Water

18 pages, 2530 KiB

Open AccessArticle

Fluoride Risk Prognostication: A Pioneering Ensemble Machine Learning Approach for Groundwater Contamination Prediction in Parts of the East Coast of India

by Alok Kumar Pati, Alok Ranjan Tripathy, Debabrata Nandi, Rakesh Ranjan Thakur, Bojan Ðurin, Dragana Dogančić and Osman Fetoshi

Water 2025, 17(6), 909; https://doi.org/10.3390/w17060909 - 20 Mar 2025

Viewed by 487

Abstract

Groundwater fluoride levels have begun to be a global concern, posing significant challenges to the safe utilization of water resources and mitigating potential impacts on human health. Chronic exposure to elevated levels of naturally occurring fluoride in groundwater affects millions worldwide. Prolonged exposure [...] Read more.

Groundwater fluoride levels have begun to be a global concern, posing significant challenges to the safe utilization of water resources and mitigating potential impacts on human health. Chronic exposure to elevated levels of naturally occurring fluoride in groundwater affects millions worldwide. Prolonged exposure can lead to health issues such as dental fluorosis and skeletal fluorosis. The World Health Organization (WHO) has established a maximum fluoride concentration guideline of 1.5 mg/L for drinking water. However, groundwater quality is not regularly tested in many regions, leaving communities unaware if water sources, such as wells and springs, contain harmful fluoride levels. In the Balasore area, Odisha, India, rising fluoride concentrations and spatial variability necessitate accurate predictions for effective groundwater management. This article proposes four predictive models, Random Forest (RF), Support Vector Regression (SVR), Gradient Boosting (XGBoost), and Stacking Regressor (SR), to estimate fluoride concentrations using physicochemical parameters and sampling depth as predictor variables. The performance of these models is assessed using the coefficient of determination (accuracy), mean square error (MSE), and mean absolute error (MAE). This article compared fluoride concentrations of machine learning models, including SR, RF, XGBoost, and SVR, in groundwater in Balasore, Odisha. Based on predictive performance, an SR model yielded the lowest MSE and MAE scores at 0.01817 and 0.10327, respectively. These findings underscore the superiority of ensemble learning approaches in addressing complex datasets and provide a robust framework for effective groundwater fluoride management. This article highlights the potential of advanced machine learning in improving public health outcomes in fluoride-affected regions. Finally, the recommendations for decreasing the fluoride concentrations and the guidelines for future research will be proposed. Full article

(This article belongs to the Special Issue The Qualitative and Quantitative Management of Groundwater Resources in Urban Areas)

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19 pages, 4387 KiB

Open AccessArticle

Hydroxyapatite-Modified Zeolite for Fluoride Removal from Drinking Water: Adsorption Mechanism Investigation and Column Study

by Rajinda Boteju, Libing Zheng, Hewa M. S. Wasana, Qiyang Wu, Yuansong Wei, Hui Zhong, Yawei Wang and Ajith de Alwis

Water 2025, 17(6), 908; https://doi.org/10.3390/w17060908 - 20 Mar 2025

Cited by 1 | Viewed by 390

Abstract

This study investigates the synthesis and application of hydroxyapatite (HAp)-modified zeolite materials for efficient fluoride removal from groundwater-based drinking water. Characterization confirmed the successful incorporation of HAp onto the zeolite surface and the formation of a stable composite. EDS analysis revealed the presence [...] Read more.

This study investigates the synthesis and application of hydroxyapatite (HAp)-modified zeolite materials for efficient fluoride removal from groundwater-based drinking water. Characterization confirmed the successful incorporation of HAp onto the zeolite surface and the formation of a stable composite. EDS analysis revealed the presence of Ca and P after modification, while FTIR and XRD confirmed the structural integrity of HAp during adsorption. ZH8 exhibited the highest F-removal efficiency of 92.23% at pH 3, 30 °C, [F⁻] = 6 ppm and dose = 10 g/L. Meanwhile, HAp-modified zeolite showed high F-selectivity, and the competing ions had limited interference. The Langmuir model best described the adsorption process, suggesting monolayer adsorption with a maximum capacity of 39.38 mg/g for ZH8. The process followed pseudo-first-order kinetics, with equilibrium achieved within 4 h. Regeneration studies demonstrated that ZH8 maintained over 85% efficiency for three cycles, highlighting its reusability. Column studies validated the material’s practical applicability, with breakthrough times of up to 23 h under optimal conditions (flow rate: 8 cm³ min⁻¹, bed depth: 30 cm, feed concentration: 7.5 ppm) and a maximum yield of 99% at [F⁻] = 5 ppm with V_b = 10.8 L. The Thomas model best described the column adsorption process, indicating chemical adsorption as the dominant mechanism. These findings demonstrate the potential of HAp-modified zeolite, particularly ZH8, as an effective adsorbent for fluoride removal in real-world applications. Full article

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

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14 pages, 2786 KiB

Open AccessArticle

Long Short-Term Memory (LSTM) Networks for Accurate River Flow Forecasting: A Case Study on the Morava River Basin (Serbia)

by Igor Leščešen, Mitra Tanhapour, Pavla Pekárová, Pavol Miklánek and Zbyněk Bajtek

Water 2025, 17(6), 907; https://doi.org/10.3390/w17060907 - 20 Mar 2025

Viewed by 566

Abstract

Accurate forecasting of river flows is essential for effective water resource management, flood risk reduction and environmental protection. The ongoing effects of climate change, in particular the shift in precipitation patterns and the increasing frequency of extreme weather events, necessitate the development of [...] Read more.

Accurate forecasting of river flows is essential for effective water resource management, flood risk reduction and environmental protection. The ongoing effects of climate change, in particular the shift in precipitation patterns and the increasing frequency of extreme weather events, necessitate the development of advanced forecasting models. This study investigates the application of long short-term memory (LSTM) neural networks in predicting river runoff in the Velika Morava catchment in Serbia, representing a pioneering application of LSTM in this region. The study uses daily runoff, precipitation and temperature data from 1961 to 2020, interpolated using the inverse distance weighting method. The LSTM model, which was optimized using a trial-and-error approach, showed a high prediction accuracy. For the Velika Morava station, the model showed a mean square error (MSE) of 2936.55 and an R² of 0.85 in the test phase. The findings highlight the effectiveness of LSTM networks in capturing nonlinear hydrological dynamics, temporal dependencies and regional variations. This study underlines the potential of LSTM models to improve river forecasting and water management strategies in the Western Balkans. Full article

(This article belongs to the Section Hydrology)

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22 pages, 5638 KiB

Open AccessArticle

Dynamic Changes in Both Summer Potential Evapotranspiration and Its Driving Factors in the Huai River Basin, China

by Saiyan Liu, Zheng Gao, Yangyang Xie, Dongyong Sun, Hongyuan Fang, Huihua Du and Pengcheng Xu

Water 2025, 17(6), 906; https://doi.org/10.3390/w17060906 - 20 Mar 2025

Viewed by 188

Abstract

Potential evapotranspiration (ETp) is an important component of the water and energy cycle. This study investigated the changing patterns of both summer ETp and its drivers in the Huai River Basin for the first time using the newly proposed anomaly contribution analysis method, [...] Read more.

Potential evapotranspiration (ETp) is an important component of the water and energy cycle. This study investigated the changing patterns of both summer ETp and its drivers in the Huai River Basin for the first time using the newly proposed anomaly contribution analysis method, as summer is usually the peak period of ETp but little has been done to study it specifically. The anomaly contribution analysis method is able to calculate the contribution rates of climate factors to summer ETp for every year, which helps to reveal the dynamic changes in the contribution of climate factors to summer ETp. The results show that the evaporation paradox is not accurate for the basin since summer ETp declines significantly while the trend of summer Tm is insignificant. Influenced by the abrupt changes in summer Sh and Ws, summer ETp underwent a mutation around the 1970s and 1980s. Sensitivity analysis and contribution analysis show that the most sensitive meteorological factors may not contribute the most to summer ETp. Contribution analysis at a multi–year scale and the results of the anomaly contribution analysis method demonstrate that dominant factors of ETp may be different at multi–year and seasonal scales in the same region. Moreover, the dominant meteorological factors of summer ETp are also different at station and basin scales due to scale effects. Further, dynamic changes in contribution rates show that contributions of summer climate factors have clear positive–negative alterations. Additionally, there are also differences in the spatial distribution of contribution rates between the north–south and east–west directions. These findings will not only provide valuable information for regional water resources management but also provide new insights into the evolution of ETp under climate change. Full article

(This article belongs to the Section Hydrology)

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27 pages, 9731 KiB

Open AccessArticle

Interpretable Machine Learning Based Quantification of the Impact of Water Quality Indicators on Groundwater Under Multiple Pollution Sources

by Tianyi Zhang, Jin Wu, Haibo Chu, Jing Liu and Guoqiang Wang

Water 2025, 17(6), 905; https://doi.org/10.3390/w17060905 - 20 Mar 2025

Viewed by 312

Abstract

Accurate evaluation of groundwater quality and identification of key characteristics are essential for maintaining groundwater resources. The purpose of this study is to strengthen water quality evaluation through the SHAP and XGBoost algorithms, analyze the key indicators affecting water quality in depth, and [...] Read more.

Accurate evaluation of groundwater quality and identification of key characteristics are essential for maintaining groundwater resources. The purpose of this study is to strengthen water quality evaluation through the SHAP and XGBoost algorithms, analyze the key indicators affecting water quality in depth, and quantify their impact on groundwater quality through interpretable tools. The XGBoost algorithm shows that zinc (0.183), nitrate (0.159), and chloride (0.136) are the three indicators with the highest weight. The SHAP algorithm shows that zinc (34.62%), nitrate (17.65%), and chloride (16.98%) have higher contribution values, which explains the output results of XGBoost. According to the calculation scores and classification standards of the water quality model, 49% of the groundwater samples in the study area have excellent water quality, 33% of the samples are better, and 18% of the samples are polluted. The results of positive matrix factorization (PMF) show that natural conditions, metal processing, metal smelting and mining, and agricultural activities all cause pollution to groundwater. Zinc, chloride, nitrate, and manganese were the key variables determined by the SHAP algorithm to explain the vast majority of human health risk sources. These findings indicate that interpretable machine learning not only improves the correlation of water quality assessment but also quantifies the judgment basis of each sample and helps to track key pollution indicators. Full article

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

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15 pages, 11806 KiB

Open AccessArticle

Numerical Investigation on Planar Configuration of a Floating Breakwater System Encircling an Artificial Floating Island

by Zhipeng Zang, Zhuo Fang, Kuan Qiao, Yinkang Li, Chunhui Zhang and Jinfeng Zhang

Water 2025, 17(6), 904; https://doi.org/10.3390/w17060904 - 20 Mar 2025

Viewed by 259

Abstract

This paper presents a quantitative investigation into the hydrodynamic characteristics of a floating breakwater system encompassing an artificial floating island. The floating breakwater’s cross-section is configured as a collection of multiple buoys, with a large main horizontal cylinder and two small cylinders. A [...] Read more.

This paper presents a quantitative investigation into the hydrodynamic characteristics of a floating breakwater system encompassing an artificial floating island. The floating breakwater’s cross-section is configured as a collection of multiple buoys, with a large main horizontal cylinder and two small cylinders. A navigation channel opening is incorporated into the floating breakwater, fortified by a floating gate positioned externally. The wave patterns surrounding the floating breakwater system are simulated and analyzed using ANSYS-AQWA (R19.0) software. The research investigates the mean transmission coefficients in the area encompassed by the floating breakwaters, considering a range of influential parameters. These parameters include the dimensions of the navigation channel opening, the planar dimensions of the floating breakwater system, the type of mooring chains, as well as the incident wave height, wave period, and wave directions, among others. Additionally, this study evaluates the impact of the navigation channel’s floating gate shape on the wave dissipation performance of the floating breakwater system. An opening angle of 75° for the navigation channel has been determined as optimal, balancing wave dissipation performance with the structural complexity of the harbor gate. The ideal distance between the floating breakwater system and the central floating island is identified as 300 m. The tensioned mooring system demonstrated superior performance compared to the catenary system. Furthermore, the arc-shaped harbor gate achieved a 26% reduction in wave transmission relative to the linear gate. These findings offer practical design guidelines for improving the stability and cost-effectiveness of floating breakwater systems in open-sea environments. Full article

(This article belongs to the Special Issue Wave–Structure Interaction in Coastal and Ocean Engineering)

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18 pages, 5214 KiB

Open AccessArticle

Picoplankton Groups and Their Responses to Environmental Factors in Small Cascade Hydropower Stations

by Peiquan Li, Zhongxin Luo, Xianfang Zhu, Zhengzhu Dang, Daxin Zhang and Xin Sui

Water 2025, 17(6), 903; https://doi.org/10.3390/w17060903 - 20 Mar 2025

Viewed by 279

Abstract

Hydropower is a clean and renewable energy source, and cascade hydropower stations have been developed to enhance water energy utilization efficiency. While small hydropower stations have a smaller scale and environmental impact compared to large ones, the cumulative effects of cascade development on [...] Read more.

Hydropower is a clean and renewable energy source, and cascade hydropower stations have been developed to enhance water energy utilization efficiency. While small hydropower stations have a smaller scale and environmental impact compared to large ones, the cumulative effects of cascade development on river ecosystems should not be overlooked. In this study, flow cytometry was used to classify picoplankton from water samples collected at four small cascade hydropower stations on a Pearl River tributary into six microbial groups: Virus, LNA (Low Nucleic Acid), HNA (High Nucleic Acid), Cyanobacteria, Algae, and Fungi. Four ecological assessment indices were calculated: Photosynthetic Autotrophic Capacity (PAC), Bacterial Activity Index (BAI), Virus Regulatory Capacity (VRC), and Fungal Metabolic Capacity (FMC). By analyzing trends in microbial abundance and ecological indices and their correlations with environmental factors, the results showed that along the small cascade hydropower stations, dissolved oxygen (DO) and electrical conductivity (EC) increased from 5.71 mg/L and 49.87 μS/cm upstream to 6.80 mg/L and 56.18 μS/cm downstream, respectively. In contrast, oxidation-reduction potential (ORP) and total organic carbon (TOC) concentrations decreased from 3.81 mV and 1.59 mg/L to −8.05 mV and 1.08 mg/L, respectively. Among the microbial groups, the abundance of Virus, LNA, and Fungi decreased by 30.9%, 30.5%, and 34.9%, respectively, along the cascade system. EC, TOC, and NO₃⁻-N were identified as key drivers of changes in the abundance of the Virus, LNA, and Fungi groups. The concentrations of carbon and nitrogen nutrients significantly influenced the ecological assessment indices. Cascade hydropower stations had a significant impact on PAC, BAI, and VRC, while their influence on FMC was relatively small. The VRC showed a decreasing trend, suggesting a weakening effect of the stations on VRC. This study offers new perspectives and methods that facilitate the rapid and quantitative assessment of the ecological impacts of cascade hydropower stations. Full article

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

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14 pages, 1384 KiB

Open AccessArticle

Analysis of Selected Elements in Rivers and Streams of Papuk Nature Park, Croatia

by Vlatka Gvozdić, Marina Vidosavljević, Miroslav Venus, Dinko Puntarić, Zvonimir Užarević, Eda Puntarić, Mario Begović, Damir Danolić and Domagoj Vidosavljević

Water 2025, 17(6), 902; https://doi.org/10.3390/w17060902 - 20 Mar 2025

Viewed by 315

Abstract

This study is the first investigation into the content of heavy metals (ecotoxic) and metalloids in the available water resources of the Papuk Nature Park (Croatia), conducted after the war in Croatia. Analyses of 13 elements, As, B, Ba, Cd, Co, Cr, Cu, [...] Read more.

This study is the first investigation into the content of heavy metals (ecotoxic) and metalloids in the available water resources of the Papuk Nature Park (Croatia), conducted after the war in Croatia. Analyses of 13 elements, As, B, Ba, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sr, V and Zn, were carried out on 21 water samples from rivers and their tributaries using the ICP-MS method. The concentration of heavy metals and metalloids in the water of the rivers and their tributaries was low, revealing an intact water environment. Depending on the area of sampling, medians (in µgL⁻¹) were 0.50–4.22 (As), 1.90–141.78 (B), 0.31–60.01 (Ba), 0.16–0.57 (Cd), 0.095–0.62 (Co), 0.18–0.66 (Cr), 1.59–15.89 (Cu), 12.1–1692.2 (Fe), 0.26–8.21 (Ni), 0.017–4.45 (Pb), 0.039–126.09 (Sr), 0.48–2.53 (V), and 3.01–25.95 (Zn). Higher concentrations of Fe (median ranged from 155.42 to 968.20 µgL⁻¹) were found in the northern part of the Papuk Nature Park and are considered to be of natural origin; therefore, anthropogenic influences are excluded. The watercourses of the Papuk Nature Park are generally characterized as a clean ecosystem. This, in part, can be attributed to the human activism legislation that declared Papuk a Nature Park, and the self-healing potential of nature. Full article

(This article belongs to the Section Hydrology)

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22 pages, 6014 KiB

Open AccessArticle

Evaluation of Industrial Water Use Efficiency on an Enterprise Scale Based on Analytic Hierarchy Process, Entropy Weight Method and Self-Organizing Map: A Case Study in Zhejiang, China

by Yimin Qian, Yingjie Zhao, Hao Qian, Junhong Xiang, Caiming Chen, Longqiang Su and Chenkai Cai

Water 2025, 17(6), 901; https://doi.org/10.3390/w17060901 - 20 Mar 2025

Cited by 1 | Viewed by 343

Abstract

The increasingly serious imbalance between the supply and demand of water resources necessitates the establishment of a scientific and reasonable comprehensive evaluation method for industrial water use efficiency (WUE). In this study, a general method for industrial WUE evaluation on an enterprise scale [...] Read more.

The increasingly serious imbalance between the supply and demand of water resources necessitates the establishment of a scientific and reasonable comprehensive evaluation method for industrial water use efficiency (WUE). In this study, a general method for industrial WUE evaluation on an enterprise scale was proposed by combining the analytic hierarchy process (AHP), entropy weight method (EWM), and self-organizing map (SOM), and it was tested in several areas of Zhejiang Province, China. The results show that the composite indexes generated using the AHP and EWM were different and were employed as the input of the SOM to divide enterprises into four categories. Most enterprises were classified as Class A, with a relatively high WUE, accounting for 82.5% of the total, while those in Class D, with a relatively low WUE, only accounted for 0.5% of the total. Furthermore, the differences in WUE for industry classification and spatial distribution were also analyzed. The classification results of several industries were more diverse, especially for those industries in which water plays an important role in production. Moreover, the spatial distribution of WUE classifications also implied that the clustering of enterprises has a positive effect on the improvement in WUE. In other words, it is feasible to improve WUE through industry clustering and sub-industry management. In summary, a comprehensive, detailed evaluation of industrial WUE was conducted on an enterprise scale, which can also be applied to other areas and used as a reference for local water resource managers for formulating targeted policies. Full article

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

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17 pages, 3167 KiB

Open AccessArticle

Distribution of Nitrification and Its Regulating Factors in Coastal Bays with Distinct Trophic Gradients

by Yanhua Wu, Wei Wei, Tao Luo, Xingnian Sun, Guanghe Shao, Zhenzhen Zheng, Lei Wei, Bin Xiu, Congqiang Wang, Wei Liu, Zibin Wang, Peng Zhou, Shuh-Ji Kao and Ehui Tan

Water 2025, 17(6), 900; https://doi.org/10.3390/w17060900 - 20 Mar 2025

Viewed by 349

Abstract

Nitrification is the key process linking the oxidized and reduced forms of reactive nitrogen, playing an important role in the nitrogen biogeochemical cycle. Quantifying the nitrification rate and evaluating its environmental regulators in different aquatic environments at both regional and global scales has [...] Read more.

Nitrification is the key process linking the oxidized and reduced forms of reactive nitrogen, playing an important role in the nitrogen biogeochemical cycle. Quantifying the nitrification rate and evaluating its environmental regulators in different aquatic environments at both regional and global scales has received increasing attention. However, the spatiotemporal variations in nitrification rates in coastal waters, particularly with different trophic states, remain unclear. By using the ¹⁵N-labeling technique, here, we quantified the nitrification rates under dark and light conditions in the surface waters of Shenzhen Bay and Dapeng Bay, representing eutrophic and oligotrophic environments, respectively. The nitrification rates were 2–3 orders of magnitude higher in Shenzhen Bay (eutrophic) than those in Dapeng Bay (oligotrophic). The concentrations of ammonium and total suspended matter play key roles in regulating the spatiotemporal distribution and difference in nitrification in these two coastal bays. The nitrification rate under the dark condition (0.13–49.37 nmol N L⁻¹ h⁻¹) was greater than that under light incubation (0–10.15 nmol N L⁻¹ h⁻¹), indicating light inhibition of 33–100% in the surface water. Such results imply that daily integrated nitrification based on the rates under dark incubation may have been overestimated. An environment with high turbidity is preferable for nitrification, as it reduces the damage caused by light to ammonia-oxidizing microbes. Collectively, the differences in nitrification rates further result in a distinct composition of dissolved inorganic nitrogen, with Shenzhen Bay dominated by nitrate and Dapeng Bay dominated by ammonium. Our results provide scientific references for the mitigation of nitrogen pollution in different trophic coastal bays. Full article

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29 pages, 5493 KiB

Open AccessArticle

Effectiveness of Water-Sensitive Urban Design Techniques on Stormwater Quantity Management at a Residential Allotment Scale

by Samira Rashetnia, Ashok K. Sharma, Anthony R. Ladson, Dale Browne and Ehsan Yaghoubi

Water 2025, 17(6), 899; https://doi.org/10.3390/w17060899 - 20 Mar 2025

Viewed by 549

Abstract

Rapid population growth and urbanization are transforming natural landscapes into built environments, resulting in increased stormwater runoff, which poses significant challenges for local governments to manage. Water-Sensitive Urban Design (WSUD) techniques have been implemented to enhance urban stormwater quality, but their effectiveness in [...] Read more.

Rapid population growth and urbanization are transforming natural landscapes into built environments, resulting in increased stormwater runoff, which poses significant challenges for local governments to manage. Water-Sensitive Urban Design (WSUD) techniques have been implemented to enhance urban stormwater quality, but their effectiveness in managing stormwater quantity and quality across different scales remains uncertain. This study examines the capacity of various WSUD approaches to reduce stormwater runoff volume and peak flow rates in a residential allotment transitioning from a single dwelling to a redeveloped condition with two dwellings. The tested techniques included a rainwater tank, infiltration trench, rain garden, vegetated swale, and permeable pavement. For storm events with a 1-in-5-year Annual Recurrence Interval (ARI)—aligning with typical piped drainage design standards—peak flow rates were reduced by 90% in the redeveloped scenario. Smaller storm events, up to a 1-in-1-year ARI, were frequently eliminated, thereby minimizing disturbances to waterways caused by frequent runoff discharges. Among the tested techniques, the combination of a rainwater tank, rain garden, and infiltration trench demonstrated the greatest effectiveness in reducing stormwater runoff volume and peak flow rates despite considerations of life cycle costs. These findings highlight the potential of integrated WSUD techniques in addressing urban stormwater management challenges. Full article

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

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25 pages, 5539 KiB

Open AccessArticle

Hydrogeochemical Signatures and Processes Influencing Mineral Waters at Furnas Volcano (São Miguel, Azores)

by Letícia Ferreira, José Virgílio Cruz, Fátima Viveiros, Nuno Durães, César Andrade, Carlos Almeida, Nuno Cabral, Rui Coutinho and José Francisco Santos

Water 2025, 17(6), 898; https://doi.org/10.3390/w17060898 - 20 Mar 2025

Viewed by 352

Abstract

Furnas volcano, one of the three active central volcanoes of São Miguel (the Azores archipelago), hosts mineral waters with significant special variations, divided into hyperthermal (89.4–95.4 °C), thermal (29.9–70.0 °C), and cold (14.2–21.4 °C) waters. Groundwaters are classified as Na-HCO₃, with [...] Read more.

Furnas volcano, one of the three active central volcanoes of São Miguel (the Azores archipelago), hosts mineral waters with significant special variations, divided into hyperthermal (89.4–95.4 °C), thermal (29.9–70.0 °C), and cold (14.2–21.4 °C) waters. Groundwaters are classified as Na-HCO₃, with a neutral to slightly acidic pH, except one SO₄-Na acidic sample. The major elements are primarily influenced by rock leaching and volcanic input, patterns also reflected in the trace elements, including the rare earth elements. The major cations, along with lithium, iron, aluminum, rubidium, and strontium, indicate the influence of water–rock interactions. Some samples depict a higher influence in this input, shown by the similar REE behavior between them and the local rock behavior. The volcanic input is distinguished into two environments: an acid sulfate boiling pool, formed by steam heating, and neutral HCO₃-Cl waters, where bicarbonate-rich waters mix with a neutral chloride fluid from a deep reservoir. The deeper reservoir also provides boron, arsenic, antimony, and tungsten, also seemingly associated with a positive spike in europium due to rock dissolution at temperatures above 250 °C or a reducing environment. This interpretation is corroborated by the stability of the strontium isotopes between samples. Full article

(This article belongs to the Section Hydrogeology)

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13 pages, 1519 KiB

Open AccessReview

Reviewing Water Wars and Water Weaponisation Literatures: Is There an Unnoticed Link?

by Paula Duarte Lopes and Margarida Gama

Water 2025, 17(6), 897; https://doi.org/10.3390/w17060897 - 20 Mar 2025

Viewed by 577

Abstract

The prediction made by former Vice President of the World Bank, Ismail Serageldin, that the wars of the 21st century will be about water, remains on the international political agenda. Yet, there is enough evidence corroborating that water wars have not occurred in [...] Read more.

The prediction made by former Vice President of the World Bank, Ismail Serageldin, that the wars of the 21st century will be about water, remains on the international political agenda. Yet, there is enough evidence corroborating that water wars have not occurred in the past and that there are sufficient mechanisms in place to prevent them in the future. Simultaneously, domestic water violent conflicts have been taking place, usually as immediate reactions to localised disputes. More importantly, water weaponisation has been gaining visibility during violent conflicts, violating international humanitarian law without any consequences so far. This paper reviews the water wars and water weaponisation literatures, arguing that there is an under-researched link between these two literatures and practices. This review suggests that the water weaponisation discourse and practice may facilitate the context for the water wars prophecy to become true. Full article

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16 pages, 1414 KiB

Open AccessOpinion

On Seven Principles of Water Governance

by Renzo Rosso

Water 2025, 17(6), 896; https://doi.org/10.3390/w17060896 - 20 Mar 2025

Viewed by 1019

Abstract

Water problems extend beyond the watershed of local communities and single countries. A novel governance approach must comprise coordination and institutional arrangements at the global scale, and rely on a set of axioms that guide the decision-making and actions of various stakeholders involved [...] Read more.

Water problems extend beyond the watershed of local communities and single countries. A novel governance approach must comprise coordination and institutional arrangements at the global scale, and rely on a set of axioms that guide the decision-making and actions of various stakeholders involved in water-related issues. These principles must reflect the awareness of water paradigms across history and geography, as well as the economic, social, environmental, and ethical dimensions of water, aiming at ensuring its sustainable and equitable use, driving governance towards recognizing the value of water for public health and social cohesion, the link of landscape and identity values to water bodies, the social, aesthetic-recreational, and symbolic values of water across the world, and the functions of water in nature. The principles presented here include the human right to water, ecosystem centrality, the principles of shared integration, precautionary, responsibility, and subsidiarity, along with the concept of the common good. The assessment of principles of water governance is essential for implementing any guideline of water management aimed not only at efficiency and security, but at equity and sustainability of water supply and flood mitigation in a globalized and conflict-ridden world. Full article

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

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15 pages, 1773 KiB

Open AccessArticle

Relationships Between Land Use and Stream Macroinvertebrate Biotic Integrity in Central Ohio, USA

by Douglas Spieles, Zoe Krashes, Khiem Nguyen, Summer Rodgers, Lillian Ruiz and Marco Vigilante

Water 2025, 17(6), 895; https://doi.org/10.3390/w17060895 - 20 Mar 2025

Viewed by 448

Abstract

Land use is known to be an important factor in the composition and function of adjacent freshwater lotic ecosystems. However, the relative effects of land use type, extent, intensity, and proximity on aquatic ecosystem quality are not fully understood. We evaluate these questions [...] Read more.

Land use is known to be an important factor in the composition and function of adjacent freshwater lotic ecosystems. However, the relative effects of land use type, extent, intensity, and proximity on aquatic ecosystem quality are not fully understood. We evaluate these questions in low-order streams within 30 watersheds in developed, agricultural, and less developed landscapes of central Ohio, USA. We assess the relationships of land use cover percentage and spatial scale with stream macroinvertebrate community diversity and biotic integrity. We also investigate the importance of impervious cover and subsurface tile drainage within each watershed and Active River Area (ARA). We find that the percentage of coverage of developed land at the watershed scale is the strongest predictor of stream macroinvertebrate community diversity and integrity. High-intensity development is a stronger negative correlate than low-intensity development or agriculture. There is a significant decline in stream macroinvertebrate diversity and biotic integrity at the watershed and ARA scales when undeveloped land coverage falls below 20–30%. We do not find a significant relationship between stream macroinvertebrate metrics and land use at the 1 km² scale or in comparison with any instream habitat attributes except sinuosity. Impervious cover has a significant negative relationship with both macroinvertebrate taxon richness and biotic integrity at the watershed and ARA scales. However, subsurface tile-drained land does not have a significant relationship with the stream macroinvertebrate community at any scale. We conclude that impervious land cover at the watershed and ARA scales is a critical factor for the biotic integrity of small streams in this region. Collectively, our conclusions provide evidence to support practices of ecologically sensitive land use planning. Full article

(This article belongs to the Special Issue Aquatic Ecosystems: Biodiversity and Conservation)

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24 pages, 6891 KiB

Open AccessArticle

Assessment of Future Rainfall Quantile Changes in South Korea Based on a CMIP6 Multi-Model Ensemble

by Sunghun Kim, Ju-Young Shin and Jun-Haeng Heo

Water 2025, 17(6), 894; https://doi.org/10.3390/w17060894 - 20 Mar 2025

Viewed by 558

Abstract

Climate change presents considerable challenges to hydrological stability by modifying precipitation patterns and exacerbating the frequency and intensity of extreme rainfall events. This research evaluates the prospective alterations in rainfall quantiles in South Korea by employing a multi-model ensemble (MME) derived from 23 [...] Read more.

Climate change presents considerable challenges to hydrological stability by modifying precipitation patterns and exacerbating the frequency and intensity of extreme rainfall events. This research evaluates the prospective alterations in rainfall quantiles in South Korea by employing a multi-model ensemble (MME) derived from 23 Global Climate Models (GCMs) associated with the Coupled Model Intercomparison Project Phase 6 (CMIP6) under four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5). Historical rainfall data from simulations (1985–2014) and future projections (2015–2044, 2043–2072, and 2071–2100) were analyzed across a total of 615 sites. Statistical Quantile Mapping (SQM) bias correction significantly enhanced the accuracy of projections (RMSE reduction of 63.0–85.3%, Pbias reduction of 93.6%, and R² increase of 0.73). An uncertainty analysis revealed model uncertainty to be the dominant factor (approximately 71.87–70.49%) in the near- to mid-term periods, and scenario uncertainty increased notably (up to 5.94%) by the end of the century. The results indicate substantial temporal and spatial changes, notably including increased precipitation in central inland and eastern coastal regions, with peak monthly increases exceeding 40 mm under high-emission scenarios. Under the SSP2-4.5 and SSP5-8.5 scenarios, the 100-year rainfall quantile is projected to increase by over 40% across significant portions of the country, emphasizing growing challenges for water resource management and infrastructure planning. These findings provide critical insights for water resource management, disaster mitigation, and climate adaptation strategies in South Korea. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Water Resources: Assessment and Modeling, 2nd Edition)

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11 pages, 1048 KiB

Open AccessArticle

Evolution of Water Governance for Climate Resilience: Lessons from Japan’s Experience

by Mikio Ishiwatari, Kenji Nagata and Miho Matsubayashi

Water 2025, 17(6), 893; https://doi.org/10.3390/w17060893 - 19 Mar 2025

Viewed by 717

Abstract

Water resources management needs to be strengthened to address increasing flood and drought risks exacerbated by climate change and socio-economic development. This requires effective water governance mechanisms that can reduce vulnerability in disasters while managing complex stakeholder relationships. This paper analyzes the evolution [...] Read more.

Water resources management needs to be strengthened to address increasing flood and drought risks exacerbated by climate change and socio-economic development. This requires effective water governance mechanisms that can reduce vulnerability in disasters while managing complex stakeholder relationships. This paper analyzes the evolution of water governance in Japan over more than half a century, examining how the country transformed from a centralized, top-down approach to a more collaborative model of water management. Through an analysis of three significant water infrastructure projects, this study identifies key drivers of governance change and evaluates the effectiveness of various stakeholder engagement mechanisms. The findings reveal how catalytic events prompted institutional innovations in addressing social impacts, environmental concerns, and climate resilience. Challenges remain in balancing diverse interests, managing implementation timeframes, and incorporating climate change uncertainties into decision-making processes. This paper offers important lessons for developing countries working to strengthen their water governance frameworks, particularly regarding stakeholder engagement, social impact mitigation, and the development of flexible institutional arrangements that can adapt to emerging climate risks. This research contributes to governance theory by demonstrating how institutional evolution occurs through the interaction of formal mechanisms and informal processes in response to changing social, environmental, and climatic conditions. Full article

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

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17 pages, 1584 KiB

Open AccessArticle

Effects of Different Irrigation Water Sources Contaminated with Heavy Metals on Seed Germination and Seedling Growth of Different Field Crops

by Ömer Süha Uslu, Osman Gedik, Ali Rahmi Kaya, Adem Erol, Emre Babur, Haroon Khan, Mahmoud F. Seleiman and Daniel O. Wasonga

Water 2025, 17(6), 892; https://doi.org/10.3390/w17060892 - 19 Mar 2025

Cited by 2 | Viewed by 634

Abstract

Irrigation water quality is of critical importance for optimum crop yield of economically important field crops in the Kahramanmaraş plains. A preliminary ecotoxicological assessment is necessary before large-scale irrigation. Therefore, this study aims to evaluate the quality of irrigation water supplied from different [...] Read more.

Irrigation water quality is of critical importance for optimum crop yield of economically important field crops in the Kahramanmaraş plains. A preliminary ecotoxicological assessment is necessary before large-scale irrigation. Therefore, this study aims to evaluate the quality of irrigation water supplied from different water sources (Karasu, Erkenez, and Oklu streams on the Aksu River and Sır Dam) and the effects on the seed germination and early seedling growth of different field crops (wheat, alfalfa, ryegrass, and maize) irrigated with this water. For this, in order to evaluate the effects on seed germination and early growth parameters of forage crop seedlings, a Petri dish germination test was carried out with four replications using a completely randomized design (CRD). Before the germination assay, heavy metal concentrations including copper (Cu), iron (Fe), lead (Pb), chromium (Cr), arsenic (As), nickel (Ni), and cadmium (Cd) were analyzed in water samples obtained from different water sources. In all water samples used for the experiment, Cu concentrations exceeded the acceptable limit of 0.2 mg L⁻¹. The Cu levels found were 0.98 mg L⁻¹ in Karasu (KC), 1.627 mg L⁻¹ in Oklu (OC), 0.945 mg L⁻¹ in Erkenez (EC), and 1.218 mg L⁻¹ in Sır Dam (SD) waters. Additionally, Fe exceeded the limit only in KC, while Cd surpassed the permissible levels in EC and SD water samples. Seeds exposed to different water treatments were germinated in a climate chamber at 20 ± 1 °C. Over two weeks, daily germination and seedling growth parameters were measured. The results indicated that higher heavy metal concentrations in irrigation water led to a decline in seed germination rates and adversely impacted early seedling growth. Notably, water from Karasu Creek exhibited the most significant negative impact on all germination and growth parameters in the tested crops, especially due to Cu and Fe metal toxicity. Additionally, ryegrass seeds were most affected by these irrigation waters. This study highlights the importance of using uncontaminated quality irrigation water for optimal crop production by quantifying its impact, such as the percentage of decrease in germination or seedling growth. Full article

(This article belongs to the Special Issue Agricultural Water-Land-Plant System Engineering)

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27 pages, 30945 KiB

Open AccessArticle

Managing Cyanobacteria Blooms in Lake Hume: Abundance Dynamics Across Varying Water Levels

by Duy Nguyen, Tapas Biswas, Janet Anstee, Phillip W. Ford and Klaus Joehnk

Water 2025, 17(6), 891; https://doi.org/10.3390/w17060891 - 19 Mar 2025

Viewed by 292

Abstract

Lake Hume, a critical reservoir within the Murray River system, Australia, has been identified as a potential source of cyanobacteria in downstream rivers during past mega-blooms. This study aims to evaluate the impact of lake-level fluctuations on cyanobacterial abundance at the dam outlets, [...] Read more.

Lake Hume, a critical reservoir within the Murray River system, Australia, has been identified as a potential source of cyanobacteria in downstream rivers during past mega-blooms. This study aims to evaluate the impact of lake-level fluctuations on cyanobacterial abundance at the dam outlets, with the goal of mitigating the risk of cyanobacteria intake from hydropower and irrigation outlets during periods of low dam levels. Utilising a one-dimensional vertical hydrodynamic model (LAKEoneD), the study simulated time series data on water temperature and stratification within Lake Hume. These outputs were then incorporated into a cyanobacteria growth model driven by water temperature, mixing dynamics and light. Despite inherent uncertainties in the models, the simulated cell counts effectively mirrored bloom occurrences. Consequently, a series of simulations across varying water levels in the lake revealed a consistent risk of significant cyanobacteria intake through both the hydropower and irrigation outlets when water levels dropped below specific thresholds. Notably, water levels below 20 m and 10 m posed heightened risks of releases of seed populations of cyanobacteria from the hydropower and irrigation outlets, respectively. Full article

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

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16 pages, 10508 KiB

Open AccessCommunication

Experimental Investigation on the Influence of Different Reservoir Water Levels on Landslide-Induced Impulsive Waves

by Anchi Shi, Jie Lei, Lei Tian, Changhao Lyu and Pengchao Mao

Water 2025, 17(6), 890; https://doi.org/10.3390/w17060890 - 19 Mar 2025

Viewed by 268

Abstract

Since the impoundment of the Baihetan Reservoir, water-involved landslides have become widespread. Existing studies on landslide-generated waves have rarely examined the impact of varying water levels on wave characteristics. This paper focuses on the Wangjiashan (WJS) landslide in the Baihetan Reservoir area of [...] Read more.

Since the impoundment of the Baihetan Reservoir, water-involved landslides have become widespread. Existing studies on landslide-generated waves have rarely examined the impact of varying water levels on wave characteristics. This paper focuses on the Wangjiashan (WJS) landslide in the Baihetan Reservoir area of China, conducting geomechanical experiments to investigate the spatiotemporal evolution of landslide-generated waves under different water level conditions. Utilizing a self-developed experimental measurement system, this study accurately records key parameters during the generation, propagation, and run-up of landslide-generated waves. It captures the complete sliding process of the WJS landslide under various water level conditions and elucidates the spatiotemporal distribution patterns of waves throughout their entire lifecycle, from generation through propagation to run-up. The research results indicate that water level factors significantly influence key parameters such as initial wave height, run-up on the opposite bank, propagation characteristics along the course, and maximum run-up in the Xiangbiling residential area. Generally, wave height initially increases and then decreases as the water level drops. Furthermore, this study offers crucial experimental data to deepen the understanding of the physical mechanisms of landslide-generated waves, advancing landslide disaster early warning technologies and enhancing the scientific accuracy and precision of landslide risk management. Full article

(This article belongs to the Special Issue Geotechnics and Geostructures Modelling for Hydrodynamic-Driven Landslides: Prediction and Control)

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30 pages, 6843 KiB

Open AccessArticle

Integrated Modeling Techniques for Understanding the Distribution and Impact of Human Activities on the Bryde’s Whale (Balaenoptera edeni) in the Sichang Islands, Thailand

by Wanchanok Umprasoet, Yongtong Mu, Chalatip Junchompoo, Zhen Guo and Zhiwei Zhang

Water 2025, 17(6), 889; https://doi.org/10.3390/w17060889 - 19 Mar 2025

Viewed by 392

Abstract

The degradation of marine and coastal resources, caused mainly by human activities, underscores the urgent need for conservation. In waters around the Sichang Islands, the Bryde’s whale is listed as an endangered marine species. The extensive human activities in this area have raised [...] Read more.

The degradation of marine and coastal resources, caused mainly by human activities, underscores the urgent need for conservation. In waters around the Sichang Islands, the Bryde’s whale is listed as an endangered marine species. The extensive human activities in this area have raised serious concerns about the possible negative influence on this species. To conserve the species effectively and efficiently, we need to understand where it distributes and how human activities influence its distribution. For this purpose, we use spatial modeling techniques alongside diverse databases encompassing various spatial and ecological factors to analyze the distribution of, and human activities’ impact on, the Bryde’s whale (Balaenoptera edeni) in the Sichang Islands, Thailand. We also use the MaxEnt model to predict habitat suitability and the result reveals key factors influencing whale occurrence across seasons. During the dry season, TSS (32.8%), chlorophyll-a (20.1%), and DO (15.9%) levels play significant roles, while DO (29.9%), NH₃ (29.4%), and distance to shore (13.3%) are crucial in the wet season. Furthermore, the Species Risk Assessment (SRA) model indicates the mooring area (14.95%) is the high-risk area for the Bryde’s Whale, particularly during the wet season. In contrast, moderate risks are observed during the dry season, notably in fishing zones (99.68%) and mooring areas (99.28%). The study also highlights that the factors mentioned above influence prey availability and habitat suitability for the Bryde’s whale and identifies potential threats posed by human activities, such as fishing and other maritime operations, that are likely to decrease water quality and prey abundance. These results are useful information for identifying sensitive areas and measures for risk mitigation, thus supporting the development of MSP or MPA plans. Full article

(This article belongs to the Special Issue Effect of Human Activities on Marine Ecosystems)

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18 pages, 3130 KiB

Open AccessArticle

A Novel Halophilic Bacterium for Sustainable Pollution Control: From Pesticides to Industrial Effluents

by Nadia Mihoubi, Samira Ferhat, Mohamed Nedjhioui, Billal Zenati, Sabrina Lekmine, Reguia Boudraa, Mohammad Shamsul Ola, Jie Zhang, Abdeltif Amrane and Hichem Tahraoui

Water 2025, 17(6), 888; https://doi.org/10.3390/w17060888 - 19 Mar 2025

Viewed by 438

Abstract

This study investigates the bioremediation potential of Marinobacter-hydrocarbonoclasticus SDK644, a strain that has been isolated from petroleum-contaminated environments, for the degradation of the herbicide metribuzin and the treatment of slaughterhouse effluent. The strain’s bacterial growth and degradation capacity were assessed under varying conditions, [...] Read more.

This study investigates the bioremediation potential of Marinobacter-hydrocarbonoclasticus SDK644, a strain that has been isolated from petroleum-contaminated environments, for the degradation of the herbicide metribuzin and the treatment of slaughterhouse effluent. The strain’s bacterial growth and degradation capacity were assessed under varying conditions, including different metribuzin concentrations, pH values, temperatures, and inoculum sizes. The strain demonstrated optimal growth at a metribuzin concentration of 20 mg/L, with an optical density (OD600) of 0.408 after 96 h. At this concentration, 80% of the chemical oxygen demand (COD) was reduced over 144 h. The optimal growth conditions for M. hydrocarbonoclasticus SDK644 were identified as a pH of 7 and a temperature of 30 °C, where the enzymatic activity and degradation efficiency were maximized. Additionally, the treatment of slaughterhouse effluent showed significant reductions in organic pollution, with the COD and biochemical oxygen demand (BOD₅) decreasing by 80% (from 1900 mg/L to 384 mg/L) and 81% (from 1700 mg/L to 320 mg/L), respectively, within seven days. The strain also facilitated ammonium removal and promoted nitrification, indicating its suitability for treating high-organic-load wastewater. Notably, the visual transformation of the effluent, from a dark red color to a clear state, further highlighted the efficiency of the treatment process. This research highlights the adaptability of M. hydrocarbonoclasticus SDK644 to a wide range of environmental conditions and its efficiency in biodegrading metribuzin and treating complex wastewater. The findings demonstrate the strain’s potential as a sustainable solution for mitigating organic pollution in agricultural runoff, pesticide-contaminated water, and industrial effluents. Full article

(This article belongs to the Special Issue Application of Biotechnology in Water Treatment and Specific Treatments for Water Reuse)

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14 pages, 10427 KiB

Open AccessArticle

Research on the Construction of an Integrated Multi-Trophic Aquaculture (IMTA) Model in Seawater Ponds and Its Impact on the Aquatic Environment

by Han Yang, Baogui Tang, Hui Zhou, Peigui Zhong and Liqiang Zhao

Water 2025, 17(6), 887; https://doi.org/10.3390/w17060887 - 19 Mar 2025

Viewed by 504

Abstract

The Integrated Multi-Trophic Aquaculture (IMTA) model is an eco-friendly aquaculture system that enhances water purification through ecological niche utilization. A study employing 16S rRNA sequencing analyzed microbial communities in aquaculture water at initial, middle, and final stages. Results indicated that physicochemical parameters were [...] Read more.

The Integrated Multi-Trophic Aquaculture (IMTA) model is an eco-friendly aquaculture system that enhances water purification through ecological niche utilization. A study employing 16S rRNA sequencing analyzed microbial communities in aquaculture water at initial, middle, and final stages. Results indicated that physicochemical parameters were lower at the final stage. The removal efficiencies of Total Nitrogen (TN) and Total Phosphorus (TP) reached 79.10% and 63.64%, respectively. The Simpson and Shannon indices revealed that microbial diversity was significantly higher in the final stage compared to the initial and middle stages (p < 0.05). Dominant bacterial phyla included Actinobacteria, Proteobacteria, and Bacteroidetes, while dominant genera included Candidatus_Aquiluna, NS3a_marine_group, and NS5_marine_group. Functional prediction results demonstrated that metabolic pathways such as amino acid metabolism, biosynthesis of other amino acids, and energy metabolism were upregulated in the final stage compared to the initial stage. Correlation analysis of environmental factors suggested that TN and TP significantly influenced the microbial community structure. Key microorganisms such as Candidatus_Aquiluna, Marinomonas, and Cobetia played crucial roles in carbon fixation, nitrogen reduction, and phosphorus removal. In summary, the IMTA model effectively purifies water, with microbial communities contributing to the stability of the aquatic environment. Full article

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13 pages, 2102 KiB

Open AccessArticle

Investigating the Effect of Iron Salts on E. coli and E. faecalis Biofilm Formation in Water Distribution Pipelines

by Sara Deumić, Ahmed El Sayed, Mahmoud Hsino, Amila Glamočak, Neira Crnčević and Monia Avdić

Water 2025, 17(6), 886; https://doi.org/10.3390/w17060886 - 19 Mar 2025

Viewed by 363

Abstract

The water distribution system is a critical infrastructure aiming to deliver safe and clean drinking water, with pipeline materials significantly influencing water quality and efficiency. One critical factor in selecting pipeline materials is the potential for biofilm formation on the inner surfaces of [...] Read more.

The water distribution system is a critical infrastructure aiming to deliver safe and clean drinking water, with pipeline materials significantly influencing water quality and efficiency. One critical factor in selecting pipeline materials is the potential for biofilm formation on the inner surfaces of pipes. This study investigates the effects of three iron salts—iron (II) sulfate heptahydrate, iron (III) nitrate nonahydrate, and iron (III) chloride on biofilm formation by Escherichia coli and Enterococcus faecalis in pipeline environments, focusing on water distribution systems. While previous research has examined the effects of iron on various bacterial species, there are limited data on E. coli and E. faecalis biofilm formation in the context of water distribution systems. Results reveal that iron (III) chloride significantly inhibited E. coli biofilm formation by up to 80%, while E. faecalis biofilm growth was promoted by iron (II) sulfate heptahydrate, with an increase of approximately 45%. These findings underscore the critical role of managing iron concentrations to mitigate biofilm-related issues, which influence water quality, infrastructure durability, and microbial resistance. The study highlights the importance of integrating these insights into sustainable water management practices and advancing pipeline material innovations to enhance public health and environmental resilience. Full article

(This article belongs to the Special Issue Sustainable Management of Water Distribution Systems)

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15 pages, 2596 KiB

Open AccessArticle

Preparation of CS/PVA/POP Nanofiber Membranes and Adsorption Behavior for Hg(II) Ions

by Qunhua Zhou, Yu Sun, Ziye Li, Siqin Sun, Jianshe Hu, Zhangpei Chen and Aikebaier Reheman

Water 2025, 17(6), 885; https://doi.org/10.3390/w17060885 - 19 Mar 2025

Viewed by 274

Abstract

Chitosan (CS) and polyvinyl alcohol (PVA) nanofiber membranes were synthesized via electrospinning and used as supporting materials for powdered porous organic polymer (POP). These membranes were then crosslinked with glutaraldehyde, resulting in nanofiber membranes (CS/PVA/POP) [...] Read more.

Chitosan (CS) and polyvinyl alcohol (PVA) nanofiber membranes were synthesized via electrospinning and used as supporting materials for powdered porous organic polymer (POP). These membranes were then crosslinked with glutaraldehyde, resulting in nanofiber membranes (CS/PVA/POP) as an efficient adsorbent for Hg(II) ions. Characterization using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy showed that the membranes effectively removed up to 92.9% of mercury ions at optimal conditions, with an adsorption capacity of 116.1 mg/g. The adsorption data fit well with the Langmuir isotherm and pseudo-second-order kinetic models. The efficient uptake of mercury ions was attributed to chemisorption involving active groups (C=S, -NH₂, -OH), facilitated by mechanisms such as chelation, complexation, or electron exchange. The CS/PVA/POP nanofiber membranes demonstrated significant advantages in adsorption capacity, economic viability, and recyclability, providing an effective solution to mercury pollution in water. Full article

(This article belongs to the Special Issue Adsorption Technologies in Wastewater Treatment Processes)

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19 pages, 8052 KiB

Open AccessArticle

Tidal-Driven Water Residence Time in the Bohai and Yellow Seas: The Roles of Different Tidal Constituents

by Qingjun Fu, Huichao Jiang, Chen Dong, Kangjie Jin, Xihan Liu and Lei Lin

Water 2025, 17(6), 884; https://doi.org/10.3390/w17060884 - 19 Mar 2025

Viewed by 250

Abstract

Water residence time (WRT) is a crucial parameter for evaluating the rate of water exchange and it serves as a timescale for elucidating hydrodynamic processes, pollutant dispersion, and biogeochemical cycling in coastal waters. This study investigates the tidal-driven WRT patterns in the Bohai [...] Read more.

Water residence time (WRT) is a crucial parameter for evaluating the rate of water exchange and it serves as a timescale for elucidating hydrodynamic processes, pollutant dispersion, and biogeochemical cycling in coastal waters. This study investigates the tidal-driven WRT patterns in the Bohai and Yellow Seas (collectively known as BYS) by employing a tidal model in conjunction with an adjoint WRT diagnostic model and explores the influence of tidal constituents on WRT. The findings indicate that the tidal-driven WRT in the BYS is approximately 2.11 years, exhibiting a significant spatially heterogeneous distribution. The WRT pattern shows a strong correlation with the pattern of tidal-driven Lagrangian residual currents (LRCs). Semidiurnal tides have a more pronounced effect on WRT than diurnal tides. Semidiurnal tides significantly reduce WRT across the entire BYS, while diurnal tides predominantly influence WRT in the Bohai Sea (BS). The M₂ tidal constituent is the most influential in decreasing WRT and enhancing water exchange, owing to its dominant energy contribution within the tidal system. In contrast, the S₂ tidal constituent has a minimal effect; however, its interaction with the M₂ tidal constituent plays a significant role in reducing the WRT. The K₁ and O₁ constituents exert more localized effects on WRT, particularly in the central BS, where their energy ratios relative to M₂ are relatively high. Although the amplitude of the S₂ constituent exceeds that of K₁ and O₁, its contribution to LRC—and consequently to WRT—is limited due to the overlapping tidal wave with M₂. This research contributes to a deeper understanding of the influence of tidal dynamics on long-term water transport and associated timescales, which are vital for enhancing predictions of material transport and ecosystem dynamics in tidal-dominated environments. Full article

(This article belongs to the Special Issue Diagnostic Timescale Methods for the Aquatic Environment: Current Challenges, Recent Improvements, and Applications)

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16 pages, 9459 KiB

Open AccessArticle

Key Calibration Strategies for Mitigation of Water Scarcity in the Water Supply Macrosystem of a Brazilian City

by Jefferson S. Rocha, José Gescilam S. M. Uchôa, Bruno M. Brentan and Iran E. Lima Neto

Water 2025, 17(6), 883; https://doi.org/10.3390/w17060883 - 19 Mar 2025

Viewed by 336

Abstract

This study focuses on Fortaleza, the largest metropolis in Brazil’s semi-arid region. Due to recurrent droughts, massive infrastructure like high-density reservoir networks, inter-municipal and interstate water transfer systems, and a seawater desalination plant have been implemented to ensure the city’s water security. To [...] Read more.

This study focuses on Fortaleza, the largest metropolis in Brazil’s semi-arid region. Due to recurrent droughts, massive infrastructure like high-density reservoir networks, inter-municipal and interstate water transfer systems, and a seawater desalination plant have been implemented to ensure the city’s water security. To evaluate the quantitative and qualitative impact of introducing these diverse water sources into Fortaleza’s water supply macrosystem, adequate calibration of the operating and demand parameters is required. In this study, the macrosystem was calibrated using the Particle Swarm Optimization (PSO) method based on hourly data from 50 pressure head monitoring points and 40 flow rate monitoring points over two typical operational days. The calibration process involved adjusting the operational rules of typical valves in large-scale Water Distribution Systems (WDS). After parameterization, the calibration presented the following results: R² of 88% for pressure head and 96% for flow rate, with average relative errors of 13% for the pressure head and flow rate. In addition, with NSE values above 0.80 after calibration for the flow rate and pressure head, the PSO method suggests a significant improvement in the simulation model’s performance. These results offer a methodology for calibrating real WDS to simulate various water injection scenarios in the Fortaleza macrosystem. Full article

(This article belongs to the Special Issue Advances in Management and Optimization of Urban Water Networks)

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16 pages, 11814 KiB

Open AccessArticle

Performance and Mechanism of a Novel Composite Ecological Ditch System for Nitrogen and Phosphorus Interception in Agricultural Drainage

by Xin Wu, Chaohui Chen, Zijiang Yang, Xiangjian Zheng, Tianyi Chen, Yongtao Li, Xueming Lin, Zheng Hu, Kerun Ren and Zhen Zhang

Water 2025, 17(6), 882; https://doi.org/10.3390/w17060882 - 19 Mar 2025

Viewed by 339

Abstract

The massive loss of nitrogen (N) and phosphorus (P) from farmland ditches contributes to non-point source pollution, posing a significant global environmental challenge. Effectively removing these nutrients remains difficult in intensive agricultural systems. To address this, a novel composite ecological ditch system (CEDS) [...] Read more.

The massive loss of nitrogen (N) and phosphorus (P) from farmland ditches contributes to non-point source pollution, posing a significant global environmental challenge. Effectively removing these nutrients remains difficult in intensive agricultural systems. To address this, a novel composite ecological ditch system (CEDS) was developed by modifying traditional drainage ditches to integrate a grit chamber, zeolite, and ecological floating beds. Dynamic monitoring of N and P levels in water, plants, and zeolite was conducted to evaluate the system’s nutrient interception performance and mechanisms. The results showed the following: (1) Water quality improved markedly after passing through the CEDS, with nutrient concentrations decreasing progressively along the flow path. The system intercepted 41.0% of N and 31.9% of P, with inorganic N and particulate P as the primary forms of nutrient loss. (2) Zeolite removes N primarily through ion exchange, and P likely through chemical reactions, with maximum capacities of 3.47 g/kg for N and 1.83 g/kg for P. (3) Ecological floating beds with hydroponic cultivation enhanced nutrient uptake by the roots of Canna indica and Iris pseudacorus, with N uptake surpassing P. (4) Nutrient interception efficiency was positively correlated with temperature, ditch inlet concentrations, and rice runoff concentrations, but negatively with precipitation. This study demonstrates the CEDS’s potential for improving farmland water quality and suggests further enhancements in design and management to increase its economic and aesthetic value. Full article

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16 pages, 10012 KiB

Open AccessArticle

Ball-Milled Spent Coffee Ground Biochar Effectively Removes Caffeine from Water

by Yicheng Yang, Yongshan Wan, Jianjun Chen, Hao Chen, Yuncong Li, Rafael Muñoz-Carpena, Yulin Zheng, Jinsheng Huang, Yue Zhang and Bin Gao

Water 2025, 17(6), 881; https://doi.org/10.3390/w17060881 - 19 Mar 2025

Viewed by 497

Abstract

Caffeine in aquatic ecosystems is an emerging contaminant causing significant environmental concern. In this work, spent coffee ground (SCG) was pyrolyzed at 300, 450, and 600 °C to produce pristine SCG biochars (CG), which were then ball-milled to produce ball-milled SCG biochars (BMCG). [...] Read more.

Caffeine in aquatic ecosystems is an emerging contaminant causing significant environmental concern. In this work, spent coffee ground (SCG) was pyrolyzed at 300, 450, and 600 °C to produce pristine SCG biochars (CG), which were then ball-milled to produce ball-milled SCG biochars (BMCG). A batch experiment with ball-milled and pristine biochars showed that ball-milled biochars pyrolyzed at 450 °C and 600 °C had the highest capacities to adsorb caffeine. Subsequently, ball-milled CG450 (BMCG450) was selected for further analysis. The results showed that ball milling dramatically augmented the specific surface area and oxygen-containing functional groups of the biochar. The Langmuir maximum caffeine adsorption capacity was 82.65 mg/g. Both solution pH and ionic strength affected caffeine removal by BMCG450. As pH increased, increased electrostatic repulsion limited caffeine adsorption onto the biochar. However, an increase in ion strength slightly enhanced caffeine adsorption because of the electrostatic screening effect of cations. The ball-milled SCG biochar also showed high adsorption efficiency in a completely mixed flow reactor under continuous flow conditions. Our study indicates that ball-milled SCG biochar at 450 °C can serve as a viable sorbent for the removal of caffeine from water. Full article

(This article belongs to the Special Issue Emerging Micropollutants: Challenges and Solutions in Detection and Treatment)

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33 pages, 13386 KiB

Open AccessArticle

Ground–Surface Water Assessment for Agricultural Land Prioritization in the Upper Kansai Basin, India: An Integrated SWAT-VIKOR Framework Approach

by Sudipto Halder, Santanu Banerjee, Youssef M. Youssef, Abhilash Chandel, Nassir Alarifi, Gupinath Bhandari and Mahmoud E. Abd-Elmaboud

Water 2025, 17(6), 880; https://doi.org/10.3390/w17060880 - 19 Mar 2025

Cited by 1 | Viewed by 647

Abstract

Prioritizing agricultural land use is a significant challenge for sustainable development in the rapidly urbanizing, semi-arid riverine basins of South Asia, especially under climate variability and water scarcity. This study introduces a systematic framework combining remote sensing and geospatial data with the Soil [...] Read more.

Prioritizing agricultural land use is a significant challenge for sustainable development in the rapidly urbanizing, semi-arid riverine basins of South Asia, especially under climate variability and water scarcity. This study introduces a systematic framework combining remote sensing and geospatial data with the Soil and Water Assessment Tool (SWAT) model, morphometric analysis, and VIKOR-based Multi-Criteria Decision Analysis (MCDA) to effectively identify Agricultural Land Prioritization (AgLP) areas in the Upper Kansai Basin, India, while reducing the environmental impact, in line with Sustainable Development Goals (SDGs). The SWAT model simulation reveals varied hydrological patterns, with basin water yields from 965.9 to 1012.9 mm and a substantial baseflow (~64% of total flow), emphasizing essential groundwater–surface water interactions for sustainable agriculture. However, the discrepancy between percolation (47% of precipitation) and deep recharge (2% of precipitation) signals potential long-term groundwater challenges. VIKOR analysis offers a robust prioritization framework, ranking SW4 as the most suitable (Qi = 0.003) for balanced hydrological and morphometric features, in agreement with the SWAT outcomes. SW4 and SW5 display optimal agricultural conditions due to stable terrain, effective water retention, and favorable morphometric traits (drainage density 3.0–3.15 km/km²; ruggedness 0.3–0.4). Conversely, SW2, with high drainage density (5.33 km/km²) and ruggedness (2.0), shows low suitability, indicating risks of erosion and poor water retention. This integrated AgLP framework advances sustainable agricultural development and supports SDGs, including SDG 2 (Zero Hunger), SDG 6 (Clean Water), SDG 13 (Climate Action), and SDG 15 (Life on Land). Incorporating hydrological dynamics, land use, soil properties, and climate variables, this approach offers a precise assessment of agricultural suitability to address global sustainability challenges in vulnerable riverine basins of developing nations. Full article

(This article belongs to the Special Issue Field Monitoring, GIS, Remote Sensing, Geophysical Techniques, and Hydrochemical Analysis in Groundwater Investigations)

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