Water

17 pages, 2142 KB

Open AccessReview

The Impact of Climate Change on Nitrogen Migration and Transformation in Inland Water Bodies: A Bibliometric Landscape Analysis

by Danhua Wang, Cancan Jiang, Xu Wang, Huijuan Feng and Hongjie Gao

Water 2026, 18(5), 646; https://doi.org/10.3390/w18050646 - 9 Mar 2026

Abstract

Based on a bibliometric analysis of 2680 publications (1962–2024), this study elucidates the knowledge structure and intellectual evolution of research on climate change-driven nitrogen migration and transformation in inland waters, a critical issue for water security and global climate stability. The field has [...] Read more.

Based on a bibliometric analysis of 2680 publications (1962–2024), this study elucidates the knowledge structure and intellectual evolution of research on climate change-driven nitrogen migration and transformation in inland waters, a critical issue for water security and global climate stability. The field has experienced accelerated growth since 2016, led by the United States and China. Analysis reveals a research framework centered on climate change, nitrogen, and water quality, interconnected with processes like eutrophication and denitrification. The intellectual focus has evolved from early investigations into fundamental chemical mechanisms towards a contemporary emphasis on human–climate interactions (e.g., land use), model-based predictions, and regional management solutions for nonpoint source pollution. A key finding is the bidirectional climate–nitrogen feedback, where climate alters nitrogen pathways and transformations, which in turn release greenhouse gases. The findings underscore a pivotal shift from theoretical understanding to applied, solution-oriented research. Future work must prioritize integrated multi-technique approaches, cross-ecosystem comparisons, and data-driven modeling to advance predictive capabilities and support effective nitrogen management in inland waters under a changing climate. Full article

(This article belongs to the Special Issue ANAMMOX Based Technology for Nitrogen Removal from Wastewater: Linking Microbial Interactions, Ecological Mechanisms, and Engineering Optimization, 2nd Edition)

► Show Figures

Figure 1

18 pages, 4504 KB

Open AccessArticle

Nonlinear Large-Strain Consolidation of Vertical Drains with Coupled Radial–Vertical Flow Considering Hansbo’s Flow and Smearing Effects

by Guanglei Chen, Haiyang Xie, Yihu Ma, Yizhao Li, Zan Xu, Linlu Song, Penglu Cui and Kejie Zhai

Water 2026, 18(5), 645; https://doi.org/10.3390/w18050645 - 9 Mar 2026

Abstract

While early ideal consolidation theories for vertical drains focused primarily on radial flow, numerous coupled radial–vertical seepage models have since been developed to better capture complex flow behavior in practice. To overcome this limitation, a nonlinear large-strain consolidation model for vertical drains with [...] Read more.

While early ideal consolidation theories for vertical drains focused primarily on radial flow, numerous coupled radial–vertical seepage models have since been developed to better capture complex flow behavior in practice. To overcome this limitation, a nonlinear large-strain consolidation model for vertical drains with coupled radial-vertical flow is proposed, explicitly incorporating Hansbo’s non-Darcy flow, smear effects, and soil nonlinearity. The finite difference method is then employed to obtain numerical solutions, and the reliability of the proposed numerical scheme is verified by degenerating the model to the radial consolidation case and comparing the results with the corresponding analytical solution. The results indicate that consolidation develops fastest when the permeability coefficient within the smear zone follows a parabolic distribution. Increasing the Hansbo’s flow parameter m and threshold hydraulic gradient parameter I₁ markedly slows down the consolidation process, while the contribution of vertical flow is primarily confined to the early stage. In addition, larger soil nonlinearity parameters I_c and α amplify the influence of radial–vertical coupled flow. Parametric analysis further shows that when the ratio of soil layer thickness to the radius of the influence zone (H/r_e) exceeds 10, the effect of vertical flow becomes negligible, and the consolidation behavior can be reasonably approximated using a radial-flow-only model. Full article

(This article belongs to the Section Hydrogeology)

► Show Figures

Figure 1

19 pages, 2832 KB

Open AccessArticle

Multidimensional Analysis of Water Scarcity Risk and Its Transmission Network Across Chinese Provinces

by Changfeng Shi, Xiaoyan Li, Kehan Zhang and Ran Zhang

Water 2026, 18(5), 644; https://doi.org/10.3390/w18050644 - 8 Mar 2026

Abstract

Water scarcity is increasingly shaped by interactions between environmental constraints and interconnected economic systems, evolving from a localized supply–demand issue into a systemic risk embedded in economic networks. This study develops an integrated framework that conceptualizes water scarcity as a multidimensional risk by [...] Read more.

Water scarcity is increasingly shaped by interactions between environmental constraints and interconnected economic systems, evolving from a localized supply–demand issue into a systemic risk embedded in economic networks. This study develops an integrated framework that conceptualizes water scarcity as a multidimensional risk by jointly accounting for water quantity, water quality, and environmental flow requirements, and embeds it within a multiregional input–output (MRIO) model to examine its formation and transmission across China. Results show that multidimensional constraints substantially amplify water scarcity risk and reshape its spatial distribution, extending risk beyond traditionally water-stressed regions to major agricultural provinces and key ecological function zones. Water-intensive, pollution-intensive, and basic industries form the core of risk accumulation, while virtual water linkages drive cross-regional risk propagation, with developed coastal provinces acting as major receivers. Network analysis identifies a small number of provinces—particularly Henan and Jiangsu—as critical hubs for risk transmission and systemic amplification. These findings highlight the need for integrated, multidimensional, and network-oriented water governance to enhance water system resilience. Full article

7 pages, 186 KB

Open AccessEditorial

Ecohydrology in the Context of Climate Change: Strategies for Management, Monitoring, and Modeling

by Carmen Maftei and Ashok Vaseashta

Water 2026, 18(5), 643; https://doi.org/10.3390/w18050643 - 8 Mar 2026

Abstract

Global anthropogenic activities and conjoint climate extremes are fundamentally disrupting closely coupled hydroecological systems, altering catchment-scale water balances, biogeochemical fluxes, and the resilience of ecosystem services [...] Full article

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

20 pages, 4585 KB

Open AccessArticle

Metal Accumulation and Plant Performance in Controlled Bioretention Mesocosms

by Qianting Chen, Boming Wang, Guohong Zhang, Mengge Wang and Yongwei Gong

Water 2026, 18(5), 642; https://doi.org/10.3390/w18050642 - 8 Mar 2026

Abstract

Bioretention systems are increasingly implemented as green infrastructure for urban stormwater management. However, their long-term performance is jeopardized by the continuous accumulation of potentially toxic metals in substrates and vegetation, posing significant risks to ecosystem health and human safety. Despite their growing application, [...] Read more.

Bioretention systems are increasingly implemented as green infrastructure for urban stormwater management. However, their long-term performance is jeopardized by the continuous accumulation of potentially toxic metals in substrates and vegetation, posing significant risks to ecosystem health and human safety. Despite their growing application, the mechanisms driving metal dynamics and plant responses within these systems remain poorly understood. This study conducts a comprehensive multi-factor investigation into the accumulation, mobility, and biological impacts of four representative potentially toxic metals (Cd, Cu, Zn, and Pb) in bioretention soils and vegetation. Through controlled mesocosm experiments, we quantified metal concentrations in soils and three plant species, analyzed alterations in the physical and chemical properties of soil, and assessed plant physiological stress responses. Metal concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS), and statistical analyses were conducted using one-way ANOVA (p < 0.05). Cadmium exhibited the highest enrichment, with plant uptake increasing by 330.0% to 563.2%, especially in Iris tectorum Maxim., which demonstrated superior phytoaccumulation potential. Conversely, Ophiopogon japonicus Ker Gawl. showed remarkable tolerance to metal-induced stress, maintaining stable levels of chlorophyll content, photosynthetic rate, peroxidase activity, and soluble sugar concentration. Notably, the incorporation of humic substances significantly enhanced metal immobilization in soil, while simultaneously reducing plant uptake and physiological stress, revealing a promising strategy for toxicity mitigation. By integrating the effects of plant species, substrate composition, and influent concentration, this study provides novel insights into the complex interactions governing pollutant fate in bioretention systems. The findings offer critical guidance for optimizing bioretention design and management to ensure sustained pollutant removal efficiency and ecological resilience in urban stormwater treatment. Full article

(This article belongs to the Special Issue Urban Drainage Systems and Stormwater Management, 2nd Edition)

► Show Figures

Figure 1

12 pages, 684 KB

Open AccessArticle

Optimality-Based Active Region Model (ARM) for Fingering Flow in the Vadose Zone: Recent Theoretical Progress

by Hui-Hai Liu, Yingjun Liu and Shuo Zhang

Water 2026, 18(5), 641; https://doi.org/10.3390/w18050641 - 8 Mar 2026

Abstract

Gravitational fingering often occurs for water flow in the vadose zone and accurate modeling of this important flow process remains a significant scientific challenge. This paper presents the latest theoretical developments of the optimality-based active region model (ARM), a macroscopic framework developed for [...] Read more.

Gravitational fingering often occurs for water flow in the vadose zone and accurate modeling of this important flow process remains a significant scientific challenge. This paper presents the latest theoretical developments of the optimality-based active region model (ARM), a macroscopic framework developed for describing gravitational fingering flow in the vadose zone. ARM divides the soil into active (fingering) and inactive regions, introducing a relationship between water flux and hydraulic gradient derived from the principle of optimality that the system self-organizes to maximize water flow conductivity. Unlike traditional models, ARM’s hydraulic conductivity depends on both capillary pressure or water saturation and water flux, reflecting the unstable nature of fingering flow. The paper provides an updated mathematical derivation of ARM relationships using calculus of variations and extends ARM to account for small water flux in the non-fingering zone, resulting in a dual-flow field model. These new developments should make ARM more rigorous and realistic for field-scale applications. Full article

(This article belongs to the Special Issue Modelling, Monitoring and Assessment of Soil Hydrology and Ecological Processes)

► Show Figures

Figure 1

22 pages, 2173 KB

Open AccessReview

The Problem of Water Losses in the Visegrad Group (V4) Countries: Challenges and Opportunities

by Mateusz Rożnowski, Jakub Żywiec, Dawid Szpak and Barbara Tchórzewska-Cieślak

Water 2026, 18(5), 640; https://doi.org/10.3390/w18050640 - 8 Mar 2026

Abstract

One of the objectives of Directive (EU) 2020/2184 is to assess the amount of water leakage in water supply systems (WSS) and to reduce it if it exceeds a certain threshold. The Directive is binding on water supply companies supplying at least 10,000 [...] Read more.

One of the objectives of Directive (EU) 2020/2184 is to assess the amount of water leakage in water supply systems (WSS) and to reduce it if it exceeds a certain threshold. The Directive is binding on water supply companies supplying at least 10,000 m³/d or serving at least 50,000 consumers. The problem of water losses due to, among other things, aging infrastructure currently requires appropriate action to be taken by WSS management companies. This paper discusses the problem of water losses in the Visegrad Group countries and the challenges and opportunities associated with it. In order to analyze the problem, a bibliometric analysis of the state of knowledge was performed. The results of the literature review present the current directions of research on this topic in the V4 countries as former communist bloc countries. The strengths and weaknesses identified in the paper can be used to plan water loss reduction by water supply companies, researchers, and legislators. Full article

(This article belongs to the Special Issue Water Resources Allocation, Planning, and Regulation for Sustainable Management)

► Show Figures

Figure 1

25 pages, 5483 KB

Open AccessArticle

Urban Expansion and Flood-Relevant Runoff Responses in Data-Limited Catchments

by Tropikë Agaj, Ewelina Janicka-Kubiak, Anna Budka and Valbon Bytyqi

Water 2026, 18(5), 639; https://doi.org/10.3390/w18050639 - 8 Mar 2026

Abstract

Rapid land-cover transformations associated with urban expansion have increasingly altered hydrological processes, modifying runoff generation and flood response at the catchment scale. This study applied the Hydrologic Engineering Center–Hydrologic Modeling System (HEC-HMS) to examine rainfall–runoff dynamics in the Prosna River catchment (Poland) and [...] Read more.

Rapid land-cover transformations associated with urban expansion have increasingly altered hydrological processes, modifying runoff generation and flood response at the catchment scale. This study applied the Hydrologic Engineering Center–Hydrologic Modeling System (HEC-HMS) to examine rainfall–runoff dynamics in the Prosna River catchment (Poland) and the Morava e Binçës River catchment (Kosovo) for 2006–2021. Land-use changes were quantified using CORINE Land Cover (CLC) data from 2006, 2012, and 2018, and their hydrological effects were evaluated through changes in the Curve Number (CN) parameter. The model was calibrated and validated for the Prosna catchment, achieving satisfactory performance (NSE = 0.72 during calibration and 0.56 during validation), confirming its reliability under varying hydrometeorological conditions. Due to the lack of continuous discharge data in Kosovo, a parameter-transfer approach was used, applying calibrated parameters from the Prosna to the Morava e Binçës. Scenario-based simulations assessed the combined effects of urban growth and meteorological variability. Under wetter conditions, increased precipitation and expanded impervious surfaces markedly amplified simulated discharge, with maximum daily differences reaching 86.9 m³ s⁻¹. These findings underscore the sensitivity of catchment response to interacting land-use and precipitation changes and highlight the need for improved hydrological monitoring in data-scarce regions. Full article

(This article belongs to the Special Issue Advances in Watershed Hydrology: Integrating Process Understanding and Predictive Modeling)

► Show Figures

Figure 1

20 pages, 2737 KB

Open AccessArticle

Hydro–Meteorological Coupled Runoff Forecasting Using Multi-Model Precipitation Forecasts

by Zhanyun Zhu, Yue Zhou, Xinhua Zhao, Yan Cheng, Qian Li and Weiwei Zhang

Water 2026, 18(5), 638; https://doi.org/10.3390/w18050638 - 7 Mar 2026

Abstract

Accurate runoff forecasting is essential for effective water resource management, hydropower operation, and flood risk mitigation. In this study, daily inflow runoff in the Xin’an River Basin, eastern China, was simulated using four ensemble learning models: Gradient Boosting Decision Tree (GBDT), XGBoost, CatBoost, [...] Read more.

Accurate runoff forecasting is essential for effective water resource management, hydropower operation, and flood risk mitigation. In this study, daily inflow runoff in the Xin’an River Basin, eastern China, was simulated using four ensemble learning models: Gradient Boosting Decision Tree (GBDT), XGBoost, CatBoost, and Stacking. Among them, the CatBoost model achieved the best performance, with a correlation coefficient (CC) exceeding 0.97, Nash–Sutcliffe efficiency (NSE) above 0.95, and reduced RMSE and MAE compared with the currently operational hydrological model. To extend the forecast lead times, two hydro–meteorological coupled models were developed by integrating the CatBoost model with a single numerical weather prediction model (EC) and a dynamically weighted multi-model ensemble precipitation forecast system (OCF). The coupled models were evaluated for lead times up to 240 h. The forecast skill value was highest within 96 h, with CC values above 0.80 and NSE around 0.50. The OCF-coupled model demonstrated improved reliability for lead times of 48–96 h, whereas the EC-driven forecasts performed better within the first 48 h. Case studies during the 2021–2022 flood seasons confirmed that the coupled framework accurately reproduced flood evolution and peak discharge dynamics, demonstrating its practical value for medium-range runoff forecasting in humid river basins. Full article

(This article belongs to the Special Issue "Watershed–Urban" Flooding and Waterlogging Disasters)

► Show Figures

Figure 1

33 pages, 5228 KB

Open AccessReview

Ecological Profile of Three River Basins of the North of Portugal—A Review

by Regina Torre, Sara C. Antunes, José Catita and Olga M. Lage

Water 2026, 18(5), 637; https://doi.org/10.3390/w18050637 - 7 Mar 2026

Abstract

Rivers are dynamic systems that flow from higher elevations to lowlands, eventually discharging into lakes, seas, or oceans, and play a key role in sustaining ecosystems and supporting human activities. River basin characterisation extends beyond the watercourse itself, encompassing land uses, tributaries and [...] Read more.

Rivers are dynamic systems that flow from higher elevations to lowlands, eventually discharging into lakes, seas, or oceans, and play a key role in sustaining ecosystems and supporting human activities. River basin characterisation extends beyond the watercourse itself, encompassing land uses, tributaries and hydromorphological features that influence ecological processes. This review analyses three river basins in northern Portugal, Ave, Douro, and Vouga, using a holistic characterisation approach. These basins represent contrasting river systems in terms of size, hydrological regulation and dominant land uses, while simultaneously being subject to pressures frequently reported in many other river basins in Europe, and around the world. The analysis includes a general basin description, a hydromorphological assessment with emphasis on land use, and an evaluation of water ecological status, with particular focus on estuarine ecosystems. Water quality in the three basins has been strongly influenced by anthropogenic pressures, including industrial and agricultural activities, and wastewater discharges. Although the implementation of the European Water Framework Directive has led to improvements in recent decades, the degree of recovery varies among basins. Persistent challenges, such as nutrient concentrations, microbial contamination, and heavy metal pollution, highlight the need for integrated river basin management and improved monitoring strategies. This review provides transferable insights for the management of river basins facing similar environmental pressures. Full article

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

► Show Figures

Figure 1

30 pages, 3388 KB

Open AccessArticle

Nonstationary Flood Frequency Analysis for Urban Watersheds Using Open-Source Bayesian Software: Contrasting Case Studies from Texas

by C. Haden Smith, Brian Skahill and David A. Margo

Water 2026, 18(5), 636; https://doi.org/10.3390/w18050636 - 7 Mar 2026

Abstract

Urban flood frequency analysis faces unique challenges as land development alters watershed hydrology, producing nonstationary flood records. This study demonstrates nonstationary flood frequency analysis (NSFFA) using RMC-BestFit, an open-source Bayesian software, through two Texas case studies. Brays Bayou at Houston (96 years of [...] Read more.

Urban flood frequency analysis faces unique challenges as land development alters watershed hydrology, producing nonstationary flood records. This study demonstrates nonstationary flood frequency analysis (NSFFA) using RMC-BestFit, an open-source Bayesian software, through two Texas case studies. Brays Bayou at Houston (96 years of record) exemplifies an urbanized watershed with increasing flood trends; a step-logistic model captures both the abrupt increase in mean flood magnitude around 1968 and the progressive decrease in log-space variance as urbanization homogenized runoff response. O.C. Fisher Reservoir (169 years of record) exhibits decreasing trends attributed to brush encroachment and groundwater extraction; despite a sinusoidal model achieving best information criteria, a step function was selected based on physical reasoning, demonstrating that statistical fit alone should not dictate model selection. Results reveal contrasting frequency curve patterns: at O.C. Fisher, stationary and nonstationary curves differ uniformly (53% reduction in 100-year flood), while at Brays Bayou, curves differ substantially for frequent events (48% increase in 2-year flood) but converge in the extreme tail due to opposing trends in location and scale parameters. These findings underscore that NSFFA relevance depends on decision context. Bayesian methods offer key advantages including flexible integration of diverse data sources, comprehensive uncertainty quantification, and principled model comparison. Open-source software democratizes access to these methods, promoting transparency and reproducibility. Full article

(This article belongs to the Special Issue Urban Flood Frequency Analysis and Risk Assessment, 2nd Edition)

► Show Figures

Figure 1

21 pages, 6167 KB

Open AccessArticle

Subseasonal Ensemble Prediction of the 2024 Abrupt Drought-to-Flood Transition in Henan Province, China

by Yifei Wang, Xing Yuan and Shiyu Zhou

Water 2026, 18(5), 635; https://doi.org/10.3390/w18050635 - 7 Mar 2026

Abstract

In 2024, an abrupt drought-to-flood transition (ADFT) event occurred in Henan Province, China, causing severe losses to agriculture and the economy. Predicting the spatiotemporal evolution of such compound extremes remains challenging at the subseasonal scale. This study employs soil moisture percentiles to identify [...] Read more.

In 2024, an abrupt drought-to-flood transition (ADFT) event occurred in Henan Province, China, causing severe losses to agriculture and the economy. Predicting the spatiotemporal evolution of such compound extremes remains challenging at the subseasonal scale. This study employs soil moisture percentiles to identify local droughts and floods, connects them into coherent patches, and detects an ADFT event spatiotemporally. The proposed three-dimensional identification method is further applied to evaluate the ECMWF S2S reforecasts of the 2024 ADFT event. At a 1-week lead, the ECMWF ensemble mean successfully captures the transition. However, the spatial extent is underpredicted substantially at a 2-week lead. In terms of probabilistic forecast, the Brier skill scores for drought, transition, and flood stages are 0.38, 0.57, and 0.38 at a 1-week lead, respectively. However, these scores drop sharply at a 2-week lead, particularly for the transition and flood stages. The decreased forecast skill is jointly influenced by internal dynamical errors in the model and biases in the positions of the subtropical high- and low-pressure systems at long lead. This study assesses the capability of a numerical model to predict a compound extreme from both deterministic and probabilistic perspectives, and highlights the critical role of atmospheric circulation in achieving skillful prediction. Full article

(This article belongs to the Section Water and Climate Change)

► Show Figures

Figure 1

20 pages, 3858 KB

Open AccessArticle

Vulnerability Assessment of Levee Failure Due to Underseepage in the Szigetköz Floodplain Area

by Edina Koch and Richard Ray

Water 2026, 18(5), 634; https://doi.org/10.3390/w18050634 - 7 Mar 2026

Abstract

Analysis of the likelihood of structural or hydraulic failures of levees is a crucial part of flood risk assessment and is affected by many uncertainties. This paper evaluates a critical area along the Danube River in the Szigetköz floodplain, where hydraulic risk has [...] Read more.

Analysis of the likelihood of structural or hydraulic failures of levees is a crucial part of flood risk assessment and is affected by many uncertainties. This paper evaluates a critical area along the Danube River in the Szigetköz floodplain, where hydraulic risk has been increasing due to rising flood levels. Blanket theory approaches demonstrated the probability of failure relative to erosional failure, and Monte Carlo simulations generated fragility curves. The results of the case study show that the thickness of the aquifer layer has a slight effect if it is deeper than 30 m. The research also reveals that the probability of failure is highly affected by the distance from the river to the riverside levee toe; the shorter this distance, the higher the hydraulic risk. Sensitivity analyses emphasize the effect of variable inhomogeneity; as the leakage factor increases, the probability of failure due to underseepage increases. Comparing coefficients of variation across different floodwater levels showed that at low floodwater levels, a lower coefficient of variation corresponds to a lower probability of failure. In contrast, at higher floodwater levels, the same coefficient produced a higher probability of failure. Full article

(This article belongs to the Section Soil and Water)

► Show Figures

Figure 1

22 pages, 1197 KB

Open AccessArticle

Thermodynamic and Microbubble-Dynamics Framework for Dissolved-Air Flotation Pretreatment of Arsenic-Rich Groundwater

by Zorana Radibratović, Biljana Cakić, Mirjana Kijevčanin, Ivona Radović, David Mitrinović and Marija Perović

Water 2026, 18(5), 633; https://doi.org/10.3390/w18050633 - 7 Mar 2026

Abstract

Dissolved-air flotation (DAF) is widely used for surface-water pretreatment but remains insufficiently explored for chemically complex groundwater. This study develops a thermodynamic and bubble-dynamics modeling framework to evaluate the feasibility of DAF pretreatment for groundwater containing elevated arsenic, natural organic matter (NOM), and [...] Read more.

Dissolved-air flotation (DAF) is widely used for surface-water pretreatment but remains insufficiently explored for chemically complex groundwater. This study develops a thermodynamic and bubble-dynamics modeling framework to evaluate the feasibility of DAF pretreatment for groundwater containing elevated arsenic, natural organic matter (NOM), and color. The study is theoretical and model-based; no experimental dissolved-air flotation tests were performed. Air solubility was calculated at pressures of 4–6 bar and temperatures of 13–17 °C, while microbubble size, rise velocity, and bubble–floc interaction efficiencies were estimated using established physical models. Laboratory coagulation–flocculation jar tests with FeCl₃ and FeCl₃/PAC were used to define realistic floc properties prior to flotation modeling. No experimental dissolved-air flotation tests were conducted; all flotation-related results presented in this study are derived from thermodynamic and hydrodynamic modeling. Results show that a temperature decrease from 17 to 13 °C increases effective gas supersaturation by ~15% and shifts predicted microbubble diameters from ~60–90 µm to ~35–60 µm under identical operating conditions. The qualitative consistency between modeled flotation-relevant parameters and previously observed coagulation–flocculation trends for color, total organic carbon, and arsenic removal supports the proposed mechanistic framework. The study demonstrates how coupling coagulation chemistry with thermodynamically optimized air dissolution can enhance DAF applicability for arsenic- and NOM-rich groundwater. Full article

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

► Show Figures

Figure 1

23 pages, 3380 KB

Open AccessArticle

Innovative Fabrication of Highly Efficient Cu₂ZnSnS₄-TiO₂/TiO₂ Nanotube Array Heterostructure for Efficient Organic Degradation in Basic Dye Wastewater: Experimental and RSM Approaches

by Amal Abdulrahman, Zaina Algarni, Nejib Ghazouani, Saad Sh. Sammen, Abdelfattah Amari and Miklas Scholz

Water 2026, 18(5), 632; https://doi.org/10.3390/w18050632 - 7 Mar 2026

Abstract

Titanium dioxide (TiO₂) nanotube arrays (NTAs) were constructed on Ti foil to immobilize Cu₂ZnSnS₄-TiO₂ (CZTS-T/NTAs) via the sol–gel dip-coating technique. The films were characterized by X-ray diffraction (XRD) patterns, field-emission scanning electron microscope–energy dispersive spectroscopy (FESEM-EDX), [...] Read more.

Titanium dioxide (TiO₂) nanotube arrays (NTAs) were constructed on Ti foil to immobilize Cu₂ZnSnS₄-TiO₂ (CZTS-T/NTAs) via the sol–gel dip-coating technique. The films were characterized by X-ray diffraction (XRD) patterns, field-emission scanning electron microscope–energy dispersive spectroscopy (FESEM-EDX), ultraviolet–visible diffuse reflectance spectra (UV–Vis/DRS), and electrochemical impedance spectroscopy (EIS) techniques. The photocatalytic property of CZTS-T/NTAs was evaluated by the photodegradation of Basic Blue 41 under visible light irradiation. We show that CZTS-T/NTAs have an energy band gap of 2.23 eV, which leads to excellent potential trapping or facilitates the transition of charge carriers under visible light. The parameters R₀ and C₀ of the experimental EIS data, by fitting the proposed electrical circuit, were also discussed. Decreasing R₀ led to an increase in cell capacitance, which resulted in increased carrier generation at the interface between the catalyst and solution and thus an increased photodegradation yield. The response surface methodology (RSM) and central composite rotatable design (CCRD) were used to optimize the effects of the experimental parameters in the degradation process by four key variables (pH, dye concentration, irradiation time, and hydrogen peroxide (H₂O₂) concentration). As a result, the optimized conditions attained a considerable degradation of 95.25%. We also proposed the possible photodegradation mechanism of the photocatalyst. Notably, the proposed catalyst after six consecutive reuse runs retained activity. Full article

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

► Show Figures

Figure 1

19 pages, 2800 KB

Open AccessArticle

Effects of Bioleaching Pretreatment on Humus Fractions and Electron Transfer Capacity During Aerobic Composting of Dewatered Sludge

by Jin Zhou, Min Huang, Mei Wang, Xiaozhe Hu, Tieguang He, Chengcheng Zeng, Mingxin Bin, Huiting Zeng and Hua Zhang

Water 2026, 18(5), 631; https://doi.org/10.3390/w18050631 - 6 Mar 2026

Abstract

Compost-derived humic acids (HAs) and fulvic acids (FAs) play an essential role in enhancing soil microbial diversity and activity by facilitating metabolic processes through electron transfer. Herein, the effect of bioleaching dewatered sludge (BDS) in comparison with filter press dewatered sludge (FDS) on [...] Read more.

Compost-derived humic acids (HAs) and fulvic acids (FAs) play an essential role in enhancing soil microbial diversity and activity by facilitating metabolic processes through electron transfer. Herein, the effect of bioleaching dewatered sludge (BDS) in comparison with filter press dewatered sludge (FDS) on the electron transfer capacity (ETC) of humic substances during composting was investigated as a novel attempt. A variety of characterization methods including UV-Vis, FTIR, 3D-EEM, and electrochemical measurements, were used to explore the change in humic substances during composting. The results indicated that bioleaching treatment significantly influenced the organic matter composition and hindered the accumulation of redox-active functional groups during composting. Notably, the ETC of HA increased by 24.07% in the FDS group but declined by 40.62% in the BDS group. This divergence stemmed from the organic matter loss during bioleaching, leading to reduced quinone-like and tryptophan-like substances associated with electron transfer in HA during composting. Furthermore, BDS showed lower pH, water content, and organic matter, but higher concentrations of ammonium nitrogen (

{NH}_{4}^{+} - N

) and ammonia nitrogen

{NH}_{3}^{-} - N

, all of which potentially influenced humification efficiency. These findings not only clarify the electron-transfer dynamics of humic fractions but also highlight the importance of optimizing sludge pretreatment for improved composting performance and resource recovery. Full article

(This article belongs to the Special Issue Emerging Technologies for Nutrient Recovery and Wastewater Treatment)

► Show Figures

Figure 1

23 pages, 7128 KB

Open AccessArticle

Differentiated Evolution of Two Mid-Channel Bars in the Middle Yangtze River’s Urban Reach: Coupled Drivers and Terrestrial Habitat Assessment

by Dong Li, Xuefeng Wang, Xiya Wang, Changbo Liu and Zhiwei Li

Water 2026, 18(5), 630; https://doi.org/10.3390/w18050630 - 6 Mar 2026

Abstract

Planform evolution and terrestrial habitat health of two representative mid-channel bars (Baishazhou bar and Tianxingzhou bar) in the urban reach of the Middle Yangtze River in Wuhan City have not been understood under the combined influences of natural forcing and human activities. Using [...] Read more.

Planform evolution and terrestrial habitat health of two representative mid-channel bars (Baishazhou bar and Tianxingzhou bar) in the urban reach of the Middle Yangtze River in Wuhan City have not been understood under the combined influences of natural forcing and human activities. Using dry-season Landsat imagery (1989–2020), hydrological records from the Hankou gauging station (1990–2019), and field surveys, we quantified bar-morphology changes and examined the mechanisms underlying their differentiated scouring. We also developed an indicator system to evaluate terrestrial habitat health on mid-channel bars. Indicator weights were determined using a combined weighting approach integrating the Analytic Hierarchy Process and the entropy weight method. Since the Three Gorges Dam began operation, the runoff in the Wuhan reach has decreased only slightly (6.72%), whereas sediment load decreased sharply (69.88%), causing net scouring of both bars. Baishazhou bar, in a straight anabranching reach, lost 43.83% of its area (1989–2020), with erosion concentrated at the head and main channel margin and caving. Tianxingzhou bar, in a mildly curved reach, had moderate shrinkage (26.33%, 1992–2022) as revetments curbed head/right margin retreat. Both bars were “very healthy” in natural attributes, with the Baishazhou bar showing longer water–land ecotone exposure (217 d) and higher vegetation cover (92%). Socially, Baishazhou bar was “sub-healthy” due to unprotected shrinkage, and Tianxingzhou bar was “unhealthy” due to area loss and low permeability of hard works. Overall, both bars were “healthy”. These findings provide a basis for ecological conservation and habitat restoration of bar wetlands. Full article

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

► Show Figures

Figure 1

19 pages, 4815 KB

Open AccessArticle

Comparison of Hydraulic Behavior of Single-Baffled Block Stepped Spillways Between Regular and Irregular Designs

by Hassan Jasim Alrikaby, Abdul-Hassan K. Al-Shukur, Ahmed Mageed Hussein, Halah Kadhim Tayyeh, Brahim Benzougagh, Qosai S. Radi Marshdi, Amnah Alasqah and Khaled Mohamed Khedher

Water 2026, 18(5), 629; https://doi.org/10.3390/w18050629 - 6 Mar 2026

Abstract

This study evaluated the hydraulic performance of regular and irregular stepped spillways experimentally to reduce the hydraulic leap length and enhance energy dissipation. The study tested fourteen physical models with 40° and 45° slopes and step numbers of 5 and 10, analyzing the [...] Read more.

This study evaluated the hydraulic performance of regular and irregular stepped spillways experimentally to reduce the hydraulic leap length and enhance energy dissipation. The study tested fourteen physical models with 40° and 45° slopes and step numbers of 5 and 10, analyzing the effect of a single barrier block and its horizontal position through 98 rectangular flume experiments to evaluate energy dissipation and hydraulic jump length. The results showed that when the nappe flow transitioned to the skimming flow, energy dissipation decreased as discharge increased. Irregular stepped spillways achieved higher energy dissipation than regular ones by about 10–25%, with five-step models outperforming ten-step models due to increased turbulence. A strong positive relationship between discharge and hydraulic jump length was also observed, with jump length increasing by approximately 30–45% at 40° and 45° slopes. Five-degree irregular stepped spillways produced the shortest hydraulic jump lengths, confirming that step irregularity reduces downstream residual energy. Adding a single barrier block improved performance by shortening the hydraulic jump by about 20–35%, especially at higher discharges, with the optimal position at B/2. Overall, an irregular stepped spillway with a barrier block at B/2 was identified as the most effective configuration, enabling shorter hydraulic jumps, smaller stilling basins, and more efficient and economical spillway designs. Full article

(This article belongs to the Special Issue Advances in Open-Channel Flow Hydrodynamics)

► Show Figures

Figure 1

15 pages, 10069 KB

Open AccessArticle

Hazard Assessment for Potential GLOF of JiongpuCo Glacial Lake, Southeastern Tibet

by Na He, Xuan Liu, Hao Wang, Weiming Liu, Miaohui Zhang, Jingxuan Cao and Yang Yang

Water 2026, 18(5), 628; https://doi.org/10.3390/w18050628 - 6 Mar 2026

Abstract

This study examined the glacial lake of JiongpuCo in the southeastern Tibet region. According to satellite images obtained by Landsat Thematic Mapper (TM) and Operational Land Imager (OLI) from 1995 to 2025, JiongpuCo’s area expanded from 1.92 ± 0.06 km² to 5.26 [...] Read more.

This study examined the glacial lake of JiongpuCo in the southeastern Tibet region. According to satellite images obtained by Landsat Thematic Mapper (TM) and Operational Land Imager (OLI) from 1995 to 2025, JiongpuCo’s area expanded from 1.92 ± 0.06 km² to 5.26 ± 0.02 km², which is a 174% increase over 30 years. The lake was in a state of dynamic equilibrium. The bathymetric data showed that JiongpuCo has a basin-like morphology. Its reservoir capacity curve was concave-up, with a maximum water depth of 237 m and total reservoir capacity of 6.35 × 10⁸ m³. A sequential HEC-RAS-MIKE 21 numerical modeling framework was constructed to simulate flood propagation. For three simulated scenarios (with breach volumes of 80%, 60%, and 30%), the peak discharge at the breach outlet was 28,368.45 m³/s, 25,451.67 m³/s, and 17,855.54 m³/s. Analysis of the simulation results shows that the glacier lake outburst flood (GLOF) has continuous attenuation of peak discharge and a gradual lag in arrival time along the flow path. Except for Bagai in Scenarios 2 and 3, all other target research towns and villages were flooded by floodwaters. These findings offer a solid scientific foundation for the reduction in GLOF disasters and the development of an early warning system for JiongpuCo. Full article

(This article belongs to the Special Issue Intelligent Analysis, Monitoring and Assessment of Debris Flow)

► Show Figures

Figure 1

Journal Description

Water

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Further Information

Guidelines

MDPI Initiatives

Follow MDPI