Water doi: 10.3390/w18131574

Authors: Jun Ma Hui Huang Defu Liu Ying Liu Yaqian Xu

River water temperature connects hydrodynamic processes, air–water heat exchange, and aquatic ecological responses. Although data-driven models are increasingly used for short-term water-temperature forecasting, input-variable choice still influences both predictive skill and the interpretation of model errors. This study examined daily water-temperature forecasting at nine hydrological stations in the upper and middle reaches of the Yangtze River. The stations were grouped according to natural hydro-meteorological background, reservoir regulation, and compound disturbance. Based on surface-water heat balance and order-of-magnitude analysis, antecedent water temperature, air temperature, and discharge were selected as process-related candidate inputs and tested using LSTM and xLSTM models. The experiments considered input-window length, learning rate, batch size, and the inclusion of discharge. Under the no-discharge scheme, learning rate had the clearest effect on the predicted water-temperature series. For LSTM, the median predicted-temperature differences caused by changes in window length, learning rate, and batch size were 0.055, 0.077, and 0.056 °C, respectively; the corresponding values for xLSTM were 0.089, 0.102, and 0.073 °C. One-day-ahead forecasts for the selected representative dates produced mean RMSE values of 0.160 °C for LSTM and 0.165 °C for xLSTM, compared with 0.183 °C for a persistence baseline. The reservoir regulation impact group showed the lowest errors, whereas the compound disturbance impact group had higher errors and clear within-group differences. The contribution of discharge varied among stations and models: for LSTM, RMSE decreased at Batang, Panzhihua, and Huanglingmiao, but increased or changed little at Gangtuo, Yichang, and Cuntan; for xLSTM, the average RMSE did not decrease after discharge was added at the seven stations with discharge data. xLSTM showed local advantages at Huanglingmiao and Cuntan. These findings show that process-informed input selection offers a consistent basis for comparing multi-site water-temperature forecasts and for interpreting error differences among stations and input schemes.

Water doi: 10.3390/w18131573

Authors: Jose F. Martinez Mario Beruvides Clifford Fedler

The growing expectation of citizens to deliver quality services without increasing taxes requires municipalities to adjust their cost models to remain good stewards of the voters’ finances. Cost-of-Quality (CoQ) models have traditionally been studied in relation to manufacturing processes as a method to increase profitability by reducing the life-cycle costs of the product. Municipalities have historically not been included in these studies as they operate on a semi-monopolistic basis for the services and infrastructure they maintain and have a different set of constraints and obligations from private entities. An analysis of three North Carolina municipalities (Winston-Salem, Cary, and Apex) is conducted to evaluate the Cost-of-Quality components of their water system budgets. The analysis consists of two evaluations. The initial evaluation compares the budgets of the aforementioned North Carolina municipalities with a previous study that analyzed three Texas municipalities’ water system budgets (Lubbock, San Antonio, and El Paso). The purpose of this portion of the study is to evaluate whether North Carolina Cost-of-Quality components behave like Texas municipalities. The second portion of this study evaluates the three North Carolina municipalities independently of the Texas study to see whether population size is a differentiator in how Cost-of-Quality components are divided in North Carolina. The three NC municipalities are chosen based on the Hickory Municipal Classification System (MCS). The Hickory MCS is a national classification system based on the relative population of each state and was developed for this study. The Texas municipalities that were studied had variable populations, variable locations, variable water sources, and variable water uses. The Cost-of-Quality analysis focuses on prevention costs, appraisal costs, failure costs, Total CoQ costs and opportunity costs between the North Carolina and Texas municipalities. Of the twelve comparative hypotheses, three CoQ costs are found to be significantly different with a probability level of p < 0.05. The results suggest that appraisal and failure costs are consistently impactful across the utilities in both states, but opportunity costs are not materially significantly different as in previous studies on Cost of Quality for utilities.

Water doi: 10.3390/w18131572

Authors: Yang Lu Qinghua Xiao Zhongmin Fu Fei Chen Tengyu Jiang

To mitigate the negative impacts of traditional rigid revetments on river ecosystems, this study focuses on perforated plate grid revetments, aiming to reveal the hydrodynamic mechanisms and parameter collaborative optimization pathways that simultaneously achieve anti-scour stability and ecological water exchange. A series of flume scour tests were conducted, combined with high-resolution large eddy simulation (LES) validated by experimental data, to systematically analyze the regulatory effects of key design parameters—such as opening ratio and longitudinal offset angle—on near-bottom flow velocity attenuation, vortex structures, and water exchange efficiency. The results indicate that a prototype parameter combination of 0.25 m grid height and 0.50 m plate grid spacing can reduce local scour depth by about 30% and enhance vertical exchange through the synergy of jetting from the openings and internal vortices. The longitudinal offset of adjacent holes may enhance the transverse water exchange but may also significantly reduce the longitudinal exchange intensity; hence, further research is needed. A hole-to-baffle height ratio greater than 0.40 is identified as a critical threshold for improving exchange efficiency. This study proposes a collaborative design framework in which grid spacing controls scour safety and aperture parameters regulate exchange functions, providing an experimental basis for the precise design and performance enhancement of ecological revetments.

Water doi: 10.3390/w18131570

Authors: Alicia C. Díaz-Osorio Juan J. Schmitter-Soto Alfonso Aguilar-Perera Jesús A. Ruiz-Valencia

Decadal changes in the community structure of coral reef-associated fishes reflect prevailing poor environmental conditions. This study analyzed temporal shifts in fish communities (e.g., diversity, density, and biomass) recorded via SCUBA belt transects across coral reefs on the center–southern coast of Quintana Roo (eastern Yucatan Peninsula) in the Mexican Caribbean. Sites were initially investigated in 1995 and revisited in 2024 after the construction of a cruise ship pier, and we compared sites under different protection categories. Mean density and biomass decreased significantly over time, particularly at reef sites outside of a protected area in 1995. While species richness and density of commercially important fishes were higher in protected sites in 1995, parrotfishes (Scarinae) maintained stable density and biomass across both years and protection status. No significant differences were found in the biomass of other fishes (e.g., Haemulidae, Lutjanidae). Changes recorded may reflect historical fishing pressure, including poaching, but probably also pollution from intense growth of coastal tourism infrastructure in 2024, as well as damage from the beached Sargassum influx. Ultimately, the positive effect offered by protected areas is not enough to mitigate the local and regional environmental impacts on coral reefs. Our findings serve as a reference point where coastal development and climate change interact and affect coral reefs.

Water doi: 10.3390/w18131571

Authors: Songsak Muangnoi Passakorn Pananont Ladda Tangwattananukul Pongsakorn Jiwapornkupt Panu Trivej Schradh Saenton Chanai Rinkaew Pee Poatprommanee Somruedee Sakkaravej

Groundwater is an important resource for domestic, agricultural, and ecological use in the Surat Thani basin, southern Thailand, where increasing demand from agriculture, urbanization, and tourism is placing pressure on aquifer systems. This study investigates groundwater recharge and basin-scale flow dynamics using integrated numerical groundwater modeling, stable isotope analysis, and hydrochemical interpretation. A three-layer MODFLOW model representing floodplain (Qfd), terrace (Qt), and semi-consolidated aquifers was calibrated for 2018–2024 using PEST with pilot-point parameterization. Despite there being only four observation wells, the model achieved excellent agreement between simulated and observed heads (weighted RMSE = 0.0707 m). Simulated groundwater generally flows from western uplands toward the central floodplain and eastern coastal plain, with the Tapee River acting mainly as a gaining stream. Recharge rates range from 1.2 to 77.3 mm/yr (mean 23.7 mm/yr), representing only 1–4% of annual precipitation, while evapotranspiration is the dominant form of water loss. Stable isotope signatures (δ2H, δ18O) indicate recharge from direct monsoonal rainfall with minimal evaporation. Hydrochemical facies evolve from Ca–HCO3 recharge waters to mixed facies along downgradient flow paths, reflecting increasing residence time and water–rock interaction. The results identify western and northern upland areas as key recharge zones requiring long-term protection and sustainable groundwater management.

Water doi: 10.3390/w18131569

Authors: Zhuan Hao Di Wang Fengwei Xu Xiaohui Sun Li Tang

Natural lakes in urbanizing regions face compounding climatic and anthropogenic pressures. Despite their socio-ecological importance, the dual vulnerability of these urban lakes to both long-term areal shrinkage and the shifting frequencies of extreme water events remains a critical research gap, often overlooked in favor of large, remote lake systems. We investigated surface area dynamics, extreme events, and climatic attribution of 7320 natural lakes across China’s five major urban agglomerations (Jing-Jin-Ji, Yangtze River Delta, Greater Bay Area, Chengdu-Chongqing, and Middle Yangtze) from 2001 to 2023. Using a satellite area product, we assessed long-term trends via Seasonal-Trend decomposition by Loess (STL). Regional climate shifts were detected via multi-scale Standardized Precipitation–Evapotranspiration Index (SPEI) breakpoint analysis, and climate attribution was performed by correlating detrended lake areas with SPEI. Results show 59.4% of lakes exhibit significant trends, with shrinkage (50%) vastly outpacing expansion (9.4%), most severely in Jing-Jin-Ji (−0.28%/year). Despite all agglomerations transitioning toward wetter conditions (2008–2013), extreme event responses diverged markedly regionally. Climate-driven lakes (14.5%) displayed stronger shrinkage and greater sensitivity to extremes than lakes with low climate sensitivity, particularly in Jing-Jin-Ji and Chengdu-Chongqing. These findings reveal pronounced spatial heterogeneity in urban lake vulnerability, providing an evidence base for sensitivity-stratified management strategies.

Water doi: 10.3390/w18131567

Authors: Cuong Quoc Nguyen Takashi Nakamura

In mountainous river basins, groundwater systems are sustained by complex recharge processes and geological heterogeneity, making groundwater flow simulation challenging in data-scarce regions where hydrological inputs are often assumed to be spatially uniform. This study developed a heterogeneous geological model of the Kofu Basin, Japan, using multiple boreholes and simulated the groundwater flow by integrating MODFLOW with climate-driven recharge outputs from SWAT+. Simulated groundwater flow was evaluated against findings from previous stable isotope studies to assess the plausibility of the simulated recharge system. After calibration, the model performance improved substantially: RMSE decreased by 91.28%, MAE decreased by 84.38%, and NSE increased from 0.9530 to 0.9996. Independent validation showed good regional agreement between observed and simulated groundwater heads (R2 = 0.9307; NSE = 0.9254), although RMSE and MAE remained relatively high at 32.70 m and 19.76 m, respectively, suggesting remaining uncertainty in local-scale groundwater head simulation. Simulated velocity vectors indicated localized shallow flow and more coherent regional basinward flow in the deeper aquifer. This pattern is consistent with the interpretation that mountain-derived recharge contributes to the deeper regional groundwater system. The results highlight the value of combining hydrogeological models and geochemical evidence to support recharge-process interpretation in complex mountainous basins.

Water doi: 10.3390/w18131568

Authors: Anjan Samanta Sankar Sarkar

Machine learning prediction of turbulent bursting in near- and far-wake flow zones past two horizontal cylinders was studied in the present article. Based on the bursting dataset, two predictive models were constructed using Artificial Neural Networks (ANNs) and Support Vector Regression (SVR) with stress ratios as target values for each bursting event. After analyzing a number of plots, it was observed that the ANN and SVR models achieved satisfactory estimation accuracy, with minor overfitting specifically in the case of ANN models. By using deep learning for quadrant analysis and highlighting the adaptability of machine learning methods in open-channel turbulence, the current work should strengthen the understanding of bursting occurrences in bluff-body hydrodynamics.

Water doi: 10.3390/w18131566

Authors: César Sánchez-Pérez María-Inmaculada López-Ortiz Patricia Fernández-Aracil

Spain is among the European countries facing the highest water stress, notably along the Mediterranean arc. Despite this, it possesses unique capabilities in water management; it leads Europe in water reuse and desalination technologies, and has the continent’s highest number of dams per capita, securing most of its urban water supply. Nonetheless, the investment gap in the urban water cycle challenges Spain’s ability to meet European Union environmental targets and ensure the sustainability of public health and economic activities. Therefore, this study analyzes the causes of Spain’s urban water investment deficit, arguing that these challenges stem from institutional factors rather than a lack of resources or technological development. The research identifies three primary governance failures: the lack of a national governing body to harmonize water policies, a fragmented pricing system that drives the infrastructure gap, and a regulatory framework that restricts private sector involvement in managing non-conventional water resources. Consequently, this study highlights the urgent need for adaptive governance to deploy all available tools to respond to the specific needs of each territory in scenarios of uncertainty and climate change.

Water doi: 10.3390/w18131565

Authors: José Lugo-Arias Javier Carpintero Salvador Villamizar Jorge Luis Pacheco Yepes Ruben Cantero-Rodelo Leandro Gómez-Plata Keila Isabel Cruz

The progressive deterioration of surface water quality due to natural and anthropogenic factors, together with the limitations associated with conventional chemical coagulants, has driven the development of natural coagulants as sustainable alternatives for water treatment. In this context, the present study analyzed the production and application of a chitosan-based natural coagulant obtained from Oreochromis niloticus fish scales through a chemical method. The first phase involved biopolymer extraction through depigmentation, deproteinization, demineralization, and deacetylation; the second phase evaluated its performance as a coagulant using jar tests with water from the Magdalena River; and the third phase consisted of statistical analysis of the results using ANOVA. Yields of 78%, 78.20%, 88.52%, and 30% were obtained for each processing stage, and the chitosan achieved a degree of deacetylation of 76.87%, confirming its potential for water treatment applications. Optimal conditions were determined as a coagulant dosage of 300 mg/L and a flocculation time of 30 min, while ANOVA results indicated that both variables significantly influenced turbidity removal (p < 0.05). Under these conditions, a turbidity reduction of 76.30% was achieved. However, the final turbidity and color values did not meet Colombian regulatory standards, which was attributed to the presence of residual minerals and a moderate degree of deacetylation. Overall, the results demonstrate that chitosan derived from fish scales represents a sustainable alternative to chemical coagulants; however, process optimization and complementary treatment stages are required to meet drinking water standards.

Water doi: 10.3390/w18131564

Authors: Yantao Zhu

Dams and geotechnical structures are fundamental infrastructure for global water allocation, flood control, clean energy production, and agricultural irrigation [...]

Water doi: 10.3390/w18131562

Authors: Ce Luan Ming Yan Fuzheng Gong Yuxuan Yang Sheng Li Xue Liu Qi Wu

Suspended sediment concentration (SSC) is a key indicator of river sediment transport processes and water environmental change. For medium-width rivers, continuous-reach SSC monitoring remains constrained by the spatial discontinuity of station observations and the temporal or consistency limitations of single-source satellite imagery. To improve multi-year SSC characterization in the middle and lower reaches of the Liaohe River, this study integrated Harmonized Landsat and Sentinel-2 (HLS) surface reflectance imagery from 2016 to 2022 with SSC observations from five hydrological stations and developed a random forest retrieval model using multi-band reflectance and sediment-related spectral features. The trained model was applied to valid HLS images to examine SSC spatial distribution, interannual variation, and inter-station reach differences. The model achieved a test-set R2 of 0.641, an RMSE of 0.083 kg·m−3, and an MAE of 0.067 kg·m−3. The median composite of 52 retrieval images showed a lower SSC in the Tieling–Mahushan and Mahushan–Pinganbao reaches and a higher SSC in the Pinganbao–Liaozhong and Liaozhong–Liujianfang reaches. SSC was generally higher in 2016 and 2022 and lower in 2018. These findings indicate that HLS-based retrieval can support continuous-reach SSC monitoring and regional water–sediment dynamic assessment in medium-width rivers, although the accurate quantification of extreme high-SSC events still requires additional in situ samples and higher-frequency observations.

Water doi: 10.3390/w18131563

Authors: Sender Kyeremeh Sanoar Rahman

Urban freshwater systems are subject to complex, interacting anthropogenic stressors that collectively alter hydrological, chemical, and ecological dynamics. This study examines the temporal evolution of water quality across the Chicago River Watershed (CRW) and the Des Plaines River Watershed (DPRW) over a 25-year monitoring period (2001–2025). Long-term data from 51 stations were analyzed across ten water quality parameters. Principal component analysis (PCA) was applied annually to characterize shifts in multivariate water quality structure and identify dominant gradients governing system behavior. During the early phase (2001–2012), three principal components described the system, reflecting semi-independent stressor gradients. Beginning in 2013, a marked structural simplification emerged where a single dominant component accounted for approximately 78–84% of total annual variance, indicating strong parameter coupling and consolidation of system variability into a unified response gradient. This transition coincided with measurable declines in total phosphorus, total dissolved solids, and nitrogen. Nevertheless, the persistence of a single dominant gradient underscores the continued influence of urban environmental controls and tightly coupled pollutant pathways. These findings affirm the value of long-term, multivariate monitoring for characterizing urban water quality dynamics and informing adaptive watershed management.

Water doi: 10.3390/w18131561

Authors: Monika Ortueta Elisabeth Bilbao-García Olatz Rey-García Ian Rojo-Ortiz de Zarate Unai Duoandicoechea Natalia Villota Miren Arrate Celaya

Chlorinated benzoquinones such as 2,6-dichlorobenzoquinone (DCBQ) are toxic disinfection by-products that may persist in treated waters, requiring post-treatment strategies. In this study, the photo-Fenton process was evaluated for DCBQ degradation, with a focus on the influence of pH on kinetics, oxidation behavior, and water quality evolution. Experiments were conducted using 50.0 mg/L DCBQ, 1.0 mg/L Fe2+, and 2.0 mM H2O2 under UV irradiation (150 W) within a pH range of 3.0–12.0. Degradation followed apparent second-order kinetics, with maximum rates at acidic pH. At initial pH 3.0–5.0, rapid pollutant removal was accompanied by efficient aromaticity (UV254) and color elimination, intense dissolved oxygen consumption, transient turbidity peaks due to intermediate formation, and increases in total dissolved solids, indicating extensive oxidation and a high degree of organic matter transformation, as inferred from indirect physicochemical indicators. At near-neutral pH, oxidation was slower, with delayed aromatic and chromophoric decay and moderate accumulation of intermediates. Mildly alkaline conditions exhibited limited radical activity, stable turbidity, and reduced mineralization. Under strongly alkaline conditions, oxidation was largely inhibited, with persistent aromaticity and negligible oxygen consumption. These findings highlight the importance of integrating advanced oxidation processes with adsorption-based systems for efficient and sustainable water treatment of emerging contaminants.

Water doi: 10.3390/w18131560

Authors: Elena Krupa Sofia Romanova Sophia Barinova

The water bodies of southern Kazakhstan are under strong anthropogenic pressure, underscoring the relevance of their comprehensive research. In the summer of 2025, hydrobiological and hydrochemical studies were conducted at 32 stations across seven water bodies in the region. The dissolved solids content (TDS) ranged from 239.5 to 1472.5 mg/dm3, with favorable oxygen levels and relatively low nutrient levels. Zooplankton comprised 100 species, with rotifers predominating. Zooplankton abundance was 133.2–1289.9 thousand specimens/m3, with a biomass of 0.99–3.94 g/m3. The average number of species per sample varied from 11.5 to 26.7. The Shannon index values ranged from 1.20 to 2.74 bits. The average individual mass of a specimen varied from 0.0011 to 0.0371 mg. Cluster analysis revealed significant differences in the species composition of planktonic invertebrates across water bodies and their biotopes, which, according to the MDS analysis, reflected heterogeneity in external conditions. Analysis of multivariate data showed that the main factors shaping summer zooplankton community structure in the surveyed water bodies were TDS, silicon, and phosphate. The reasons for the identified dependencies between abiotic and biological variables are discussed. The high indicator significance of zooplankton communities in assessing the ecological state of aquatic ecosystems is demonstrated.

Water doi: 10.3390/w18131559

Authors: Tamás Mester György Szabó Emőke Kiss Dániel Balla

Shallow groundwater systems of rural municipalities are highly vulnerable to long-term contamination from former on-site sanitation systems, while the hydrochemical response of the aquifer after sewerage network development may be delayed by several factors. In the present study, a total of 147 shallow groundwater samples collected during the summer sampling campaigns of 2018, 2019, 2023, and 2024 were analyzed for general water-quality parameters including pH, EC, NH4+, NO2−, NO3−, PO4−, Cl−, SO42−, microelements, and potentially toxic elements, including As, Pb, Cd, Ni, Cu, Zn, Fe, and Mn. The dataset was evaluated using descriptive statistics, Piper, Wilcox, and Gibbs diagrams, hierarchical cluster analysis, principal component analysis, and GIS-based spatial interpolation. The results indicate that, more than ten years after sewerage network development (2014), shallow groundwater in the study area still shows considerable contamination, primarily characterized by elevated mean concentrations of ammonium (0.836 mg/L), nitrate (177.43 mg/L), and chloride (313.26 mg/L), accompanied by high electrical conductivity (3115 µS/cm) and sodium enrichment (378.12 mg/L). Spatial and boxplot analyses of SAR further indicated increasing sodium-related heterogeneity after 2018, with higher local SAR values in 2023–2024. Hydrochemical diagrams revealed a shift towards Ca-Cl type to Na–Cl types, while multivariate analyses confirmed that salinity enrichment, nitrate contamination, water–rock interaction and redox-sensitive trace element mobilization act as overlapping but partly separable controls. The nitrate–chloride source plot indicated mixed contamination origins, dominated by residual sewage influence and manure-related inputs, with diffuse agricultural nitrogen leaching. Arsenic was used as a supporting indicator of mixing with wastewater; however, As was no longer detectable in most of the investigated wells, suggesting a marked reduction in the former wastewater leakage. These results support the slow attenuation of contamination in the shallow groundwater system affected by former wastewater infiltration and highlight the need for continuous monitoring.

Water doi: 10.3390/w18131557

Authors: Dong Zhou Xiaochen Wang Kai Si Mingtang Liu Mengmeng Ge Zhixin Li Jinggan Shao

Water level monitoring is closely linked to the safety of production and daily activities along riverbanks, making real-time and high-precision water level measurement an urgent technical demand. The feature extraction backbone of the Unet model is modified, and the lightweight MobileNet V2 network is adopted in this paper. The constructed network achieves significantly higher computational efficiency than standard convolutions, effectively overcoming the limited real-time performance of conventional water level measurement methods. Furthermore, the coordinate attention (CA) mechanism is integrated into the skip connections of Unet to strengthen the network’s capability to extract key features for water level segmentation, thereby further improving the accuracy of water level detection. A novel piecewise linear fitting method for water level line measurement based on monocular vision is proposed, and field-measured water level data are adopted to verify the calculation results. The main achievements of the improved model include the following: (1) Compared with the baseline model, the improved model MCUnet (MobileNet V2 + CA + Unet) achieves a 5.77% increase in accuracy and a 25.71% improvement in inference speed on the experimental water surface recognition dataset. (2) Taking the field-observed water level as the reference, the mean absolute error of the proposed image-based water level monitoring method reaches approximately 1.69 cm. (3) In comparison with DeepLab, U2net and Unet, the MCUnet model gains accuracy improvements of 4.47%, 2.81% and 5.77% respectively, with the detection frame rate increased by 12 FPS, 15 FPS and 11 FPS correspondingly. Through this work, the paper can provide some theoretical support and technical references for overcoming the limitations of conventional water level measuring devices, including strict installation requirements, limited measurement precision, high deployment and maintenance costs, and cumbersome data processing.

Water doi: 10.3390/w18131558

Authors: Yanyan Cheng Dongliang Ma Xiao Liu Yubo Zhao Qianqian Bai Huimin Li

Water bodies play an important role in regulating settlement microclimates, and understanding the influence of water body morphology is essential for climate-adaptive settlement planning. This study quantified three key morphological parameters, scale, dispersion degree, and enclosure morphology, to investigate their effects on the microclimate of traditional Weizi settlements. Based on field measurements and ENVI-met simulations, fifteen water body layout scenarios were developed and evaluated using air temperature, relative humidity, wind speed, and PET. The results indicate that water body scale, enclosure morphology, and dispersion degree exert differentiated effects on thermal–humidity regulation, whereas their influence on wind speed is limited. The cooling and humidifying capacities followed the order of scale > enclosure morphology > dispersion degree, while the spatial influence range followed the order of enclosure morphology > scale > dispersion degree. PET analysis further demonstrated that larger water bodies, lower dispersion levels, and higher enclosure degrees contribute to improved outdoor thermal comfort. Under a constant water surface area, the optimal configuration consisted of a centralized water body layout with a water–land ratio of 0.49, a double-enclosure morphology, and a length-to-width ratio of 2:3. These findings provide quantitative guidance for climate-responsive planning and the design of water-adaptive settlements.

Water doi: 10.3390/w18131556

Authors: Anuradha Jangra

The article examines how India and Pakistan have interpreted the Indus Water Treaty (IWT) in the broader context of their preference, needs, and constraints. Rather than treating the IWT as a static legal instrument or as a case of institutional resilience, the analysis conceptualizes the Treaty as a performance-based regime, where treaty stability emerges from how states perform their obligations over time rather than from institutional design alone. Adopting a qualitative process-tracing approach grounded in treaty interpretation as operationalized through state practice, this article advances three interrelated arguments: first, the durability of the IWT cannot be explained solely by institutional design, but must be understood as a “performance-based equilibrium” sustained through state practice. Second, this stability historically relied on a pattern of “compliance asymmetry,” in which India, as the upper riparian, exercised restraint well beyond minimal entitlement while Pakistan consolidated downstream dependence through infrastructural development. Third, the growing juridification of dispute resolution since the 2000s, driven by escalating infrastructural friction, has altered the political meaning of compliance, narrowed interpretive flexibility, and reshaped reciprocal expectations. The article contributes to the scholarship of international legal theory and hydro-politics, particularly by reconceptualizing treaty resilience as a function of material and political performance, rather than the formal text alone.

Water doi: 10.3390/w18131555

Authors: Fangting Wang Ke Bao Xin Qi Xiaohan Wang

Karst terrains hold vital global groundwater reserves, underpinning regional water security and ecological stability. To elucidate groundwater hydrochemical patterns and formation mechanisms in Wuhan’s karst zone, this study adopted the Gibbs model, correlation analysis, principal component analysis and positive matrix factorization to explore water–rock interactions, hydrochemical origins, element migration, hydrogeochemical facies and genetic processes. The results show that water in both confined porous loose rock aquifers (CPLRAs) and karst fissure carbonate rock aquifers (KFCRAs) is mainly of HCO3–Ca and HCO3·SO4–Ca types. Carbonate dissolution dominates hydrochemical evolution, with Ca2+, Mg2+, and HCO3− as major ions. Natural water–rock interactions control the ionic characteristics of both groundwater types. Silicate weathering exerts a greater influence on water in the KFCRA, while water in the CPLRA has more complex ion sources. Anthropogenic activities contribute 17.52% and 17.61% to their hydrochemical variations, suggesting moderate human influence. Water in the CPLRA is mainly affected by domestic sewage and soil organic nitrogen, locally superimposed with industrial and mining disturbances. Water in the KFCRA is primarily influenced by agricultural pollution, with minor domestic sewage input. These findings provide a scientific basis for sustainable development, protection, and targeted pollution control of groundwater resources in the Wuhan karst area, and offer a reference for hydrochemical studies in comparable karst regions.

Water doi: 10.3390/w18131554

Authors: Sara P. Azerrad Shilat Parsha Hassan Azaizeh Nariman Mattar-Dabit Manal Haj Zaroubi Eyal Kurzbaum

Trihalomethanes (THMs) are priority disinfection by-products in drinking water, and their effective removal remains a persistent challenge for sustainable treatment. Here, olive mill solid waste (OMSW) was valorized into biochar (BC) and evaluated as a low-cost adsorbent for chloroform, bromodichloromethane (BDCM), chlorodibromomethane (CDBM), and bromoform under environmentally relevant conditions. Among the prepared materials, thermally activated BC (BC-T) performed best, achieving equilibrium removals of 74.7 ± 6.6% for chloroform, 91.1 ± 0.8% for BDCM, 87.2 ± 1.9% for CDBM, and 93.8 ± 0.3% for bromoform at 3000 mg/L. Adsorption increased with bromine substitution, following the order of bromoform > CDBM ≈ BDCM > chloroform, consistent with rising hydrophobicity. In contrast, KOH and Zn/Fe activation increased the BET surface area but did not improve THM removal, suggesting that adsorption was controlled by surface chemistry and site accessibility rather than surface area alone. Persulfate (PSF) addition reduced THM removal, indicating that oxidant activation did not compensate for the loss of adsorption capacity. Adsorption data were well described by the Freundlich isotherm and pseudo-second-order kinetics. BC-T also maintained high removal efficiency in drinking water, demonstrating its promise as a practical polishing adsorbent for THM control and as a route for high-value valorization of an abundant agricultural residue.

Water doi: 10.3390/w18131553

Authors: Marco Anglano Genuario Belmonte Enrique Isla Juan Usó-Canós Sergio Rossi

Mesozooplankton were studied monthly (September 2023–August 2024, 12 months) at two coastal stations, at 35 and 90 m water depth, off Punta Blanca, SW Tenerife, Canary archipelago. Sample collection involved 250 and 500 μm bongo nets. This research focused on improving the description of plankton biodiversity and dynamics of the Canary archipelago (Macaronesia area), including its role in the transport of particulate carbon. A total of 156 taxa were identified. Copepoda dominated with 85 taxa, including 72 Calanoida species. They were numerically followed by Appendicularia, Chaetognatha, and Hydrozoa. Mesh sizes varied in collection efficiency, but with a similar pattern during the annual cycle: abundance peaks in early autumn (October–November) and late winter–spring (February–April). The 35 m depth station showed 57 to 3809 ind. m−3 (250 μm mesh size) and 10 to 1577 ind. m−3 (500 μm). The 90 m depth station showed 22 to 402 ind. m−3 (250 μm) and 11 to 170 ind. m−3 (500 μm). The present study enhances our understanding of Macaronesia’s mesozooplankton dynamics related to environmental variability, which is crucial for energy transfer assessments in pelagic food webs. It reports new species for the study area, Labidocera acutifrons (Dana, 1849–1852) and Undinula vulgaris (Dana, 1849–1852), highlighting the need for consistent zooplankton monitoring to properly inform conservation and sustainable management actions in the region.

Water doi: 10.3390/w18131552

Authors: Dinis Girão Sónia Ferreira Vladimir Pešić Luís P. da Silva

Water mites (Hydrachnidia) are diverse, ecologically important arachnids that can serve as effective bioindicators; however, their communities in Mediterranean mountain rivers are scarcely documented. The present study provides a comprehensive analysis of water mite communities in mountain rivers of Serra da Estrela (Portugal), assessing how abundance, genus richness, and community composition vary across seasons, among rivers, and along an elevational gradient. Water mites were sampled in twelve sites belonging to 3 rivers across an elevational gradient and in three seasons. In total, 7296 adult water mites were collected, representing 33 genera and 17 families. Three genera were documented for the first time in Portugal: Albia, Hexaxonopsalbia, and Wettina. Abundance varied with season, being lower in spring (102 ± 35 specimens per site) than in summer (249 ± 73) and autumn (257 ± 83). Genus richness showed a similar pattern, with lower values in spring (9.8 ± 2.0) than in summer (12.2 ± 1.9). Spatial variation among rivers was comparatively minor. The multivariate analysis revealed that community-level changes between seasons, rivers and elevation were driven by only a few genera. The findings help improve the knowledge of Mediterranean mountain water mite communities, shedding light on their seasonal and spatial dynamics.

Water doi: 10.3390/w18131551

Authors: Tamer Elsakhawy Daniella Sári Mohamed H. Sheta Neama Abdalla Hassan El-Ramady József Prokisch

Nanotechnology offers transformative potential for wastewater treatment, yet its full-scale implementation remains bottlenecked by the “lab–reality gap”. While bench-scale studies using idealized matrices report outstanding pollutant removal efficiencies, performance routinely deteriorates in authentic wastewater due to complex matrix interferences, natural organic matter (NOM) competitive binding, fouling dynamics, and unpredictable nano–bio transformations. Moving beyond traditional reviews that focus heavily on material synthesis and theoretical capacities, this review provides a novel, systems-oriented, and function-driven perspective on environmental nanotechnology. We critically evaluate the operational stability and behavior of nano-enabled systems under realistic conditions, categorizing nanomaterial roles into reactive interfaces, selective barriers, signal generators, and biological modulators. Crucially, this work examines the synergistic integration of nanotechnology with advanced oxidation processes (AOPs), membrane bioreactors, and digital intelligence—including artificial intelligence (AI) and real-time nanosensing—to achieve smart fouling management and circular resource recovery. Finally, we propose a comprehensive, multidimensional evaluation framework that simultaneously assesses technical efficiency, stability, scalability, economic feasibility, environmental safety, and system compatibility. This review delivers a pragmatic roadmap to bridge the chasm between isolated laboratory discovery and robust, sustainable, field-scale wastewater engineering.

Water doi: 10.3390/w18131550

Authors: Lan Anh Phung Thi Yuki Itoh Seongwon Lee Masaya Yasuhara Ryuga Ono Takashi Nakamura

This study investigates nitrogen sources and biogeochemical pathways in a highly urbanized shallow aquifer in Shinagawa Ward, Tokyo, using an integrated approach combining hydrochemical analysis, multivariate statistics (PCA and K-means cluster analysis), and stable nitrogen isotopes (δ15N-NH4+, δ15N-NO3−, δ15N-DON, and dual δ15N–δ18O-NO3−). K-means clustering (K = 2, silhouette = 0.54) partitioned all 41 samples into a background group (n = 34) and an ion-enriched group (n = 7; wells sbi 1, 2, 3, 4, 5, 13, and 19), with the latter exhibiting hydrochemical signatures consistent with localized sewage leakage. The convergence of hydrochemical, multivariate, and isotopic evidence suggests that soil organic matter may represent the dominant diffuse background source of nitrogen across the study area. DON constitutes the dominant fraction of total dissolved nitrogen (TDN), while the linear correlations between TDN and DON concentrations (r = 0.77, p < 0.001) and between δ15N-TDN and δ15N-DON (r = 0.88, p < 0.001) indicate a common primary source. The dominance of DON combined with the theoretical inverse relationship between δ15N-DON and DON concentration is consistent with active soil DON mineralization, supported by an isotope fractionation factor (ε = −4.4 ± 0.78‰). Dual isotope analysis of NO3− (δ15N–N–δ18O slope = 0.51) points towards denitrification as an ongoing process in the aquifer. Taken together, the isotopic variations among nitrogen species suggest a transformation sequence from soil organic nitrogen → DON → NH4+/NO3− → N2, though each step in this sequence is supported to varying degrees of confidence. These findings highlight the value of δ15N-DON as a tracer for nitrogen source attribution and cycling in urban groundwater systems, and underscore the importance of considering all dissolved nitrogen fractions in contamination assessments.

Water doi: 10.3390/w18131549

Authors: Seung Hyun Son Hyeon Ji Kim Sang Chul Yoon Dae-Hyeon Kwon Hawsun Sohn Do-Gyun Kim

A total of 3930 blackfin flounder (Glyptocephalus stelleri) individuals were collected continuously on a monthly basis from the East Sea of Korea in 2024 (n = 1800) and 2025 (n = 2130). The total length ranged from 10.6 to 44.0 cm in 2024 and from 11.9 to 49.7 cm in 2025. The major prey items differed between the years. In 2024, polychaetes (75.3%) and amphipods (12.2%) were the dominant prey items, whereas in 2025, euphausiids (33.1%), polychaetes (33.7%), and fish (17.5%) were the most important prey groups, indicating a clear interannual variation in diet composition. PERMANOVA revealed that diet composition varied significantly with year, season, and size class (p < 0.05), with a significant interaction between the year and season. These patterns were consistently supported by the CAP ordination, which showed a clear separation of samples along the seasonal gradient on the CAP1 axis, with additional variations associated with the year and size class observed within the respective seasonal groupings. Ultimately, these results suggest that G. stelleri functions as an opportunistic feeder that is capable of shifting its diet in response to environmental fluctuations. This study aims to provide scientific data for efficient fishery resource management and ecosystem-based assessments in response to future climate change.

Water doi: 10.3390/w18131548

Authors: Xicheng Wang Junqi Jia Zhangbin Pan Congcong Li Zhenqi Du Ruibao Jia

Ribavirin (RBV) and chloroquine phosphate (CQP) are two typical pharmaceutical contaminants with distinct hydrophilic (RBV) and hydrophobic (CQP) properties. This polarity contrast led to markedly different degradation behaviors. Interestingly, hydrophobic CQP consistently degraded faster and with lower EEO than hydrophilic RBV across all combined systems, highlighting pollutant polarity as a key determinant. This study systematically compared their degradation by three UV-based advanced oxidation processes (UV/AOPs): UV/H2O2, UV/PMS, and UV/KMnO4. Degradation kinetics, electrical energy per order (EEO), radical pathways, and water matrix effects were investigated. Sole UV or sole oxidant achieved negligible removal (<7.2%). All UV/AOPs greatly enhanced degradation in a dose-dependent manner. At equal molar oxidant concentration (0.2 mM), the efficiency order was UV/PMS > UV/H2O2 ≫ UV/KMnO4, with the gap widening at higher dosages. UV/H2O2 exhibited the best overall performance, with remarkably low EEO values (0.59 kWh/m3 for RBV and 0.46 kWh/m3 for CQP at 0.2 mM), whereas UV/PMS showed faster kinetics but much higher energy consumption (e.g., 28.67 kWh/m3 for RBV and 28.60 kWh/m3 for CQP at 0.4 mM) and secondary pollution risks. UV/KMnO4 had low energy but poor degradation. Radical quenching experiments revealed that in UV/H2O2, hydroxyl radicals (•OH) predominantly drove degradation regardless of pollutant polarity. In UV/PMS, •OH primarily drove RBV degradation, while CQP removal involved the combined action of •OH, sulfate radicals (SO4•−), and other reactive species. For the optimal UV/H2O2 process, acidic pH (5.0) favored degradation; Cl− slightly promoted CQP removal but inhibited RBV, whereas SO42−, CO32−, and HCO3− suppressed both pollutants. Collectively, UV/H2O2 is recommended as the most energy-efficient and robust UV/AOP for treating both hydrophilic and hydrophobic pharmaceuticals, with the additional insight that pollutant polarity governs both degradation kinetics and radical mechanisms.

Water doi: 10.3390/w18131547

Authors: Debbie F. Sulca Bulbul Ahmmed Noah F. Hobbs Terry A. Miller Kevin D. Reid Philip H. Stauffer

At subsurface waste disposal sites, degradation of containment materials can cause leaks of chlorinated volatile organic compounds (Cl-VOCs) in the vadose zone. Material Disposal Area L (MDA L) is a heavily monitored waste site at Los Alamos National Laboratory in Northern New Mexico where a sharp increase in contaminant concentrations was measured in February 2019. Subsequently, soil vapor extraction (SVE) was performed as part of an ongoing interim measure. Here, we demonstrate a new method to introduce possible leakage within an existing numerical framework to bound possible leakage related to concentration increases seen in site monitoring data. A previously calibrated three-dimensional (3-D) model for SVE at MDA L is used to simulate the three conceptual stages from June 2017 to July 2024. The three conceptual stages based on the observed events are: leakage, passive diffusion, and soil vapor extraction. We use a 3-D multiphase flow simulator to introduce a simulated leak and attempt to approximately match monitoring data collected in February 2019, May 2024, and July 2024. After approximately matching the observed leak, outputs from the 3-D simulations were used to quantify the simulated mass of Cl-VOC leaked. Simulated results for a leak on the order of 40 kg of Cl-VOC showed general agreement with the monitoring data. Although the solution is non-unique, this paper presents a proof-of-concept addition to an existing case study, to show that a suspected subsurface container failure could create a signal consistent with the measured data and sets the stage for further analysis of future potential leak signals at the site. The work can also be adapted at other sites where changing subsurface conditions can require innovative modeling techniques to answer regulatory questions.

Water doi: 10.3390/w18131546

Authors: Chong Li Yanan Jiao Xiaoying Zhao Bin Yang Bo Bai

Acid mine drainage (AMD) pollution from closed coal mines in karst regions represents a major environmental challenge in the global mining industry. The complexity of hydrogeological conditions in such regions leads to significant challenges in both predictability and controllability of pollution. Taking the Yudong River Basin in Guizhou Province, Southwest China, as the study area, and based on six years (2017–2023) of systematic remediation practices and monitoring data, this study systematically evaluates the effectiveness and applicable conditions of three types of treatment technologies: centralized treatment stations, source control combined with end-of-pipe treatment, and water-sealing ecological plugging. On this basis, governance models applicable to karst regions are distilled. The results show that after six years of remediation, the number of pollution points in the Yudong River Basin decreased from 27 to 12. At the outflow section, the total Fe reduction rate reached 88.3%, the total Mn reduction rate reached 62.3%, and the proportion of contaminated river length was reduced by 78.5%. Each of the three technologies has its own applicable conditions. Centralized treatment stations, characterized by mature technology but high operational costs, are suitable for emergency transition periods. Source control combined with end-of-pipe treatment addresses both symptoms and root causes, making it applicable to complex pollution points. Water-sealing ecological plugging, although cost-controllable, carries a risk of secondary pollution in karst-developed areas. The failure of water-sealing ecological plugging technology is mainly attributed to two mechanisms: bypass flow through karst conduits and overflow induced by water level rise. Based on the six-year remediation practice, this study proposes a source control model for karst conduits centered on the core concepts of “filling, isolating, plugging, intercepting, draining, and controlling”. The implementation process consists of four stages: detailed investigation, graded optimization, stepwise implementation, and long-term monitoring. The core innovation lies in the cross-disciplinary application of coal mine water control techniques to environmental remediation, achieving a shift from passive end-of-pipe treatment to active source control. This model can provide theoretical reference and practical guidance for karst mining areas in Southwest China and other regions with similar geological conditions.

Water doi: 10.3390/w18131545

Authors: Duohui Zhao Wei Zhang Anfu Zhang Liang Yin Bin Yang Lei Song

The sources of potentially toxic elements (PTEs) in the lower reaches of the Yellow River (LYR) remain poorly understood due to intensive human activities in this region. To elucidate the spatiotemporal distribution characteristics and sources of PTEs, water samples were collected from both mainstream and tributary sites during the dry season (DS) and flood season (FS). Concentrations of eight PTEs (Fe, Mn, Cu, Zn, Pb, As, Cr, and Hg) were determined. The single-factor pollution index, Nemerow comprehensive pollution index, statistical techniques, and the positive matrix factorization (PMF) receptor model were jointly employed to evaluate PTEs pollution levels and quantitatively apportion its sources. The results showed that PTEs concentrations in the mainstream were significantly higher than those in the tributaries, with Fe and Mn being the primary contaminants exceeding standards. During the DS, the mean concentrations of Fe and Mn were 1.33 mg/L and 0.34 mg/L, with exceedance rates of 100% and 84.2%, respectively. In contrast, both concentrations declined markedly in the FS (Fe: 0.27 mg/L; Mn: 0.112 mg/L). The PMF model identified three sources in the DS, with contribution rates of 42.1% (geogenic background and domestic sewage), 32.4% (industrial wastewater), and 25.5% (agricultural sources). In the FS, two sources were resolved, namely a mixture of non-point source pollution and domestic sewage (64.3%) and a mixture of geogenic background and industrial wastewater (35.7%). The pronounced increase in non-point source contribution during the FS highlights the role of rainfall runoff in driving pollutant input. This study provides a scientific basis for PTEs pollution control in the LYR.

Water doi: 10.3390/w18131544

Authors: Dilip Kumar Roy Kowshik Kumar Saha Bithin Datta

Saltwater intrusion (SI) threatens groundwater sustainability in nearshore regions, particularly in Bangladesh, where over-extraction and sea-level rise accelerate aquifer salinization. Accurate prediction of SI dynamics is therefore critical for effective groundwater management. This study developed and evaluated several deep learning and hybrid models, including CNN, DNN, LSTM, CNN–DNN, CNN–LSTM, DNN–LSTM, and CNN–DNN–LSTM, to predict SI in a nearshore aquifer system. Predictor–response datasets were generated using the three-dimensional density-dependent flow and solute transport model FEMWATER. This study presents the first comprehensive benchmarking of standalone and hybrid CNN–DNN–LSTM models for SI prediction in a Bangladesh nearshore aquifer, supported by CRITIC–EDAS-based model ranking. Model performance was assessed using RMSE, MAE, MAD, R, IOA, a-20, NRMSE, along with CRITIC weighting and EDAS ranking. Results indicate that hybrid models integrating LSTM outperformed standalone models. The CNN–LSTM model achieved the best performance at OW1 (RMSE = 1.57 mg/L, MAE = 1.26 mg/L, R = 0.99, IOA = 0.99). The DNN–LSTM model performed best at OW2 (RMSE = 2.87 mg/L, IOA = 0.98, R = 0.97) and OW3 (RMSE = 1.95 mg/L, IOA = 0.99, R = 0.99). In contrast, the DNN model showed poor performance, while the CNN model demonstrated moderate performance and the LSTM model underperformed. Overall, the hybrid CNN–LSTM and DNN–LSTM models demonstrated superior accuracy and robustness for reliable SI prediction and sustainable groundwater management.

Water doi: 10.3390/w18131543

Authors: Yang Song Rui Hu Lirui Fan Huiyang Qiu

Travel–time-based thermal tracer tomography (TTT) has emerged as a promising technique for characterizing aquifer heterogeneity. However, the influence of travel–time definitions and data density on inversion performance is not well understood. In this study, we present a controlled two-dimensional sandbox experiment designed to systematically investigate three travel–time definitions (early-time t10, intermediate t50, and peak-time tpeak) under data-rich (32 travel times) and data-sparse (10 travel times) conditions. The obtained hydraulic conductivity (K) fields are benchmarked against permeameter measurements and a geostatistical inversion that assimilates dense steady-state head observations. The results demonstrate that all three travel–time definitions satisfactorily reproduce the primary layered heterogeneity when abundant travel–time data are available, with t50 and tpeak providing marginally better structural fidelity under data-rich conditions. However, only the early-time t10 definition preserves the spatial continuity of dominant geological structures under data-sparse conditions, exhibiting superior robustness. All TTT inversions systematically underestimate the K ranges and exhibit pronounced range compression, whereas the geostatistical inversion overestimates K and introduces spurious high-value extremes. Forward thermal transport simulations reveal that TTT-derived K fields yield systematically delayed thermal breakthroughs, while the geostatistical inversion yields more accurate predictions. These findings highlight the critical interplay between travel–time diagnostics and observation density. They also underscore the necessity of jointly inverting hydraulic and thermal data to overcome the limitations of single-dataset approaches for reliable aquifer characterization and transport prediction.

Water doi: 10.3390/w18131542

Authors: Vedanti Kelkar Vishal Solanki Peter Krebs

Indian metropolitan cities such as Mumbai grapple with rapid urbanisation, extreme urban density, high built-up areas, loss of green cover, and shrinking open spaces, resulting in increased impermeable surfaces, urban heat island effects, and frequent flooding occurrences. Modern stormwater management has increasingly been characterised by integrated grey-green approaches; however, cities in the Global North benefit from established policies, technical expertise, and financial resources that enable the systematic and large-scale integration of Blue-Green Infrastructure (BGI) through district-wide geospatial assessment frameworks, unlike many cities in the Global South. Despite growing interest in nature-based stormwater solutions, there remains a dearth of geospatial empirical research from India examining the placement, distribution, performance, and functionality of BGI integrated with existing stormwater management systems in cities such as Mumbai. Furthermore, hydrological modelling using tools such as the Storm Water Management Model (SWMM) for the design, planning, and implementation of BGI in Indian cities remains largely unexplored. This study explores the role of BGI strategies in improving urban stormwater management within high-density Indian cities under a 25-year return period extreme rainfall scenario. Using an integrated approach that combines QGIS-based spatial analysis with EPA-SWMM hydrologic-hydraulic modelling, the research examines runoff behaviour, identifies flooding hotspots, and evaluates the effectiveness of Low Impact Development (LID)-based BGI measures such as permeable pavements, infiltration trenches, and green roofs applied at the ward level in Mumbai’s F/North and G/North Wards. Detailed land use classification, spatial mapping, and rainfall simulation corresponding specifically to a 25-year return period rainfall event was used to assess pre- and post-intervention conditions. The findings indicate that the applied BGI measures led to a 12.6% reduction in peak runoff (137.6 m3/s to 120.2 m3/s) and a 5.5% decrease in total runoff volume (783,510 m3 to 740,410 m3). More importantly, the peak flooding flow rate decreased by 45% (94.1 m3/s to 51.7 m3/s), demonstrating that BGI measures can efficiently reduce peak flooding flows by extending runoff hydrographs during extreme rainfall events. These findings are specifically applicable to the simulated 25-year return period extreme rainfall scenario and may vary under different rainfall intensities or return periods. Less extreme events could potentially experience even greater relative reductions or prevent flooding altogether, while also easing downstream hydraulic loads. Overall, strategically placed BGI interventions can significantly reduce surface runoff and peak flow, thereby enhancing stormwater resilience within spatially constrained urban environments. This study provides a replicable, data-driven framework for catchment-scale stormwater planning in dense Indian cities under extreme rainfall conditions, offering practical insights into methods, local contextual considerations, and spatial planning strategies for policymakers and urban planners seeking to retrofit and adapt existing infrastructure under increasing hydrologic stress and climate variability.

Water doi: 10.3390/w18131541

Authors: Xuexiang He Mark L. Brusseau

Per- and polyfluoroalkyl substances (PFAS) are a group of anthropogenically manufactured chemicals widely detected in the environment. Characterizing their transport and fate in soil is important for assessing the potential of their human exposure and health impact. However, to date, few studies have been conducted to investigate the influence of PFAS on soil physical properties. This study investigates the impact of PFAS exposure on the surface wettability of soil via contact angle (θ) measurements. Contact angle was measured based on the fluid uptake rate in the Washburn capillary rise (WCR) method. Contact angles were measurably affected by the presence of 0.5 µg/g PFAS, with an increase of 4.5–6.8% for the exposed Accusand 40/50 and a decrease of 3.6–16% for the exposed Eustis soil, after 7 days of contact. The changes were attributed to the modification of the surface properties caused by the adsorbed PFAS. These results demonstrate that PFAS can potentially alter the surface properties of soils, which could subsequently impact soil hydraulic properties as well as affect geochemical interactions.

Water doi: 10.3390/w18131540

Authors: Il-Moon Chung Sun Woo Chang Ryan Bailey

Water resources systems are inherently complex, governed by dynamic interactions between surface water and groundwater across multiple spatial and temporal scales [Contribution 1] [...]

Water doi: 10.3390/w18131539

Authors: G.-Fivos Sargentis Levon Gevorkov Theano Iliopoulou

We propose a quantitative, spatially explicit framework for assessing local self-sufficiency and resilience within the Water–Energy–Food (WEF) Nexus. The methodology introduces normalized, per capita indicators that quantify the degree of dependence on local versus external resources, explicitly incorporating physical availability, renewability, energy requirements, infrastructure, and land-use constraints. In contrast to conventional composite indices, the proposed framework adopts a non-compensatory structure, whereby deficiencies in one sector cannot be offset by surpluses in another, reflecting the physical constraints of the nexus. Indicator values range from 0 (complete dependence on external resources) to 1 (full local self-sufficiency) and are formulated dynamically, enabling comparison across existing conditions and alternative infrastructural or policy scenarios. The framework is applied as a proof of concept to a small rural settlement in North Euboea, Greece. The results indicate substantial potential for food and renewable energy self-sufficiency under optimized infrastructure configurations, while also revealing critical vulnerabilities associated with groundwater-dependent water supply and seasonal energy imbalances. The analysis further demonstrates how spatial proximity, energy–water coupling, and land-use competition jointly constrain achievable self-sufficiency levels, highlighting trade-offs that are often overlooked in sectoral or purely volumetric assessments. By explicitly linking resource flows with spatial proximity and infrastructural choices, the proposed indicators provide a robust and transparent tool for resilience-oriented planning under conditions of climatic, environmental, and systemic uncertainty.

Water doi: 10.3390/w18131538

Authors: Chao Chen Zhenxiao Li Hao Yang Yumu Xu Wenjie Wang Minjie Sun Bo Zhang Weisi Chen

Loess slopes are prone to rapid infiltration, surface erosion, and shallow instability under intense rainfall, highlighting the need for eco-friendly shallow protection methods with enhanced anti-seepage and erosion resistance. To improve the applicability of microbially induced calcite precipitation (MICP) in loess slope protection, this study proposes a combined MICP–sesbania gum (SG) modification method. Permeability tests, surface hardness tests, and indoor artificial rainfall model tests were conducted to systematically evaluate its effects on seepage control and the erosion resistance of loess slopes. The results show that calcium chloride provides a stronger permeability-reducing effect than calcium acetate. Compared with the MICP-only treatment, the combined MICP-SG treatment significantly reduces the permeability coefficient and increases surface hardness. Based on the overall modification performance, a cementation solution concentration of 1.0 mol/L and a curing time of 7 d were selected as suitable treatment parameters. Rainfall model tests further demonstrate that the combined treatment delays erosion failure, reduces infiltration rate and soil loss, and suppresses wetting front migration and internal water content response. These findings indicate that MICP combined with SG can effectively improve the anti-seepage, erosion resistance and surface stability of shallow loess slopes, providing experimental support for eco-friendly shallow slope protection in loess regions.

Water doi: 10.3390/w18131537

Authors: Ibrahim Farhan Mohd S. Mahafdah Edlic Sathiamurthy Abel Chemura Jawad Al-Bakri Mustafa Al Kuisi Lina A. Salameh Fesail Albahrat

The Dead Sea, the Earth’s lowest major surface water body, serves as the terminal basin for surface and groundwater flow in its surrounding region. However, anthropogenic activities and natural processes contribute to significant alterations in the lake’s area. The scope and implications of these changes remain insufficiently documented, necessitating further investigation. The CA-Markov model was used to project the Dead Sea’s surface area for 2034 and 2050. Time series of observed and future climate data, especially temperature data, under Representative Concentration Pathways (RCPs) 4.5 and 8.5, were analyzed to track climate change. Statistical analyses of the Kendall correlation matrix were performed on the observed and predicted surface areas, water levels, and temperatures. This study revealed that the Dead Sea decreased by 41.8% from 1971 to 2022, and the sea level is expected to decrease by 12.63 m and 33 m by 2034 and 2050, respectively. In addition, there were significant inverse relationships between surface area, water level, and temperature, with correlations of r = −0.79 (p = 0.001) and r = −0.82 (p = 0.001), respectively. Notably, from 2022 to 2050, the mean annual temperature is expected to increase by at least 1 °C. The long-term strategic vision for stabilizing Dead Sea water levels involves a twofold approach: (1) augmenting natural inflow by introducing 300–400 million cubic meters (MCM) from manufactured sources and channeling them into the Jordan River, and (2) reducing water extraction by Dead Sea industries by a maximum of 330 MCM.

Water doi: 10.3390/w18131536

Authors: Lan Yang Shengnan Zhu Yanan Sun Zhuozheng Li Wei Gao Zhongxu Li

Reliable estimates of future precipitation are essential for adaptive water management in large river basins. This study presents a machine-learning approach that combines six CMIP6 models to examine precipitation changes in the Yangtze River Basin. ERA5 monthly precipitation for 1979–2025 served as the reanalysis reference. The random forest model incorporated individual model outputs, ensemble statistics, geographic variables, and monthly cyclic terms. It was trained with data from 1979–2009, evaluated for 2010–2014, and then applied to the period 2015–2099 under SSP1-2.6, SSP2-4.5, and SSP5-8.5. Compared with the simple multi-model mean, the proposed method showed better agreement with ERA5 and generally smaller reconstruction errors during the validation period. Annual precipitation is projected to increase under all three pathways, with the largest increase under SSP5-8.5. Precipitation remains concentrated from May to August, while spring totals and intra-annual variability increase more clearly under high-emission conditions. Mean precipitation remains highest in the humid middle and lower reaches, while the magnitude and significance of future trends vary across the basin. Inter-model spread remains greater than the differences among emission pathways and reaches 85.92 mm under SSP5-8.5 during 2071–2099. These results represent uncertainty-aware climate estimates rather than verified forecasts. They can support flood-risk assessment, reservoir planning, and adaptive water management in the Yangtze River Basin.

Water doi: 10.3390/w18131535

Authors: Alyssa Calomeni-Eck Alan Kennedy Jose Mattei-Sosa Andrew McQueen P. U. Ashvin Iresh Fernando Gilbert Kosgei Taylor Rycroft Daniel Tague Lauren May

Advanced oxidation processes using titanium dioxide (TiO2) have emerged as a promising approach for the photocatalytic degradation of contaminants in water and have drawn extensive research attention despite limited translation of this technology to large-scale applications. The limitations of this technology include immobilization of the photocatalyst, scalability, and compatibility with available light sources. Using 3D printing to immobilize TiO2-based photocatalysts, we systematically evaluated the rates of photocatalytic degradation of methylene blue (MB) with different light-emitting diode (LED) ultraviolet (UV) light sources and modified TiO2-based photocatalytic materials. The UV LED lights successfully decreased the MB concentrations with half-lives ranging from 0.9 to 2.4 h, with relative photocatalytic performance of UVA-365 > UVA-395 > UVC-280. The photocatalytic degradation rates under UV LEDs were slower (0.9–2.4 h) than those achieved using a low-pressure mercury UV-C lamp (0.5 h) and were also lower than those observed under solar simulated lights (0.6 h). The TiO2 modified by an alkyl silane entity and embedded in a polylactic acid polymeric system with 3D printing exhibited the fastest methylene blue (MB) removal among the three TiO2-based structures evaluated, with a half-life of 0.6 h compared to the 1.6–17.7 h for the other materials. This research demonstrated that 3D printing enables the integration of functionalized photocatalysts, and, when paired with low-cost, low-energy UV LED lights, can achieve environmentally relevant rates of performance. Ultimately, these findings represent an incremental step toward improving the performance of 3D-printed photocatalytic materials.

Water doi: 10.3390/w18131534

Authors: Ana Rita Alves Ângela Guedes Maria Luz Maia Piedade Barros Inês Baptista Sónia A. Figueiredo Valentina Fernandes Domingues Cristina Delerue-Matos

The Directive (EU) 2024/3019 on urban wastewater treatment (WWT) imposes new, stringent targets for nutrients and pharmaceutical compounds, thereby requiring the implementation of tertiary and quaternary treatments and promoting water reuse. This study evaluated the ecotoxicological impacts of advanced wastewater treatments applied to the effluent from a WWTP after secondary treatment: ultrafiltration (UF), ultraviolet radiation (UV), ozonation (OZ), and non-thermal plasma (NTP). Ecotoxicity assays were conducted using Raphidocelis subcapitata (chronic tests) and Daphnia magna (acute and chronic tests), representing primary producers and consumers, respectively. For R. subcapitata, no significant growth inhibition was observed for most treatments, while growth was promoted due to the presence of nutrients, except for OZ, which produced inhibitory effects. In D. magna, acute toxicity was low for most treatments, except for OZ, which showed significant toxicity. An additional chronic exposure experiment was conducted for the NTP-treated effluent, inducing adverse effects on growth and reproduction of D. magna; in contrast, R. subcapitata showed no effects, demonstrating species-specific sensitivity and trophic-level-dependent responses. These findings demonstrate that although advanced oxidation technologies enhance water quality, they may cause sublethal and lethal ecotoxicity effects, highlighting the importance of ecotoxicological evaluations in risk assessment of quaternary treatments, framed by Directive (EU) 2024/3019.

Water doi: 10.3390/w18131533

Authors: Frauke von den Driesch Sonja Szymczak

Climate-induced natural hazards can result in disruptions and failures of railway routes which are associated with high economic costs. Hence, the mechanisms of climate impacts posing a threat to rail transport must be identified, analysed and localised in railway networks. This study aims at assessing heavy rainfall hazards on the railway network of the federal state Nordrhein-Westfalen (NRW) in Germany and presents a GIS-based flooding indicator. A rule-based classification and aggregation approach with a hazard matrix was developed using potential flooding depths and flow velocities, resulting in five hazard classes. The approach was applied to the railway network in NRW for two heavy rainfall scenarios (N100, Next). The results show that the clear majority of route kilometres are classified as at least moderate hazard in both precipitation scenarios considered (Next 81%, N100 72%). On railway routes in low mountain range regions, more sections are assigned higher hazard classes than in flat landscapes. The plausibility of the indicator was explored through scenario, structural and conceptual parameter analyses, which support robustness of the results. The maps can serve as a tool for making qualitative statements on the potential impact on the German railway network and localising these impacts spatially.

Water doi: 10.3390/w18131532

Authors: Araujo Reyes Luis-Donato Percy Cesar Estrada-Ayre Percy Eduardo Basualdo-Garcia Anthony Enriquez-Ochoa Syntia Porras-Sarmiento Miriam Liz Palacios-Mucha Russbelt Yaulilahua-Huacho

Water scarcity in Peru is increasingly shaped by competing sectoral demands, particularly between large-scale mining and agriculture. Both sectors rely heavily on limited freshwater resources in arid coastal and Andean basins, generating complex trade-offs between economic productivity, environmental sustainability, and social equity. This review synthesizes and critically evaluates current knowledge on water footprint (WF) dynamics within mining–agriculture systems, integrating hydrosocial theory, water–energy–food nexus thinking, and sustainability transition frameworks. Mining activities in Peru are characterized by high blue and grey water footprints, associated with intensive extraction processes and contamination risks, while agriculture exhibits diverse water footprints depending on crop type, irrigation efficiency, and climatic conditions. The interaction of these sectors creates hydrosocial conflicts driven by unequal water allocation, environmental degradation, and institutional fragmentation. This paper identifies key drivers of conflict and evaluates emerging pathways for sustainability transitions, including technological innovation, nature-based solutions, and participatory governance mechanisms. An integrative conceptual framework derived from a thematic synthesis of the reviewed literature is proposed. The findings provide actionable insights for policymakers and researchers seeking to reconcile economic development with water sustainability in resource-constrained environments.

Water doi: 10.3390/w18131531

Authors: Roukaya Al Haj Ishak Al Ali Boris Armel Olou François Lestremau Monica Brienza Serge Chiron Andrés Sauvêtre

The presence of organic micropollutants such as pharmaceuticals and pesticides in aquatic systems poses risks to environmental and public health, as conventional wastewater treatment plants are often ineffective at removing them, highlighting the need for alternative solutions. This study evaluates the combined use of biochar and laccase to remove trimethoprim, clindamycin, and fipronil, selected for their ubiquity, persistence, and physicochemical properties. Commercial wood-derived biochar was used, and removal performance was assessed through adsorption isotherms, time-dependent evaluation of removal efficiency, and quantification by UPLC-MS/MS. Toxicity after treatment was evaluated using bacterial growth assays with Escherichia coli and Rhodococcus erythropolis. Adsorption of trimethoprim and clindamycin followed the Langmuir model (Qmax 2.27 and 1.49 mg/g), while that of fipronil followed the Temkin model (Qmax 0.98 mg/g). The combined biochar–laccase system enabled up to 99% removal of trimethoprim and clindamycin within one hour, demonstrating synergy between adsorption and enzymatic removal. Enhanced removal was also observed for clindamycin and fipronil in mixtures. Bacterial assays showed partial restoration of growth after treatment, suggesting reduced antibacterial activity of transformation products, although effects remained species-dependent. Overall, the biochar–laccase system shows promise for micropollutant removal, supporting green remediation strategies, but further work is required to characterize transformation products and assess ecological impacts.

Water doi: 10.3390/w18131530

Authors: Xin Zeng Yuan Yuan Jinqiong Zhao

Sediment deposition in water diversion channels threatens the operational safety and water supply reliability of large-scale inter-basin water transfer projects. This study investigates the deposition patterns and sediment reduction strategies for the diversion channel of the Shigu Water Source Project, a key intake hub of the Central Yunnan Water Diversion Project on the Jinsha River. A one-dimensional total-load sediment mathematical model (HELIU-2) was used to simulate deposition volume, particle size distribution, and sediment concentration at the pumping station intake under eight design scenarios spanning high-, medium-, and low-sediment years. Results show that over 95% of the deposited sediment in front of the pumping station is finer than 0.05 mm. Dredging reduces the deposition thickness at the pump intake by 13–25% in high-sediment years, significantly enhancing sediment trapping efficiency and reducing both average and maximum sediment concentrations. Longer diversion channels increase total deposition by 9–13% but reduce intake sediment concentration by 2–5% and decrease local deposition thickness by 27–42%, especially in high-sediment years. These findings provide quantitative support for optimizing desilting basin layout, channel length design, and dredging schedules. The proposed modeling framework and mitigation strategies may provide a reference for other large-scale water diversion systems facing similar sedimentation challenges.

Water doi: 10.3390/w18121529

Authors: Anuroop Singh Yarlagadda. Nancharaiah

De novo granulation of autochthonous microorganisms of water and wastewater reduces the start-up periods for cultivating aerobic granular sludge (AGS) and enrichment of degrading strains. However, it has not been demonstrated using refractory carbon compounds. This work investigated the formation of AGS from the seawater microbiome and establishment of pollutant removal pathways by feeding acetonitrile as the sole carbon and nitrogen source. Use of acetonitrile at an organic loading rate of 0.124 kg/m3/day enabled rapid emergence of aggregates and then stable granules (size: 1.3 mm; SVI5: 68 mL/g) within two weeks. TOC removal accompanied by ammonium nitrogen release was consistent and stable at 93% during the 50 days of bioreactor operation. Formation of acetamide and ammonium indicated involvement of nitrile hydratase and amidase enzymes in acetonitrile biodegradation. Ammonium released during acetonitrile biodegradation was removed by partial nitrification and the nitrite denitrification pathway. However, incomplete ammonium removal led to accumulation of up to 120 mg/L NH4+-N by day 50. Phosphate was removed via the enhanced biological phosphate removal pathway. This study shows that de novo granulation permits cultivation of AGS via the de novo granulation approach for simultaneous biodegradation of refractory acetonitrile and biological nutrient removal under saline conditions.

Water doi: 10.3390/w18121528

Authors: Yongfeng Zhou Hele Su Hanqing Huang Binghua Xu Jiasheng Cen Shipeng Chu

Leakage detection in water distribution networks is a core component of smart water management. Addressing the limitations of traditional acoustic detection methods, which heavily rely on manual expertise, and the inadequate feature extraction and low recognition rates for minor leaks of existing deep learning models in complex noise environments, this study proposes a novel hybrid architecture CNN model named Incep-ResNet. The model innovatively integrates multi-scale feature extraction and deep residual learning, incorporating an SE attention mechanism to achieve adaptive recalibration of feature channels. Experimental results demonstrate that the model achieves a leakage identification accuracy of 96.6%, representing improvements of 6.7% and 7% compared to ResNet18 and GoogLeNet, respectively. It exhibits excellent noise resistance and feature extraction capabilities, providing a new technical solution for intelligent leakage detection.

Water doi: 10.3390/w18121527

Authors: Andrea Gianni Cristoforo Nardini Giacomo Pellegrini Luca Mao Yoiner Ariza Fayder Herrera Jairo René Escobar Villanueva Emirielys Andrea Ospino Navarro

The Tomarrazón-Camarones Basin (La Guajira, Colombia) is characterized by frequent, widespread flooding and, anthropogenically, by intense instream sediment mining. Mapping flood hazard is hence essential to develop effective flood management plans, and a knowledge of the water regime (duration curves) is also essential to estimate sediment transport and carry out sediment budgets to inform on the impacts and sustainability of the mining activity. However, neither water levels nor discharges are monitored by official gauging stations, and only a few rainfall gauging stations are available in the area, with daily records often affected by data gaps. Therefore, a first challenge is to reconstruct discharge time series by an affordable effort, scaled to the financial-labour resources available in that challenging context. This paper presents an integrated approach that combines satellite-derived rainfall data with ground observations. A semi-distributed hydrological model (HEC-HMS, SCS-CN method) is used to reconstruct the full flow-rate time series once calibrated and validated with data derived from automatic sensors and field measurements. The model is fed with hourly data derived from daily data at ground gauging stations temporally downscaled by adopting the spatially distributed hourly rainfall patterns obtained from satellite records. Before that, observed water levels in three stations equipped with water level sensors were translated into discharge time series using analytical relationships based on field-measured geometric and physical characteristics. Then, these event-based hydrographs were used to calibrate and validate the model. Results show good agreement with observations, with R2 = 0.981 and a relative RMSE of 40% for overall hydrograph reproduction, and R2 = 0.87 for peak flow estimation, supporting a reasonable confidence in the approach. The calibrated model is then applied to long-term datasets (1973–2024) to retrieve duration curves and return periods of peak discharges.

Water doi: 10.3390/w18121526

Authors: Donghan Feng Can Qiu Yichen Liu Guili Feng

To enhance the meteorological forecasting and early warning service capability for urban waterlogging risks in Jinan, this study aims to investigate the relationship between rainfall and urban waterlogging. Based on minute-scale precipitation observations from 38 automatic weather stations and records from 70 waterlogging monitoring sites in the urban area of Jinan from 2011 to 2024, this study systematically analyzes the spatiotemporal characteristics of precipitation and waterlogging events and quantifies their response relationship. The main findings are summarized as follows. Heavy precipitation and waterlogging events are strongly temporally coincident, primarily occurring during the main flood season from June to August. Regarding diurnal variation, short-duration heavy rainfall and waterlogging events are concentrated between 14:00 and 20:00. The water depth of most waterlogging events ranges from 0.11 m to 1.04 m, with a median of 0.26 m, and the distribution of waterlogging exhibits a pronounced right-skewed pattern. A moderate positive spatial autocorrelation was observed in waterlogging depth, suggesting that severe urban waterlogging events are more likely to occur in the northern region of Jinan. The precipitation preceding waterlogging events is predominantly short-duration heavy rainfall. A strong temporal relationship exists between peak precipitation and maximum waterlogging depth. In nearly 90% of the waterlogging events, peak precipitation occurs within 2 h before the maximum waterlogging depth, with an average lead time of approximately 55 min. The relationship between antecedent cumulative precipitation and peak waterlogging depth is strongest at the 120 min timescale. About 90% of maximum rainfall over 10 min, 1 h, and 2 h did not exceed the 1-year return period threshold, indicating that the precipitation causing waterlogging events in Jinan is generally non-extreme.

Water doi: 10.3390/w18121525

Authors: Tianhao Zhao Dexiu Hu

River water quality monitoring data are often non-stationary and nonlinear and may contain occasional abnormal values. To support anomaly early warning, this study proposes an LSTM–SOA–DA framework. Water quality monitoring data for six indicators, including pH, DO, CODMn, NH3-N, TP, and TN, were collected from the Bahekou section in Xi’an at 4 h intervals from 2021 to 2023 and chronologically divided into training and testing sets at an 8:2 ratio. The Seagull Optimization Algorithm (SOA) was used to optimize the L2 regularization coefficient, initial learning rate, and number of hidden units of the Long Short-Term Memory (LSTM) network, establishing an LSTM-SOA forecasting model. Compared with traditional LSTM, BP neural network, Support Vector Machine (SVM), Extreme Learning Machine (ELM), and other optimization-based LSTM models, the proposed model achieved better RMSE and R2 performance, indicating improved prediction accuracy. Based on the residuals between observed and predicted values, the DA method was then used to determine indicator-specific anomaly thresholds from the residual distributions. The model identified 193 abnormal points in the test set. After manual rechecking, the Precision, Recall, and F1-score reached 87.6%, 93.9%, and 90.64%, respectively. These results suggest that the LSTM–SOA–DA framework can effectively identify abnormal fluctuations in river water quality data and support timely water environment management.

Water doi: 10.3390/w18121524

Authors: Yongliang Cui Yuting Zhang Yue Wang Kongping Xie Huan Xi Qingsong Chen Song Lu

Plateau waters in Northern Sichuan, China, act as critical headwaters of the Yellow River. Microbial communities in water bodies and soil matrices within this region are increasingly pressured by intensive animal rearing; yet few studies have characterized microbial shifts across entire riverine niches. In this study, we employed next-generation sequencing based metagenomics to investigate microbial features, community structure and diversity, metabolic potentials, and antibiotic resistance genes (ARGs) in the Baihe River, a tributary in the source region of the Yellow River. Sampling locations covered the main stem and three tributaries of the Baihe River, spanning from its source, through upstream and downstream segments, to the convergence site with the main stem of the Yellow River. Results revealed that Pseudomonadota and Bacteroidota were the most abundant phyla. The relative abundance of most taxa at multiple taxonomic levels exhibited an increasing trend along the river continuum driven by rising total nitrogen (TN) and total phosphorus (TP) concentrations; however, a notable exception occurred at BH1 (the Baihe source), where the abundance of numerous taxa was markedly higher than in downstream samples. We detected abundant ARGs predominantly associated with antibiotic resistance. Furthermore, prevalent viruses affiliated with the phyla Uroviricota and Nucleocytoviricota, together with pathogenic bacteria, were identified as etiological agents of diverse infectious diseases. This study provides novel perspectives for managing aquatic contamination in plateau river ecosystems by linking environmental variables, microbial succession, and resistome distribution.

Water doi: 10.3390/w18121523

Authors: Ashikur Rahman Gwo Chin Chung Yin Hoe Ng Kah Yoong Chan Soo Fun Tan

Water quality monitoring is a fundamental element of sustainable aquaculture management, as changes in parameters of physicochemical and biological properties directly affect the health, growth performance, and productivity of the aquaculture systems. Although traditional machine learning (ML) methods have demonstrated effectiveness in water quality classification, their performance often depends on large amounts of labeled data, which can be challenging and expensive to collect in real-world aquaculture environments. This study explores a few-shot learning (FSL) framework for data-efficient water quality classification under limited supervision to address this limitation. Several FSL models, including prototypical networks (ProtoNet), Siamese Networks, and Matching Networks were developed and evaluated in a comparative experimental framework against the traditional machine learning classifiers logistic regression, random forest, support vector machine and extreme gradient boosting. Low-data learning scenarios were simulated using a structured episodic evaluation approach. Experimental results demonstrate FSL techniques outperform traditional machine learning methods across all evaluated scenarios. Among the tested methods, ProtoNet achieved the highest performance, attaining an accuracy of 94.46% and an ROC-AUC score of 98.65%, indicating superior discriminative capability and robustness. Siamese Networks also demonstrated competitive performance under highly constrained data conditions. Furthermore, latent-space visualization, confusion matrix analysis, paired t-test statistical analysis, and ablation studies confirmed that episodic meta-learning enables the learning of highly discriminative latent representations with strong generalization capability under limited labeled data conditions. The findings highlight that FSL provides a robust and scalable framework for intelligent water quality classification in aquaculture systems, particularly in scenarios where labeled data are scarce, offering significant potential for sustainable aquaculture monitoring applications.

Water doi: 10.3390/w18121522

Authors: Ting Chen Guocai Xiong Zhanxin Gao Zhijie Song Jingyi Zhang Dandan Dong Hui Chen

Vegetation is an important component of ecosystems and plays an important role in carbon balance, water balance, and energy conversion. The spatial and temporal changes in the normalized difference vegetation index (NDVI), water resources, and hydrometeorological factors in southwest China between 2003 and 2020 were investigated using multisource remote sensing data. Correlation analyses were performed to assess the correlation among NDVI, water resource changes, and hydrometeorological factors with different time lags. A stepwise regression model with different lag times was constructed to clarify the effects of four topographic factors and eight climatic factors on NDVI, and the following conclusions were obtained: (1) NDVI increased from 2003 to 2020, and the increase became obvious after 2012. (2) NDVI was considerably affected by alterations in the soil water content caused by natural changes. The correlation of NDVI with evapotranspiration and precipitation was high, followed by NDVI’s correlation with surface temperature. The spatial distribution of the positive correlation between NDVI and evapotranspiration and NDVI and precipitation was relatively consistent, and a positive correlation was observed in most parts of Southwest China. (3) The hydrometeorological factors mainly affected NDVI with a lag of 0–1 month, and the correlation was high in western Sichuan and most of Yunnan. In Yunnan, Available Water Capacity (AWC) affected NDVI with a lag of 0–2 months; the lag was 0–1 month in western Yunnan and 1–2 months in eastern Yunnan. (4) In terms of different vertical heights, the NDVI in the regions with altitudes higher than 3000 m was affected by climate change, especially evapotranspiration and precipitation. (5) Digital Elevation Model (DEM), Latitude (Lat), Evapotranspiration (ET), Precipitation (PRCP), Land Surface Temperature (LST), and NDVI were closely related in the construction of stepwise regression models with different lag times.

Water doi: 10.3390/w18121521

Authors: Biao Sun Yuying Guo Chunling Wang Zhilei Zhen

The shells of testate amoebae are decay-resistant and well preserved in lake sediments, making them excellent biological indicators of climate change. In this study, the identification method for testate amoebae was initially optimized based on the collection of surface sediments from Dali Lake, and statistical analyses were conducted to investigate the community distribution characteristics and key environmental factors driving the testate amoeba species composition. According to the results, the testate amoeba species diversity in the surface sediments of Dali Lake was relatively low. A total of eight species belonging to five genera were identified, and the dominant species were Arcella discoides (35.64% of the total abundance), Phryganella acropodia (24.75%), and Arcella gibbosa (11.39%). All the identified testate amoeba taxa are common in global freshwater sediments, and no new species was discovered in this study. The testate amoeba community composition exhibited strong correlations with the total organic carbon, total nitrogen, dissolved inorganic phosphorus, and total phosphorus and weak correlations with the electrical conductivity and Chlorophyll-a.

Water doi: 10.3390/w18121520

Authors: Dinara Adenova Janay Sagin Malis Absametov Yermek Murtazin Vladimir Smolyar

Groundwater flow is an integral part of the Earth’s water cycle and plays a key role in assessing groundwater resource potential, characterizing the upper limit of possible groundwater withdrawal over a long period without depletion. The objective of this study is a comprehensive regional assessment of groundwater flow and the natural and predicted resources of fresh and low-mineralized groundwater in Southern and Western Kazakhstan. This assessment is based on an analysis of hydrogeological conditions and water balance, taking into account climate variability and anthropogenic load, to justify sustainable water resources management in arid territories. This article provides a regional assessment and mapping of groundwater flow, taking into account climate and anthropogenic changes in Kazakhstan, to refine the predicted resources of fresh and low-mineralized groundwater. The basin balance calculation results indicate that in arid and semi-arid regions, the decline in groundwater recharge by the 2050s will generally not exceed 10%. The average layer of groundwater flow of renewable groundwater resources in the Kazakhstan part of the Zhaiyk-Caspian water management basin (WMB) is estimated at 33.4 mm/year, and the average modulus of groundwater flow is 1.06 L/s per 1 km2. The average layer of groundwater flow of renewable groundwater resources in the Kazakhstan part of the Aral-Surdarya water management basin (WMB) is estimated at 14.8 mm/year, and the average modulus of groundwater flow is 0.47 L/s per 1 km2. The average layer of groundwater flow of renewable groundwater resources in the Kazakhstan part of the Shu-Talas water management basin (WMB) is estimated at 26.5 mm/year, and the average modulus of groundwater flow is 0.84 L/s per 1 km2. For mountainous and folded regions, the average layer of groundwater flow of renewable groundwater resources in the Balkhash-Alakol water management basin (WMB) system is estimated at 70.7 mm/year, and the average modulus of groundwater flow is 2.24 L/s per 1 km2. For intermontane and foothill basins, the average layer of groundwater flow of renewable groundwater resources in the Balkhash-Alakol water management basin (WMB) is estimated at 54.3 mm/year, and the average modulus of groundwater flow is 1.72 L/s per km2.

Water doi: 10.3390/w18121519

Authors: Meddage Kumara Pathmalal Manage Ganepola Ganepola Ponnamperuma Wijerathna Weiping Liu Shanshan Yin

Tropical coastal waters are increasingly recognized as critical reservoirs for virulent, antibiotic-resistant enteric pathogens, yet seasonal dynamics governing their spatial distribution remain poorly characterized. We hypothesized that hydrological shifts and anthropogenic nutrient enrichment drive the seasonal distribution, virulence profiles, and antimicrobial resistance (AMR) of Escherichia coli, Salmonella spp., and Shigella spp. in the Jaffna Peninsula, Sri Lanka. Across 25 coastal sites during dry and transitional seasons, we integrated physicochemical water quality assessment, culture-based enumeration, PCR-based virulence gene profiling, Minimum Inhibitory Concentration (MIC) assays, GIS mapping, and statistical analyses. Key water quality parameters, including ammonium, nitrite, and total phosphorus, showed significant seasonal variation (p < 0.05), reflecting distinct hydrological regimes across seasons. A total of 220 E. coli, 200 Salmonella spp., and 100 Shigella spp. isolates were examined for virulence gene profiles and antibiotic tolerance. E. coli was detected at 80–88% of sites, Salmonella spp. at 72–88%, and Shigella spp. at 32–48%. Among E. coli isolates, stx1 was detected at 20–28% of sites and eae at 16% across both seasons. The stn gene was detected in Salmonella spp. at 12–28% of sites seasonally. Virulence profiling confirmed STEC harbouring stx1, stx2, and eae; Salmonella spp. carried stn; and Shigella spp. possessed invasion-associated genes. Trimethoprim–sulfamethoxazole resistance was recorded in 63.2% of E. coli, 33.0% of Salmonella spp., and 31.0% of Shigella spp. isolates at the lowest tested concentration of 4 µg/mL., while ciprofloxacin and piperacillin–tazobactam retained greater efficacy. Correlation analyses revealed significant associations among faecal contamination, nutrient enrichment, and virulence gene prevalence, implicating untreated sewage discharge and eutrophication as likely ecological factors associated with pathogen occurrence. These findings designate the Jaffna coastal zone as a significant reservoir of virulent AMR enteric pathogens, underscoring the urgent need for integrated One Health surveillance and seasonally adaptive coastal water quality management.

Water doi: 10.3390/w18121518

Authors: Weimin Xie Bingyang Wang Jianghuan Hua Mingyang Li Gezi Li Fan Xia Tao Zuo Xiaochen Wang

Excessive fluoride intake from drinking water remains a public health concern in geogenic high-fluoride regions, yet direct evidence linking environmental fluoride levels to internal exposure in remote high-altitude areas is limited. This study integrated environmental monitoring with human biomonitoring to assess fluoride exposure and health risks in the Taruo Lake region of the Tibetan Plateau. Surface water (n = 45 for Taruo Lake; n = 8 for its tributaries) and groundwater samples (n = 4) were collected and analyzed for fluoride concentrations, and blood ionic fluoride (BIF) levels were measured in 122 local residents (47 adults, 75 children). The results showed that fluoride concentrations in most surface water tributaries of Taruo Lake and groundwater sources were below China’s drinking water standard, whereas those in Taruo Lake exceeded this limit (routine monitoring mean 2.54 mg/L; multi-site mean 2.79 mg/L). BIF levels were significantly higher in adults (0.126 ± 0.041 mg/L) than in children (0.075 ± 0.032 mg/L) and showed a positive correlation with age (r = 0.533, p < 0.001). Notably, 23.4% of adults and 1.3% of children exceeded 0.15 mg/L, an empirical threshold typical for healthy populations in non-endemic areas. Based on the hazard quotient (HQ) model recommended by the US EPA, most drinking water sources posed acceptable non-carcinogenic risks (HQ < 1). In contrast, Taruo Lake water presented an elevated risk (HQ > 1) in 2024 primarily due to the regional geological background, and although not used for daily drinking, this finding offers an indicative reference for local water management and risk prevention. This preliminary monitoring and biomonitoring assessment provides baseline data for future studies and underscores the necessity of continuous surveillance and evaluation of total dietary fluoride intake to protect the health of this vulnerable high-altitude population.

Water doi: 10.3390/w18121517

Authors: David A. Foltz Zachary J. Loughman

Burrowing crayfish are among the most important keystone species in North American ecosystems, yet they remain poorly understood. The Meadow River Mudbug (Cambarus pauleyi), native to West Virginia, was only recently described and is known from a very limited range in the Central Appalachians. During planning for an interstate pipeline, two large populations of C. pauleyi were found in the proposed right-of-way. As part of environmental compliance, salvage, relocation, and monitoring for the species were conducted from 2018 to 2024. All C. pauleyi were moved to the Meadow River Wildlife Management Area, where artificial starter burrows were created, and exclusion baskets were placed over them to prevent predation, the process of which is described herein. Monitoring showed a two-month survival rate of 74.0% to 85.5%. These results are promising for the future restoration of burrowing crayfish and other species that rely on crayfish burrows for habitat.

Water doi: 10.3390/w18121516

Authors: Shihan Wang Jiaqing He Aidi Huo Yapeng Li Yibing Cao Salah Elsayed Jahangir Muhammad Ilyas

Under the dual constraints of global food security and ecological protection, conventional agriculture is hampered by low resource efficiency and sluggish environmental response. Crop digital twin technology establishes a dynamic virtual reality system that integrates crops, environment, and water to enable real-time interaction and optimization. Based on the existing literature, this paper reviews the concept, architecture, and core modules of this technology and summarizes its applications in precision irrigation and crop monitoring. There are three major bottlenecks that persist, including limited high-frequency multi-source sensing and spatiotemporal fusion, insufficient parameter calibration and dynamic updating, and weak cross-scale integration from plant to watershed. Water is increasingly recognized as the key constraint and control variable and acting as both the central physiological driver of crop growth and the mass-flow link that connects the soil–plant–atmosphere continuum. The spatiotemporal dynamics of crop water deficit, compensatory root water uptake, evapotranspiration feedback, and the hydraulic behavior of irrigation-district canal systems constitute the core hydrological processes that must be simulated within the digital twin. Synchronizing crop water demand, soil moisture dynamics, atmospheric evapotranspiration, and irrigation scheduling within a unified spatiotemporal framework establishes a complete sensing, diagnosis, prediction and regulation technical chain. This chain offers a core pathway for alleviating agricultural water scarcity, improving irrigation efficiency, and ensuring food security.

Water doi: 10.3390/w18121515

Authors: Muhnad Almasoudi Soroosh Sharifi Hassan Hemida

An empirical model is developed to predict significant wave height and significant wave period using only wind speed at 10 m height, fetch, and water depth. The model distinguishes between fetch-limited and duration-limited sea states within a conditional empirical framework that incorporates modified empirical exponents and corrections into classical wave formulations. Validation was performed using wind and wave data from the Global Forecast System at 26 coastal and offshore stations distributed across eleven different pilot seas and oceans worldwide, encompassing a broad spectrum of marine environments and climatic conditions. The proposed model was benchmarked against established empirical approaches. Results indicate a mean prediction error of 6.6% for the significant wave height and 9.6% for the significant wave period, substantially outperforming conventional formulations whose errors exceed 50% under comparable conditions. Unlike existing empirical models that are restricted to specific regions or sea-state conditions, the proposed model demonstrated strong predictive performance across diverse seas, oceans, and climatic conditions, enabling more reliable wave predictions in data-scarce and dynamically complex marine environments. The developed model was further applied to the Red Sea, where it successfully reproduced the spatial variability of significant wave height and wave period. From the results, it has been found that the developed model provides a practical and transferable tool for wave forecasting, coastal engineering, and offshore renewable energy applications.

Water doi: 10.3390/w18121514

Authors: Ganga B. Basnet Samendra Sherchan

Urban water insecurity is an increasingly critical challenge in rapidly urbanizing regions of the Global South, driven by population growth, environmental degradation, infrastructure limitations, and institutional constraints. Kathmandu Valley, Nepal, exemplifies these interconnected pressures. This study presents a systematic review of 45 peer-reviewed and selected grey literature sources published between 2000 and 2025, conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were included if they examined drinking water contamination, public health risks, household coping practices, wastewater-related exposure, or governance dynamics in Kathmandu Valley, Nepal. Findings were synthesized using a narrative thematic approach. The review identifies widespread contamination across municipal supply systems, groundwater, tanker water, traditional water sources, and household-stored water. Microbial contamination, particularly total coliforms, fecal coliforms, and Escherichia coli, emerged as the most consistently reported and immediate public health concern. Chemical and physicochemical contaminants, including ammonia, iron, arsenic, nitrate, and turbidity, were also widely reported, especially in shallow and deep groundwater systems. Seasonal dynamics further influenced exposure risks, with increased microbial contamination during monsoon periods and greater dependence on alternative and less regulated water sources during dry seasons. The findings further indicate that unsafe water exposure is associated with a substantial burden of waterborne diseases and emerging risks such as antimicrobial resistance. Although household water treatment practices reduced contamination in some cases, risks often persisted due to recontamination during storage and handling. These burdens disproportionately affected marginalized and peri-urban populations with limited access to safe and reliable water infrastructure. The review also highlights persistent governance challenges, including institutional fragmentation, weak regulatory enforcement, inadequate infrastructure investment, and growing dependence on informal water supply systems. Together, these conditions contribute to a hybrid urban water system in which formal and informal sources coexist without consistent quality control. Overall, the evidence demonstrates that water insecurity in Kathmandu Valley is a systemic condition shaped by the interaction of environmental contamination, unequal exposure, household coping limitations, and fragmented governance. By integrating environmental, public health, and governance evidence, this review advances understanding of urban water insecurity in rapidly urbanizing contexts and highlights the need for integrated, equity-oriented, and governance-informed interventions. These findings have broader relevance for cities across the Global South experiencing similar environmental and infrastructural pressures.

Water doi: 10.3390/w18121513

Authors: Yazeed Algurainy

Mineral scaling on carbon electrodes remains a critical limitation to the long-term performance of capacitive deionization (CDI) systems treating hard and alkaline waters. In this study, alternating polarization (AP) is investigated as an in situ electrochemical regeneration strategy to reverse cathodic scaling in flow-through CDI treating a feed containing 5 mM NaCl, 5 mM NaHCO3, and 2.5 mM CaCl2 under three modes: conventional cycling (control), delayed AP introduced after fouling developed, and immediate AP implemented from the first cycle. Under conventional operation, cathodic scaling reduced the salt adsorption capacity (SAC) to 5.9 ± 0.2 mg/g, increased cathode mass from 0.208 ± 0.004 g (pristine) to 0.353 ± 0.054 g, and decreased specific capacitance to 28 ± 2 F/g, accompanied by extensive pore blockage and carbonate deposition observed by SEM and BET measurements. Application of delayed AP restored electrode functionality, increasing SAC to 8.9 ± 0.6 mg/g and specific capacitance to 56 ± 2 F/g while reducing the cathode mass to 0.212 ± 0.007 g and removing surface precipitates. The immediate AP operation reduced the extent of scale formation from cycle 1, maintaining SAC at 8.4 ± 0.2 mg/g throughout operation, with stable physical and electrochemical properties. These improvements are attributed to periodic polarity reversal, which induces alternating alkaline and acidic microenvironments at the electrode surface and promotes the electrochemical dissolution of carbonate phases during anodic polarization. Overall, this work establishes AP as a simple, chemical-free operational strategy for both preventing and reversing cathodic mineral scaling, thereby enabling sustained CDI performance and mitigating capacity loss over the tested operational periods in complex water matrices.

Water doi: 10.3390/w18121512

Authors: Tiziano Bo Anna Marino Margherita Abbà Francesca Bona Elisa Falasco Marta Moriondo Stefano Fenoglio

The use of mesocosms in stream ecology has long attracted the attention of researchers due to the clear advantages these systems offer for manipulative experiments. Despite some limitations, they provide an effective way to create semi-natural conditions in which selected parameters can be artificially controlled. This study presents the ALPSTREAM eco-hydraulic laboratory, a mesocosm system designed to mimic the conditions of an alpine stream (Ostana, NW Italy). The structure of this system is unique and consists of six 25-m-long flumes, fed directly by the Po River and equipped to regulate key hydraulic parameters. The paper describes the structure of this system and presents two case studies to illustrate some potential applications. The first aimed to analyze the impact of different aquatic insects (scrapers) on periphyton dynamics. The second tested the feasibility of the flumes for the ex situ breeding of a threatened fish species, the European bullhead (Cottus gobio L.). The purpose of this paper is to raise awareness of this facility and make it available to researchers interested in eco-hydraulic studies in mountain environments.

Water doi: 10.3390/w18121511

Authors: Tongzhou Wang Peipei Li Yong Li Lei Chen Yanqiu Wang

The biological treatment risk associated with wastewater containing the novel pigment intermediate N,N′-(1,4-phenylene)bis(acetoacetamide) has not been previously characterized. This study systematically evaluated the tolerance and performance of a laboratory-scale anaerobic–anoxic–oxic (AAO) system subjected to progressively increasing loadings of high-concentration (COD > 10,000 mg·L−1) wastewater. During a 39-day trial, the influent proportion was incrementally increased from 0.57% to 52.14% without system collapse. Complete microbial adaptation required approximately seven days. The anaerobic unit exhibited the highest sensitivity to shock loads, followed by the oxic unit, while the anoxic unit remained stable. GC-MS analysis confirmed the degradation of complex organic intermediates throughout the treatment stages, and TEST-based predictions indicated that the effluent exhibited lower predicted toxicity than the influent. Notably, cessation of mother liquor addition resulted in system self-recovery, further demonstrating robust shock resistance. This study provides the first experimental evidence of (i) unit-specific shock sensitivity (anaerobic > oxic > anoxic), (ii) a quantified adaptation period of approximately seven days, (iii) an operational threshold of 52.14% mother liquor without causing system collapse, and (iv) self-recovery following load cessation in an AAO system treating wastewater containing N,N′-(1,4-phenylene)bis(acetoacetamide). These findings extend previous AAO toxicity studies on industrial wastewater and present a practical, cost-effective mitigation strategy for full-scale applications.

Water doi: 10.3390/w18121510

Authors: Tania Pedimina Simone Bontà Stefanie Fumetti

Springs are environmentally stable habitats that are refugia for specialized species. Springs at Monte Generoso, Monte Bar, and Monte Tamaro in the southern Swiss Alps were investigated to understand how they are affected by human activities and environmental changes. We conducted (a) a temporal comparison of five springs at Monte Generoso, which were first sampled in 2011 and re-sampled in 2023 and (b) a spatial comparison of 19 springs of the three mountains. Physical and chemical parameters were measured, ecomorphology and anthropogenic impacts were evaluated, and macroinvertebrates were sampled. Springs at Monte Generoso changed along a temperature gradient. EPT-taxa shifted towards euryoecious taxa owing to environmental changes. The spatial comparison showed differences between the mountain summits driven by electrical conductivity and water temperature. These differences were mainly evident for Crenobia alpina and in the occurrence of Niphargus cf. thuringius in Bar and Tamaro as well as Drusus alpinus in Tamaro. Springs at Monte Generoso were the least diverse and exhibited the highest water temperature, possibly owing to the higher utilization pressure. Spring specialists were present even in heavily modified springs. This spatio-temporal analysis provided insights into the pressure on springs in the southern Swiss Alps, emphasizing the importance of a site-specific protection of these precious habitats.

Water doi: 10.3390/w18121509

Authors: Silvia González-Rojo Alvaro Martínez-Sánchez Xiomar Gómez

The transition to a circular economy requires the safe management of sewage sludge through nutrient and energy recovery. However, pharmaceuticals and personal care products (PPCPs) present a significant challenge. These compounds tend to accumulate in sludge via sorption, shifting the environmental burden from the aqueous phase to the sludge. This manuscript provides a comprehensive review of the scientific literature on technical alternatives for valorizing sewage sludge and removing emerging contaminants. The study evaluates the limitations of conventional biological methods, such as anaerobic digestion and composting, which exhibit variable efficacy and are often insufficient to degrade some commonly used pharmaceuticals. On the contrary, thermal treatments (pyrolysis, gasification, and hydrothermal processes) are considered robust alternatives capable of achieving the high removal of chemical compounds. Furthermore, the article emphasizes the innovative potential of utilizing carbon-based byproducts (biochar and hydrochar) as adsorbents, catalysts, or soil amendment to enhance the removal of PPCPs within the treatment infrastructure itself. The integration of advanced thermal technologies is essential to mitigate the risks of contaminant transfer to the food chain and ensure a safe and sustainable nutrient cycle.

Water doi: 10.3390/w18121508

Authors: Xiaolei Yan Qianwen Zhan Seping Dai Chuanfu Zang

Soil is the principal physical space for water conservation (WC), so analyzing the driving forces of soil on WC is significant for studying WC services and integrated environmental management. Guangdong Province, a major economic province in China, was taken as a research case to deeply analyze the spatiotemporal pattern of WC function from 2000 to 2020 with InVEST, and to reveal its soil driving forces using a classical mathematical statistics method. We found that, from 2000 to 2020, the WC functions in Guangdong Province exhibited significant spatiotemporal differences. High-value regions were mainly concentrated in the northern and western mountainous regions, while low-value areas were primarily in the Pearl River Delta. The total WC in Guangdong showed a fluctuating upward trend, with 10.71% of its area experiencing extremely significant improvement in the Pearl River Delta, followed by Northern Guangdong. Moreover, WC is influenced by the types and distribution areas of different soils. Red soil has the highest WC depth and volume, followed by paddy soil, while lateritic red soil has the lowest WC depth. Furthermore, soil components exhibited complex stratified relationships with precipitation-normalized WC (PNWC). Components characterized by cation exchange capacity (CEC), pH, and total exchangeable bases (TEB) were positively associated with PNWC, whereas aluminum saturation (ALSA) showed a negative association within the corresponding soil components. The findings provide an important scientific basis for the ecological governance of ecosystem WC functions and water resource management.

Water doi: 10.3390/w18121507

Authors: Lingzhi Xiang Weimin Yang Siqi Ma Jingkai Qu Yongjun Zhang Feipeng Wan Lingfu Yi

Min County experiences intense debris flow activity due to extreme weather and geological events. This study analyzes debris flow activity in Min County using GIS spatial analysis, time-series statistics, correlation analysis, periodic fitting, and field investigations across four event-based key periods (2002, 2012, 2013, and 2020). Long-term meteorological records (1951–2020) are introduced to support climatic trend analysis. Results indicate that stratigraphic lithology and fault tectonics control about 85–90% of the spatial distribution of debris flows, while extreme short-duration rainstorms trigger large-scale outbreaks and strong earthquakes further intensify activity. The high-occurrence cycle of debris flows (7–8 years) does not fully align with the annual wetness cycle (12 years). On a short time scale (years to decades), extreme earthquakes and rainstorms exert more significant impacts than normal precipitation patterns. This study preliminarily infers potential future peak periods of debris flows in Min County, with uncertainty from climate fluctuations and uncertain seismic events considered. The coupled mechanism of seismic weakening and rainfall triggering, together with lag-time characteristics, is revealed to support disaster prevention and mitigation.

Water doi: 10.3390/w18121505

Authors: Anar Imamverdiyev Zoltán Péter Jákói Cecilia Hodúr Sándor Beszédes

Sewage sludge management is increasingly shifting from a liability-focused “treat-and-dispose” approach toward resource recovery, where digestion residues and their liquid fractions are treated as secondary feedstocks for nutrient, water, and energy recovery. In Europe, the recast Urban Wastewater Treatment Directive strengthens performance and monitoring requirements and reinforces the need for efficient sludge treatment and downstream valorization routes. This review synthesizes evidence on how pretreatment-induced changes in digestate properties translate into membrane performance outcomes and maps practical design implications for selecting pretreatment-membrane trains for nutrient recovery and reclaimed water production. Pressure-driven membrane methods (MF/UF/NF/RO), together with membrane distillation and electrodialysis, are central candidates for producing clarified water streams and concentrating nutrients; however, their performance is governed by digestate rheology, colloidal stability, and the composition of soluble microbial products and inorganic ions, which collectively shape fouling and scaling risks. Pretreatments such as thermal hydrolysis and microwave conditioning can modify floc structure and solubilize organics, with potential benefits for dewaterability and mass transfer, but can also shift particle size distributions toward fines and increase fouling propensity if not coupled with appropriate solid–liquid separation and conservative flux control. Emphasis is placed on mechanisms and operational trade-offs rather than single-point performance claims, highlighting where evidence is robust and where further comparability and full-scale validation remain necessary.

Water doi: 10.3390/w18121506

Authors: Kpade O. L. Hounkpatin Amadou Keita Ebagnerin J. Tondoh Djéneba Djamila Traoré Nouroudine Morou Hamadou Aymar Y. Bossa Yacouba Yira Jean Hounkpe Traoré Hortense Kagambèga Olayèmi Ursula Charlène Gaba Djigbo Félicien Badou Sarah Konaré

Understanding how irrigation water management shapes crop performance is critical for improving productivity and resource-use efficiency in peri-urban agriculture. This study investigated the socio-technical factors driving sprinkler system abandonment and assessed how irrigation water variability influences vegetable yield variability at two market gardening sites (Bogdin and 14 Yaar) in Ouagadougou, Burkina Faso. Survey data from 50 farmers and field measurements of soil properties, irrigation water application, and lettuce yield were analyzed using descriptive statistics, Spearman correlations, and principal component analysis. More than 80% of farmers had ceased using the sprinkler system within two years of installation, 76% reported major equipment failures, and 70% expressed willingness to re-adopt an improved system. Irrigation dose and yield showed considerable variability across sites (CV = 20.9–42.3% and 36.4–44.0%, respectively). At 14 Yaar, irrigation dose was strongly associated with yield (r = 0.862, p = 0.006), indicating that uneven water application was a major constraint on productivity. At Bogdin, where irrigation was more uniform, no single soil or water variable dominated yield variability. Although soil fertility variables contributed to multivariate patterns, nutrient–yield correlations were not statistically significant under the available sample size, and their potential influence on yield requires confirmation with larger datasets. Overall, operational constraints, equipment failures, and inadequate support services contributed to sprinkler system abandonment, while variability in manual water application was associated with variability in crop productivity. These findings highlight the need for irrigation strategies that are both technically robust and adapted to farmers’ realities.

Water doi: 10.3390/w18121504

Authors: Yaoxuan Cheng Zeming Shi Xinyue Zhao Lixin Li

Per- and polyfluoroalkyl substances (PFASs) are persistent emerging contaminants characterized by high environmental stability and biotoxicity. Ubiquitous detection of these contaminants across aquatic environments poses severe threats to ecosystem stability and human health, while constructed wetlands (CWs) serve as a sustainable low-carbon alternative for the remediation of PFAS-laden wastewater. However, traditional mechanisms such as matrix adsorption, phytoaccumulation, and microbial transformation often suffer from low efficiency, rapid saturation, and incomplete degradation. To overcome the above drawbacks, the arbuscular mycorrhizal fungi (AMF)–plant–microbe synergistic consortium has become a promising remediation candidate, which facilitates PFAS immobilization and biodegradation via symbiotic crosstalk among three components. This paper reviews recent advancements in PFAS remediation within AMF-facilitated systems, examining fundamental synergistic mechanisms, treatment efficiencies, and key influencing factors. We propose several optimization strategies, including substrate modification, operational parameter refinement, and the integration of advanced technologies. Furthermore, we emphasize the necessity of elucidating the molecular pathways governing long-chain PFAS degradation and addressing current bottlenecks in engineering applications. Future research should prioritize molecular interaction level interaction mechanisms, the development of anti-interference systems, and field-scale validation. This review provides a theoretical foundation and technical framework for leveraging AMF–plant–microbe synergism to enhance PFAS removal in CWs.

Water doi: 10.3390/w18121502

Authors: Chengjiang Deng Bo Kong Huan Yu Han Wang Jianan Li Kangkang Li Yunfeng Gao

This study established a refined, distributed SWAT modeling framework that integrates elevation-band and snowmelt modules to reconstruct the alpine hydrological and sediment cycles of the Koshi River Basin (KRB) over the period 1990–2024, with climate scenarios constructed using the delta change approach. The KRB, a major transboundary watershed traversing China, Nepal, and India, was selected owing to its critical hydro-climatic role under the destabilizing “Asian Water Tower”; it generates substantial sediment yield, hosts the densest concentration of hydropower potential within the Ganges system, and spans an extreme vertical gradient from Mount Everest to the southern alluvial plains. Results reveal accelerated warming at a rate of 0.21 °C per decade and an overall warming–wetting trend, punctuated by an abrupt interdecadal shift around 2015. Precipitation dominated interannual streamflow variability, with enhanced rainfall triggering basin-wide sediment surges that overwhelmed the natural buffering capacity of the land surface. Conversely, rising temperatures intensified actual evapotranspiration, markedly depleting soil water and reducing total water yield and monsoon runoff, although sustained snow and glacier melt effectively elevated the dry-season low-flow baseline. The integrated climate forcing reshaped the disparity between hydrological extremes, imposing severe seasonal eco-hydrological stress that manifested as a pre-monsoon deficit in terrestrial green water and acute summer sediment outbursts for aquatic habitats. Furthermore, the flood regime exhibited an altered distribution, with mid-to-high frequency floods enhanced while low-frequency extreme flood peaks declined. The hydro-sedimentological regime consequently exhibits pronounced nonlinear responses to climate change, providing a critical, threshold-based scientific foundation for adaptive transboundary water resource management.

Water doi: 10.3390/w18121503

Authors: Mei Chen Dongyu Lu Ruxi Feng Wei Li Xudong Guo Fei Tian Changfa Xia Lei Huang

To elucidate the pollution status and spatial distribution patterns of microplastics in representative deep-sea regions of China, the Qiongdongnan sea area has emerged as a key focus area for microplastic research. A comprehensive assessment of microplastic contamination across the water column (0–1500 m) was conducted using CTD-integrated water sampling coupled with 0.2 μm membrane filtration. Results revealed that polypropylene (PP), polyethylene (PE), and polyamide (PA) were the dominant polymer types. Granular microplastics constituted the overwhelming majority (95.3%) of identified particles, while size analysis showed that those in the 20–50 μm range accounted for the largest fraction (80.5%). The average microplastic abundance across all sampled depths was 3.47 particles/L. Comparative analysis with other prominent marine environments globally and domestically indicates minimal vertical differences in the characteristics of microplastics. Comparative analysis with other prominent marine environments globally and domestically indicates that microplastic pollution in the South China Sea is relatively moderate. This study delivers foundational empirical data critical for environmental risk assessment and source apportionment of microplastics in the South China Sea. This study provides key basic data for assessing the environmental risk of microplastics in the South China Sea and tracing their sources.

Water doi: 10.3390/w18121501

Authors: Armand K. Houanyé Félix T. Amoussou Ernest Amoussou Richard Todé Henri S. Totin Vodounon Mohamed N. Baco Japhet D. Kodja Pierre I. Akponikpè Gil Mahé Jean-Emmanuel Paturel

Water resource management in the Sahelian-Sudanian transition zone faces growing uncertainty under climate change, yet hydrological projections remain scarce for the Oti-Pendjari basin (West Africa). This study develops an integrated modelling chain combining CMIP6 multi-model evaluation, bias correction, and GR4J hydrological modelling to project streamflow changes under SSP2-4.5 and SSP5-8.5 over 2021–2100. Eleven CMIP6 models were evaluated against ERA5 reanalysis data (1960–2014) using NSE, KGE, and MAE; the three best-performing models were bias-corrected using Linear Scaling, Variance Scaling, Quantile Mapping, and Quantile Delta Mapping. Linear Scaling proved most effective, with CMCC-ESM2 best reproducing observed precipitation (NSE and KGE up to 0.9), while the multi-model approach performed best for temperature. The GR4J model, calibrated at Porga, Mandouri, and Mango (KGE: 0.609–0.668), satisfactorily reproduces intermediate flows and flood dynamics, although structural limitations persist for low flows (KGE [1/Q]: −0.65 to −0.71). Projections reveal a marked divergence between scenarios: SSP2-4.5 yields September peak flow increases of +5.7% to +16.7%, whereas SSP5-8.5 leads to slight decreases of −1.1% to −3.6%, likely driven by increased potential evapotranspiration partially offsetting precipitation gains. These findings underscore the critical importance of scenario selection and model uncertainty in regional water resource planning.

Water doi: 10.3390/w18121500

Authors: Samin Shapour Miandouab Mustafa Meriç Aksen Mehrshad Gholami Anjiraki Fotis Sotiropoulos SeokKoo Kang Ali Khosronejad

Accurate three-dimensional characterization of turbulent flows in natural waterways is essential for the effective design of tidal farms and other critical infrastructure situated along or across rivers. High-fidelity predictions based on the large-eddy simulation (LES) method capture the necessary physics but incur computational costs that hinder rapid scenario testing. Statistically, a relatively long history of instantaneous flow fields is required to generate reliable turbulence statistics, e.g., mean velocity and Reynolds stresses, of river flow. Such a requirement often incurs high simulation runtime and data storage costs. This study seeks to develop a neural network surrogate model that learns from a limited number of instantaneous flow realizations and approximates the outputs of the corresponding time-averaged fields with LES-level accuracy. Such a surrogate would eliminate the need to accumulate extensive ensembles, enabling faster hydrodynamic assessment and making LES-informed analyses more accessible for practical engineering decisions.

Water doi: 10.3390/w18121499

Authors: Leonardo Mendoza Antonio Lima Harold de Mello Maria Maceira Albert Melo Marco Pacheco

Understanding how climate variability is reflected in streamflow is essential for reservoir management and hydropower planning. This study investigated how temporal scale influences climate–streamflow relationships, persistence characteristics, and predictability in two Brazilian reservoirs: Três Marias (São Francisco Basin) and Serra da Mesa (Tocantins Basin). Monthly streamflow and climate-index records (Pacific Decadal Oscillation (PDO), El Niño–Southern Oscillation (ENSO), and Antarctic Oscillation (AAO)) from 1979–2020 were analyzed using a 12-month moving average (MA12) filter to emphasize low-frequency variability. Temporal filtering strengthened climate–streamflow relationships, particularly for PDO and AAO, revealing signals that were less apparent in the original monthly series. Lagged-correlation analyses identified contrasting persistence structures between the reservoirs. Três Marias exhibited multi-year persistence timescales (22–27 months), whereas Serra da Mesa showed shorter and more heterogeneous response timescales, ranging from an immediate PDO response to approximately 14–19 months for ENSO and AAO. Forecasting experiments using benchmark models (Persistence and Linear Regression) and deep learning architectures (LSTM and TCN) showed limited predictive skill on the raw monthly series but substantially improved performance after temporal filtering. For the MA12-filtered series, the benchmark models achieved the highest performance in both reservoirs (R2≈0.95 in Três Marias and R2≈0.93 in Serra da Mesa). Overall, the results indicate that temporal scale strongly influences the detectability of climate signals, the persistence of streamflow variability, and the predictability of reservoir inflows.

Water doi: 10.3390/w18121498

Authors: Xinyu Wu Xiang Zhang Xiaolei Zhang Zhiheng Xu

The relationship between water and sediment in the lower reaches of the Yellow River is uncoordinated, leading to frequent floods. In this area, the floodplain is situated below the main channel and embankment foundations, increasing the likelihood of overbank flooding. Ecological protective forests serve as a nature-based mitigation measure by reducing flow velocities along embankments and lowering the risk of structural failure during near-bank flood events. To assess the role of ecological protective forests, laboratory experiments were conducted, and field data informed parameterization and geometry selection. A total of 24 scenarios were designed, combining four forest arrangements (A1, A2, A3, and A4), two submergence degrees (H0/H = 0.5 and 1.0), and three water and sediment conditions. Results show that sediment deposition increases with vegetation density. Under constant vegetation density and embankment-aligned flow, a larger along-flow to cross-flow spacing ratio promoted deposition upstream, whereas a smaller ratio extended deposition further downstream. Deposition thickness was greater under fully submerged conditions than under semi-submerged conditions. Among the arrangements, sediment deposition effectiveness followed the order A1 > A2 > A4 > A3, with arrangement A1 providing the strongest promotion of deposition. Under varying flow–sediment conditions, the A1 arrangement enhanced sediment deposition by 6.8% to 20.6%. Flow structure was also modified: under semi-submerged conditions, the vertical profile of longitudinal velocity approximated a logarithmic distribution, whereas full submergence produced a different profile due to combined drag from tree trunks and canopy. Vertical sediment concentration profiles were similar under both submerged states, with minimum values near the water surface and maximum concentrations near the bottom. These changes confirm that ecological protective forests contributed to reducing flow velocity and diminishing sediment transport capacity.

Water doi: 10.3390/w18121497

Authors: Nektarios N. Kourgialas Monica Garnier Aldo Tamburrino Rohitashw Kumar Gideon Oron Nicholas Dercas Andreas N. Angelakis

Across human history, water has sustained communities while also shaping religious imagination as a symbol of life, danger, purification, and renewal. This review examines how water acquires religious meaning through symbolic associations, ritual uses, theological interpretations, sacred landscapes, and material water infrastructures across more than five millennia, drawing on examples from ancient civilizations, long-standing Asian traditions, Indigenous religions of the Americas and the Caribbean, and the three major Abrahamic religions. The study explores how rivers, springs, rain, floods, wells, sacred basins, and ritual waters have been understood as signs of creation, purification, fertility, healing, divine presence, destruction, and renewal, while also remaining part of everyday practices of settlement, agriculture, health, and communal life. The comparative analysis highlights recurring patterns and cultural differences. In some traditions, water appears as a primordial substance from which life emerges; in others, it functions as a medium of moral cleansing, ritual preparation, communal prayer, or sacred geography. The study argues that the religious meaning of water is best understood through the interaction of four closely related dimensions: symbolic interpretation, ritual practice, sacred or culturally charged landscapes, and material water infrastructures. By bringing these dimensions together, the article uses the concept of hydraulic heritage to connect religious water symbolism with sacred basins, wells, springs, hammams, monastic water systems, irrigation rituals, and other inherited water-related landscapes and practices. These connections offer a culturally grounded perspective for contemporary discussions on environmental ethics, water protection, and societies’ responsibility toward natural resources.

Water doi: 10.3390/w18121496

Authors: Leonardo Castillo-Sánchez Luis Darío Sánchez-Torres María Fernanda Jaramillo-Llorente Edgar Leonardo Quiroga-Rubiano Diego Gómez-Calle Andrés Fernando Echeverri-Sánchez

Increasing pressure on surface water resources in intensive agricultural regions has driven the search for sustainable alternatives for irrigation supply, especially in areas where water quality limits crop safety and export opportunities. In this context, riverbank filtration (RBF) systems offer a nature-based solution by utilizing physical, chemical, and biological processes associated with river–aquifer exchange. However, their implementation depends on suitable site selection supported by hydrogeological, geomorphological, and hydraulic criteria. This study developed an integrated methodology to identify zones with potential for implementing RBF systems in the Roldanillo–Unión–Toro irrigation district, located in northern Valle del Cauca, Colombia. This region requires irrigation water over 10,256 ha of agricultural land (mainly sugarcane, maize, grapes, and guava). We combined geophysical methods (vertical electrical soundings, 2D electrical resistivity tomography, and passive seismic), geotechnical methods (CPTu tests), and hydraulic characterization of the river reach to evaluate subsurface stratigraphy, preliminary hydrogeological suitability, inferred river–aquifer connectivity conditions, and channel stability. The evaluation covered four sectors along an approximately 21 km stretch of the Cauca River’s left-bank alluvial valley. The results revealed pronounced lateral and vertical heterogeneity of alluvial materials. However, the “El Palmar” sector was identified as the best-supported priority sector for future RBF validation, due to the presence of profile-scale evidence of potentially permeable sandy and gravelly units with intermediate resistivity values (52–61 Ω·m), favorable stratigraphic organization, and stable river-reach conditions during the field campaign. In contrast, the other three sectors (La Esperanza, Candelaria, and Cayetana) showed more fine-grained sediments with deeper permeable strata. River-flow measurements during the July 2025 field campaign indicated high discharge conditions at the evaluated reach, while river-channel observations showed active fine-sediment transport; these findings provide hydraulic and sedimentary context for the future evaluation of induced infiltration and potential clogging, but do not constitute direct evidence of river–aquifer exchange. This study highlights the value of integrated screening approaches for prioritizing candidate RBF sites in agricultural alluvial settings, while indicating that pumping tests, piezometric monitoring, hydraulic-gradient analysis, and water-quality validation remain necessary before engineering implementation.

Water doi: 10.3390/w18121495

Authors: Tânia Mara Sebben Oneda Enedir Ghisi

Human activities and economic development require large amounts of water and energy. The analysis of the nexus between water and energy flows can improve the understanding of the quantitative relationship between the two resources and guide actions and policies to obtain better results with lower risks. This article aimed to analyse and evaluate the use of rainwater in urban environments and its relationship with the water–energy nexus through a literature review. The PRISMA guidelines were used to structure the research, and the RStudio programme was used for the bibliometric analysis. A total of 118 articles published between 2013 and 2023 were identified in the Scopus and Web of Science databases, of which 30 met the eligibility criteria and were included in the review. The risk of bias in the studies included was assessed by two independent reviewers, and disagreements were resolved by consensus. The results were synthesized in a narrative and descriptive way, and organized in a table containing the authors, year, country, and main findings. The studies were grouped according to the theme addressed and the results related to the use of rainwater and the water–energy nexus were compared. The results indicate that the main use of rainwater is for non-drinkable purposes, to reduce the demand for potable water, lessen the pressure on water resources and contribute to environmental sustainability. Climate change can affect rainfall regimes and, consequently, the feasibility of systems. By decentralizing water supply services, the use of rainwater can save drinking water. When assessing energy savings, the use of rainwater is not always the best option, as system configurations and pump specifications are determining factors. Regarding the environmental impacts, all stages of the urban water cycle consume energy for their operation, and the environmental impact is directly related to the energy source used. Policies and regulations focused on rational use, water conservation, demand reduction, and tax incentives for the installation of rainwater harvesting systems, together with awareness campaigns, are necessary for the widespread adoption of rainwater harvesting systems. Finally, there is consensus regarding saving drinking water, but there is still a lack of studies and specifications regarding energy savings. The findings highlight the need for future longitudinal and simulation-based studies to strengthen knowledge of water–energy nexus dynamics in buildings.

Water doi: 10.3390/w18121494

Authors: Jhonatan Hinojosa Mamani Benito Calsina Calsina Yalmar Ponce Atencio Juan Tito Humpiri Henry Pizarro Viveros Edwerson Pacori Paricahua Jose Ramos Choque Maximiliano Cornejo Turpo

Climate change is expected to significantly affect hydrological processes in high-Andean basins, where water availability depends strongly on seasonal precipitation and groundwater recharge. This study evaluates future impacts on runoff, groundwater recharge, renewable water resources, and water stress in the Coata River basin (Lake Titicaca watershed, Peru) using the SWAT model forced with CMIP5 climate projections (MPI-ESM-MR and ACCESS1-0 under RCP 4.5 and RCP 8.5 for the period 2025–2100). Model calibration showed satisfactory performance (R2 = 0.86; NSE > 0.80). Results indicate a pronounced reduction in groundwater recharge, strong variability in runoff, and persistently high water stress across scenarios. Although some projections show increases in runoff, reduced infiltration and subsurface storage limit effective water availability. Renewable water resources exhibit contrasting responses depending on the scenario, with both increases and decreases relative to historical conditions, but with greater variability overall. These findings highlight the high sensitivity of the Coata River basin to climate variability and emphasize the need to incorporate climate projections into water management strategies, including recharge zone protection, improved storage capacity, and more efficient water use.

Water doi: 10.3390/w18121493

Authors: Shudong Zhou Qile Ding Yi Zhang Tongwei Zhang Yiren Wang Xinrui Song Fengyang Wang

Reliable prediction of landslide run-out distance is of great importance for hazard zoning and risk mitigation. However, most previous studies evaluate model performance within a single landslide inventory, while the transferability of models across different triggering mechanisms remains insufficiently explored. To evaluate whether landslide run-out-prediction models and their uncertainty estimates remain reliable when transferred between rainfall-induced and earthquake-induced landslide inventories, this study investigates trigger-dependent run-out behavior and cross-trigger transferability using a harmonized inventory of 10,158 rainfall-induced and 681 earthquake-induced records. Common geometric descriptors, including run-out distance L, elevation difference H, source area A, source volume V, and mean slope angle θ, were used for distributional comparison, scaling-law analysis, machine-learning prediction, tail-risk assessment, and uncertainty quantification. The results show that earthquake-induced landslides occupy a larger geometric domain, whereas rainfall-induced landslides exhibit greater elevation-normalized mobility. Cross-trigger prediction experiments reveal substantial and asymmetric transfer degradation, with systematic overprediction in R→E and underprediction in E→R. Prediction-interval reliability also deteriorates markedly under cross-trigger transfer, indicating that uncertainty estimates calibrated within one trigger type may not remain reliable when applied to another. These findings suggest that trigger-associated inventory differences should be explicitly considered in landslide run-out modeling. Direct application of models across rainfall- and earthquake-induced landslide inventories may lead to biased predictions and unreliable uncertainty estimates.

Water doi: 10.3390/w18121492

Authors: Laura Rima Khaled Haddad Ataur Rahman

This study presents regionalisation of the Generalised Extreme Value (GEV) distribution by adopting L moments and Bayesian Generalised Least Squares (BGLS) regression. This uses data from 88 gauged catchments in New South Wales, Australia. The regional GEV distribution is compared using the Parameter Regression Technique (PRT) and Quantile Regression Technique (QRT) under fixed-region and Region-of-Influence (ROI) approaches. Results indicate improved regional flood estimation, capturing spatial variability and reducing uncertainty in flood quantile estimation through the ROI approach compared to fixed regions. The mean flood statistic shows a higher spatial heterogeneity in the fixed region approach, while the ROI approach more effectively reduces uncertainty and enhances predictive performance. For fixed regions, PRT achieves a median relative error (Rer%) of 34–40% and a relative root mean square error (RRMSE%) of 59–65%, compared with QRT’s Rer% of 40–63% and RRMSE of 59–94%. In the ROI framework, both techniques yield similar Rer% (31–40%), though QRT-ROI exhibits slightly reduced RRMSE.

Water doi: 10.3390/w18121491

Authors: Darwin Alberto Núñez Torres E. Fabián Rivera Stefani Vanesa Vega Reinel José Luis Altuna Vásquez

This study evaluates the microbiological quality of drinking water in the urban area of Guaranda through an integrated approach combining culture-based methods, biochemical characterization, and polymerase chain reaction (PCR) analysis. A total of 50 drinking water samples were collected from strategically selected points within the urban distribution system following Ecuadorian technical standards. Microbiological analyses included the detection of total and fecal coliforms, as well as the isolation and identification of Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes. Culture-based analyses revealed that 22% of samples were positive for total coliforms and 4% for fecal coliforms. In selective culture media, contamination rates reached 18% for E. coli O157:H7, 8% for Salmonella spp., and 46% for Listeria monocytogenes. However, biochemical profiling showed substantial inconsistencies with the expected phenotypic characteristics of these pathogens, particularly in oxidase and citrate tests, suggesting possible false-positive identifications in complex environmental matrices. PCR assays confirmed lower detection frequencies, identifying E. coli O157:H7 and Salmonella spp. in 2% of samples each, and Listeria monocytogenes in 10% of samples. Agarose gel electrophoresis validated the amplification of specific DNA fragments of 212 bp, 244 bp, and 388 bp, respectively. The findings demonstrate significant discrepancies between conventional phenotypic methods and molecular techniques, highlighting the limitations of culture-based identification when used alone. This study emphasizes the importance of integrating molecular diagnostics into routine water quality monitoring programs to improve the reliability of pathogen detection and support more effective public health risk management in urban drinking water systems.

Water doi: 10.3390/w18121490

Authors: Zhi Wei Xueting Wu Yancong Wu Caihong Chen Yu Pang Jinkui Wu

The Liujiaxia–Heishanxia reach is critical for water and sediment regulation in the upper Yellow River, where changes in runoff–sediment relationships greatly affect downstream channel stability and flood safety. Climate change and intensive human activities have substantially altered local hydrological regimes in recent decades. Using long-term hydrological records from five stations during 1956–2020, this study applied the Mann–Kendall test, moving t-test, wavelet analysis and XGBoost algorithms to analyze the trends, abrupt changes and periodic features of runoff and sediment load, and quantify the contributions of natural and human drivers. The results show that both runoff and sediment load decreased significantly, with a sharper decline in sediment load. Major abrupt changes occurred in 1969, 1986, 1996 and 2008, and both variables presented a dominant 40-year interdecadal cycle. Human-induced landscape changes became the leading factor driving hydrological variations after 1996. Our findings suggest that future watershed management should combine landscape optimization and climate adaptation to maintain stable runoff-sediment conditions. This work provides scientific references for water resource management and the construction of the Heishanxia Water Conservancy Project.

Water doi: 10.3390/w18121489

Authors: Qing Luo Yixuan Zheng Yukun Jiang Qing He Lu Yang Shuxin Hu Xinye Zhao

Polycyclic aromatic hydrocarbons (PAHs) in farmland soils pose potential ecological and human health risks, yet their contamination characteristics and source-related risks in farmland soils across different river basins in China remain insufficiently understood. This present study analyzed 84 farmland soil samples from northeast (primarily the middle and lower reaches of the Songhua River and Liao River basin), central (primarily the middle reaches of the Yellow River basin and Dongting Lake system), northwest (primarily the middle and upper reaches of the Yellow River and Yarlung Zangbo River basin), and southern (primarily the upper reaches of the Pearl River and Yangtze River basin) China in order to assess the contamination characteristics, sources, ecological risks, and human health risks associated with 16 US EPA priority PAHs in the samples. The findings suggest that the 16 aggregate PAHs’ concentrations in Chinese farmland soils varied from 63.9 to 9637.7 μg/kg, with an average of 1919.3 μg/kg. A gradual decline was observed from north to south, with dibenz[a,h]anthracene (DahA) accounting for the highest proportion at 14.3%. Correlation analysis, principal component analysis, and positive matrix factorization jointly indicated that fossil fuel combustion, high-temperature combustion, and traffic-related emissions were the main PAH inputs to farmland soils. The results of the ecological risk assessment indicated that the northeastern region exhibited the highest PAH ecological risk, with 41.2% of sample plots demonstrating severe PAH contamination. Conversely, the southern region exhibited the lowest PAH ecological risk, with 73.9% of the sample plots demonstrating no ecological risk. The human health risk assessment found that non-carcinogenic risks for both children and adults were within safe limits, while carcinogenic risks for both groups were relatively high. DahA was identified as the primary carcinogen, accounting for 45.9% and 70.3% of the total carcinogenic risk for children and adults, respectively. Oral ingestion was the primary route of exposure. This study provides an integrated basin-scale assessment of PAH contamination and source-related risks in Chinese farmland soils, supporting targeted management of PAH inputs in agricultural environments.

Water doi: 10.3390/w18121488

Authors: Yibing Song Fengming Zhou Xinqi Zhao Yan Sun Jialin Chen Yaohong Yang Shoukai Chen

To investigate the three-dimensional seepage response and safety implications of high concrete-face rockfill dams (CFRDs) under waterstop failure scenarios, this study establishes a refined three-dimensional finite element model for a high CFRD at the JD Hydropower Station using COMSOL (version 6.1) Multiphysics. A comparative analysis is conducted for six representative scenarios, including peripheral joint failure, single vertical joint failure, overall vertical joint failure, and combined failures. The seepage safety assessment is based on the phreatic surface, seepage discharge, hydraulic gradients in key zones, and left- and right-bank abutment bypass seepage. The results show that waterstop failure significantly changes the seepage field, phreatic surface, leakage discharge, and hydraulic gradients. Among the six scenarios, S5, representing overall vertical joint failure with an aperture of 0.5 mm for each of the 41 vertical joints, produces the most unfavorable leakage response, with the total seepage discharge reaching 3010.46 L/s and the water level behind the face slab reaching 3888.23 m. In contrast, peripheral joint failure mainly induces local hydraulic-gradient concentration in the special cushion zone. Under S1, the maximum hydraulic gradient in the special cushion zone reaches 2.72, exceeding the allowable value of 0.72. The results also reveal asymmetric bypass seepage around the dam abutments, with the right-bank foundation leakage being 90.4–137.7% higher than that on the left bank. These findings clarify the distinct seepage risk mechanisms of different waterstop failures and provide support for waterstop design, construction quality control, targeted monitoring, and operation-stage safety assessment of high CFRDs.

Water doi: 10.3390/w18121487

Authors: Zijiang Yang Tao Zhang

Anaerobic co-digestion (AcoD) is increasingly applied in sewage-sludge management and organic-waste treatment because it can improve methane recovery, stabilize mixed substrates, and reduce life-cycle greenhouse-gas emissions under appropriate feedstock and operating conditions. However, existing reviews still focus mainly on feedstock types or isolated enhancement measures and less often connect synergistic mechanisms with engineering implementation and carbon outcomes. The specific novelty of this review is to connect functional feedstock classification, mechanism boundaries, engineering controls, and carbon-performance evaluation within one sludge-centered AcoD framework. This review synthesizes recent progress in AcoD of sewage sludge, food waste, livestock manure, crop residues, and industrial organic streams through a chain from feedstock traits to substrate interactions, microbial responses, engineering performance, and carbon benefits. Feedstocks are reorganized by function rather than by waste name, highlighting how carbon-to-nitrogen contrast, buffering capacity, hydrolysis recalcitrance, and inhibitor profiles jointly define synergy potential. Key mechanisms, including C/N balancing, hydrolysis complementarity, inhibitor mitigation, and direct interspecies electron transfer (DIET), are discussed together with their applicability limits. Representative evidence shows methane-yield or methane-production increases of about 41–55% for selected food-waste–manure blends, approximately 45% for rice–straw–pig manure systems after cellulolytic pretreatment, and approximately 16–55% for selected additive strategies; these values are illustrative rather than directly comparable because the underlying studies differ in substrates, baselines, reactor configurations, pretreatment conditions, and operating parameters. The review then translates mechanism into practice through pretreatment, reactor-selection templates, operating windows, additive reinforcement, and artificial-intelligence-assisted monitoring. Representative cases and life-cycle evidence indicate that AcoD can improve methane productivity while lowering greenhouse-gas emissions relative to landfill or mono-digestion pathways when energy substitution and nutrient recycling are credibly counted. Remaining bottlenecks include incomplete kinetic integration, limited DIET quantification, insufficient reporting of quantitative operating ranges and additive dosages, and weak coupling of carbon, economics, and regional feedstock dynamics. The revised review therefore treats AcoD as a sludge-centered mechanism-to-engineering framework and highlights two transferability gaps that require stronger standardization: biodegradation/toxicity testing and local co-substrate logistics.

Water doi: 10.3390/w18121486

Authors: Ruitao Jia Suying Ma Sa Wei Zhenbo Ma Shanshan Ji Daying Zhang

Accurate prediction of groundwater level (GWL) is of great significance for refined groundwater management. This study establishes a multi-model framework for predicting groundwater level by integrating the three-dimensional transient MODFLOW model, artificial neural networks (ANN) and long short-term memory (LSTM). The results reveal that the numerical model satisfactorily reproduces groundwater level variations during calibration and validation periods, with relative errors within 1.5 m for over 91.67% of the monitoring wells. The performance of LSTM model is significantly outperformed by the ANN model with the NSEs greater than 0.92 and RMSEs smaller than 1.51 m during the training period and validation periods. Multiple scenarios were established to compare and verify the prediction accuracy of the LSTM and numerical models. RMSE values ranged from 0.054 to 0.187 and 0.012 to 0.121, respectively. In addition, the RMSE value increases with the extension of the prediction period. The uncertainty value of the LSTM model gradually decreased from 1.0 to 0.74, while that of the numerical model remained at 0.71. This indicates that the physical process constraints of the numerical model can enhance prediction stability and interpretability under different scenarios, while machine learning can efficiently satisfy high-frequency adjustment requirements and respond to abrupt disturbances. This study provides scientific references for accurately predicting GWL and comparative research between numerical models and machine learning models.

Water doi: 10.3390/w18121485

Authors: Nevena Čule Aleksandar Lučić Marija Nešić Goran Češljar Ilija Đorđević Jelena Božović Vladan Popović

Eutrophication remains a persistent water-quality problem in shallow lakes, where external inputs interact with internal loading and biogeochemical cycling. Although floating treatment wetlands (FTWs) are increasingly promoted as nature-based solutions for water remediation, their field-scale interpretation in hydrologically complex eutrophic lakes remains challenging. This study examined the spatial organization of water quality during the operation of a floating-island system in a eutrophic urban lake affected by polluted tributary inflow. The study was not designed to quantify isolated FTW removal efficiency, but to evaluate spatial water quality organization during FTW operation under real-use field conditions. Water quality was monitored over two growing seasons across six functionally defined zones, and spatial and temporal patterns were analyzed using descriptive statistics and linear mixed-effects models. The results showed parameter-specific spatial structuring rather than a uniform treatment response. The clearest inlet-lake contrasts were observed for electrical conductivity (EC), suspended matter (SM), and nitrate nitrogen (NO3-N), whereas biochemical oxygen demand (BOD5), ammonium nitrogen (NH4-N), and total organic carbon (TOC) showed lower values at the inlet and higher values in downstream zones. Dissolved oxygen (DO), oxygen saturation (SO), chemical oxygen demand (COD), nitrite nitrogen (NO2-N), and orthophosphate phosphorus (PO4-P) showed moderate or non-robust zonal effects. These findings indicate that FTWs in shallow eutrophic lakes should be evaluated through functional zoning and parameter-specific interpretation rather than as isolated units with uniform removal responses.

Water doi: 10.3390/w18121484

Authors: Xia Yu Hao Liu Bingyang Dai Xuran Liu Zilin Mei Chao Ma Chengzhi Yang Mingyu Shao Yanling An

Reservoirs in karst regions exhibit significant carbon sink potential; however, how different reservoir types influence carbon sequestration remains poorly understood. In this study, dual carbon isotopes (δ13C–Δ14C) were applied to trace dissolved organic carbon (DOC) sources in an open reservoir (Aha Reservoir, AHR) and a closed reservoir (Guanshan Lake, GSL) in southwestern China, and to evaluate their carbon sequestration potential. DOC concentrations in GSL were significantly higher than those in AHR (4.14 ± 0.28 mg/L > 3.37 ± 0.30 mg/L) (p < 0.01), along with lower δ13C values (−30.34 ± 0.51‰ < −28.18 ± 0.31‰) and more enriched Δ14C values (−6.94 ± 11.07‰ > −93.74 ± 6.76‰). The δ13C–Δ14C tracing revealed that plants were the primary DOC source for AHR (61 ± 2%), whereas algae dominated DOC sources in GSL (70 ± 2%). Inflow rivers and water retention time (WRT) likely drive differences in DOC sources and concentrations between the two reservoirs. The absence of inflow rivers and the longer WRT in GSL created favorable conditions for algal growth, resulting in substantially higher chlorophyll a (Chl.a) concentrations (103.00 ± 29.87 μg/L > 13.10 ± 3.29 μg/L) and enhanced production of autochthonous DOC through a stronger biological carbon pump (BCP) effect. These conditions further facilitate the formation and accumulation of recalcitrant DOC (RDOC), ultimately increasing DOC concentrations in GSL. Our findings highlight that closed karst reservoirs may represent important yet underappreciated carbon sinks and should receive greater attention in future carbon-sink assessments.

Water doi: 10.3390/w18121483

Authors: Aseem Saxena Sachin Tripathi Abrahan Mora Miguel Ángel López Zavala Hiroaki Furumai Manish Kumar

Groundwater contamination by redox-sensitive elements (RSEs) such as arsenic (As), chromium (Cr), vanadium (V), and selenium (Se) pose a critical challenge in alluvial aquifers, where seasonal hydrological forcing drives dynamic hydrogeochemical and redox conditions. This study investigates the seasonal evolution of groundwater hydrogeochemistry and multi-metal behavior in shallow aquifers of the Mid-Gangetic Plain, India, with particular emphasis on the role of seasonal redox decoupling. Monsoon conditions were dominated by strongly reducing environments (ORP: −150 to −70 mV), predominantly Ca–Mg–SO4 and Na–Cl type facies. Under these conditions, significant correlations among RSEs in particular (As–V, As–Se) indicated coupled mobilization governed by the reductive dissolution of Fe–Mn (oxyhydr)oxides. Monsoon groundwater also exhibited strong associations between RSEs and agronomic indicators (NO3−, SO42−), suggesting the influence of recharge-mediated agricultural inputs on redox-sensitive geochemical processes. In contrast, post-monsoon conditions showed a clear transition to sub-oxic states (ORP up to +121 mV) and were dominated by Ca–Mg–HCO3 facies, accompanied by substantial increases in bicarbonate (~372%), electrical conductivity (~62%), and total dissolved solids (~21%). Despite the partial oxidation of the aquifer system, redox-sensitive metals did not respond uniformly. Instead, inter-element correlations weakened or disappeared, indicating a transition from coupled to decoupled contaminant behavior. Arsenic concentrations increased up to 20.8 µgL−1, whereas Cr and V displayed variable enrichment controlled by alkali-induced desorption and carbonate-mediated surface interactions. This transition reflects seasonal redox decoupling, whereby seasonal redox shifts lead to metal-specific rather than coordinated multi-metal behavior. We propose a Seasonal Redox Decoupling Framework (SRDF) to explain the shift from coupled reductive release during monsoon conditions to selective mobilization pathways in the post-monsoon period. These findings demonstrate that seasonal redox shifts control not only metal concentrations but also inter-element relationships, leading to metal-specific risk profiles. This underscores the need for seasonally adaptive monitoring and management strategies in hydrologically dynamic alluvial aquifers.

Water doi: 10.3390/w18121482

Authors: Xuewen Guan Zhenghua Wang Yubin Chen Yinshan Xu Xiangxing Wei

Traditional reservoir flood control operations in China have long relied on a fixed flood-limited water level (FLWL), which frequently results in the underutilization of water resources during flood seasons. Dynamic FLWL regulation and joint reservoir operation have emerged as core strategies to optimize floodwater resource utilization while ensuring flood control safety. However, these approaches typically treat the flood control storage capacity of individual reservoirs as fixed constraints, failing to consider the potential for reallocating this capacity within a cascade reservoir system. This study explores the concept of “equivalent utilization of flood control storage capacity” among cascade reservoirs. Focusing on the four major reservoirs (Wudongde, Baihetan, Xiluodu, and Xiangjiaba) in the lower reaches of the Jinsha River, a methodology for analyzing the equivalent index of their flood control storage capacity is established. The core of this methodology involves a two-round scheduling simulation under various design flood scenarios. The first round of simulation adheres to standard operating rules, while the second round allows upstream reservoirs to retain additional flood volume—with downstream reservoirs correspondingly reducing their outflow—on the premise that downstream safety targets are satisfied. The equivalent index is defined as the ratio of the reduced storage capacity utilized downstream to the additional storage capacity utilized upstream. Nine design flood scenarios (covering three typical years with 1%, 2%, and 5% exceedance probabilities) for flood control in the Sichuan–Chongqing reach were analyzed, with the tightly coupled Wudongde–Baihetan and Xiluodu–Xiangjiaba reservoir pairs treated as two integrated units. The results indicate that the equivalent indices between these two reservoir groups range from 0.96 to 0.999, demonstrating near-perfect functional interchangeability of their flood control storage capacities for the specified research objective. For practical engineering application, a value of 0.96 is recommended as the lower-bound equivalent index. This study provides a methodological framework and specific index to support the dynamic, coordinated, and more efficient utilization of flood control storage capacity in large-scale cascade reservoir systems.

Water doi: 10.3390/w18121481

Authors: Ignacio J. Petit Jaime Aburto Catalina Sapag Scheila Recabarren Sofía Ramirez-Montero Ana Cinti Alejandro Correa-Rivera Andrés Cádiz Marisol Romero Liesbeth Van der Meer

Marine Protected Areas (MPAs) are key tools for mitigating the impacts of human activities on marine biodiversity and addressing climate change. Consequently, nations worldwide have committed to international targets to expand MPA coverage, leading to a rapid increase in protected areas and generating significant challenges for financing and effective management, particularly in developing countries. Under this scenario, multiple stakeholders, including local communities, academia, governments, and national and international organizations, are joining efforts to reduce financial gaps and strengthen MPA governance and management. In this study, we present the case of the Juan Fernández Archipelago in Chile, where multiple organizations collaborated to develop a socially robust and locally grounded governance system for a network of MPAs through a comprehensive community engagement process conducted on Robinson Crusoe Island between 2022 and 2024. As a result, a Functional Community Organization was established to co-manage the MPAs with the Chilean government, and three MPA management plans encompassing ~580,000 km2 were approved. Among them, the management plan of the Multiple-Use MPA “Mar de Juan Fernández” was the first approved under the new Chilean Biodiversity and Protected Areas Service (Law 21,600), setting a national precedent for co-management. Our findings show that effective MPA governance depends not only on institutional design but also on the extent to which governance arrangements are socially embedded and locally legitimate. In this context, community-grounded and context-sensitive engagement processes facilitated high levels of participation, strengthened representation, and supported the co-production of knowledge, providing a strong foundation for the long-term implementation of conservation objectives.

Water doi: 10.3390/w18121480

Authors: Muhammad Shahid Sami Fida Hussain Ammarah Mushtaq Jalal Shah Sang-Eun Oh Aneela Anwar

Next-generation wastewater treatment and recycling rely on membrane-based processes, but they face a trade-off among permeability, selectivity, and fouling resistance. In the present study, thin-film nanocomposite (TFN) membranes were fabricated by incorporating a ternary TiO2-SiO2-biochar nanofiller into a polysulfone (PSf) support using nonsolvent-induced phase separation, after which m-phenylenediamine and trimesoyl chloride were used via interfacial polymerization to produce a selective polyamide layer. The membrane compositions were M1 (22 wt.% PSf), M2 (22 wt.% PSf/0.5 wt.% TiO2/0.5 wt.% SiO2/0.5 wt.% biochar), and M3 (polyamide-coated M2). FTIR, XRD, SEM, contact-angle, porosity, and mechanical analyses supported successful membrane formation and changes in morphology, wettability, and structural strength after nanofiller incorporation and TFC coating. The addition of a nanofiller increased the hydrophilicity of the membranes by decreasing the water contact angle from 98.6 ± 0.8° for pristine PSf to 35.6 ± 1.5° for the nanocomposite membrane. Consequently, the pure-water permeability increased from 21 to 37 L m−2 h−1 bar−1. After polyamide layer formation, the optimized TFN membrane maintained a contact angle of 55.4 ± 3.8° and achieved a high Congo red rejection of 98% with permeate flux of 7–9 L m−2 h−1 bar−1. The membrane also showed good antifouling performance, with flux recovery ratios exceeding 90%. For heavy-metal-containing solutions, the optimized membrane showed apparent removal efficiencies of 78–98% for multivalent heavy metals (Pb2+, Hg2+, Cd2+, Mn2+, Zn2+, Cu2+, Ni2+, Fe3+, As3+, and Cr6+). Static adsorption tests showed the order M2 > M3 > M1, confirming that exposed TiO2-SiO2-biochar sites contribute to pollutant uptake, while the superior filtration performance of M3 is attributed to the combined effect of the polyamide selective layer and adsorption-assisted interactions. Overall, the TiO2-SiO2-biochar-based TFN membrane provides a promising platform for dye removal and preliminary heavy-metal attenuation from contaminated water.

Water doi: 10.3390/w18121479

Authors: Conor T. Gowan Bailey A. M. Gordon Judy Westrick Shawn P. McElmurry

Ensuring safe and palatable drinking water is critical for long-duration space travel and part of NASA’s 2022 strategic goals. This study investigated whether the formation of iodoform occurred when iodine reacts with trace levels of dissolved organic carbon (DOC) leaching from spacecraft water system components. A simplified model of the International Space Station’s Environmental Control and Life Support System was constructed, focusing on disinfection. The system included water storage in low-density polyethylene (LDPE) bags followed by activated carbon block filtration. Three scenarios were tested: iodine treatment in the storage tank, iodine treatment in-line after storage, and a control with no iodine. Preliminary results showed I2 concentrations of 0.1–5.42 mg/L prior to filtration, which decreased below detection after filtration. DOC concentrations ranged from below detection to 1.1 mg/L. Concentrations of iodoform, determined by gas chromatography–mass spectrometry, were assessed to observe potential risks to spacecraft drinking water quality. Iodine-based disinfection did result in significant iodoform formation or increased leaching of DOC. This study supports that long-term water storage can be achieved using iodine disinfection and LDPE storage. These results also inform the use of iodine disinfection in emergency situations by drinking water managers when water supply is interrupted in disaster situations.

Water doi: 10.3390/w18121478

Authors: Linmin Li

This editorial introduces and synthesizes the contributions included in this Special Issue on advanced numerical methods for multiphase and cavitating flows [...]

Water doi: 10.3390/w18121477

Authors: Robert Galla Hiroshi Ishidaira Jun Magome Kazuyoshi Souma

Flooding is one of the most common and destructive natural disasters worldwide, and projections indicate that its intensity will increase across various climate regions during this century. South Sudan is particularly vulnerable due to a combination of factors, including hydrological releases from Lake Victoria, local rainfall patterns, and wetland retention dynamics. These factors raise important questions regarding the hydrological connectivity between Lake Victoria and the Nile system. This study examined how upstream hydrological conditions impact flood dynamics in South Sudan’s flood-prone regions, specifically in the states of Jonglei and Unity along the River Nile. To statistically estimate flood propagation lag time from Lake Victoria to the Sudd wetland, we used Cyclone Global Navigation Satellite System (CYGNSS) remote sensing data and water-level altimetry from both Lake Victoria and the River Nile at Mangalla. The analytical methods included moving block bootstrap (MBB) cross-correlation and Gaussian process (GP) modeling. Furthermore, we validated the event-based propagation and inundation patterns using flood event reports from the Displacement Tracking Matrix (DTM). The findings indicate that the statistical propagation signals took approximately 106 days during the wet season (95% confidence interval [CI]: 60–150 days) and 134 days during the dry season (95% CI: 75–195 days) for the downstream water level response to reach the River Nile at Mangalla, and 3–4 weeks to reach the adjacent floodplains downstream. Residual stationarity diagnostics showed augmented Dickey–Fuller (ADF) statistics below −7 across the analyzed propagation pathways, indicating statistically stationary lag-adjusted residual behavior. Consistent temporal correspondence between inferred flood arrival windows and independently reported DTM flood-impact periods provides cautious support for the hydrological plausibility of the estimated propagation structure.

Water doi: 10.3390/w18121476

Authors: Mohsen Hajibabaei Robert Sitzenfrei Mohsen Shahandashti Milad Latifi

The effective management and optimization of urban water networks is essential for addressing the growing challenges posed by aging infrastructure, population growth, urbanization, and climate change [...]

Water doi: 10.3390/w18121475

Authors: Milan Stehlík Francisca Rodríguez Silva Andrés Rivera

We study the extreme behavior of six central Chile glacier mass balance series facing significant retreats and ice wastage due to climate variability and change. This has led to reduced meltwater availability in dry seasons, increasing competition for downstream water resources. Understanding glacier mass balances is crucial for predicting future water availability in scenarios with higher water demands. We used Extreme Value Theory tools to analyze the data and identify extreme events. The main objective of this study is to statistically analyze glacier mass losses in Chile, using mass balance data collected from both national and international sources. The results show high heterogeneity in the extreme behavior of glaciers, with some showing an approximately exponential tail (Guanaco Glacier), others exhibiting stability with slight tails (Echaurren Norte and Mocho Glaciers) and one (Amarillo Glacier) with a highly unstable structure. The other analyzed glaciers (Juncal Norte and Juncal Sur) have slight and potentially limited tails. These results confirm the high importance of studying glaciers in the Andes in order to better understand their responses to climate change, an important and relevant aspect for the future management of glacier melt water resources.