Water

19 pages, 1605 KB

Open AccessArticle

Morphology and Ecology of Newly Recorded Diatom Taxa from the Nakdonggang River (South Korea) Revealed by Scanning Electron Microscopy

by Sang Deuk Lee, Mirye Park and Daeryul Kwon

Water 2026, 18(3), 303; https://doi.org/10.3390/w18030303 (registering DOI) - 24 Jan 2026

Abstract

This study reports 10 freshwater diatom taxa newly recorded from the Nakdonggang River Basin, South Korea, based on samples collected in April 2023. Species identification was conducted using scanning electron microscopy (SEM), which enabled detailed observation of valve ultrastructures critical for taxonomic resolution. [...] Read more.

This study reports 10 freshwater diatom taxa newly recorded from the Nakdonggang River Basin, South Korea, based on samples collected in April 2023. Species identification was conducted using scanning electron microscopy (SEM), which enabled detailed observation of valve ultrastructures critical for taxonomic resolution. The newly documented taxa include Achnanthidium druartii, A. peetersianum, Discocyclus hubeianus, Geissleria cascadensis, Gomphonella perolivaceoides, Navicula venetiformis, Punctastriata glubokoensis, P. mimetica, Rhoicosphenia californica, and Sellaphora nigri. Environmental parameters (temperature, pH, conductivity, dissolved oxygen, turbidity) were recorded to characterize habitats. As these taxa are not listed in the National List of Species of Korea, our findings expand the country’s diatom inventory and emphasize the importance of SEM-based surveys in documenting biodiversity and biogeographic distributions. Full article

(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)

► Show Figures

Figure 1

17 pages, 3929 KB

Open AccessArticle

Study on the Hydrodynamic Performance of Pitch–Heave Flapping Wings Under High-Frequency Heave Disturbance

by Ertian Hua, Sihan Li, Xiaopeng Wu and Yang Lin

Water 2026, 18(3), 302; https://doi.org/10.3390/w18030302 (registering DOI) - 24 Jan 2026

Abstract

To improve the pumping performance of biomimetic flapping-wing devices in small river channels, this study introduces high-frequency disturbances in the heave direction based on traditional pitch–heave motion. A systematic investigation of the forces and hydrodynamic performance is conducted using numerical simulations, with vortex [...] Read more.

To improve the pumping performance of biomimetic flapping-wing devices in small river channels, this study introduces high-frequency disturbances in the heave direction based on traditional pitch–heave motion. A systematic investigation of the forces and hydrodynamic performance is conducted using numerical simulations, with vortex contour analysis to explore the evolution mechanism of the wake vortex structure. The results show that high-frequency disturbances cause the instantaneous thrust to exhibit an amplitude modulation feature, with thrust oscillating approximately f_p/f_b times within one base frequency cycle. As the disturbance frequency increases, the average thrust also increases. There is a significant frequency-dependent difference in performance: at low disturbance frequencies (f_p/f_b ≤ 16), changes in thrust, pressure difference, and flow rate are limited, with little improvement in pumping efficiency; at intermediate frequencies (16 < f_p/f_b ≤ 32), wake coherence and jet momentum flux are significantly enhanced, and both thrust and pumping efficiency reach their maximum (up to 47%); at high disturbance frequencies (f_p/f_b > 32), although the vortex structure is further strengthened, input power increases sharply, leading to a decrease in efficiency. Overall, moderate disturbance frequencies can effectively enhance the thrust and pumping performance of the flapping wing, while excessively high frequencies do not offer an advantage due to the high energy cost. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

21 pages, 1038 KB

Open AccessReview

A Systematic Review of Factors Influencing Life Cycle Assessment Outcomes in Aquaponics

by Syed Ejaz Hussain Mehdi, Aparna Sharma, Suleman Shahzad, Sandesh Pandey, Fida Hussain, Woochang Kang and Sang-Eun Oh

Water 2026, 18(3), 301; https://doi.org/10.3390/w18030301 - 23 Jan 2026

Abstract

Aquaponic systems are the integration of aquaculture and hydroponic systems to enhance productivity, reduce land use, and improve sustainability. This review focused on commonly used life cycle assessment (LCA) methodologies, system boundaries, and functional units used in aquaponics, standard impact categories, and identified [...] Read more.

Aquaponic systems are the integration of aquaculture and hydroponic systems to enhance productivity, reduce land use, and improve sustainability. This review focused on commonly used life cycle assessment (LCA) methodologies, system boundaries, and functional units used in aquaponics, standard impact categories, and identified hotspots. The scope is worldwide and encompasses a variety of aquaponic designs, fish species, and crops, illustrating the diversity of the systems examined. The analysis indicates that aquaponics provides the considerable environmental advantages of decreased fertilizer consumption and water conservation in comparison with aquaculture and hydroponic system. However, aquaponics systems are characterized by high energy consumption and may produce greater greenhouse gas (GHG) emissions compared to traditional farming methods when reliant on fossil fuel energy sources. Studies show that fish feed production, system infrastructure, and electricity usage for pumps, lights, heating, and other controls are hotspots. Harmonized comparisons of previous studies show methodological differences, especially in fish–plant co-production. Despite these variations, most believe that energy efficiency, renewable energy, feed optimization, and waste reuse may make aquaponics more sustainable. The study recommends the inclusion of broader environmental and social impacts. Also, future focus might be on making a standard functional unit or specifying system boundaries which might provide different accurate outcomes. Full article

(This article belongs to the Special Issue Advanced Water Management for Sustainable Aquaculture)

21 pages, 2026 KB

Open AccessReview

Adsorption and Removal of Emerging Pollutants from Water by Activated Carbon and Its Composites: Research Hotspots, Recent Advances, and Future Prospects

by Hao Chen, Qingqing Hu, Haiqi Huang, Lei Chen, Chunfang Zhang, Yue Jin and Wenjie Zhang

Water 2026, 18(3), 300; https://doi.org/10.3390/w18030300 - 23 Jan 2026

Abstract

The continuous detection of emerging pollutants (EPs) in water poses potential threats to aquatic environmental safety and human health, and their efficient removal is a frontier in environmental engineering research. This review systematically summarizes research progress from 2005 to 2025 on the application [...] Read more.

The continuous detection of emerging pollutants (EPs) in water poses potential threats to aquatic environmental safety and human health, and their efficient removal is a frontier in environmental engineering research. This review systematically summarizes research progress from 2005 to 2025 on the application of activated carbon (AC) and its composites for removing EPs from water and analyzes the development trends in this field using bibliometric methods. The results indicate that research has evolved from the traditional use of AC for adsorption to the design of novel materials through physical and chemical modifications, as well as composites with metal oxides, carbon-based nanomaterials, and other functional components, achieving high adsorption capacity, selective recognition, and catalytic degradation capabilities. Although AC-based materials demonstrate considerable potential, their large-scale application still faces challenges such as cost control, adaptability to complex water matrices, material regeneration, and potential environmental risks. Future research should focus on precise material design, process integration, and comprehensive life-cycle sustainability assessment to advance this technology toward highly efficient, economical, and safe solutions, thereby providing practical strategies for safeguarding water resources. Full article

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

► Show Figures

Figure 1

20 pages, 2626 KB

Open AccessArticle

Integrating Performance Indicators and Simulation Model for Assessing Operational Performance of Water Distribution Pipe System (WDPS) in Irrigation District

by Jintao Liu and Yanan Liu

Water 2026, 18(3), 299; https://doi.org/10.3390/w18030299 - 23 Jan 2026

Abstract

Water distribution pipe systems (WDPSs) are critical for delivering irrigation water in an irrigation district. Ensuring the WDPS operates with good operational performance has become a key focus for irrigation water management. Assessing the operational performance of WDPS from both water delivery capacity [...] Read more.

Water distribution pipe systems (WDPSs) are critical for delivering irrigation water in an irrigation district. Ensuring the WDPS operates with good operational performance has become a key focus for irrigation water management. Assessing the operational performance of WDPS from both water delivery capacity and pressure changes is compatible with the system, but such an approach has rare been proposed systematically. This paper establishes an integrated framework to assess the performance of WDPS by combining a performance indicator system with a simulation model. The performance indicator system encompasses Adequacy, Efficiency, Equity, and Pressure Reliability, capturing both water delivery capacity and pressure changes. The simulation model is established for providing required data for calculating the performance indicators. Applied to a case study, the framework demonstrates its applicability. Under the specified conditions of the case study, the overall assessment results of WDPS are Adequacy (0.99), Efficiency (0.993), Equity (0.0484), and Pressure Reliability (0.82). Meanwhile, the assessment results at different outlet nodes of the WDPS indicate that there may be insufficient pressure and excessive water supply at some outlet nodes of the WDPS. Further interpretation of the results indicates that the proposed method has the potential to be beneficial for irrigation water management, as it enables strategic assessment of the future operational performance of water distribution pipe systems (WDPSs) and provides effective management guidance for irrigation district managers. Full article

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

► Show Figures

Figure 1

13 pages, 2371 KB

Open AccessFeature PaperArticle

Facet-Dependent Electrocatalysis of Spinel Co₃O₄ for Enhanced Chlorine-Mediated Ammonia Oxidation

by Xuanxu Shen and Fang Ma

Water 2026, 18(3), 298; https://doi.org/10.3390/w18030298 - 23 Jan 2026

Abstract

Facet engineering has emerged as a promising approach to tailor the catalytic performance of metal oxides for environmental electrocatalysis. Herein, we synthesized spinel Co₃O₄ nanocrystals with predominantly exposed {110}, {111}, and {112} facets to investigate their facet-dependent electrocatalytic activity toward [...] Read more.

Facet engineering has emerged as a promising approach to tailor the catalytic performance of metal oxides for environmental electrocatalysis. Herein, we synthesized spinel Co₃O₄ nanocrystals with predominantly exposed {110}, {111}, and {112} facets to investigate their facet-dependent electrocatalytic activity toward chlorine-mediated ammonia oxidation. Structural characterization confirmed the successful fabrication of well-defined {110} nanorods, {111} octahedra, and {112} nanoplates. Electrochemical evaluation revealed a distinct activity trend: {110} > {112} > {111}. The Co₃O₄ {110} facet exhibited the lowest chlorine evolution potential, the smallest charge-transfer resistance, and the highest ammonia removal rate, achieving nearly complete oxidation of 75 mg L⁻¹ NH₄⁺-N within 2 h at 15 mA cm⁻². Mechanistic studies demonstrated that free chlorine species (HOCl/OCl⁻), rather than hydroxyl or chlorine radicals, serve as the primary oxidants. XPS and CV analyses further indicated that the superior activity of the {110} facet is attributed to its higher proportion of Co³⁺ sites and greater oxygen vacancy density, which enhance chloride adsorption and facilitate the Co³⁺/Co²⁺ redox cycle critical for the chlorine evolution reaction. This work elucidates the intrinsic structure–activity relationships of Co₃O₄ facets and provides a rational strategy for designing efficient electrocatalysts for electrochemical ammonia removal. Full article

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

► Show Figures

Figure 1

31 pages, 27773 KB

Open AccessArticle

Machine Learning Techniques for Modelling the Water Quality of Coastal Lagoons

by Juan Marcos Lorente-González, José Palma, Fernando Jiménez, Concepción Marcos and Angel Pérez-Ruzafa

Water 2026, 18(3), 297; https://doi.org/10.3390/w18030297 - 23 Jan 2026

Abstract

This study evaluates the performance of several machine learning models in predicting dissolved oxygen concentration in the surface layer of the Mar Menor coastal lagoon. In recent years, this ecosystem has suffered a continuous process of eutrophication and episodes of hypoxia, mainly due [...] Read more.

This study evaluates the performance of several machine learning models in predicting dissolved oxygen concentration in the surface layer of the Mar Menor coastal lagoon. In recent years, this ecosystem has suffered a continuous process of eutrophication and episodes of hypoxia, mainly due to continuous influx of nutrients from agricultural activities, causing severe water quality deterioration and mortality of local flora and fauna. In this context, monitoring the ecological status of the Mar Menor and its watershed is essential to understand the environmental dynamics that trigger these dystrophic crises. Using field data, this study evaluates the performance of eight predictive modelling approaches, encompassing regularised linear regression methods (Ridge, Lasso, and Elastic Net), instance-based learning (k-nearest neighbours, KNN), kernel-based regression (support vector regression with a radial basis function kernel, SVR-RBF), and tree-based ensemble techniques (Random Forest, Regularised Random Forest, and XGBoost), under multiple experimental settings involving spatial variability and varying time lags applied to physicochemical and meteorological predictors. The results showed that incorporating time lags of approximately two weeks in physicochemical variables markedly improves the models’ ability to generalise to new data. Tree-based regression models achieved the best overall performance, with eXtreme Gradient Boosting providing the highest evaluation metrics. Finally, analysing predictions by sampling point reveals spatial patterns, underscoring the influence of local conditions on prediction quality and the need to consider both spatial structure and temporal inertia when modelling complex coastal lagoon systems. Full article

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

► Show Figures

Figure 1

21 pages, 7081 KB

Open AccessArticle

Synergistic Coupling of In Situ Oxygenation and Advanced Oxidation Processes Using a Novel Lime-Based Composite for Water Quality Management in Litopenaeus vannamei Ponds

by Muhammad Irfan Afif, Hanifah Widi Astuti, Niken Tunjung Murti Pratiwi, Bambang Widigdo, Mohammad Khotib, Nia Rosiana and Muhammad Faisal

Water 2026, 18(3), 296; https://doi.org/10.3390/w18030296 - 23 Jan 2026

Abstract

Effective management of water quality is critical for Litopenaeus vannamei aquaculture, yet it remains a significant technological hurdle for traditional farmers facing benthic anaerobiosis and toxic metabolite accumulation. This study introduces a novel approach by synergistically integrating calcium peroxide (CaO₂), titanium [...] Read more.

Effective management of water quality is critical for Litopenaeus vannamei aquaculture, yet it remains a significant technological hurdle for traditional farmers facing benthic anaerobiosis and toxic metabolite accumulation. This study introduces a novel approach by synergistically integrating calcium peroxide (CaO₂), titanium dioxide (TiO₂), and peracetic acid (PAA) encapsulated within Fe–alginate granules. Unlike conventional methods that treat oxygen depletion and toxicity separately, this composite is designed to simultaneously facilitate in situ oxygenation and advanced oxidation processes (AOPs) directly at the sediment–water interface. The physicochemical properties and radical generation mechanisms of the synthesized composites were characterized using FTIR, XRD, SEM, and ESR. In laboratory simulations of pond conditions, the synergistic efficacy of these composites was evaluated against critical parameters, including dissolved oxygen (DO), ammonia, and sulfide. Experimental results revealed that the application of 5 mg/L CP-T-PAA product to the sediment with an AOP system exhibited superior performance, generating the highest intensity of hydroxyl (•OH) and superoxide (•O₂⁻) radicals. This optimized treatment effectively maintained DO levels above ~2 mg/L at the sediment–water interface for 21 days (3 weeks) and achieved removal efficiencies of 94% for ammonia, 89% for sulfide, and 93% for turbidity. Multi-criteria decision analysis (TOPSIS) validated this formulation as the ideal solution. Consequently, this novel composite presents a sustainable, user-friendly strategy for enhancing environmental stability in traditional shrimp farming. Full article

(This article belongs to the Topic Advanced Oxidation Processes: Applications and Prospects, 2nd Volume)

24 pages, 4010 KB

Open AccessArticle

Bridging Time-Scale Mismatch in WWTPs: Long-Term Influent Forecasting via Decomposition and Heterogeneous Temporal Attention

by Wenhui Lei, Fei Yuan, Yanjing Xu, Yanyan Nie and Jian He

Water 2026, 18(3), 295; https://doi.org/10.3390/w18030295 - 23 Jan 2026

Abstract

The time-scale mismatch between rapid influent fluctuations and slow biochemical responses hinders the stability of wastewater treatment plants (WWTPs). Existing models often fail to capture shock signals due to noise interference (“signal pollution”). To address this, we propose the HD-MAED-LSTM model, which employs [...] Read more.

The time-scale mismatch between rapid influent fluctuations and slow biochemical responses hinders the stability of wastewater treatment plants (WWTPs). Existing models often fail to capture shock signals due to noise interference (“signal pollution”). To address this, we propose the HD-MAED-LSTM model, which employs a “decompose-and-conquer” strategy. Targeting the dynamic characteristics of different components, this study innovatively designs heterogeneous attention mechanisms: utilizing Long-term Dependency Attention to capture the global evolution of the trend component, employing Multi-scale Periodic Attention to reinforce the cyclic patterns of the seasonal component, and using Gated Anomaly Attention to keenly capture sudden shocks in the residual component. In a case study, the effectiveness of the proposed model was validated based on one year of operational data from a large-scale industrial WWTP. HD-MAED-LSTM outperformed baseline models such as Transformer and LSTM in the medium-to-long-term (10-h) prediction of COD, TN, and TP, clearly demonstrating the positive role of differentiated modeling. Notably, in the core task of shock load early warning, the model achieved an F1-Score of 0.83 (superior to Transformer’s 0.77 and LSTM’s 0.67), and a Mean Directional Accuracy (MDA) as high as 0.93. Ablation studies confirm that the specialized attention mechanism is the key performance driver, reducing the Mean Absolute Error (MAE) by 56.7%. This framework provides precise support for shifting WWTPs from passive response to proactive control. Full article

(This article belongs to the Special Issue Pathways to Carbon Neutrality in Water Systems: The Role of LCA, Ecological Engineering, and Pollution Control)

► Show Figures

Figure 1

17 pages, 990 KB

Open AccessReview

Review on Riverine Bacteria from the Perspective of River Dynamics

by Yanlin Du and Shan Zheng

Water 2026, 18(3), 294; https://doi.org/10.3390/w18030294 - 23 Jan 2026

Abstract

Riverine bacteria are vital to geochemical cycling, climate change, and water environments, and the relative research requires knowledge from multiple disciplines, including microbiology, ecology and river dynamics. The influence of river dynamics and morphology on riverine bacteria is drawing increasing attention; yet, there [...] Read more.

Riverine bacteria are vital to geochemical cycling, climate change, and water environments, and the relative research requires knowledge from multiple disciplines, including microbiology, ecology and river dynamics. The influence of river dynamics and morphology on riverine bacteria is drawing increasing attention; yet, there are few comprehensive reviews on the riverine bacteria from the perspective of river dynamics. Therefore, this paper systematically reviews the research progress from the perspective of river dynamics, focusing on the research techniques and methods of riverine bacteria, the impact of hydrodynamic conditions, the ecological effects of dam construction, and the spatial distribution pattern of river bacteria. The review indicates that hydrodynamic processes and human activities such as dam construction drive community reorganization of planktonic and sedimentary bacteria across scales from microhabitats to macrolandscapes by altering aquatic environments, promoting microbial interactions, and affecting diversity, thereby shaping their complex spatiotemporal distribution patterns. Finally, this paper looks forward to future research directions, emphasizing the need to further reveal the diversity of planktonic and sedimentary bacteria, their genetic functions and community construction mechanisms, and to deeply analyze the feedback driving relationship between hydrodynamics, river morphology and riverine bacteria. Full article

(This article belongs to the Special Issue Environmental and Anthropogenic Influences on Freshwater Biodiversity and Ecosystem Health)

► Show Figures

Figure 1

17 pages, 1556 KB

Open AccessArticle

Using Biokinetic Modeling and Dielectric Monitoring to Assess Anaerobic Digestion of Meat-Processing Sludge Pretreated with Microwave Irradiation and Magnetic Nanoparticles

by Zoltán Péter Jákói, Erzsébet Illés, Réka Dobozi and Sándor Beszédes

Water 2026, 18(3), 293; https://doi.org/10.3390/w18030293 - 23 Jan 2026

Abstract

This study investigated the effects of microwave (MW) pre-treatment (45 kJ total irradiated microwave energy) and magnetic nanoparticles (MPs) on the anaerobic digestion (AD) of meat-processing sludge, integrating biokinetic modeling with dielectric parameter measurements. Five different sludge variants were examined: native (non-treated control); [...] Read more.

This study investigated the effects of microwave (MW) pre-treatment (45 kJ total irradiated microwave energy) and magnetic nanoparticles (MPs) on the anaerobic digestion (AD) of meat-processing sludge, integrating biokinetic modeling with dielectric parameter measurements. Five different sludge variants were examined: native (non-treated control); MP-only control; microwave pre-treated sludge, and MW + MP combination with the nanoparticles either retained in the fermentation medium or removed prior to anaerobic digestion. Cumulative biomethane production was evaluated using the modified Gompertz, Logistic, and Weibull models, and key kinetic parameters (maximum achievable methane yield, maximum rate of product formation, and λ-values) were compared across the different treatments. The results revealed that the highest production rate, along with the highest biomethane potential, could be achieved when combining MW treatment with magnetic nanoparticles which were retained in the fermentation medium during AD. Based on the biokinetic analysis, this combined method increased biomethane potential by 52% to 390 mL CH₄/gVS and maximum methane production rate by 85% to 37 mL CH₄/gVS/day compared to the untreated control. The measurement of relative permittivity (

ε^{'}

) exhibited progressive changes during digestion, and the maximum rate of change in

ε^{'}

strongly correlated with the maximum methane production rate across all samples (R² > 0.98). These results highlight the potential of microwave–metal oxide nanoparticle pre-treatment for process enhancement and to demonstrate the suitability of dielectric parameter measurement as a rapid, non-invasive indicator of biochemical activity during anaerobic digestion. Full article

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

► Show Figures

Graphical abstract

32 pages, 6728 KB

Open AccessArticle

The Development of Long-Term Mean Annual Total Nitrogen and Total Phosphorus Load Models for Mississippi, U.S., Using RSPARROW

by Victor L. Roland II, Emily Gain and Matthew Hicks

Water 2026, 18(3), 292; https://doi.org/10.3390/w18030292 - 23 Jan 2026

Abstract

Water-quality degradation from nutrient pollution remains a major challenge for resource managers. Developing effective strategies requires tools to characterize nutrient sources and transport. This study used the RSPARROW framework to develop and assess new, smaller-scale models for Total Nitrogen (TN) and Total Phosphorus [...] Read more.

Water-quality degradation from nutrient pollution remains a major challenge for resource managers. Developing effective strategies requires tools to characterize nutrient sources and transport. This study used the RSPARROW framework to develop and assess new, smaller-scale models for Total Nitrogen (TN) and Total Phosphorus (TP) transport across Mississippi (MS). These state-level models were built using 15 years (2005–2020) of observation data and considered variables including multiple nutrient sources, land characteristics, and attenuation processes. The MS models demonstrated comparable accuracy to larger regional SPARROW models, validating the use of smaller-scale models for local management. Results showed agricultural sources are the major contributors to TN, dominated by fertilizer in northern MS and livestock manure in the south. Urban land cover also significantly influenced TN and was the second most significant source of TP, following geologic material (background P). Fertilizer and manure were also important TP sources. This study provides valuable, spatially explicit data on nutrient distribution in MS streams, supporting the state’s nutrient reduction planning. It concludes by highlighting the need for future model improvements via updated source data and mean annual flow estimates. Full article

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

25 pages, 4518 KB

Open AccessArticle

Time Series Analysis and Periodicity Analysis and Forecasting of the Dniester River Flow Using Spectral, SSA, and Hybrid Models

by Serhii Melnyk, Kateryna Vasiutynska, Oleksandr Butenko, Iryna Korduba, Roman Trach, Alla Pryshchepa, Yuliia Trach and Vitalii Protsiuk

Water 2026, 18(2), 291; https://doi.org/10.3390/w18020291 - 22 Jan 2026

Abstract

This study applies spectral analysis and singular spectrum analysis (SSA) to mean annual runoff of the Dniester River for 1950–2024 to identify dominant periodic components governing the hydrological regime of this transboundary basin shared by Ukraine and Moldova. The novelty lies in a [...] Read more.

This study applies spectral analysis and singular spectrum analysis (SSA) to mean annual runoff of the Dniester River for 1950–2024 to identify dominant periodic components governing the hydrological regime of this transboundary basin shared by Ukraine and Moldova. The novelty lies in a basin-specific integration in the first systematic application of a combined spectral–SSA framework to the Dniester River, enabling consistent characterization of runoff variability and assessment of large-scale natural drivers. Time series from three gauging stations are analysed to develop data-driven runoff models and medium-term forecasts. Four stable groups of periodic variability are identified, with characteristic timescales of approximately 30, 11, 3–5.8, and 2 years, corresponding to major atmospheric–oceanic oscillations (AMO, NAO, PDO, ENSO, QBO) and the 11-year solar cycle. Cross-spectral and coherence analyses reveal a statistically significant relationship between solar activity and river discharge, with an estimated lag of about 2 years. SSA reconstructions explain more than 80% of discharge variance, indicating high model reliability. Forecast comparisons show that spectral methods tend to amplify long-term trends, CNN–LSTM models produce conservative trajectories, while a hybrid ensemble approach provides the most balanced and physically interpretable projections. Ensemble forecasts indicate reduced runoff during 2025–2028, followed by recovery in 2029–2034, supporting long-term water-resources planning and climate adaptation. Full article

(This article belongs to the Section Hydrology)

► Show Figures

Figure 1

31 pages, 1227 KB

Open AccessReview

Physicochemical Properties and Adsorption Mechanisms of Bentonite–Sawdust-Derived Carbon Composites

by Rabiga M. Kudaibergenova, Olzhas N. Nurlybayev, Ivan Kazarinov, Aisha N. Nurlybayeva, Seitzhan A. Orynbayev, Nazgul S. Murzakasymova, Elvira A. Baibazarova and Arman A. Kabdushev

Water 2026, 18(2), 290; https://doi.org/10.3390/w18020290 - 22 Jan 2026

Abstract

The escalating global water crisis necessitates the development of efficient, sustainable, and cost-effective remediation technologies. This review highlights bentonite–sawdust-derived carbon composites as a promising class of adsorbents for the removal of diverse water pollutants. The synthesis strategies, physicochemical properties, key interfacial adsorption mechanisms, [...] Read more.

The escalating global water crisis necessitates the development of efficient, sustainable, and cost-effective remediation technologies. This review highlights bentonite–sawdust-derived carbon composites as a promising class of adsorbents for the removal of diverse water pollutants. The synthesis strategies, physicochemical properties, key interfacial adsorption mechanisms, and adsorption performance toward different pollutant categories are systematically discussed. These hybrid materials exhibit synergistically enhanced properties, including increased surface area, optimized porosity, abundant functional groups, tunable surface charge, and improved structural stability, often outperforming the individual components. Their effectiveness has been demonstrated for both heavy metals (e.g., Cd and Pb) and organic contaminants (e.g., dyes and pharmaceuticals), governed by a combination of ion exchange, electrostatic attraction, π–π interactions, and pore-filling mechanisms. Current challenges related to large-scale production, long-term stability, and regeneration are critically evaluated, and future research directions for the sustainable application of these composites in advanced water treatment systems are outlined. Full article

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

20 pages, 1830 KB

Open AccessArticle

Utilization of Coal-Based Activated Carbon (JA) for the Adsorption of Methyl Orange Azo Dye in Wastewater

by Lihua Dong, Qianwen Xu, Yang Yao, Yingjie Han and Guanghui Zhang

Water 2026, 18(2), 289; https://doi.org/10.3390/w18020289 - 22 Jan 2026

Abstract

Currently, the mainstream methods for dye removal internationally include advanced oxidation, catalytic degradation, and adsorption. Catalytic and oxidation methods are costly and unsuitable for large-scale application. While adsorption is straightforward, selecting and modifying raw materials poses significant challenges. Therefore, identifying readily available and [...] Read more.

Currently, the mainstream methods for dye removal internationally include advanced oxidation, catalytic degradation, and adsorption. Catalytic and oxidation methods are costly and unsuitable for large-scale application. While adsorption is straightforward, selecting and modifying raw materials poses significant challenges. Therefore, identifying readily available and inexpensive adsorbents is crucial for dye removal. This study utilized Type A coal as raw material to prepare a series of specialized activated carbon (JA) for adsorbing methyl orange from wastewater, followed by optimization. The optimized screening results indicated that JA-12 exhibited the highest methyl orange removal rate (90.54%). This performance is attributed to its larger micropore structure and increased pore volume. Further analysis revealed that the adsorption process follows pseudo-second-order kinetics and the Langmuir adsorption isotherm model (R² ≈ 0.999). Compared to the theoretical adsorption capacity calculated based on specific surface area, the adsorption capacity calculated based on pore volume (270.66 mg/g) was closer to the actual adsorption capacity, indicating that the pore structure of JA-12 plays a dominant role in the adsorption process. Combined with the Langmuir adsorption model, it can be inferred that dye molecules in solution adsorb onto the inner surface of JA-12 in a monolayer form. Surface functional group analysis revealed that protonation enhances JA-12’s adsorption capacity for the azo dye methyl orange. Collectively, our findings elucidate the removal mechanism of methyl orange using readily available coal as raw material to prepare low-cost specialty activated carbon, providing a framework for cost-effective, large-scale dye removal. Full article

(This article belongs to the Topic Advanced Processes and Technologies for Wastewater: Collection, Treatment, and Resource)

► Show Figures

Graphical abstract

21 pages, 828 KB

Open AccessArticle

Origin, Composition and Spectroscopic Characteristics of Dissolved Organic Matter in Brine from Yuncheng Salt Lake

by Panyun Jiang, Hailan Chen, Meng Wang, Jinhua Li, Yuhua Cao, Jing Wang and Ming Li

Water 2026, 18(2), 288; https://doi.org/10.3390/w18020288 - 22 Jan 2026

Abstract

Dissolved organic matter (DOM) in salt lake brines comprises organic compounds dissolved in high-salinity aquatic systems. With complex composition and diverse sources, DOM significantly influences biogeochemical cycles, mineral formation, and resource development in salt lakes. However, few studies have investigated the characteristics and [...] Read more.

Dissolved organic matter (DOM) in salt lake brines comprises organic compounds dissolved in high-salinity aquatic systems. With complex composition and diverse sources, DOM significantly influences biogeochemical cycles, mineral formation, and resource development in salt lakes. However, few studies have investigated the characteristics and sources of DOM in salt lake brines. In this study, a DOM sample (YC-4) from brine of Shanxi Yuncheng Salt Lake was isolated and characterized using FT-ICR-MS, nuclear magnetic resonance spectroscopy, three-dimensional fluorescence spectroscopy, and parallel factor analysis. The results demonstrate that YC-4 DOM exhibits rich chemical diversity, primarily composed of lignin/CRAM-like compounds (54.26%), tannins (16.75%) and proteins (13.43%). The predominant carbon forms in YC-4 DOM were aliphatic C-O bonded compounds (33.74%), aliphatic compounds (24.31%), and carboxylic acid compounds (23.95%). YC-4 DOM consists of five fluorescent components: marine-like humic substances, two types of humic-like substances, fulvic-like substances, and one protein-like substance. The fluorescence signature, characterized by high fluorescence index (FI 1.99), low humification index (HIX 0.66), and high biological index (BIX 1.27), collectively indicates that the DOM in Yuncheng Salt Lake brine is predominantly autochthonous, weakly humified, and highly bioavailable. This study reveals the DOM feature within the “human–environment coupled system” of Yuncheng Salt Lake. The findings provide a scientific basis for the sustainable utilization of its brine DOM resources and further enrich the theoretical system of DOM biogeochemical cycle in high-salinity lake system. Full article

(This article belongs to the Section Hydrology)

35 pages, 8072 KB

Open AccessArticle

Bioretention as an Effective Strategy to Mitigate Urban Catchment Loss of Retention Capacity Attributed to Land Use and Precipitation Patterns

by Krzysztof Muszyński

Water 2026, 18(2), 287; https://doi.org/10.3390/w18020287 - 22 Jan 2026

Abstract

This study provides a quantitative assessment of the combined effects of progressive urbanization and changes in precipitation patterns (PPs) on the urban water cycle. The primary objective was to evaluate historical (1940–2024) and projected (to 2060) changes in total annual surface runoff (TSR) [...] Read more.

This study provides a quantitative assessment of the combined effects of progressive urbanization and changes in precipitation patterns (PPs) on the urban water cycle. The primary objective was to evaluate historical (1940–2024) and projected (to 2060) changes in total annual surface runoff (TSR) and retention capacity (RC) in the highly urbanized catchment of the Dłubnia River in Cracow, Poland. Simulations were performed using the EPA SWMM hydrodynamic model, supported by digitized historical land-use maps and long-term meteorological records. The results demonstrate that the dominant driver of the observed 6.4-fold increase in TSR and 6.8-fold loss of retention capacity (LRC) over the study period was the progressive increase in impervious surfaces. Although inter-annual variability in the amount and structure of annual precipitation (AP) strongly correlates with annual TSR (r = 0.97), its contribution to the long-term upward trend in TSR is marginal (r = 0.19). Land use and land cover change (LULC) exhibits an extremely strong correlation with the long-term TSR trend (r = 0.998). The study also highlights the high effectiveness of nature-based solutions (NbSs), particularly bioretention cells (BCs)/rain gardens, in mitigating the adverse hydrological effects of excessive surface sealing. Implementation of BCs covering just 3–4% of the total drained roof and road area is sufficient to fully offset the projected combined negative impacts of further urbanization and climate change (CC) in scope Representative Concentration Pathways (RCP4.5 and RCP8.5) projections on catchment retention capacity by 2060. These findings position strategically targeted, relatively small-scale bioretention as one of the most effective and feasible urban adaptation measures in mature, densely developed cities. Full article

(This article belongs to the Special Issue Urban Water Management: Challenges and Prospects, 2nd Edition)

► Show Figures

Figure 1

24 pages, 780 KB

Open AccessReview

Beyond ‘Business as Usual’: A Research Agenda for the Operationalisation of Nature-Based Solutions in Flood Risk Management in The Netherlands

by Nicola Ann Harvey, Herman Kasper Gilissen and Marleen van Rijswick

Water 2026, 18(2), 286; https://doi.org/10.3390/w18020286 - 22 Jan 2026

Abstract

The Netherlands is widely recognised as the global leader in water management, with its flood risk management (FRM) infrastructure lauded as being of the best in the world. This status notwithstanding, Dutch FRM primarily maintains established infrastructural practices and experimental applications of NBSs [...] Read more.

The Netherlands is widely recognised as the global leader in water management, with its flood risk management (FRM) infrastructure lauded as being of the best in the world. This status notwithstanding, Dutch FRM primarily maintains established infrastructural practices and experimental applications of NBSs remain less frequent than established structural projects. This paper details and examines the challenges associated with the prevailing ‘business-as-usual’ approach to FRM in the Netherlands, in which traditional ‘grey’ infrastructural techniques are prioritised over innovative ‘green’ nature-based solutions (NBSs). In line with emerging international trends, such as the EU Water Resilience Strategy, NBSs are increasingly advocated as a strategic, complementary layer to enhance the resilience of existing safety frameworks rather than a self-evident replacement for them. Contrary to grey infrastructure, NBSs provide a number of environmental and social co-benefits extending beyond their flood and drought protection utility. The literature on NBSs details the design, effectiveness, and positive socio-economic impact of the operationalisation of such projects for FRM. This notwithstanding, the uptake and practical implementation of NBSs have been slow in the Netherlands. From a legal and policy perspective, this has been attributed to a lack of political will and the corresponding failure to include NBSs in long term FRM planning. Given the long planning horizons associated with FRM (50–100 years), the failure to incorporate NBSs can lead to policy lock-in that blocks future adaptations. Against this backdrop, this paper employs a semi-systematic literature review to clarify the obstacles to implementing NBSs in Dutch FRM and sets a research agenda that charts a course to mainstreaming NBSs in Dutch FRM. Seven core focus areas for future research are identified. The paper concludes by drawing on these identified focus areas to construct a research agenda aimed at systematically addressing each barrier to the practical operationalisation of NBSs in Dutch FRM, emphasising a hybrid green–grey approach which may serve to inspire similar research in other jurisdictions. Full article

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

46 pages, 9891 KB

Open AccessArticle

An Operational Streamflow Forecasting System for a Data-Scarce Catchment in Tanzania

by Preksedis Marco Ndomba and Ånund Killingtveit

Water 2026, 18(2), 285; https://doi.org/10.3390/w18020285 - 22 Jan 2026

Abstract

This paper reports the findings of the first initiative of developing a year-round streamflow forecasting system using the HBV hydrologic model in a data-scarce Ruvu catchment in Tanzania. Considering the importance of the Ruvu catchment as the main source of water to the [...] Read more.

This paper reports the findings of the first initiative of developing a year-round streamflow forecasting system using the HBV hydrologic model in a data-scarce Ruvu catchment in Tanzania. Considering the importance of the Ruvu catchment as the main source of water to the fast-growing mega city of Dar es Salaam, the researchers in this study made the most of the available data and their joint previous application experience of the modelling framework for the purpose of setting up a reliable operational model. In addition, the researchers adopted a phased approach of developing the streamflow forecasting system, using HBV as a hydrological model, which resulted in a simplified model structure with minimized complexity. For instance, the snow routine was removed as it is not relevant to the study area, and a few parameters were reduced to improve model efficiency. As a measure to demonstrate model performance, in addition to the Nash–Sutcliffe Efficiency (NSE) parameter used for model calibration and verification, several other error functions and graphical displays were used. The model performance values, as measured by NSE for calibration and verification periods, are 0.85 and 0.82 for Ruvu Roadbridge (1H8A), and 0.80 and 0.82 for Kidunda (1H3), respectively, and all are classified as “Very Good”. In addition, the PBIAS of less than ±5% in calibration indicates excellent water balance simulation. Furthermore, the forecast’s performance in this study is evidenced by an annual forecast R² of 0.933, with operational meteorological forecasts improving to 0.962 with “perfect” precipitation; dry season performance with R² of 0.964, demonstrating high skill in baseflow-dominated periods; and the PBIAS for forecasts of 0.866, indicating a slight systematic under-forecasting correctable by a ~15% precipitation adjustment. Although the Ruvu catchment has been characterized by this study as a data-scarce catchment, the results of the operational hydrological forecasting system vary with season and quality of forecast meteorological data, and the model is already launched for operational use. As evidenced by these study findings, the journey from data scarcity to operational forecast provision in the Ruvu catchment demonstrates that the principal barriers are fundamentally institutional and capacity-related. The authors suggest that any future forecasting initiative should put much emphasis on both the understanding of the modelling framework to be used and adequate data collection and analysis, in a synergetic manner with all relevant agencies. And it is also recommended to be vigilant regarding changes in the catchment characteristics and model performance during its life cycle, as the performance of the developed model is only valid under the condition that it was calibrated and validated. Full article

(This article belongs to the Section Hydrology)

► 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