Water

17 pages, 1340 KiB

Open AccessArticle

Optimizing the Arrangement of Semi-Cylindrical Structures for Bank Protection Effectiveness Using the Multi-Objective Genetic Algorithm

by Maomei Wang, Liangzhen Hong, Hongwei Wang, Lian Wang, Hongguang Sun and Jun Cai

Water 2025, 17(9), 1360; https://doi.org/10.3390/w17091360 (registering DOI) - 30 Apr 2025

Abstract

To address the problem of concave bank scour in a 120° bend river, this study designed and explored the bank protection effect of different arrangements of semi-cylinder sandbags. Based on the actual riverbed structure, a simplified geometric model of the bend riverbed was [...] Read more.

To address the problem of concave bank scour in a 120° bend river, this study designed and explored the bank protection effect of different arrangements of semi-cylinder sandbags. Based on the actual riverbed structure, a simplified geometric model of the bend riverbed was constructed, and the bank protection effect of sandbags arranged at different angles and spacings under different flow conditions was evaluated by using a multi-objective genetic algorithm (MOGA). The optimization results showed that the net sediment mass flow rate of the riverbed in the curved riverbed model using one semi-cylinder sandbag was maximum when the angle between the semi-cylinder sandbag and the concave bank of the riverbed was 158°. Further, the results of the analyses of velocity and spacing indicated that the effect of inlet flow velocity on the effectiveness of bank protection is 1.5 times greater than the spacing of the throw pillows in a bend channel with two semi-cylindrical sandbags. In the conventional flow velocity range of 1~2 m/s, the net sediment mass flow rate in the riverbed is the largest when the throw pillow distance is set at 49 m, which is about 9.4 kg/s, which can provide a better bank protection effect and can provide a certain reference for the design of engineering bank protection. Full article

(This article belongs to the Section Water Erosion and Sediment Transport)

17 pages, 3284 KiB

Open AccessArticle

Vertical Binding Characteristics Between Dissolved Organic Matter and Heavy Metals in the Upper Reaches of the Yangtze River Using EEM-PARAFAC and 2D-FTIR-COS

by Xihuan Wang, Tiansen Zou, Weibo Zhang, Yili Fan and Yingchen Bai

Water 2025, 17(9), 1359; https://doi.org/10.3390/w17091359 (registering DOI) - 30 Apr 2025

Abstract

Dissolved organic matter (DOM) exerts a significant influence on the environmental behavior of heavy metals in water. This study investigated the spatial distribution characteristics of DOM in the upper reaches of the Yangtze River and its vertical (0–10 m) binding behavior with heavy [...] Read more.

Dissolved organic matter (DOM) exerts a significant influence on the environmental behavior of heavy metals in water. This study investigated the spatial distribution characteristics of DOM in the upper reaches of the Yangtze River and its vertical (0–10 m) binding behavior with heavy metals. The results indicated that humic acid-like substances dominated the DOM composition in the river water, exhibiting spatial variability horizontally, with a higher proportion of protein-like components observed at the depth of 8 m. The DOM showed complexation affinity (LogK) values were 4.71–6.38 for Cu²⁺ and 4.27–6.26 for Hg²⁺, with the protein-like component C3 exhibiting higher LogK values when binding with Cu²⁺ or Hg²⁺ compared to humic-like components. The LogK_Cu and LogK_Hg varied distinctly with water depth, and at 8 m depth, humus-like component C1 exhibited stronger binding affinity for Hg²⁺, whereas protein-like component C3 showed greater affinity for Cu²⁺. The 2D-FTIR-COS analysis revealed that, in the DOM-Cu complexes, DOM from surface water preferentially bound to O-H groups of carbohydrates, phenols, and carboxylic acids, while deep water DOM favored C=O groups in amides; for DOM–Hg complexes, the active binding sites varied distinctly with depth. This study provides novel insights into the migration and transformation mechanisms of heavy metals in rivers. Full article

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

21 pages, 4287 KiB

Open AccessArticle

Towards Participatory River Governance Through Citizen Science

by Natalia Alvarado-Arias, Julián Soria-Delgado, Jacob Staines and Vinicio Moya-Almeida

Water 2025, 17(9), 1358; https://doi.org/10.3390/w17091358 (registering DOI) - 30 Apr 2025

Abstract

The concept of a “water governance crisis” manifests distinctly across different regions. In the Global South, particularly in rapidly urbanizing cities, innovative governance models that incorporate community participation are critically needed to address unique challenges such as informal settlements and less stringent pollution [...] Read more.

The concept of a “water governance crisis” manifests distinctly across different regions. In the Global South, particularly in rapidly urbanizing cities, innovative governance models that incorporate community participation are critically needed to address unique challenges such as informal settlements and less stringent pollution controls. This paper presents a theoretical and methodological approach, emphasizing citizen science and community engagement in urban water management. It explores how engaging communities in the assessment and management of water bodies not only enhances the identification of priority areas but also strengthens local capacities to address environmental challenges. An analytical framework highlighting the interdependence between valuation languages and citizen science supports the development of management models for degraded hydro-social territories. Utilizing a mixed-methods approach, this research develops social indicators and applies participatory methodologies, such as Participatory Mapping, demonstrated through a study of four urban rivers in Sangolquí, Ecuador: Santa Clara, San Pedro, Pita, and San Nicolás. Our findings reveal that participatory models are more effective than traditional technocratic hierarchies and underscore a new paradigm for water governance that prioritizes local knowledge and community practices. This study not only reveals the ecological, social, and spatial configurations of urban river landscapes in Sangolquí but also suggests the framework’s applicability to other Latin American cities facing similar challenges. Full article

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

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17 pages, 3487 KiB

Open AccessArticle

The Efficacy of a Novel Selection of Bacillus spp. on Reducing Off-Flavor Compounds and Improving Flesh Quality

by Tianyu Liu, Nattida Boonpeng, Kang Li, Li Yan, Justice Frimpong Amankwah, Kriengkrai Satapornvanit, Russell Borski and Liping Liu

Water 2025, 17(9), 1357; https://doi.org/10.3390/w17091357 (registering DOI) - 30 Apr 2025

Abstract

Geosmin (GSM) and 2-methylisoborneol (2-MIB), microbial-derived terpenoid compounds prevalent in aquaculture systems, impair fillet quality and disrupt physiological homeostasis in aquatic species by inducing oxidative stress and lipid peroxidation. Despite their significant impact, effective strategies for eliminating these compounds from fish tissues remain [...] Read more.

Geosmin (GSM) and 2-methylisoborneol (2-MIB), microbial-derived terpenoid compounds prevalent in aquaculture systems, impair fillet quality and disrupt physiological homeostasis in aquatic species by inducing oxidative stress and lipid peroxidation. Despite their significant impact, effective strategies for eliminating these compounds from fish tissues remain underexplored. In this study, we employed primer-mediated PCR amplification to identify strains that produce 2-MIB and GSM and evaluated the efficacy of Bacillus licheniformis strain BL23 (BL23) in suppressing S. thermocarboxydus (ST), a key contributor to terpenoid synthesis. Experimental fish were allocated to three groups (n = 30 per group): Group C (control, standard feed), Group T1 (BL23-supplemented feed), and Group T2 (BL23 + ST coculture). Probiotic concentrations in the tanks were maintained at 10⁶ CFU/mL under controlled conditions (30 °C). Tissue and aqueous samples were collected at intervals for the analysis of texture, growth performance, and terpenoid concentrations, with measurements in triplicate. Subsequently, B. licheniformis strain BL23 (BL23), which exhibits inhibitory effects against S. thermocarboxydus (ST) growth, was cultured and introduced into both fish specimens and aqueous systems. The outcomes of strain inoculation and cultivation experiments demonstrated the emergence of an inhibition zone surrounding the actinomycetes inoculated with BL23. The results from liquid coculture assays revealed a reduction in the concentration of ST from 10⁶ CFU/mL at 48 h to 10¹ CFU/mL at 72 h post-coculture with BL23 for an initial 48 h period. An analysis of fish tissue and aqueous samples confirmed that BL23 exhibited a significant inhibitory effect on the growth of ST, leading to a substantial decrease in GSM content (p < 0.05). However, no statistically significant improvements were observed in fish growth performance (weight gain, feed conversion rate) or meat texture quality parameters (hardness, elasticity). These findings present a novel approach to mitigating geosmin-induced off-flavors in aquaculture products, highlighting its potential utility in water management and aquatic food production systems. The results are particularly pertinent for the development of biological control strategies targeting microbial-derived odorants in recirculating aquaculture systems. Full article

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

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13 pages, 4733 KiB

Open AccessArticle

Groundwater Suitability Mapping in Jimma and Borena Zones of Ethiopia Using GIS and Remote Sensing Techniques

by Geteneh Moges Assefa, Frehiwot Derbe Abay, Genetu Addisu Kebede and Sintayehu Abebe

Water 2025, 17(9), 1356; https://doi.org/10.3390/w17091356 (registering DOI) - 30 Apr 2025

Abstract

Groundwater is a vital resource in arid and semi-arid regions, such as Ethiopia’s Jimma and Borena zones, where surface water availability is limited. This study employs Geographic Information Systems (GIS), Remote Sensing (RS), and the Analytical Hierarchy Process (AHP) to delineate groundwater potential [...] Read more.

Groundwater is a vital resource in arid and semi-arid regions, such as Ethiopia’s Jimma and Borena zones, where surface water availability is limited. This study employs Geographic Information Systems (GIS), Remote Sensing (RS), and the Analytical Hierarchy Process (AHP) to delineate groundwater potential zones. Key hydrogeological parameters, including lithology, slope, land use/land cover, drainage density, and recharge, were analyzed and weighted using the AHP to generate suitability maps. The findings indicate that in Jimma, 4.6% of the area is highly suitable for groundwater development, 24% is moderately suitable, and 70% has low suitability. In Borena, 6.2% of the area is highly suitable, 42.6% is moderately suitable, and 51.1% exhibits low suitability due to topographic and geological constraints. Validation using borehole data confirms the model’s reliability, demonstrating strong agreement with observed groundwater yields. These results provide a cost-effective approach for groundwater exploration and highlight the necessity of geophysical surveys in complex terrains to enhance mapping accuracy. This study offers valuable insights for water resource planners and policymakers, supporting sustainable groundwater management strategies in the region. Full article

(This article belongs to the Section Hydrology)

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38 pages, 3533 KiB

Open AccessArticle

Sea-Level Rise and Saltwater Intrusion: Economic Estimates of Impacts of Nature-Based Mitigation Policies Under Uncertainty

by Dat Q. Tran and Kieu N. Le

Water 2025, 17(9), 1355; https://doi.org/10.3390/w17091355 (registering DOI) - 30 Apr 2025

Abstract

Increased saltwater intrusion likely causes a significant reduction in food production in alluvial river deltas worldwide. One of the mitigation measures for saltwater intrusion is to increase natural flow through irrigation water conservation and land-fallowing policies to prevent the saltwater from moving further [...] Read more.

Increased saltwater intrusion likely causes a significant reduction in food production in alluvial river deltas worldwide. One of the mitigation measures for saltwater intrusion is to increase natural flow through irrigation water conservation and land-fallowing policies to prevent the saltwater from moving further inland. However, economic estimates of the costs of such measures under uncertainty are scant. Herein, we develop an integrated modeling framework for estimating the costs of saltwater intrusion mitigation policies by 2050 in the Mekong Delta. The integrated model combines hydrodynamic, advection-dispersion, statistical, crop yield, and economic models, thus allowing us to account for the risk and uncertainty of saltwater intrusion and the costs of mitigation policies. We found that a 95% confidence interval of the saltwater intrusion-impacted area is estimated to be 186,000–201,000 hectares for the baseline, 193,000–209,000 hectares for a sea level rise of 22 cm, and 204,000–219,000 hectares for a sea level rise of 53 cm scenarios, respectively. To bring the saltwater intrusion under the sea level rise of 22 cm back to the baseline level, 100,000–150,000 hectares of currently cultivated rice would need to be fallowed at least once a year. This is equivalent to annual economic losses, with a 50% chance, ranging from $100.03–$176.67 million, implying a substantial economic cost of sea level rise-induced saltwater intrusion even under a modest sea level rise scenario. Under the sea level rise of 53 cm scenario, the results show that widespread adoption of alternate wetting and drying and approximately 300,000 ha of land-fallowing would be needed to push saltwater intrusion back to the baseline level. The findings indicate that saltwater intrusion in the Mekong Delta is more likely than not to intensify considerably and is much less predictable, posing a greater risk to one of the most important rice-producing regions in the world. Full article

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

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28 pages, 2480 KiB

Open AccessArticle

Sustainable Water-Related Hazards Assessment in Open Pit-to-Underground Mining Transitions: An IDRR and MCDM Approach at Sijiaying Iron Mine, China

by Aboubakar Siddique, Zhuoying Tan, Wajid Rashid and Hilal Ahmad

Water 2025, 17(9), 1354; https://doi.org/10.3390/w17091354 (registering DOI) - 30 Apr 2025

Abstract

The transition from open pit to underground mining intensifies water-related hazards such as Acid Mine Drainage (AMD), groundwater contamination, and aquifer depletion, threatening ecological and socio-economic sustainability. This study develops an Inclusive Disaster Risk Reduction (IDRR) framework using a Multi-Dimensional Risk (MDR) approach [...] Read more.

The transition from open pit to underground mining intensifies water-related hazards such as Acid Mine Drainage (AMD), groundwater contamination, and aquifer depletion, threatening ecological and socio-economic sustainability. This study develops an Inclusive Disaster Risk Reduction (IDRR) framework using a Multi-Dimensional Risk (MDR) approach to holistically assess water hazards in China’s mining regions, integrating environmental, social, governance, economic, technical, community-based, and technological dimensions. A Multi-Criteria Decision-Making (MCDM) model combining the Fuzzy Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) evaluates risks, enhanced by a Z-number Fuzzy Delphi AHP (ZFDAHP) spatiotemporal model to dynamically weight hazards across temporal (short-, medium-, long-term) and spatial (local to global) scales. Applied to the Sijiaying Iron Mine, AMD (78% severity) and groundwater depletion (72% severity) emerge as dominant hazards exacerbated by climate change impacts (36.3% dynamic weight). Real-time IoT monitoring systems and AI-driven predictive models demonstrate efficacy in mitigating contamination, while gender-inclusive governance and community-led aquifer protection address socio-environmental gaps. The study underscores the misalignment between static regulations and dynamic spatiotemporal risks, advocating for Lifecycle Assessments (LCAs) and transboundary water agreements. Policy recommendations prioritize IoT adoption, carbon–water nexus incentives, and Indigenous knowledge integration to align mining transitions with Sustainable Development Goals (SDGs) 6 (Clean Water), 13 (Climate Action), and 14 (Life Below Water). This research advances a holistic strategy to harmonize mineral extraction with water security, offering scalable solutions for global mining regions facing similar ecological and governance challenges. Full article

(This article belongs to the Special Issue Inclusive Disaster Risk Reduction: Gender, Community-Based Approaches, and Local Governance in Mitigating Water-Related Hazards)

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26 pages, 7811 KiB

Open AccessArticle

In Situ Hyperspectral Reflectance Sensing for Mixed Water Quality Monitoring: Insights from the RUT Agricultural Irrigation District

by Jhony Armando Benavides-Bolaños, Andrés Fernando Echeverri-Sánchez, Aldemar Reyes-Trujillo, María del Mar Carreño-Sánchez, María Fernanda Jaramillo-Llorente and Juan Pablo Rivera-Caicedo

Water 2025, 17(9), 1353; https://doi.org/10.3390/w17091353 (registering DOI) - 30 Apr 2025

Abstract

Water-quality monitoring in agricultural irrigation systems is challenging due to the dynamic and heterogeneous nature of mixed water sources, which complicates traditional and remote sensing-based assessment methods. Traditional water quality monitoring relies on water sampling and laboratory analysis, which can be time-consuming, labor-intensive, [...] Read more.

Water-quality monitoring in agricultural irrigation systems is challenging due to the dynamic and heterogeneous nature of mixed water sources, which complicates traditional and remote sensing-based assessment methods. Traditional water quality monitoring relies on water sampling and laboratory analysis, which can be time-consuming, labor-intensive, and spatially limited. In situ hyperspectral reflectance sensing (HRS) presents a promising alternative, offering high-resolution, non-invasive monitoring capabilities. However, applying HRS in mixed-water environments—where served-water effluent, precipitation, and natural river water converge—presents significant challenges due to variability in water composition and environmental conditions. While HRS has been widely explored in controlled or homogeneous water bodies, its application in highly dynamic agricultural mixed-water systems remains understudied. This study addresses this gap by evaluating the relationships between in situ hyperspectral data (450–900 nm) and key water-quality parameters—pH, turbidity, nitrates, and chlorophyll-a—across three campaigns in a Colombian tropical agricultural irrigation system. A Pearson’s correlation analysis revealed the strongest spectral associations for nitrates, with positive correlations at 500 nm (r ≈ 0.76) and 700 nm (r ≈ 0.85) and negative correlations in the near-infrared (850 nm, r ≈ −0.88). Conversely, the pH exhibited weak and diffuse correlations, with a maximum of r ≈ 0.51. Despite their optical activity, turbidity and chlorophyll-a showed unexpectedly weak correlations, likely due to the optical complexity of the mixed water matrix. Random Forest regression identified key spectral regions for each parameter, yet model performance was limited, with R² values ranging from 0.51 (pH) to −1.30 (chlorophyll-a), and RMSE values between 0.41 and 1.51, reflecting the challenges of predictive modeling in spatially and temporally heterogeneous wastewater systems. Despite these challenges, this study establishes a baseline for future hyperspectral applications in complex agricultural water monitoring and highlights critical spectral regions for further investigation. To improve the feasibility of HRS in mixed-water assessments, future research should focus on enhancing data-preprocessing techniques, integrating complementary sensing modalities, and refining predictive models to better account for environmental variability. Full article

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

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23 pages, 3954 KiB

Open AccessArticle

Testing Macrophyte-Based Assessment Tools Developed Under the EU Water Framework Directive for Application in a Caucasus Region Country (Armenia)

by Hermine Yepremyan, Vardan Asatryan, Marine Dallakyan, Gayane Shahnazaryan and Martin Pusch

Water 2025, 17(9), 1352; https://doi.org/10.3390/w17091352 (registering DOI) - 30 Apr 2025

Abstract

The UN framework of “Integrated Water Resources Management” recommends countries establish a sustainable management of their water resources, which relies on the availability of proper assessment indexes for the ecological status of surface waters. Such indexes have been developed by many EU countries [...] Read more.

The UN framework of “Integrated Water Resources Management” recommends countries establish a sustainable management of their water resources, which relies on the availability of proper assessment indexes for the ecological status of surface waters. Such indexes have been developed by many EU countries under the EU Water Framework Directive. Non-EU countries may be interested in adapting such assessment tools. Hence, we describe here a test of three macrophyte-based assessment tools developed in EU countries for use in Armenia. All three indices were tested in a regionally adapted version where local species were entered into reference taxonomic lists, river types were assigned, and matching exercises of the results with benthic macroinvertebrates and physical and chemical parameters of the rivers were performed. The results show that the three tested assessment tools produced similar spatial patterns of ecological status changes, while the adapted version of the MTR index had the highest number of significant correlations with various metrics of macrozoobenthos and hydro-chemical parameters. We conclude that assessment scores for rivers based on macrophytes can be used for rivers of the Caucasus after regional adaptation of the reference macrophyte list. We recommend that the modified MTR index be introduced into the national hydrobiological system of Armenia after some additional adaptations. Full article

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

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23 pages, 14196 KiB

Open AccessArticle

Application of Deep Learning and Geospatial Analysis in Soil Loss Risk in the Moulouya Watershed, Morocco

by Mohammed Hlal, Bilal El Monhim, Jérôme Chenal, Jean-Claude Baraka Munyaka, Rida Azmi, Abdelkader Sbai, Gary Cwick and Badr Ben Hichou

Water 2025, 17(9), 1351; https://doi.org/10.3390/w17091351 (registering DOI) - 30 Apr 2025

Abstract

This study integrates deep learning and geospatial analysis to enhance soil loss estimation in the Moulouya Watershed, a region prone to erosion due to diverse topography and climatic conditions. Traditional models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE) [...] Read more.

This study integrates deep learning and geospatial analysis to enhance soil loss estimation in the Moulouya Watershed, a region prone to erosion due to diverse topography and climatic conditions. Traditional models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE) often fall short in capturing complex environmental interactions, leading to inaccurate soil loss predictions. This research introduces a novel approach using Convolutional Neural Networks (CNNs) combined with Geographic Information Systems (GISs) to improve the precision and spatial resolution of soil loss risk assessments. High-resolution satellite imagery, soil maps, and climatic data were processed to extract critical factors, such as slope, land cover, and rainfall erosivity, which were then fed into the CNN model. The findings revealed that the CNN model outperformed traditional methods, achieving a low Root Mean Square Error (RMSE) of 2.3 and an R-squared value of 0.92, significantly surpassing the USLE and RUSLE models. The resulting high-resolution soil loss maps identified high-risk erosion areas, particularly in the central and eastern regions of the watershed, with soil loss rates exceeding 40 tons/ha/year. These findings demonstrate the superior predictive capabilities of deep learning, offering valuable insights for targeted soil conservation strategies and highlighting the potential of advanced computational techniques to revolutionize environmental modeling. Full article

(This article belongs to the Special Issue Bridging the Gaps: Hydrological Research for Sustainable River Management)

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14 pages, 4983 KiB

Open AccessArticle

Assessment of per Capita Contribution to Fecal Sewage in Rural Residences of Quilombola Communities

by Adivânia Cardoso da Silva, Paulo Sérgio Scalize and António Albuquerque

Water 2025, 17(9), 1350; https://doi.org/10.3390/w17091350 (registering DOI) - 30 Apr 2025

Abstract

The universalization of basic sanitation remains a challenge. For the development of sanitation infrastructure projects, it is essential to use water consumption data that accurately reflect reality, ensuring greater precision. This study aimed to determine the per capita contribution to fecal sewage (Cp) [...] Read more.

The universalization of basic sanitation remains a challenge. For the development of sanitation infrastructure projects, it is essential to use water consumption data that accurately reflect reality, ensuring greater precision. This study aimed to determine the per capita contribution to fecal sewage (Cp) in six quilombola residences in Goiás (Brazil). The research was conducted in two phases: (a) a literature review on Cp in similar communities (CpL) and (b) the determination of Cp in six residences from different rural communities (CpP), varying in the number of inhabitants (8, 8, 5, 2, 1, and 1 persons in households R1 to R6, respectively). Flow measurements were obtained using a volumetric flowmeter (nominal flow rate of 1.5 m³/h) installed in the water pipeline supplying the toilet(s) of each household. A dearth of Cp data was observed in the literature, particularly for rural areas. Research on this topic remains in its infancy, as evidenced by the small number of publications (nine papers) published between 2006 and 2022, of which 44.4% reported on-site measurements. In the present study, the CpP ranged from 12.10 L/cap.day to 21.79 L/cap.day, with a mean of 16.22 L/cap.day (CV = 0.239). These calculated values lie within the lower (9.9 L/cap.day) and upper (51.5 L/cap.day) ranges reported in the literature. Generally, estimated data are higher than values calculated from flowrate measurements, highlighting the importance of direct measurements—which can also help reduce construction costs. Therefore, it is recommended that flowrate measurements and Cp calculations be expanded to residences with diverse demographic and geographic characteristics, also incorporating meteorological data, to obtain more accurate results. Full article

(This article belongs to the Special Issue Exposure, Ecological Effects and Risk Assessment of Emerging Contaminants in Water Environment)

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26 pages, 9639 KiB

Open AccessArticle

Hydrochemical Characteristics and Evolution Laws of Groundwater in Huangshui River Basin, Qinghai

by Ziqi Wang, Ting Lu, Shengnan Li, Kexin Zhou, Yidong Gu, Bihui Wang and Yudong Lu

Water 2025, 17(9), 1349; https://doi.org/10.3390/w17091349 (registering DOI) - 30 Apr 2025

Abstract

Groundwater plays a leading role in ecological environment protection in semi-arid regions. The Huangshui River Basin is located in the Tibetan Plateau and Loess Plateau transition zone of semi-arid areas. Its ecological environment is relatively fragile, and there is an urgent need for [...] Read more.

Groundwater plays a leading role in ecological environment protection in semi-arid regions. The Huangshui River Basin is located in the Tibetan Plateau and Loess Plateau transition zone of semi-arid areas. Its ecological environment is relatively fragile, and there is an urgent need for systematic study of the basin to develop a groundwater environment and realize the rational and efficient development of water resources. In this study, methodologically, we combined the following: 1. Field sampling (271 groundwater samples across the basin’s hydrogeological units); 2. Comprehensive laboratory analysis of major ions and physicochemical parameters; 3. Multivariate statistical analysis (Pearson correlation, descriptive statistics); 4. Geospatial techniques (ArcGIS kriging interpolation); 5. Hydrochemical modeling (Piper diagrams, Gibbs plots, PHREEQC simulations). Key findings reveal the following: 1. Groundwater is generally weakly alkaline (pH 6.94–8.91) with TDS ranging 155–10,387 mg/L; 2. Clear spatial trends: TDS and major ions (Na⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻) increase along flow paths; 3. Water types evolve from Ca-HCO₃-dominant (upper reaches) to complex Ca-SO₄/Ca-Cl mixtures (lower reaches); 4. Water–rock interactions dominate hydrochemical evolution, with secondary cation exchange effects; 5. PHREEQC modeling identifies dominant carbonate dissolution (mean SIcalcite = −0.32) with localized evaporite influences (SIgypsum up to 0.12). By combining theoretical calculations and experimental results, this study reveals distinct hydrochemical patterns and evolution mechanisms. The groundwater transitions from Ca-HCO₃-type in upstream areas to complex Ca-SO₄/Cl mixtures downstream, driven primarily by dissolution of gypsum and carbonate minerals. Total dissolved solids increase dramatically along flow paths (155–10,387 mg/L), with Na⁺ and SO₄²⁻ showing the strongest correlation to mineralization (r > 0.9). Cation exchange processes and anthropogenic inputs further modify water chemistry in midstream regions. These findings establish a baseline for sustainable groundwater management in this ecologically vulnerable basin. Full article

(This article belongs to the Special Issue Dynamic Response of Water and Soil Resources in the Context of Climate Change and Human Activities)

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14 pages, 4280 KiB

Open AccessArticle

Dynamic Microstructural Changes in Bentonite During Hydration: A Micro-CT Investigation

by Kui Liu, Jing Hu, Quanchang Zhang and Chaofeng Zeng

Water 2025, 17(9), 1348; https://doi.org/10.3390/w17091348 (registering DOI) - 30 Apr 2025

Abstract

Bentonite is widely used as an engineering barrier in radioactive waste disposal. This study examined the hydromechanical behavior and microstructural evolution of a bentonite mixture under controlled hydration, utilizing real-time X-ray micro-CT imaging to capture transitions from granular to dense homogeneous states. The [...] Read more.

Bentonite is widely used as an engineering barrier in radioactive waste disposal. This study examined the hydromechanical behavior and microstructural evolution of a bentonite mixture under controlled hydration, utilizing real-time X-ray micro-CT imaging to capture transitions from granular to dense homogeneous states. The results demonstrated that, during the early stages of hydration, bentonite pellets experienced substantial swelling, filling inter-pellet voids and transforming from a loosely packed granular structure to a compact, homogeneous matrix. This transformation significantly reduced the porosity from an initial value of 20% to below 0.1% after 60 days, thereby substantially lowering the material’s permeability. Particle displacement analysis, employing digital image correlation techniques, revealed axial displacements of up to 2.6 mm and radial displacements of up to 0.9 mm, highlighting pronounced void closure and structural reorganization. The study also examined the influence of initial dry density heterogeneities on swelling pressure and permeability, providing insights for optimizing barrier design. The findings affirm that hydrated bentonite serves as a highly effective low-permeability barrier for sealing deep geological repositories. Its capacity for environmental adaptation, demonstrated through self-healing and densification, further reinforces its suitability for critical and long-term engineering applications. Full article

(This article belongs to the Special Issue Recent Advances in Groundwater Control in Geotechnical Engineering)

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29 pages, 7299 KiB

Open AccessArticle

Application of Transformer-Based Deep Learning Models for Predicting the Suitability of Water for Agricultural Purposes

by K. Rejini, J. Visumathi and C. Heltin Genitha

Water 2025, 17(9), 1347; https://doi.org/10.3390/w17091347 - 30 Apr 2025

Abstract

Water is the most vital component for the sustainability of living beings on Earth. From plants to human beings, every single living being on Earth needs water for its survival. In this research, a novel model has been developed in order to predict [...] Read more.

Water is the most vital component for the sustainability of living beings on Earth. From plants to human beings, every single living being on Earth needs water for its survival. In this research, a novel model has been developed in order to predict the suitability of water for agricultural purposes. This research developed the ALBERT Base v2 model for detecting water quality and suitability and a model named the ALBERT Water Potability Detection (ALBERT-WPD) model, customized from the ALBERT Base v2 transformer model. The model was tested using a dataset from Kaggle, and the performance was evaluated. The research used ten parameters. The performance of both models was measured using metrics, accuracy, precision, recall, and F1-score. In this research, traditional models (CNN and RNN) were developed and compared against the ALBERT model to measure its performance and its efficiency in water potability prediction. The findings revealed that the ALBERT models gained higher accuracies than the traditional models: the Base v2 model gained 91% and the altered ALBERT-WPD rendered 96% accuracy. The classification results (precision, recall, and F1-score) obtained for the ALBERT-WPD model for the potability class were 93%, 98%, and 96% and those for the non-potability class were 98%, 95%, and 96%, respectively. The study found that using transformer models for water potability detection procures higher accuracy with the model optimization method. The study concludes that using transformer models (BERT-based) in water potability detection procures higher accuracy (>95%) with fewer parameters in comparison with traditional models (CNN and RNN) which utilize more parameters. The findings show that the transformer models exhibit rapid data processing and handle large datasets efficiently; the handling of such datasets is complicated when using traditional models, as they have vanishing gradient and encounter temporal data loss challenges. Thus, the significance of the proposed research dwells within the use of “transformers” as an advanced machine learning model to predict water potability and quality, showing that transformers are the future of machine learning. Full article

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

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20 pages, 5117 KiB

Open AccessArticle

Hydrological Conditions and Dominant Phytoplankton Species in the Middle and Upper Reaches of the Yarlung Zangbo River, Tibetan Plateau

by Wenyan Xu, Shenhui Li, Hongyu Jin, Zepeng Zhang, Wanqiao Lu, Yanzhe Zhao, Lianghan Pan and Lei Li

Water 2025, 17(9), 1346; https://doi.org/10.3390/w17091346 - 30 Apr 2025

Abstract

To investigate the structure of phytoplankton communities and the ecological niches of dominant species in the middle and upper reaches of the Yarlung Zangbo River, we collected samples at 14 sites in April (spring) and September (autumn) 2023. A total of 198 phytoplankton [...] Read more.

To investigate the structure of phytoplankton communities and the ecological niches of dominant species in the middle and upper reaches of the Yarlung Zangbo River, we collected samples at 14 sites in April (spring) and September (autumn) 2023. A total of 198 phytoplankton species were identified belonging to 6 classes, 13 orders, 24 families, and 53 genera. The community structure was dominated by diatoms, green algae, and cyanobacteria. In April, 163 species of phytoplankton from four phyla were identified, with abundance ranging from 2.94 × 10⁵ to 2.32 × 10⁶ cells/m³ and an average of 1.28 × 10⁶ cells/m³. In September, the abundance of phytoplankton ranged from 1.52 × 10⁵ to 1.58 × 10⁶ cells/m³, with an average value of 6.76 × 10⁵ cells/m³. Sixteen species were classified as dominant (Y > 0.02), among which four showed dominance in both sampling periods, with their dominance level and niche width differing with the season. Water temperature increased with decreasing altitude. At <3500 m in September, Ankistrodesmus falcatus and Oocystis borgei became dominant. Cymbella cistula, Amphora ovalis, and Navicula cryptocephala occupy broad ecological niches and can represent indicator species for water quality. Water temperature, pH, and salinity were identified as primary factors influencing the ecological niche differentiation of dominant phytoplankton species. The interspecific niche overlap was higher in September than in April and greater at >4500 m compared to other elevation ranges (>4500 m; 4000–4500 m; 3500–<4000 m; <3500 m). The effect of elevation on the community structure was greater than that of season. This is the first study to characterize the association of ecological niches of phytoplankton in the upper reaches of the Yarlung Zangbo River with physicochemical environmental parameters. This provides baseline information for the conservation of biodiversity and management of aquatic ecosystems in the rivers of the Tibetan Plateau. Full article

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

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24 pages, 21395 KiB

Open AccessArticle

Accuracy Evaluation of a Wave Monitoring System by Testing the Hydraulic Performance of Portable Low-Cost Buoys

by Susanne Scherbaum, Robin Härtl, Franziska Hübl, Philipp Berglez and Josef Schneider

Water 2025, 17(9), 1345; https://doi.org/10.3390/w17091345 - 30 Apr 2025

Abstract

Lakes are complex ecosystems affected by various anthropogenic influences, including vessel-induced waves. Detecting these waves by a micro-electro-mechanical system (MEMS)-based inertial measurement unit (IMU) equipped on a buoy-based monitoring system can help assess their impacts and support developing sustainable water ecosystem management. This [...] Read more.

Lakes are complex ecosystems affected by various anthropogenic influences, including vessel-induced waves. Detecting these waves by a micro-electro-mechanical system (MEMS)-based inertial measurement unit (IMU) equipped on a buoy-based monitoring system can help assess their impacts and support developing sustainable water ecosystem management. This study evaluated and optimized the measurement accuracy of a wave-monitoring system designed to detect waves generated by recreational vessels on lakes. In laboratory tests, we analyzed and, separately, compared the hydraulic behavior of different buoy configurations and assessed the IMU integration in field test campaigns. Results showed that all tested buoys exhibited a mean average absolute deviation (AAD) of less than 20 mm, while the IMU integration achieved an overall AAD of

1.9

mm. For small waves, characterized by wave heights < 50 mm, the IMU’s AAD corresponds to the buoy’s AAD. However, for larger waves, the buoy’s AAD often significantly exceeds that of the IMU, indicating that the hydraulic performance of the buoy limits measurement accuracy in case of greater waves. The best-performing buoy configuration in laboratory tests achieved a measurement accuracy (mean AAD) below 10 mm (or

10 %

of wave height), confirming the suitability of the developed wave buoys for a vessel-induced wave-monitoring system on lakes. Full article

(This article belongs to the Special Issue Water Resources, Environment, and Ecosystems: Application of New Technology)

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16 pages, 3243 KiB

Open AccessArticle

Enhanced Nitrification of High-Ammonium Reject Water in Lab-Scale Sequencing Batch Reactors (SBRs)

by Sandeep Gyawali, Eshetu Janka and Carlos Dinamarca

Water 2025, 17(9), 1344; https://doi.org/10.3390/w17091344 - 30 Apr 2025

Abstract

Dewatering anaerobic digested sludge leaves a liquid fraction known as reject water, a liquid organic fertilizer containing high amounts of ammonium nitrogen (NH₄-N). However, its concentration should be enhanced to produce commercial fertilizer. Thus, reject water nitrification for stabilization as well [...] Read more.

Dewatering anaerobic digested sludge leaves a liquid fraction known as reject water, a liquid organic fertilizer containing high amounts of ammonium nitrogen (NH₄-N). However, its concentration should be enhanced to produce commercial fertilizer. Thus, reject water nitrification for stabilization as well as for nitrate capture in biochar to be used as a slow-release fertilizer is proposed. This study attempted to accomplish enhanced nitrification by tuning the operating parameters in two lab-scale sequential-batch reactors (SBRs), which were fed reject water (containing 520 ± 55 mg NH₄-N/L). Sufficient alkalinity as per stoichiometric value was needed to maintain the pH and free nitrous acid (FNA) within the optimum range. A nitrogen loading rate (NLR) of 0.14 ± 0.01 kg/m³·d and 3.34 days hydraulic retention time (HRT) helped to achieved complete 100% nitrification in reactor 1 (R₁) on day 61 and in reactor 2 (R₂) on day 82. After a well-developed bacterial biomass, increasing the NH₄-N concentration up to 750 ± 85 mg/L and NLR to 0.23 ± 0.03 kg/m³·d did not affect the nitrification process. Moreover, a feeding sequence once a day provided adequate contact time between nitrifying sludge and reject water, resulting in complete nitrification. It can be concluded that enhanced stable nitrification of reject water can be achieved with quick adjustment of loading, alkalinity, and HRT in SBRs. Full article

(This article belongs to the Special Issue Sustainable Wastewater Treatment and the Circular Economy—2nd Edition)

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19 pages, 1966 KiB

Open AccessReview

The Effect and Adjustment of Ferrate Species in Ferrate-Based Advanced Oxidation Processes for Wastewater Treatment: A Systematic Review

by Yushu Wang, Xiao Luo, Xiaoke Ma, Patiya Kemacheevakul, Sen Qu, Junxiang Huang, Tarloh G. Chea, Peizhe Sun, Lin Zhao, Youjun Zhang and Yongkui Yang

Water 2025, 17(9), 1343; https://doi.org/10.3390/w17091343 - 30 Apr 2025

Abstract

Interest in the combination of ferrates and advanced oxidation processes (AOPs) for wastewater treatment has increased, as revealed in this systematic review. In this study, the multiple functions of Fe(VI) in ferrate-based AOPs are summarized based on the Fe species. Various enhanced oxidation [...] Read more.

Interest in the combination of ferrates and advanced oxidation processes (AOPs) for wastewater treatment has increased, as revealed in this systematic review. In this study, the multiple functions of Fe(VI) in ferrate-based AOPs are summarized based on the Fe species. Various enhanced oxidation pathways are achieved through electron capture by Fe(VI), oxidation by Fe(V) and Fe(IV), or the catalytic effects of Fe(III) and Fe(II). The different contributions of high-valent Fe species and general reactive oxidation species are highlighted by analyzing the results of quenching, methyl phenyl sulfoxide probing, and electron paramagnetic resonance analysis. Methods that are used to adjust the Fe species, including changing the reaction pH, oxidant dosage, dosing pattern, and the addition of reducing or complexing additives, can influence the enhancement efficiency of micropollutant treatment from the perspective of determining the transformation from Fe(VI) to Fe(V) and Fe(IV) with higher reactivity or Fe(III) and Fe(II) circulation. Future studies should focus on the in situ production of high-valent Fe and oxidation pathway-based adjustments in Fe(VI)-AOP techniques. Full article

(This article belongs to the Special Issue Advanced Biotechnologies for Water and Wastewater Treatment, 2nd Edition)

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24 pages, 3828 KiB

Open AccessArticle

Developing Recyclable Magnetic TiO₂-Fe₃O₄ Loading on Carbon Microtube Photocatalyst for Efficient Photodegradation of Microcystin-LR Under Visible Light

by Xinyi Zhang, Tian Xia, Ying Meng, Jiaxi Zhang, Gaofeng Chen, Zhaoting Ji and Wenli Qin

Water 2025, 17(9), 1342; https://doi.org/10.3390/w17091342 - 29 Apr 2025

Abstract

Microcystins (MCs) are produced by cyanobacteria blooms in eutrophic water and can cause acute and chronic toxicity and even mortality to animals and humans. Previous MC removal strategies concernedonly highly contaminated water, in which the concentration of the pollutant was considerably larger than [...] Read more.

Microcystins (MCs) are produced by cyanobacteria blooms in eutrophic water and can cause acute and chronic toxicity and even mortality to animals and humans. Previous MC removal strategies concernedonly highly contaminated water, in which the concentration of the pollutant was considerably larger than that in the natural world. In this study, we developed a composite of TiO₂-coated magnetic carbon microtube (C-TiO₂-Fe₃O₄) and used it as a photocatalyst to efficiently remove microcystin-LR (MC-LR) from water under visible light from water. And the huge surface of the carbon microtube dramatically boosted the adsorbability and charge mobility, which lowered the recombination rate of electron–hole pairs, and hence systematically enhanced photocatalytic activity. The combination of adsorption and photodegradation endowed the composite with a better performance in the removal of trace amounts of MC-LR than the C-TiO₂. It was found that increasing the contact time and catalyst dosage, acidic environment, and lower initial MC-LR concentration had positive effects on MC-LR removal. The optimum reaction conditions of C-TiO₂-Fe₃O₄ was a reaction time of 12.68 min, a catalyst dosage of 0.39 g·L⁻¹, and a pH of 7.72. The C-TiO₂-Fe₃O₄ (surface area normalized apparent reaction rate constants K/S_BET = 1.2 × 10⁻⁴) presented a higher reaction rate than C-TiO₂ (K/S_BET = 8.4 × 10⁻⁵). Moreover, the stable removal capability of C-TiO₂-Fe₃O₄ was confirmed over multiple cycles. Finally, the ecological safety performance was also evaluated after visible light illumination. This work paves the way for the development of more efficient and easily separable purifiers for the removal of pollutants and toxins from contaminated water. Full article

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

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