Assessing the Applicability of the LTSF Algorithm for Streamflow Time Series Prediction: Case Studies of Dam Basins in South Korea

Journal Description

Water

Water is a peer-reviewed, open access journal on water science and technology, including the ecology and management of water resources, published semimonthly online by MDPI. Water collaborates with the Stockholm International Water Institute (SIWI). In addition, the American Institute of Hydrology (AIH), Polish Limnological Society (PLS) and Japanese Society of Physical Hydrology (JSPH) are affiliated with Water and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, GEOBASE, GeoRef, PubAg, AGRIS, CAPlus / SciFinder, Inspec, and other databases.
Journal Rank: JCR - Q2 (Water Resources) / CiteScore - Q1 (Aquatic Science)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 18.9 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Companion journals for Water include: GeoHazards.
Journal Clusters of Water Resources: Water, Journal of Marine Science and Engineering, Hydrology, Resources, Oceans, Limnological Review, Coasts.

Impact Factor: 3.0 (2024); 5-Year Impact Factor: 3.3 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2073-4441

Latest Articles

19 pages, 2575 KB

Open AccessArticle

Assessing Urban Flood Susceptibility Using Random Forest Machine Learning and Geospatial Technologies: Application to the Bonoumin-Palmeraie Watershed, Abidjan (Côte d’Ivoire)

by Jean Homian Danumah, Wilfred Ahoumodom Ataba, Valère Carin Jofack Sokeng, You Lucette Akpa, Mahaman Bachir Saley and Andrew Ogilvie

Water 2026, 18(3), 402; https://doi.org/10.3390/w18030402 (registering DOI) - 4 Feb 2026

Abstract

Recurrent flooding poses a persistent and growing threat to West African watersheds facing rapid urbanization and climate change. Despite advances in machine learning and geospatial datasets, urban planning and flood prevention often rely on limited datasets and traditional analysis. This study addresses this research gap in the Bonoumin-Palmeraie watershed (Abidjan, Côte d’Ivoire) by developing an integrated approach leveraging remote sensing, Geographic Information Systems (GIS), and the Random Forest algorithm to assess and map flood susceptibility. Twelve conditioning factors related to topography, hydrology, land use, and climate were derived from Sentinel-1, ALOS PALSAR, and multi-source earth observation datasets. Historical flood extents were mapped in Google Earth Engine to train the Random Forest model in a Google Colab environment. The model demonstrated high discriminatory power, yielding an Area Under the Curve of 0.94 and Overall Accuracy of 0.83. Drainage density, rainfall, and altitude were identified as the primary explanatory drivers. The resulting flood susceptibility map indicates that 39% of the watershed exhibits medium to very high susceptibility, with critical hotspots in the neighborhoods of Palmeraie, Attoban, Akouedo, Djorogobité, and Riviera-Sogefiha. While limited by the exclusion of certain anthropogenic variables and ground truth constraints, the study provides a reproducible, data-driven framework for flood risk assessment in tropical urban environments. These findings offer essential scientific support for urban planners and decision-makers to enhance territorial planning and sustainable flood management in Abidjan. Full article

(This article belongs to the Special Issue Advances in Hydroinformatics and Geo/Statistics for Modelling and Risk Assessment of Water Systems)

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4 pages, 136 KB

Open AccessEditorial

Geochemistry and Removal of Heavy Metals and Other Pollutants in Water

by Qiusheng Yuan and Xun Wang

Water 2026, 18(3), 401; https://doi.org/10.3390/w18030401 (registering DOI) - 4 Feb 2026

Abstract

Global water ecosystems are confronted with increasing pressure, characterized by sustained deterioration of water quality and diminishing availability of water resources, which have emerged as critical constraints on regional sustainable development [...] Full article

(This article belongs to the Special Issue Geochemistry and Removal of Heavy Metals and Other Pollutants in Water)

4 pages, 140 KB

Open AccessEditorial

Analysis of Extreme Precipitation Under Climate Change

by Xiaosheng Qin

Water 2026, 18(3), 400; https://doi.org/10.3390/w18030400 (registering DOI) - 4 Feb 2026

Abstract

The escalation in both frequency and magnitude of extreme precipitation events represents one of the most significant and immediate challenges posed by climate change [...] Full article

(This article belongs to the Special Issue Analysis of Extreme Precipitation Under Climate Change)

5 pages, 153 KB

Open AccessEditorial

Study on Environmental Hydrology and Hydrodynamic Characteristics of Basins, Estuaries and Offshore

by Biyun Guo

Water 2026, 18(3), 399; https://doi.org/10.3390/w18030399 (registering DOI) - 4 Feb 2026

Abstract

Freshwater from land flows into the ocean, mixing with saline water at the land–sea interface to form estuarine and adjacent nearshore ecosystems—one of the most productive and biologically active critical ecological zones [...] Full article

(This article belongs to the Special Issue Study on Environmental Hydrology and Hydrodynamic Characteristics of Basins, Estuaries and Offshore)

28 pages, 1025 KB

Open AccessReview

Green Roofs in Southern Europe: Assessing Native Vegetation Suitability While Tackling Water Management Strategies

by Teresa A. Paço

Water 2026, 18(3), 398; https://doi.org/10.3390/w18030398 - 3 Feb 2026

Abstract

Green roofs in Southern Europe are interest-growing nature-based solutions, capable of improving urban sustainability by positively impacting the water cycle, biodiversity, pollution, and, in some cases, energy consumption and carbon sequestration. Native plants adapted to Mediterranean climates exhibit drought-resistant traits, making them highly suitable for the challenging microclimate of green roofs. This microclimate features intense solar radiation, strong winds, and higher temperatures, in comparison to ground level, leading to increased atmospheric evaporative demand, driven by the interplay of radiation, wind, temperature, and humidity. Consequently, native plants from ecosystems resembling this microclimate are likely better suited for green roofs than local ground-level species. The current review synthesizes current knowledge on the use of native plants in Southern European green roofs, focusing on water management challenges given the region’s climate and scarce water resources. Out of roughly 12,500 native plant species in the Mediterranean basin, only about 124 have been examined in the past 20 years for green roof applications, with just 16% appearing in multiple scientific studies, highlighting a significant knowledge gap. The data indicate that ca. 85% of these species are perennials, valued for their low maintenance needs, a key consideration for green roof sustainability. Some of the studied species retain adequate aesthetic value when cultivated on green roofs with limited water availability. These species are mainly associated with four habitat types—rocky, coastal, dry, or well-drained environments—with a few linked to humid or adaptable conditions. This study aims to document the selection of drought-adapted native plant species best suited for green roof implementation in Southern Europe, contributing to enhancing sustainable urban design in the region, considering water management best practices and water use efficiency. Full article

(This article belongs to the Section Urban Water Management)

35 pages, 7867 KB

Open AccessArticle

Inter-Comparison of Deep Learning Models for Flood Forecasting in Ethiopia’s Upper Awash Basin

by Girma Moges Mengistu, Addisu G. Semie, Gulilat T. Diro, Natei Ermias Benti, Emiola O. Gbobaniyi and Yonas Mersha

Water 2026, 18(3), 397; https://doi.org/10.3390/w18030397 - 3 Feb 2026

Abstract

Flood events driven by climate variability and change pose significant risks for socio-economic activities in the Awash Basin, necessitating advanced forecasting tools. This study benchmarks five deep learning (DL) architectures, Convolutional Neural Network (CNN), Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU), Bidirectional LSTM (BiLSTM), and a Hybrid CNN–LSTM, for daily discharge forecasting for the Hombole catchment in the Upper Awash Basin (UAB) using 40 years of hydrometeorological observations (1981–2020). Rainfall, lagged discharge, and seasonal indicators were used as predictors. Model performance was evaluated against two baseline approaches, a conceptual HBV rainfall–runoff model as well as a climatology, using standard and hydrological metrics. Of the two baselines (climatology and HBV), the climatology showed limited skill with large bias and negative NSE, whereas the HBV model achieved moderate skill (NSE = 0.64 and KGE = 0.82). In contrast, all DL models substantially improved predictive performance, achieving test NSE values above 0.83 and low overall bias. Among them, the Hybrid CNN–LSTM provided the most balanced performance, combining local temporal feature extraction with long-term memory and yielding stable efficiency (NSE ≈ 0.84, KGE ≈ 0.90, and PBIAS ≈ −2%) across flow regimes. The LSTM and GRU models performed comparably, offering strong temporal learning and robust daily predictions, while BiLSTM improved flood timing through bidirectional sequence modeling. The CNN captured short-term variability effectively but showed weaker representation of extreme peaks. Analysis of peak-flow metrics revealed systematic underestimation of extreme discharge magnitudes across all models. However, a post-processing flow-regime classification based on discharge quantiles demonstrated high extreme-event detection skill, with deep learning models exceeding 89% accuracy in identifying extreme-flow occurrences on the test set. These findings indicate that, while magnitude errors remain for rare floods, DL models reliably discriminate flood regimes relevant for early warning. Overall, the results show that deep learning models provide clear improvements over climatology and conceptual baselines for daily streamflow forecasting in the UAB, while highlighting remaining challenges in peak-flow magnitude prediction. The study indicates promising results for the integration of deep learning methods into flood early-warning workflows; however, these results could be further improved by adopting a probabilistic forecasting framework that accounts for model uncertainty. Full article

(This article belongs to the Section Hydrology)

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35 pages, 9430 KB

Open AccessArticle

Biofilms, Groundwater Seepage, and Internal Controls on Dry-Weather Bacterial Loading in Underground Storm Drains

by Barry J. Hibbs and Carol Peralta

Water 2026, 18(3), 396; https://doi.org/10.3390/w18030396 - 3 Feb 2026

Abstract

Bacterial sourcing in urban watersheds is a critical water quality concern because elevated index bacteria concentrations routinely trigger beach advisories and closures in coastal Southern California and elsewhere. This study evaluates diurnal controls on dry-weather bacterial loading in a groundwater-fed storm drain within the Malibu Creek watershed using a 24 h monitoring campaign. Discharge, nutrients, major ions, stable water isotopes, and index bacteria (total coliforms and Escherichia coli) were measured at six time intervals. Storm drain discharge varied by more than an order of magnitude, with rapid nighttime increases of up to +91 L/min during irrigation periods. Total Dissolved Solids ranged from 1276 to 2175 mg/L, peaking during groundwater-dominated low-flow conditions. Nitrate–N ranged from 1.08 to 2.96 mg/L, and orthophosphate from 0.44 to 2.16 mg/L, with nutrient concentrations increasing as irrigation inputs increased. Total coliform concentrations ranged from 13,000 to 670,000 MPN/100 mL, and E. coli ranged from 300 to 120,000 MPN/100 mL, exceeding concentrations in tap water and recycled water runoff by up to two orders of magnitude. End member mixing analysis showed that storm drain flow consisted of approximately 45% groundwater, 23–26% tap water, and 30–33% recycled water during early morning peak flow, shifting to ~56% groundwater and <12% recycled water by mid-morning. The lowest bacterial concentrations occurred during groundwater-only flow, while the largest bacterial increases coincided with the greatest positive changes in discharge rather than with maximum absolute flow. These results support an irrigation-driven biofilm stripping mechanism as the dominant control on dry-weather bacterial loading, with groundwater seepage sustaining biofilm persistence but not peak bacterial release. The findings highlight the importance of internal storm drain processes for managing coastal bacterial exceedances and protecting beach health. Full article

(This article belongs to the Section Hydrogeology)

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24 pages, 2992 KB

Open AccessArticle

Tributary-to-Mainstream Aquatic Macroinvertebrate Discontinuities in the Colorado River, Southwestern USA

by Lawrence E. Stevens, Joseph H. Holway and Craig Ellsworth

Water 2026, 18(3), 395; https://doi.org/10.3390/w18030395 - 3 Feb 2026

Abstract

Tributary-to-mainstem discontinuities (TMDs) are understudied, but are likely common in river networks, arising from abrupt transitions in stream order and dominant ecological factors. We present a conceptual model of aquatic macroinvertebrate (AMI) TMD directionality and relative magnitude by contrasting the impacts of hydrography, geochemistry, and sediment transport on tributary-related channel-floor precipitate cementation and the mainstream embeddedness (burial) of channel-floor substrata in fine sediment. We test that model using AMI assemblage density/m², species richness/sample, and diversity data from 24 tributaries confluent with the regulated Colorado River in Grand Canyon through pairwise and multivariate analyses of long-term discharge records and substrate and water-quality data in three habitats: tributaries, their confluences, and adjacent mainstream habitats. Mean AMI density decreased 2.7-fold from low to high cementation, 6.1-fold from low-to-high embeddedness, and 136.0-fold across combined gradients. We also analyzed pre-dam aquatic insect literature, finding that TMDs were naturally common in Glen Canyon upstream but were more strongly tributary-positive (discontinuity magnitude, D_mag = 0.62 in pre-dam Glen Canyon) compared to tributaries in the post-dam Grand Canyon (D_mag = 0.31). We conclude that, depending on D_mag directionality, tributary confluences can function as hotspots or barriers to AMI assemblage development. Our results demonstrate that TMDs are and were common in the contemporary regulated and natural unregulated Colorado River corridor, and we expand the concept of biotic discontinuity to improve understanding of fluvial ecosystem ecology and constraints on river and dam management. Full article

(This article belongs to the Special Issue Freshwater Ecosystems—Biodiversity and Protection: 2nd Edition)

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18 pages, 1490 KB

Open AccessArticle

Closing the Nutrient Loop Through Multi-Cycle Phototrophic Reuse of Landfill Leachate in Cyanobacterial PHB Bioproduction

by Antonio Zuorro, Jessica Ximena Pedreros-Sánchez, Roberto Lavecchia, Maria D. Ortiz-Alvarez, Janet B. García-Martínez and Andrés F. Barajas-Solano

Water 2026, 18(3), 394; https://doi.org/10.3390/w18030394 - 3 Feb 2026

Abstract

This study investigated a phototrophic approach to close nutrient loops by using landfill leachate as a culture medium to produce biomass and polyhydroxybutyrate (PHB) from a thermotolerant strain of Potamosiphon sp. A multi-cycle reuse scheme in which post-culture leachate was partially replenished with fresh leachate and reused in successive cultivation rounds to increase the biomass concentration (g/L) and the intracellular PHB content (% w/w) was tested. Three operational variables were optimized (leachate replenishment percentage, number of reuse cycles, and sanitation method (autoclaving, UV irradiation, or no treatment)) via the Box–Behnken response surface method. Both response variables were modeled with high predictive accuracy (R² = 0.98 for biomass and R² = 1.00 for PHB content). According to the experimental data, leachate replenishment emerged as the key factor influencing nutrient availability—particularly nitrogen and phosphorus—and thus PHB accumulation. The optimized conditions (2.17% v/v fresh leachate, three reuse cycles, and UV sanitation) yielded predicted values of 0.29 g/L biomass and 3.48% w/w PHB. These results demonstrate the feasibility of a controlled multicycle reuse process that integrates effluent treatment and biopolymer synthesis, offering a low-input, circular biotechnological approach for sustainable leachate valorization. Full article

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

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19 pages, 5065 KB

Open AccessArticle

Energy Dissipation Rate and Conjugate Depth After Hydraulic Jump for Counterflow Underflow Energy Dissipation in Spillways

by Shiyong Zhao, Huanmin Zhang, Qin Zhao, Gengsheng Nie, Zhengqing Deng and Gang Yu

Water 2026, 18(3), 393; https://doi.org/10.3390/w18030393 - 3 Feb 2026

Abstract

To address the energy dissipation requirements of hydraulic engineering projects with medium-low water heads and medium-high unit discharges, counterflow-type underflow energy dissipation can significantly enhance the energy dissipation efficiency through the head-on collision of flows from spillways on both sides. In this study, the spillway of the Lieshen Reservoir was used as the prototype. Since gravity dominates the flow in spillways, we established a 1:15 physical model based on the Froude similarity criterion, and conducted numerical simulations using the volume of fluid method coupled with the realizable k-ε turbulence model. Furthermore, the hydraulic characteristics of counterflow energy dissipation under different flow rates and stilling basin length conditions were analyzed. The results show that the counterflow energy dissipation rate first increases before decreasing with increasing stilling basin length, and the maximum energy dissipation rate can exceed 85%; however, the change in the stilling basin depth has a small impact on the energy dissipation rate, especially under relatively high flow rates; furthermore, an empirical formula for the conjugate depth after a hydraulic jump suitable for counterflow energy dissipation with Froude number in the range of 2.0 < Fr₁ < 9.7 and stilling basin depth of 0.5–1.5 m is proposed, with the relative error between its predicted and simulated values being less than 6%. Based on the analysis of the water depth outer envelope curve at the outlet section of the stilling basin, it is suggested that the sidewall height be set to 0.6–0.8 times the conjugate depth after the hydraulic jump. Full article

(This article belongs to the Topic Hydraulic Engineering and Modelling)

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5 pages, 150 KB

Open AccessEditorial

Research Advances in Hydraulic Structure and Geotechnical Engineering

by Xiang Yu, Yuke Wang and Yongqian Qu

Water 2026, 18(3), 392; https://doi.org/10.3390/w18030392 - 3 Feb 2026

Abstract

The escalating global energy demand coupled with accelerating low-carbon transitions has intensified focus on hydro energy resources as a renewable clean energy source [...] Full article

(This article belongs to the Special Issue Research Advances in Hydraulic Structure and Geotechnical Engineering)

28 pages, 10120 KB

Open AccessArticle

Change in the Intensity of Soil Erosion via Water in the Vistula River Basin in Future Climate: A Comparison of the RCP 4.5 and RCP 8.5 Scenarios (2021–2050) Using the MUSLE Model

by Damian Badora, Rafał Wawer, Aleksandra Król-Badziak, Beata Bartosiewicz and Jerzy Kozyra

Water 2026, 18(3), 391; https://doi.org/10.3390/w18030391 - 3 Feb 2026

Abstract

This study aims to assess how climate change will affect the intensity of soil erosion in the Vistula River basin by the mid-21st century. A simulation framework based on the SWAT–MUSLE model was applied, calibrated, and validated against observed streamflow data and driven by climatic forcings from the EURO-CORDEX ensemble (the RACMO22E, HIRHAM5, and RCA4 models forced by EC-EARTH GCM) under the RCP 4.5 and RCP 8.5 scenarios. Simulations were conducted at a daily time step for the years 2021–2050 and compared to the reference period 2013–2018. The analysis included the decadal and seasonal aggregation of the sediment yield (SYLD, t ha⁻¹ yr⁻¹). The results indicate that, relative to the baseline value (~1.84 t ha⁻¹ yr⁻¹), the SYLD increases under both scenarios. In RCP 4.5, the rise culminates during 2031–2040 and then stabilizes in 2041–2050. Under RCP 8.5, a continuous upward trend is observed, with the highest values projected for 2041–2050, particularly for the HIRHAM5 realization. The largest relative increases occur in summer (JJA) and, in the final decade, also in autumn (SON); in the early horizon, autumn may locally exhibit declines that later shift to increases. The spread among RCM realizations remains significant and should be interpreted as an expression of projection uncertainty. The practical implications include prioritizing soil protection measures in sub-catchments with high LS factors and soils susceptible to water erosion, strengthening runoff and sediment control in summer, and planning maintenance of small-scale retention infrastructure. Study limitations arise from the inherent structure of the MUSLE model, bias correction procedures for climate data, and the representation of extreme events. Therefore, greater emphasis is placed on the direction and seasonality of changes rather than absolute numerical values. Full article

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

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14 pages, 1637 KB

Open AccessArticle

Hydraulic Performance of a Box Culvert-Type Two-Way Channel Pumping System: An Experimental Study

by Pu Xu, Lingyu Li and Weixuan Jiao

Water 2026, 18(3), 390; https://doi.org/10.3390/w18030390 - 3 Feb 2026

Abstract

With the increasing application of box culvert-type two-way channel pumping systems in low-head pumping stations along rivers in China, a comprehensive investigation of their hydraulic performance is of significant importance. In this study, a physical model test was conducted on a box culvert-type two-way channel pumping station located along the Yangtze River. The energy performance, cavitation characteristics, runaway characteristics, and pressure pulsation behavior of the pumping system were systematically examined. The experimental results indicate that the pumping system achieves optimal energy performance when the blade installation angle is −2°, under which the maximum system efficiency reaches 68.0% while satisfying the operational requirements across different head conditions. For a given blade angle, the critical cavitation margin of the pumping system initially decreases and subsequently increases as the head decreases. At the same head, the critical cavitation margin increases with increasing blade installation angle. Furthermore, the unit runaway speed of the pumping system increases as the blade angle decreases. The blade installation angle significantly influences the amplitude of pressure pulsations at the impeller, whereas its effect on the dominant frequency is relatively minor. The overall pressure pulsation amplitudes measured at the impeller are less than 0.20 m. These findings provide valuable experimental insights for the hydraulic optimization design and operational regulation of similar pumping stations, contributing to improved operational efficiency and reliability while reducing operating costs. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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20 pages, 6085 KB

Open AccessArticle

A Novel Weather Generator and Soil Attribute Database for SWAT to Improve the Simulation Accuracy in the Heilongjiang Region of China

by Zhihao Zhang, Haorui Zhang, Xiaoying Yu, Chunyan Yang and Tong Zheng

Water 2026, 18(3), 389; https://doi.org/10.3390/w18030389 - 3 Feb 2026

Abstract

This study addresses the issue of missing basic data and insufficient accuracy in predicting runoff and non-point-source pollution in the Heilongjiang region of China using the Soil and Water Assessment Tool (SWAT) model. Based on the China Ground Climate Data Daily Dataset (V3.0) and SPAW soil characteristic calculation formula, and assisted by the Python V3.0 language for data processing and computation, new high-precision weather generators and soil attribute databases suitable for the Heilongjiang region of China were established. The weather generator is based on daily data and contains detailed meteorological parameters such as temperature, humidity, wind speed, rainfall, etc., used to characterize the periodic changes in meteorological elements. And the differences and fluctuations outside this change curve were also retained in the basic construction of the weather generator. The soil database covers various parameters, such as soil type, texture, structure, nutrient content, organic matter content, etc., enabling the SWAT model to better simulate hydrological and pollutant transport processes in the soil. Additionally, point-source input data, including various industrial and domestic wastewater discharge situations, were collected and organized to improve data quality. Furthermore, a series of agricultural management measures were developed based on the use of fertilizers and pesticides for simulation, providing an important basis for analyzing non-point-source pollution using the SWAT model. By comparing the different results of the simulation using optimized databases, it is shown that the above work improved the simulation accuracy of the SWAT model in predicting runoff and pollution load in Heilongjiang, China. The NSE of runoff simulation increased from 0.923 to 0.988, and the NSE of ammonia nitrogen and CBOD simulation increased from 0.852 and 0.758 to 0.930 and 0.902, respectively. It is expected that these efforts will provide strong data support for subsequent research and provide a theoretical basis for government decision-makers to build scientifically rigorous and effective pollution control strategies. Full article

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

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4 pages, 134 KB

Open AccessEditorial

Enhancing Planning in the Management of Urban Water Systems to Increase Resilience

by Dália Loureiro and Maria Adriana Cardoso

Water 2026, 18(3), 388; https://doi.org/10.3390/w18030388 - 3 Feb 2026

Abstract

Urban water infrastructures are vital to cities, yet they are complex and vulnerable to both climate-related events—such as extreme precipitation, urban floods, droughts, heat waves, and cyclones—and other disruptive events like earthquakes, tidal effects, and tsunamis [...] Full article

(This article belongs to the Special Issue Enhancing Planning in the Management Urban Water Systems to Increase Resilience)

28 pages, 5224 KB

Open AccessArticle

Systematic Updates on the Caridina serratirostris De Man, 1892, Species Group and the Genus Marosina Cai & Ng, 2005 (Crustacea, Decapoda, Atyidae)

by Yixiong Cai

Water 2026, 18(3), 387; https://doi.org/10.3390/w18030387 - 2 Feb 2026

Abstract

During a taxonomic revision on Caridina of East and Southeast Asia, a group of amphidromous and anchialine Caridina species, i.e., Caridina serratirostris, C. celebensis, C. rubella, C. troglodytes, C. magnovis, C. rintelenorum, and C. henriettae, widely distributed in the Indo-Pacific region has been found to exhibit distinct and unique morphological characters, e.g., rostra moderately long and straight, armed with many dorsal teeth, at least six of them on the carapace; telson terminating in a posteromedian projection; stylocerite long, reaching to or beyond the end of the basal segment of the antennular peduncle; and preanal carina with a spine, and with slender walking legs. Genetically, the group forms a monophyletic clade, either alone or together with the genus Marosina. The clade is well-separated from other species/species groups of Caridina. By taking a conservative taxonomic approach, the genus Marosina is thus redefined to accommodate members of the C. serratirostris species group. The revised genus Marosina can be separated from the typical Caridina species (represented by Caridina typus species group) by the structure of the endopod of the male first pleopod, which does not have an appendix interna, and the long stylocerite, which reaches to or beyond the end of the basal segment of the antennular peduncle, and the high number of postorbital teeth on the carapace. The paper provides a revised diagnosis of Marosina, with a key to all species assigned to it. Diagnosis, taxonomic remarks, habitat, and distribution information for all species are provided. The ecology, biogeography, and conservation of the genus are briefly discussed. Full article

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

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20 pages, 1671 KB

Open AccessArticle

Spatiotemporal Characteristics of Water Quality in Qiantang River Basin: An Analysis Based on the WQI Model and Multivariate Statistics

by Wen Luo, Danxia Liu, Jing Chen and Jing Cheng

Water 2026, 18(3), 386; https://doi.org/10.3390/w18030386 - 2 Feb 2026

Abstract

Global river water quality degradation severely impairs aquatic ecosystem stability and human health, highlighting the urgency of spatiotemporal analysis for management guidance. Based on 2014–2024 monitoring data from the Quzhou Section of Qiantang River Basin, this study adopted the Water Quality Index (WQI) and statistical methods (PCA, Mann–Kendall test) to explore the spatiotemporal characteristics of water quality across the basin. Results showed an overall mean WQI of 79.26 (classified as “Good”), with general stability, localized fluctuations, and a stable-then-declining trend, mirroring an imbalance between governance effects and emerging pollution pressures. It identifies a critical governance phase focused on securing the current good water quality and curbing the trend of further deterioration. Water quality exhibited distinct variations: upper reaches > lower reaches, tributaries > mainstreams, with priority required for the Wuxi River’s declining WQI and the Qu River’s persistently low WQI. TN, TP, and NH₃-N were identified as key factors coupled with land use patterns. A differentiated strategy prioritizing nitrogen control, synergizing phosphorus–oxygen management, and reducing organics is thus proposed. This study provides scientific references for water quality assessment and targeted aquatic ecological governance in the basin and similar river networks. Full article

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

16 pages, 2836 KB

Open AccessArticle

Experimental Study on the Influence of Sand Dune Morphology on Near-Bed Flow Structure

by Shan Li, Zhongwu Jin and Xiaohu Guo

Water 2026, 18(3), 385; https://doi.org/10.3390/w18030385 - 2 Feb 2026

Abstract

Riverbed topography in natural rivers commonly features sand dunes, whose morphological variations can alter the turbulent flow structure near the bed and thereby affect processes of channel scour, deposition, and sediment transport. In this study, a series of flume experiments was conducted using an acoustic Doppler velocimeter (ADV) to simulate fixed bedforms of different dune scales (ratio of wavelength to flow depth, λ/h) in a laboratory flume. Velocity measurements were taken along the water depth at the dune crest and trough for each test case. The near-bed distributions of mean flow velocity, Reynolds stress, turbulent kinetic energy (TKE), and turbulence intensity were obtained at the crest and trough under three flow conditions, allowing analysis of the vertical decay of turbulence intensity at different locations on the dune. The results show that the dune steepness (Ψ, defined as dune height over wavelength) is a key parameter controlling the near-bed flow structure. As Ψ increases, the near-bed velocity gradient, Reynolds stress, TKE, and peak turbulence intensity all increase significantly, with the peak positions shifting closer to the bed. The trough region, due to flow separation and vortex shedding, exhibits substantially higher values of all turbulence-related parameters than the crest, making it the primary zone of energy dissipation and turbulence production. This study provides experimental evidence and theoretical reference for understanding the mechanism by which sand dune morphology influences flow structure, and it offers insight for predicting riverbed evolution. Full article

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

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24 pages, 4932 KB

Open AccessArticle

Optimization and Performance Modeling of Constructed Wetlands for the Treatment of Slaughterhouse Effluents in Tropical Zones Using Response Surface Methodology

by Jesús Castellanos-Rivera, Alex Elías Álvarez Month, Cindy Carolina Contreras-Castro, Jorge Figueroa, Mayerlin Sandoval-Herazo, Oscar Marín-Peña and Luis Carlos Sandoval Herazo

Water 2026, 18(3), 384; https://doi.org/10.3390/w18030384 - 2 Feb 2026

Abstract

The meat industry generates wastewater with high organic matter loads, posing a significant environmental risk if not properly treated. The present study evaluated the performance of a horizontal subsurface flow constructed wetland (HSSF-CW) treating slaughterhouse effluents characterized by high-strength influent concentrations of 3570.51 ± 153.82 mg/L COD, 2114.33 ± 104.58 mg/L BOD₅, and 1173.77 ± 96.95 mg/L TOC. Furthermore, Response Surface Methodology (RSM) was employed to model and optimize the operational parameters. The independent variables considered were hydraulic retention time (HRT: 3, 5, and 10 days) and vegetation type (Heliconia latispatha, Typha latifolia, and polyculture). The results demonstrated a statistically significant improvement in treatment efficiency, achieving maximum removal efficiencies of 86.5% for COD, 89.4% for BOD₅, and 91.5% for TOC. The statistical models exhibited high accuracy (R² ≥ 0.996, p < 0.001). Adjusted response surface equations identified the polyculture with a 5-day HRT as the most favorable operational scenario. These findings confirm that properly designed and operated constructed wetlands represent a viable and sustainable alternative for treating high-load agro-industrial effluents, contributing to the protection of receiving water bodies. Future research should focus on full-scale studies and the inclusion of critical parameters such as nutrients and pathogens for a more comprehensive system characterization. Full article

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

18 pages, 3742 KB

Open AccessBrief Report

How Important Is Solid Phase PFAS Release from Legacy Coastal Landfills to the Water Environment?

by William M. Mayes, Sebastian J. Pitman, Alex L. Riley, Patrick A. Byrne, Ashley Lily, Adam P. Jarvis, Karen A. Hudson-Edwards and Ian T. Burke

Water 2026, 18(3), 383; https://doi.org/10.3390/w18030383 - 2 Feb 2026

Abstract

Historical landfills in coastal environments are at increasing risk of erosion under changing climate conditions. Various studies have highlighted pollutant release associated with potentially toxic elements and flame retardants from such erosional processes, but there has been little focus on per- and poly-fluoroalkyl substance (PFAS) release as a result of physical erosion at such sites, despite landfills being highlighted as a key source of PFAS to the water environment. This study presents a rapid screening approach that could be adopted at scale by regulators to assess the presence and potential flux of PFAS released at three historical municipal waste landfill sites in the UK. The sites selected cover a range of epochs prior to rigorous environmental regulation from the second half of the twentieth century. At the older waste deposits (Withernsea: 1950s–1960s; Hessle: 1930s–1970s), all 52 PFAS analysed in solid materials were below the detection limits except for two samples where modest concentrations (0.92–1.98 ng/g) of perfluorooctane sulfonate (PFOS) and perfluoroethylcyclohexane sulfonate (PFecHS) were detected. At the more recently operational site (Crosby: 1970s–1980s), the legacy PFAS chemicals, PFOS and perfluorooctanoic acid (PFOA), were present in all samples in modest concentrations (6.01–8.22 ng/g for PFOS; 0.62–1.20ng/g for PFOA) below contaminated land thresholds. At this site, it was possible to model the flux of PFAS release based on LiDAR surveys of the eroding waste terrace over an 18-year period. This showed an annualised total solid phase PFAS (PFOS plus PFOA in this case) flux in the region of 2.5–16.9 g/yr, which is towards the lower end of the reported landfill leachate flux at inland sites. While such releases are relatively modest on an individual site basis, in transitional and coastal waters in heavily urbanised and (post-)industrial regions, the aggregated solid phase PFAS flux from the large number of eroding historical landfills (n = 114) could be significant. Full article

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

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