third instar Ae. aegypti larvae. The findings demonstrate that the combined application of water disinfectants yields greater efficacy in suppressing the emergence of Aedes aegypti compared to the use of the individual disinfectants alone. The silver (Ag) and copper (Cu) combination treatment (40 ppb Ag + 600 ppb Cu) showed the greatest efficacy, achieving nearly complete inhibition of emergence of the older instar larvae (98.52% [96.50, 99.47]). All treatments demonstrated high efficacy against late 1st instar Ae. aegypti larvae, with the combined copper and chlorine (Cl) treatment yielding the lowest survival rates, though individual disinfectants also produced substantial mortality. The results of this study provide critical insights to inform the design and implementation of point-of-use water treatment technologies for household water storage containers that both ensure safe drinking water and also strategically target mosquito breeding within household storage containers, thus supporting integrated vector management approaches essential for controlling neglected tropical diseases. Full article

(This article belongs to the Topic Sustainable Water Purification Technologies for Multiple Applications)

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19 pages, 2931 KB

Open AccessArticle

Integrating Microbial Source Tracking to Unravel Impacts of Wastewater Discharge on Spatial Distribution of Riverine Microbial Community

by Yanru Fan, Hongbin Gao, Zhongfeng Jiang, Yuran Lv, Xiang Guo, Xinfeng Zhu, Junfeng Wu, Yizhe Li, Wenxiang Yu, Qi Li and Keyu Yuan

Water 2025, 17(18), 2753; https://doi.org/10.3390/w17182753 - 17 Sep 2025

Abstract

Microbial communities play a pivotal role in material cycling, energy flow, and pollutant degradation within river ecosystems. Thus, gaining a clear understanding of how wastewater discharge affects microbial community structure and function is essential for the protection and management of the surface water [...] Read more.

Microbial communities play a pivotal role in material cycling, energy flow, and pollutant degradation within river ecosystems. Thus, gaining a clear understanding of how wastewater discharge affects microbial community structure and function is essential for the protection and management of the surface water environment. In this study, a total of 9 samples were collected from the Sha River in March 2024. Subsequently, 16S rRNA sequencing technology combined with investigation of physicochemical properties of water was used to investigate the compositional diversity, spatial distribution, and explore the environmental effects of wastewater discharged on microorganisms. The sequencing results of species at the phylum level revealed that the dominant microbial phyla in the Sha River were primarily Proteobacteria (55.4%), Actinobacteriota (24.0%), Bacteroidota (14.3%), and Verrucomicrobiota (2.6%). The most dominant phylum, Proteobacteria, exhibited varying abundances across different sampling sites in the Sha River basin, with the highest abundances observed at Sites S2, S4, S5, and S6. This is mainly due to the fact that the upstream areas of Sites S2, S4, S5, and S6 are characterized by high concentrations of COD and NH₃-N, which are caused by wastewater discharge. Quantitative analysis was also conducted using the Source Tracker model; the results showed that S2 (36.7%) and S4 (31.3%) in the upper reaches of the Sha River are the primary contributors to the microbial community in the downstream catchment area (S6). The study found that the impact of wastewater discharge on the microbial community in the downstream water body exhibits a “longitudinal persistence of microbial signatures” even though the physicochemical pollution indicators of the water body have decreased. These findings of this study represent the application in microbial source tracking in the upstream and downstream sections of rivers, providing strong support for formulating more effective environmental protection strategies in the Sha River basin. Full article

(This article belongs to the Special Issue Freshwater Ecosystems—Biodiversity and Protection: 2nd Edition)

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24 pages, 11507 KB

Open AccessReview

A Review on Ecological and Environmental Impacts of Pumped Hydro Storage Based on CiteSpace Analysis

by Hailong Yin, Xuhong Zhao, Meixuan Chen, Zeding Fu, Yingchun Fang, Hui Wang, Meifang Li, Jiahao Luo, Peiyang Tan and Xiaohua Fu

Water 2025, 17(18), 2752; https://doi.org/10.3390/w17182752 - 17 Sep 2025

Abstract

This study conducted a systematic review of 222 research articles (2014–2024) from the Web of Science Core Collection database to investigate the ecological and environmental impacts of pumped hydro storage (PHS). Utilizing CiteSpace 6.1R software for visual analysis, the research hotspots and evolutionary [...] Read more.

This study conducted a systematic review of 222 research articles (2014–2024) from the Web of Science Core Collection database to investigate the ecological and environmental impacts of pumped hydro storage (PHS). Utilizing CiteSpace 6.1R software for visual analysis, the research hotspots and evolutionary trends over the past decade were comprehensively examined. Key findings include the following: (1) Annual publication output exhibited sustained growth, with China contributing 29.7% of total publications, ranking first globally. (2) Research institutions demonstrated broad geographical distribution but weak collaborative networks, as the top 10 institutions accounted for only 21.6% of total publications, highlighting untapped potential for cross-regional cooperation. (3) Current research focuses on three domains: ecological–environmental benefit assessment, renewable energy synergistic integration, and power grid regulation optimization. Emerging trends emphasize multi-objective planning (e.g., economic–ecological trade-offs) and hybrid system design (e.g., solar–wind–PHS coordinated dispatch), providing critical support for green energy transitions. (4) Post-2020 research has witnessed novel thematic directions, including deepened studies on wind–PHS coupling and life-cycle assessment (LCA). Policy-driven renewable energy integration research entered an explosive growth phase, with PHS–photovoltaic–wind complementary technologies emerging as a core innovation pathway. Future research should prioritize strengthening institutional collaboration networks, exploring region-specific ecological impact mechanisms, and advancing policy–technology–environment multi-dimensional frameworks for practical applications. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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18 pages, 2468 KB

Open AccessArticle

Enhanced Nitrogen Removal from Aquaculture Wastewater Using Biochar-Amended Bioretention Systems

by Wenqiang Jiang, Xueming Yang, Chengcai Zhang, Qian Qian, Zhen Liang, Junneng Liang, Luting Wen, Linyuan Jiang and Shumin Wang

Water 2025, 17(18), 2751; https://doi.org/10.3390/w17182751 - 17 Sep 2025

Abstract

Aquaculture wastewater is characterized by large discharge volumes and variable nitrogen concentrations, posing challenges for stable and efficient treatment. This study investigated biochar-amended bioretention systems (BBSs) under varying temperatures (8.0–26.0 °C), influent TN levels, and operation modes (intermittent and continuous flow). In intermittent [...] Read more.

Aquaculture wastewater is characterized by large discharge volumes and variable nitrogen concentrations, posing challenges for stable and efficient treatment. This study investigated biochar-amended bioretention systems (BBSs) under varying temperatures (8.0–26.0 °C), influent TN levels, and operation modes (intermittent and continuous flow). In intermittent runs, the 20% biochar system (BBS20) achieved 72.4% TN removal at low influent TN (9.55 mg/L) and 80.4% at high TN (29.96 mg/L), significantly outperforming the control (CBS). In continuous runs, BBS20 reduced effluent TN to 1.75 mg/L within 72 h, yielding higher average HRT, HLR, and ELR than CBS. Mechanistic analyses showed that biochar addition enhanced extracellular polymeric substance (EPS) secretion, stimulated electron transport system activity (ETSA), and increased the relative abundance of denitrifying genera and functional genes (e.g., nirS, narG). These synergistic effects optimized nitrification–denitrification coupling, particularly under low-temperature conditions. The findings demonstrate that biochar amendment is a practical and effective strategy for improving nitrogen removal from aquaculture wastewater. Full article

(This article belongs to the Special Issue Applications of Nanozymes and Other Nanomaterials in the Water Environment: Latest Advances and Prospects)

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