Water

21 pages, 1198 KB

Open AccessEditor’s ChoiceArticle

pH-Dependent Reactivity, Radical Pathways, and Nitrosamine Byproduct Formation in Peroxynitrite-Mediated Advanced Oxidation Processes

by Zhe Chen, Dandan Rao, Jian Zhang and Bo Sun

Water 2026, 18(1), 97; https://doi.org/10.3390/w18010097 - 31 Dec 2025

Cited by 2 | Viewed by 1154

Abstract

Peroxynitrite (ONOOH/ONOO⁻) is increasingly recognized as a key intermediate in advanced oxidation processes (AOPs), yet its role in water treatment remains insufficiently defined. This study provides mechanistic insights into peroxynitrite-mediated AOPs through competition kinetics method, demonstrating that both decomposition and pollutant [...] Read more.

Peroxynitrite (ONOOH/ONOO⁻) is increasingly recognized as a key intermediate in advanced oxidation processes (AOPs), yet its role in water treatment remains insufficiently defined. This study provides mechanistic insights into peroxynitrite-mediated AOPs through competition kinetics method, demonstrating that both decomposition and pollutant degradation are strongly pH-dependent, with ONOOH dominating stability and radical pathways across pH 5.0−9.0, while its decay rate decreases from 1.2 s⁻¹ to 0.0022 s⁻¹. The interplay of HO^• and diverse reactive nitrogen species (RNS, including reactive nitrogen radicals and peroxynitrite) dictates pollutant-specific degradation efficiencies, with RNS showing a unique reliance in degrading bisphenol A—contributing up to 66.7% at pH 8.0. Buffer chemistry further modulates these pathways: bicarbonate accelerates peroxynitrite decay via CO₂ and CO₃^•−-mediated acceleration (resulting in a 361.9% increase at pH 9.0), while borate promotes reactive nitrogen radical formation but suppresses HO^• contributions. Importantly, peroxynitrite was shown to facilitate N-nitrosodimethylamine formation in the presence of dimethylamine, with yields maximized under alkaline conditions and attenuated by bicarbonate. These quantitative findings underscore the critical roles of pH and buffer chemistry in optimizing peroxynitrite-based water treatment while mitigating byproduct risks. Full article

(This article belongs to the Special Issue Novel Advanced Oxidation Technology for Water Treatment)

► Show Figures

Graphical abstract

16 pages, 4982 KB

Open AccessEditor’s ChoiceArticle

Evaluation of Sediment Deposition Processes in Hydroelectric Plant: Case Study of Espora Reservoir, Brazil

by Assunção Andrade de Barcelos, João Batista Pereira Cabral, Fernanda Luisa Ramalho, Patrícia da Silva Gomes, Hudson Moraes Rocha, Valter Antonio Becegato and Alexandre Tadeu Paulino

Water 2026, 18(1), 94; https://doi.org/10.3390/w18010094 - 31 Dec 2025

Cited by 1 | Viewed by 1255

Abstract

Studying sedimentary distribution in water reservoirs is essential to understand the depositional processes and develop sustainable environmental management strategies. Characterization of deposited sediments provides information about the sources of particulate matter, transport patterns and predominant deposition mechanisms in different compartments of the reservoir. [...] Read more.

Studying sedimentary distribution in water reservoirs is essential to understand the depositional processes and develop sustainable environmental management strategies. Characterization of deposited sediments provides information about the sources of particulate matter, transport patterns and predominant deposition mechanisms in different compartments of the reservoir. This study aimed to evaluate active deposition processes and to improve the understanding of sedimentation in water reservoirs. In this case, the Espora hydroelectric power plant, located on the Corrente River, southwestern Goiás, Brazil, was employed as a model environment. Sediment cores were collected at 29 points along the reservoir, covering different aquatic compartments. Particle-size analysis of the sediments was performed based on established methodologies using textural classification to identify sedimentary facies. The results indicated the predominance of stream deposits (sandy material) in areas where water flow velocity was higher, and bed deposits, composed predominantly of clays and silts, in regions of lower water flow velocity and greater depth. Full article

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

► Show Figures

Graphical abstract

22 pages, 2990 KB

Open AccessEditor’s ChoiceArticle

A New Semi-Empirical Model to Predict Vehicle Instability in Urban Flooding

by Omayma Amellah

Water 2026, 18(1), 80; https://doi.org/10.3390/w18010080 - 28 Dec 2025

Cited by 2 | Viewed by 1535

Abstract

Urban floods frequently destabilize most objects they encounter, including vehicles, which potentially worsens flood impacts, leading to significant casualties and material losses. Improving the prediction of vehicle instability under flood conditions is therefore essential for effective risk assessment and emergency management. This work [...] Read more.

Urban floods frequently destabilize most objects they encounter, including vehicles, which potentially worsens flood impacts, leading to significant casualties and material losses. Improving the prediction of vehicle instability under flood conditions is therefore essential for effective risk assessment and emergency management. This work introduces a new physics-based, hazard assessment model for vehicle instability in urban floodwaters. The core of the model is the construction of a comprehensive parameter that integrates the main hydraulic mechanisms responsible for vehicle destabilization within a single and integrative formulation. An extensive set of experimental data covering multiple vehicle types was used and integrated into the modelling framework. Through calibration, model parameters were determined for three representative vehicle categories, allowing the derivation of distinct critical stability curves as functions of flow depth and velocity. Vehicle stability is evaluated using a physics-based force balance approach that explicitly accounts for the interaction between flood hydrodynamics and vehicle physical characteristics, enhancing model adaptability across different vehicle types and flood scenarios. The proposed model is validated through comparison with existing experimental data and stability criteria, including widely used guidelines. The results show good agreement while demonstrating improved accuracy in predicting critical stability thresholds for modern vehicles. Overall, the model provides a generalizable parameter for flood hazard assessment, with direct applications in urban flood risk mapping and decision support for emergency management. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

24 pages, 2004 KB

Open AccessEditor’s ChoiceReview

Biofilm Control in Wastewater Treatment: A Review Regarding the Application of Quorum Sensing and Quenching Processes and Future Perspectives

by Ioannis Masatlis, Alexandros Chatzis and Anastasios Zouboulis

Water 2026, 18(1), 77; https://doi.org/10.3390/w18010077 - 27 Dec 2025

Cited by 8 | Viewed by 3299

Abstract

Wastewater treatment (WWT) is among the main challenges in environmental engineering. However, conventional wastewater treatment methods are limited by several aspects, mostly related to efficiency, excessive energy requirements, and surplus sludge production. Thus, the alternative use of biofilms (instead of suspended biomass/activated sludge [...] Read more.

Wastewater treatment (WWT) is among the main challenges in environmental engineering. However, conventional wastewater treatment methods are limited by several aspects, mostly related to efficiency, excessive energy requirements, and surplus sludge production. Thus, the alternative use of biofilms (instead of suspended biomass/activated sludge systems) has garnered particular interest, especially due to their ability to sustain high microbial activity and withstand extreme conditions. This review aims to provide an interdisciplinary and comprehensive approach to understanding the main interactions occurring in biofilms, emphasizing, specifically, the quorum sensing (QS) and the quorum quenching (QQ) mechanisms, as well as to address their relative applications in controlling biofouling problems, e.g., during the operation of membrane bioreactors (MBRs). The review summarizes and analyzes the latest developments, highlights the relevant research gaps in the literature, and links microbiological knowledge with related technological applications. Full article

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

► Show Figures

Graphical abstract

31 pages, 8862 KB

Open AccessEditor’s ChoiceArticle

Machine-Learned Emulators for Teleconnection Discovery and Uncertainty Quantification in Coupled Human–Natural Systems

by Asim Zia, Patrick J. Clemins, Muhammad Adil, Andrew Schroth, Donna Rizzo, Panagiotis D. Oikonomou and Safwan Wshah

Water 2026, 18(1), 79; https://doi.org/10.3390/w18010079 - 27 Dec 2025

Cited by 1 | Viewed by 1679

Abstract

Introduction: Traditional approaches to discover teleconnections and quantify uncertainty, such as global sensitivity analysis, Monte Carlo experiments, decomposition analysis, etc., are computationally intractable for large-scale process-based Coupled Human and Natural Systems (CHANS) models. This study hypothesizes that machine-learned emulator models provide “computationally efficient” [...] Read more.

Introduction: Traditional approaches to discover teleconnections and quantify uncertainty, such as global sensitivity analysis, Monte Carlo experiments, decomposition analysis, etc., are computationally intractable for large-scale process-based Coupled Human and Natural Systems (CHANS) models. This study hypothesizes that machine-learned emulator models provide “computationally efficient” algorithms for discovering teleconnections and quantifying uncertainty within and across dynamically evolving human and natural systems. Objectives: This study aims to harness machine-learned emulator models to discover the relative contributions of internal- versus external-to-the-lake teleconnected processes driving the emergence of Harmful Algal Blooms (HABs) and trophic regime shifts. Three objectives are pursued: (1) build emulators; (2); quantify uncertainty and (3) identify teleconnections. Methods: Six machine-learned emulator models are trained on ~3.8 million observations for ~52 features derived from 332 scenarios simulated in an integrated process-based CHANS model that predicts water quality in Missisquoi Bay of Lake Champlain under alternate hydro-climatic and nutrient management scenarios for the 2001–2047 timeframe. The regression random forest (RRF), regression LightGBM (RLGBM) and regression XGBoost (RXGB) models predict the average surface mean of ChlA. Further, the classifier random forest (CRF), classifier LightGBM (CLGBM) and classifier XGBoost (CXGB) predict four trophic states of Missisquoi Bay. Relative importance and partial dependence plots are derived from all six emulator models to quantify relative uncertainty and importance of external-to-the-lake (climatic, hydrological, nutrient management) and internal-to-the-lake (P and N sediment release) drivers of HABs. Results: RXGB (R² = 96%, 48 features) outperforms RLGBM (R² = 95%, 37 features) and RRF (R² = 93%, 20 features) in predicting the average surface mean of ChlA. CLGBM (F1 = 96.15, 4 features) outperforms CXGB (F1 = 95.66, 48 features) and CRF (F1 = 93.06, 23 features) in predicting four trophic states. We discovered that predictor variables representing snow, evaporation and transpiration dynamics teleconnect hydro-climatic processes occurring in terrestrial watersheds with the biogeochemical processes occurring in the freshwater lakes. Conclusions: The proposed approach to discover teleconnections and quantify uncertainty through machine-learned emulator models can be scaled up in different watersheds and lakes for informing integrated water governance processes. Full article

(This article belongs to the Special Issue Artificial Intelligence in Water Science: Opportunities, Prospects, and Concerns)

► Show Figures

Figure 1

13 pages, 12941 KB

Open AccessEditor’s ChoiceArticle

Isolation and Identification of Pseudoalteromonas agarivorans LJ53, a Pathogenic Bacterium Causing Bleaching Disease in Saccharina japonica

by Ying Ouyang, Ruojing Tu, Jiapeng Li, Xianzhen Zhou, Chenhui Zhong, Lijun Fu and Jiangwei Li

Water 2026, 18(1), 66; https://doi.org/10.3390/w18010066 - 25 Dec 2025

Cited by 2 | Viewed by 1107

Abstract

As a major export crop in China, Saccharina japonica cultivation suffers from significant economic losses due to disease outbreaks, with pathogen identification remaining a critical bottleneck for mariculture. In this study, a dominant bacterial strain, LJ53, was isolated from the diseased farmed S. [...] Read more.

As a major export crop in China, Saccharina japonica cultivation suffers from significant economic losses due to disease outbreaks, with pathogen identification remaining a critical bottleneck for mariculture. In this study, a dominant bacterial strain, LJ53, was isolated from the diseased farmed S. japonica. Artificial challenge assay confirmed that this strain is the direct causative agent of bleaching symptoms on sporophytes. Based on morphological characteristics and 16S rRNA gene-based phylogeny, it was identified as Pseudoalteromonas agarivorans LJ53. Ultrastructural observation revealed that this strain destroyed host cells and caused typical pathological changes such as chloroplast disintegration. Interestingly, metagenomic analysis showed no significant difference in the relative abundance of this pathogen between healthy and diseased S. japonica tissues. However, the co-occurrence network of the disease community exhibited increased connectivity, altered modularity, and features characteristic of microbial dysbiosis. This dysbiosis disrupts the water ecological balance by destabilizing microbial symbiosis and nutrient cycling, which are essential for overall ecosystem resilience. As a result, these imbalances can exacerbate disease transmission and weaken the self-regulating capacity of marine environment, highlighting the need for integrated management strategies to restore equilibrium. These findings provide a theoretical basis for elucidating the mechanisms of bacterial diseases in S. japonica and developing future control strategies. Full article

(This article belongs to the Special Issue Aquaculture Productivity and Environmental Sustainability)

► Show Figures

Figure 1

14 pages, 993 KB

Open AccessEditor’s ChoiceArticle

Combating Toxic Blooms of Prymnesium parvum: Hydrogen Peroxide Influence on the Haptophyte, Other Phytoplankton Taxa, and Concentrations of Prymnesins Under Experimental Conditions

by Iwona Jasser, Tümer O. Aykut, Robin Crucitti-Thoo, Agnieszka Pasztaleniec, Robert Konkel and Hanna Mazur-Marzec

Water 2026, 18(1), 52; https://doi.org/10.3390/w18010052 - 24 Dec 2025

Cited by 2 | Viewed by 1480

Abstract

In the summer of 2022, massive blooms of the toxic haptophyte Prymnesium parvum triggered one of the most significant ecological disasters ever recorded in the Odra River, resulting in massive fish and mollusk kills and severe economic damage. Having shown promise for treating [...] Read more.

In the summer of 2022, massive blooms of the toxic haptophyte Prymnesium parvum triggered one of the most significant ecological disasters ever recorded in the Odra River, resulting in massive fish and mollusk kills and severe economic damage. Having shown promise for treating other types of phytoplankton blooms, we applied various concentrations of hydrogen peroxide (HP) in an experimental setting using waters collected from the Gliwice Canal; a location with extensive proliferations of P. parvum. In the first stage of our experiment, a single application as low as 14 mg H₂O₂/L successfully reduced P. parvum biomass and prymnesin concentrations, measured using newly obtained prymnesin standards, with limited negative impact on other phytoplankton. In the second stage of the experiment, we reintroduced an inoculum of the canal water containing the haptophyte bloom. The simulated renewal of the phytoplankton community led to higher P. parvum biomass and elevated prymnesin concentrations, possibly due to nutrient release after HP application or reduced phytoplankton competition. We observed differences in the toxin profile compared with control conditions, suggesting changes in the haptophyte ecotypes in the experimental treatments. The results suggest that HP can be successfully used to combat P. parvum blooms, though caution is warranted with higher concentrations. Full article

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

► Show Figures

Figure 1

14 pages, 947 KB

Open AccessEditor’s ChoiceArticle

Effects of Hydraulic Retention and Inorganic Carbon During Municipal Wastewater Treatment Using a Microalgal Bacterial Consortium

by Thinojah Thiruchchelvam, Mohammed Johir, K. C. Bal Krishna and Arumugam Sathasivan

Water 2026, 18(1), 57; https://doi.org/10.3390/w18010057 - 24 Dec 2025

Cited by 2 | Viewed by 1097

Abstract

Municipal wastewater (MWW) was treated using a microalgal–bacterial consortium without mechanical aeration. An inoculum for the reactor was prepared by acclimatizing Chlorella vulgaris to MWW and supplementing with a small amount of activated sludge. The hydraulic retention time (HRT) and solids retention time [...] Read more.

Municipal wastewater (MWW) was treated using a microalgal–bacterial consortium without mechanical aeration. An inoculum for the reactor was prepared by acclimatizing Chlorella vulgaris to MWW and supplementing with a small amount of activated sludge. The hydraulic retention time (HRT) and solids retention time (SRT) were progressively reduced from 6.67 to 1.17 d and from 10 to 6.67 d, respectively, to test the process robustness under realistic MWW operation. The COD removal efficiency was 88% at 0.23 kg-COD/m³/d. Mass balance suggested the major nitrogen and phosphorus removal mechanism as assimilation. A high percentage (80%) of oxidized nitrogen indicated an efficient nitrification at all HRTs. Inorganic carbon (IC) balance calculation explained the observed IC dynamics. The chlorophyll a-to-mixed liquor volatile suspended solids (MLVSS) ratio and percentage of nitrite responded to IC limitation and supplementation. The mixed liquor exhibited excellent settleability (sludge volume index: 42 mL/g) with dense algal–bacterial flocs. An increased organic loading rate, however, reduced daytime dissolved oxygen, suggesting limitation under non-aerated conditions. These findings demonstrate the potential of microalgal–bacterial systems to achieve efficient COD removal and nitrification at realistic HRTs without aeration while emphasizing the importance of IC management. Full article

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

► Show Figures

Figure 1

16 pages, 2394 KB

Open AccessEditor’s ChoiceArticle

Phytoplankton Community Shifts Under Nutrient Imbalance in the Yellow River Estuary and Adjacent Coastal Waters

by Yifei Li, Mingtao Zhao, Hongwei Ren, Dongrui Zhang, Ke Yan, Zhigang Guo and Ying Chen

Water 2026, 18(1), 54; https://doi.org/10.3390/w18010054 - 24 Dec 2025

Cited by 4 | Viewed by 1850

Abstract

The phytoplankton community structure is regulated by environmental conditions, influencing ecosystem stability and productivity. In August 2023, a survey was conducted at 28 stations in the Yellow River Estuary (YRE) and adjacent coastal waters, where phytoplankton communities, nutrients, chlorophyll-a, and other environmental factors [...] Read more.

The phytoplankton community structure is regulated by environmental conditions, influencing ecosystem stability and productivity. In August 2023, a survey was conducted at 28 stations in the Yellow River Estuary (YRE) and adjacent coastal waters, where phytoplankton communities, nutrients, chlorophyll-a, and other environmental factors were synchronously analyzed. Across-site comparison, redundancy analysis (RDA), and K-means clustering were applied to characterize spatial patterns and identify key factors controlling diatom to dinoflagellate ratios and dominant taxa. The nutrient structure, particularly DIN/PO₄³⁻, corresponded closely with the spatial shift between diatom and dinoflagellate dominance. Offshore areas dominated by diatoms (Cerataulina, Chaetoceros) exhibited higher salinity and more balanced nutrient ratios, whereas nearshore zones influenced by Yellow River inputs had high DIN, low PO₄³⁻, and evident phosphorus limitation, favoring dinoflagellates (Noctiluca, Heterodinium). These results indicate that nutrient imbalance and salinity gradients are likely the main drivers of diatom-to-dinoflagellate transitions and shape the phytoplankton composition in the estuary coastal waters. This study provides insights linking nutrient imbalance to phytoplankton community succession and advances the understanding of estuarine phytoplankton dynamics. Full article

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

► Show Figures

Figure 1

15 pages, 1890 KB

Open AccessEditor’s ChoiceArticle

Freshwater Quality Criteria for the Protection of Aquatic Life and Ecological Risk Assessment for Sulfamethoxazole in China

by Zeya Zhang, Yili Fan, Lan Wang, Weibo Zhang and Yingchen Bai

Water 2026, 18(1), 45; https://doi.org/10.3390/w18010045 - 23 Dec 2025

Cited by 1 | Viewed by 1772

Abstract

Sulfamethoxazole (SMX) has adverse effects on aquatic life, including algae, crustaceans, and even fish. However, the freshwater quality criteria for the protection of aquatic life (ALFQC) of SMX are still unclear, as well as its ecological risk for surface waters in China. The [...] Read more.

Sulfamethoxazole (SMX) has adverse effects on aquatic life, including algae, crustaceans, and even fish. However, the freshwater quality criteria for the protection of aquatic life (ALFQC) of SMX are still unclear, as well as its ecological risk for surface waters in China. The acute and chronic toxicity data for SMX covered 10 and 11 species, respectively, which are widely distributed across China. The native species in China of Raphidocelis subcapitata displayed the most sensitivity after short-term exposure, whereas Lemna gibba showed the most sensitivity after long-term exposure to water contaminated with SMX. The short-term and long-term ALFQC of SMX were 2829 and 23.63 µg/L, respectively using the species sensitivity distribution in China. The 112 exposure data were collected from peer-reviewed publications and government reports published between 2006 and 2024, with the concentrations of SMX ranging from 0 to 0.531 µg/L in surface waters in China. A negligible ecological risk of SMX was observed in surface waters in China, confirmed by the low risk quotient (0~0.0225) and probability area overlap (0~0.005). This study provides a scientific basis for water quality standards and the ecological risk management for SMX in surface waters in China. Full article

(This article belongs to the Special Issue Environmental Criteria and Risk Control of Emerging Pollutants in Aquatic Environments)

► Show Figures

Figure 1

25 pages, 7474 KB

Open AccessEditor’s ChoiceArticle

A 10-Year Continuous Daily Simulation of Chloride Flux from a Suburban Watershed in Fairfax County, Virginia, USA

by Jeffrey G. Chanat and Christopher A. Custer

Water 2026, 18(1), 43; https://doi.org/10.3390/w18010043 - 23 Dec 2025

Cited by 2 | Viewed by 1136

Abstract

Increasing levels of chloride in surface water are associated with detrimental effects on water quality, aquatic ecosystems, infrastructure, and human health. Numerous mass-balance studies have inferred watershed transport processes by interpreting chloride inputs and outputs, but few represent internal dynamics explicitly. We constructed [...] Read more.

Increasing levels of chloride in surface water are associated with detrimental effects on water quality, aquatic ecosystems, infrastructure, and human health. Numerous mass-balance studies have inferred watershed transport processes by interpreting chloride inputs and outputs, but few represent internal dynamics explicitly. We constructed a coupled water/chloride mass balance model to gain insights into storage, residence time, and transport processes in a 10-km² urban watershed. The model, which operates over a 10-year period at a daily time scale, represents storage in a dynamic soil-moisture reservoir, quick-flow runoff from storm events, and slow-flow runoff that sustains streamflow in dry weather. The calibrated model accurately represented (a)the observed transition from a streamflow enrichment regime in cold months to a dilution regime in warmer months, (b) the observed tendency for late-summer concentrations to be higher after winters with heavy snowfall, and (c) a period-of-record downward trend in chloride concentration likely associated with a downward trend in annual snowfall. Estimated chloride inputs averaged 195 metric tons per year, while the average output was 270 metric tons per year. In contrast, estimated storage was only 107 metric tons. The estimated mean residence time in groundwater was 1.27 years. This short residence time indicates that efforts to reduce inputs will manifest as decreased concentrations in streamflow on a management-relevant time scale of several years. The coupled mass balance model yielded insights into internal watershed dynamics that would not be possible from simple input/output analysis; such models can be useful tools for gaining insight into small watershed hydrology and pollutant transport. Full article

(This article belongs to the Section Hydrology)

► Show Figures

Figure 1

18 pages, 5573 KB

Open AccessEditor’s ChoiceArticle

Assessing the Impact of Land Use and Landscape Patterns on Water Quality in Yilong Lake Basin (1993–2023)

by Yue Huang, Ronggui Wang, Jie Li and Yuhan Jiang

Water 2026, 18(1), 30; https://doi.org/10.3390/w18010030 - 22 Dec 2025

Cited by 3 | Viewed by 1782

Abstract

To investigate the influence of land use landscape patterns on lake water quality in the basin, the land use and water quality data of the Yilong Lake Basin from 1993 to 2023 were analyzed with a geographic information system, remote sensing, and landscape [...] Read more.

To investigate the influence of land use landscape patterns on lake water quality in the basin, the land use and water quality data of the Yilong Lake Basin from 1993 to 2023 were analyzed with a geographic information system, remote sensing, and landscape ecology methods in this research. The results show that (1) the land use landscape pattern and water quality of the Yilong Lake Basin had significant changes: the lake surface area, farmland, and shrubland declined, with grassland showing the sharpest decrease and serving as the main source of conversion to other land types, while forest land expanded and built-up land increased by five times. The landscape pattern analysis showed that the aggregation degree of the core habitat in the basin increased and the landscape had decreased patch density and increased heterogeneity. Regarding water quality, the concentrations of total nitrogen (TN), total phosphorus (TP), and ammonium nitrogen (NH₄⁺-N); permanganate index (I_Mn); and biochemical oxygen demand over 5 days (BOD₅) decreased. Furthermore, the concentration of dissolved oxygen (DO) increased and the concentration of chlorophyll-a (Chl-a) fluctuated for a long time but did not decrease dramatically at the end of the period compared with the beginning. In general, the eutrophication degree of Yilong Lake slightly decreased. (2) The landscape configuration strongly shaped the water quality: the redundancy analysis (RDA) revealed that the edge density (ED), landscape shape index (LSI), largest patch index (LPI), and patch density (PD) were negatively associated with the eutrophication of Yilong Lake (TN, TP, NH₄⁺-N, Chl-a), whereas the contagion index (CONTAG) was positively associated; the Shannon’s diversity index (SHDI) was closely linked with TN and I_Mn but negatively with DO; and the patch cohesion index (COHESION) had a low interpretation power for water quality changes. In particular, larger and more cohesive ecological patches supported a higher DO, while an increased patch density was linked to an elevated I_Mn and reduced DO. These results indicate that the restoration of key ecological patches and enhanced landscape cohesion helped to improve the water quality, whereas increased patch density and landscape heterogeneity negatively affected it. (3) In the past 30 years, the ecological management and protection work on Yilong Lake, such as returning farmland to forests and lakes, wetland restoration, and sewage pipe network construction, achieved remarkable results that were reflected in the change in the relationship between land use landscape pattern and water quality in the basin. However, human activities still affected the dynamic evolution of water quality: the expansion of built-up land increased the patch density, the reduction in shrubland and grassland weakened natural filtration, and the rapid urbanization process introduced more pollution sources. Although the increase in forest land helped to improve the water quality, the effect was not fully developed. These findings provide a scientific basis for the management and ecological restoration of plateau lakes. Strengthening land use planning, controlling urban expansion, and maintaining ecological patches are essential for sustaining water quality and promoting the coordinated development of the ecology and economy in the Yilong Lake Basin. Full article

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

► Show Figures

Figure 1

18 pages, 4075 KB

Open AccessEditor’s ChoiceArticle

An Attention-Based Hybrid CNN–Bidirectional LSTM Model for Classifying Chlorophyll-a Concentration in Coastal Waters

by Wara Taparhudee, Tanuspong Pokavanich, Manit Chansuparp, Kanokwan Khaodon, Saroj Rermdumri, Alongot Intarachart and Roongparit Jongjaraunsuk

Water 2026, 18(1), 33; https://doi.org/10.3390/w18010033 - 22 Dec 2025

Cited by 3 | Viewed by 4491

Abstract

Accurate monitoring of chlorophyll-a (Chl-a) is essential for managing coastal aquaculture, as Chl-a indicates phytoplankton biomass and water quality. This study developed a hybrid deep learning model integrating convolutional neural networks (CNN), bidirectional long short-term memory (BiLSTM), and an attention mechanism (Attention) to [...] Read more.

Accurate monitoring of chlorophyll-a (Chl-a) is essential for managing coastal aquaculture, as Chl-a indicates phytoplankton biomass and water quality. This study developed a hybrid deep learning model integrating convolutional neural networks (CNN), bidirectional long short-term memory (BiLSTM), and an attention mechanism (Attention) to classify Chl-a using hourly, water quality datasets collected from the GOT001 station in Si Racha Bay, Eastern Gulf of Thailand (2020–2024). A random forest (RF) identified sea surface temperature (SEATEMP), dew point temperature (DEWPOINT), and turbidity (TURB) as the most influential variables, accounting for over 90% of the accuracy. Chl-a concentrations were categorized into ecological groups (low, medium, and high) using quantile-based binning and K-means clustering to support operational classification. Model performance comparison showed that the CNN–BiLSTM model achieved the highest classification accuracy (81.3%), outperforming the CNN–LSTM model (59.7%). However, the addition of the Attention did not enhance predictive performance, likely due to the limited number of key predictive variables and their already high explanatory power. This study highlights the potential of CNN–BiLSTM as a near-real-time classification tool for Chl-a levels in highly variable coastal ecosystems, supporting aquaculture management, early warning of algal blooms or red tides, and water quality risk assessment in the Gulf of Thailand and comparable coastal regions. Full article

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

► Show Figures

Figure 1

24 pages, 1829 KB

Open AccessEditor’s ChoiceArticle

Integrating Multi-Index and Health Risk Assessment to Evaluate Drinking Water Quality in Central Romania

by Maria-Alexandra Resz, Olimpiu Blăjan, Dorina Călugăru, Augustin Crucean, Eniko Kovacs and Cecilia Roman

Water 2026, 18(1), 23; https://doi.org/10.3390/w18010023 - 21 Dec 2025

Cited by 1 | Viewed by 1575

Abstract

Chemical contaminants in drinking water represent a widespread threat to human health, making water quality monitoring an essential mitigation measure. This study aimed to assess the quality of drinking water by conducting comprehensive multi-year seasonal monitoring at seven distribution points in central Romania, [...] Read more.

Chemical contaminants in drinking water represent a widespread threat to human health, making water quality monitoring an essential mitigation measure. This study aimed to assess the quality of drinking water by conducting comprehensive multi-year seasonal monitoring at seven distribution points in central Romania, determining the spatial and temporal trends of relevant physical parameters (pH and electrical conductivity) and chemical contaminants (NO₂, NO₃, NH₄, Cl, and SO₄). The pollution degree was evaluated using the pollution index and the overall pollution assessment index. The principal component analysis attributed over 60% of water quality variance to NO₂, NO₃, and NH₄ pollution, linked to incomplete nitrification or external loading, such as agricultural practices. Additionally, a human health risk assessment was performed according to U.S. EPA guidelines, calculating the chronic daily intake, hazard quotient, and hazard index for nitrogen compounds via oral and dermal exposure pathways for both adults and children. The results showed significant seasonal fluctuations in nitrogen compounds and electrical conductivity. The pollution indices classified the water bodies across a spectrum from “light” to “significant” pollution degrees. The health risk assessment revealed that NO₃ was the primary risk driver, with hazard index values exceeding the threshold of one in specific locations and seasons, indicating potential adverse health effects, particularly for children. Full article

(This article belongs to the Special Issue New Technologies to Ensure Safe Drinking Water)

► Show Figures

Figure 1

22 pages, 1745 KB

Open AccessEditor’s ChoiceArticle

Governance on Point? An Assessment of the Permitting, Supervision and Enforcement Processes for Point Source Discharges in The Netherlands

by Arnoud Klok, Carel Dieperink and Tessa Rötscheid

Water 2026, 18(1), 27; https://doi.org/10.3390/w18010027 - 21 Dec 2025

Cited by 2 | Viewed by 1308

Abstract

The European Water Framework Directive (2000/60/EC) (WFD) aims to protect inland surface waters, transitional waters, coastal waters and groundwater. The overarching goal of the WFD is to reach a good aquatic ecosystem throughout all of Europe. With the aim of reaching this goal, [...] Read more.

The European Water Framework Directive (2000/60/EC) (WFD) aims to protect inland surface waters, transitional waters, coastal waters and groundwater. The overarching goal of the WFD is to reach a good aquatic ecosystem throughout all of Europe. With the aim of reaching this goal, article 4 of the WFD sets certain environmental objectives. According to article 4 of the WFD, all the surface water bodies falling under its scope should be of good chemical and ecological quality by the end of 2027, as most extension deadlines will expire. For artificial and heavily modified surface water bodies—which make up the vast majority in the Netherlands—the goal is not to achieve a good ecological status but instead a good ecological potential and a good chemical status. Point source discharges may have a major impact on water quality and in order to progress, a well-functioning permitting, supervision and enforcement (PSE) process is of considerable interest. So far little academic attention has been paid to the functioning and quality of the governance processes underlying the PSE process. This paper aims to reduce this knowledge gap by conducting a case study on Sitech, the wastewater company for the Chemelot industrial complex in Geleen in the province of Limburg, the Netherlands. We first elaborate on an assessment framework consisting of 18 good governance criteria. The framework is used to assess the permitting, supervision and enforcement process concerning the discharges of Chemelot industrial plant. Our assessment reveals that, despite significant improvements over the last decade, good governance in this case is only partially achieved. While in terms of accountability and resilience the process shows robust strengths, gaps are found in its inclusiveness, effectiveness and transparency. We conclude our paper with some reflections on the generalizability of our findings and some suggestions for further research and policymaking. Full article

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

► Show Figures

Figure 1

17 pages, 1377 KB

Open AccessEditor’s ChoiceArticle

Compound River Floods and Sea Storms: Forcings and Impacts

by Caterina Canale, Giuseppe Barbaro, Olga Petrucci, Francesca Minniti and Giandomenico Foti

Water 2026, 18(1), 14; https://doi.org/10.3390/w18010014 - 20 Dec 2025

Cited by 1 | Viewed by 1430

Abstract

Coastal areas are strategically significant from an ecological, anthropic, and economic point of view, but they are also susceptible to forces causing inundations. Multiple forcings occurring in close succession in space and time amplify the effects of a single force and form a [...] Read more.

Coastal areas are strategically significant from an ecological, anthropic, and economic point of view, but they are also susceptible to forces causing inundations. Multiple forcings occurring in close succession in space and time amplify the effects of a single force and form a compound event. An example is an atmospheric disturbance that extends from the sea to the mainland, causing a sea storm and a river flood due to heavy rainfall. This condition can occur in geomorphological contexts where the sea and mountains are close to each other, and the river basins are small. Most research on compound events focuses on extreme events; detailed studies of compound events not associated with extreme events and generated by non-exceptional atmospheric disturbances are scarce. Furthermore, there are very few detailed studies focusing solely on compound river floods and sea storms. Consequently, this paper is focused on compound river floods and sea storms generated by atmospheric disturbances regardless of their exceptional or non-typical typology. This analysis includes their forcings, correlation, and effects and is carried out in Calabria, a region of Southern Italy that represents an interesting case study due to its geomorphological, climatic, and hydrological peculiarities, which favor the formation of compound events, and, due to the considerable anthropization of its coastal territories, increases their risk. The main findings concern confirming that the existence of this compound event between river floods and sea storms is generated by the same atmospheric disturbance, the geomorphological conditions under which it occurs, and the main driving forces behind it. Therefore, this study is only the first step in a more in-depth analysis that will also examine the quantitative aspects of these phenomena. This analysis is essential for the planning and management of coastal areas subject to compound events and for ensuring effective mitigation measures. Full article

(This article belongs to the Section Hydrology)

► Show Figures

Figure 1

25 pages, 12169 KB

Open AccessEditor’s ChoiceArticle

Development of XAI-Based Explainable Planning Management for Chl-a Reduction

by Jong Gu Jeong, Yong Min Ryu and Eui Hoon Lee

Water 2026, 18(1), 7; https://doi.org/10.3390/w18010007 - 19 Dec 2025

Cited by 2 | Viewed by 1210

Abstract

This study presents an explainable artificial intelligence (XAI)-based explainable planning management (EPM) framework designed to provide interpretable prediction-driven insights for water quality management. Although deep learning models such as the multi-layer perceptron (MLP) effectively predict water quality indicators, they have limited interpretability and [...] Read more.

This study presents an explainable artificial intelligence (XAI)-based explainable planning management (EPM) framework designed to provide interpretable prediction-driven insights for water quality management. Although deep learning models such as the multi-layer perceptron (MLP) effectively predict water quality indicators, they have limited interpretability and practical use. To address this limitation, Shapley additive explanations (SHAP) were applied to quantify each input feature’s contribution to model-predicted chlorophyll-a (Chl-a) values and to support the construction of scenario-based analyses. The proposed framework was applied at the Dasan water quality observation station in the Nakdong river basin, Republic of Korea. Daily water quality data from 2014 to 2023 were used for model training, and 2024 data were used for prediction. The model excluding turbidity achieved the lowest root mean squared error (RMSE) of 7.3922. Scenario analyses were performed by varying Chl-a(t−1) and major variables in 10% increments, guided by influence identified through SHAP analysis. Results indicated that pH, which had the highest Shapley value excluding Chl-a(t−1), was the most influential variable, reducing algal bloom warning occurrences by up to 34%. These results demonstrate that the proposed EPM framework enhances interpretability and supports the exploration of prediction-based planning strategies, without implying causal or mechanistic relationships among water quality variables. Full article

(This article belongs to the Special Issue Algae Distribution, Risk, and Prediction)

► Show Figures

Figure 1

15 pages, 1819 KB

Open AccessEditor’s ChoiceArticle

Application of a Parsimonious Phosphorus Model (SimplyP) to Two Hydrologically Contrasting Agricultural Catchments

by Daniel Hawtree, Per-Erik Mellander, Russell Adams, Golnaz Ezzati, Leah Jackson-Blake, Ognjen Zurovec, Magnus Norling and Jason Galloway

Water 2026, 18(1), 6; https://doi.org/10.3390/w18010006 - 19 Dec 2025

Cited by 1 | Viewed by 1034

Abstract

Understanding how water-quality models perform across different hydrological and biogeochemical contexts is essential for managing nutrient losses in agricultural catchments. This study evaluated SimplyP, a parsimonious phosphorus model, adapted to better represent Irish agricultural catchments and implemented within the flexible Mobius2 framework. Long-term, [...] Read more.

Understanding how water-quality models perform across different hydrological and biogeochemical contexts is essential for managing nutrient losses in agricultural catchments. This study evaluated SimplyP, a parsimonious phosphorus model, adapted to better represent Irish agricultural catchments and implemented within the flexible Mobius2 framework. Long-term, high-frequency monitoring data from the Agricultural Catchments Programme (ACP) were used for two sites: Ballycanew, a grassland catchment dominated by surface runoff, and Castledockrell, an arable, groundwater-driven catchment. Model calibration and validation were performed for streamflow (Q), suspended sediment (SS), and multiple phosphorus (P) fractions, with performance assessed using Kling–Gupta efficiency (KGE). In Ballycanew, the model reproduced Q, SS, and total P load well, with weaker agreement for total reactive phosphorus (TRP), likely reflecting unaccounted point sources during low flows. In Castledockrell, performance was moderate for Q and SS, but TRP and other P fractions were not adequately captured, highlighting the need for more detailed representation of subsurface P pathways in groundwater-dominated systems. Overall, SimplyP is well-suited to surface-runoff-dominated catchments with conventional phosphorus mobilisation. Its flexible implementation in Mobius2 allows relatively straightforward modifications, such as including groundwater-mediated P processes, to extend applicability to more complex systems. High-resolution ACP datasets were crucial for identifying model strengths and limitations, supporting refinement for improved nutrient management across diverse agricultural landscapes. Full article

(This article belongs to the Special Issue New Technologies for Hydrological Forecasting and Modeling)

► Show Figures

Figure 1

22 pages, 4565 KB

Open AccessEditor’s ChoiceArticle

Removal of Cr(VI) from an Aqueous Solution via a Metal Organic Framework (Ce-MOF-808)

by Hongfei Zhang, Ming Zou, Haixin Zhang, Naoto Miyamoto and Naoki Kano

Water 2025, 17(24), 3594; https://doi.org/10.3390/w17243594 - 18 Dec 2025

Cited by 3 | Viewed by 1587

Abstract

Hexavalent chromium (Cr(VI)) is a carcinogenic and highly mobile pollutant in aquatic environments. In this study, three cerium-based metal–organic frameworks (Ce-UiO-66, Ce-UiO-66-NO₂, and Ce-MOF-808) were synthesized and evaluated for their ability to remove Cr(VI) from aqueous solutions. Among the frameworks studied, [...] Read more.

Hexavalent chromium (Cr(VI)) is a carcinogenic and highly mobile pollutant in aquatic environments. In this study, three cerium-based metal–organic frameworks (Ce-UiO-66, Ce-UiO-66-NO₂, and Ce-MOF-808) were synthesized and evaluated for their ability to remove Cr(VI) from aqueous solutions. Among the frameworks studied, Ce-MOF-808 exhibited the highest adsorption capacity and was selected for detailed investigation. To elucidate its structure and adsorption behavior, Ce-MOF-808 was characterized using XRD, FT-IR, SEM-EDS, TG-DTA, XPS, and Zeta potential analyses. The zeta potential results showed that the adsorbent surface remained positively charged in the pH range of 2.8–8.6, enabling electrostatic attraction toward anionic chromate species. XPS further revealed valence transitions between Ce³⁺/Ce⁴⁺ and Cr(VI)/Cr(III), demonstrating the occurrence of partial redox transformation during adsorption. Batch experiments showed that the adsorption was strongly pH-dependent and favored acidic conditions (pH 2). The kinetics followed the pseudo-second-order model, whereas the isotherm data were better described by the Langmuir model, yielding a maximum adsorption capacity of 42.74 mg/g. Thermodynamic analysis indicated a spontaneous and exothermic process. Moreover, Ce-MOF-808 maintained high Cr(VI) uptake in real water samples, demonstrating its environmental applicability. Overall, Ce-MOF-808 is a promising redox-active adsorbent for efficient Cr(VI) removal in water treatment applications. Full article

(This article belongs to the Special Issue Water Quality Engineering and Wastewater Treatment, 4th Edition)

► Show Figures

Figure 1

20 pages, 8586 KB

Open AccessEditor’s ChoiceArticle

Multi-Objective Optimization for Irrigation Canal Water Allocation and Intelligent Gate Control Under Water Supply Uncertainty

by Qingtong Cai, Xianghui Xu, Mo Li, Xingru Ye, Wuyuan Liu, Hongda Lian and Yan Zhou

Water 2025, 17(24), 3585; https://doi.org/10.3390/w17243585 - 17 Dec 2025

Cited by 4 | Viewed by 1330

Abstract

Open-channel irrigation systems often face constraints due to water supply uncertainty and insufficient gate control precision. This study proposes an integrated framework for canal water allocation and gate control that combines interval-based uncertainty analysis with intelligent optimization to address these challenges. First, we [...] Read more.

Open-channel irrigation systems often face constraints due to water supply uncertainty and insufficient gate control precision. This study proposes an integrated framework for canal water allocation and gate control that combines interval-based uncertainty analysis with intelligent optimization to address these challenges. First, we predict the inflow process using an Auto-Regressive Integrated Moving Average (ARIMA) model and quantify the range of water supply uncertainty through Maximum Likelihood Estimation (MLE). Based on these results, we formulate a bi-objective optimization model to minimize both main canal flow fluctuations and canal network seepage losses. We solve the model using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to obtain Pareto-optimal water allocation schemes under uncertain inflow conditions. This study also designs a Fuzzy Proportional–Integral–Derivative (Fuzzy PID) controller. We adaptively tune its parameters using the Particle Swarm Optimization (PSO) algorithm, which enhances the dynamic response and operational stability of open-channel gate control. We apply this framework to the Chahayang irrigation district. The results show that total canal seepage decreases by 1.21 × 10⁷ m³, accounting for 3.9% of the district’s annual water supply, and the irrigation cycle is shortened from 45 days to 40.54 days, improving efficiency by 9.91%. Compared with conventional PID control, the PSO-optimized Fuzzy PID controller reduces overshoot by 4.84%, and shortens regulation time by 39.51%. These findings indicate that the proposed method can significantly improve irrigation water allocation efficiency and gate control performance under uncertain and variable water supply conditions. Full article

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

► Show Figures

Figure 1

18 pages, 4452 KB

Open AccessEditor’s ChoiceArticle

Identification of Nitrate Sources in the Upper Reaches of Xin’an River Basin Based on the MixSIAR Model

by Benjie Luan, Ai Wang, Zhiguo Huo, Xuqing Lin and Man Zhang

Water 2025, 17(24), 3584; https://doi.org/10.3390/w17243584 - 17 Dec 2025

Cited by 3 | Viewed by 1216

Abstract

The upper Xin’an River basin serves as a critical ecological barrier and water-conservation area for the Yangtze River Delta. However, with rapid economic development, nitrogen pollution in the surface waters of this region has become increasingly pronounced. This study analyzed river water samples [...] Read more.

The upper Xin’an River basin serves as a critical ecological barrier and water-conservation area for the Yangtze River Delta. However, with rapid economic development, nitrogen pollution in the surface waters of this region has become increasingly pronounced. This study analyzed river water samples collected on four occasions from the upper Xin’an River basin for ammonium (NH₄⁺–N), nitrate-nitrogen (NO₃⁻–N), total nitrogen (TN), and nitrate isotopic (δ¹⁵N–NO₃⁻ and δ¹⁸O–NO₃⁻). The sources of nitrate (NO₃⁻) were apportioned using the MixSIAR stable-isotope mixing model, and the spatial distribution of these sources across the basin was characterized. Across the four sampling rounds, the mean TN concentration exceeded 1.3 mg/L, with NO₃⁻–N accounting for over 45% of TN, indicating that nitrate was the dominant inorganic nitrogen species. The δ¹⁵N–NO₃⁻ values ranged from 2.17‰ to 13.0‰, with mean values following the order summer > winter > autumn > spring. The δ¹⁸O–NO₃⁻ values varied from −5.20‰ to −3.48‰, and the average value showed a completely opposite seasonal variation pattern to that of δ¹⁵N–NO₃⁻. Process-based analysis of nitrogen transformations revealed that nitrification predominates during nitrate transport and transformation, whereas denitrification is comparatively weak. MixSIAR-based estimates indicate marked seasonal differences in the source composition of nitrate pollution in the upper Xin’an River basin; NO₃⁻ derives primarily from soil nitrogen (SN) and livestock/sewage manure nitrogen (LSN). LSN was the dominant contributor in spring and summer (49.2% and 59.9%, respectively). SN dominated in autumn (49.2%) and winter (54.1%). Fertilizer nitrogen (FN) contributed more during summer and autumn, when fertilization is concentrated and rainfall is higher. Atmospheric deposition (AN) contributed approximately 1% across all seasons and was thus considered negligible. These findings provide a scientific basis for source control of nitrogen pollution and water-quality management in the upper Xin’an River. Full article

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

► Show Figures

Figure 1

21 pages, 2101 KB

Open AccessEditor’s ChoiceArticle

Probabilistic Prediction of Local Scour at Bridge Piers with Interpretable Machine Learning

by Jaemyeong Choi, Jongyeong Kim, Soonchul Kwon and Taeyoon Kim

Water 2025, 17(24), 3574; https://doi.org/10.3390/w17243574 - 16 Dec 2025

Cited by 8 | Viewed by 1174

Abstract

Local pier scour remains one of the leading causes of bridge failure, calling for predictions that are both accurate and uncertainty-aware. This study develops an interpretable data-driven framework that couples CatBoost (Categorial Gradient Boosting) for deterministic point prediction with NGBoost (Natural Gradient Boosting) [...] Read more.

Local pier scour remains one of the leading causes of bridge failure, calling for predictions that are both accurate and uncertainty-aware. This study develops an interpretable data-driven framework that couples CatBoost (Categorial Gradient Boosting) for deterministic point prediction with NGBoost (Natural Gradient Boosting) for probabilistic prediction. Both models are trained on a laboratory dataset of 552 measurements of local scour at bridge piers using non-dimensional inputs (y/b, V/V_c, b/d₅₀, Fr). Model performance was quantitatively evaluated using standard regression metrics, and interpretability was provided through SHAP (Shapley Additive Explanations) analysis. Monte Carlo–based reliability analysis linked the predicted scour depths to a reliability index β and exceedance probability through a simple multiplicative correction factor. On the held-out test set, CatBoost offers slightly higher point-prediction accuracy, while NGBoost yields well-calibrated prediction intervals with empirical coverages close to the nominal 68% and 95% levels. This framework delivers accurate, interpretable, and uncertainty-aware scour estimates for target-reliability, risk-informed bridge design. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

24 pages, 16009 KB

Open AccessEditor’s ChoiceArticle

Coastal Ecosystem Services in Urbanizing Deltas: Spatial Heterogeneity, Interactions and Driving Mechanism for China’s Greater Bay Area

by Zhenyu Wang, Can Liang, Xinyue Song, Chen Yang and Miaomiao Xie

Water 2025, 17(24), 3566; https://doi.org/10.3390/w17243566 - 16 Dec 2025

Cited by 3 | Viewed by 1168

Abstract

As critical ecosystems, coastal zones necessitate the identification of their ecosystem service values, trade-off/synergy patterns, spatiotemporal evolution, and driving factors to inform scientific decision-making for sustainable ecosystem management. This study selected the coastal zone of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as [...] Read more.

As critical ecosystems, coastal zones necessitate the identification of their ecosystem service values, trade-off/synergy patterns, spatiotemporal evolution, and driving factors to inform scientific decision-making for sustainable ecosystem management. This study selected the coastal zone of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as the research region. By incorporating land-use types such as mangroves, tidal flats, and aquaculture areas, we analyzed land-use changes in 1990, 2000, 2010, and 2020. The InVEST model was employed to quantify six key ecosystem services (ESs): annual water yield, urban stormwater retention, urban flood risk mitigation, soil conservation, coastal blue carbon storage, and habitat quality, while spatial correlations among them were examined. Furthermore, Spearman’s rank correlation coefficient was used to assess trade-offs and synergies between ecosystem services, and redundancy analysis (RDA) combined with the geographically and temporally weighted regression (GTWR) model were applied to identify driving factors and their spatial heterogeneity. The results indicate that: (1) Cultivated land, forest land, impervious surfaces, and water bodies exhibited the most significant changes over the 30-year period; (2) Synergies predominated among most ecosystem services, whereas habitat quality showed trade-offs with others; (3) Among natural drivers, the normalized difference vegetation index (NDVI, positive effect) and evapotranspiration were critical factors. The proportion of impervious surfaces served as a key land-use change driver, and the nighttime light index emerged as a primary socioeconomic factor (negative effect). The impacts of drivers on ecosystem services displayed notable spatial heterogeneity. These findings provide scientific support for managing the supply-demand balance of coastal ecosystem services, rational land development, and sustainable development. Full article

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

► Show Figures

Figure 1

16 pages, 5009 KB

Open AccessEditor’s ChoiceArticle

Groundwater Storage Changes Derived from GRACE-FO Using In Situ Data for Practical Management

by Hongbo Liu, Jianchong Sun, Litang Hu, Shinan Tang, Fei Chen, Junchao Zhang and Zhenyuan Zhu

Water 2025, 17(24), 3572; https://doi.org/10.3390/w17243572 - 16 Dec 2025

Cited by 2 | Viewed by 1328

Abstract

The ongoing global decline in groundwater levels poses significant challenges for sustainable water management. Satellite gravity missions, such as the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), provide valuable estimates of groundwater storage changes at regional scales. However, the relatively coarse spatial resolution [...] Read more.

The ongoing global decline in groundwater levels poses significant challenges for sustainable water management. Satellite gravity missions, such as the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), provide valuable estimates of groundwater storage changes at regional scales. However, the relatively coarse spatial resolution of these satellite data limits their direct applicability to local groundwater management. In this study, we address this limitation for China by analyzing groundwater monitoring data from 108 cities with shallow groundwater use and 37 cities with deep groundwater use from the period 2019–2022, integrating in situ groundwater level records, official monitoring reports, monthly dynamic data, and GRACE-FO-derived groundwater storage estimates. Our findings reveal rapid groundwater depletion in northern China, especially in Xinjiang and Hebei Provinces. Fluctuations in shallow groundwater levels in Beijing and Jiangsu are closely related to precipitation variability. For deep aquifer regions, GRACE-FO-derived groundwater storage changes show a moderate Pearson correlation coefficient of 0.45 and groundwater level variations. Regional analysis for 2019–2021 in the Northeast Plain and the Huang–Huai–Hai Basin indicates better agreement between satellite-derived storage and groundwater levels, with a Pearson correlation coefficient of 0.58 in the Huang–Huai–Hai Basin. Groundwater level dynamics are strongly influenced by both precipitation and pumping, with an approximate three-month lag between precipitation events and groundwater storage responses. Overall, satellite gravity data are suitable for use in regional groundwater assessment and could serve as valuable indicators in areas with intensive deep groundwater exploitation. To enable fine-scale groundwater management, future work should focus on improving the spatial resolution through downscaling and other advanced techniques. Full article

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

► Show Figures

Figure 1

19 pages, 5987 KB

Open AccessEditor’s ChoiceArticle

Mesozooplankton Community Structure and Indicator Species in Relation to Seasonal Hydrography in the Yellow Sea and Northern East China Sea

by Garam Kim, Hyung-Ku Kang and Dong Han Choi

Water 2025, 17(24), 3547; https://doi.org/10.3390/w17243547 - 15 Dec 2025

Cited by 2 | Viewed by 813

Abstract

This study investigated variation in mesozooplankton community structure and indicator species in the Yellow Sea and northern East China Sea, based on four surveys conducted at different times of year. Total mesozooplankton abundance ranged from 1063 to 4515 ind. m⁻³, and [...] Read more.

This study investigated variation in mesozooplankton community structure and indicator species in the Yellow Sea and northern East China Sea, based on four surveys conducted at different times of year. Total mesozooplankton abundance ranged from 1063 to 4515 ind. m⁻³, and dry weight ranged from 23.3 to 44.6 mg m⁻³, with higher values observed in May and August compared to October and January. Redundancy analysis explained a modest fraction of the variation in community structure (17.6% in total; Axis 1: 10.5%, Axis 2: 4.6%), with temperature, salinity, and chlorophyll a jointly contributing to the observed gradients. Cluster and indicator species analyses delineated three ecologically distinct regions: (1) a neritic coastal area dominated by coastal copepods and meroplankton; (2) a cold-water region associated with the Yellow Sea Bottom Cold Water (YSBCW); and (3) a warm offshore region influenced by the Jeju and Yellow Sea Warm Currents. Oithona atlantica was consistently linked to the YSBCW, suggesting its potential as a biological indicator of cold-water mass, whereas Clausocalanus minor was confined to warm offshore waters and reflected the seasonal northward expansion of warm currents. These findings demonstrate a clear coupling between mesozooplankton community dynamics and hydrographic conditions during the survey periods. Full article

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

► Show Figures

Figure 1

16 pages, 1829 KB

Open AccessEditor’s ChoiceArticle

Environmental Sustainability of Nanobubble Watering Through Life-Cycle Evidence and Eco-Innovation for Circular Farming Systems

by Yeganeh Arablousabet, Bahman Peyravi and Arvydas Povilaitis

Water 2025, 17(24), 3543; https://doi.org/10.3390/w17243543 - 14 Dec 2025

Cited by 3 | Viewed by 1206

Abstract

Nanobubble-saturated water (NBSW) is widely seen as a potential innovation for sustainable agriculture; however, its overall environmental impact still requires clarification. This study examined the sustainability performance of NBSW using laboratory experiments, a life-cycle assessment (LCA), and an expert-based feasibility evaluation. Air and [...] Read more.

Nanobubble-saturated water (NBSW) is widely seen as a potential innovation for sustainable agriculture; however, its overall environmental impact still requires clarification. This study examined the sustainability performance of NBSW using laboratory experiments, a life-cycle assessment (LCA), and an expert-based feasibility evaluation. Air and oxygen nanobubble (ONB) watering were applied to silty clay loam and sandy loam soils, and environmental impacts were assessed using ILCD 2011 midpoint indicators. The results revealed that the electricity required for NB generation was the most significant contributor to the impacts across all categories, while material and nutrient inputs had only a minor impact. Air-NB and ONB treatments demonstrated similar life-cycle profiles because of their comparable energy demand. Conventional watering did not involve electricity use but increased nitrate leaching in sandy soil, leading to the possibility of eutrophication. Expert assessments indicated that future adoption of NBSW depends mainly on reducing energy consumption and improving operational reliability and cost efficiency. When combined with low-carbon energy and efficiency improvements, NBSW may contribute to reducing nutrient losses and enhancing resource efficiency in watering. These findings show that NB technology has potential as an eco-innovation, but more study is needed before it can be considered a viable circular-agriculture solution. Full article

(This article belongs to the Special Issue Water and Soil Pollution from Agriculture: Mechanisms, Assessments and Mitigation Strategies)

► Show Figures

Figure 1

22 pages, 7205 KB

Open AccessEditor’s ChoiceArticle

Integrating UAV-LiDAR and Field Experiments to Survey Soil Erosion Drivers in Citrus Orchards Using an Exploratory Machine Learning Approach

by Jesús Rodrigo-Comino, Laura Cambronero-Ruiz, Lucía Moreno-Cuenca, Jesús González-Vivar, María Teresa González-Moreno and Víctor Rodríguez-Galiano

Water 2025, 17(24), 3541; https://doi.org/10.3390/w17243541 - 14 Dec 2025

Cited by 2 | Viewed by 1044

Abstract

Citrus orchards are especially vulnerable owing to low inter-row vegetation cover, and frequent tillage. Here, we combine controlled field experiments with proximal remote sensing–derived geomorphometric variables and machine learning (ML) to identify key factors of erosion in a Mediterranean climate citrus plantation located [...] Read more.

Citrus orchards are especially vulnerable owing to low inter-row vegetation cover, and frequent tillage. Here, we combine controlled field experiments with proximal remote sensing–derived geomorphometric variables and machine learning (ML) to identify key factors of erosion in a Mediterranean climate citrus plantation located close to Seville and the National Park of Doñana (Southern Spain) on Gleyic Regosols (clayic, arenic). We conducted rainfall simulations with 30 s sampling, measured infiltration (mini-disc infiltrometer), saturated hydraulic conductivity (Kfs; Guelph permeameter), compaction (penetrologger), and soil respiration (gas analyzer) at multiple points, and derived high resolution morphometric indices from proximal sensing (UAV-LiDAR). Linear models and Random Forests were trained to explain three responses: soil loss, sediment concentration (SC), and runoff. Results show that soil loss is most strongly associated with maximum compaction and Kfs (multiple regression: R² = 0.68; adjusted R² = 0.52; p = 0.063), while SC increases with surface compaction and exhibits weak relationships with topographic metrics. Runoff decreases with average infiltration, which is related to compaction (β = −4.83 ± 2.38; R² = 0.34; p = 0.077). Diagnostic checks indicate centered residuals with mild heteroscedasticity and a few high leverage observations. Random Forests captured part of the variance for soil loss (≈29%) but performed poorly for runoff, consistent with limited sample size and modest nonlinear signal. Morphometric analysis revealed gentle relief but pronounced convergent–divergent patterns that modulate hydrological connectivity. There were strong differences in the experiments conducted close to the trees and in the tractor trails. We conclude that compaction and near surface hydraulic properties are the most influential and measurable controls of erosion at plot scale and the UAV-LiDAR could not give us extra-insights. We highlight that integrating standardized field protocols with proximal morphometrics and ML can be the best method to prioritize a small set of explanatory variables, helping to reduce experimental effort while maintaining explanatory power. Full article

(This article belongs to the Special Issue Soil Erosion Measurement Techniques and Field Experiments, 2nd Edition)

► Show Figures

Figure 1

64 pages, 2249 KB

Open AccessEditor’s ChoiceReview

Towards a Structured Approach to Advance Sustainable Water Management in Higher Education Institutions: A Review

by Riccardo Boiocchi, Cosimo Peruzzi, Ramona Giurea and Elena Cristina Rada

Water 2025, 17(24), 3526; https://doi.org/10.3390/w17243526 - 12 Dec 2025

Cited by 6 | Viewed by 3721

Abstract

The aim of this paper is to investigate the measures adopted by higher education institutions (HEIs) for sustainable water management in university campuses. Rain and storm water harvesting and treatment, rain and storm water reuse, wastewater treatment and reuse and technologies for runoff [...] Read more.

The aim of this paper is to investigate the measures adopted by higher education institutions (HEIs) for sustainable water management in university campuses. Rain and storm water harvesting and treatment, rain and storm water reuse, wastewater treatment and reuse and technologies for runoff reduction were found to be frequently undertaken. Sustainable approaches to water supply such as water-efficient appliances, irrigation algorithms and the use of drought-resistant plants have been adopted as well. In support, monitoring of consumed water and of rain and storm waters has been a widespread practice. Important considerations were given to the impact of the identified measures on campuses’ energy consumption and greenhouse gas emissions. Nature-based solutions, employment of renewable energies and sustainable disinfection methods are measures to prioritize. Some wastewater technologies may deserve priority in virtue of their positive contribution to circular economy. Drawbacks such as groundwater and soil contamination due to wastewater reuse and the release of pollutants from fertilized nature-based technologies were identified. Despite their variety, it must be noted that many of these measures have generally involved rather limited portions of campuses, taken more for demonstration or pilot/full-scale research purposes. Additional measures not identified in the current review—for instance the prevention of pollution from micropollutants and waste mismanagement—should be implemented to boost HEIs’ environmental sustainability. The findings of this review pave the way for a more structured implementation of water sustainability measures in university campuses. Full article

(This article belongs to the Special Issue Drawbacks, Limitations, Solutions and Perspectives of Water Reuse)

► Show Figures

Graphical abstract

24 pages, 14098 KB

Open AccessEditor’s ChoiceArticle

Enhanced Adsorption–Photocatalytic Degradation of the Congo Red Dye in the Presence of the MOF/Activated Carbon Composite Catalysts

by Marija Egerić, Djordje Petrović, Radojka Vujasin, Yi-nan Wu, Fengting Li, Pierre-Eymeric Janolin, Ljiljana Matović and Aleksandar Devečerski

Water 2025, 17(24), 3515; https://doi.org/10.3390/w17243515 - 12 Dec 2025

Cited by 11 | Viewed by 1601

Abstract

The extensive application of synthetic dyes in various industries and potential accidental uncontrolled discharge into natural water bodies have led to significant environmental challenges and a need for effective treatment. In this study, UiO-66 metal–organic framework/activated carbon (MOF/AC) composites were used to evaluate [...] Read more.

The extensive application of synthetic dyes in various industries and potential accidental uncontrolled discharge into natural water bodies have led to significant environmental challenges and a need for effective treatment. In this study, UiO-66 metal–organic framework/activated carbon (MOF/AC) composites were used to evaluate the photocatalytic degradation of Congo Red dye (CR) in aqueous solution under natural solar irradiation. The degradation efficiency of CR was determined using UV-Vis spectroscopy, while material characterization and additional insight into the reaction mechanism were obtained by XRD, FTIR, and Raman analysis. For a 50 ppm CR solution, within a 2 h reaction time, pure MOF achieved 57.2% and 26.3% degradation under solar irradiation and dark conditions, respectively, while the 75/25 MOF/AC composite reached 74% and 38.3% under the same conditions. These results confirm the synergistic interaction between MOF and AC, where AC acts as an electron sink, preventing charge recombination and enhancing photocatalytic activity. Chemisorption occurred simultaneously with photocatalytic degradation on the MOF surface. Reusability tests showed that pure MOF retained the highest stability over repeated cycles. Overall, the combination of MOF and AC enhances catalytic performance, which represents a sustainable approach for treating dye-contaminated wastewater under natural solar conditions. Full article

(This article belongs to the Special Issue Advanced Materials for the Catalytic Removal of Emerging Pollutants from Water)

► Show Figures

Figure 1

17 pages, 1332 KB

Open AccessEditor’s ChoiceArticle

Implementing the One Water Concept in Greece: Evidence from Case Studies and Policy Pathways

by Nektarios N. Kourgialas, Andreas N. Angelakis and George Tchobanoglous

Water 2025, 17(24), 3525; https://doi.org/10.3390/w17243525 - 12 Dec 2025

Cited by 2 | Viewed by 1222

Abstract

A prominent development in environmental engineering and water resource management is the growing adoption of the term “One Water,” which encompasses all categories of water. In practical terms, One Water Concept (OWC) suggests that some municipalities could benefit from combining their traditionally separate [...] Read more.

A prominent development in environmental engineering and water resource management is the growing adoption of the term “One Water,” which encompasses all categories of water. In practical terms, One Water Concept (OWC) suggests that some municipalities could benefit from combining their traditionally separate water supply and wastewater divisions into a single, unified department. This integration is believed to enable more strategic, efficient, and economically viable approaches to addressing future water challenges. The OWC promotes an integrated approach to water resource management, emphasizing the interconnectedness of water systems and the need for holistic governance. The focus of this paper is on an examination of the implementation of OWC in Greece based on an analysis of recent international case studies, and the identification of the methodological and epistemological challenges. Through critical engagement with current literature and policy frameworks, the study highlights the successes and obstacles in adopting OWC, offering insights into future directions for sustainable water management. The study identifies key challenges such as institutional fragmentation, insufficient reuse infrastructure, and fragmented policy frameworks, while also highlighting opportunities related to digital monitoring, stakeholder collaboration, and investment in green infrastructure. These findings underscore the need for coordinated strategies to advance the One Water approach in Greece. Full article

(This article belongs to the Special Issue Climate–Water Effects in Agriculture: Adaptation and Mitigation Approaches)

► Show Figures

Graphical abstract

19 pages, 672 KB

Open AccessEditor’s ChoiceArticle

An Improved Entropy Weight Method Mitigating Grade Distortion in Water Quality Assessment

by Qin Yan, Feng Yan, Lingping Xie, Jiang Huang, Rui Chen and Xinxin Liu

Water 2025, 17(24), 3508; https://doi.org/10.3390/w17243508 - 11 Dec 2025

Cited by 7 | Viewed by 1827

Abstract

The Entropy Weight Method (EWM) is a prevalent and objective technique for assigning weights in water quality assessment. However, engineering practice has shown that distortion phenomena occur in water quality assessment results based on the EWM. This study reveals EWM’s distortion in grade [...] Read more.

The Entropy Weight Method (EWM) is a prevalent and objective technique for assigning weights in water quality assessment. However, engineering practice has shown that distortion phenomena occur in water quality assessment results based on the EWM. This study reveals EWM’s distortion in grade discrimination via theory and case studies. To address this, we developed an improved entropy weight model (I-EWM) based on fuzzy variable set theory, which determines weights by incorporating both pollution degree and grade discrimination capacity. We quantify an indicator’s grade discrimination level and pollution degree using the fuzzy entropy and first-order moment of its average membership vector, respectively. A specific water quality assessment example was used to demonstrate the effectiveness of the I-EWM. The I-EWM significantly altered the weight allocation: the weights for COD_Mn, NH₃-N, and TP shifted from (0.687, 0.185, 0.127) to (0.191, 0.428, 0.381). When applied to the five monitoring points, the I-EWM produced markedly different results from the EWM. The water quality grades shifted from a pattern of (“Good”, “Good”, “Good”, “Good”, “Medium”) to a more conservative and realistic assessment of (“Medium”, “Medium”, “Poor”, “Poor”, “Poor”). Theoretical analysis demonstrates that the I-EWM provides more reasonable water quality assessments and effectively addresses the grade discrimination distortion inherent in the EWM. Full article

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

► Show Figures

Figure 1

23 pages, 783 KB

Open AccessEditor’s ChoiceReview

Bridging the Gap Between Model Assumptions and Realities in Leak Localization for Water Networks

by Rosario La Cognata, Stefania Piazza and Gabriele Freni

Water 2025, 17(24), 3502; https://doi.org/10.3390/w17243502 - 11 Dec 2025

Cited by 1 | Viewed by 1573

Abstract

Localising leaks in pressurised water distribution networks (WDNs) is crucial for reducing water loss but remains challenging because of model uncertainties and limited sensor data. Nevertheless, many state-of-the-art methods rely on idealised assumptions that are perfectly known, like time-invariant demands, noise-free pressure sensors, [...] Read more.

Localising leaks in pressurised water distribution networks (WDNs) is crucial for reducing water loss but remains challenging because of model uncertainties and limited sensor data. Nevertheless, many state-of-the-art methods rely on idealised assumptions that are perfectly known, like time-invariant demands, noise-free pressure sensors, a single, stationary leak, and a known leak-free baseline. These assumptions rarely hold in practice, creating a gap between expected performance and field reality. This article provides a comprehensive review of current leak localisation techniques based on sensor data and hydraulic or data-driven models. This study critically examines how recent studies have addressed these unrealistic assumptions. Advanced methods incorporate demand uncertainty and sensor noise into leak detection algorithms to improve robustness, estimate unknown demand variations using physics-informed machine learning, and employ Bayesian inference to locate multiple simultaneous leaks. The analysis indicates that accounting for such real-world complexities markedly improves localisation accuracy; for instance, even minor demand estimation errors or sensor noise can dramatically degrade performance if not addressed. Finally, bridging the gap between the models and reality is essential for the practical deployment of water utilities. Thus, this review recommends that future studies integrate uncertainty quantification, adaptive modelling, and enhanced sensing into leak localisation frameworks, thereby guiding the development of more resilient and field-ready leak management solutions. Full article

(This article belongs to the Special Issue Research on Water Supply Systems and on the Treatment and Recovery of Wastewater and Stormwater)

► Show Figures

Figure 1

36 pages, 2303 KB

Open AccessEditor’s ChoiceArticle

Season-Aware Ensemble Forecasting with Improved Arctic Puffin Optimization for Robust Daily Runoff Prediction Across Multiple Climate Zones

by Wenchuan Wang, Xutong Zhang, Qiqi Zeng and Dongmei Xu

Water 2025, 17(24), 3504; https://doi.org/10.3390/w17243504 - 11 Dec 2025

Cited by 1 | Viewed by 899

Abstract

Accurate daily runoff forecasting is essential for flood control and water resource management, yet existing models struggle with the seasonal non-stationarity and inter-basin variability of runoff sequences. This paper proposes a Season-Aware Ensemble Forecasting (SAEF) method that integrates SVM, LSSVM, LSTM, and BiLSTM [...] Read more.

Accurate daily runoff forecasting is essential for flood control and water resource management, yet existing models struggle with the seasonal non-stationarity and inter-basin variability of runoff sequences. This paper proposes a Season-Aware Ensemble Forecasting (SAEF) method that integrates SVM, LSSVM, LSTM, and BiLSTM models to leverage their complementary strengths in capturing nonlinear and non-stationary hydrological dynamics. SAEF employs a seasonal segmentation mechanism to divide annual runoff data into four seasons (spring, summer, autumn, winter), enhancing model responsiveness to seasonal hydrological drivers. An Improved Arctic Puffin Optimization (IAPO) algorithm optimizes the model weights, improving prediction accuracy. Beyond numerical gains, the framework also reflects seasonal runoff generation processes—such as rapid rainfall–runoff in wet seasons and baseflow contributions in dry periods—providing a physically interpretable perspective on runoff dynamics. The effectiveness of SAEF was validated through case studies in the Dongjiang Hydrological Station (China), the Elbe River (Germany), and the Quinebaug River basin (USA), using four performance metrics (MAE, RMSE, NSEC, KGE). Results indicate that SAEF achieves average Nash–Sutcliffe Efficiency Coefficient (NSEC) and Kling–Gupta efficiency (KGE) coefficients of over 0.92, and 0.90, respectively, significantly outperforming individual models (SVM, LSSVM, LSTM, BiLSTM) with RMSE reductions of up to 58.54%, 55.62%, 51.99%, and 48.14%. Overall, SAEF not only strengthens predictive accuracy across diverse climates but also advances hydrological understanding by linking data-driven ensembles with seasonal process mechanisms, thereby contributing a robust and interpretable tool for runoff forecasting. Full article

(This article belongs to the Section Hydrology)

► Show Figures

Figure 1

17 pages, 6882 KB

Open AccessEditor’s ChoiceArticle

Identifying Urban Pluvial Frequency Flooding Hotspots Using the Topographic Control Index and Remote Sensing Radar Images for Early Warning Systems

by Unique Bakhrel, Nicholas Brake, Mahdi Feizbahr, Yong Je Kim, Hossein Hariri Asli, Liv Haselbach and Slater J. Macon

Water 2025, 17(24), 3500; https://doi.org/10.3390/w17243500 - 10 Dec 2025

Cited by 2 | Viewed by 1032

Abstract

Identifying areas that frequently experience post-rainfall ponding is essential for effective flood mitigation and planning. This study integrates Sentinel-1 radar imagery and the Topographic Control Index (TCI) to identify 378 flood-prone urban depressions in Beaumont, Texas. Out of 159 major rainfall events, only [...] Read more.

Identifying areas that frequently experience post-rainfall ponding is essential for effective flood mitigation and planning. This study integrates Sentinel-1 radar imagery and the Topographic Control Index (TCI) to identify 378 flood-prone urban depressions in Beaumont, Texas. Out of 159 major rainfall events, only six had Sentinel-1 radar imagery acquired within six hours of peak rainfall, and these were used to generate the flood frequency map; the ground-based flood sensor data were used to verify that these selected events corresponded to actual peak rainfall and to validate radar-detected water pixels. Validation results showed 100% precision, 70.87% recall, an F1-score of 82.95%, and 71.32% overall accuracy. Approximately 84% of medium-to-high TCI depressions overlapped with Beaumont’s two-year inundation map, confirming a strong relationship between TCI and observed flooding. A total of 124 depressions retained significant water, and after excluding 25 engineered detention ponds, 99 natural depressions remained flood vulnerable. Among these, 74 depressions with medium or high TCI were identified as the highest-priority nuisance flooding hotspots. The results demonstrate that combining TCI with radar imagery provides a reliable and cost-effective approach for identifying areas prone to frequent urban ponding. This framework supports practical decision-making for drainage improvements, hotspot identification, and early-warning system development in urban flood-prone regions. Full article

(This article belongs to the Section Urban Water Management)

► Show Figures

Figure 1

31 pages, 5615 KB

Open AccessEditor’s ChoiceReview

Constructed Wetlands for Dairy and Livestock Wastewater Treatment: A Review

by Salvatore Barresi, Alessia Concetta Marzo and Mirco Milani

Water 2025, 17(24), 3492; https://doi.org/10.3390/w17243492 - 10 Dec 2025

Cited by 3 | Viewed by 2002

Abstract

Dairy and livestock farms produce considerable amounts of wastewater, which could pose an environmental risk if not properly treated and discharged. Conventional treatment plants can represent an inadequate and costly solution in terms of operation and maintenance, especially for small and medium-sized farms. [...] Read more.

Dairy and livestock farms produce considerable amounts of wastewater, which could pose an environmental risk if not properly treated and discharged. Conventional treatment plants can represent an inadequate and costly solution in terms of operation and maintenance, especially for small and medium-sized farms. Thus, a valid and sustainable alternative can be provided by constructed wetland (CW). This paper analyzed the use of CW systems at different scales to treat dairy wastewater (DWW) and livestock wastewater (LWW) all around the world over the last thirty years. This systematic review identified 50 case studies reported in 50 publications from 22 countries: 20 CW for LWW and 30 for DWW. Per each type of WW, the analysis reported and compared the following: CW layout, type of substrates, vegetations planted, design parameters, removal efficiencies and management aspects. Gravel and sand are the most common substrates used in CW to treat both types of WW. Regarding vegetation, Phragmites australis is the most commonly used species in CWs treating LWW, whereas Typha spp. are the most frequently used in CWs treating DWW. Hybrid CW showed the highest removal performance for all parameters reported. This review can improve knowledge on CW, offering a technical and practical overview of the status of CW for treating LWW and DWW. Full article

(This article belongs to the Special Issue Constructed Wetland Systems for Wastewater Treatment and Water Remediation)

► Show Figures

Figure 1

13 pages, 1315 KB

Open AccessEditor’s ChoiceArticle

Efficiency of a DAF System in Removing Organic Matter and Lipid Compounds from Municipal Effluent

by Luis R. Paredes-Quiroz, Hermógenes Ccasani-Dávalos, Dagnith L. Bejarano-Luján, Ruth M. Ccopa-Flores and Franklin Lozano

Water 2025, 17(24), 3474; https://doi.org/10.3390/w17243474 - 8 Dec 2025

Cited by 2 | Viewed by 3016

Abstract

Oil and grease (O&G) pollution in municipal effluents represents a critical environmental challenge. This study contributes a novel experimental assessment of how pressure and recirculation time influence oxygen transfer, microbubble generation, and pollutant removal in a pilot-scale DAF system, providing new insights into [...] Read more.

Oil and grease (O&G) pollution in municipal effluents represents a critical environmental challenge. This study contributes a novel experimental assessment of how pressure and recirculation time influence oxygen transfer, microbubble generation, and pollutant removal in a pilot-scale DAF system, providing new insights into process optimization for municipal wastewater treatment. This study evaluated the efficiency of a DAF system in removing organic pollutants and solids from municipal effluent by varying gauge pressure (1–5 bar) and recirculation time (1–20 min). The initial concentrations present in the effluent were 800 mg/L total solids (TS), 590 mg/L total suspended solids (TSS), 450 mg/L oil and grease (O&G), 360 mg/L biochemical oxygen demand (BOD₅), and 710 mg/L chemical oxygen demand (COD). The concentration of dissolved air (interpreted as dissolved oxygen supersaturation) reached 102.3 mg/L and removal efficiencies of 84.4% for O&G, 88.9% for BOD₅, 88.7% for COD, and 85% for TSS were achieved, while pH and dissolved solids (DS) remained stable. The saturation factor (f = 0.8) confirmed efficient oxygen-liquid transfer, attributed to the use of Raschig rings in the absorption column. The significance of this work lies in demonstrating that operating conditions directly enhance oxygen dissolution and flotation performance, highlighting an optimization pathway rarely reported for municipal effluents. The results demonstrate that DAF is a robust, stable, and energy-efficient technology capable of effectively removing organic and lipid loads from municipal effluent, providing a sustainable alternative for the pretreatment and reuse of urban wastewater. Full article

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

► Show Figures

Figure 1

17 pages, 1272 KB

Open AccessEditor’s ChoiceArticle

Unravelling Metabolic Pathways and Evaluating Process Performances in Anaerobic Digestion of Livestock Manures

by Hangbae Jun, Rahul Kadam, Sangyeol Jo and Jungyu Park

Water 2025, 17(24), 3464; https://doi.org/10.3390/w17243464 - 6 Dec 2025

Cited by 2 | Viewed by 1022

Abstract

Anaerobic digestion (AD) provides significant environmental benefits by converting livestock manures, such as cattle manure (CM) and pig manure (PM), into biogas and nutrient-rich digestate, supporting circular economy principles. However, challenges arise when feedstock overload disrupts microbial balance, leading to reduced methane (CH [...] Read more.

Anaerobic digestion (AD) provides significant environmental benefits by converting livestock manures, such as cattle manure (CM) and pig manure (PM), into biogas and nutrient-rich digestate, supporting circular economy principles. However, challenges arise when feedstock overload disrupts microbial balance, leading to reduced methane (CH₄) yields and process instability. This study examined the performance of AD using CM and PM with gradually increasing organic loading rates (OLR). At steady state, CH₄ yields were 120.32 mL-CH₄/g VS for CM and 229 mL-CH₄/g VS for PM. The lower yield for CM is attributed to its high cellulose and hemicellulose content, which exceeds 50% and is difficult to degrade. In contrast, PM showed more efficient carbohydrate degradation, resulting in higher CH₄ production. Key methanogens, including Methanocorpusculum, Methanosaeta, Methanosarcina, Methanobacterium, and Methanospirillum, were present in both reactors. Metagenomic analysis revealed that pathways for degrading cellulose and hemicellulose were poorly represented in CM, while PM exhibited enhanced total volatile fatty acid metabolism. This study offers valuable insights into the metabolic pathways associated with CM and PM in anaerobic digestion. Full article

(This article belongs to the Special Issue Advances in Biological Technologies for Drinking and Wastewater Treatment)

► Show Figures

Figure 1

19 pages, 6163 KB

Open AccessEditor’s ChoiceArticle

Analysis of Application of Design Standards for Future Climate Change Adaptive Agricultural Reservoirs Using Cluster Analysis

by Dong-Hyuk Joo, Ra Na, Hayoung Kim, Seung-Hwan Yoo and Sang-Hyun Lee

Water 2025, 17(24), 3463; https://doi.org/10.3390/w17243463 - 5 Dec 2025

Cited by 1 | Viewed by 898

Abstract

This study aimed to assess the impact and vulnerability of climate change by classifying 26 clusters of meteorologically homogeneous regions. To determine the optimal clustering method, both K-means and Gaussian Mixture Model (GMM) clustering were analyzed using the effective storage capacity to watershed [...] Read more.

This study aimed to assess the impact and vulnerability of climate change by classifying 26 clusters of meteorologically homogeneous regions. To determine the optimal clustering method, both K-means and Gaussian Mixture Model (GMM) clustering were analyzed using the effective storage capacity to watershed area ratio. The optimal number of clusters was derived based on several evaluation metrics, including the Silhouette Score, Calinski-Harabasz Index, Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). Ultimately, GMM clustering was identified as the optimal method, with the best clustering results obtained at k = 4 for an effective storage capacity of 100,000 to 400,000 tons and k = 5 for an effective storage capacity of 400,000 to 10,000,000 tons. Additionally, standard reservoirs applicable to agricultural production infrastructure design standards were identified based on homogeneous weather region clusters, the optimal clustering method, and centroid results. The findings of this study can serve as fundamental data for the development and revision of design standards, contributing to more climate-resilient agricultural infrastructure. Full article

► Show Figures

Figure 1

25 pages, 3145 KB

Open AccessEditor’s ChoiceArticle

Modeling the Effect of Nature-Based Solutions in Reducing Soil Erosion with InVEST ^® SDR: The Carapelle Case Study

by Ossama M. M. Abdelwahab, Giovanni Francesco Ricci, Addolorata Maria Netti, Anna Maria De Girolamo and Francesco Gentile

Water 2025, 17(24), 3451; https://doi.org/10.3390/w17243451 - 5 Dec 2025

Cited by 3 | Viewed by 1833

Abstract

Soil erosion threatens agricultural sustainability and water quality in Mediterranean watersheds, necessitating effective Nature-Based Solutions (NBSs) for mitigation. This study applied the InVEST Sediment Delivery Ratio (SDR) model to assess erosion patterns and evaluate NBS effectiveness in the Carapelle watershed (506 km² [...] Read more.

Soil erosion threatens agricultural sustainability and water quality in Mediterranean watersheds, necessitating effective Nature-Based Solutions (NBSs) for mitigation. This study applied the InVEST Sediment Delivery Ratio (SDR) model to assess erosion patterns and evaluate NBS effectiveness in the Carapelle watershed (506 km²). The SDR model was calibrated and validated using measured sediment yield data from 2007 and 2008. Model validation achieved a 4.3% deviation from observed data after parameter optimization. Four NBS scenarios were evaluated: contour farming (CF), no-tillage (NT), cover crops (CCs), and combined practices (Comb). Baseline soil loss varied from 2.43 t ha⁻¹ yr⁻¹ (2007) to 3.88 t ha⁻¹ yr⁻¹ (2008), with sediment export ranging from 0.86 to 1.30 t ha⁻¹ yr⁻¹. NT demonstrated the highest individual effectiveness, reducing sediment export by 72.2% on average. The Comb approach (NT + CCs) achieved a superior performance with a 75.9% sediment export reduction and a 70.5% soil loss reduction. Spatial analysis revealed that high-retention zones were concentrated in forest and shrubland, while agricultural zones showed the greatest potential for NBS implementation. NBSs significantly enhance sediment retention services in Mediterranean agricultural watersheds. The InVEST SDR model proves to be effective for watershed-scale assessment. The results provide actionable guidance for sustainable land management and soil conservation policy in erosion-prone Mediterranean environments. Full article

(This article belongs to the Special Issue Soil Erosion and Sedimentation by Water)

► Show Figures

Figure 1

17 pages, 3818 KB

Open AccessEditor’s ChoiceArticle

Water and Soil Salinization Mechanism in the Arid Barkol Inland Basin in NW China

by Ziyue Wang, Chaoyao Zan, Yajing Zhao, Bo Xu, Rui Long, Xiaoyong Wang, Jun Zhang and Tianming Huang

Water 2025, 17(24), 3462; https://doi.org/10.3390/w17243462 - 5 Dec 2025

Cited by 2 | Viewed by 1521

Abstract

Identifying the dominant mechanisms of water and soil salinization in arid and semi-arid endorheic basins is fundamental for our understanding of basin-scale water–salt balance and supports water resources management. In many inland basins, mineral dissolution, evaporation, and transpiration govern salinization, but disentangling these [...] Read more.

Identifying the dominant mechanisms of water and soil salinization in arid and semi-arid endorheic basins is fundamental for our understanding of basin-scale water–salt balance and supports water resources management. In many inland basins, mineral dissolution, evaporation, and transpiration govern salinization, but disentangling these processes remains difficult. Using the Barkol Basin in northwestern China as a representative endorheic system, we sampled waters and soils along a transect from the mountain front through alluvial fan springs and rivers to the terminal lake. We integrated δ¹⁸O–δ²H with hydrochemical analyses, employing deuterium excess (d-excess) to partition salinity sources and quantify contributions. The results showed that mineral dissolution predominated, contributing 65.8–81.8% of groundwater salinity in alluvial fan settings and ~99.7% in the terminal lake, whereas direct evapoconcentration was minor (springs and rivers ≤ 4%; lake ≤ 0.2%). Water chemistry types evolved from Ca-HCO₃ in mountainous runoff, to Ca·Na-HCO₃·SO₄ in groundwater and groundwater-fed rivers, and finally to Na-SO₄·Cl in the terminal lake. The soil profiles showed that groundwater flow and vadose-zone water–salt transport control spatial patterns: surface salinity rises from basin margins (<1 mg/g) to the lakeshore and is extremely high near the lake (23.85–244.77 mg/g). In spring discharge belts and downstream wetlands, the sustained evapotranspiration of groundwater-supported soil moisture drives surface salt accumulation, making lakeshores and wetlands into terminal sinks. The d-excess-based method can robustly separate the salinization processes despite its initial isotopic variability. Full article

(This article belongs to the Special Issue Isotope Hydrology: Tracing Water’s Journey and Water–Rock Interactions in a Changing World)

► Show Figures

Figure 1

27 pages, 7755 KB

Open AccessEditor’s ChoiceArticle

Characterization of a Multi-Diffuser Fine-Bubble Aeration Reactor: Influence of Local Parameters and Hydrodynamics on Oxygen Transfer

by Oscar Prades-Mateu, Guillem Monrós-Andreu, Delia Trifi, Jaume Luis-Gómez, Salvador Torró, Raúl Martínez-Cuenca and Sergio Chiva

Water 2025, 17(24), 3448; https://doi.org/10.3390/w17243448 - 5 Dec 2025

Cited by 1 | Viewed by 1715

Abstract

Fine-bubble aeration is a core process in wastewater treatment plants (WWTPs). However, the physical mechanisms linking bubble plume hydrodynamics to oxygen transfer performance remain insufficiently quantified under configurations representative of full-scale installations. This study presents a local multi-sensor experimental characterization of a multiple [...] Read more.

Fine-bubble aeration is a core process in wastewater treatment plants (WWTPs). However, the physical mechanisms linking bubble plume hydrodynamics to oxygen transfer performance remain insufficiently quantified under configurations representative of full-scale installations. This study presents a local multi-sensor experimental characterization of a multiple bubble plume system using a 4 × 4 array of commercial membrane diffusers in a pilot-scale aeration tank (2 m³), emulating WWTP diffuser density and geometry. Airflow rate was varied to analyze its effects on mixing and oxygen transfer efficiency. The experimental methodology combines three complementary measurement approaches. Oxygen transfer performance is quantified using a dissolved oxygen probe. Liquid-phase velocity fields are then mapped using Acoustic Doppler Velocimetry (ADV). Finally, local two-phase measurements are obtained using dual-tip Conductivity Probe (CP) arrays, which provide bubble size, bubble velocity, void fraction, and Interfacial Area Concentration (IAC). Based on these observations, a zonal hydrodynamic model is proposed to describe plume interaction, wall-driven recirculation, and the formation of a collective plume core at higher airflows. Quantitatively, the results reveal a 29% reduction in Standard Oxygen Transfer Efficiency (SOTE) between 10 and 40 m³/h, driven by a 41% increase in bubble size and an 18% rise in bubble velocity. Bubble chord length also increased with height, by 33%, 19%, and 15% over 0.8 m for 10, 20, and 40 m³/h, respectively. These trends indicate that increasing airflow enhances turbulent mixing but simultaneously enlarges bubbles and accelerates their ascent, thereby reducing residence time and negatively affecting oxygen transfer. Overall, the validated multiphase datasets and mechanistic insights demonstrate the dominant role of diffuser interaction in dense layouts, supporting improved parameterization and experimental benchmarking of fine-bubble aeration systems in WWTPs. Full article

(This article belongs to the Special Issue Hydrodynamics Science Experiments and Simulations, 2nd Edition)

► Show Figures

Figure 1

20 pages, 1296 KB

Open AccessEditor’s ChoiceArticle

Use of Ultrafiltration Membranes as Tertiary/Quaternary Treatment for Wastewater Reclamation in Municipal WWTPs

by Á. Sabina Acebrón, Julio Revert-Vercher, Pau Sanchis-Perucho, Luis Borrás and Aurora Seco

Water 2025, 17(24), 3453; https://doi.org/10.3390/w17243453 - 5 Dec 2025

Cited by 2 | Viewed by 1586

Abstract

This work assesses the viability of ultrafiltration (UF) membranes as a substitution for classic tertiary technologies for municipal wastewater (MWW) treatment. UF membranes can offer efficient MWW filtration, meeting quality standards regarding solids, bacteria, viruses and emerging pollutants, such as microplastics. All of [...] Read more.

This work assesses the viability of ultrafiltration (UF) membranes as a substitution for classic tertiary technologies for municipal wastewater (MWW) treatment. UF membranes can offer efficient MWW filtration, meeting quality standards regarding solids, bacteria, viruses and emerging pollutants, such as microplastics. All of these make UF not only an attractive competitor regarding tertiary treatments but also a potential quaternary treatment according to the latest legislation. Indeed, the achieved permeate quality meets the more stringent parameters for water reuse in agriculture according to the European standard (A-type water). The UF membrane’s feasibility when used as an MWW tertiary/quaternary treatment was assessed in a semi-industrial plant with commercially available industrial membrane modules under different operating conditions: (1) transmembrane flux, (2) air sparging intensity and filtration/relaxation periodicities, (3) the concentration of solids reached in the membrane tank and (4) the efficacy of chemically enhanced backwashing (CEB) to mitigate fouling. Increasing the air intensity (around 0.25 m³ m⁻² h⁻¹), increasing the solids concentration (3–4 g L⁻¹) and using acid chemicals for backwashing at low concentrations but high periodicities (about 25–50 ppm of HCl/citric acid at a pH of 2.5 once or twice every 15 days) displayed great effectiveness in minimizing fouling, which was found to be mainly reversible. Thanks to the stablished conditions, semi-industrial UF membrane filtration was possible for more than 30 days when operating at relatively high transmembrane fluxes (21.5 LMH), achieving an average transmembrane pressure of around 120 mbar with an extremely low fouling growth rate of 0.024 mbar d⁻¹. Full article

(This article belongs to the Special Issue New Advances in Membrane Separation Technology for Water Pollution Control and Membrane Fouling Mitigation)

► Show Figures

Figure 1

22 pages, 3860 KB

Open AccessEditor’s ChoiceArticle

Drought–Flood Abrupt Alternation in the Heilongjiang River Basin Under Climate Change: Spatiotemporal Patterns, Drivers, and Projections

by Fengli Huang, Jianyu Jing, Changlei Dai and Peng Qi

Water 2025, 17(23), 3436; https://doi.org/10.3390/w17233436 - 3 Dec 2025

Cited by 2 | Viewed by 2467

Abstract

Climate change has exacerbated the occurrence of complex extreme hydrological events in high-latitude cold regions, among which drought–flood abrupt events (DFAAEs) threaten food and water security, and accurately predicting their future evolution remains a key challenge. This study used the Community Water Model [...] Read more.

Climate change has exacerbated the occurrence of complex extreme hydrological events in high-latitude cold regions, among which drought–flood abrupt events (DFAAEs) threaten food and water security, and accurately predicting their future evolution remains a key challenge. This study used the Community Water Model (CWatM) hydrological model, combined with five CMIP6 climate models, to simulate runoff datasets for historical periods (1985–2014) and future shared socioeconomic pathways (SSPs: SSP126, SSP370, SSP585: 2015–2100). We calculated the DFAA index (DFAAI), analyzed the spatiotemporal distribution patterns and predicted future trends of DFAAEs in the Heilongjiang River Basin, and explored their climatic driving mechanisms. The main conclusions are as follows: (1) Under SSPs, precipitation and evaporation increase from northwest to southeast, and temperature increases from north to south; hotspots expand inland. By 2100, annual precipitation will reach 655, 700, and 720 mm; mean air temperature will rise by 3, 6, and 7 °C; and annual evapotranspiration will reach 460, 515, and 521 mm. (2) Relative to the historical period, DFAAEs increase from 5.9 to 6.6, 7.1, and 7.5 events per year (SSP126/370/585). Coverage rises from 10.6% to 12.7%, 17.1%, and 19.0%, while mean intensity remains 1.8–2.0. Across both the historical period and SSPs, the shares of light (69–74%), moderate (20–24%), and severe (6–8%) events are stable. (3) Principal Component 1 (PC1,62.9%) reflects a precipitation-dominated wetting mode with synchronous increases in evapotranspiration and is the primary driver of DFAAI variability. PC2 (20.3%) captures an energy-related mode governed mainly by evapotranspiration and indirectly modulated by air temperature, providing a secondary contribution. These results clarify DFAA mechanisms and inform water-resources security planning in the Heilongjiang River Basin. Full article

(This article belongs to the Special Issue Advances in Extreme Hydrological Events Modeling)

► Show Figures

Figure 1

21 pages, 898 KB

Open AccessEditor’s ChoiceReview

Current Research Trends and Challenges Related to the Use of Greywater in Buildings

by Kaja Niewitecka and Monika Żubrowska-Sudoł

Water 2025, 17(23), 3431; https://doi.org/10.3390/w17233431 - 2 Dec 2025

Cited by 1 | Viewed by 3180

Abstract

This paper presents a review of current trends and challenges in greywater use in buildings, with particular emphasis on toilet = flushing applications. It discusses the quantitative and qualitative characteristics of greywater, including its generation sources, share in total domestic wastewater volume (50–89%), [...] Read more.

This paper presents a review of current trends and challenges in greywater use in buildings, with particular emphasis on toilet = flushing applications. It discusses the quantitative and qualitative characteristics of greywater, including its generation sources, share in total domestic wastewater volume (50–89%), and flow variability depending on residents, building type, and user habits. Implementation of greywater recycling technologies faces several challenges, such as parameter variability, stringent sanitary and epidemiological standards, and the presence of micropollutants, including pharmaceuticals. Technological barriers include the integration of multi-stage treatment systems (physical, biological, and chemical) and ensuring effective disinfection for indoor use. The paper also highlights the lack of uniform international regulations and the significant variation in recovered water quality requirements. Key physicochemical and microbiological indicators that determine treatment system requirements are presented, with particular emphasis on the removal of organic pollutants and indicator bacteria. Various physical, chemical, and biological treatment technologies are described, with hybrid systems offering high efficiency and user safety. The implementation of greywater recycling systems encounters technical, regulatory, and social barriers. Social acceptance and transparent monitoring are identified as key challenges for widespread adoption. This critical literature review summarises current knowledge on effective greywater management in buildings, representing an increasingly important issue for sustainable water resource management. Full article

(This article belongs to the Special Issue Drawbacks, Limitations, Solutions and Perspectives of Water Reuse)

► Show Figures

Figure 1

22 pages, 3578 KB

Open AccessEditor’s ChoiceArticle

Integrated Approach to Assess Simulated Rainfall Uniformity and Energy-Related Parameters for Erosion Studies

by Roberto Caruso, Maria Angela Serio, Gabriel Búrdalo-Salcedo, Francesco Giuseppe Carollo, Almudena Ortiz-Marqués, Vito Ferro and María Fernández-Raga

Water 2025, 17(23), 3429; https://doi.org/10.3390/w17233429 - 2 Dec 2025

Cited by 3 | Viewed by 1413

Abstract

Rainfall simulators are crucial devices in erosion research, enabling the controlled reproduction of precipitation characteristics for both laboratory and field investigations. This study presents a comprehensive characterization of a rainfall simulator originally designed to assess the erosive effects of precipitation on heritage surfaces. [...] Read more.

Rainfall simulators are crucial devices in erosion research, enabling the controlled reproduction of precipitation characteristics for both laboratory and field investigations. This study presents a comprehensive characterization of a rainfall simulator originally designed to assess the erosive effects of precipitation on heritage surfaces. The simulator, installed at the University of León, was evaluated using volumetric methods and disdrometric techniques, employing a Parsivel² optical disdrometer. Simulations were conducted with a falling height of 10 m and high-intensity rainfalls. Spatial uniformity was assessed through thematic mapping and the Christiansen Uniformity (CU) coefficient, revealing limited uniformity across the full wetted area, but an improved performance within the central zone (CU up to 80%). Disdrometric data provided detailed insights into drop size and velocity distributions, enabling the estimation of rainfall intensity, kinetic energy, and momentum, as well as the spatial uniformity of the energetic parameters. Empirical models to estimate the raindrop’s fall velocity were tested against disdrometric measurements, confirming the simulator’s ability to generate rainfall with velocity characteristics comparable to those of natural precipitation. Moreover, the findings underscore the importance of integrating multiple measurement approaches to enhance the reliability and accuracy of rainfall simulator characterization. Full article

(This article belongs to the Special Issue Soil Erosion Measurement Techniques and Field Experiments, 2nd Edition)

► Show Figures

Figure 1

18 pages, 8220 KB

Open AccessEditor’s ChoiceArticle

Energy Dissipation in Chute Spillway with Labyrinth Roughness Appurtenances

by James Yang, Shicheng Li, Umar Farooq and Anna Helgesson

Water 2025, 17(23), 3417; https://doi.org/10.3390/w17233417 - 1 Dec 2025

Cited by 2 | Viewed by 1874

Abstract

The updated flood guidelines in Sweden have led to higher design discharges for many existing dams. While the primary function of a spillway chute is to convey floodwater, roughness appurtenances are proposed for installation along the chute. The aim is to dissipate an [...] Read more.

The updated flood guidelines in Sweden have led to higher design discharges for many existing dams. While the primary function of a spillway chute is to convey floodwater, roughness appurtenances are proposed for installation along the chute. The aim is to dissipate an extra portion of the flow’s energy before release into the tailwater. One straight and three labyrinth roughness configurations are designed and manufactured. Their effectiveness is assessed through model tests. The roughness leads to an increase in water depth and induces an undulating streamwise water-surface profile. Due to their lateral interaction with the flow, the labyrinth shapes exhibit less distinct contours of surface unevenness than the straight one. With an increasing water depth, the free surface becomes gradually smeared out. For all the shapes, the roughness effect on the surface flow almost disappears if the water depth exceeds 6.5–7.0 times the roughness height. Compared to the smooth chute, the straight elements augment the energy loss by a factor of 1.9–3.8; the labyrinth configurations outperform the straight ones by 16–35% more energy dissipation. The differences among the triangular, trapezoidal, and rectangular shapes are, however, minor. Introducing chute roughness is a complementary measure. If the chute is sufficiently long, an adequate number of roughness rows could replace the function of a stilling basin. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

24 pages, 4517 KB

Open AccessEditor’s ChoiceArticle

A Comparative Study of the Adsorption of Industrial Anionic Dyes with Bone Char and Activated Carbon Cloth

by Samuel Aguirre-Contreras, María Victoria López-Ramón, Inmaculada Velo-Gala, Miguel Ángel Álvarez-Merino, Angélica Aguilar-Aguilar and Raúl Ocampo-Pérez

Water 2025, 17(23), 3422; https://doi.org/10.3390/w17233422 - 1 Dec 2025

Cited by 6 | Viewed by 1121

Abstract

This study presents a comparative analysis of the adsorption behavior of three industrial ionic dyes—Indigo Carmine (IC), Congo Red (CR), and Evans Blue (EB)—using two adsorbent materials with distinct physicochemical and textural properties: bone char (BC) and activated carbon cloth (ACC). The main [...] Read more.

This study presents a comparative analysis of the adsorption behavior of three industrial ionic dyes—Indigo Carmine (IC), Congo Red (CR), and Evans Blue (EB)—using two adsorbent materials with distinct physicochemical and textural properties: bone char (BC) and activated carbon cloth (ACC). The main objective was to evaluate and compare the adsorption equilibrium and kinetics of these dyes on both materials. Equilibrium behavior was analyzed using the Prausnitz–Radke isotherm model, while adsorption kinetics were evaluated using PVSDM. The results showed that adsorption onto BC was primarily driven by electrostatic interactions, enhanced by the presence of hydroxyapatite. The maximum adsorbed amounts were determined to be 0.296, 0.107, and 0.0614 mmol g⁻¹ for CR, IC, and EB, respectively. In contrast, adsorption on ACC was influenced by both electrostatic and hydrophobic forces due to its carbonaceous composition. IC exhibited significantly higher adsorption on ACC (1.087 mmol g⁻¹), whereas CR and EB only 0.269 mmol g⁻¹ and 0.028 mmol g⁻¹, respectively. Kinetic studies revealed that intraparticle transport was the rate-limiting step across all systems. Specifically, pore volume diffusion controlled the adsorption rate on ACC, with mean diffusion coefficients of 9.72 × 10⁻⁸, 1.83 × 10⁻⁹, and 1.48 × 10⁻¹⁰ cm² s⁻¹ for IC, CR and EB, respectively. Conversely, for BC, adsorption surface diffusion played a dominant role in the adsorption of IC and CR, with mean diffusion coefficients of 1.62 × 10⁻⁹ and 7.28 × 10⁻¹⁰ for IC and CR, respectively. These findings underscore the importance of considering both equilibrium and kinetic parameters in the design of efficient wastewater treatment systems. Full article

(This article belongs to the Special Issue Advanced Materials for the Catalytic Removal of Emerging Pollutants from Water)

► Show Figures

Figure 1

18 pages, 2168 KB

Open AccessEditor’s ChoiceArticle

A Quantitative Sustainability Assessment Framework for Contaminated Site Remediation: Integrating LCA, Economic Analysis, and Social Big Data

by Yuanyuan Li, Ruihui Chen, Xintong Yang, Xiaoyu Liu, Ganghui Zhu and Qiang Hu

Water 2025, 17(23), 3416; https://doi.org/10.3390/w17233416 - 1 Dec 2025

Cited by 4 | Viewed by 1305

Abstract

The remediation of contaminated sites necessitates robust and objective sustainability assessment frameworks to guide decision-making, yet prevailing methods often rely on qualitative or semi-quantitative metrics susceptible to subjectivity. This study establishes a comprehensive, fully quantitative evaluation system integrating environmental, economic, and social dimensions, [...] Read more.

The remediation of contaminated sites necessitates robust and objective sustainability assessment frameworks to guide decision-making, yet prevailing methods often rely on qualitative or semi-quantitative metrics susceptible to subjectivity. This study establishes a comprehensive, fully quantitative evaluation system integrating environmental, economic, and social dimensions, comprising 13 objective indicators derived from Life Cycle Assessment (LCA), economic documentation, and publicly accessible social data—including nighttime light intensity, Point of Interest (POI) data, and social media sentiment analysis. The system employs the Analytic Hierarchy Process (AHP) for weight assignment, ensuring methodological rigor and expert consensus. Validated through three case studies of remediated contaminated sites in Shandong Province, China, the framework reveals distinct sustainability profiles: Site 1 achieved the highest composite score (0.1030), demonstrating balanced performance across all dimensions, whereas Sites 2 and 3 yielded negative scores (−0.2490 and −0.1069, respectively), reflecting trade-offs between remediation efficiency, secondary environmental impacts, and socio-economic outcomes. The key findings underscore the dominance of environmental health indicators—notably Disability-Adjusted Life Years (DALYs)—in overall weighting and highlight the critical influence of remediation technology selection on lifecycle impacts. The study validates the utility of a quantitative, multi-criteria approach in identifying optimal remediation strategies, facilitating cross-project comparability, and supporting the transition from cost-centric remediation toward value-driven, sustainable redevelopment. Full article

(This article belongs to the Special Issue Groundwater Environmental Risk Perception)

► Show Figures

Figure 1

17 pages, 1981 KB

Open AccessEditor’s ChoiceArticle

Integrating Kinetic Models with Physics-Informed Neural Networks (PINNs) for Predicting Methane Production from Anaerobic Co-Digestion of Enzyme-Modified Biodegradable Plastics and Food Waste Leachate

by Zhujun Wang, Shizhuo Wang, Xinnan Zheng, Wenjie Liu and Zheng Shen

Water 2025, 17(23), 3411; https://doi.org/10.3390/w17233411 - 29 Nov 2025

Cited by 5 | Viewed by 1952

Abstract

In the face of increasingly severe water environmental pollution and energy shortages, anaerobic digestion (AD) technology has demonstrated immense potential for the resource recovery of wastewaters such as food waste leachate (FWL). However, the inherent drawback of the long experimental period required for [...] Read more.

In the face of increasingly severe water environmental pollution and energy shortages, anaerobic digestion (AD) technology has demonstrated immense potential for the resource recovery of wastewaters such as food waste leachate (FWL). However, the inherent drawback of the long experimental period required for AD severely constrains research efficiency. Existing studies often rely on either kinetic models with high interpretability or machine learning models with strong generalization capabilities, rarely integrating both. To address this, this study innovatively investigated the anaerobic co-digestion of enzyme-modified biodegradable plastics (BPs) and FWL, and constructed a novel Physics-Informed Neural Network (PINN) based on a dataset of 261 experimental observations. The results indicated that, among the three kinetic models, the Modified Gompertz model exhibited the best prediction accuracy (R² approaching 0.99), stability, and universality. Among the four machine learning models, the Artificial Neural Network (ANN) demonstrated optimal generalization ability (Test set R² = 0.958). Notably, the constructed Modified Gompertz PINN model achieved superior predictive performance (Test set R² = 0.994), reducing the Root Mean Square Error (RMSE) by 74.0% compared to the ANN model. Shapley analysis further confirmed the PINN retained strong biological rationality, indicating that the hydrolysis process significantly impacts methane production. This work provides a robust hybrid model for efficient co-digestion prediction and offers a new approach for the resource valorization of enzyme-modified BPs and FWL. Full article

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

► Show Figures

Figure 1

21 pages, 2031 KB

Open AccessEditor’s ChoiceArticle

Settlement Induction in Mytilus coruscus Is Driven by Cue Diversity: Evidence from Natural Biofilms and Bacterial Isolates

by Ni Chen, Yonghui Fu, Qianyu Zhang, Jie Du, Wanting Liu, Xinjie Liang, Yingying Ye and Jiji Li

Water 2025, 17(23), 3395; https://doi.org/10.3390/w17233395 - 28 Nov 2025

Cited by 1 | Viewed by 1229

Abstract

Mytilus coruscus, a commercially important mariculture mussel in China, has shown a marked decline in larval settlement and metamorphosis over the past decade, a trend often linked to environmental degradation and resource depletion. Numerous studies have identified bacterial biofilms as key modulators [...] Read more.

Mytilus coruscus, a commercially important mariculture mussel in China, has shown a marked decline in larval settlement and metamorphosis over the past decade, a trend often linked to environmental degradation and resource depletion. Numerous studies have identified bacterial biofilms as key modulators of mussel larval settlement. To investigate this, we deployed PVC plates in situ within aquaculture zones near Shengsi (Zhoushan, Zhejiang) and Lianjiang (Fuzhou, Fujian). After natural biofilm colonization on the plates, juvenile M. coruscus were introduced to assess settlement rates. The attached juveniles were homogenized, leading to the isolation of four dominant bacterial strains: Pseudomonas sp. LJBF001, Vibrio sp. LJBF002, Pseudomonas sp. LJBF003 and Bacillus sp. LJBF004. Compared to control PVC plates, natural biofilms significantly promoted juvenile settlement, with the Lianjiang (LJ) group reaching up to >29% under our assay conditions. In contrast, monospecific biofilms prepared from these isolates did not significantly increase larval metamorphosis; the numerically highest response (LJBF004) reached ~9% and was not significant versus the control. These contrasting outcomes are consistent with a threshold–multi-cue synergy mechanism, whereby cue diversity and partial redundancy in natural biofilms favour threshold crossing, while restricted cue sets in single-strain films often fall short. Guided by this framework, priority next steps include testing c-di-GMP delivery (soluble and via OMVs), probing EPS structure–function and EPS–OMV/LPS–free-fatty-acid blends alongside minimal multi-strain consortia, and adopting stage-gated assays with time-to-event endpoints and effect-size/CI reporting. Full article

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

► Show Figures

Figure 1

Journal Menu

Journal Browser

Editor’s Choice Articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI