Water

22 pages, 1157 KB

Open AccessArticle

The Risk Assessment for Water Conveyance Channels in the Yangtze-to-Huaihe Water Diversion Project (Henan Reach)

by Huan Jing, Yanjun Wang, Yongqiang Wang, Jijun Xu and Mingzhi Yang

Water 2025, 17(20), 2992; https://doi.org/10.3390/w17202992 (registering DOI) - 16 Oct 2025

Water conveyance channels, as critical components of water diversion projects, feature numerous structures, complex configurations, and intensive operational management requirements, making them vulnerable to multiple risks, such as extreme flooding, channel blockage, structural failures, and management deficiencies. To ensure an accurate assessment of [...] Read more.

Water conveyance channels, as critical components of water diversion projects, feature numerous structures, complex configurations, and intensive operational management requirements, making them vulnerable to multiple risks, such as extreme flooding, channel blockage, structural failures, and management deficiencies. To ensure an accurate assessment of the operational safety risk, this study proposes a comprehensive risk assessment framework that integrates risk probability and risk loss. The former is quantified using the Consequence Reverse Diffusion Method (CRDM), which systematically identifies and categorizes key factors of primary dike failure modes into four domains: hydrological characteristics, channel morphology, engineering structures, and operational management. The latter is assessed by integrating socioeconomic impacts, including population exposure, infrastructure investment, and industrial and agricultural production. A structured assessment framework is established through systematic indicator selection, justified weight assignment, and standardized scoring criteria. Application of the framework to Yangtze-to-Huaihe Water Diversion Project (Henan Reach) reveals that the risk probability across four segments falls within the (1, 3) range, indicating a generally low to moderate risk profile, while channel morphology shows greater spatial variability than hydrological, structural, and management indicators, driven by local differences in crossing structure density, sinuosity, and regime coefficients. Meanwhile, the segments along the Qingshui River face higher risk losses owing to their upstream location and large-scale water supply capacity, resulting in a relatively higher comprehensive risk level. Full article

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

20 pages, 5795 KB

Open AccessArticle

Freeze–Thaw-Driven Dynamics of Soil Water–Salt and Nitrogen: Effects and Implications for Irrigation Management in the Hetao Irrigation District

by Weili Ge, Jiaqi Jiang, Chunli Su, Xianjun Xie, Qing Zhang, Chunming Zhang, Yanlong Li, Xin Li, Jiajia Song and Yinchun Su

Water 2025, 17(20), 2991; https://doi.org/10.3390/w17202991 (registering DOI) - 16 Oct 2025

Abstract

This study investigated the mechanisms of soil water–salt and nitrogen transport and optimal strategies under freeze–thaw (F-T) cycles in the salinized farmlands of the Hetao Irrigation District. A combined approach of field monitoring and laboratory simulation, utilizing both undisturbed and repacked soil columns [...] Read more.

This study investigated the mechanisms of soil water–salt and nitrogen transport and optimal strategies under freeze–thaw (F-T) cycles in the salinized farmlands of the Hetao Irrigation District. A combined approach of field monitoring and laboratory simulation, utilizing both undisturbed and repacked soil columns subjected to 0–15 F-T cycles and five irrigation treatments, was employed to analyze the spatiotemporal dynamics in Gleyic Solonchaks. The results demonstrated that freeze–thaw processes play an important role in salt migration in surface soil layers, driving salt redistribution through phase changes of soil moisture. Increased freeze–thaw cycles reduced surface soil moisture content while promoting upward salt accumulation, salt dynamics exhibited pronounced spatial heterogeneity and irrigation source dependency, and the surface layer exhibited lower salinity levels after irrigation compared to pre-irrigation levels. These cycles also enhanced short-term soil nitrogen transformation and facilitated inorganic nitrogen accumulation. Different irrigation regimes exhibited a significant impact on the dynamics of water–salt and nitrogen in soil, with low-salinity treatment (S2) and moderate-nitrogen irrigation (N2) effectively reducing surface salt accumulation while improving nitrogen utilization efficiency (moderate-nitrogen irrigation exhibited higher mineralization rates, which facilitated the release of inorganic nitrogen from soil). This study reveals the synergistic transport mechanisms of water–salt and nitrogen under freeze–thaw driving forces and provides a scientific basis and practical pathway for sustainable agricultural management in cold arid irrigation districts. Full article

(This article belongs to the Section Soil and Water)

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30 pages, 1604 KB

Open AccessArticle

Bottle Test Free Chlorine Bulk Decay Coefficient Statistical Fitting for Water Supply Systems Via State Estimation Techniques

by Elena Cejas, Sarai Díaz and Javier González

Water 2025, 17(20), 2990; https://doi.org/10.3390/w17202990 (registering DOI) - 16 Oct 2025

Abstract

Free chlorine residual is the most widely adopted disinfectant residual in water supply systems. Chlorine is usually applied at treatment works, but it decays as water flows and spends time within the network. Chlorine decay is the result of a bulk and a [...] Read more.

Free chlorine residual is the most widely adopted disinfectant residual in water supply systems. Chlorine is usually applied at treatment works, but it decays as water flows and spends time within the network. Chlorine decay is the result of a bulk and a wall decay component. Bulk decay may be considered invariable through the pipe network (it only depends on water composition) and is often characterized at the entrance to the system through bottle tests, which measure chlorine evolution over time in a laboratory environment to then adjust a model (dependent on one or more coefficients) that represents its behavior. Previous studies have acknowledged that the bulk decay coefficient varies widely and that free chlorine measurements are subject to measurement errors, but they have not quantified the impact of these errors on the bulk decay coefficient. The aim of this paper is to provide a methodology that statistically fits chlorine’s bulk decay coefficient based on bottle test results, with appropriate management of uncertainty effects. The proposal is to use state estimation techniques, which combine free chlorine measurements and system knowledge (in this case, a first-order bulk decay model) to provide the most likely chlorine behavior and its associated uncertainty. This approach goes one step beyond previous studies, which report only a single value of the bulk decay coefficient without accounting for randomness, and thus fail to assess true variability, leading to unrepresentative comparisons. Results for water samples from different sources demonstrate the importance of controlling the fitting process through state estimation to understand and compare the bulk decay coefficient. Full article

(This article belongs to the Section Urban Water Management)

23 pages, 4998 KB

Open AccessArticle

Hybrid Reconstruction of Sea Level at Dokdo in the East Sea Using Machine Learning and Geospatial Interpolation (1993–2023)

by MyeongHee Han and Hak Soo Lim

Water 2025, 17(20), 2989; https://doi.org/10.3390/w17202989 (registering DOI) - 16 Oct 2025

Abstract

Sea level variability in the East Sea (Sea of Japan) and the Northwest Pacific poses challenges for coastal risk management due to the scarcity of long-term observations at remote locations such as Dokdo (Dok Island). This study reconstructs a continuous monthly sea level [...] Read more.

Sea level variability in the East Sea (Sea of Japan) and the Northwest Pacific poses challenges for coastal risk management due to the scarcity of long-term observations at remote locations such as Dokdo (Dok Island). This study reconstructs a continuous monthly sea level record at Dokdo from 1993 to 2023 by imputing gaps in 13 nearby Permanent Service for Mean Sea Level tide gauge stations using eight machine learning models and geospatial interpolation methods. The ensemble mean of Machine Learning-based imputations produced physically realistic and temporally coherent timeseries, preserving both seasonal and interannual variability. Sea level at Dokdo, estimated via inverse distance weighting, aligned well with satellite altimetry from Copernicus Marine Service and exhibited strong regional coherence with nearby stations. These results demonstrate that a hybrid framework combining statistical imputation, Machine Learning, and inverse barometric correction can effectively reconstruct sea level in data-sparse marine regions. The methodology provides a scalable tool for monitoring long-term trends and validating satellite and model products in marginal seas like the East Sea. Full article

(This article belongs to the Special Issue Advanced Remote Sensing for Coastal System Monitoring and Management)

22 pages, 727 KB

Open AccessArticle

Copper (II) Complex Decorated PVDF Membranes for Enhanced Removal of Organic Pollutants from Textile and Oily Wastewater

by Felipe P. da Silva, Aline C. F. Pereira, Juliana C. Pinheiro, Annelise Casellato, Cristiano P. Borges and Fabiana V. da Fonseca

Water 2025, 17(20), 2988; https://doi.org/10.3390/w17202988 (registering DOI) - 16 Oct 2025

Abstract

This study reports the development of polyvinylidene fluoride (PVDF) membranes decorated with a copper(II) complex (CuL) for the removal of organic pollutants from wastewater. Using Drimaren Red X-6BN (DRX-6BN) as a probe, the PVDF membrane with the lowest CuL loading (PVDF/PDA/CuL-4) reached an [...] Read more.

This study reports the development of polyvinylidene fluoride (PVDF) membranes decorated with a copper(II) complex (CuL) for the removal of organic pollutants from wastewater. Using Drimaren Red X-6BN (DRX-6BN) as a probe, the PVDF membrane with the lowest CuL loading (PVDF/PDA/CuL-4) reached an adsorption capacity of 19.78 mg/g at 300 min, with removal of up to 50% DRX-6BN. Kinetic analysis favored Elovich (R² > 0.9928; RMSE < 0.4489) and the pseudo-second-order model (R² > 0.9540; RMSE < 1.1388), consistent with chemisorption. Intraparticle diffusion occurred in two steps. In the presence of 20 mg/L of hydrogen peroxide (H₂O₂), the removal was >80% within 180 min at higher CuL loadings (PVDF/PDA/CuL-40). In oily wastewater, PVDF/PDA/CuL-4 achieved ~100% COD removal in 120 min with H₂O₂, whereas pristine PVDF achieved 38.5%. Storage stability tests demonstrated the preservation of catalytic and separation performance for at least three months. All tests were conducted at pH ≈ 6.0 and a temperature of 25 °C. In contrast to many catalytic membranes, these membranes operate at near-neutral pH and ambient temperature in the absence of radiation. The results highlight PVDF membranes decorated with CuL as a robust and sustainable approach for the treatment of oily effluents, particularly by combining Fenton-like processes under mild conditions. Full article

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

17 pages, 1916 KB

Open AccessArticle

Comparative Performance of Green Roof Systems with Smart Cisterns: Balancing Stormwater Capture and Irrigation Supply

by Nandan H. Shetty, Mark Wang, Robert M. Elliott and Patricia J. Culligan

Water 2025, 17(20), 2987; https://doi.org/10.3390/w17202987 (registering DOI) - 16 Oct 2025

Abstract

Using five years of field monitoring data, this study compares two types of roof systems that combine green roofs, cisterns, and real-time control (RTC) strategies: one optimized to reduce stormwater runoff (a fully vegetated roof with cisterns operating under a “smart detention” [SD] [...] Read more.

Using five years of field monitoring data, this study compares two types of roof systems that combine green roofs, cisterns, and real-time control (RTC) strategies: one optimized to reduce stormwater runoff (a fully vegetated roof with cisterns operating under a “smart detention” [SD] logic that fully empties within 24 h), and one designed to balance architectural, economic, and structural tradeoffs (a half vegetated, half bare roof with cisterns operating under a “rainwater harvesting” [RWH] logic that partially drains in anticipation of rainfall while maintaining a reserve for green roof irrigation). Both configurations demonstrated strong stormwater performance, with cisterns improving roof retention by 10.2 to 13.0% over five years. For small to medium storms (under 25 mm), representing 71.2% of events, both strategies prevented more than 95% of runoff, while forecast accuracy primarily influenced larger events. Even with modest cistern sizing, the SD system captured 96.7% and the RWH system 95.8% of runoff from small to medium storms, approaching 100% assuming perfect weather forecasts. Irrigation analysis showed that RWH cisterns supplied ~51% of irrigation demand, increasing to ~70% under perfect forecasts. This study is among the first to compare stormwater and irrigation outcomes from side-by-side RTC-managed roof systems over multiple years. The results underscore that the mixed green/bare roof with RWH logic provides nearly equivalent stormwater benefits while offering added value through irrigation supply, reduced structural loading, and design flexibility. Full article

(This article belongs to the Special Issue Stormwater Management in Sponge Cities)

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21 pages, 12126 KB

Open AccessArticle

Optimization of Synergistic Water Resources, Water Environment, and Water Ecology Remediation and Restoration Project: Application in the Jinshan Lake Basin

by Wenyang Jiang, Xin Liu, Yue Wang, Yue Zhang, Xinxin Chen, Yuxing Sun, Jun Chen and Wanshun Zhang

Water 2025, 17(20), 2986; https://doi.org/10.3390/w17202986 (registering DOI) - 16 Oct 2025

Abstract

The concept of synergistic water resources, water environment, water ecology remediation, and restoration (3WRR) is essential for addressing the interlinked challenges of water scarcity, pollution, and ecological degradation. An intelligent platform of remediation and restoration project optimization was developed, integrating multi-source data fusion, [...] Read more.

The concept of synergistic water resources, water environment, water ecology remediation, and restoration (3WRR) is essential for addressing the interlinked challenges of water scarcity, pollution, and ecological degradation. An intelligent platform of remediation and restoration project optimization was developed, integrating multi-source data fusion, a coupled air–land–water model, and dynamic decision optimization to support 3WRR in river basins. Applied to the Jinshan Lake Basin (JLB) in China’s Greater Bay Area, the platform assessed 894 scenarios encompassing diverse remediation and restoration plans, including point/non-point source reduction, sediment dredging, recycled water reuse, ecological water replenishment, and sluice gate control, accounting for inter-annual meteorological variability. The results reveal that source control alone (95% reduction in point and non-point loads) leads to limited improvement, achieving less than 2% compliance with Class IV water quality standards in tributaries. Integrated engineering–ecological interventions, combining sediment dredging with high-flow replenishment from the Xizhijiang River (26.1 m³/s), increases compliance days of Class IV water quality standards by 10–51 days. Concerning the lake plans, including sluice regulation and large-volume water exchange, the lake area met the Class IV standard for COD, NH₃-N, and TP by over 90%. The platform’s multi-objective optimization framework highlights that coordinated, multi-scale interventions substantially outperform isolated strategies in both effectiveness and sustainability. These findings provide a replicable and data-driven paradigm for 3WRR implementation in complex river–lake systems. The platform’s application and promotion in other watersheds worldwide will serve to enable the low-cost and high-efficiency management of watershed water environments. Full article

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

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34 pages, 97018 KB

Open AccessArticle

Identifying Fresh Groundwater Potential in Unconfined Aquifers in Arid Central Asia: A Remote Sensing and Geo-Information Modeling Approach

by Evgeny Sotnikov, Zhuldyzbek Onglassynov, Kanat Kanafin, Ronny Berndtsson, Valentina Rakhimova, Oxana Miroshnichenko, Shynar Gabdulina and Kamshat Tussupova

Water 2025, 17(20), 2985; https://doi.org/10.3390/w17202985 (registering DOI) - 16 Oct 2025

Abstract

Arid regions in Central Asia face persistent and increasing water scarcity, with groundwater serving as the primary source for drinking water, irrigation, and industry. The effective exploration and management of groundwater resources are critical, but are constrained by limited monitoring infrastructure and complex [...] Read more.

Arid regions in Central Asia face persistent and increasing water scarcity, with groundwater serving as the primary source for drinking water, irrigation, and industry. The effective exploration and management of groundwater resources are critical, but are constrained by limited monitoring infrastructure and complex hydrogeological settings. This study investigates the Akbakay aquifer, a representative area within Central Asia with challenging hydrogeological conditions, to delineate potential zones for fresh groundwater exploration. A multi-criteria decision analysis was conducted by integrating the Analytical Hierarchy Process (AHP) with Geographic Information Systems (GIS), supported by remote sensing datasets. To address the subjectivity of weight assignment, the AHP results were further validated using Monte Carlo simulations and fuzzy logic aggregation (Fuzzy Gamma). The integrated approach revealed stable high-suitability groundwater zones that consistently stand out across deterministic, probabilistic, and fuzzy assessments, thereby improving the reliability of the groundwater potential mapping. The findings demonstrate the applicability of combined AHP–GIS methods enhanced with uncertainty analysis for sustainable groundwater resource management in data-scarce arid regions of Central Asia. Full article

(This article belongs to the Special Issue Regional Geomorphological Characteristics and Sedimentary Processes)

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23 pages, 6751 KB

Open AccessArticle

Health Risk Assessment of Groundwater in Cold Regions Based on Kernel Density Estimation–Trapezoidal Fuzzy Number–Monte Carlo Simulation Model: A Case Study of the Black Soil Region in Central Songnen Plain

by Jiani Li, Yu Wang, Jianmin Bian, Xiaoqing Sun and Xingrui Feng

Water 2025, 17(20), 2984; https://doi.org/10.3390/w17202984 (registering DOI) - 16 Oct 2025

Abstract

The quality of groundwater, a crucial freshwater resource in cold regions, directly affects human health. This study used groundwater quality monitoring data collected in the central Songnen Plain in 2014 and 2022 as a case study. The improved DRASTICL model was used to [...] Read more.

The quality of groundwater, a crucial freshwater resource in cold regions, directly affects human health. This study used groundwater quality monitoring data collected in the central Songnen Plain in 2014 and 2022 as a case study. The improved DRASTICL model was used to assess the vulnerability index, while water quality indicators were selected using a random forest algorithm and combined with the entropy-weighted groundwater quality index (E-GQI) approach to realize water quality assessment. Furthermore, self-organizing maps (SOM) were used for pollutant source analysis. Finally, the study identified the synergistic migration mechanism of NH₄⁺ and Cl⁻, as well as the activation trend of As in reducing environments. The uncertainty inherent to health risk assessment was considered by developing a kernel density estimation–trapezoidal fuzzy number–Monte Carlo simulation (KDE-TFN-MCSS) model that reduced the distribution mis-specification risks and high-risk misjudgment rates associated with conventional assessment methods. The results indicated that: (1) The water chemistry type in the study area was predominantly HCO₃⁻–Ca²⁺ with moderately to weakly alkaline water, and the primary and nitrogen pollution indicators were elevated, with the average NH₄⁺ concentration significantly increasing from 0.06 mg/L in 2014 to 1.26 mg/L in 2022, exceeding the Class III limit of 1.0 mg/L. (2) The groundwater quality in the central Songnen Plain was poor in 2014, comprising predominantly Classes IV and V; by 2022, it comprised mostly Classes I–IV following a banded distribution, but declined in some central and northern areas. (3) The results of the SOM analysis revealed that the principal hardness component shifted from Ca²⁺ in 2014 to Ca²⁺–Mg²⁺ synergy in 2022. Local high values of As and NH₄⁺ were determined to reflect geogenic origin and diffuse agricultural pollution, whereas the Cl⁻ distribution reflected the influence of de-icing agents and urbanization. (4) Through drinking water exposure, a deterministic evaluation conducted using the conventional four-step method indicated that the non-carcinogenic risk (HI) in the central and eastern areas significantly exceeded the threshold (HI > 1) in 2014, with the high-HI area expanding westward to the central and western regions in 2022; local areas in the north also exhibited carcinogenic risk (CR) values exceeding the threshold (CR > 0.0001). The results of a probabilistic evaluation conducted using the proposed simulation model indicated that, except for children’s CR in 2022, both HI and CR exceeded acceptable thresholds with 95% probability. Therefore, the proposed assessment method can provide a basis for improved groundwater pollution zoning and control decisions in cold regions. Full article

(This article belongs to the Special Issue Soil and Groundwater Quality and Resources Assessment, 2nd Edition)

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20 pages, 3504 KB

Open AccessArticle

Modeling the Evolution of Mechanical Behavior in Rocks Under Various Water Environments

by Lixiang Liu, Sai Fu, Xianlin Jia, Xibin Li and Linfei Zhang

Water 2025, 17(20), 2983; https://doi.org/10.3390/w17202983 - 16 Oct 2025

Abstract

After reservoir impoundment, water infiltration weakens rock strength and accelerates creep deformation. Existing models seldom capture both strength degradation and creep behavior under prolonged saturation. This study develops a coupled hydro-mechanical creep model that integrates saturation-dependent elastic modulus reduction, cohesion decay with pore [...] Read more.

After reservoir impoundment, water infiltration weakens rock strength and accelerates creep deformation. Existing models seldom capture both strength degradation and creep behavior under prolonged saturation. This study develops a coupled hydro-mechanical creep model that integrates saturation-dependent elastic modulus reduction, cohesion decay with pore pressure, and a nonlinear creep law modified by a Heaviside function. Simulation of rock deformation during water infiltration reveals that water–creep coupling increases steady-state deformation by over 50% compared to strength degradation alone. A case study of a high arch dam reservoir slope demonstrates that models incorporating both water-weakening and creep effects predict significantly larger deformations than those ignoring these mechanisms. The model provides a practical tool for predicting long-term deformation in reservoir slopes under water–rock interaction. Full article

(This article belongs to the Special Issue Reservoir Control Operation and Water Resources Management, 2nd Edition)

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12 pages, 3265 KB

Open AccessArticle

Per- and Polyfluoroalkyl Substances (PFAS) in Urban Stormwater Runoff: Insights from a Roadside Rain Garden

by Hadeer Saleh, Dibyendu Sarkar, Zhiming Zhang, Michel Boufadel and Rupali Datta

Water 2025, 17(20), 2982; https://doi.org/10.3390/w17202982 - 16 Oct 2025

Abstract

Urban stormwater runoff is increasingly recognized as a critical but underexplored pathway for per- and polyfluoroalkyl substances (PFAS) to enter aquatic environments. This work investigated the occurrence and behavior of 40 PFAS compounds in stormwater runoff entering a roadside rain garden in Secaucus, [...] Read more.

Urban stormwater runoff is increasingly recognized as a critical but underexplored pathway for per- and polyfluoroalkyl substances (PFAS) to enter aquatic environments. This work investigated the occurrence and behavior of 40 PFAS compounds in stormwater runoff entering a roadside rain garden in Secaucus, New Jersey, during six storm events between August 2023 and July 2024. Total PFAS concentrations (Σ40 PFAS) ranged from 1437 to 1615 ng/L, with perfluorobutane sulfonate (PFBS, 239–303 ng/L) and perfluorohexanoic acid (PFHxA, 115–137 ng/L) consistently emerging as dominant species. Perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) together accounted for over 70% of the total PFAS mass. Despite its intended role in water quality improvement, the rain garden showed no measurable change in PFAS concentrations (differences of only 0.03–1.10%). These findings highlight the persistence and mobility of PFAS in urban stormwater runoff and the limited efficacy of conventional green infrastructure in mitigating PFAS contamination. Furthermore, they underscore the ineffectiveness of conventional green infrastructure for PFAS mitigation and the urgent need for advanced treatment technologies integrated into urban water management frameworks. Full article

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

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25 pages, 7515 KB

Open AccessReview

Research Status and Emerging Trends in the Comprehensive Impact of Inter-Basin Water Transfer Projects (IBWTs)

by Tao Han, Laihong Jing, Dengming Yan, Yisi Lu and Xinying Fan

Water 2025, 17(20), 2981; https://doi.org/10.3390/w17202981 - 16 Oct 2025

Abstract

Research on the impact and response strategies of inter-basin water transfer projects (IBWTs) on regional hydrology, water resources, the ecological environment, the economy, and society holds significant strategic importance for the protection of the environment and long-term economic and social development throughout the [...] Read more.

Research on the impact and response strategies of inter-basin water transfer projects (IBWTs) on regional hydrology, water resources, the ecological environment, the economy, and society holds significant strategic importance for the protection of the environment and long-term economic and social development throughout the entire lifecycle of IBWTs. In this study, the current state and trends in research on the comprehensive impact of IBWTs were explored using CiteSpace and HistCite, two analytical tools, to perform a bibliometric analysis on 498 studies (2002–2024) in the Web of Science Core Collection (WoSCC). The following aspects are addressed in depth: (1) The characteristics of publications on the comprehensive impact of IBWTs. (2) Critical information on the countries, institutions, and subjects engaged in research about the comprehensive impact of IBWTs. (3) The trends and hotspots of research on the comprehensive impact of IBWTs. In this study, we review and evaluate the results of research on the comprehensive impact of large-scale IBWTs, efficiently providing scholars an understanding of the existing research and new frontiers in this field. In addition, for domestic and foreign scholars who are about to delve into the assessment of IBWTs’ impacts and related research, this article can provide valuable information on hot topics and next steps in research from a global perspective. Full article

(This article belongs to the Section Hydrology)

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23 pages, 5923 KB

Open AccessArticle

Mechanistic Study of Methyl Orange Removal by Fe₃O₄@MIL-53(Fe Cu) Composite Material

by Xiuzhen Yang, Xiaochen Yue, Tianjiao He and Changye Wang

Water 2025, 17(20), 2980; https://doi.org/10.3390/w17202980 - 16 Oct 2025

Abstract

A novel magnetic composite, Fe₃O₄@MIL-53(Fe Cu), was successfully synthesized and applied for the efficient removal of methyl orange (MO) from aqueous solutions. The ad sorption performance was systematically evaluated under various conditions, including adsorbent dosage, solution pH, coexisting anions, [...] Read more.

A novel magnetic composite, Fe₃O₄@MIL-53(Fe Cu), was successfully synthesized and applied for the efficient removal of methyl orange (MO) from aqueous solutions. The ad sorption performance was systematically evaluated under various conditions, including adsorbent dosage, solution pH, coexisting anions, and regeneration cycles. The results demonstrated that an optimal dosage of 20 mg achieved a removal efficiency exceeding 85%, with maximum adsorption observed at pH 3. The presence of common anions (Cl⁻, SO₄²⁻, CO₃²⁻, and PO₄³⁻) showed negligible effects on MO removal. Kinetic studies revealed that the adsorption process followed the pseudo-second-order model. Although minor chemisorption contributions were observed, the Dubinin–Radushkevich (D–R) model confirmed the predominance of physical adsorption. The Freundlich isotherm provided the best fit to the equilibrium data, indicating a maximum adsorption capacity of 193.65 mg/g and suggesting multilayer adsorption on a heterogeneous surface. Thermodynamic analysis confirmed the spontaneous and endothermic nature of the adsorption process. The primary mechanisms governing MO adsorption were identified as electrostatic attraction, π–π interactions, and hydrogen bonding. The composite exhibited excellent reusability over multiple cycles, demonstrating its potential for practical wastewater treatment applications. Full article

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

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18 pages, 3473 KB

Open AccessArticle

The Dynamic Reallocation Value: Revisiting the Framework of Computing the Stabilization Value of Groundwater in a Dynamic Context

by Zeyu Zhang and Masahiro Sato

Water 2025, 17(20), 2979; https://doi.org/10.3390/w17202979 - 15 Oct 2025

Abstract

This paper revisits the theoretical framework of computing the stabilization value of groundwater in a dynamic context. Specifically, we argue that what the existing studies have measured as the augmentation value contains a different type of value, the dynamic reallocation value (DRV), which [...] Read more.

This paper revisits the theoretical framework of computing the stabilization value of groundwater in a dynamic context. Specifically, we argue that what the existing studies have measured as the augmentation value contains a different type of value, the dynamic reallocation value (DRV), which should be evaluated as an important part of the dynamic stabilization value. We examine the existence of DRV and its underlying behavioural mechanism using a simple two-stage model and then generalise the specification to a dynamic model with an arbitrary number of stages. We find that behind the positive values of DRV, users amplify their reactions against surface water fluctuations and still realize a higher total expected benefit than in the case without uncertainty. Ignoring the existence of DRV may impair the value of groundwater as an essential instrument for climate adaptation. Full article

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

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49 pages, 27043 KB

Open AccessArticle

Comparison of Pluvial Flooding Modeling Software Applied in Highly Urbanized Settlements Using the Case of Lake Ganzirri

by José Javier Serrano Chano, Giuseppina Brigandi and Giuseppe Tito Aronica

Water 2025, 17(20), 2978; https://doi.org/10.3390/w17202978 - 15 Oct 2025

Abstract

The rising urbanization and climate change have increased pluvial flood risks, especially in highly urbanized areas. This study focuses on the Lake Ganzirri area in Messina, Italy, where street-level floods have raised concerns for infrastructure resilience and public safety. This study aims to [...] Read more.

The rising urbanization and climate change have increased pluvial flood risks, especially in highly urbanized areas. This study focuses on the Lake Ganzirri area in Messina, Italy, where street-level floods have raised concerns for infrastructure resilience and public safety. This study aims to explore how to effectively represent key urban features, emphasizing buildings and low-impact development/sustainable urban drainage systems (LID/SUDS). For the buildings, a combination of referred approaches to represent buildings is compared against the widely used method to represent buildings as voids in a 2D mesh, ignoring them in the water balance calculations. For the LID/SUDS control elements, a 2D representation is presented and compared against the widely used 1D approach to model such elements. The study uses three well-known software packages—EPA-SWMM 5.2, HEC-RAS 6.2, and InfoWorks ICM 2021.9—applied to the Lake Ganzirri area, to explore the representation of buildings using the building void method (available in InfoWorks ICM 2021.9) against the proposed method (in HEC-RAS 6.2) to replicate runoff flow over a 2D model of a highly urbanized area. From scenario S0, three more scenarios were derived: S1 (S0 with pluvial drainage network), S2 (S1 with LID/SUDS control elements), and S3 (S0 with 2D representation of LID/SUDS), which were then compared against using four comparison schemes. Results show that the proposed method for representing buildings computed the propagation of the runoff comparable to when the building void method is used, with some shortcomings regarding mesh adjustments and computational times. Regarding the 2D representation of LID/SUDS, the effects were unperceivable on water depth maps (reduction in water depths of 1.5 mm on average for all the rainfall events). Still, they were reflected in the increase of 62% of the infiltration volume on average of all the rainfall scenarios and a decrease of 9.1% of water flowing outside the 2D area, therefore replicating the effect of capturing water. Full article

(This article belongs to the Special Issue Advances in Flood Hazard and Risk Analysis: Theory, Methods, Numerical Models, Strategies, and Applications)

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21 pages, 8633 KB

Open AccessArticle

Experimental Study on the Fracture and Failure of the Locking Section of Rock Slopes Caused by Freeze–Thaw of Fracture Water

by Shuai Liu, Hui Liu, Xiangqi Tian, Kuanyao Zhao, Yonglong Qu, Zhigang Jia and Huaiwu Su

Water 2025, 17(20), 2977; https://doi.org/10.3390/w17202977 - 15 Oct 2025

Abstract

In rock slopes with a three-section landslide, the locking section is the key control factor. This study conducted double-sided freeze–thaw tests on a scale model of a rock slope with a three-section landslide in a cold region. We monitored the changes in frost [...] Read more.

In rock slopes with a three-section landslide, the locking section is the key control factor. This study conducted double-sided freeze–thaw tests on a scale model of a rock slope with a three-section landslide in a cold region. We monitored the changes in frost heave force, strain, and fracture during the water–ice phase change and investigated the effect of the trailing edge tensile crack length on the frost heave fracture of the locking section. A crack frost heave model was proposed based on rock and fracture mechanics to explore the mechanism of slope crack freeze–thaw weathering. According to the results, the slope shoulder froze first, with the freezing front progressing from the slope shoulder to the interior of the rock mass. The fracture failure in the three-section rock slopes was mostly caused by the frost heave of the trailing-edge tensile cracks. The largest frost heave force and locking section deformation occurred when the temperature of the top of the trailing edge tensile crack decreased from −3.5 °C to −6 °C (whereas that of the bottom of the crack dropped from 0 °C to −2.6 °C). Additionally, the results demonstrate that the frost heave force is positively correlated with the length of the trailing edge tension crack, and shear marks are virtually absent on the tensile fracture surface. Full article

(This article belongs to the Special Issue Advances in Water Related Geotechnical Engineering)

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20 pages, 5603 KB

Open AccessArticle

Research on the Influence Mechanism of Regulating Capacity and Flow Recession Process in the Karst Vadose Zone

by Ruitong Liu, Jinguo Wang, Shumei Zhu, Yuting Zhang, Shiyu Zheng, Yongsheng Zhao, Fei Qiao and Dong Yang

Water 2025, 17(20), 2976; https://doi.org/10.3390/w17202976 - 15 Oct 2025

Abstract

Understanding the groundwater movement patterns and regulating functions of the karst vadose zone is essential in addressing water scarcity and protecting the ecological environment in the karst area of southwest China. A laboratory-scale experimental model of a typical karst vadose zone was constructed [...] Read more.

Understanding the groundwater movement patterns and regulating functions of the karst vadose zone is essential in addressing water scarcity and protecting the ecological environment in the karst area of southwest China. A laboratory-scale experimental model of a typical karst vadose zone was constructed and used to simulate the water flow process under the influence of four factors: transfer zone thickness, surface slope, karstification degree, and rainfall intensity. A corresponding distributed model was subsequently developed to simulate the laboratory experiments. The discharge recession process, the regulating capacity, and the division of fast and slow flow were quantitatively analyzed by the recession coefficient, the regulating coefficient, and the percentage of fast flow and that of sinkhole flow. As the transfer zone thickness increases from 40 cm to 120 cm, the vadose zone regulating coefficient rises from 0.49 to 0.53, while fast flow decreases from 87.7% to 78.1%, indicating that the enhanced regulating capacity is mainly governed by the slow flow system. The evident difference in growth rates between the percentage of fast flow (an increase of 9.1%) and that of sinkhole flow (an increase of 48.7%) indicates that the decrease in regulating capacity resulting from an increase in surface slope is primarily due to enhanced water loss through sinkholes. When the structure of the karst vadose zone remains constant, the regulating coefficient decreases exponentially with increasing rainfall intensity and gradually approaches a constant value, which represents the maximum regulating capacity of the karst vadose zone under its current structural conditions. Full article

(This article belongs to the Special Issue Hydrogeological and Hydrochemical Investigations of Aquifer Systems)

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23 pages, 2237 KB

Open AccessArticle

Heavy Metal Contamination and Bioaccumulation Patterns from a Ramsar Wetland Tributary, Northern Algeria: A Baseline Assessment

by Selma Salhi, Mohammed Khalil Mellal, Abdelmadjid Chelli and Rassim Khelifa

Water 2025, 17(20), 2975; https://doi.org/10.3390/w17202975 - 15 Oct 2025

Abstract

Freshwater ecosystems face increasing contamination by heavy metals, yet their transfer patterns remain poorly understood. This study aimed to assess the extent of pollution by ten potential toxic elements (As, Ni, Zn, Pb, Cd, Cr, Fe, Cu, Mn and Se) in water, sediment, [...] Read more.

Freshwater ecosystems face increasing contamination by heavy metals, yet their transfer patterns remain poorly understood. This study aimed to assess the extent of pollution by ten potential toxic elements (As, Ni, Zn, Pb, Cd, Cr, Fe, Cu, Mn and Se) in water, sediment, Spirogyra sp., and two endemic fish species (Tropidophoxinellus callensis and Luciobarbus callensis) in the El Mellah River. The element concentrations were measured in four matrices using inductively coupled plasma optical emission spectrometry. Bioaccumulation Factor and Trophic Transfer Factor were used to depict bioaccumulation patterns across the ecological strata and two levels of the food web. The results showed that all sediment samples demonstrated very high ecological risk, consistently exceeding critical thresholds (PLI > 1, RI > 600). Contamination factor and geoaccumulation index revealed moderate to extreme contamination by As and Cd throughout all samples. Both fish species exhibited a bio-accumulation affinity for Cr, Cd, Mn, and Zn from water, while concurrently accumulating As from Spirogyra sp. Muscle tissue concentrations of As, Pb, Cr, and Cd in both species exceeded international guideline values. Health risk assessment indicated that children face elevated exposure risks, with Cd intake exceeding safe limits and total hazard quotient surpassing safety thresholds by 2.6-fold, while carcinogenic risks from Cd and Cr exceeded acceptable levels for both adults and children. These findings provide baseline contamination data for this tributary system and highlight elevated risks to both human health (through fish consumption) and ecosystem integrity, indicating the need for targeted monitoring and risk management measures. Full article

(This article belongs to the Special Issue Water Treatment Technology for Emerging Contaminants, 2nd Edition)

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25 pages, 12040 KB

Open AccessArticle

Water and Salt Transport and Balance in Saline Soils Under Different Land Use Types in the Seasonally Frozen Zone of Songnen Plain

by Caidie Chen, Yu Wang, Jianmin Bian, Xiaoqing Sun and Yanchen Wang

Water 2025, 17(20), 2974; https://doi.org/10.3390/w17202974 - 15 Oct 2025

Abstract

To investigate differences in water and salt transport during irrigation, freezing, and thawing periods in typical saline-affected paddy fields and saline-affected upland fields, field-based automated in situ monitoring was conducted in both types of saline-affected farmland (May 2023 to May 2024). Correlation analysis [...] Read more.

To investigate differences in water and salt transport during irrigation, freezing, and thawing periods in typical saline-affected paddy fields and saline-affected upland fields, field-based automated in situ monitoring was conducted in both types of saline-affected farmland (May 2023 to May 2024). Correlation analysis identified seasonal drivers of water–salt migration, while the HYDRUS-3D model simulated transport and equilibrium processes. The HYDRUS-3D model, equipped with a freeze–thaw module, accurately simulated complex water–salt transport in cold arid regions. Key findings include: (1) During freeze–thaw periods, soil moisture content and electrical conductivity (Ec) increased with the retreating frost front in both upland and paddy soils. During the irrigation period, maximum soil moisture content and Ec values occurred at 80 cm depth in dryland soils and 60 cm depth in paddy soils, primarily influenced by irrigation and capillary rise. (2) Groundwater salt ions significantly affected soil salinization in both farmland types. During the freeze–thaw period, Ec positively correlated with soil temperature. During the irrigation period, Ec positively correlated with evapotranspiration and negatively correlated with precipitation. (3) Salt changes during the irrigation, freezing, and thawing periods were −565.4, 326.85, and 376.55 kg/ha for upland fields, respectively; corresponding changes for paddy fields were −1217.0, 280.07, and 299.35 kg/ha. (4) Both land types exhibited reduced salinity during the irrigation period, with paddy fields showing a reduction 3.36 times greater than dryland fields. During the freezing and thawing periods, both land types experienced salinity accumulation, with dryland fields accumulating higher salinity levels than paddy fields. These results indicate that paddy field irrigation and drainage systems help mitigate salinization, while dryland fields are more prone to springtime salt accumulation. These findings provide a basis for developing targeted management strategies for saline–alkali soils. Full article

(This article belongs to the Section Soil and Water)

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