Water

16 pages, 1602 KB

Open AccessReview

Multi-Stable Isotope Constraints on the Sources and Evolution of Potash-Forming Fluids in the Mahai Basin, Qinghai–Tibetan Plateau

by Zhendong Wang, Qiugui Wang, Zengping Ning, Weigang Su, Ying Ma, Yujun Ma, Enzong Xiao and Xiaohang Lu

Water 2026, 18(4), 443; https://doi.org/10.3390/w18040443 (registering DOI) - 7 Feb 2026

Abstract

The Mahai Basin (MHB), situated in the northern Qaidam Basin on the Qinghai–Tibetan Plateau, hosts significant Quaternary potash resources. Nevertheless, the sources and evolutionary pathways of potash-forming fluids remain controversial. In this study, a comprehensive multi-isotope dataset and online-first publications spanning the period [...] Read more.

The Mahai Basin (MHB), situated in the northern Qaidam Basin on the Qinghai–Tibetan Plateau, hosts significant Quaternary potash resources. Nevertheless, the sources and evolutionary pathways of potash-forming fluids remain controversial. In this study, a comprehensive multi-isotope dataset and online-first publications spanning the period from 2015 to 2025 were compiled to constrain the end-member characteristics and evolution of brines in the MHB. δD-δ¹⁸O indicates that the initial fluids were derived mainly from Qilian Mountains precipitation and snowmelt, delivered via surface runoff and concentrated through prolonged evaporation under arid, semi-closed conditions, forming a river-lake-brine evolution sequence. δ⁷Li (+7‰ to +40‰) systematically increases with salinity and K content, reflecting long-term low-temperature water–rock interactions and selective ⁶Li adsorption by secondary clays, while deep Ca-Cl brines represent highly evolved endmembers. Elevated ⁸⁷Sr/⁸⁶Sr ratios (0.7113–0.7122) confirm silicate weathering contributions, with intercrystalline brines acting as key intermediate end members. B, S, and Cl isotopes further highlight deep fluid ascent along faults and anticlines, driving K co-enrichment, while sandy–gravel brines inherit highly evolved paleo-lake signatures. These multi-isotope constraints define an integrated evolutionary model involving surface runoff recharge, evaporation-driven concentration with water–rock interaction, deep fluid mixing, lateral migration, and final potash precipitation. Full article

(This article belongs to the Special Issue Contaminants in Aquatic Systems: Biogeochemical Processes, Ecological Impacts)

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20 pages, 3022 KB

Open AccessArticle

Near-Future Climate Change Impacts on Sado River (Southern Portugal) Flow Rates Using CMIP6-HSPF Modelling

by André M. Claro, André R. Fonseca, António Fernandes, Christoph Menz, Carina Almeida, Helder Fraga and João A. Santos

Water 2026, 18(4), 442; https://doi.org/10.3390/w18040442 (registering DOI) - 7 Feb 2026

Abstract

Climate change impacts on the Sado River (southwest Portugal) flow rates (FRs) were assessed for the first time under the 2041–2060 Shared Socioeconomic Pathways: 1–2.6 W/m² (SSP1-2.6), 3–7.0 W/m² (SSP3-7.0), and 5–8.5 W/m² (SSP5-8.5), using bias-adjusted and downscaled General Circulation [...] Read more.

Climate change impacts on the Sado River (southwest Portugal) flow rates (FRs) were assessed for the first time under the 2041–2060 Shared Socioeconomic Pathways: 1–2.6 W/m² (SSP1-2.6), 3–7.0 W/m² (SSP3-7.0), and 5–8.5 W/m² (SSP5-8.5), using bias-adjusted and downscaled General Circulation Model (GCM) ensemble projections from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3b-Sado). ISIMIP3b-Sado was used to estimate future precipitation and temperature changes, and as input for Hydrological Simulation Program—FORTRAN (HSPF) simulations. The HSPF projected decreases in the Sado FRs, mainly under SSP3-7.0 and SSP5-8.5, due to temperature increases and autumn/spring precipitation decreases. The FR decreases may lead to 29%/33% reductions in yearly accumulated riverine water volume under SSP3-7.0/SSP5-8.5 and a 31% summertime riverine water deficit increase under SSP3-7.0. Surface-water demand fulfilment in the Sado Basin could suffer a 22-day delay, and the wintertime precipitation range is projected to increase. Hence, in the near-future, summertime surface-water needs and reservoir recharge in the Sado Basin could become more dependent on wintertime precipitation. With Sado being an agricultural region, our results should prompt agriculture stakeholders and decision makers to improve wintertime surface water storage and management to sustain summertime crop irrigation needs. Full article

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

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15 pages, 3303 KB

Open AccessArticle

Enhanced Stormwater Treatment via Thermally Modified Steel Slag-Based Bioretention System: Performance Evaluation and Mechanistic Insights

by Lei Yu, Yiming Nie, Wenen Chai, Jiayi Sha, Tianyin Huang and Bingdang Wu

Water 2026, 18(4), 441; https://doi.org/10.3390/w18040441 (registering DOI) - 7 Feb 2026

Abstract

Conventional bioretention systems face challenges in effectively removing dissolved nutrients, heavy metals, and emerging contaminants from stormwater runoff. This study investigates the application of thermally modified steel slag (700 °C) as a functional bioretention matrix for comprehensive stormwater purification. Three pilot-scale systems were [...] Read more.

Conventional bioretention systems face challenges in effectively removing dissolved nutrients, heavy metals, and emerging contaminants from stormwater runoff. This study investigates the application of thermally modified steel slag (700 °C) as a functional bioretention matrix for comprehensive stormwater purification. Three pilot-scale systems were evaluated over 120 days: Control (biochar-zeolite), Unmodified (raw steel slag-biochar-zeolite), and Modified (thermally modified steel slag-biochar-zeolite). The modified system demonstrated superior and stable removal efficiencies for NH₄⁺-N (95.3 ± 1.3%), TN (85.7 ± 1.8%), TP (90.5 ± 1.5%), Cu²⁺ (96.1 ± 0.7%), Cr⁶⁺ (90.5 ± 1.2%), Pb²⁺ (92.2 ± 1.1%), enrofloxacin (65.6 ± 2.1%), and norfloxacin (62.6 ± 2.4%). Performance remained robust under varying hydraulic conditions, with high removal maintained across rainfall return periods (0.5–2 years) and antecedent dry periods (2–8 days). Mechanistic investigations revealed synergistic effects: (1) Enhanced physical adsorption through increased surface area (2.338 m²/g) and pore volume (0.109 cm³/g); (2) Chemical precipitation via Ca²⁺/Fe³⁺ release at alkaline pH (8.2–8.5); (3) Enriched microbial communities with 35% higher Shannon diversity, particularly Hydrogenophaga (12.3%) for autotrophic denitrification using Fe²⁺ as electron donor. The modified slag matrix creates a “triple-barrier” removal mechanism combining physical, chemical, and biological processes, offering an efficient solution for multi-pollutant stormwater treatment. This study demonstrates that thermally modified steel slag represents a high-performance, cost-effective bioretention matrix for comprehensive stormwater treatment while promoting industrial byproduct utilization and aligning with circular economy principles. Full article

(This article belongs to the Special Issue Urban Water Pollution Control: Theory and Technology, 2nd Edition)

36 pages, 833 KB

Open AccessReview

Data Assimilation and Modeling Frontiers in Soil–Water Systems

by Ying Zhao

Water 2026, 18(4), 440; https://doi.org/10.3390/w18040440 (registering DOI) - 7 Feb 2026

Abstract

Sustainable soil–water management under climate and socio-economic pressures requires predictive capability that is both mechanistic and continuously corrected by observations. Data assimilation (DA) provides the formal machinery to merge models with heterogeneous measurements—from satellite evapotranspiration and soil moisture to cosmic-ray neutron sensing, proximal [...] Read more.

Sustainable soil–water management under climate and socio-economic pressures requires predictive capability that is both mechanistic and continuously corrected by observations. Data assimilation (DA) provides the formal machinery to merge models with heterogeneous measurements—from satellite evapotranspiration and soil moisture to cosmic-ray neutron sensing, proximal geophysics, lysimeters, and groundwater hydrographs—while propagating uncertainty. This review (based on 90 references) synthesizes frontiers in DA and modeling for soil–water systems across scales, emphasizing (i) multi-source observation operators and scaling; (ii) coupled crop–vadose–groundwater modeling frameworks and their structural hypotheses; (iii) modern DA methods (ensemble, variational, particle-based, and hybrid physics–ML) for joint estimation of states, parameters, and biases; and (iv) emerging digital twins that enable predict-then-verify management loops for irrigation, recharge enhancement, and drought risk reduction. We highlight how tracer-aided and isotope-informed components can improve evapotranspiration partitioning and recharge threshold detection, and how agent-based or socio-hydrological coupling can represent human decision feedback. Finally, we outline research gaps in uncertainty quantification, benchmarking, reproducibility, and governance needed to operationalize trustworthy soil–water digital twins for resilient food and water systems. Full article

(This article belongs to the Special Issue Data Assimilation and Modeling for Sustainable Soil–Water Systems)

26 pages, 2409 KB

Open AccessArticle

Integrated Assessment of Bathing Water Quality Along the Romanian Black Sea Coast

by Alina Bărbulescu and Lucica Barbeș

Water 2026, 18(4), 439; https://doi.org/10.3390/w18040439 (registering DOI) - 7 Feb 2026

Abstract

The quality of bathing waters along the Romanian Black Sea coast is critical to environmental conservation and sustainable tourism development. This study assesses water quality at several key beaches along the Black Sea Littoral in Romania, using a dataset collected from 2022 to [...] Read more.

The quality of bathing waters along the Romanian Black Sea coast is critical to environmental conservation and sustainable tourism development. This study assesses water quality at several key beaches along the Black Sea Littoral in Romania, using a dataset collected from 2022 to 2024 at 20 locations. Two methods are employed for this aim. The first utilizes the Bathing Water Directive (BWD), considering only the E. coli (EC) and Intestinal Enterococci (IE) as pollutants. The second proposes a water quality index (WQI) that considers temperature (T), pH, salinity, nitrite ion (NO2-), and ammonia ion (NH4+) together with EC and IE. Results show that while most beaches meet European Union water quality standards, specific areas, particularly in the Năvodari, Vadu, and Mamaia sectors, exhibit elevated bacterial contamination. The findings underscore the need for enhanced wastewater treatment and stricter monitoring to support the region’s eco-friendly tourism aims. Full article

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

18 pages, 2815 KB

Open AccessArticle

Spatiotemporal Variation and Source Apportionment of Total Phosphorus in the Xiangjiang River Based on an Interpretable Association Rule Mining Framework

by Xiaonan Du, Cen Meng, Chao Xu, Shulin Xu, Tingting Zhang, Pingxiu Teng, Ao Deng, Peng Zeng and Feng Liu

Water 2026, 18(4), 438; https://doi.org/10.3390/w18040438 (registering DOI) - 7 Feb 2026

Abstract

Phosphorus enrichment remains a major driver of eutrophication in lake-feeding rivers, yet effective regulation is hindered by insufficient understanding of the spatiotemporal variability and dominant sources of total phosphorus (TP) at the basin scale. The Xiangjiang River, a major inflow to Dongting Lake, [...] Read more.

Phosphorus enrichment remains a major driver of eutrophication in lake-feeding rivers, yet effective regulation is hindered by insufficient understanding of the spatiotemporal variability and dominant sources of total phosphorus (TP) at the basin scale. The Xiangjiang River, a major inflow to Dongting Lake, provides a representative system for examining TP dynamics in a human-impacted watershed. An interpretable association rule mining framework was applied to multi-source water quality, hydrological, agricultural, and socio-economic data (2020–2024) to characterize TP variation and quantify source contributions. TP concentrations exhibit pronounced seasonal and hydrological variability, with higher levels during spring and the flood season and lower levels during autumn and low-flow periods, together with a longitudinal increasing pattern from upstream to downstream. Quantitative source apportionment indicates that agricultural non-point sources dominate TP contributions at the basin scale, domestic sources provide a stable secondary contribution, and industrial sources exert localized influences. The spatial organization of source contributions closely corresponds to land-use patterns, with relatively consistent source structures among sites despite local heterogeneity. These results demonstrate the utility of an interpretable association rule mining framework for resolving TP source structures in heterogeneous river basins. The proposed framework offers a transferable approach for phosphorus source identification and supports basin-scale nutrient management and targeted control of agricultural non-point source pollution. Full article

(This article belongs to the Special Issue Using Artificial Intelligence for Smart Water Management, 2nd Edition)

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14 pages, 3304 KB

Open AccessArticle

Influence of Blade Tip Clearance on External Characteristics and Internal Flow Pattern of Axial Flow Pumps

by Ling Bai, Jie Zhang, Lei Jiang, Hong Xu and Ling Zhou

Water 2026, 18(3), 437; https://doi.org/10.3390/w18030437 - 6 Feb 2026

Abstract

Axial flow pumps, widely utilized in critical fields such as agricultural irrigation, urban water diversion and flood control, play an indispensable role in large-scale water transport and drainage projects due to their high-flow and low-head characteristics. This study systematically investigates the influence of [...] Read more.

Axial flow pumps, widely utilized in critical fields such as agricultural irrigation, urban water diversion and flood control, play an indispensable role in large-scale water transport and drainage projects due to their high-flow and low-head characteristics. This study systematically investigates the influence of tip clearance on the external characteristics and internal flow field of a large-scale axial flow pump (model 1800GZX-125). By combining numerical simulations with experimental validation, a comparative analysis was conducted under four tip clearance sizes (3 mm, 12 mm, 17.5 mm, 24 mm) and various flow conditions. The results indicate that increasing the tip clearance generally reduces the pump head and peak efficiency. It also alters the blade pressure distribution, expands the low-pressure region, and intensifies tip leakage flow. While vorticity overall increases, it weakens locally under certain conditions due to changes in leakage flow patterns. Entropy generation analysis further reveals that larger clearances lead to significantly increased energy losses, thereby degrading external performance. These findings provide a theoretical basis for improving the performance and operational stability of axial flow pumps. Full article

(This article belongs to the Special Issue Hydrodynamics in Pumping and Hydropower Systems, 2nd Edition)

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21 pages, 4464 KB

Open AccessArticle

Future Climate Change Increases Streamflow and Risks of Hydrological Hazards in the Pearl River Basin

by Haoyuan Yu, Qichun Yang, Liuqian Yu, Xia Li, Minyang Li and Yingxian Yang

Water 2026, 18(3), 436; https://doi.org/10.3390/w18030436 - 6 Feb 2026

Abstract

Understanding and predicting climate change impacts on the terrestrial water cycle is essential for water resources management and hazard prevention. This study aims to project future runoff of a densely-populated river basin, the Pearl River Basin (PRB), under different Shared Socioeconomic Pahway (SSP) [...] Read more.

Understanding and predicting climate change impacts on the terrestrial water cycle is essential for water resources management and hazard prevention. This study aims to project future runoff of a densely-populated river basin, the Pearl River Basin (PRB), under different Shared Socioeconomic Pahway (SSP) scenarios, by combining the Soil and Water Assessment Tool (SWAT) model and the CMIP6 climate projections. Results show that climate change will significantly increase the runoff of the PRB, with changing rates of 0.21, 0.20, 0.11, and 0.17 mm/month/year for low- to high-emission scenarios SSP126, SSP245, SSP370, and SSP585, respectively. Future runoff exhibits strong seasonal and spatial variability due to complex changes in precipitation and potential evapotranspiration across the basin. The PRB may experience higher flood risks during the wet season under all SSP scenarios, driven by a ~15% increase in runoff during the wettest month during 2061–2100 relative to that of 2021–2060. Conversely, drought risks may escalate in the East River Sub-basin of the PRB during the dry season under the high-emission scenarios (SSP370 and SSP585), with a ~20% reduction in runoff during the driest month during 2061–2100 relative to that of 2021–2060. The highest-emission scenario (SSP585) may lead to the most drastic hydrological changes, including increased risks of flooding and drought across different parts of the PRB. Our findings suggest intensified water cycling and increased hydrological risks in the PRB under a changing climate, highlighting the necessity of future water resource management to consider potential climate change impacts to mitigate the risks of floods and droughts effectively. Full article

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

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12 pages, 1821 KB

Open AccessArticle

Impact of Food Processing Industry Wastewater on Root Growth and DNA Damage in Allium cepa L. as Assessed by the Comet Assay

by Matiba Tufail, Muhammad Luqman, Zahid Mehmood, Wasim Abbas, Maryam Iqbal, Harma Shah, Imran Farooq Awan, Noor Sana, Arooba John, Samra Rafiq, Awais Riaz, Adeel Ahmad, Anum Tahir and Muhammad Umar Farooq Awan

Water 2026, 18(3), 435; https://doi.org/10.3390/w18030435 - 6 Feb 2026

Abstract

Wastewater from food processing industries contains synthetic dyes and preservatives that may pose phytotoxic and genotoxic risks. The present work represents an exploratory study based on a wastewater source and sampling period. Wastewater was characterized by physicochemical analysis and high-performance liquid chromatography (HPLC). [...] Read more.

Wastewater from food processing industries contains synthetic dyes and preservatives that may pose phytotoxic and genotoxic risks. The present work represents an exploratory study based on a wastewater source and sampling period. Wastewater was characterized by physicochemical analysis and high-performance liquid chromatography (HPLC). Onion seeds and bulbs were exposed to 0% (control), 20%, 40%, 60%, 80%, and 100% wastewater dilution. DNA was extracted from root cells using the cetyltrimethylammonium bromide (CTAB) method. The DNA damage was analyzed by the comet assay. HPLC analysis confirmed the presence of sorbic acid, citric acid, benzoic acid, butylated hydroxyanisole (BHA), and butylated Hydroxytoluene (BHT) by showing corresponding peaks. The mean root length in wastewater was significantly reduced by 55%, 50%, and 65% on days 3, 5, and 7, respectively, relative to the control. On day 3, the highest genotoxicity at 100% wastewater was indicated by 96.69% tail DNA, a tail moment of 108.3 a.u., an Olive tail moment of 58.01 a.u., and a comet length of 136 µm. Enhanced DNA damage persisted on days 5 and 7, with comet lengths reaching 127–149 µm and 111–182 µm, respectively. Although the observed effects may reflect general cytotoxicity arising from a complex wastewater mixture and showed that untreated food processing wastewater presents a significant genotoxic risk and requires effective treatment prior to reuse. Full article

(This article belongs to the Special Issue Advances and Innovations in Technologies for Treatment and Toxicity Assessment of Conventional and Emerging Contaminant in Industrial Wastewater)

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Graphical abstract

19 pages, 1330 KB

Open AccessArticle

Constraint-Aware and Economic Optimization of Riverbank Retaining Walls Using Metaheuristic Algorithms

by Shaymaa Alsamia, Edina Koch and Mais Mayassah

Water 2026, 18(3), 434; https://doi.org/10.3390/w18030434 - 6 Feb 2026

Abstract

The optimal design of riverbank retaining walls requires a careful balance between structural safety, constructability, and economic efficiency. In this study, a constraint-aware optimization framework is developed for the design of concrete gravity retaining walls by explicitly incorporating stability, serviceability, and geometric feasibility [...] Read more.

The optimal design of riverbank retaining walls requires a careful balance between structural safety, constructability, and economic efficiency. In this study, a constraint-aware optimization framework is developed for the design of concrete gravity retaining walls by explicitly incorporating stability, serviceability, and geometric feasibility constraints. Several metaheuristic algorithms are comparatively evaluated under identical computational conditions using 30 independent runs, a population size of 50, and 1000 iterations. The results demonstrate that enforcing geometric constraints is essential to prevent non-physical designs and to ensure engineering realism. Quantitative analysis shows that the Flower Fertilization Optimization (FFO) algorithm yields the minimum wall weight, reducing material usage by approximately 19% compared to more conservative solutions. In contrast, the adaptive exploration artificial bee colony (AEABC) algorithm exhibits the most robust and repeatable convergence behavior with low statistical dispersion across independent runs. An economic assessment based on concrete volume further confirms the direct impact of material efficiency on construction cost. The proposed framework highlights the importance of constraint-aware optimization for achieving reliable and economically efficient retaining wall designs. Full article

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

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20 pages, 1239 KB

Open AccessArticle

Sustainable Selection Criteria for Small Wastewater Treatment Plants Ensuring Biodegradation

by Zbigniew Mucha, Agnieszka Generowicz, Kamil Zieliński, Iga Pietrucha, Anna Kochanek, Piotr Herbut, Paweł Kwaśnicki, Anna Gronba-Chyła and Elżbieta Sobiecka

Water 2026, 18(3), 433; https://doi.org/10.3390/w18030433 - 6 Feb 2026

Abstract

The rapid development of rural and peri-urban areas increases the demand for decentralized wastewater treatment systems. Small wastewater treatment plants (SWTPs) with a capacity below 2000 PE are becoming an important element of local water protection and circular-economy strategies, yet clear guidelines for [...] Read more.

The rapid development of rural and peri-urban areas increases the demand for decentralized wastewater treatment systems. Small wastewater treatment plants (SWTPs) with a capacity below 2000 PE are becoming an important element of local water protection and circular-economy strategies, yet clear guidelines for selecting appropriate technologies are still lacking. This study analyzes the criteria used in decision-making for SWTPs from a multi-stakeholder perspective and evaluates the relative importance of technical, economic, environmental and social factors. The research was conducted in Poland and included a survey of 130 respondents representing six stakeholder groups (officials, operators, designers, contractors, scientists and residents). Respondents allocated weights to four main groups of criteria and assessed eleven detailed parameters on a 1–10 scale. The data were analyzed using descriptive statistics, the Kolmogorov–Smirnov test with the Lilliefors correction to verify distribution assumptions, and the Kruskal–Wallis test to examine differences between stakeholder groups. The results show a consistent hierarchy of criteria, with technical reliability, treatment efficiency and operating costs ranked as the most important factors. Social and environmental aspects were assessed as relevant but secondary. Only minor differences between stakeholder groups were observed. The study highlights the need for integrated, multicriteria approaches in SWTP planning, particularly in dispersed rural areas. The findings may support local authorities, designers and investors in technology selection. The research is limited by the non-probability sampling strategy, the national scope of the dataset and the cross-sectional character of the survey. Full article

(This article belongs to the Special Issue Sustainable Biodegradation and Bioremediation of Organic Contaminants in Aquatic and Terrestrial Environments)

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19 pages, 38597 KB

Open AccessArticle

Hydraulic Characteristics and the Adaptability to Water-Level Fluctuation of the Vertical-Slot Fishway

by Xianglong Huang, Junjun Tan, Yuanyang Wang, Junjian Sun, Sicheng Zeng, Shuaijie Wu and Xiaotao Shi

Water 2026, 18(3), 432; https://doi.org/10.3390/w18030432 - 6 Feb 2026

Abstract

This study explored the hydraulic characteristics and the adaptability to water-level fluctuations of the vertical-slot fishway. The maximum allowable water depth difference between the entrance and exit was calculated for a one-entrance fishway and two-entrance fishways with different entrance distances (100 m, 200 [...] Read more.

This study explored the hydraulic characteristics and the adaptability to water-level fluctuations of the vertical-slot fishway. The maximum allowable water depth difference between the entrance and exit was calculated for a one-entrance fishway and two-entrance fishways with different entrance distances (100 m, 200 m, 300 m) under insufficient entrance water depth, with a fishway slope of 2% and an exit water depth of 2.5 m. It was found that the maximum allowable water depth difference between the 1# entrance and exit of the two-entrance fishways (0.71 m, 0.85 m, 0.93 m) was greatly larger than that of the one-entrance fishway (0.48 m). Additionally, the maximum allowable water depth difference in the two-entrance fishway increased with the increased distance between the two entrances. The relationship between the maximum allowable water depth difference and the distance of the two entrances followed a logarithmic function. We suggested that the 2# entrance should be at least 1.6 m when the water depth of 1# entrance was decreased to 1.8 m. When the water depth of the 1# entrance was gradually decreased to 1.6 m, the water depth of the 2# entrance also gradually decreased to 1.2 m. The distance between the 1# entrance and 2# entrance subsequently changed. It was noteworthy that the conclusions proposed in this study were strictly limited to vertical-slot fishways with a slope of 2%, exit water depth of 2.5 m, similar geometric parameters, and target cyprinid species. Furthermore, different slopes or exit water depths should be studied to extend the relationship by introducing correction coefficients from subsequent studies. This study can provide references for the design and optimization of future fishway projects. Full article

(This article belongs to the Special Issue Ecohydraulics and Fish Behavior Simulation)

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14 pages, 2037 KB

Open AccessArticle

Turbulence in a Bend in the Presence of Emergent Vegetation and a 3D Pool Bedform

by Alirahm Rahimpour, Hossein Afzalimehr, Saeid Okhravi, Mohammad Nazari-Sharabian and Moses Karakouzian

Water 2026, 18(3), 431; https://doi.org/10.3390/w18030431 - 6 Feb 2026

Abstract

The interaction of emergent vegetation and three-dimensional (3D) bedforms is essential for understanding turbulent flow dynamics in curved channels. A laboratory investigation can help to collect required data under controlled conditions. Experiments were conducted in a 9.5 m-long, 0.9 m-wide recirculating flume incorporating [...] Read more.

The interaction of emergent vegetation and three-dimensional (3D) bedforms is essential for understanding turbulent flow dynamics in curved channels. A laboratory investigation can help to collect required data under controlled conditions. Experiments were conducted in a 9.5 m-long, 0.9 m-wide recirculating flume incorporating a 90° bend and a sculpted 3D pool bedform. Artificial rigid vegetation, designed to replicate the hydraulic behavior of natural emergent plants, was installed along both sidewalls. Instantaneous three-dimensional velocities were recorded using an acoustic Doppler velocimeter (ADV) across multiple cross-sections under both bare-bed and vegetated conditions. The results reveal that emergent vegetation markedly increases flow resistance, distorts mean velocity distributions, and suppresses the classical logarithmic velocity profile, particularly within the bend and pool regions. The combined presence of vegetation and the 3D pool bedform amplified turbulence intensity, elevated Reynolds shear stresses, and redistributed turbulent kinetic energy (TKE), which increased by up to sevenfold from the bend entrance to its exit. In vegetated pool sections, Reynolds stresses were approximately 12% greater than under bare-bed conditions, underscoring the synergistic effects of vegetation drag, secondary circulation, and flow separation in producing anisotropic turbulence. These findings highlight the importance of incorporating vegetation–bedform interactions in fluvial modeling frameworks, with significant implications for sediment transport prediction, channel stability evaluation, river restoration, and aquatic habitat design. Full article

(This article belongs to the Special Issue Advancing Hydro-Environmental Research and Practice: Integrating Ecohydrology, Remote Sensing and Hydroinformatics)

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21 pages, 2167 KB

Open AccessArticle

Understanding Spatiotemporal Inundation Dynamics in the Sundarbans Mangroves Through Hydrodynamic Modelling

by Fazlul Karim, Shaikh Nahiduzzaman, Raju Ahmmad, Mohammed Mainuddin, Shahriar Wahid and Rubayat Alam

Water 2026, 18(3), 430; https://doi.org/10.3390/w18030430 - 6 Feb 2026

Abstract

Tidal inundation plays a critical role in maintaining the ecosystem services of the Sundarbans mangrove forest. In this study, we configured and calibrated a coupled one-dimensional (1D) river network and two-dimensional (2D) floodplain hydrodynamic model for the Sundarbans in Bangladesh. Model calibration was [...] Read more.

Tidal inundation plays a critical role in maintaining the ecosystem services of the Sundarbans mangrove forest. In this study, we configured and calibrated a coupled one-dimensional (1D) river network and two-dimensional (2D) floodplain hydrodynamic model for the Sundarbans in Bangladesh. Model calibration was performed using gauged water levels, inundation maps, and Google Earth (Version 7.3.6) imagery. Using the calibrated model, we assessed potential changes in inundation extent, depth, and duration across the Sundarbans for varying freshwater inflow and tidal height scenarios. Results show variation in inundation extent, depth, and duration spatially and temporarily across the Sundarbans. Inundation is relatively less during February-March (end of the dry season) and high in July-August (mid-wet season). Approximately 3158 km² (85.1%) of the Sundarbans experiences at least one inundation in March, increasing to about 3658 km² (98.6%) in July. Although a large proportion of the Sundarbans inundate during daily tidal cycles, the mean inundation depth remains shallow (0.24 to 0.33 m) due to flat topography. The influence of freshwater inflow on inundations is small (<2%). In contrast, the impacts of tidal magnitude are substantial on both inundation extent and depth. These findings provide valuable insights on inundation dynamics for understanding the hydrological and ecological functioning of the Sundarbans. Full article

(This article belongs to the Special Issue Flood Inundation Modeling and Mapping: Application of Hydrodynamic Models, Remote Sensing and Machine Learning Tools)

20 pages, 4107 KB

Open AccessArticle

Analysis of Contaminant Behavior in Loop Pipe System for Ultrapure Water Distribution Using Computational Fluid Dynamics and Autopsy

by Juyoung Andrea Lee, Jinsu Park, Song Lee, Kyunghyun Son and Sangho Lee

Water 2026, 18(3), 429; https://doi.org/10.3390/w18030429 - 6 Feb 2026

Abstract

Ultrapure water (UPW) distribution loops must deliver stable hydraulics while limiting contamination from polymer piping. This study integrates computational fluid dynamics (CFD) with systematic pipe autopsy to examine contaminant behavior in a pilot-scale UPW loop constructed using chlorinated polyvinyl chloride (CPVC) and polyvinylidene [...] Read more.

Ultrapure water (UPW) distribution loops must deliver stable hydraulics while limiting contamination from polymer piping. This study integrates computational fluid dynamics (CFD) with systematic pipe autopsy to examine contaminant behavior in a pilot-scale UPW loop constructed using chlorinated polyvinyl chloride (CPVC) and polyvinylidene fluoride (PVDF) and operated under identical conditions. CFD predicted nearly identical loop-scale velocity, pressure, and temperature fields for both materials, and identified low-shear recirculation at elbows and downstream tees as zones of elevated particle residence. Lagrangian particle tracking (0.05 μm, no-sticking) showed rapid breakthrough and complete flushing within 13 min, providing a hydraulic susceptibility map for transient retention. After eight months of operation, 17 sections were inspected endoscopically and leached at 60 °C. CPVC exhibited yellow–brown discoloration and highly heterogeneous total organic carbon (TOC) release with hot spots of 16–18 mg·L⁻¹, whereas PVDF showed low, spatially uniform TOC (0.4–2.3 mg·L⁻¹) and minimal fouling; inorganic ions remained at sub-mg·L⁻¹ levels for both materials. Overall, geometry governs where contamination can accumulate, while material properties control its magnitude and persistence, with PVDF providing greater resistance to long-term organic contamination than CPVC. Full article

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

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5 pages, 151 KB

Open AccessEditorial

Integrated Approaches to Water Resources and Environmental Management: Innovations in Simulation and Impact Assessment

by Yuntao Wang

Water 2026, 18(3), 428; https://doi.org/10.3390/w18030428 - 6 Feb 2026

Abstract

Water resources and environmental systems face unprecedented pressure from the combined effects of climate change, rapid urbanization, population growth, land-use transformation, and intensifying economic activities [...] Full article

(This article belongs to the Special Issue Integrated Approaches to Water Resources and Environmental Management: Innovations in Simulation and Impact Assessment)

19 pages, 4029 KB

Open AccessArticle

Smart Technological Urban Flood Management Strategies Are “Must-Do” Approaches: The Case of Chinese Coastal Megacity, Ningbo, East Coast of China

by Faith Ka Shun Chan, Weiwei Gu, Fang Zhang, Xiaolei Pei, Zilin Wang, Lingwen Lu, Ming Cheng, Yuhe Wang, Weiguo Zhang and Yutian Jiang

Water 2026, 18(3), 427; https://doi.org/10.3390/w18030427 - 6 Feb 2026

Abstract

Ningbo (NGB), a major port city on China’s east coast, is defined by a network of over 100 rivers across three major catchments. From the 1970s to the 2000s, extensive engineering, including channelisation and embankment construction, was used to manage flood risk during [...] Read more.

Ningbo (NGB), a major port city on China’s east coast, is defined by a network of over 100 rivers across three major catchments. From the 1970s to the 2000s, extensive engineering, including channelisation and embankment construction, was used to manage flood risk during rapid urbanisation. Since the 2010s, however, the city has shifted towards smart flood management. The Ningbo government and Water Bureau have deployed digital twins and technologies like 3D flood mapping and real-time monitoring, significantly improving precision. Our study demonstrated that this smart technology performed effectively during recent extreme events, namely typhoons In-Fa (2021) and Muifa (2022), helping the Municipal Bureau to safeguard public safety. This success strengthens municipal and national commitments to climate resilience. Nevertheless, further advancement of the digital twin platform is required. Key priorities include boosting computational capacity, improving cross-departmental coordination, establishing open data sharing, and integrating artificial intelligence (AI) to enhance decision-making during future climate extremes. Full article

(This article belongs to the Special Issue Water Reuse and Land Management: Strategies, Policies, and Integrated Land-Use Approaches)

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13 pages, 925 KB

Open AccessReview

Marine Pollution in Panama: A Bibliometric Approach to Knowledge Gaps and Institutional Influence

by Nelva E. Alvarado-González, Yulissa De Gracia, Jenifer Ortega, Maricselis Díaz, Yostin Añino, Xabier Lekube, Maren Ortiz-Zarragoitia and Beñat Zaldibar

Water 2026, 18(3), 426; https://doi.org/10.3390/w18030426 - 6 Feb 2026

Abstract

Human activities in Panama, such as agriculture, industry, and transport, have led to the release of pollutants that affect the health of marine and coastal ecosystems. However, there is a lack of bibliographic compilation studies to understand the current state of research on [...] Read more.

Human activities in Panama, such as agriculture, industry, and transport, have led to the release of pollutants that affect the health of marine and coastal ecosystems. However, there is a lack of bibliographic compilation studies to understand the current state of research on marine pollution in Panama. In recent years, bibliometric studies have attracted attention due to the development of new analytical and integrative online tools. This study conducts a bibliometric analysis of marine pollution and its environmental effects on Panama’s coastal areas. The results show consistent growth in scientific production, with increased collaboration among researchers. However, the involvement of national institutions is limited, highlighting the need to strengthen local research. Most publications focus on environmental sciences, with a recent shift towards studying a broader range of pollutants. Full article

(This article belongs to the Section Oceans and Coastal Zones)

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13 pages, 1250 KB

Open AccessArticle

Tritium and Plutonium Time Series from the Puruogangri Ice Field, Tibetan Plateau, China

by László Palcsu, Miruna Cotan, Lide Tian, Cheng Wang, Liu Feng, Xu Chenhao, Yu Songlin, Magdolna Szilágyi, Loránd Zákány, Zoltán Dezső, Danny Vargas and Marjan Temovski

Water 2026, 18(3), 425; https://doi.org/10.3390/w18030425 - 5 Feb 2026

Abstract

Ice cores retrieved from the Third Pole provide invaluable information about past and present environmental changes. Here we present, for the first time, a continuous tritium and plutonium isotope profile of the Puruogangri ice field, Tibetan Plateau, China, for the last 70 years. [...] Read more.

Ice cores retrieved from the Third Pole provide invaluable information about past and present environmental changes. Here we present, for the first time, a continuous tritium and plutonium isotope profile of the Puruogangri ice field, Tibetan Plateau, China, for the last 70 years. The age-depth profile has been composed by different time anchors such as the onset of thermonuclear weapon tests, the so-called bomb peak of tritium, the Chernobyl event, and the time of ice coring. The accumulation rate of ice calculated from the age-depth relation shows a decrease after 1963. It was 57, 15, and 22 cm/year in the periods of 1954–1963, 1963–1986, and 1986–2023, respectively. The concentrations of plutonium isotopes (²³⁹Pu: up to 2.7 fg/g) are slightly lower than those of the Belukha ice core, Siberian Altai, Russia, and almost the same as the Miaoergou glacier, eastern Tien Shan, China. Contrary to this latter ice core profile, the Puruogangri plutonium profile reflects that the Chinese weapon test started in 1966. This is confirmed by the tritium time series as well. ²⁴⁰Pu/²³⁹Pu atomic ratios vary between 0.14 and 0.23, with an average of 0.177 ± 0.024. The overall obtained local fallout of ²³⁹Pu and ²⁴⁰Pu is 13.2 and 9.0 Bq/m² (4.0 and 1.1 ng/m²), respectively. Full article

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

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