Water

16 pages, 3385 KiB

Open AccessArticle

The Influence of Seasonal Freeze–Thaw in Northeast China on Greenhouse Gas Emissions and Microbial Community Structure in Peat Soil

by Yanru Gong, Tao Yang, Jiawen Yan and Xiaofei Yu

Water 2025, 17(16), 2395; https://doi.org/10.3390/w17162395 (registering DOI) - 13 Aug 2025

Abstract

Peat soil is a significant global carbon storage pool, accounting for one-third of the global soil carbon pool. Its greenhouse gas emissions have a significant impact on climate change. Seasonal freeze–thaw cycles are common natural phenomena in high-latitude and high-altitude regions. They significantly [...] Read more.

Peat soil is a significant global carbon storage pool, accounting for one-third of the global soil carbon pool. Its greenhouse gas emissions have a significant impact on climate change. Seasonal freeze–thaw cycles are common natural phenomena in high-latitude and high-altitude regions. They significantly affect the mineralization of soil organic carbon and greenhouse gas emissions by altering the physical structure, moisture conditions, and microbial communities of the soil. In this study, through the construction of an indoor simulation experiment of the typical freeze–thaw cycle models in spring and autumn in the Greater Xing‘an Range region of China and the Jinchuan peatland of Jilin Longwan National Nature Reserve, the physicochemical properties, greenhouse gas emission fluxes, microbial community structure characteristics, and key metabolic pathways of peat soils in permafrost and seasonally frozen ground areas were determined. The characteristics of greenhouse gas emissions and their influencing mechanisms for peat soil in northern regions under different freeze–thaw conditions were explored. The research found that the freeze–thaw cycle significantly changed the chemical properties of peat soil and significantly affected the emission rates of CO₂, CH₄, and N₂O. It also clarified the interaction relationship between soil’s physicochemical properties (such as dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonium nitrogen (NH₄⁺), soil organic carbon (SOC), etc.) and the structure and metabolic function of microbial communities. It is of great significance for accurately assessing the role of peatlands in the global carbon cycle and formulating effective ecological protection and management strategies. Full article

(This article belongs to the Section Soil and Water)

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27 pages, 20003 KiB

Open AccessArticle

Spatiotemporal Patterns of Algal Blooms in Lake Bosten Driven by Climate and Human Activities: A Multi-Source Remote-Sensing Perspective for Sustainable Water-Resource Management

by Haowei Wang, Zhoukang Li, Yang Wang and Tingting Xia

Water 2025, 17(16), 2394; https://doi.org/10.3390/w17162394 (registering DOI) - 13 Aug 2025

Abstract

Algal blooms pose a serious threat not only to the lake ecosystem of Lake Bosten but also by negatively impacting its rapidly developing fisheries and tourism industries. This study focuses on Lake Bosten as the research area and utilizes multi-source remote sensing imagery [...] Read more.

Algal blooms pose a serious threat not only to the lake ecosystem of Lake Bosten but also by negatively impacting its rapidly developing fisheries and tourism industries. This study focuses on Lake Bosten as the research area and utilizes multi-source remote sensing imagery from Landsat TM/ETM+/OLI and Sentinel-2 MSI. The Adjusted Floating Algae Index (AFAI) was employed to extract algal blooms in Lake Bosten from 2004 to 2023, analyze their spatiotemporal evolution characteristics and driving factors, and construct a Long Short Term Memory (LSTM) network model to predict the spatial distribution of algal-bloom frequency. The stability of the model was assessed through temporal segmentation of historical data combined with temporal cross-validation. The results indicate that (1) during the study period, algal blooms in Lake Bosten were predominantly of low-risk level, with low-risk bloom coverage accounting for over 8% in both 2004 and 2005. The intensity of algal blooms in summer and autumn was significantly higher than in spring. The coverage of medium- and high-risk blooms reached 2.74% in the summer of 2004 and 3.03% in the autumn of 2005, while remaining below 1% in spring. (2) High-frequency algal bloom areas were mainly located in the western and northwestern parts of the lake, and the central region experienced significantly more frequent blooms during 2004–2013 compared to 2014–2023, particularly in spring and summer. (3) The LSTM model achieved an R² of 0.86, indicating relatively stable performance. The prediction results suggest a continued low frequency of algal blooms in the future, reflecting certain achievements in sustainable water-resource management. (4) The interactions among meteorological factors exhibited significant influence on bloom formation, with the q values of temperature and precipitation interactions both exceeding 0.5, making them the most prominent meteorological driving factors. Monitoring of sewage discharge and analysis of agricultural and industrial expansion revealed that human activities have a more direct impact on the water quality of Lake Bosten. In addition, changes in lake area and water environment were mainly influenced by anthropogenic factors, ultimately making human activities the primary driving force behind the spatiotemporal variations of algal blooms. This study improved the timeliness of algal-bloom monitoring through the integration of multi-source remote sensing and successfully predicted the future spatial distribution of bloom frequency, providing a scientific basis and decision-making support for the sustainable management of water resources in Lake Bosten. Full article

(This article belongs to the Special Issue Use of Remote Sensing Technologies for Water Resources Management)

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27 pages, 12670 KiB

Open AccessArticle

Integrated Multivariate and Spatial Assessment of Groundwater Quality for Sustainable Human Consumption in Arid Moroccan Regions

by Yousra Tligui, El Khalil Cherif, Wafae Lechhab, Touria Lechhab, Ali Laghzal, Nordine Nouayti, El Mustapha Azzirgue, Joaquim C. G. Esteves da Silva and Farida Salmoun

Water 2025, 17(16), 2393; https://doi.org/10.3390/w17162393 - 13 Aug 2025

Abstract

Groundwater quality in arid and semi-arid regions of Morocco is under increasing pressure due to both anthropogenic influences and climatic variability. This study investigates the physicochemical and heavy metal characteristics of groundwater across four Moroccan regions (Tangier-Tetouan-Al Hoceima, Oriental, Souss-Massa, and Marrakech-Safi) known [...] Read more.

Groundwater quality in arid and semi-arid regions of Morocco is under increasing pressure due to both anthropogenic influences and climatic variability. This study investigates the physicochemical and heavy metal characteristics of groundwater across four Moroccan regions (Tangier-Tetouan-Al Hoceima, Oriental, Souss-Massa, and Marrakech-Safi) known for being argan tree habitats. Thirteen groundwater samples were analyzed for twenty-five parameters, including major ions, nutrients, and trace metals. Elevated levels of ammonium, turbidity, electrical conductivity, and dissolved oxygen were observed in multiple samples, surpassing Moroccan water quality standards and indicating significant quality deterioration. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) detected arsenic concentrations exceeding permissible limits in sample AW11 alongside widespread lead contamination in most samples except AW5 and AW9. Spatial patterns of contamination were characterized using Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), K-means clustering, and GIS-based Inverse Distance Weighted (IDW) interpolation. These multivariate approaches revealed marked spatial heterogeneity and highlighted the dual influence of geogenic processes and anthropogenic activities on groundwater quality. To assess consumption suitability, a Water Quality Index (WQI) and Human Health Risk Assessment were applied. As a result, 31% of samples were rated “Fair” and 69% as “Good”, but with notable non-carcinogenic risks, particularly to children, attributable to nitrate, lead, and arsenic. The findings underscore the urgent need for systematic groundwater monitoring and management strategies to safeguard water resources in Morocco’s vulnerable dryland ecosystems, particularly in regions where groundwater sustains vital socio-ecological species such as argan forests. Full article

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

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14 pages, 2098 KiB

Open AccessArticle

Addition of Heterotrophic Nitrification and Aerobic Denitrification Bacterial Agents to Enhance Bio-Nests Treating Low Carbon-to-Nitrogen Ratio Municipal Wastewater

by Qingxin Diao, Chaolin Quan, Wanmeng Li, Xiangtong Zhou, Zhigang Liu, Xinshan Rong, Zhishui Liang, Xiao Wang and Zhiren Wu

Water 2025, 17(16), 2392; https://doi.org/10.3390/w17162392 - 13 Aug 2025

Abstract

Municipal wastewater with a low carbon-to-nitrogen (C/N) ratio presents challenges for conventional nitrogen removal processes, often requiring costly external carbon sources. This study investigated the enhancement of nitrogen removal in a simultaneous nitrification and denitrification (SND) system by incorporating heterotrophic nitrification and aerobic [...] Read more.

Municipal wastewater with a low carbon-to-nitrogen (C/N) ratio presents challenges for conventional nitrogen removal processes, often requiring costly external carbon sources. This study investigated the enhancement of nitrogen removal in a simultaneous nitrification and denitrification (SND) system by incorporating heterotrophic nitrification and aerobic denitrification (HN-AD) bacterial agents (Klebsiella variicola L3, Acinetobacter beijerinckii W4, and Acinetobacter sp. Z1) with modified basalt fiber carriers. Three reactors were compared: mixed HN-AD strains (M), mixed strains with activated sludge (A+M), and activated sludge alone (A). Results demonstrated that the A+M reactor achieved superior performance, with median removal efficiencies of 82.2% for NH₄⁺-N, 52.9% for total nitrogen (TN), and 51.6% for COD, outperforming the M reactor (75.2%, 43.6%, and 51.6%) and the A reactor (63.2%, 29.3%, and 44.8%). The A+M reactor also exhibited a 40% reduction in COD consumption per unit TN removed (2.55 ± 1.75) compared to the control reactor A (4.25 ± 3.99). Microbial analysis revealed Acinetobacter sp. Z1 (6.1%) and K. variicola L3 (1.1%) as dominant species, with the A+M reactor showing higher microbial diversity (56.4% Proteobacteria, 10.2% Bacteroidota) and biological viability (VSS/SS ratio of 0.70 ± 0.01). Extracellular polymeric substance (EPS) content in A+M reached 242.26 ± 15.52 mg/g-VSS, with a protein-to-polysaccharide ratio of 2.77 ± 0.00, indicating robust biofilm activity. These findings highlight the potential of HN-AD bacterial agents to enhance nitrogen removal in low C/N wastewater treatment, offering a cost-effective and sustainable alternative to traditional methods by reducing reliance on external carbon sources and improving system efficiency. Full article

(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)

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18 pages, 4123 KiB

Open AccessArticle

Urban Growth and River Course Dynamics: Disconnected Floodplain and Urban Flood Risk in Manohara Watershed, Nepal

by Shobha Shrestha, Prem Sagar Chapagain, Kedar Dahal, Nirisha Adhikari, Prajjwal Shrestha and Laxmi Manandhar

Water 2025, 17(16), 2391; https://doi.org/10.3390/w17162391 - 13 Aug 2025

Abstract

Human activities and river course change have a complex reciprocal interaction. The river channel is altered by human activity, and these alterations have an impact on the activities and settlements along the riverbank. Understanding the relationship between urbanization and changes in river morphology [...] Read more.

Human activities and river course change have a complex reciprocal interaction. The river channel is altered by human activity, and these alterations have an impact on the activities and settlements along the riverbank. Understanding the relationship between urbanization and changes in river morphology is crucial for effective river management, safeguarding the urban environment, and mitigating flood hazards. In this context, this study has been conducted to investigate the interrelationship between morphological dynamics, built-up growth, and urban flood risk along the Manohara River in Kathmandu Valley, Nepal. The Sinuosity Index was used to analyze variation in river courses and instability from 1996 to 2023. Built-up change analysis is carried out using supervised maximum likelihood classification method and rate of change is calculated for built-up area growth (2003–2023) and building construction between 2003 and 2021. Flood hazard risk manning was carried out using flood frequency estimation method integrating HEC-GeoRAS modeling. Linear regression and spatial overlay analysis was carried out to examine the interrelationship between river morphology, urban growth, and fold hazed risk. In recent years (2016–2023), the Manohara River has straightened, particularly after 2011. Before 2011, it had significant meandering with pronounced curves and bends, indicating a mature river system. However, the SI value of 1.45 in 2023 and 1.80 in 2003 indicates a significant straightening of high meandering over 20 years. A flood hazard modeling carried out within the active floodplain of the Manohara River shows that 26.4% of the area is under high flood risk and 21% is under moderate risk. Similarly, over 10 years from 2006 to 2016, the rate of built-up change was found to be 9.11, while it was 7.9 between 2011 and 2021. The calculated R² value of 0.7918 at a significance level of 0.05 (with a p value of 0.0175, and a standard error value of 0.07877) indicates a strong positive relationship between decreasing sinuosity and increasing built-up, which demonstrates the effect of built-up expansion on river morphology, particularly the anthropogenic activities of encroachment and haphazard constructions, mining, dumping wastes, and squatter settlements along the active floodplain, causing instability on the river course and hence, lateral shift. The riverbank and active floodplain are not defined scientifically, which leads to the invasion of the river area. These activities, together with land use alteration in the floodplain, show an increased risk of flood hazards and other natural calamities. Therefore, sustainable protection measures must be prioritized in the active floodplain and flood risk areas, taking into account upstream–downstream linkages and chain effects caused by interaction between natural and adverse anthropogenic activities. Full article

(This article belongs to the Special Issue Sustainable Urban Water Management: The Role of Nature-Based Solutions)

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35 pages, 4629 KiB

Open AccessArticle

Evaluation of Infiltration Swale Media Using Small-Scale Testing Techniques and Its SWMM Modeling Considerations

by Diego Armando Ramírez Flórez, Yuting Ji, Parker J. Austin, Michael A. Perez, Xing Fang and Wesley N. Donald

Water 2025, 17(16), 2390; https://doi.org/10.3390/w17162390 - 12 Aug 2025

Abstract

Impervious surfaces reduce natural infiltration, leading to increased runoff, erosion, and pollutant transport. The Alabama Department of Transportation (ALDOT) relies on implementing infiltration swales, a linear bioretention-based practice, along roadside drainage channels to reduce surface runoff. This study developed and constructed modified permeameters [...] Read more.

Impervious surfaces reduce natural infiltration, leading to increased runoff, erosion, and pollutant transport. The Alabama Department of Transportation (ALDOT) relies on implementing infiltration swales, a linear bioretention-based practice, along roadside drainage channels to reduce surface runoff. This study developed and constructed modified permeameters and infiltrometers to evaluate and optimize media used to construct infiltration swales. The average measured falling head infiltration rate of sandy topsoil used in the media matrix was 0.63 ft/day (0.19 m/day). A series of amended topsoil mixtures were tested to improve the infiltration rate of the media. In particular, the mixture of 80% topsoil and 20% pine bark fines (by weight) significantly improved the infiltration rates of the swale media. Through iterative testing, the F3 design with 6 in. (15.2 cm) mixture and 10 in. (25.4 cm) sand achieved up to 13.73 ft/day (4.18 m/day) of infiltration rate under constant head, far surpassing the infiltration rate of the current ALDOT design. SWMM bioretention cell models were developed to understand the swale infiltration process and revealed that the infiltration rates obtained from column tests were the saturated hydraulic conductivities of the soil layer when there was no other restriction on vertical flow. The simulated swale hydrological performance depends not only on variations in soil conductivity but also on other swale characteristics under field conditions. Findings from this research can be used to enhance the performance of infiltration-based stormwater practices. Full article

(This article belongs to the Special Issue Urban Drainage Systems and Stormwater Management)

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31 pages, 10184 KiB

Open AccessArticle

Multiple Correlation Analysis of Operational Safety of Long-Distance Water Diversion Project Based on Copula Bayesian Network

by Pengyuan Li, Fudong Dong, Guibin Lv, Yuansen Wang, Yongguo Sheng, Feng Cheng and Bo Wang

Water 2025, 17(16), 2389; https://doi.org/10.3390/w17162389 - 12 Aug 2025

Abstract

Based on the Copula theory, a multiple correlation analysis model for the operation safety risks of long-distance water diversion projects was established. Combined with Bayesian network reasoning, a polynomial regression analysis, and other techniques, a dynamic analysis method for the operation safety of [...] Read more.

Based on the Copula theory, a multiple correlation analysis model for the operation safety risks of long-distance water diversion projects was established. Combined with Bayesian network reasoning, a polynomial regression analysis, and other techniques, a dynamic analysis method for the operation safety of long-distance water diversion projects based on a Copula Bayesian network model was proposed, providing decision support for the operation safety risk management of long-distance water diversion projects. We took the Middle Route Project of the South-to-North Water Diversion Project as an example to verify the validity and practicability of the model. The results show that this method can capture the nonlinear mapping relationship when the probability of risk occurrence changes dynamically on the basis of considering the risk correlation, and realize the dynamic analysis of risk correlation. Full article

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

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35 pages, 7825 KiB

Open AccessReview

Approaches for Assessment of Soil Moisture with Conventional Methods, Remote Sensing, UAV, and Machine Learning Methods—A Review

by Songthet Chinnunnem Haokip, Yogesh A. Rajwade, K. V. Ramana Rao, Satya Prakash Kumar, Andyco B. Marak and Ankur Srivastava

Water 2025, 17(16), 2388; https://doi.org/10.3390/w17162388 - 12 Aug 2025

Abstract

Soil moisture or moisture content is a fundamental constituent of the hydrological system of the Earth and its ecological systems, playing a pivotal role in the productivity of agricultural produce, climate modeling, and water resource management. This review comprehensively examines conventional and advanced [...] Read more.

Soil moisture or moisture content is a fundamental constituent of the hydrological system of the Earth and its ecological systems, playing a pivotal role in the productivity of agricultural produce, climate modeling, and water resource management. This review comprehensively examines conventional and advanced approaches for estimation or measuring of soil moisture, including in situ methods, remote sensing technologies, UAV-based monitoring, and machine learning-driven models. Emphasis is primarily on the evolution of soil moisture measurement from destructive gravimetric techniques to non-invasive, high-resolution sensing systems. The paper emphasizes how machine learning modules like Random Forest models, support vector machines, and AI-based neural networks are becoming more and more popular for modeling intricate soil moisture dynamics with data from several sources. A bibliometric analysis further underscores the research trends and identifies key contributors, regions, and technologies in this domain. The findings advocate for the integration of physics-based understanding, sensor technologies, and data-driven approaches to enhance prediction accuracy, spatiotemporal coverage, and decision-making capabilities. Full article

(This article belongs to the Special Issue Application of Various Hydrological Modeling Techniques and Methods in River Basin Management, 2nd Edition)

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22 pages, 793 KiB

Open AccessArticle

Ecotoxicological Risk Assessment and Monitoring of Pesticide Residues in Soil, Surface Water, and Groundwater in Northwestern Tunisia

by Khaoula Toumi, Abir Arbi, Nafissa Soudani, Anastasia Lomadze, Dalila Haouas, Terenzio Bertuzzi, Alessandra Cardinali, Lucrezia Lamastra, Ettore Capri and Nicoleta Alina Suciu

Water 2025, 17(16), 2387; https://doi.org/10.3390/w17162387 - 12 Aug 2025

Abstract

Pesticides play a significant role in agriculture, but their leaching into soil and water poses serious environmental risks. This study examines pesticide contamination in surface and groundwater in northern Tunisia, specifically in Kef governorate, involving a survey of 140 farmers to gather data [...] Read more.

Pesticides play a significant role in agriculture, but their leaching into soil and water poses serious environmental risks. This study examines pesticide contamination in surface and groundwater in northern Tunisia, specifically in Kef governorate, involving a survey of 140 farmers to gather data on agricultural practices and pesticide use. Twenty-four pesticides were monitored and utilized within the Pesticide Environmental Risk Indicator (PERI) model to evaluate environmental risk scores for each substance. Soil and water samples were analyzed using a multi-residue method and liquid chromatography–tandem mass spectrometry. Results showed that 50% of the pesticides assessed had an Environmental Risk Score of 5 or higher. Contamination was identified in water and soil, with 18 and 15 pesticide residues, respectively. Notable concentrations included 7.8 µg/L of linuron and flupyradifurone in water and 1718.4 µg/kg of linuron in soil. Commonly detected substances included the insecticide acetamiprid and fungicides like cyflufenamid and penconazole in water, while soil contamination was linked to fungicides metalaxyl and metalaxyl-m, as well as herbicides linuron and s-metolachlor. Factors such as proximity to treated water points and poor packaging management were discussed as risks. The findings emphasize the need for better monitoring and sustainable agricultural practices to mitigate contamination. Full article

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

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Graphical abstract

27 pages, 2893 KiB

Open AccessArticle

How Integrated Are Water and Food Systems in China? Assessing Coupling Mechanisms and Geographic Disparities

by Shan Zhou, Chao Sun and Yihang Hu

Water 2025, 17(16), 2386; https://doi.org/10.3390/w17162386 - 12 Aug 2025

Abstract

Water resources are of vital importance to human survival and development. This study systematically analyzed the coupling coordination mechanism between China’s food security (FS) and water resource management (WRM) from 2010 to 2022 using the TOPSIS model, Dagum Gini coefficient, coupling coordination model, [...] Read more.

Water resources are of vital importance to human survival and development. This study systematically analyzed the coupling coordination mechanism between China’s food security (FS) and water resource management (WRM) from 2010 to 2022 using the TOPSIS model, Dagum Gini coefficient, coupling coordination model, and fixed effects regression model. The results indicate that FS exhibited a “U-shaped” evolution: an average annual decline of 1.4% before 2017 followed by recovery to 2.39% due to policy optimization and technological upgrades, though significant regional disparities persisted with 15 provinces maintaining ecological vulnerability scores below 0.3. WRM showed an average annual increase of 1.33%, later accelerating to 1.76% driven by projects like the South-to-North Water Diversion Project, which significantly improved 28 provinces. The FS-WRM coupling coordination degree escalated from mild imbalance to near imbalance, forming a spatial pattern of “central region leading–northeast following–eastern fluctuation–western catching up”, with 10 provinces reaching barely coordinated levels in 2022. The study reveals that policy support, infrastructure development, technological innovation, and management model transformation are key influencing factors for FS-WRM coupling coordination. Full article

(This article belongs to the Special Issue Urban Water Resources: Sustainable Management and Policy Needs)

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19 pages, 3264 KiB

Open AccessArticle

Urban Geochemical Contamination of Highland Peat Wetlands of Very High Ecological and First Nations Cultural Value

by Ian A. Wright, Holly Nettle, Uncle David King, Michael J. M. Franklin and Amy-Marie Gilpin

Water 2025, 17(16), 2385; https://doi.org/10.3390/w17162385 - 12 Aug 2025

Abstract

Temperate Highland Peat Swamps on Sandstone (THPSS) are wetlands in the Blue Mountains, south-eastern Australia. The wetlands have legislative protection as endangered ecological communities. They have long-standing cultural significance for Gundungurra Traditional Custodians. Previous studies document their degradation by urban development and [...] Read more.

Temperate Highland Peat Swamps on Sandstone (THPSS) are wetlands in the Blue Mountains, south-eastern Australia. The wetlands have legislative protection as endangered ecological communities. They have long-standing cultural significance for Gundungurra Traditional Custodians. Previous studies document their degradation by urban development and vulnerability to extreme weather. Water quality in our study was assessed at wetlands in protected areas and compared with others exposed to urban development. We derived water quality guidelines that are intended to help future water quality assessment at THPSS and, in particular, to detect any impact from urban development on these wetland systems. Water quality in urban swamps was consistent with the freshwater salinisation syndrome despite all the swamps having relatively low electrical conductance (<140 µS cm⁻¹). Urban swamp water had salinity (mean 87.3 µS cm⁻¹) three times that of non-urban swamps (mean 28 µS cm⁻¹). The ionic composition of urban swamp water was dominated by calcium and bicarbonate, consistent with urban alkalisation syndrome. Our guidelines instead recommend limits for pH, salinity, turbidity, dissolved oxygen, and metals detected in greater concentrations that were found in urban swamps (iron, manganese, barium, and strontium). Our results support the theory that the dissolution of urban concrete materials is a degradation process that contributes to the impairment of urban swamp water quality. Full article

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

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23 pages, 3226 KiB

Open AccessArticle

Advanced Flow Detection Cell for SPEs for Enhancing In Situ Water Monitoring of Trace Levels of Cadmium

by Giulia Mossotti, Davide Girelli, Matilde Aronne, Giulio Galfré, Andrea Piscitelli, Luciano Scaltrito, Sergio Ferrero and Valentina Bertana

Water 2025, 17(16), 2384; https://doi.org/10.3390/w17162384 - 12 Aug 2025

Abstract

An advanced anodic stripping voltammetry (ASV)-based Micro Electro Mechanical System (MEMS) sensor for cadmium (Cd) detection is presented in this study, which is cost-effective and efficient for in situ water monitoring, providing a crucial early warning mechanism, streamlining environmental monitoring, and facilitating timely [...] Read more.

An advanced anodic stripping voltammetry (ASV)-based Micro Electro Mechanical System (MEMS) sensor for cadmium (Cd) detection is presented in this study, which is cost-effective and efficient for in situ water monitoring, providing a crucial early warning mechanism, streamlining environmental monitoring, and facilitating timely intervention to safeguard public health and environmental safety. The rationale behind this work is to address the critical need for an in situ monitoring system for cadmium (Cd) in freshwater sources, particularly those adjacent to agricultural fields. Cd(II) is a highly toxic heavy metal that poses a significant threat to agricultural ecosystems and human health due to its rapid bioaccumulation in plants and subsequent entry into the food chain. The developed analytic device is composed of a commercial mercury salt-modified graphite screen-printed electrode (SPE) with a custom-designed innovative polydimethylsiloxane (PDMS) flow detection cell. The flow cell was prototyped using 3D printing and replica moulding, with its design and performance validated through COMSOL Multiphysics simulations to optimize inflow conditions and ensure maximum analyte dispersion on the working electrode surface. Chemical detection was performed using square wave voltammetry, demonstrating a linear response for Cd(II) concentrations of 0 to 20 µg/L. The system exhibited robust analytical performance, enabling 25–30 daily analyses with consistent sensitivity within the Limit of Detection (LoD) set by the law of 3 µg/L. Full article

(This article belongs to the Special Issue Water Quality Monitoring and Prediction Using New Sensors, Machine Learning and Big Data)

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15 pages, 2779 KiB

Open AccessArticle

Groundwater Flow Impact in Complex Karst Regions Considering Tunnel Construction Conditions: A Case Study of the New Construction Project at XLS Tunnel

by Zhou Chen, Hongtu Zhang, Qi Shen, Zihao Chen, Kai Wang and Changsheng Chen

Water 2025, 17(16), 2383; https://doi.org/10.3390/w17162383 - 12 Aug 2025

Abstract

Tunneling in structurally complex, tectonically active regions such as southwest China poses significant environmental risks to groundwater, especially in heterogeneous karst fault systems where conventional prediction methods often fail. This study innovatively coupled MODFLOW’s STREAM package (for simulating karst conduit networks) and DRAIN [...] Read more.

Tunneling in structurally complex, tectonically active regions such as southwest China poses significant environmental risks to groundwater, especially in heterogeneous karst fault systems where conventional prediction methods often fail. This study innovatively coupled MODFLOW’s STREAM package (for simulating karst conduit networks) and DRAIN package (for tunnel inflow prediction) within a 3D groundwater model to assess hydrogeological impacts in complex mountainous terrain. The simulations show that an uncased tunnel lining causes significant groundwater changes under natural conditions, with predicted inflows reaching 34,736 m³/d. Conventional cement grouting (permeability: 1 × 10⁻⁵ cm/s; thickness: 10 m) mitigates the effects considerably and reduces the inflows in the tunnel sections by 27–97%. Microfine cement grouting (5 × 10⁻⁶ cm/s; 10 m thickness) further improves performance by achieving a 49–98% reduction in inflows and limiting the reduction in spring discharge to ≤13.28%. These results establish a valid theoretical framework for predicting groundwater impacts in heterogeneous terrain and demonstrate that targeted seepage control—particularly grouting with microfine cement—effectively protects groundwater-dependent ecosystems during infrastructure development. Full article

(This article belongs to the Section Hydrogeology)

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21 pages, 12605 KiB

Open AccessArticle

Impact of Sharp Soil Interfaces on Solute Transport: Insights from a Reactive Tracer Test in a 2D Intermediate-Scale Experiment

by Guido González-Subiabre, Oriol Bertran and Daniel Fernàndez-Garcia

Water 2025, 17(16), 2382; https://doi.org/10.3390/w17162382 - 12 Aug 2025

Abstract

Understanding solute transport across interfaces between different porous materials is crucial for subsurface applications. Column tracer experiments have suggested solute accumulation at these interfaces. This effect cannot be explained by standard models based on Fickian flux continuity and the advection–dispersion equation. To analyze [...] Read more.

Understanding solute transport across interfaces between different porous materials is crucial for subsurface applications. Column tracer experiments have suggested solute accumulation at these interfaces. This effect cannot be explained by standard models based on Fickian flux continuity and the advection–dispersion equation. To analyze this phenomenon, we present reactive transport experiments in a 2D intermediate-scale horizontal tank to visualize and evaluate the spatiotemporal evolution of a solute plume crossing a sharp interface between coarse and fine materials. The plume results from the reaction of two fluid solutions entering the tank in parallel through inlet ports. The reaction product is analyzed using mixing and reaction metrics. Results show the reaction product encounters anomalous resistance when the plume crosses the coarse-to-fine (CF) interface. This effect is less pronounced in the fine-to-coarse (FC) transition. This asymmetric resistance does not produce solute accumulation behind the interface, a difference from the results obtained with the one-dimensional model. Instead, results show enhanced transverse spread of the reaction product in the coarse-to-fine transition, with slow release in the fine material. A sudden decrease in the longitudinal concentration profile across the interface is observed. Mixing metrics show that as apparent transverse dispersivity increases closer to the interface in the CF transition, the scalar dissipation rate and total mass reacted increase, indicating that the CF configuration promotes greater solute reactivity near the interface compared to the FC configuration. Full article

(This article belongs to the Topic Advances in Groundwater Science and Engineering)

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19 pages, 1033 KiB

Open AccessArticle

Designing Nature-Based Solutions for Sediment Control in Impaired Humid Subtropical Forests: An Approach Based on the Environmental Benefits Assessment

by Águeda Bellver-Domingo, Carme Machí-Castañer and Francesc Hernández-Sancho

Water 2025, 17(16), 2381; https://doi.org/10.3390/w17162381 - 12 Aug 2025

Abstract

Land-use changes cause disturbance to sediment dynamics, increasing downstream sediment loads discharged into ecosystems and provoking impacts on stream quality and damage to current stormwater infrastructures. Wastewater nature-based solutions (NBSWT) are bioretention techniques that alleviate downstream degradation caused by runoff sediment accumulation and [...] Read more.

Land-use changes cause disturbance to sediment dynamics, increasing downstream sediment loads discharged into ecosystems and provoking impacts on stream quality and damage to current stormwater infrastructures. Wastewater nature-based solutions (NBSWT) are bioretention techniques that alleviate downstream degradation caused by runoff sediment accumulation and are projected as an off-line street device that enhances treatment of runoff contaminant loads. This research assesses the economic, social, and environmental benefits from sediment load reduction in runoff by designing a new NBSWT in a selected urban area of the Mantiqueira Mountain Range (São Paulo, Brazil), considered an irreplaceable protected area for biodiversity and urban water supply. To achieve this quantification, the shadow prices methodology has been used. The results obtained here show the adaptive capacity that NBSWT have according to the territory and its climatic particularities, quantified at USD 40,475,255. This value demonstrates that the retention of runoff sediment generates a direct environmental benefit related to the ecosystem improvement of the river system located downstream, preserving its environmental and social importance. Hence, this study demonstrates the potential of using shadow prices methodology as a management tool for quantifying the environmental benefit of removing runoff solids by using NBSWT in developing urban areas. Full article

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

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44 pages, 3756 KiB

Open AccessArticle

Reflection of Intercontinental Freshwater Resources on Geopolitical Risks: Time Series Analysis

by Sabiha Oltulular

Water 2025, 17(16), 2380; https://doi.org/10.3390/w17162380 - 12 Aug 2025

Abstract

Water, an indispensable resource for life and not a complete substitute, is indispensable for energy production, industry, agriculture, and ecosystem sustainability. In particular, the limited and unequal distribution of freshwater reserves makes water a strategic power element on a global scale, making competition [...] Read more.

Water, an indispensable resource for life and not a complete substitute, is indispensable for energy production, industry, agriculture, and ecosystem sustainability. In particular, the limited and unequal distribution of freshwater reserves makes water a strategic power element on a global scale, making competition inevitable. Increasing water demand and decreasing water resources increase regional and global security risks, causing water to go beyond being a vital natural resource and become a determining factor in diplomacy, conflict, and the balance of power. This study aimed to examine the relationship between freshwater resources and geopolitical risk between 1961 and 2021 using the ARDL model. All models had long-run relationships between water resources and geopolitical risk. In the long-run, a 1% decrease in water resources increased geopolitical risk by 0.37% in Chile, 0.30% in Colombia, 0.46% in the Netherlands, 0.42% in Thailand, 0.44% in Ukraine, and 0.29% in Venezuela. The adjustment rates for the prior period imbalances were estimated to be 0.75% in Switzerland, 0.68% in Chile, 0.28% in Colombia, 0.45% in the Netherlands, 0.86% in Thailand, 0.14% in Ukraine, and 0.59% in Venezuela. Full article

(This article belongs to the Special Issue Water Resources, Economic Development and Environment Carrying Capacity)

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32 pages, 4113 KiB

Open AccessArticle

A Novel Deep Learning-Based Soil Moisture Prediction Model Using Adaptive Group Radial Lasso Regularized Basis Function Networks (AGRL-RBFN) Optimized by Hierarchical Correlated Spider Wasp Optimizer (HCSWO) and Incremental Learning (IL)

by Claudia Cherubini and Muthu Bala Anand

Water 2025, 17(16), 2379; https://doi.org/10.3390/w17162379 - 11 Aug 2025

Abstract

Soil moisture serves as a critical factor in the hydrological cycle, affecting plant growth, ecosystem health, and groundwater reserves. Current methods for monitoring and predicting it fail to account for the complexities introduced by climatic variations and other influencing factors, such as the [...] Read more.

Soil moisture serves as a critical factor in the hydrological cycle, affecting plant growth, ecosystem health, and groundwater reserves. Current methods for monitoring and predicting it fail to account for the complexities introduced by climatic variations and other influencing factors, such as the effects of atmospheric interference and data gaps, leading to reduced prediction accuracy. To address these challenges, this study introduces a novel soil moisture prediction model based on remote sensing and deep learning, utilizing the Adaptive Group Radial Lasso Regularized Basis Function Networks (AGRL-RBFN) optimized by the Hierarchical Correlated Spider Wasp Optimizer (HCSWO) and incremental learning (IL) techniques. The proposed method for monitoring soil moisture utilizes hyperspectral and soil moisture data from a 2017 campaign in Karlsruhe, encompassing variables such as datetime, soil moisture percentage, soil temperature, and remote sensing spectral bands. The proposed methodology begins with comprehensive preprocessing of historical remote sensing data to fill gaps, reduce noise, and correct atmospheric disturbances. It then employs a unique seasonal mapping and grouping technique, enhanced by the AdaK-MCC method, to analyze the impact of climatic changes on soil moisture patterns. The model’s innovative feature selection approach, using HCSWO, identifies the most significant predictors, ensuring optimal data input for the AGRL-RBFN model. The model achieves an impressive accuracy of 98.09%, a precision of 98.17%, a recall of 97.24%, and an F1-score of 98.95%, outperforming existing methods. Furthermore, it attains a mean absolute error (MAE) of 0.047 in gap filling and a Dunn Index of 4.897 for clustering. Although successful in many aspects, the study did not investigate the relationship between soil moisture levels and specific crops, which presents an opportunity for future research aimed at enhancing smart agricultural practices. Furthermore, the model can be refined by integrating a wider range of datasets and improving its resilience to extreme weather conditions, thereby providing a reliable tool for climate-responsive agricultural management and water conservation strategies. Full article

(This article belongs to the Special Issue Artificial Intelligence for Sustainable Management of Groundwater Resources: New Developments, Challenges and Untapped Potentials)

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18 pages, 5592 KiB

Open AccessArticle

Influence of a Diversion Pier on the Hydraulic Characteristics of an Inverted Siphon in a Long-Distance Water Conveyance Channel

by Jian Wang, Jingyu Hu, Xiaoli Yang, Lifang Lou, Tong Mu, Dongsheng Wang and Tengfei Hu

Water 2025, 17(16), 2378; https://doi.org/10.3390/w17162378 - 11 Aug 2025

Abstract

Since large-flow water diversion began in the middle route of the South-to-North Water Diversion Project, inverted siphons have experienced varying degrees of local flow pattern disorder at their inlets and outlets, resulting in a significant decline in hydraulic performance. Taking the Kuhe inverted [...] Read more.

Since large-flow water diversion began in the middle route of the South-to-North Water Diversion Project, inverted siphons have experienced varying degrees of local flow pattern disorder at their inlets and outlets, resulting in a significant decline in hydraulic performance. Taking the Kuhe inverted siphon as a case study, a combination of numerical simulation and on-site testing was used to explore the causes of flow pattern disorder at the outlet of the inverted siphon. Meanwhile, based on the actual engineering situation, the influence of the flow pattern optimization measure of installing a 5D (five times the diameter of the pier) diversion pier at the outlet of the inverted siphon on its hydraulic characteristics was studied. Research findings indicated that before the implementation of flow pattern optimization measures, the Karman vortex street phenomenon was found to occur when water flowed through the piers; the interaction of the vortex streets behind each pier led to flow pattern disorder and affected the flow capacity. After implementation of the flow pattern optimization measures, the diversion piers had a significant inhibitory effect on the formation and development of the Karman vortex street behind the piers under the dispatching and design flow conditions. The flow velocities in each vertical layer were adjusted, with a significant improvement in the flow pattern. The hydraulic loss of the Kuhe inverted siphon was reduced by 11.5 mm, or approximately 7.8%. Under the dispatching flow condition, the water diversion flow of the Kuhe inverted siphon increased by approximately 4.11%. The water diversion capacity of the structure could be effectively enhanced by adding diversion piers to the tails of the piers. This method can be widely applied in similar open-channel long-distance water diversion projects. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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14 pages, 1446 KiB

Open AccessArticle

Factors Influencing the Spatial Distribution of Microplastics in Lakes with the Example of Dianchi Lake

by Chunnuan Deng, Yuejiao Huang, Yao Hu, Quan Zhang and Hui Zhao

Water 2025, 17(16), 2377; https://doi.org/10.3390/w17162377 - 11 Aug 2025

Abstract

The spatial law and influencing factors of microplastics in lakes are an important part of microplastic research. This study focused on exploring the influences of factors such as the underwater slope, water depth, and pollution source/shore distance of a lake on the spatial [...] Read more.

The spatial law and influencing factors of microplastics in lakes are an important part of microplastic research. This study focused on exploring the influences of factors such as the underwater slope, water depth, and pollution source/shore distance of a lake on the spatial distribution of lake MPs (microplastics). The relationships between the underwater slope, other factors, and the concentration of MPs were analyzed. The results showed that the average abundance of MPs in Dianchi Lake was 129 n/m³, and the spatial distribution pattern was higher in the lake center and lower in the lake shore. The correlation analysis showed that MP abundance was not significantly associated with distance to pollution sources or water depth, but it was significantly correlated with slope (p < 0.05) and offshore distance (p < 0.01). There was a significant negative correlation between the abundance of MPs and the underwater slope. The greater the underwater slope, the lower the abundance of MPs; the smaller the underwater slope, the higher the abundance of MPs. There was a significant positive correlation between the abundance of MPs and offshore distance. The abundance of MPs increased with increasing offshore distance. These new discoveries will help us better understand the spatial patterns of MPs in lakes. Full article

(This article belongs to the Special Issue Research on Microplastic Pollution in Water and Soil Environment)

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