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Industrial Wastewater Treatment by Coagulation–Flocculation and Advanced Oxidation Processes: A Review

Journal Description

Water

Water is a peer-reviewed, open access journal on water science and technology, including the ecology and management of water resources, and is published semimonthly online by MDPI. Water collaborates with the Stockholm International Water Institute (SIWI). In addition, the American Institute of Hydrology (AIH), The Polish Limnological Society (PLS) and Japanese Society of Physical Hydrology (JSPH) are affiliated with Water and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, GEOBASE, GeoRef, PubAg, AGRIS, CAPlus / SciFinder, Inspec, and other databases.
Journal Rank: JCR - Q2 (Water Resources) / CiteScore - Q1 (Aquatic Science)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 19.1 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Companion journals for Water include: GeoHazards.
Journal Clusters of Water Resources: Water, Journal of Marine Science and Engineering, Hydrology, Resources, Oceans, Limnological Review, Coasts.

Impact Factor: 3.0 (2024); 5-Year Impact Factor: 3.3 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2073-4441

Latest Articles

20 pages, 11068 KB

Open AccessArticle

Seepage Modeling in Filled Tortuous Fractures Coupled with Porous Media Matrix: Influence of Filling Material Properties

by Weitao Liu, Debin Kong, Jiyuan Zhao, Lihong Shi and Zhenguo Mao

Water 2025, 17(23), 3386; https://doi.org/10.3390/w17233386 (registering DOI) - 27 Nov 2025

Nonlinear seepage behavior within rock fractures represents a critical and actively researched challenge in underground engineering, energy exploitation, and environmental sciences. Through the integration of nonlinear seepage theory with coupled numerical simulations of fracture flow and matrix flow, this study systematically investigates the [...] Read more.

Nonlinear seepage behavior within rock fractures represents a critical and actively researched challenge in underground engineering, energy exploitation, and environmental sciences. Through the integration of nonlinear seepage theory with coupled numerical simulations of fracture flow and matrix flow, this study systematically investigates the synergistic mechanisms governing the influence of filling particles, tortuous fractures, and porous matrices on fluid transport within fracture–porous matrix seepage systems. Key findings reveal that: (1) Horizontal fractures continuously receive fluid influx from the surrounding porous matrix, where the flow field maintains remarkable symmetry, with a critical matrix height-to-fracture aperture ratio regulating streamline divergence and convergence at the fracture outlet; (2) The flow field within horizontal fractures undergoes substantial transformation when the Reynolds number exceeds a critical threshold, while maintaining stable flow patterns and -ΔP-Q relationships below this value, demonstrating a distinct inertial-controlled flow regime transition; (3) Tortuous fracture geometries induce localized vortex formation and significant velocity fluctuations, particularly in the front and rear dip-angle zones, substantially enhancing fluid exchange efficiency compared to horizontal configurations; (4) The volumetric flow rate exhibits a non-monotonic relationship with inclination angle, peaking at approximately 36°, while a synergistic effect between fracture inclination and infill particle diameter systematically modulates pressure-drop-flow-rate relationships, with a critical d/h = 0.5 threshold distinguishing fundamentally different flow behaviors. These findings provide quantitative criteria for predicting nonlinear seepage in practical engineering scenarios involving complex fracture networks and filling materials, offering significant implications for risk assessment and drainage design in deep underground projects. Full article

(This article belongs to the Topic Human Impact on Groundwater Environment, 2nd Edition)

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14 pages, 8910 KB

Open AccessArticle

Overland Flow Generation Under Clear-Cut, 40% Thinning, and Control Conditions in a Japanese Cypress Plantation

by Moein Farahnak, Takahiro Ogura, Nobuaki Tanaka, Toko Suzaki and Koichiro Kuraji

Water 2025, 17(23), 3385; https://doi.org/10.3390/w17233385 (registering DOI) - 27 Nov 2025

Managing overland flow (OF) is essential in steep high-rainfall regions. A key strategy is to increase ground cover either naturally or through management. In Japanese cypress plantations, low ground cover increases OF and flood risks during intense rainfall. We analyzed OF and soil [...] Read more.

Managing overland flow (OF) is essential in steep high-rainfall regions. A key strategy is to increase ground cover either naturally or through management. In Japanese cypress plantations, low ground cover increases OF and flood risks during intense rainfall. We analyzed OF and soil water content (SWC) in three plots of a Japanese cypress plantation under clear-cutting, 40% thinning, and control conditions over one year (2022–2023). The SWC remained consistently higher in the clear-cut plot than in the thinned and control plots. In contrast, the OF rate was greatest in the control plot (1.97%), intermediate in the thinned plot (1.03%), and lowest in the clear-cut plot (0.58%) with 5, 5, and 35% ground cover, respectively. Event-based analyses showed that in the clear-cut plot, OF was correlated with total rainfall (r = 0.597, p = 0.003), suggesting a tendency toward subsurface flow. Conversely, in the control plot, OF was correlated with 60 min of maximum rainfall (r = 0.90, p < 0.001), indicating Hortonian flow. No significant relationships were observed in the thinned plot, likely because of response variability. Our findings imply that ground cover dynamics following management regulate OF, emphasizing the importance of continued monitoring. Full article

(This article belongs to the Section Hydrology)

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15 pages, 6013 KB

Open AccessArticle

Regional Circulation and Fate of Typical Antibiotic Discharges in the Yangtze River Estuarine Region

by Xiang Feng, Junchuan Sun, Han Zhou and Peng Zhan

Water 2025, 17(23), 3384; https://doi.org/10.3390/w17233384 - 27 Nov 2025

The discharge of antibiotics from riverine sources into estuaries and adjacent coastal seas is an emerging environmental concern. In this study, we employ seasonal averages derived from a five-year, high-resolution, three-dimensional ocean circulation model to investigate the transport and degradation of a representative [...] Read more.

The discharge of antibiotics from riverine sources into estuaries and adjacent coastal seas is an emerging environmental concern. In this study, we employ seasonal averages derived from a five-year, high-resolution, three-dimensional ocean circulation model to investigate the transport and degradation of a representative antibiotic tracer with a half-life of 31 days, released from the Yangtze River and the Qiantang River into the East China Sea. The model incorporates realistic tides, climatological winds, and seasonal runoff, enabling an examination of typical seasonal conditions. The simulated tracer remains concentrated near the estuarine outlets, with dispersion shaped by the seasonal circulation and stratification. Particle-tracking experiments show distinct pathways: Yangtze-sourced material is rapidly exported southward along the 30 m isobath, traveling about 100 km within 5–10 days, while Qiantang-sourced material exhibits much longer residence times (>30 days) within Hangzhou Bay. Vertical distributions also vary seasonally, with summer stratification confining the tracer to the surface layer and winter mixing dispersing it to deeper waters offshore. These results highlight the contrasting transport behaviors of the two river sources and illustrate how hydrodynamic conditions regulate antibiotic fate in estuarine–coastal environments. Full article

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

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22 pages, 5217 KB

Open AccessReview

Deep Learning-Driven Sandy Beach Resilience Assessment: Integrating External Forcing Forecasting, Process Simulation, and Risk-Informed Decision Support

by Yuanshu Jiang, Yingtao Zhou and Juntong Zhang

Water 2025, 17(23), 3383; https://doi.org/10.3390/w17233383 - 27 Nov 2025

Sandy beach resilience faces growing threats from extreme events and intensified human activity. Deep Learning (DL) has emerged as a powerful tool in coastal research, offering strengths in spatial feature extraction, nonlinear sequence modeling, acceleration of physical processes, and integration of multi-source data. [...] Read more.

Sandy beach resilience faces growing threats from extreme events and intensified human activity. Deep Learning (DL) has emerged as a powerful tool in coastal research, offering strengths in spatial feature extraction, nonlinear sequence modeling, acceleration of physical processes, and integration of multi-source data. This review frames resilience in three technical dimensions—resistance, recovery, and adaptation—and examines DL applications across three domains: first, monitoring and forecasting external forcing, including typhoon tracks and storm surge peak values; second, modeling and simulating beach processes, from rapid hydrodynamic forecasting to medium- and long-term shoreline evolution, and high-resolution sediment transport forecasting; and third, management and decision support, where DL methods and multi-scenario generation expand governance options, and interpretable features with uncertainty quantification enhance risk communication and policy adoption. DL complements traditional models by shortening the “observation–model–decision” cycle, expanding scenario analysis, and improving governance transparency. Challenges remain in cross-domain generalization, robustness in extreme scenarios, and data governance. This review confirms DL’s potential as a technology stack for enhancing sandy beach resilience and provides a methodological foundation for future research. Full article

(This article belongs to the Special Issue Coastal Engineering and Fluid–Structure Interactions)

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19 pages, 3194 KB

Open AccessArticle

Hybrid Nylon-6/Pumice Nonwoven Composites as Nature-Based Adsorbents for Methylene Blue Dye-Contaminated Wastewater: Insights into Monolayer and Multilayer Adsorption Mechanisms

by Carlos Alberto Ávila-Orta, Germán Alvarado-Tenorio, Erick Ricardo Ramírez-López, Gregorio Cadenas-Pliego, Víctor Javier Cruz-Delgado, María de Lourdes Hernández-Rodríguez, Lucía Fabiola Cano-Salazar, Yesenia Pérez-García, Fernando Pérez-Flores, Karla Itzel Sevilla-Vargas and Gustavo Soria-Argüello

Water 2025, 17(23), 3382; https://doi.org/10.3390/w17233382 - 26 Nov 2025

The contamination of water bodies by dye effluents from micro-scale in-house denim laundries remains a significant environmental concern in central México, particularly in the Atoyac River, where conventional treatment methods are not economically viable. This study develops and evaluates Nylon-6/pumice powder (PPw) nonwoven [...] Read more.

The contamination of water bodies by dye effluents from micro-scale in-house denim laundries remains a significant environmental concern in central México, particularly in the Atoyac River, where conventional treatment methods are not economically viable. This study develops and evaluates Nylon-6/pumice powder (PPw) nonwoven composites as hybrid adsorptive membranes for the removal of methylene blue (MB) from aqueous solutions. Pumice, a locally abundant siliceous mineral, was incorporated into Nylon-6 through melt-compounding and melt-blown fiber processing at 1 wt% and 5 wt% loadings. SEM, XRD, and TGA confirmed even filler distribution, structural stability, and the development of a porous, layered structure. Batch adsorption tests revealed a rapid initial dye adsorption, followed by a slower diffusion-controlled phase, with equilibrium achieved within 15 min for PPw and within 30 min for the composites. The data fitted both Langmuir and Freundlich isotherms, indicating that MB adsorption involved a combined mechanism: monolayer adsorption on uniform silanol/aluminol sites and multilayer physical adsorption at the polymer–mineral interfaces. Higher PPw content increased adsorption capacity (q_max = 1.1460 mg/g) and surface uniformity, resulting in favorable Freundlich exponents (n = 2). Finally, it was found that adsorption proceeds via chemisorption, where the pumice powder provides reactive sites. These findings demonstrate that Nylon-6/PPw nonwoven composites combine the strength of a synthetic material with the surface reactivity of a natural mineral, providing an effective and scalable Nature-Based Solution for decentralized dye removal, aligned with Sustainable Development Goals 6 and 12. Full article

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

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18 pages, 2238 KB

Open AccessArticle

Evaluating the Carbon and Water Footprints of Livestock Transportation in Japan

by Hanwool Do, Makoto Taniguchi and Sang-Hyun Lee

Water 2025, 17(23), 3381; https://doi.org/10.3390/w17233381 - 26 Nov 2025

This study investigates the environmental impact of rising meat consumption in Japan, focusing on water and carbon footprints associated with livestock production and transportation. We quantify the water footprint of beef cattle and swine, differentiating between direct water use (drinking and service water) [...] Read more.

This study investigates the environmental impact of rising meat consumption in Japan, focusing on water and carbon footprints associated with livestock production and transportation. We quantify the water footprint of beef cattle and swine, differentiating between direct water use (drinking and service water) and indirect water use (feed production). Our findings reveal a significant contribution of indirect water use to the overall water footprint, with 15,090.3 m³/ton for beef and 4398.6 m³/ton for swine, primarily attributed to feed crop production. These results are consistent with previous studies, with minor variations. Furthermore, we simulate transportation scenarios for beef and pork products, considering both road and rail transport. This analysis encompasses key parameters such as transportation volume, direct and indirect water use, CO₂ emissions, and fuel consumption. By evaluating the environmental implications of both livestock farming and product transportation, this study provides valuable insights for sustainable practices and informed policy development in Japan’s specific context. Our research contributes to a nuanced understanding of water use patterns in livestock production by distinguishing between direct and indirect water footprints. The integration of transportation simulations further enhances the scope of the study, offering a holistic perspective on the interconnectedness of meat production and distribution. This comprehensive approach aims to support informed decision-making processes in sustainable agriculture, environmental conservation, and policy development within Japan’s unique context. Full article

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

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20 pages, 8313 KB

Open AccessArticle

Pipe Burst Detection and Localization in Water Distribution Networks Using Faster Region-Based Convolutional Neural Network

by Kyoungwon Min, Joong Hoon Kim, Donghwi Jung, Seungyub Lee and Doosun Kang

Water 2025, 17(23), 3380; https://doi.org/10.3390/w17233380 - 26 Nov 2025

Pipe leakage and bursts are the primary contributors to water losses in water distribution networks (WDNs). However, the use of object detection techniques for identifying such failures is underexplored. This study proposes a novel deep-learning-based framework for pipe burst detection and localization (PBD&L) [...] Read more.

Pipe leakage and bursts are the primary contributors to water losses in water distribution networks (WDNs). However, the use of object detection techniques for identifying such failures is underexplored. This study proposes a novel deep-learning-based framework for pipe burst detection and localization (PBD&L) within WDNs. The framework employs spatial encoding of pressure fields obtained from hydraulic simulations of normal and burst scenarios. These encoded images serve as inputs to a faster region-based convolutional neural network (Faster R-CNN) object detection model, specifically designed for infrastructure monitoring. The framework was tested on three WDNs—Fossolo, PB23, and CM53—under varying sensor coverages (100%, 75%, and 50%). The results indicate that the model consistently achieves high detection accuracy across different network configurations, even with limited sensor availability. For Fossolo and PB23, the model demonstrated stable performance; however, for the CM53 network, accuracy decreased at full sensor coverage, possibly owing to overfitting or signal redundancy. Overall, the proposed method presents a robust solution for PBD&L in WDNs, showcasing significant practical applicability. Its ability to maintain high performance under partial observability and diverse network conditions demonstrates its potential for integration into real-time smart water management systems, enabling automated monitoring, rapid response, and improved operational efficiency. Full article

(This article belongs to the Special Issue Applications of Artificial Intelligence (AI) in Water Resources Systems)

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19 pages, 7929 KB

Open AccessArticle

Enhancing Erosion Hazard Mapping Using 2D Hydraulic-Sediment Transport Models: A Case Study from Slovenia

by Gašper Rak, Agata Pivk and Mateja Škerjanec

Water 2025, 17(23), 3379; https://doi.org/10.3390/w17233379 - 26 Nov 2025

In Slovenia, flood hazard mapping follows a standardized model-based procedure, defined by the EU Floods Directive. On the other hand, erosion hazard mapping remains largely empirical due to the absence of a unified methodology. Recent advances in 2D hydraulic and morphodynamic modelling offer [...] Read more.

In Slovenia, flood hazard mapping follows a standardized model-based procedure, defined by the EU Floods Directive. On the other hand, erosion hazard mapping remains largely empirical due to the absence of a unified methodology. Recent advances in 2D hydraulic and morphodynamic modelling offer new opportunities to integrate sediment processes into hazard assessments. This study enhances the current empirical approach to erosion hazard mapping by applying a combined 2D hydraulic-sediment transport model using HEC-RAS software version 6.4.1 and the Selška Sora River (Slovenia) as the case study area, comprising 300 ha of floodplains. Incorporating hydraulic variables and soil characteristics, the method identifies erosion-prone zones and classifies hazard levels. For the case study area, 21.9 ha of floodplains were identified as subject to erosion, and 23.9 ha as prone to deposition. Additionally, 43.8 ha of floodplains fall within the low, 1.9 ha within the medium, and 0.1 ha within the high erosion hazard class. The presented approach not only supports the national hazard mapping framework in Slovenia but also has potential applicability within broader EU hazard assessment practices. Full article

(This article belongs to the Special Issue River Channel Hydraulics, Fluvial Dynamics and Re-Opening Floodplains)

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23 pages, 3219 KB

Open AccessArticle

Reconstruction of the Evolution of the Hydro-Sedimentary Signal to the Sea from the Study of the Sedimentary Archives: Case of the Wadi Cheliff, Algeria

by Ali Hadour, Gil Mahé, Mohamed Meddi and Laurent Dezileau

Water 2025, 17(23), 3378; https://doi.org/10.3390/w17233378 - 26 Nov 2025

This work focuses on the study of several fluvial cores to help better understand the contribution of rainfall and large dams in the decline of sedimentary inputs of the Wadi Cheliff at its outlet. Therefore, three sediment cores, sampled in the lower Cheliff [...] Read more.

This work focuses on the study of several fluvial cores to help better understand the contribution of rainfall and large dams in the decline of sedimentary inputs of the Wadi Cheliff at its outlet. Therefore, three sediment cores, sampled in the lower Cheliff valley, downstream of dams, were studied through the paleohydrological approach. Then, the granulometric and geochemical profiles obtained were correlated with ¹³⁷Cs profiles, hydrological data of the Wadi Cheliff at the station closest to the Sea, Sidi bel Attar, the evolution of the rainfall signal and the data on the large dams. Such an examination aims, on the one hand, to establish a chronology of depositional accumulation and, on the other hand, to evaluate the ability of the information contained in the sedimentary archive to transcribe the evolution of the hydro-sedimentary signal and the fluctuations of the controlling factors. The results reveal a strong variation in the granulometric distribution of the deposits and a progressive decline in the rate of sediment accumulation. Thus, the upper part of the core is mainly made of particles belonging to the silt and clays granulometric classes that have accumulated with an average rate of about 1.31 cm.y⁻¹, contrary to the deposits in the lower part of the core composed of a succession of sand and finer sedimentary layers, and showing an accumulation rate much more superior, which value is evaluated to 16 cm.y⁻¹. However, the fluctuations observed in the granulometric composition, and the accumulation rate of the deposits correlated strongly with the evolution of the rainfall signal and/or the multiplication of the number of large dams. Indeed, frequent sand deposits and a higher accumulation rate correspond to the wet period before 1980. Then, the decrease in rainfall has been accompanied by a lower accumulation rate, and deposits composed mainly of clay and silt particles. In addition, the recently built dams have a drastic effect on the deposition process. Thus, the accumulation rate has been strongly slowed, and the deposits are short of the sand fraction. This study shows that the deposition process is closely linked to the hydro-sedimentary yield of the Wadi Cheliff to the sea, as it shows that the information present in the sediment archive accurately reflects the evolution of rainfall signal and the effect of large dams on the decline of sedimentary inputs from the Wadi Cheliff to the sea. Full article

(This article belongs to the Special Issue Rivers, Estuaries, and Coastal Zones: Sediment Transport and Morphodynamical Models)

42 pages, 14371 KB

Open AccessArticle

An Improved Variable-Speed Control Strategy for Air Turbine of Floating Oscillating Water Column Wave Energy Converter

by Yuxuan Liu, Cheng Zhang, Jiahao Wang and Chongwei Zhang

Water 2025, 17(23), 3377; https://doi.org/10.3390/w17233377 - 26 Nov 2025

This study proposes an improved variable-speed control strategy for Wells turbines in floating oscillating water column (OWC) wave energy converters (WECs) to address efficiency loss caused by turbine stalling. By optimizing the

ϕ

from the conventional critical value from 0.3 to 0.11, the [...] Read more.

This study proposes an improved variable-speed control strategy for Wells turbines in floating oscillating water column (OWC) wave energy converters (WECs) to address efficiency loss caused by turbine stalling. By optimizing the

ϕ

from the conventional critical value from 0.3 to 0.11, the system achieves maximum mechanical power output while avoiding stall effects. A dynamic rotor-speed controller is designed to modulate turbine rotation behavior in response to real-time airflow velocity. This approach is validated using numerical simulations and MATLAB/Simulink R2021b models under both regular and irregular wave conditions. Results show a 124% increase in turbine power compared to uncontrolled operation, with stable DC-link voltage (+0.2%) and reduce torque ripple. The strategy enhances energy conversion efficiency by 51.2% and ensures safe operation under mechanical speed limits (3000 rpm), thus offering a practical solution for offshore WEC systems. Full article

(This article belongs to the Special Issue Recent Advances in Offshore Hydrodynamics)

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16 pages, 1916 KB

Open AccessArticle

Diversity and Activity of Bacterioplankton in Shallow Lakes During Cyanobacterial Blooms

by Emilia Jankowiak, Ewa Dembowska, Marta Małecka-Adamowicz and Łukasz Kubera

Water 2025, 17(23), 3376; https://doi.org/10.3390/w17233376 - 26 Nov 2025

One of the global issues concerning aquatic environments is the increasing frequency of cyanobacterial blooms. These blooms can lead to oxygen depletion and the release of potent toxins, potentially disrupting the bacterial communities responsible for organic matter transformation and mineralization. This study aimed [...] Read more.

One of the global issues concerning aquatic environments is the increasing frequency of cyanobacterial blooms. These blooms can lead to oxygen depletion and the release of potent toxins, potentially disrupting the bacterial communities responsible for organic matter transformation and mineralization. This study aimed to examine the structural and functional diversity of bacterioplankton in three eutrophic lakes during periods of cyanobacterial bloom. The microbial communities were analyzed using high-throughput sequencing of the 16S rRNA gene, and the abundance and activity of bacterioplankton were assessed with fluorescent markers. The findings revealed that dead bacterial cells predominated in the water samples (61.16%). Taxonomic profiling identified Cyanobacteria (45.38%), Proteobacteria (20.99%), Bacteroidetes (11.37%), Actinobacteria (8.08%), and Verrucomicrobia (4.04%) as the dominant phyla. Additionally, the structure of the bacterial communities (β-diversity) showed significant variation across the lakes, but this variation did not correlate with seasonal changes. No marked effect of abiotic factors on the structural or functional diversity of the bacterioplankton was observed. These results suggest that, despite the presence of cyanobacterial dominance, microbial community structure is more closely tied to the type of lake rather than seasonal or abiotic factors. Further studies are needed to better understand the factors driving these community patterns. Full article

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

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26 pages, 6464 KB

Open AccessArticle

An Analytical Solution for the Stability Evaluation of Anti-Dip Layered Rock Slopes Under Water-Level Fluctuations in Reservoirs

by Ning Sun, Shuang Yao, Leilei Jin, Wenxi Fu, Yang Wang, Fei Ye and Zhihao Wu

Water 2025, 17(23), 3375; https://doi.org/10.3390/w17233375 - 26 Nov 2025

Significant fluctuations in reservoir water levels occur seasonally during the flood period, adversely affecting the stability of bank slopes. In this paper, a modified mechanical model for the flexural toppling of anti-dip rock slopes under water level fluctuations is established, and an actual [...] Read more.

Significant fluctuations in reservoir water levels occur seasonally during the flood period, adversely affecting the stability of bank slopes. In this paper, a modified mechanical model for the flexural toppling of anti-dip rock slopes under water level fluctuations is established, and an actual deflection equation for rock slabs is derived. The critical length for the flexural toppling failure of rock slabs is calculated, which can be used to evaluate slope stability. Multiple linear regression analysis reveals the relative degree of the influence of each parameter (such as rock slab thickness, rock layer dip angle, water level height, etc.) on the critical length. The results indicate that rock slab thickness plays a controlling role in slope stability. The failure mechanisms of the slope under the influence of water level fluctuations are revealed through fluid–solid coupling numerical simulations. The results indicate that the rise in water level reduces the strength of the rock mass in the submerged zone and generates significant water pressure on the rock mass at the slope toe, leading to its cracking. A rapid drop in water level generates seepage forces detrimental to slope stability and carries away fractured rock particles at the slope toe, ultimately causing slope failure. Finally, the reliability and applicability of the proposed method are validated through numerical simulations, case studies, and comparisons with existing analytical solutions. Full article

(This article belongs to the Section Hydrogeology)

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17 pages, 2235 KB

Open AccessArticle

Reliability Assessment of Long-Service Gravity Dams Based on Historical Water Level Monitoring Data

by Yuzhou Lu, Huijun Qi, Ziwei Li, Xiaohu Du, Chaoning Lin, Taozhen Sheng and Tongchun Li

Water 2025, 17(23), 3374; https://doi.org/10.3390/w17233374 - 26 Nov 2025

This paper addresses the challenge of systemic extreme risk in long-service gravity dams under human-controlled operation. It is the first study to construct a Generalized Extreme Value (GEV) distribution model using long-term operational monitoring data. The model, validated by multiple statistical tests and [...] Read more.

This paper addresses the challenge of systemic extreme risk in long-service gravity dams under human-controlled operation. It is the first study to construct a Generalized Extreme Value (GEV) distribution model using long-term operational monitoring data. The model, validated by multiple statistical tests and engineering boundary conditions, is then applied within a Response Surface Method-Monte Carlo (RSM-MC) reliability framework. Results indicate that the historical GEV model accurately captures the high-water-level tail characteristics and significantly overcomes the risk underestimation inherent in the uniform distribution model. Compared to the Log-Pearson Type III (Log-P3) design condition model, the GEV model yields a significantly lower probability of failure, e.g., the probability of cracking at the dam heel, the most sensitive failure mode, is reduced by nearly six times. This quantitative difference fully demonstrates GEV’s ability to precisely quantify the effective risk reduction achieved by human control, establishing a more scientific and realistic foundation for risk assessment of long-service gravity dams. Full article

(This article belongs to the Special Issue Risk Assessment and Mitigation for Water Conservancy Projects)

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16 pages, 2228 KB

Open AccessArticle

Groundwater of Parque Rural del Nublo—UNESCO Biosphere Reserve and World Heritage Site “El Molinillo” Spring—Gran Canaria—Canary Islands—Spain

by Eduardo Navarro

Water 2025, 17(23), 3373; https://doi.org/10.3390/w17233373 - 26 Nov 2025

This study discusses the unique features of the rural park Parque Rural del Nublo (Gran Canaria) that resulted in the designation of this site as UNESCO’s Biosphere Reserve. Due to its indigenous flora and fauna, its mild climate and its farming lands, this [...] Read more.

This study discusses the unique features of the rural park Parque Rural del Nublo (Gran Canaria) that resulted in the designation of this site as UNESCO’s Biosphere Reserve. Due to its indigenous flora and fauna, its mild climate and its farming lands, this park is considered as an outdoor “sustainable research laboratory”. This paper describes the main features (source, denomination, classification, municipality, year of declaration and hydro-chemical facies) of some of the many groundwater springs found in the park. The quality of the drinking water obtained from the spring “El Molinillo”, located in the basin of the municipality of Tejeda, is analysed by assessing its organoleptic, physico-chemical, chemical and bacteriological properties. Considering that it is described as “natural mineral water”, based on the taxonomy for mineral–medicinal waters, the water from “El Molinillo” is classified as hypothermal, alkaline and very soft water, with a low conductivity, a very weak mineralisation and a significant silica content. The water especially contains the following ions: bicarbonate, chloride, magnesium and calcium. The paper describes several pharmacological effects and therapeutic indications attributed to this water, analysing the impact of its silica content on human and plant health. The paper concludes that the park should be permanently protected as a World Heritage Site, and the water obtained from “El Molinillo” is classified as “drinking water”, “natural mineral water” and “mineral–medicinal water”. Full article

(This article belongs to the Special Issue Groundwater for Health and Well-Being)

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21 pages, 6126 KB

Open AccessArticle

Evaluating Agricultural Drought in the Haihe River Basin Using an Improved Crop Moisture Index

by Mingzhi Yang, Xinyang Li, Jijun Xu, Huan Jing, Xinyi Zhang and Lianhai Sang

Water 2025, 17(23), 3372; https://doi.org/10.3390/w17233372 - 26 Nov 2025

In large irrigated agricultural regions under intensive human management, irrigation profoundly influences agricultural drought dynamics. High-frequency irrigation markedly alters natural farmland soil moisture, causing traditional drought indices to distort the actual severity of human-modified agricultural drought and leading to substantial monitoring deviations. In [...] Read more.

In large irrigated agricultural regions under intensive human management, irrigation profoundly influences agricultural drought dynamics. High-frequency irrigation markedly alters natural farmland soil moisture, causing traditional drought indices to distort the actual severity of human-modified agricultural drought and leading to substantial monitoring deviations. In this work, an improved agricultural drought index based on the Crop Moisture Index (CMI) was developed to accurately characterize drought conditions, using the Haihe River Basin as a case study. The CMI’s water balance equation was revised by incorporating an auto-irrigation threshold method with crop coefficients and water stress coefficients. Furthermore, the improved CMI explicitly models irrigation by defining auto-irrigation thresholds based on the critical growth stages of the main crops. The performance of the original and improved CMI was evaluated by comparing their simulated soil moisture and drought detection accuracy against benchmark data derived from measurements across yearly, monthly, and weekly scales. The spatial evolution of a major 2002 drought in North China was also reconstructed to assess the indices’ performance. The results showed that: (1) The revised soil water balance equation achieved significantly lower relative errors than the original equation across all time scales; (2) The improved CMI consistently demonstrated higher drought identification accuracy rates than the original CMI; (3) Drought patterns monitored by the improved CMI showed superior alignment with actual conditions, confirming that it has enhanced applicability for agricultural drought assessment and demonstrates clear advantages for drought assessment in large-scale irrigated agriculture. This work provides crucial insights into the driving mechanisms of agricultural drought under intense human interventions and offers valuable guidance for drought risk management in major agricultural zones. Full article

(This article belongs to the Section Water, Agriculture and Aquaculture)

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11 pages, 1470 KB

Open AccessArticle

Response of Phytoplankton to Nutrient Limitation in the Ecological Restoration of a Subtropical Shallow Lake

by Shi Fu, Zhenmei Lin, Hu He, Kuanyi Li, Jian Gao, Zhengwen Liu and Jinlei Yu

Water 2025, 17(23), 3371; https://doi.org/10.3390/w17233371 - 26 Nov 2025

Lake restoration, achieved through a combination of biomanipulation and the recovery of submerged macrophytes, can effectively reduce nutrient concentrations, thereby suppressing phytoplankton biomass. Nevertheless, there is limited knowledge regarding the impact of nutrient limitation in phytoplankton biomass on lake restoration efforts. We compared [...] Read more.

Lake restoration, achieved through a combination of biomanipulation and the recovery of submerged macrophytes, can effectively reduce nutrient concentrations, thereby suppressing phytoplankton biomass. Nevertheless, there is limited knowledge regarding the impact of nutrient limitation in phytoplankton biomass on lake restoration efforts. We compared the changes in nutrient levels and phytoplankton biomass (measured by chlorophyll a, Chl a) between restored and unrestored areas of a subtropical shallow Lake Yiai. Furthermore, we assessed the nutrient limitation patterns in these two areas through field nutrient addition experiments conducted during the summer. Monitoring results indicated that mean concentrations of Chl a and nutrients were significantly lower (t-test p < 0.0001) in the restored area compared to the unrestored area. In the nutrient addition experiment, phytoplankton biomass was nitrogen-limited in the unrestored part, whereas it was co-limited by both nitrogen and phosphorus in the restored area. These findings suggest that nutrient limitation may serve as a crucial mechanism in sustaining low phytoplankton biomass following the restoration of shallow lakes, particularly during the summer season, with the recovery of submerged macrophytes. Full article

(This article belongs to the Special Issue Impacts of Environmental Change and Human Activities on Aquatic Ecosystems, 2nd Edition)

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22 pages, 3215 KB

Open AccessArticle

Resolving Nitrate Sources in Rivers Through Dual Isotope Analysis of δ¹⁵N and δ¹⁸O

by Shuai Wang, Heng Li, Tao Kang, Ruixin Li and Chengzhong Zhang

Water 2025, 17(23), 3370; https://doi.org/10.3390/w17233370 - 26 Nov 2025

Nitrate (NO₃⁻) pollution in rivers within agricultural regions has become a global issue that cannot be ignored. Identifying the sources and transformation processes of NO₃⁻ is crucial for safeguarding water quality in agricultural catchment areas. This study traces [...] Read more.

Nitrate (NO₃⁻) pollution in rivers within agricultural regions has become a global issue that cannot be ignored. Identifying the sources and transformation processes of NO₃⁻ is crucial for safeguarding water quality in agricultural catchment areas. This study traces the sources and transformation processes of NO₃⁻ in the Songhua River basin of Northeast China by analysing hydrochemical parameters and NO₃⁻ dual isotopes (δ¹⁵N and δ¹⁸O) in river water. It estimates the proportional contributions of NO₃⁻ sources using Bayesian modelling via the MixSIAR package （3.1.12）in the R programming language. (1) The relatively low NO₃⁻/Cl⁻ ratio and high chloride concentrations in the upstream section indicate that the primary sources of NO₃⁻ in this area are manure and sewage (M&S). (2) Dual isotope analysis of NO₃⁻ indicates that the primary sources of NO₃⁻ in the Songhua River basin are M&S, soil nitrogen (SN), and chemical fertilizers (CF). (3) Nitrification occurs throughout the entire watershed. (4) Model estimation results indicate that SN constitutes the primary source of NO₃⁻ throughout the entire watershed (48%), with no significant variation observed across the studied river sections. However, other major NO₃⁻ sources exhibit spatially significant differences, primarily manifested as follows: M&S constitute the primary upstream source of NO₃⁻ (39%), whilst downstream contributions are predominantly attributable to CF (20%). Intermediate regions experience combined impacts from both MS and CF sources. Full article

(This article belongs to the Special Issue Advanced Research in Non-Point Source Pollution of Watersheds)

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26 pages, 6618 KB

Open AccessArticle

From Flood Vulnerability Mapping Using Coupled Hydrodynamic Models to Optimizing Disaster Prevention Funding Allocation: A Case Study of Wenzhou

by Anfeng Zhu, Yinxiang Xu, Jiahao Zhong, Jingtao Hao, Yongkang Ma, Gang Xu, Zhiyang Chen and Zegen Wang

Water 2025, 17(23), 3369; https://doi.org/10.3390/w17233369 - 26 Nov 2025

Urban areas face increasing flood risks due to extreme precipitation and anthropogenic activities, which threaten residents’ livelihoods. However, conventional research often lacks a forward-looking perspective, failing to integrate future flood vulnerability assessments with pre-disaster resource allocation. To address this gap, the combination of [...] Read more.

Urban areas face increasing flood risks due to extreme precipitation and anthropogenic activities, which threaten residents’ livelihoods. However, conventional research often lacks a forward-looking perspective, failing to integrate future flood vulnerability assessments with pre-disaster resource allocation. To address this gap, the combination of spatiotemporal flood vulnerability distributions and a pre-disaster funding allocation model serves to enhance urban flood resilience and recovery capabilities. Using Wenzhou City as a case study, a Hydrodynamic Flood Vulnerability Framework (VHCF) was applied to assess current and future vulnerabilities based on hydrodynamic modeling, which revealed distinct spatial patterns in vulnerability. Specifically, a coupled hydrological–hydrodynamic model and the Patch-generating Land Use Simulation (PLUS) model were integrated to simulate flood dynamics under future land-use scenarios for the years 2020 and 2030. A subsequent funding optimization model, based on the VHCF, was developed to prioritize disaster prevention resources for both current and projected high-risk areas. This approach achieves efficient resource allocation by balancing multidimensional flood vulnerability dynamics. The results indicate that extremely high-risk and high-risk zones are predominantly distributed along river corridors and urban centers. From 2020 to 2030, the areal proportion across all vulnerability levels exhibited an increasing trend. Following funding optimization, the coverage rates for low-risk and extremely low-risk zones reached 88.29% and 87.93% in 2020 and 2030, respectively. This methodology provides a scientific basis for decision-makers to enhance urban flood resilience, facilitate post-disaster recovery, and advance sustainable disaster prevention and mitigation strategies. Full article

(This article belongs to the Special Issue Water-Related Disasters in Adaptation to Climate Change)

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19 pages, 681 KB

Open AccessArticle

Ecotoxicological Assessment of Perfluorooctane Sulfonate and Perfluorooctanoic Acid Following Biodegradation: Insights from Daphnia magna Toxicity and Yeast Estrogen Screen Assays

by Muyasu Grace Kibambe and Maggy Ndombo Benteke Momba

Water 2025, 17(23), 3368; https://doi.org/10.3390/w17233368 - 26 Nov 2025

Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) pose significant health risks through various exposure pathways, including ingestion of contaminated food and water, as well as dermal absorption. Aquatic organisms are especially at risk, as water bodies serve as primary pathways for the transport [...] Read more.

Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) pose significant health risks through various exposure pathways, including ingestion of contaminated food and water, as well as dermal absorption. Aquatic organisms are especially at risk, as water bodies serve as primary pathways for the transport and transformation of these chemicals. While the biodegradation study was previously performed using a bacterial consortium from the activated sludge compartment at Zeekoegat WWTP, the ecotoxicological implications of the treated effluents remained unclear, particularly given the potential presence of degradation products. To address this gap, the present study used bioassays to evaluate the acute toxicity and endocrine-disrupting potential of PFOS and PFOA. For this purpose, PFOS and PFOA concentrations ranged from 58 ng/L to 1050 ng/L, and two types of bioassays were used: the Daphnia magna acute toxicity test, which examined the short-term lethal effects of the samples on a small freshwater organism (Daphnia magna), and the Yeast Estrogen Screen (YES), which measured estrogenic activity, an important indicator of potential endocrine disruption. Results revealed detectable estrogenic activity at environmentally relevant concentrations, with PFOS showing higher activity than PFOA. The estradiol equivalency (EEQ) values in samples containing PFOA ranged from 0.23 ± 0.029 ng/L to 3.15 ± 0.056 ng/L and from 0.43 ± 0.036 ng/L to 1.96 ± 0.086 ng/L in samples containing PFOS. Daphnia magna bioassays showed 100% mortality in samples containing PFOS at concentrations ≥ 62 ng/L and in samples containing PFOA at concentrations ≥ 142 ng/L, classifying them as ‘Very High Acute Hazard’ falling into Hazard Class V (100% mortality) according to the classification system proposed in 2003 by Persoone and co-workers. These bioassays helped to determine whether the degradation products were more toxic compared to the parent compounds, thereby supporting the objective of this study to assess environmental safety post-treatment. Full article

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

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17 pages, 2833 KB

Open AccessArticle

Variable Selection and Model Comparison for Optimizing Machine Learning-Based TOC Prediction

by Kang Bin Ju and Dong Woo Jang

Water 2025, 17(23), 3367; https://doi.org/10.3390/w17233367 - 25 Nov 2025

This study developed a rapid and real-time model for predicting total organic carbon (TOC), which is an alternative to the conventional biochemical oxygen demand (BOD) and chemical oxygen demand (COD) indicators. The influence of input variable selection methods and machine learning hyperparameter tuning [...] Read more.

This study developed a rapid and real-time model for predicting total organic carbon (TOC), which is an alternative to the conventional biochemical oxygen demand (BOD) and chemical oxygen demand (COD) indicators. The influence of input variable selection methods and machine learning hyperparameter tuning on TOC prediction accuracy was compared using ten-year water quality monitoring data. The analysis showed that TOC exhibited strong correlations with COD, T-P, BOD, and ammonia nitrogen (NH₃-N). Principal component analysis confirmed that the primary factors driving TOC variation were associated with organic matter and nutrient pollution. Prediction models were developed using a multilayer perceptron (MLP) and random forest (RF). On average, the MLP model outperformed the RF model by approximately 20%, and COD consistently appeared as a critical predictor in all top-ranked feature sets. Finally, grid search-based hyperparameter tuning of the MLP model with the optimal variable set (DO, COD, T-P, DTP, PO₄-P) increased the coefficient of determination from 0.7496 to 0.7562. The findings demonstrate that precise exploration of variable combinations and stronger model regularization are essential for improving prediction performance in TOC modeling. This study provides a foundation for future development of predictive models that integrate external environmental factors such as nonpoint source pollution. Full article

(This article belongs to the Special Issue Advanced Aquaculture Water Quality Management Research)

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