Water

14 pages, 1317 KiB

Open AccessArticle

Research on the Spatiotemporal Characteristics and Driving Factors of Water Quality in the Midstream of the Chishui River

by Mingwu Bai, Jianguo Zhou, Bi Chen, Zhibin Li, Fengxue Wu, Yufeng Xiao and Jingfu Wang

Water 2025, 17(12), 1837; https://doi.org/10.3390/w17121837 - 19 Jun 2025

Viewed by 455

Abstract

This study investigated the spatiotemporal dynamics and driving forces governing water quality variationsin the Midstream of the Chishui River, a pivotal area for China’s iconic liquor production, focused on its mainstream and tributaries. Through monthly intensive sampling and monitoring, combined with water quality [...] Read more.

This study investigated the spatiotemporal dynamics and driving forces governing water quality variationsin the Midstream of the Chishui River, a pivotal area for China’s iconic liquor production, focused on its mainstream and tributaries. Through monthly intensive sampling and monitoring, combined with water quality assessment methods (single-factor evaluation and the Nemerow index method) and hydrochemical analysis, the spatiotemporal patterns and driving mechanisms of the water environment were systematically analyzed. The key findings reveal three distinct patterns. 1. Spatial heterogeneity: There is a notable difference in water quality between the main stream and tributaries, with the main stream exhibiting better water quality, while some tributaries show poorer water quality during certain months. 2. Seasonal ion variability: The proportions of Mg²⁺, Cl⁻, and SO₃²⁻ peaked during winter and spring, while concentrations of cations and anions decreased in summer and autumn. 3. Driving factors: The spatial disparity between mainstream and tributary water quality was primarily controlled by anthropogenic activities, whereas temporal variations in ionic composition were jointly influenced by basin lithology and seasonal environmental-climatic changes. Enhanced tributary management and climate adaptive monitoring strategies are proposed to safeguard water resources critical for both ecosystem integrity and specialty beverage manufacturing. Full article

(This article belongs to the Section Soil and Water)

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22 pages, 2915 KiB

Open AccessArticle

Variational Quantum Regression Application in Modeling Monthly River Discharge

by Liu Zhen and Alina Bărbulescu

Water 2025, 17(12), 1836; https://doi.org/10.3390/w17121836 - 19 Jun 2025

Viewed by 500

Abstract

In the framework of efficient water resources management, the hydrological forecast is the basis of the pertinent management of water resources. Therefore, this study applies the variational quantum regression (VQR), a novel machine learning approach inspired by quantum computing principles, to the series [...] Read more.

In the framework of efficient water resources management, the hydrological forecast is the basis of the pertinent management of water resources. Therefore, this study applies the variational quantum regression (VQR), a novel machine learning approach inspired by quantum computing principles, to the series of water discharges from a river in Romania. The models were evaluated against the quantum neural network (QNN) and other classic artificial intelligence (AI) outputs on the same dataset. Performance was assessed based on the coefficient of determination (R²), mean absolute error (MAE), and mean squared error (MSE). VQR outperformed classical neural networks and hybrid models with respect to MSE and MAE, demonstrating superior accuracy and generalization capability. Notably, the models exhibited exceptional skill in capturing monthly maxima—an area where other models often struggle, underscoring the potential of VQR as a powerful and reliable tool for hydrological forecasting, particularly in the context of nonlinear and high-variability data series. Full article

(This article belongs to the Special Issue Ecohydrology in the Context of Climate Change: Strategies for Management, Monitoring, and Modeling)

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22 pages, 3777 KiB

Open AccessArticle

Exploring the Effects of Fillers and Cultivation Conditions on Microbial-Algal Biofilm Formation and Cattle Wastewater Treatment Efficiency

by Weice Zhang, Lei Wu, Ming Li, Yuting Chen, Chenyang Li, Cong Wang and Shiyao Sun

Water 2025, 17(12), 1835; https://doi.org/10.3390/w17121835 - 19 Jun 2025

Viewed by 367

Abstract

With the rapid development of the livestock farming industry, the treatment of livestock farming wastewater has become increasingly important. The microbial-algal biofilm method has gained widespread attention for cattle wastewater treatment owing to its non-toxic nature, resistance to shock loading, and high treatment [...] Read more.

With the rapid development of the livestock farming industry, the treatment of livestock farming wastewater has become increasingly important. The microbial-algal biofilm method has gained widespread attention for cattle wastewater treatment owing to its non-toxic nature, resistance to shock loading, and high treatment efficiency. In this study, three types of substrates—polyurethane sponge, ceramic material, and moving bed biofilm reactor media—were evaluated. The formation of biofilms was assessed through variations in chlorophyll content, microscopic observations, and measurements of biofilm dry weight and attachment rate. Biofilm characterization on the different substrates was conducted via Fourier transform infrared spectroscopy, confocal laser scanning microscopy, and scanning electron microscopy. The results demonstrated that polyurethane sponge was the most effective substrate. Furthermore, a single-factor experiment was conducted to optimize the cultivation conditions for the microbial-algal biofilms and identify the optimal parameters based on the ability of the biofilm to remove COD, TN, TP, and NH₄⁺-N. The optimal conditions were as follows: an illumination intensity of 8000 lux, red light, a temperature of 20 °C, a pH of 7, and an aeration intensity of 8 L/min. Under these conditions, the pollutant removal rates were exceptionally high: ~73.4% for COD, 51.8% for TP, 57.0% for TN, and 75.1% for NH₄⁺-N. Full article

(This article belongs to the Special Issue Water Reclamation and Reuse in a Changing World)

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17 pages, 2398 KiB

Open AccessArticle

Mesoporous SBA-15-Supported Ceria–Cadmium Composites for Fast Degradation of Methylene Blue in Aqueous Systems

by Dănuţa Matei, Abubakar Usman Katsina, Diana-Luciana Cursaru and Sonia Mihai

Water 2025, 17(12), 1834; https://doi.org/10.3390/w17121834 - 19 Jun 2025

Viewed by 478

Abstract

A composite photocatalyst of ceria–cadmium supported on mesoporous SBA-15 silica was synthesized and employed for the aqueous methylene blue (MB) degradation. The composites were prepared using an incipient wetness impregnation technique and a conventional sol–gel approach with triblock copolymer P123 as a structure-directing [...] Read more.

A composite photocatalyst of ceria–cadmium supported on mesoporous SBA-15 silica was synthesized and employed for the aqueous methylene blue (MB) degradation. The composites were prepared using an incipient wetness impregnation technique and a conventional sol–gel approach with triblock copolymer P123 as a structure-directing agent for SBA-15 preparation, enabling the uniform dispersion of CeO₂ and Cd species within the SBA-15 framework. The physicochemical properties of both CeO₂/SBA-15 and Cd-CeO₂/SBA-15 composites were analyzed using small-angle and wide-angle XRD, FT-IR spectroscopy, SEM, TEM, EDX spectroscopy, N₂ physisorption at 77 K, and UV-Vis spectroscopy. The findings revealed that the SBA-15 support retained its well-ordered hexagonal mesostructure in both the ceria–SBA-15 and SBA-15-supported cadmium–ceria (Cd-CeO₂) composites. The highest degradation efficiency of 96.40% was achieved under optimal conditions, and kinetic analysis using the Langmuir–Hinshelwood model indicated that the MB degradation process followed pseudo-first-order kinetics, with a strong correlation coefficient (R² = 0.9925) and a rate constant (k) of 0.02532 min⁻¹. Under irradiation, the Cd-CeO₂/SBA-15 composites exhibited superior photocatalytic activity compared to the pristine components, owing to the synergistic interaction between ceria and cadmium, enhanced light absorption, and improved charge carrier separation. The recyclability test demonstrated that the degradation efficiency decreased slightly from 96.40% to 94.86% after three cycles, confirming the stability and reusability of Cd-CeO₂/SBA-15 composites. The photocatalytic process demonstrated a favorable electrical energy per order (EE/O) value of 281.8 kWh m⁻³, indicating promising energy efficiency for practical wastewater treatment. These results highlight the excellent photocatalytic performance and durability of the synthesized Cd-CeO₂/SBA-15 composites, making them promising candidates for facilitating the photocatalytic decomposition of MB and other dye molecules in water treatment applications. Full article

(This article belongs to the Special Issue Advanced Design and Synthesis of Novel Photocatalyst Materials for Wastewater Remediation)

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27 pages, 870 KiB

Open AccessReview

Thermochemical Conversion of Sewage Sludge: Progress in Pyrolysis and Gasification

by Yibo Hu and Ziwei Chen

Water 2025, 17(12), 1833; https://doi.org/10.3390/w17121833 - 19 Jun 2025

Cited by 1 | Viewed by 711

Abstract

Sewage sludge, as a by-product of wastewater treatment, poses severe environmental challenges due to its high moisture, ash, and heavy metal content. Thermochemical conversion technologies, including pyrolysis and gasification, offer promising pathways for transforming sludge into valuable products such as bio-oil, biochar, and [...] Read more.

Sewage sludge, as a by-product of wastewater treatment, poses severe environmental challenges due to its high moisture, ash, and heavy metal content. Thermochemical conversion technologies, including pyrolysis and gasification, offer promising pathways for transforming sludge into valuable products such as bio-oil, biochar, and syngas. This paper systematically reviews recent advancements in pyrolysis and gasification, focusing on process optimization and catalyst development to enhance product quality and energy recovery. In pyrolysis, factors such as temperature, residence time, and heating rate significantly influence product yields and properties, while catalytic and co-pyrolysis approaches further improve product structure and reduce environmental risks. In gasification, parameters like the equivalence ratio, steam-to-sludge ratio, and catalyst application are key to enhancing syngas yield and quality, with biomass co-gasification offering additional benefits. Despite substantial progress, commercialization remains challenged by high operational costs, catalyst durability, and environmental impacts. Future research should emphasize improving sludge pretreatment, optimizing thermochemical processes, developing efficient and cost-effective catalysts, and addressing critical issues such as bio-oil quality, tar management, and syngas purification to promote the industrial application of these technologies. Full article

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

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18 pages, 3188 KiB

Open AccessArticle

Experimental and Theoretical Evaluation of Buoyancy Reduction in Saturated Clay Soils

by Tao Gao, Yongliang Xu, Xiaomin Zhou, Yubo Wang and Hongyan Liu

Water 2025, 17(12), 1832; https://doi.org/10.3390/w17121832 - 19 Jun 2025

Viewed by 282

Abstract

The rational calculation of groundwater buoyancy directly impacts the safety of underground engineering. However, there is still no consensus on whether the reduction of groundwater buoyancy should be considered, and a theoretical explanation and quantification of buoyancy reduction in clayey soils is lacking. [...] Read more.

The rational calculation of groundwater buoyancy directly impacts the safety of underground engineering. However, there is still no consensus on whether the reduction of groundwater buoyancy should be considered, and a theoretical explanation and quantification of buoyancy reduction in clayey soils is lacking. Based on laboratory engineering model tests, this study observed and analyzed the phenomenon of buoyancy reduction in saturated clayey soils. The contact area ratio of gravity water, calculated from geotechnical test data, was compared with the reduction slope. The experimental results indicated that the reduction slope of the fitted line between the static water head in the silty clay layer and the buoyancy water head was 0.8692. And theoretical analysis showed that the distribution of interparticle pore water pressure tends to attenuate from the pore center to the soil particle surface, suggesting a reduction in buoyancy head compared to the groundwater level. The reduction slope is theoretically equal to the contact area ratio of gravity water. Additionally, since limitations in current techniques for generalizing the soil–water constitutive models affect the reduction slope, this study proposes a method for determining the buoyancy reduction slope in saturated clayey soil based on the theory that interparticle pore water pressure distribution attenuates from the pore center to the soil particle surface. This method could potentially change the existing conceptual framework for buoyancy design in underground structures. Full article

(This article belongs to the Section Soil and Water)

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19 pages, 6897 KiB

Open AccessArticle

The Evolution of Sediment Microorganisms During the Transition from Freshwater to Seawater and Their Dependence on Water Quality

by Qingyu Zhu, Lingli Min, Wenzhou Zhang, Shouping Ji and Yulang Chi

Water 2025, 17(12), 1831; https://doi.org/10.3390/w17121831 - 19 Jun 2025

Viewed by 486

Abstract

Estuarine ecosystems, characterized by dynamic salinity gradients and complex physicochemical interactions, serve as critical transition zones between freshwater and marine environments. This study investigates the spatial evolution of sediment microbial communities across a freshwater–seawater continuum and their correlations with water quality parameters. Five [...] Read more.

Estuarine ecosystems, characterized by dynamic salinity gradients and complex physicochemical interactions, serve as critical transition zones between freshwater and marine environments. This study investigates the spatial evolution of sediment microbial communities across a freshwater–seawater continuum and their correlations with water quality parameters. Five sampling zones (upstream, midstream, downstream, transition zone, and ocean) were established in a typical estuary (Kuiyu Park, China). High-throughput 16S rRNA sequencing revealed significant shifts in microbial composition, with dominant phyla including Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Alpha diversity decreased from freshwater to the transition zone but rebounded in seawater, suggesting habitat filtering and niche differentiation. Redundancy analysis identified salinity, dissolved oxygen, nutrients, and heavy metals as key drivers of microbial community structure. Functional predictions highlighted metabolic adaptations such as methanogenesis, sulfur oxidation, and aerobic chemoheterotrophy across zones. This study explores how sediment microorganisms adapt to water quality variations during the freshwater–seawater transition, offering insights into estuarine resilience under global change. These findings elucidate microbial assembly rules in estuarine ecosystems and provide insights for ecological management under global environmental change. Full article

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

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16 pages, 2241 KiB

Open AccessArticle

Microvascular Responses in the Dermis and Muscles After Balneotherapy: Results from a Prospective Pilot Histological Study

by Traian-Virgiliu Surdu, Monica Surdu, Olga Surdu, Irina Franciuc, Elena-Roxana Tucmeanu, Alin-Iulian Tucmeanu, Lucian Serbanescu and Vlad Iustin Tica

Water 2025, 17(12), 1830; https://doi.org/10.3390/w17121830 - 19 Jun 2025

Viewed by 401

Abstract

Background: This study aimed to assess the feasibility of conducting a prospective study to evaluate histological changes in skin and muscle tissues after two weeks of balneotherapeutic intervention, as described in Romanian medical regulations. Methods: Thirty-five patients participated in this study, thirty of [...] Read more.

Background: This study aimed to assess the feasibility of conducting a prospective study to evaluate histological changes in skin and muscle tissues after two weeks of balneotherapeutic intervention, as described in Romanian medical regulations. Methods: Thirty-five patients participated in this study, thirty of whom received balneotherapy (a cold mud ointment or a mud pack, or a mud bath, and/or a salted water bath) and five received hydrotherapy (the witness plot). Inclusion and exclusion criteria were applied. Twenty-four hours after discharge, a tegument and muscle biopsy were performed, and fragments were histologically prepared. Results: In the blade evidence analysis, the increased caliber and number of open capillaries and the presence of angiogenesis vessels were statistically significant (p = 0.001 < α = 0.05) for the cold mud ointment and mud pack compared with the witness and mud bath plots. The number of angiogenesis blood vessels was higher in the dermis (p < 0.05 *) with the mud pack plot and in the muscle with the mud cold ointment (p < 0.05). The histological study showed that two weeks of therapeutic intervention produced evidence-based proof in the dermis and muscle tissues, which was persistent at least twenty-four hours after the completion of the balneal course. The results encourage the team to continue the histological approach using modern techniques. Full article

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

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18 pages, 677 KiB

Open AccessArticle

Optimizing Hydrodynamic Regulation in Coastal Plain River Networks in Eastern China: A MIKE11-Based Partitioned Water Allocation Framework for Flood Control and Water Quality Enhancement

by Haijing Gao, Qian Wang, Zheng Zhou, Wan Wu, Weiying Wang, Yan Li, Jianyong Hu, Puxi Li, Yongpeng Zhang and Wenjing Hu

Water 2025, 17(12), 1829; https://doi.org/10.3390/w17121829 - 19 Jun 2025

Viewed by 357

Abstract

The effective management of river networks in coastal plains is crucial to flood control, water quality improvement, and sustainable flow distribution. This study aims to optimize the hydrodynamic performance of a plain river network in eastern China through water diversion and circulation scheduling, [...] Read more.

The effective management of river networks in coastal plains is crucial to flood control, water quality improvement, and sustainable flow distribution. This study aims to optimize the hydrodynamic performance of a plain river network in eastern China through water diversion and circulation scheduling, addressing challenges such as channel narrowing and sedimentation. This research study utilized a partitioned water allocation approach modeled in MIKE11 to simulate the effects of various diversion projects, including locks and connecting rivers, on the primary conveyance channel and supporting rivers. The simulation results indicated that flow velocities exceeded 0.1 m/s in most rivers, with significant improvements in flood discharge and water quality in the main conveyance channel and one supporting river. However, some sections of the network showed poor hydrodynamic performance due to narrow channels, encroachment, and sedimentation, and smaller rivers exhibited inadequate flow capacity. The findings provide critical insights for optimizing hydrodynamic regulation in coastal plain river systems, emphasizing the need to address specific issues to enhance overall network performance and flood resilience. Full article

(This article belongs to the Special Issue Recent Advances in Hydraulic Machinery and Its Application in Marine Engineering)

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12 pages, 979 KiB

Open AccessArticle

Dynamics of Plant Litter Sodium Storage in a Subtropical Forest Headwater Stream

by Yuchen Zheng, Siying Chen, Yan Peng, Zemin Zhao, Chaoxiang Yuan, Ji Yuan, Nannan An, Xiangyin Ni, Fuzhong Wu and Kai Yue

Water 2025, 17(12), 1828; https://doi.org/10.3390/w17121828 - 19 Jun 2025

Viewed by 380

Abstract

Headwater streams serve as a crucial link between forest and downstream aquatic ecosystems and also act as crucial agents in carbon (C) and nutrient storage and flux. These aquatic systems play a pivotal role in regulating biogeochemical cycles. Plant litter is an important [...] Read more.

Headwater streams serve as a crucial link between forest and downstream aquatic ecosystems and also act as crucial agents in carbon (C) and nutrient storage and flux. These aquatic systems play a pivotal role in regulating biogeochemical cycles. Plant litter is an important contributor of nutrients to headwater streams, having significant impacts on downstream ecosystems. However, current research predominantly focuses on the dynamics of plant litter C and nutrients such as nitrogen and phosphorus, and we know little about those of nutrients such as sodium (Na). In this study, we conducted a comprehensive evaluation of the annual dynamics of plant litter Na storage within a subtropical headwater stream. This study took place over a period of one year, from March 2021 to February 2022. Our results showed that (1) the average annual concentration and storage of litter Na was 538.6 mg/kg and 2957.6 mg/m², respectively, and litter Na storage exhibited a declining trend from stream source to mouth, while demonstrating significantly higher values during the rainy season compared to the dry season; (2) plant litter type had significant impacts on Na concentration and storage, with leaf, twig, and fine woody debris accounting for the majority of litter Na storage; and (3) hydrological (precipitation, discharge) and physicochemical (water temperature, flow velocity, pH, dissolved oxygen, alkalinity) factors jointly affected Na storage patterns. Overall, the results of this study clearly reveal the dynamic characteristics of Na storage in plant litter in a subtropical forest headwater stream, which contributes to a more comprehensive understanding of the role of headwater streams in nutrient cycling and the dynamic changes of nutrients along with hydrological processes. This research will enhance our predictive understanding of nutrient cycling at the watershed scale. Full article

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

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20 pages, 4612 KiB

Open AccessReview

A Review of Low-Cost Point-of-Use Water Treatment Solutions Addressing Water Access and Quality in Resource-Limited Settings

by Dorcas Cheptoo Sombei, Cleophas Achisa Mecha and Martha N. Chollom

Water 2025, 17(12), 1827; https://doi.org/10.3390/w17121827 - 19 Jun 2025

Viewed by 884

Abstract

Access to safe, clean drinking water is a critical challenge across many resource-constrained settings, especially in developing economies. Large-scale water treatment technologies are often available in urban areas, whereas such centralized systems are unavailable in rural and remote areas due to high infrastructure [...] Read more.

Access to safe, clean drinking water is a critical challenge across many resource-constrained settings, especially in developing economies. Large-scale water treatment technologies are often available in urban areas, whereas such centralized systems are unavailable in rural and remote areas due to high infrastructure costs, rugged terrains, and maintenance challenges. To address this challenge, point-of-use (PoU) water treatment systems can fill this critical gap. This study critically evaluates the role low-cost PoU water treatment solutions play as a promising alternative to address water access and quality aspects in remote rural areas. The study explores the present state of global water sources, the challenges of water scarcity and pollution, and the limitations of existing large-scale treatment technologies. It highlights the motivation behind PoU systems and provides an in-depth analysis of various low-cost technologies, including operational principles, performance efficiency, and economic viability. Embedded in this study is a concise evaluation of the sustainability of these solutions in addressing water access and quality challenges in resource-limited regions. Finally, the study proposes solutions and perspectives on improving PoU systems and scale-up of the systems for large-scale applications to facilitate increased access to clean and safe water. Full article

(This article belongs to the Special Issue Advanced Technologies on Water and Wastewater Treatment)

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21 pages, 2628 KiB

Open AccessArticle

Water-Richness Evaluation of Sandstone Aquifer Based on Set Pair Analysis Variable Fuzzy Set Coupling Method: A Case Study on Bayangaole Mine, China

by Kaihua Liang, Yueyue Li, Yuanlin Bai, Weijie Zhang, Chenghao Han, Daolei Xie, Shengjian Liang and Bowen Xi

Water 2025, 17(12), 1826; https://doi.org/10.3390/w17121826 - 19 Jun 2025

Viewed by 340

Abstract

The Jurassic aquifer in Northwest China is the key aquifer for mine water filling, which is significant due to its loose structure, large porosity, strong rock permeability, and fracture development characteristics. In addition, the water richness in space is extremely uneven, and many [...] Read more.

The Jurassic aquifer in Northwest China is the key aquifer for mine water filling, which is significant due to its loose structure, large porosity, strong rock permeability, and fracture development characteristics. In addition, the water richness in space is extremely uneven, and many coal mine roof water inrush events are closely related to it. A case of evaluation of water-richness of the roof sandstone in the 3-1 coal seam of the Bayangaole minefield was analyzed in depth, and the evaluation index system is established based on lithology and structural characteristics. Specifically, the evaluation indexes are under the influence of the influencing factors of lithology, the density of fault intersection endpoints, and the density of fault scale and the strength of folds as the influencing factors of structure. On this basis, the set pair analysis-variable fuzzy set coupling evaluation method is introduced to form a targeted water-rich evaluation model of a roof sandstone aquifer. By using the coupling method of set pair analysis and variable fuzzy set, a targeted evaluation model is formed to realize the organic integration of indicators. Through the comprehensive analysis of the relative zoning of water abundance and the data from the borehole pumping (drainage) test, the distribution of water abundance grade in the study area is clarified. Full article

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

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15 pages, 4908 KiB

Open AccessArticle

A Comparative Assessment of Surface Water Quality in Lake Yuriria, Guanajuato, Using the Water Quality Index

by Juan Manuel López-Gutiérrez, Elizabeth Ramírez-Mosqueda, Glenda Edith Cea-Barcia, Graciela M. L. Ruiz-Aguilar, Israel Castro-Ramírez, Sarai Camarena-Martínez, César Arturo Ilizaliturri-Hernández, Diana Olivia Rocha-Amador and Rogelio Costilla-Salazar

Water 2025, 17(12), 1825; https://doi.org/10.3390/w17121825 - 19 Jun 2025

Viewed by 536

Abstract

The pollution of water bodies has deteriorated the quality of freshwater and the health of the natural ecosystem. In the present study, the water quality index (WQI) was used to evaluate the spatial and temporal contamination levels in Lake Yuriria, Guanajuato, Mexico. Water [...] Read more.

The pollution of water bodies has deteriorated the quality of freshwater and the health of the natural ecosystem. In the present study, the water quality index (WQI) was used to evaluate the spatial and temporal contamination levels in Lake Yuriria, Guanajuato, Mexico. Water quality was monitored at 27 different locations (monitoring points) in the dry season (April) and after the rainy season (November), measuring 21 physicochemical water parameters, 2 biological parameters, and 19 metal concentrations. The data analysis revealed that Yuriria Lake is a eutrophic water body. Six monitoring points exhibited a poor WQI (25–50) in April, and seven monitoring sites were classified as having poor water quality in November. The remaining monitoring points showed a WQI categorized as fair (51–70) in both periods. The present study analyzes an extensive distribution of monitoring points over the lake’s surface in two periods, showing a significant spatial and temporal representation of water quality. In addition, the major pollution sources identified include agricultural runoff and effluents from a nearby waterway and freshwater river. Finally, the key physicochemical parameters that determined the water quality were identified. BOD₅, NH₄⁺, P, orthophosphates, DO, conductivity, TSS, and color were linked to anthropogenic pollution sources, and Li, Ni, Zn, Cd, Ba, and Pb concentrations were linked to natural contamination sources. This study demonstrates the utility and versatility of these methodologies in water quality research, and it is the first spatial and temporal WQI analysis of Yuriria Lake. Full article

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

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17 pages, 3762 KiB

Open AccessArticle

Spatiotemporal Dynamics of Nitrogen and Phosphorus in the Water and Sediment from the Source Reservoir of the Mid-Route of China’s South-to-North Water Diversion Project

by Yuanyuan Zhang, Donghua Zhang, Yue Li, Xueqing Han, Xinyu Wang, Ji’ao Zhang, Kaidi Gu, Shuaijie Sun, Qigen Liu and Jun Lv

Water 2025, 17(12), 1824; https://doi.org/10.3390/w17121824 - 18 Jun 2025

Viewed by 446

Abstract

To investigate the spatiotemporal distribution characteristics of nitrogen and phosphorus in the water and sediment of the Danjiangkou Reservoir, the source of the Middle Route of China’s South-to-North Water Diversion Project, we designed a year-long monitoring program. The water and sediment samples were [...] Read more.

To investigate the spatiotemporal distribution characteristics of nitrogen and phosphorus in the water and sediment of the Danjiangkou Reservoir, the source of the Middle Route of China’s South-to-North Water Diversion Project, we designed a year-long monitoring program. The water and sediment samples were collected from 13 sampling points in the upstream and downstream areas over the year. The results revealed significant spatial heterogeneity in N and P concentrations, with higher levels of total nitrogen, nitrate nitrogen, and nitrite nitrogen in the upstream area compared to the downstream area (p < 0.01). Total phosphorus was also significantly higher in the upstream area (p < 0.05). Seasonal variations were observed, with TN and TP levels peaking in February and August, respectively. The TN:TP ratio indicated a severe P-limited state in most periods, transitioning to a co-limited state of N and P during summer. Sediment analysis showed that TN and TP concentrations were higher in the upstream area, with no significant differences between upstream and downstream on an annual basis, exhibiting strong stoichiometric internal stability. However, seasonal differences were noted, particularly in February and November. This study highlights the complex interactions between water and sediment, emphasizing the role of sediment resuspension, water flow, and seasonal changes in nutrient dynamics. These findings provide a scientific basis for the management and protection of water quality in the Danjiangkou Reservoir, ensuring its role as a critical water source for the South-to-North Water Diversion Project. Full article

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

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20 pages, 2071 KiB

Open AccessArticle

Leakage Break Diagnosis for Water Distribution Network Using LSTM-FCN Neural Network Based on High-Frequency Pressure Data

by Sen Peng, Hongyan Zeng, Xingqi Wu and Guolei Zheng

Water 2025, 17(12), 1823; https://doi.org/10.3390/w17121823 - 18 Jun 2025

Viewed by 332

Abstract

Water distribution is no arguably the most important factor in modern times, and water leak breaks are typically a consequence of failures in water distribution networks. But pipeline leakage breaks have become one of the most frequent consequences affecting the operation of water [...] Read more.

Water distribution is no arguably the most important factor in modern times, and water leak breaks are typically a consequence of failures in water distribution networks. But pipeline leakage breaks have become one of the most frequent consequences affecting the operation of water distribution networks (WDNs) and monitoring their health is often complicated. This paper proposes a leakage break diagnosis method based on an LSTM-FCN neural network model from high-frequency pressure data. Data preprocessing is used to avoid the influence of noise and information redundancy, and the LSTM module and the FCN module are used to extract and concatenate different leakage break features. The leakage break feature is sent to a dense classifier to obtain the predicted result. Two sample sets, steady state and water consumption, were obtained to verify the performance of the proposed leakage break diagnosis method. Three other models, LSTM, FCN, and ANN, were compared using the sample sets. The proposed LSTM-FCN model achieved an overall accuracy of 85% for leakage break detection, illustrating that the model could effectively learn the leakage break features in high-frequency time-series data and had a high accuracy for leakage break detection and leakage break degree prediction of new samples in WDNs. Meanwhile, the proposed method also had good adaptability to the variations in water consumption in actual WDNs. Full article

(This article belongs to the Special Issue Numerical and Experimental Methods, Data Analyses, Digital Twin, IoT Machine Learning and AI in Water Sciences)

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23 pages, 7071 KiB

Open AccessArticle

Numerical Simulation of Ship Wave Characteristics Under Different Navigation Conditions in the Restricted Waterway of the Pinglu Canal

by Chu Zhang, Tiejun Cheng, Shishuang Wu, Jian Pan, Jiacheng You, Xiangyu Xu, Jianan Shi, Sudong Xu and Jianxin Hao

Water 2025, 17(12), 1822; https://doi.org/10.3390/w17121822 - 18 Jun 2025

Viewed by 362

Abstract

The Pinglu Canal is a strategic inland restricted waterway under construction in southwest China. Its ship wave superposition characteristics under conditions of high-density shipping and large ships may threaten navigation safety, but little related research has been performed. Based on the Pinglu Canal [...] Read more.

The Pinglu Canal is a strategic inland restricted waterway under construction in southwest China. Its ship wave superposition characteristics under conditions of high-density shipping and large ships may threaten navigation safety, but little related research has been performed. Based on the Pinglu Canal project, this study uses the XBeach numerical model, which is validated by field observations on the Chengzi River waterway, to analyze the ship wave characteristics under single-ship navigation (SN) and two-ship navigation in opposite directions (2NOD). The results show the influences of ship type and water depth. For SN, secondary waves of the navigation administration boat (NAB) dominate, with wave height decreasing as water depth increases. Larger cargo ships (CSs) present significant primary wave effects and a complex relationship between the secondary wave’s height and water depth. For 2NOD, the NAB wave effect is stronger due to superposition. As for larger CSs, the primary wave effect is significantly enhanced and occupies the dominant position, with secondary wave height tending to increase with the increase in water depth. The study reveals the characteristics of single-ship and two-ship waves in the Pinglu Canal, providing a theoretical basis and technical support for ship wave risk assessment and ecological revetment design. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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16 pages, 1827 KiB

Open AccessArticle

Tropical Wetlands as Nature-Based Solutions to Remove Nutrient and Organic Inputs from Stormwater Discharge and Wastewater Effluent in Urban Environments

by Flavia Byekwaso, Gabriele Weigelhofer, Rose Kaggwa, Frank Kansiime, Guenter Langergraber and Thomas Hein

Water 2025, 17(12), 1821; https://doi.org/10.3390/w17121821 - 18 Jun 2025

Viewed by 537

Abstract

Natural wetlands are critical water quality regulators, especially in developing tropical countries. The Lubigi wetland is a large urban wetland in Kampala, the largest city in Uganda in Africa. We studied whether stormwater discharge and wastewater effluent from a nearby stormwater channel and [...] Read more.

Natural wetlands are critical water quality regulators, especially in developing tropical countries. The Lubigi wetland is a large urban wetland in Kampala, the largest city in Uganda in Africa. We studied whether stormwater discharge and wastewater effluent from a nearby stormwater channel and a sewage treatment plant in the western part of the city were cleaned as they flowed through the wetland. Despite the significant pollution, the wetland removed ammonium-nitrogen, orthophosphate, and particulate nutrients during both seasons, achieving removal rates ranging from 50 to 60% for orthophosphate but only 20–40% for ammonium-nitrogen. Overall, seasonal differences in loads and retention rates of nutrient and organic matter inputs were minimal. Interestingly, the wetland mostly released nitrate and nitrite during water passage through the wetland, most likely due to the mineralization of organic nitrogen and agricultural run-off during rainy events in the wet season. However, the limited capacity of the sewage treatment plant and untreated stormwater discharge from the Nsooba main channel reduced the wetland’s ability to clean water. The insufficient carrying capacity of the treatment plant and the release of untreated sewage into the wetland significantly impact the self-purification capacity of the Lubigi wetland. Thus, the concept of Nature-Based Solutions is ineffective if the wetland systems are overloaded. Full article

(This article belongs to the Topic Wastewater Treatment by Physical, Chemical, Photochemical, and Biological Processes, and Their Combinations)

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24 pages, 2488 KiB

Open AccessArticle

Rapid SWMM Catchment Prototyping Using Fuzzy Logic: Analyzing Catchment Features for Enhanced Efficiency

by Jacek Dawidowicz and Rafał Buczyński

Water 2025, 17(12), 1820; https://doi.org/10.3390/w17121820 - 18 Jun 2025

Viewed by 274

Abstract

Parameterization of SWMM subcatchments is labor-intensive and a major source of model uncertainty. This study presents the Rapid Catchment Generator (RCG), a fuzzy logic framework that derives hydraulic width, average slope, and impervious fraction from three easily accessible descriptors—area, landform type, and land [...] Read more.

Parameterization of SWMM subcatchments is labor-intensive and a major source of model uncertainty. This study presents the Rapid Catchment Generator (RCG), a fuzzy logic framework that derives hydraulic width, average slope, and impervious fraction from three easily accessible descriptors—area, landform type, and land cover type—and inserts them directly into SWMM input files. A sensitivity analysis of 116,640 synthetic simulations confirmed that width, slope, and imperviousness are the dominant controls on runoff and infiltration. Their relationships are encoded in triangular membership functions covering nine geomorphic classes and twelve imperviousness classes, linked through expert-calibrated Mamdani rules. Validation on a calibrated 37-subcatchment, 10-hectare urban basin in Wrocław, Poland, showed Mean Absolute Percentage Errors of 15.9–16.0% for total runoff, 19% for infiltration, and 29–37% for peak flow, while preserving hydrograph shape. RCG thus reduces model setup time and provides a transparent, reproducible starting point for rapid scenario screening and subsequent fine-scale calibration. Full article

(This article belongs to the Section Hydrology)

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13 pages, 2162 KiB

Open AccessArticle

Characterization of Transboundary Transfer Mechanisms for Improved Plastic Waste Management: A Study on the U.S.–Mexico Border

by Carol Maione, Domenico Vito, Gabriela Fernandez and Paolo Trucco

Water 2025, 17(12), 1819; https://doi.org/10.3390/w17121819 - 18 Jun 2025

Viewed by 438

Abstract

The vast majority of ocean plastics originate from land and are transported over long distances to their final sink. Yet, our current understanding of transfer mechanisms through rivers and estuaries remains poor due to a lack of consistent methods for assessing and monitoring [...] Read more.

The vast majority of ocean plastics originate from land and are transported over long distances to their final sink. Yet, our current understanding of transfer mechanisms through rivers and estuaries remains poor due to a lack of consistent methods for assessing and monitoring plastic waste. In this study, we quantify and characterize the abundance of plastics in the Tijuana River estuary, located along the U.S.–Mexico border. We found a total of 2804 plastic debris items, of which 79.3% were sampled during heavy rainfalls and 20.7% during the dry period. Overall, most plastics were attributed to five economic sectors: packaging, food, construction, fishing, and tourism, highlighting losses during the use and waste management phases of the plastic’s value chain. Based on the results of the analysis, consistent monitoring of plastic pollution is recommended for managing variable plastic loads. Full article

(This article belongs to the Special Issue Water Pollution Control and Ecological Restoration)

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24 pages, 6191 KiB

Open AccessArticle

The Impact of Climate Change on Agricultural Nonpoint Source Pollution in the Sand River Catchment, Limpopo, South Africa

by Tlhogonolofatso A. Chuene, Remilekun T. Akanbi and Hector Chikoore

Water 2025, 17(12), 1818; https://doi.org/10.3390/w17121818 - 18 Jun 2025

Viewed by 415

Abstract

Understanding the impact of climate change on agricultural nonpoint source (NPS) pollution is crucial for developing effective adaptation strategies and reducing vulnerabilities where such challenges exist. This study evaluated the impact of precipitation and temperature variations on Total Inorganic Nitrogen (TIN), Total Inorganic [...] Read more.

Understanding the impact of climate change on agricultural nonpoint source (NPS) pollution is crucial for developing effective adaptation strategies and reducing vulnerabilities where such challenges exist. This study evaluated the impact of precipitation and temperature variations on Total Inorganic Nitrogen (TIN), Total Inorganic Phosphorus (TIP), and sediment loads in the Sand River Catchment (SRC) using the Soil and Water Assessment Tool plus (SWAT+). One-way analysis of variance (ANOVA) was used to determine the significance (p < 0.05) of the relationships (R²) between precipitation and temperature on sediment, TIN, and TIP loads in the SRC. SWAT+ calibration and validation demonstrated that the statistical indices (NSE and R² ≥ 0.72; −17.30 ≤ PBIAS ≤ 14.74) fell within an acceptable range. Results indicated a significant influence of average monthly precipitation (p < 0.0001) and temperature (p ≤ 0.004) on sediment, TIN, and TIP loads. In addition, a decrease in average annual precipitation led to a decline in sediment, TIN, and TIP loads (R² ≥ 0.55), with the average annual temperature increasing in the same period (R² ≤ 0.23). This study confirms that climate change contributes to agricultural NPS pollution in the SRC and highlights the need to employ suitable adaptation strategies for pollution control in the catchment. Full article

(This article belongs to the Section Hydrology)

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22 pages, 2333 KiB

Open AccessArticle

Ecological Assessment of Rivers Under Anthropogenic Pressure: Testing Biological Indices Across Abiotic Types of Rivers

by Dariusz Halabowski, Iga Lewin, Małgorzata Bąk, Wojciech Płaska, Joanna Rosińska, Jacek Rechulicz and Małgorzata Dukowska

Water 2025, 17(12), 1817; https://doi.org/10.3390/w17121817 - 18 Jun 2025

Viewed by 400

Abstract

The ecological assessment of rivers under the Water Framework Directive (WFD) requires the use of biological quality elements (BQEs) across defined abiotic types of rivers. However, limited evidence exists on how well biological indices perform across multiple typological classes, particularly under the influence [...] Read more.

The ecological assessment of rivers under the Water Framework Directive (WFD) requires the use of biological quality elements (BQEs) across defined abiotic types of rivers. However, limited evidence exists on how well biological indices perform across multiple typological classes, particularly under the influence of complex, overlapping stressors. This study evaluated the diagnostic performance of four biological indices (IO—diatoms, MIR—macrophytes, MMI_PL—benthic macroinvertebrates, and EFI + PL—fish) in 16 river sites in southern Poland. These were classified into four abiotic types (5, 6, 12, and 17) and subjected to varying levels of human pressure. Biological, physical and chemical, and hydromorphological data were collected along environmental gradients including conductivity, nutrient enrichment, and habitat modification. Statistical analyses were used to evaluate patterns in community composition and index responsiveness. The IO and MMI_PL indices were the most consistent and sensitive in distinguishing between reference and degraded river conditions. MIR and EFI + PL were more variable, especially in lowland rivers, and showed stronger associations with habitat structure and oxygen levels. Conductivity emerged as a key driver of biological responses across all BQEs, with clear taxonomical shifts observed. The results support the need to consider both typological context and local environmental variation in ecological classification. The findings underscore the need for typology-aware, pressure-specific biomonitoring strategies that combine multiple organism groups and integrate continuous environmental variables. Such approaches can enhance the ecological realism and diagnostic accuracy of river assessment systems, supporting more effective water resource management across diverse hydroecological contexts. Full article

(This article belongs to the Special Issue Freshwater Species: Status, Monitoring and Assessment)

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24 pages, 3000 KiB

Open AccessArticle

Identifying Worst Transient Cases and Optimizing Surge Protection for Existing Water Networks

by Hossam Mohamed Ahmed, Yehya Emad Imam, Hamdy Ahmed El-Ghandour and Amgad Saad Elansary

Water 2025, 17(12), 1816; https://doi.org/10.3390/w17121816 - 17 Jun 2025

Viewed by 454

Abstract

Previous studies of transients in existing water distribution networks (WDNs) accounted for only single worst cases in optimizing surge protection measures, considered only pressure at pipe end nodes, and did not examine the effect of regulating the duration of demand increase. This study [...] Read more.

Previous studies of transients in existing water distribution networks (WDNs) accounted for only single worst cases in optimizing surge protection measures, considered only pressure at pipe end nodes, and did not examine the effect of regulating the duration of demand increase. This study presents a comprehensive model for identifying the minimal set of worst transient cases for which optimized surge protection achieves zero Surge Damage Potential Factor (SDPF) for all transient loading cases. The model introduces

S D P F_{P}

to account for pressure at all computational nodes along pipes, as opposed to relying on

S D P F_{N}

, which considers pressure at pipe end nodes only. The existing New York Tunnel network was used for model validation and for determining the optimal diameters for additional duplicate pipes to achieve higher pressure under steady-state conditions and protect the network from transients due to demand increase. Compared to previous studies, the model achieved

S D P F_{N} = 0

with a lower cost for sudden demand increase at a single predefined node. For concurrent sudden demand increase at two nodes, the model identified a total of 8 critical transient cases and corresponding optimum duplicate pipe diameters that achieved

S D P F_{N} = 0

and

S D P F_{P} = 0

with 46% and 74% higher costs than previous studies, respectively. The higher costs are necessary; previous studies did not achieve zero

S D P F_{N}

and

S D P F_{P}

in 39% and 91% of transient cases, respectively. To reduce duplicate pipe costs, the model was used to examine the effect of regulating the duration for a gradual demand increase. Using only the pipes optimized for steady-state service, the minimum duration for satisfying the transient pressure constraints was identified as ~260 s for the concurrent demand increase scenario. Slight relaxation of the minimum allowable pressure constraint allows a reduction in the duration to 150 s. For applying a demand increase over a smaller duration, duplicate pipes would be needed and can be optimized using the model. These results indicate the advantage of the proposed model in achieving full protection of existing WDNs while maintaining computational efficiency and cost-effectiveness. Full article

(This article belongs to the Special Issue Machine Learning Applications in the Water Domain)

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10 pages, 1104 KiB

Open AccessArticle

Comparative Analysis of Extreme Flood Characteristics in the Huai River Basin: Insights from the 2020 Catastrophic Event

by Youbing Hu, Shijin Xu, Kai Wang, Shuxian Liang, Cui Su, Zhigang Feng and Mengjie Zhao

Water 2025, 17(12), 1815; https://doi.org/10.3390/w17121815 - 17 Jun 2025

Viewed by 380

Abstract

Catastrophic floods in monsoon-driven river systems pose significant challenges to flood resilience. In July 2020, China’s Huai River Basin (HRB) encountered an unprecedented basin-wide flood event characterized by anomalous southward displacement of the rain belt. This event established a new historical record with [...] Read more.

Catastrophic floods in monsoon-driven river systems pose significant challenges to flood resilience. In July 2020, China’s Huai River Basin (HRB) encountered an unprecedented basin-wide flood event characterized by anomalous southward displacement of the rain belt. This event established a new historical record with the three typical hydrological stations (Wangjiaba, Runheji, and Lutaizi sections) along the mainstem of the Huai River exceeded their guaranteed water levels within 11 h and synchronously reached peak flood levels within a 9-h window, whereas the inter-station lag times during the 2003 and 2007 floods ranged from 24 to 48 h, causing a critical emergency in the flood defense. By integrating operational hydrological data, meteorological reports, and empirical rainfall-runoff model schemes for the Meiyu periods of 2003, 2007, and 2020, this research systematically dissects the 2020 flood’s spatial composition patterns. Comparative analyses across spatiotemporal rainfall distribution, intensity metrics, and flood peak response dynamics reveal distinct characteristics of southward-shifted torrential rain and flood variability. The findings provide critical technical guidance for defending against extreme weather events and unprecedented hydrological disasters, directly supporting revisions to flood control planning in the Huai River Ecological and Economic Zone. Full article

(This article belongs to the Special Issue Using Hydrological Modeling for Spatio-Temporal Analysis of Rainfall Signatures)

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25 pages, 7020 KiB

Open AccessArticle

A Deep Learning Framework for Deformation Monitoring of Hydraulic Structures with Long-Sequence Hydrostatic and Thermal Time Series

by Hui Li, Jiankang Lou, Fan Li, Guang Yang and Yibo Ouyang

Water 2025, 17(12), 1814; https://doi.org/10.3390/w17121814 - 17 Jun 2025

Viewed by 336

Abstract

As hydraulic buildings are constantly subjected to complex interactions with water, particularly variations in hydrostatic pressure and temperature, deformation structural behavior is inherently sensitive to environmental fluctuations. Monitoring dam deformation with high accuracy and robustness is critical for ensuring the long-term safety and [...] Read more.

As hydraulic buildings are constantly subjected to complex interactions with water, particularly variations in hydrostatic pressure and temperature, deformation structural behavior is inherently sensitive to environmental fluctuations. Monitoring dam deformation with high accuracy and robustness is critical for ensuring the long-term safety and operational integrity of hydraulic structures. However, traditional physics-based models often struggle to fully capture the nonlinear and time-dependent deformation responses in hydraulic structures driven by such coupled environmental influences. To address these limitations, this study presents an advanced deep learning (DL)-based deformation monitoring for hydraulic buildings using long-sequence monitoring data of hydrostatic pressure and temperature. Specifically, the Bidirectional Stacked Long Short-Term Memory (Bi-Stacked-LSTM) is proposed to capture intricate temporal dependencies and directional dynamics within long-sequence hydrostatic and thermal time series. Then, hyperparameters, including the number of LSTM layers, neuron counts in each layer, dropout rate, and time steps, are efficiently fine-tuned using the Gaussian Process-based surrogate model optimization (GP-SMO) algorithm. Multiple deformation monitoring points from hydraulic buildings and a variety of advanced machine-learning methods are utilized for analysis. Experimental results indicate that the developed GP-SMO-optimized Bi-Stacked-LSTM dam deformation monitoring model shows better comprehensive representation capability of both past and future deformation-related sequences compared with benchmark methods. By approximating the behavior of the target function, the GP-SMO algorithms allow for the optimization of critical parameters in DL models while minimizing the high computational costs typically associated with direct evaluations. This novel DL-based approach significantly improves the extraction of deformation-relevant features from long-term monitoring data, enabling more accurate modeling of temporal dynamics. As a result, the developed method offers a promising new tool for safety monitoring and intelligent management of large-scale hydraulic structures. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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20 pages, 5062 KiB

Open AccessArticle

Groundwater Characteristics and Quality in the Coastal Zone of Lomé, Togo

by Koko Zébéto Houédakor, Djiwonou Koffi Adjalo, Benoît Danvide, Henri Sourou Totin Vodounon and Ernest Amoussou

Water 2025, 17(12), 1813; https://doi.org/10.3390/w17121813 - 17 Jun 2025

Viewed by 470

Abstract

The unprecedented development of coastal cities in West Africa is marked by anarchic urbanization accompanied by ineffective environmental management, leading to water pollution. This study is conducted in the southern districts of Lomé, Togo, an area built on sandbars where inappropriate attitudes, behaviors, [...] Read more.

The unprecedented development of coastal cities in West Africa is marked by anarchic urbanization accompanied by ineffective environmental management, leading to water pollution. This study is conducted in the southern districts of Lomé, Togo, an area built on sandbars where inappropriate attitudes, behaviors, and inadequate hygiene and sanitation practices prevail. The objective of this study is to characterize the quality of groundwater in the study area. Bacteriological and physicochemical analyses were carried out on 11 wells in 10 districts in the southern districts during the four seasons of the year. The analysis shows that the groundwater is polluted in all seasons. Nitrate concentrations exceed 50 mg/L in 65% of the samples, while chloride levels surpassed 250 mg/L in 18% of the cases. Regardless of the season, the dominant facies is sodium chloride and potassium chloride. In all districts, the analysis of microbiological parameters including total germs (30 °C, 100/mL), total coliforms (30 °C, 0/mL), Escherichia coli (44 °C, 2/250 mL), fecal streptococci (0/100 mL), and anaerobic sulfite reducers (44 °C, 2/20 mL) reveals values exceeding the European Union standards (2007). Groundwater contamination is facilitated by the sandy nature of the soil, which increases its vulnerability to various pollutants. Togo continues to experience cholera outbreaks, aggravated by poor sanitation infrastructure and limited vaccination coverage. Public health efforts are directed toward improving sanitation and raising awareness about waterborne and non-communicable diseases. Full article

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

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28 pages, 8465 KiB

Open AccessArticle

Analysis of Precipitation Variation Characteristics in Typical Chinese Regions Within the Indian Ocean and Pacific Monsoon Convergence Zone

by Junjie Wu, Liqun Zhong, Daichun Liu, Xuhua Tan, Hongzhen Pu, Bolin Chen, Chunyong Li and Hongbo Zhang

Water 2025, 17(12), 1812; https://doi.org/10.3390/w17121812 - 17 Jun 2025

Viewed by 386

Abstract

With climate warming, the global precipitation patterns have undergone significant changes, which will profoundly impact flood–drought disaster regimes and socioeconomic development in key regions of human activity worldwide. The convergence zone of the Indian Ocean monsoon and Pacific monsoon in China covers most [...] Read more.

With climate warming, the global precipitation patterns have undergone significant changes, which will profoundly impact flood–drought disaster regimes and socioeconomic development in key regions of human activity worldwide. The convergence zone of the Indian Ocean monsoon and Pacific monsoon in China covers most of the middle and lower reaches of the Yangtze River (MLRYR), which is located in the transitional area of the second and third steps of China’s terrain. Changes in precipitation patterns in this region will significantly impact flood and drought control in the MLRYR, as well as the socioeconomic development of the MLRYR Economic Belt. In this study, Huaihua area in China was selected as the study area to study the characteristics of regional precipitation change, and to analyze the evolution in the trends in annual precipitation, extreme precipitation events, and their spatiotemporal distribution, so as to provide a reference for the study of precipitation change patterns in the intersection zone. This study utilizes precipitation data from meteorological stations and the China Meteorological Forcing Dataset (CMFD) reanalysis data for the period 1979–2023 in Huaihua region. The spatiotemporal variation in precipitation in the study area was analyzed by using linear regression, the Mann–Kendall trend test, the moving average method, the Mann–Kendall–Sneyers test, wavelet analysis, and R/S analysis. The results demonstrate the following: (1) The annual precipitation in the study area is on the rise as a whole, the climate tendency rate is 9 mm/10 a, and the precipitation fluctuates greatly, showing an alternating change of “dry–wet–dry–wet”. (2) Wavelet analysis reveals that there are 28-year, 9-year, and 4-year main cycles in annual precipitation, and the precipitation patterns at different timescales are different. (3) The results of R/S analysis show that the future precipitation trend will continue to increase, with a strong long-term memory. (4) Extreme precipitation events generally show an upward trend, indicating that their intensity and frequency have increased. (5) Spatial distribution analysis shows that the precipitation in the study area is mainly concentrated in the northeast and south of Jingzhou and Tongdao, and the precipitation level in the west is lower. The comprehensive analysis shows that the annual precipitation in the study area is on the rise and has a certain periodic precipitation law. The spatial distribution is greatly affected by other factors and the distribution is uneven. Extreme precipitation events show an increasing trend, which may lead to increased flood risk in the region and downstream areas. In the future, it is necessary to strengthen countermeasures to reduce the impact of changes in precipitation patterns on local and downstream economic and social activities. Full article

(This article belongs to the Special Issue Remote Sensing of Spatial-Temporal Variation in Surface Water)

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21 pages, 47488 KiB

Open AccessArticle

Evaluation of X-Band Radar for Flash Flood Modeling in Guangrun River Basin

by Yan Xiong, Lingsheng Meng, Jiyang Tian and Yuefen Zhang

Water 2025, 17(12), 1811; https://doi.org/10.3390/w17121811 - 17 Jun 2025

Viewed by 395

Abstract

Flash flood disasters occur frequently under the influence of climate change and human activities, with the characteristics of strong suddenness, a wide range of hazards, and difficult prediction. Obtaining high-spatial- and high-temporal-resolution and high-precision rainfall monitoring and forecasting data is of great significance [...] Read more.

Flash flood disasters occur frequently under the influence of climate change and human activities, with the characteristics of strong suddenness, a wide range of hazards, and difficult prediction. Obtaining high-spatial- and high-temporal-resolution and high-precision rainfall monitoring and forecasting data is of great significance for accurate early warnings for flash flood disasters. In order to evaluate the advantages of X-band radar inverted rainfall in flash flood simulations, two typical flood events (3 July 2024 and 13 July 2024) in the Guangrun River Basin were studied. A comparative study between X-band radar inversion-based rainfall and rainfall measured at rainfall stations in terms of the flooding process and inundation extent was carried out using the China Flash Flood Hydrological Model (CNFF) and the two-dimensional hydrodynamic model (FASFLOOD). The results indicated that the temporal and spatial distribution characteristics of rainfall inversion by X-band radar were highly consistent with the measured rainfall at rainfall stations; in terms of simulating flood processes, rainfall based on X-band radar inversion performed better in key indicators such as the relative error of runoff depth, relative error of peak flow, error in time of peak occurrence, and Nash–Sutcliffe efficiency coefficient (NSE). In terms of simulating flood inundation, the simulation results based on X-band radar inversion and the measured rainfall from rainfall stations were consistent in the trend of rising and falling water processes and inundation range changes, and X-band radar could more accurately capture the spatial heterogeneity of rainfall. This study can provide technical support for disaster prevention and reductions in mountain floods in small watersheds. Full article

(This article belongs to the Section Hydrology)

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12 pages, 397 KiB

Open AccessArticle

Comparison Study of Urban Wastewater Treatment Using Conventional Biologic Treatment and Submerged Membrane Bioreactor Processes

by Halis Gazi Hiz and Hüdaverdi Arslan

Water 2025, 17(12), 1810; https://doi.org/10.3390/w17121810 - 17 Jun 2025

Viewed by 383

Abstract

Today, the demand for clean water resources causes the rapid consumption of water and the finding of alternative water resources. The recovery and reuse of wastewater after treatment is important for water sustainability, and in recent years, the use of wastewater by completely [...] Read more.

Today, the demand for clean water resources causes the rapid consumption of water and the finding of alternative water resources. The recovery and reuse of wastewater after treatment is important for water sustainability, and in recent years, the use of wastewater by completely or partially treating it has gained importance due to the water shortage that has emerged as a result of global climate change. It can be used in agricultural areas where water is frequently used, especially if the water content is suitable after treatment. In this study, the use of water from the treatment plant as irrigation water in agricultural areas was investigated. The effluent of the Mezitli and Kızkalesi Wastewater Treatment Plants in Mersin was used for this purpose. In the investigation of the usability of the treated water in agricultural irrigation, analyses were made for many pollutants. In order to examine the usability of wastewater after treatment in irrigation water, parameters such as total phosphorus (TP), total nitrogen (TN), biological oxygen demand (BOD) and heavy metals were examined in order to meet the nutrient needs of plants. The analysis results were evaluated according to the agricultural irrigation water criteria specified in the Wastewater Treatment Plant Technical Procedures Communiqué. As a result, the analysis results of the treated water were compared with the limit values in the regulations, and it was evaluated that the treated water in the Mezitli Wastewater Treatment Plant did not meet the limit values of irrigation water usage criteria. However, it has been evaluated that the effluent from the Kızkalesi Wastewater Treatment Plant, which was treated with the MBR process, meets the limit values and therefore can be used for agricultural irrigation purposes. As a result, when the analysis results performed on treated water were compared with the Wastewater Treatment Plant Technical Procedures Communiqué irrigation water limit values, it was evaluated that the treated water of the Mezitli Wastewater Treatment Plant did not meet irrigation water limit values, but the treated water of the Kızkalesi Wastewater Treatment Plant with the MBR process met the irrigation water limit values and therefore could be used for agricultural irrigation purposes. The study results showed that the treated water in the Mezitli Wastewater Treatment Plant could not be used for agricultural irrigation, but the treated water in the Kızkalesi Wastewater Treatment Plant could be used for agricultural irrigation. Full article

(This article belongs to the Topic Wastewater Treatment by Physical, Chemical, Photochemical, and Biological Processes, and Their Combinations)

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17 pages, 4075 KiB

Open AccessArticle

Design and Properties of Titanium Dioxide/Graphene Oxide Composites Exploitable in Wastewater Treatments

by Simona Ortelli, Lara Faccani, Enrico Ercolani, Ilaria Zanoni, Chiara Artusi, Magda Blosi, Stefania Albonetti and Anna Luisa Costa

Water 2025, 17(12), 1809; https://doi.org/10.3390/w17121809 - 17 Jun 2025

Viewed by 456

Abstract

Water is one of the necessities for human survival, and clean water is essential for life. As a result, there is an increasing focus on efficient wastewater treatment methods, including advanced oxidation processes using innovative heterogeneous photocatalysts. In this context, TiO₂–graphene [...] Read more.

Water is one of the necessities for human survival, and clean water is essential for life. As a result, there is an increasing focus on efficient wastewater treatment methods, including advanced oxidation processes using innovative heterogeneous photocatalysts. In this context, TiO₂–graphene oxide (TGO) composites offer a multifaceted approach to wastewater treatment, combining the photocatalytic properties of TiO₂ with the adsorption capabilities and potential synergistic effects of graphene oxide. In this research, we intimately mixed commercial TiO₂ powder with graphene oxide at different concentrations (9, 16, and 25 wt.%) by exploiting sonochemical activation. The morphological and physicochemical analyses confirmed the interfacial interactions and the successful formation of the composite. The TGO composites exhibited increased reactivity compared to both GO and TiO₂ phases, during the photodegradation process of Rhodamine B (RhB), serving as a reaction model. Therefore, the photocatalytic results demonstrated the synergistic effect that occurs when a TiO₂-based photocatalyst is combined with sonochemically activated GO. The Cu²⁺ adsorption tests, simulating the removal of heavy metals from contaminated water, revealed that TGO composites displayed intermediate capabilities compared to the pure phases’ higher (GO) and lower (TiO₂) adsorption capacity. The functional characterizations revealed that the optimal design is represented by the sample containing 16 wt.% of GO. Overall, this study confirms that TGO composites are effective as photocatalysts and adsorbents for removing both organic and inorganic pollutants, making them strong candidates for wastewater treatment. Full article

(This article belongs to the Special Issue Recent Advances in Photocatalysis in Water and Wastewater Treatment)

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18 pages, 2405 KiB

Open AccessArticle

Influence of Aquatic Vegetation on Velocity Distribution, Water Surface Profile, and Energy Loss: An Experimental Study in an Open Channel

by Mohamed Galal Elbagoury, Roland Weiss, Eva Panulinova, Gamal M. Abdel-Aal and Marwa F. Shaheen

Water 2025, 17(12), 1808; https://doi.org/10.3390/w17121808 - 17 Jun 2025

Viewed by 369

Abstract

Aquatic vegetation can influence hydraulic performance in channels, rivers, and floodplains. Most previous studies used cylindrical stems to simulate vegetation, while few studies used shrub-like or sedge structures that exhibited a maximum width near the top of the vegetation. In contrast, this research [...] Read more.

Aquatic vegetation can influence hydraulic performance in channels, rivers, and floodplains. Most previous studies used cylindrical stems to simulate vegetation, while few studies used shrub-like or sedge structures that exhibited a maximum width near the top of the vegetation. In contrast, this research focuses on shrub-like structures that show a maximum width near the bottom of the vegetation. To understand the effects of aquatic vegetation on velocity distribution, water surface profile, and energy loss, experiments have been conducted in an open channel with a rectangular cross-section. The results indicated that the streamwise velocity within the lower layer remains nearly constant with depth where z/y is less than 0.20. However, once z/y exceeds 0.20, the streamwise velocity increases rapidly as the depth increases toward the water surface. Additionally, the shape of the vegetation influences the position of the inflection point. Moreover, the water level rises upstream of the vegetated area, decreases within it, and gradually returns to the normal depth downstream. The bed slope has little effect on relative energy loss, with maximum values reaching 6.61%, while the presence of vegetation leads to a significant increase, reaching up to 22.51%. The relative energy loss increases with a higher submerged ratio. A new empirical equation is proposed to estimate the relative energy loss in vegetated channels. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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