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Water, Volume 18, Issue 8 (April-2 2026) – 105 articles

Cover Story (view full-size image): This study presents the authors’ experience in the application of a fully hydrodynamic model over an entire territory, with direct rainfall input (rain-on-grid approach). This way of conducting flood risk analyses provides hydraulic engineering with an advancement in diagnostics similar to the progress that occurred in medicine with the transition from radiography to contrast-enhanced computed tomography. With radiography, the investigation is focused on a specific point where a symptom is already present. Conversely, a full-body contrast-enhanced scan is a much more powerful tool, detecting all parts of the body, including those where risk hotspots remain asymptomatic. In the rain-on-grid approach, the contrast medium is stormwater. The numerical simulation of all possible stormwater paths generates a comprehensive image of the entire territory. View this paper
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23 pages, 2811 KB  
Article
Physical Modeling of Seepage Control Using Upstream Blanket and Cutoff in Earth Dams: A Hele–Shaw Experimental Study
by Ahmed M. Abdelrazek, Mohamed A. Hafez, Abdulrahman Mohammed and Mohammed A. Abourohiem
Water 2026, 18(8), 989; https://doi.org/10.3390/w18080989 - 21 Apr 2026
Cited by 1 | Viewed by 848
Abstract
Seepage beneath earth dams founded on pervious strata can cause excessive under-seepage, elevated downstream exit gradients, and high phreatic levels, thereby increasing susceptibility to internal erosion and piping. This study presents a Hele–Shaw laboratory investigation of seepage-control efficiency for an upstream impervious blanket [...] Read more.
Seepage beneath earth dams founded on pervious strata can cause excessive under-seepage, elevated downstream exit gradients, and high phreatic levels, thereby increasing susceptibility to internal erosion and piping. This study presents a Hele–Shaw laboratory investigation of seepage-control efficiency for an upstream impervious blanket used alone and in combination with a vertical cutoff (blanket–cutoff system). The experimental geometry reproduces a zoned earth dam cross-section at a scale of 1:200. Five foundation thickness ratios (T/B=0.184–1.00) were tested. For the blanket-only system, four blanket length ratios (Lb/B=0.50–1.25) were examined. For the blanket–cutoff system, cutoff depth ratios (S/T=0.20–0.80) were investigated using (i) a representative blanket length Lb/B=0.75 across all foundation depths and (ii) a deep-foundation case T/B=1.00 across all blanket lengths. Seepage discharge, head loss due to seepage-control measures, maximum exit gradient at the downstream toe, and phreatic line location were measured at steady state and expressed in dimensionless form using the equivalent Hele–Shaw hydraulic conductivity. Relative to the no-measure reference case, the upstream blanket reduced dimensionless discharge by 20.8–70.2%, reduced the exit-gradient indicator by 6.4–50.2%, and reduced the downstream seepage-surface height by 58.9–92.8%. Adding a vertical cutoff provided further reductions relative to the blanket-only configuration, up to 34.4% in discharge and to 29.8% in exit-gradient indicator at Lb/B=0.75—while increasing head loss across the upstream control system. Regression-based correlations and main-text design maps are proposed for preliminary sizing. The proposed correlations and design maps are intended for screening-level use only within the tested ranges 0.18 ≤ T/B ≤ 1.00, 0.50 ≤ Lb/B ≤ 1.25, and 0.20 ≤ S/T ≤ 0.80. Because the Hele–Shaw model is a two-dimensional viscous-flow analog of saturated seepage, the results provide a physical basis for relative comparison of seepage-control measures rather than a direct substitute for site-specific analysis of heterogeneous three-dimensional foundations. Accordingly, the agreement discussed in this paper is qualitative and trend-based, and the proposed tools are intended to complement rather than replace quantitative FEM for site-specific design. Full article
(This article belongs to the Special Issue Advances in Hydraulic and Water Resources Research, 4th Edition)
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25 pages, 8407 KB  
Article
Mitigating Peak Edge Effects in Multi-Zone Irrigation: A Safety-Constrained Reinforcement Learning Approach with Short-Term Evapotranspiration Forecasting
by Zhenyu Fu, Chunming Zhang, Xinwei Liu, Jihui Tian and Yu Song
Water 2026, 18(8), 988; https://doi.org/10.3390/w18080988 - 21 Apr 2026
Viewed by 521
Abstract
To address peak edge operation and excessive valve switching in hydraulically coupled multi-zone campus irrigation, this study proposes a collaborative scheduling framework that combines short-term evapotranspiration (ET) forecasting with safety-constrained reinforcement learning. Temperature, relative humidity, and light intensity are used to construct vapor [...] Read more.
To address peak edge operation and excessive valve switching in hydraulically coupled multi-zone campus irrigation, this study proposes a collaborative scheduling framework that combines short-term evapotranspiration (ET) forecasting with safety-constrained reinforcement learning. Temperature, relative humidity, and light intensity are used to construct vapor pressure deficit and radiation proxy features, and a lightweight predictor provides two-hour-ahead ET statistics as forward-looking disturbance information. A safety layer composed of Top-2 gating and total flow projection is then used to map policy outputs into a feasible action space under parallel irrigation and total flow constraints. Using seven consecutive days of field data from October 2025, the proposed method reduced total water consumption to 131.04 m3, corresponding to reductions of 9.13% and 6.12% relative to fixed-schedule and hysteresis threshold rotational irrigation, respectively. It also reduced the maximum total flow from 2.00 to 1.60 L/s, lowered valve switching cycles to 12, and reduced the border ratios at 0.90 and 0.95 to 0. Additional ablation, sensing noise/packet loss, and Top-K extension experiments further showed that ET forecasting improves anticipatory scheduling, whereas safety projection is essential for zero-violation operation. These results demonstrate that the proposed framework provides a practical and deployable solution for safe and water-efficient multi-zone irrigation scheduling under shared pump constraints. Full article
(This article belongs to the Section Water, Agriculture and Aquaculture)
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30 pages, 65437 KB  
Article
Transboundary Aquifer Vulnerability: Modeling Future Groundwater Decline in the Nubian Sandstone Aquifer (Al Kufrah Basin, Libya)
by Abdalraheem Huwaysh, Fadoua Hamzaoui and Nawal Alfarrah
Water 2026, 18(8), 987; https://doi.org/10.3390/w18080987 - 21 Apr 2026
Viewed by 1490
Abstract
Groundwater in arid and semi-arid regions is increasingly stressed by low rainfall, high evaporation, population growth, agricultural expansion, and climate change. A critical question is whether non-renewable aquifers can sustain rising water demand without irreversible decline. This study addresses that question for the [...] Read more.
Groundwater in arid and semi-arid regions is increasingly stressed by low rainfall, high evaporation, population growth, agricultural expansion, and climate change. A critical question is whether non-renewable aquifers can sustain rising water demand without irreversible decline. This study addresses that question for the Al Kufrah Basin in southeastern Libya, part of the Nubian Sandstone Aquifer System, the world’s largest fossil aquifer. A three-dimensional groundwater flow model (MODFLOW-2000) was calibrated using data from more than 1000 production wells and 32 piezometers spanning 1968–2022. The model was applied to simulate groundwater behavior under five scenarios extending to 2050, including the planned development of 150 new wells. The results indicate that over 85% of withdrawals are derived from aquifer storage rather than boundary inflows. While regional water levels remain relatively stable over the 25-year horizon, localized drawdowns of up to 11 m are expected near new well fields. These findings highlight short-term resilience but point to long-term vulnerability, as continued reliance on non-renewable reserves without recharge will ultimately lead to depletion. The study underscores the need for adaptive management, climate-resilient water strategies, and regional cooperation to ensure the sustainable use of this transboundary aquifer under increasing environmental and socio-economic pressures. Full article
(This article belongs to the Special Issue Advances in Extreme Hydrological Events Modeling)
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20 pages, 3471 KB  
Article
Multi-Indicator Assessment of Hydrological Change Across Europe Using Satellite Observations
by Monika Birylo
Water 2026, 18(8), 986; https://doi.org/10.3390/w18080986 - 21 Apr 2026
Viewed by 555
Abstract
Understanding drought and water availability requires integrating multiple components of the hydrological cycle. Satellite observations enable consistent monitoring of water storage, groundwater variability, and water budget components at continental scales. This study synthesises results from several satellite-based analyses to examine hydrological signals across [...] Read more.
Understanding drought and water availability requires integrating multiple components of the hydrological cycle. Satellite observations enable consistent monitoring of water storage, groundwater variability, and water budget components at continental scales. This study synthesises results from several satellite-based analyses to examine hydrological signals across Europe within the Köppen–Geiger climate zones. Indicators were analysed jointly, including the Combined Climatologic Deviation Index (CCDI), Water Budget (WB), Water Storage Deficit Index (WSDI), and Groundwater Drought Index (GDI). The comparison of these indices reveals consistent spatial and temporal patterns of water deficit across Europe, with the strongest drying signals observed in temperate and Mediterranean regions. In contrast, northern climatic zones show higher retention capacity. The integrated approach highlights relationships among groundwater variability, water storage anomalies, climate anomalies, and water budget dynamics, providing a broader perspective on hydrological responses to climate variability. The results demonstrate the value of multi-indicator satellite analysis for large-scale drought monitoring and water resource assessment. Full article
(This article belongs to the Section Hydrology)
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21 pages, 4008 KB  
Article
Estimation of the Mean-to-Surface-Velocity Ratio in Shallow Streams with Rough Beds
by Katerina Mazi, Evangelos Akylas and Antonis D. Koussis
Water 2026, 18(8), 985; https://doi.org/10.3390/w18080985 - 21 Apr 2026
Viewed by 626
Abstract
Estimating in a stream’s cross-section the depth-averaged velocity, V, from the free-surface velocity, vsurf, is an efficient, non-invasive hydrometric method. The ratio fv = V/vsurf is typically assumed constant at fv = 0.86 in field [...] Read more.
Estimating in a stream’s cross-section the depth-averaged velocity, V, from the free-surface velocity, vsurf, is an efficient, non-invasive hydrometric method. The ratio fv = V/vsurf is typically assumed constant at fv = 0.86 in field applications, despite observations to the contrary. Guidance is, therefore, needed in estimating actual fv-ratios when velocity profile data are absent. This work provides field-verified guidance based on the hydromechanics of the logarithmic velocity law, which shows that fv depends on the scaled resistance measure ‘friction length/depth’, yo/h, with the yo(k) function of the equivalent sand grain roughness, k. The mean-to-surface-velocity ratio in rough-bed streams is estimated from the bed roughness and stream morphology by modifying Nikuradze’s equation, yo = k/30, to yo = ck, with c(h/k) ≥ 1/30, and k ≈ D84—data fit: c ≈ 8.61(h/k)−1.821, ~5 ≤ h/k < ~30. Field-verification of the ratio’s modified hydromechanics, fv = fh/yo, with yo(h/k) evaluated from bed roughness estimated by inspection or sieve analysis shows this ratio holding within ~|10|% error for shallow streamflow over a coarse bed of gravels and rocks, giving submergences of ~5 ≤ h/D84 ≤ ~30; yo = k/30 suits large streams with smooth beds (h/k ≥ ~30, fv ≥ ~0.86). Variable roughness-estimated fv-ratios appear to be more reliable than the fixed default, fv(h/yo ≈ 1000) = 0.86. This flow-gauging concept is based on observable physical characteristics of a monitoring cross-section and facilitates the rating of hard-to-access streams draining small basins in ragged upland terrain. Full article
(This article belongs to the Special Issue Rivers, Estuaries, and Coastal Zones: Sediment Transport and Morphodynamical Models: 2nd Edition)
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18 pages, 8162 KB  
Article
Hydrochemical Characteristics, EWQI-Based Water Quality Evaluation, and Health Risk Assessment of Groundwater in the City of the Tibetan Plateau
by Meizhu Zhou, Qi Liu, Zhongyou Yu and Si Wang
Water 2026, 18(8), 984; https://doi.org/10.3390/w18080984 - 21 Apr 2026
Viewed by 734
Abstract
Groundwater plays an indispensable role in daily life. However, with the continuous advancement of industrialization, more attention should be paid to the quality of groundwater and the associated potential health risks in areas surrounding industrial parks. In this study, groundwater samples collected in [...] Read more.
Groundwater plays an indispensable role in daily life. However, with the continuous advancement of industrialization, more attention should be paid to the quality of groundwater and the associated potential health risks in areas surrounding industrial parks. In this study, groundwater samples collected in the city of the Tibetan Plateau during the wet season (WS) and dry season (DS) were analyzed using Piper diagrams, Gibbs diagrams, and correlation analysis. The results elucidated the hydrochemical characteristics, formation mechanisms, and controlling factors of groundwater in the area. Groundwater potability was assessed using the Entropy-weighted Water Quality Index (EWQI) method. In addition, the health risk assessment model was applied to evaluate potential risks for four population groups, with NO3− and F− selected as representative groundwater pollutants. The findings revealed that groundwater in the study zone was typically moderately alkaline and characterized primarily as soft–fresh and hard–fresh. The groundwater in both seasons mainly exhibited HCO3–Ca chemical facies. Water–rock interactions involving silicate and carbonate minerals were identified as key processes controlling the hydrochemical composition in both seasons. EWQI results showed that groundwater quality for drinking purposes was excellent in the seasons. Sensitivity analysis further showed that Cl− exerted the greatest influence on the drinking water quality evaluation in both seasons. Health risk assessments revealed that the risks posed by NO3− and F− to infants, children, adult females, and adult males remained within acceptable limits (with max values of 0.63, 0.39, 0.28, and 0.33 in the WS, and 0.59, 0.36, 0.26, and 0.31 in the DS, respectively). However, infants exhibited greater susceptibility than the other groups across seasons, with a risk index approximately twice that of adults. Overall, the findings contribute valuable insights for the sustainable management and planning of groundwater resources in the study zone. Future research could refine the risk assessment model with localized data and explore mitigation strategies for elevated risks in specific seasons or regions. Full article
(This article belongs to the Topic Water-Soil Pollution Control and Environmental Management)
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23 pages, 337 KB  
Review
From Abiotic Filters to Dynamic Biofilm Reactors for the Treatment of Diffuse Agricultural Pollution: A Comprehensive Review
by Soledad González-Juárez, Nora Ruiz-Ordaz and Juvencio Galíndez-Mayer
Water 2026, 18(8), 983; https://doi.org/10.3390/w18080983 - 21 Apr 2026
Cited by 1 | Viewed by 801
Abstract
Diffuse pollution from agricultural runoff, characterized by intermittent discharges of complex contaminant mixtures, including nutrients, pesticides, and heavy metals (HMs), poses a persistent threat to global water quality. Conventional “end-of-pipe” strategies often fail to address these decentralized, nonpoint sources. This review examines the [...] Read more.
Diffuse pollution from agricultural runoff, characterized by intermittent discharges of complex contaminant mixtures, including nutrients, pesticides, and heavy metals (HMs), poses a persistent threat to global water quality. Conventional “end-of-pipe” strategies often fail to address these decentralized, nonpoint sources. This review examines the evolution of Permeable Reactive Barriers (PRBs) from static, abiotic filters into modern Permeable Reactive Bio-Barriers (PRBBs), engineered as dynamic, fixed-bed biofilm reactors. A key advancement in PRBB efficacy is the exploitation of biofilm plasticity, particularly in response to coexistence with organic and inorganic pollutants. While heavy metals are traditionally viewed as inhibitors, this review synthesizes evidence showing that subinhibitory HM levels can act as structural and functional drivers. These metals induce the upregulation of Extracellular Polymeric Substances (EPSs), creating a “protective shield” that sequesters metals and confers functional resilience on the microbial consortia responsible for nutrient removal and pesticide biodegradation. The review analyzes contaminant removal mechanisms, highlighting the bio-chemo synergy between reactive media and biofilms, and proposes a classification framework based on target contaminants, media, and technological integration. Significant focus is placed on emerging hybrid multi-media systems designed to protect the microbial community from toxic metal shocks, alongside the integration of artificial intelligence for predictive control. While challenges in hydraulic sustainability and field validation remain, PRBBs represent a compact, low-energy, and scalable ecotechnology. PRBBs offer a strategically targeted solution within the Nature-Based Solutions toolkit for building resilient protection of aquatic ecosystems at the critical land-water interface. Full article
(This article belongs to the Special Issue Emerging Contaminants in Water Environments: Occurrence, Analysis and Ecotoxicity)
18 pages, 10323 KB  
Article
Flooding of the Dragone Plain Polje and Its Impacts on the Karst Groundwater Resource (Terminio-Tuoro Massif, Southern Apennines, Italy)
by Saman Abbasi Chenari, Guido Leone, Michele Ginolfi, Libera Esposito and Francesco Fiorillo
Water 2026, 18(8), 982; https://doi.org/10.3390/w18080982 - 21 Apr 2026
Viewed by 552
Abstract
The carbonate massifs of the southern Italian Apennines host extensive karst aquifers, which represent the principal drinking water resources. This study focuses on the Dragone Plain polje, a vast closed karst depression located in the main recharge sector of the Terminio–Tuoro carbonate massif. [...] Read more.
The carbonate massifs of the southern Italian Apennines host extensive karst aquifers, which represent the principal drinking water resources. This study focuses on the Dragone Plain polje, a vast closed karst depression located in the main recharge sector of the Terminio–Tuoro carbonate massif. The polje drains a ~55 km2 endorheic catchment and may be flooded during the cold and wet season, forming a temporary lake. We employed continuous hydroclimatic time series (rainfall, groundwater level, spring discharge, and river level) together with sparse Sentinel-2 true color satellite images for the period 2020–2024 to analyze the flooding process in the polje and its hydraulic connection with the saturated zone of the karst aquifer. Results indicate that lake formation depends on the balance among soil moisture, rainfall intensity, and runoff development, which were modeled on a daily scale. Daily recharge was also estimated and compared with groundwater level time series from the deep karst aquifer. The modeling was integrated with cross-correlation analysis of the time series, providing insights into the propagation of precipitation pulses through the hydrogeological system. This case study represents an important example for understanding the relationship between karst polje hydrological functioning and climate in a Mediterranean area. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: The Impact of Climate Change on Water Resources)
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30 pages, 1925 KB  
Article
Assessment of Soil Physicochemical Changes, Bioaccumulation of Potentially Toxic Elements, and Okra Growth Parameters Under Different Irrigation Systems with Treated Wastewater
by Mohamed Naceur Khelil and Rim Ghrib
Water 2026, 18(8), 981; https://doi.org/10.3390/w18080981 - 20 Apr 2026
Viewed by 926
Abstract
Treated wastewater (TWW) reuse mitigates water scarcity but may induce soil salinization and trace metal accumulation if improperly managed. This field study evaluated the combined effects of irrigation water quality (TWW vs. well water) and irrigation method (surface vs. subsurface drip irrigation, SDI) [...] Read more.
Treated wastewater (TWW) reuse mitigates water scarcity but may induce soil salinization and trace metal accumulation if improperly managed. This field study evaluated the combined effects of irrigation water quality (TWW vs. well water) and irrigation method (surface vs. subsurface drip irrigation, SDI) on soil chemical properties, okra growth, yield, and nutrient/trace element dynamics under semi-arid Mediterranean conditions. Soil pH remained stable across treatments. Electrical conductivity was not significantly affected by water quality but increased in deeper layers under surface drip irrigation, indicating salt migration. SDI promoted more uniform nutrient distribution and favored Na+ displacement toward deeper layers, reducing root-zone exposure. Cations stratified vertically, with Ca2+, Mg2+, and K+ concentrated in surface layers and Na+ at depth. Water quality exerted a stronger influence than irrigation method. The fertilizing effect of TWW significantly enhanced plant height (53%), leaf dry matter (43%), aboveground biomass (81%), and fruit yield (16.3%). When combined with SDI, TWW improved irrigation water use efficiency by 20%. Although fruit Cd concentrations increased under TWW irrigation, all trace metals remained below international food safety standards. These findings indicate that integrating TWW with SDI enhances productivity and water use efficiency while maintaining short-term food safety, though long-term monitoring remains essential. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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19 pages, 14416 KB  
Article
Graphene Oxide-Mediated Sulfur Cycling: A Novel Strategy for Multi-Pathway Autotrophic Nitrogen Removal in the SRAO Bioreactor
by Duyang Yao, Hao Xu, Zhujun Wang, Shilong Tang, Xinyu Yang, Min Wu and Yayi Wang
Water 2026, 18(8), 980; https://doi.org/10.3390/w18080980 - 20 Apr 2026
Viewed by 731
Abstract
Sulfate-reducing ammonium oxidation (SRAO) is an emerging anaerobic autotrophic nitrogen removal process that combines ammonium oxidation with sulfate reduction. However, it faces some challenges, such as the slow growth of autotrophic microorganisms, weak synergistic interaction between different microorganisms, and poor substrate transfer capability. [...] Read more.
Sulfate-reducing ammonium oxidation (SRAO) is an emerging anaerobic autotrophic nitrogen removal process that combines ammonium oxidation with sulfate reduction. However, it faces some challenges, such as the slow growth of autotrophic microorganisms, weak synergistic interaction between different microorganisms, and poor substrate transfer capability. Herein, graphene oxide (GO) was added to a lab-scale bioreactor to promote SRAO reaction, and its effect on nitrogen removal was systematically investigated. The results demonstrated that GO served not only microbial carriers but also electron shuttles, which were conducive to microbial spatial distribution and better electron transfer, improving the sulfur cycle-driven multi-pathway nitrogen removal performance. The addition of 50 mg/L GO not only enhanced the SRAO activity and increased the ammonium removal efficiency by 24.7%, but also reduced the effluent nitrite concentration and promoted nitrogen production. After reaction, the main functional groups on the surface of GO had been changed, and the composite aggregates of microorganisms were formed. Mass balance analysis revealed that SRAO was the dominant pathway, while Anammox and sulfur-autotrophic denitrification (SADN) played complementary roles. Moreover, after adding GO, the relative abundances of Desulfosarcinaceae and Bacillus, which were functional microorganisms in the SRAO reaction, were increased by 35.7% and 58.5%, respectively. This study will provide an in-depth understanding of the mechanisms for nitrogen removal in the SRAO bioreactor. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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3 pages, 818 KB  
Correction
Correction: La Pasta Cordeiro et al. Tracing the Origin of Groundwater Salinization in Multilayered Coastal Aquifers Using Geochemical Tracers. Water 2026, 18, 252
by Mariana La Pasta Cordeiro, Johanna Wallström and Maria Teresa Condesso de Melo
Water 2026, 18(8), 979; https://doi.org/10.3390/w18080979 - 20 Apr 2026
Viewed by 476
Abstract
In the original publication [...] Full article
(This article belongs to the Section Water Quality and Contamination)
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22 pages, 5624 KB  
Article
Multi-Decadal Remote Sensing of Crop Planting Structure and Surface Water Dynamics in the Ningxia Plain: Drivers and Scale-Dependent Responses
by Chao Jiang and Xianfang Song
Water 2026, 18(8), 978; https://doi.org/10.3390/w18080978 - 20 Apr 2026
Cited by 1 | Viewed by 710
Abstract
Crop planting structure adjustments in irrigated agricultural regions alter irrigation and drainage regimes, with potential consequences for regional surface water dynamics. However, the nature and scale dependence of these linkages remain insufficiently understood. This study investigates the spatiotemporal dynamics of crop planting structure [...] Read more.
Crop planting structure adjustments in irrigated agricultural regions alter irrigation and drainage regimes, with potential consequences for regional surface water dynamics. However, the nature and scale dependence of these linkages remain insufficiently understood. This study investigates the spatiotemporal dynamics of crop planting structure and surface water bodies in the Ningxia Plain from 2004 to 2023, and systematically quantifies their scale-dependent coupling mechanisms. Annual crop maps were generated using a Random Forest classifier (Sentinel-2, 2019–2023) and a Transformer-based model applied to multi-source satellite imagery (2004–2018). Surface water bodies were derived from long-term remote sensing datasets covering the full study period. Results show that the agricultural system underwent a pronounced transition toward maize dominance. Maize area expanded by 50.8%, whereas wheat and rice declined by 74.3% and 44.6%, respectively. Crop diversity also decreased, with the Shannon Diversity Index declining from 1.41 to 1.06 in 2023, indicating progressive system simplification. Meanwhile, surface water bodies exhibited a sustained downward trend, decreasing at an average rate of −5.32 km2 per year after 2013 and reaching a minimum in 2022. The Yellow River water surface area also contracted by 14.41% (p = 0.001), indicating a basin-scale reduction in surface water extent. Lake classification results reveal strong scale-dependent hydrological responses. Small lakes (≤18 ha), accounting for 73.2% of lake numbers, are primarily controlled by local irrigation–drainage processes. Medium lakes (18–80 ha) are influenced by both anthropogenic regulation and natural variability. Large lakes (>80 ha), although representing only 4.9% of lake numbers but 62.9% of total water area, are mainly sustained by climatic variability and ecological water supplementation. Principal component analysis explains 84.44% of total variance, highlighting agricultural structural change and irrigation–drainage dynamics as key system drivers. Correlation analysis further reveals strong climate sensitivity of large lakes and the Yellow River (ρ = 0.50, p = 0.031), while small lakes are predominantly influenced by agricultural drainage processes. Overall, crop planting structure affects regional water dynamics through scale-dependent processes, with maize expansion altering irrigation and diversion patterns and local irrigation–drainage processes controlling small water bodies. Full article
(This article belongs to the Section Hydrology)
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17 pages, 1707 KB  
Article
Partial Weir Opening Is Associated with Shifts in Benthic Diatom Diversity and Assemblage Reorganization in a Monsoonal River
by Yong-Jae Kim, Su-Ok Hwang, Byeong-Hun Han and Baik-Ho Kim
Water 2026, 18(8), 977; https://doi.org/10.3390/w18080977 - 20 Apr 2026
Cited by 1 | Viewed by 573
Abstract
Using a coordinated multi-year monitoring dataset collected during the 2020–2024 partial-opening management period, we examined benthic diatom assemblages across the Sejong, Gongju, and Baekje weirs in the Geum River, Republic of Korea. Seasonal surveys at eight stations were used to evaluate spatiotemporal variation [...] Read more.
Using a coordinated multi-year monitoring dataset collected during the 2020–2024 partial-opening management period, we examined benthic diatom assemblages across the Sejong, Gongju, and Baekje weirs in the Geum River, Republic of Korea. Seasonal surveys at eight stations were used to evaluate spatiotemporal variation in water quality and benthic diatom community structure under this hydrological management regime. Annual basin-wide averages showed gradual interannual changes in water quality, including declines in total phosphorus, total nitrogen, chlorophyll-a, turbidity, and biochemical oxygen demand after 2021, accompanied by increased dissolved oxygen. Diatom community indices based on relative-abundance data showed corresponding temporal variation, with decreased dominance and increased Shannon diversity, evenness, and taxon richness. Ordination analyses indicated gradual differentiation between the earlier (2020–2021) and later (2022–2024) monitoring groups within the study period, whereas random forest models showed limited explanatory power and were treated as exploratory. Overall, the results support benthic diatoms as sensitive descriptors of ecological change in flow-regulated monsoonal rivers while underscoring the value of long-term monitoring where true pre-intervention biological baselines are unavailable. Full article
(This article belongs to the Special Issue Diatom Biodiversity and Their Adaptation to Environment Change)
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40 pages, 3172 KB  
Article
Systematic Assessment of Minimum Inter-Event Time Determination Methods and Precipitation Thresholds for Constructing Design-Critical Huff Hyetographs
by Marin Grubišić, Željko Šreng, Jadran Berbić and Tamara Brleković
Water 2026, 18(8), 976; https://doi.org/10.3390/w18080976 - 20 Apr 2026
Viewed by 641
Abstract
The primary processing of high-resolution precipitation records (5 min and shorter) is crucial for constructing dimensionless design hyetographs and identifying design-critical precipitation scenarios for urban drainage systems. A key step in this process is separating continuous precipitation records into individual precipitation events, typically [...] Read more.
The primary processing of high-resolution precipitation records (5 min and shorter) is crucial for constructing dimensionless design hyetographs and identifying design-critical precipitation scenarios for urban drainage systems. A key step in this process is separating continuous precipitation records into individual precipitation events, typically based on minimum inter-event time (MIT) and precipitation amount thresholds. This separation directly influences the subsequent analysis steps and the accuracy of the design hyetographs. Building upon this foundation, this study systematically analyses how different MIT determination methods influence the construction of dimensionless Huff hyetographs in a moderately humid continental climate. Three approaches for defining MIT were examined: a fixed MIT method (1–12 h), an autocorrelation-based method (AC), and a kernel density estimation approach (KDE). The analysis also considers the effects of minimum precipitation thresholds (P = 1, 3, and 5 mm) and precipitation duration classes (all durations and short-duration events with T≤2 h), utilising a continuous 10-year series of 5 min precipitation data. The results demonstrate that the choice of MIT substantially affects the identified precipitation events, duration, total amount, and the median Huff curve’s shape, especially for precipitation types with early and late maximum intensity. Specifically, increasing MIT values produces longer and deeper events with steeper Huff curves, while precipitation thresholds mainly filter weaker events rather than impacting peak intensities. The AC method yields results similar to larger fixed MIT values (≈6–9 h), whereas the KDE method corresponds to shorter separations (≈1–3 h). To unify the assessment of design relevance, a composite design index combining Huff curve slope and short-term peak intensities was introduced. Analysis shows that short-duration convective precipitation with an early maximum is the most critical design scenario. However, late-maximum events (events in which peak intensity occurs in the fourth quartile of storm duration, Type 4) can become equally critical when longer MIT values or autocorrelation-based separation are applied. These findings underscore the importance of a transparent and methodologically consistent definition of precipitation event separation criteria when using dimensionless hyetographs in urban drainage design. Full article
(This article belongs to the Special Issue Changes in Hydrology and Rainfall–Runoff Processes at Watersheds)
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24 pages, 4858 KB  
Article
Reconstructing Shallow River Bathymetry Through Sequence-Based Modeling Approach
by Modestas Butnorius, Timas Akelis, Matas Vaitkevičius, Dominykas Matulis, Andrius Kriščiūnas, Vytautas Akstinas and Rimantas Barauskas
Water 2026, 18(8), 975; https://doi.org/10.3390/w18080975 - 20 Apr 2026
Viewed by 689
Abstract
Hydrological monitoring is crucial for protecting aquatic ecosystems, especially downstream of hydropower plants where water levels can change suddenly and cause the degradation of instream habitats. There are lot of traditional methods used to monitor water levels and river bathymetry, but most of [...] Read more.
Hydrological monitoring is crucial for protecting aquatic ecosystems, especially downstream of hydropower plants where water levels can change suddenly and cause the degradation of instream habitats. There are lot of traditional methods used to monitor water levels and river bathymetry, but most of them rely on in situ measurements. Drone-based remote sensing has received more attention in recent years, with the data in turn processed using CNNs. In this paper, we propose a new sequence-based method that uses multiple frames to expand the available context and compare it to already existing methods, such as Lyzenga, Stumpf, CNN, and SfM. The best performing models within this study end up being SfM and CNN, with the former being more accurate on rivers with clean riverbeds and the latter being the most consistent. The sequence-based model shows promise, and even outperforms CNN, in terms of MAE, on rivers where the same location across multiple views is mapped, achieving the most accurate results across different images. This shows that utilizing multiple views to increase the available context can improve the accuracy of riverine depth estimation based on multispectral visual information. Full article
(This article belongs to the Special Issue Integrating AI and Remote Sensing for Ecohydrological Monitoring and Prediction)
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12 pages, 2011 KB  
Article
Sustainable Removal of Heavy Metals Using Activated Carbon Produced from Durian Skin: Experiments and Advanced Modelling
by Khawla Nasri, Lotfi Sellaoui, Rihab Ghorbali, Felycia Edi Soetaredjo, Najoua Belhadj Mbarek Mkacher, Mohamed Mbarek, Houcine Ghalla, Nour Sghaier, Adrian Bonilla-Petriciolet and Suryadi Ismadji
Water 2026, 18(8), 974; https://doi.org/10.3390/w18080974 - 20 Apr 2026
Viewed by 1078
Abstract
This study reports a mechanistic analysis of Pb2+ and Cu2+ adsorption on activated carbon (AC) obtained from durian skin. Pb2+ and Cu2+ adsorption tests were carried out at 303–323 K and pH 5.5 to interpret the heavy metal—durian skin [...] Read more.
This study reports a mechanistic analysis of Pb2+ and Cu2+ adsorption on activated carbon (AC) obtained from durian skin. Pb2+ and Cu2+ adsorption tests were carried out at 303–323 K and pH 5.5 to interpret the heavy metal—durian skin AC systems. A monolayer model was applied to simulate experimental isotherms and calculate steric and energy parameters. The results indicated that the removal of these target pollutants was a multi-ionic process. The saturation adsorption capacities of this AC improved with increasing aqueous solution temperature, ranging from 81 to 139 mg/g for Pb2+ and from 95 to 180 mg/g for Cu2+ under the tested operating conditions. The calculated interaction energies indicated a physisorption mechanism where oxygenated functional groups played a relevant role. Durian skin AC can be used as an alternative adsorbent for purifying wastewater and industrial streams polluted by heavy metals. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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27 pages, 2500 KB  
Article
Impacts of Livestock Species and Farm Size on Blue Water Productivity and Water Scarcity Footprint of Dairy Farming Sheds in Punjab State (India)
by Hanish Sharma, Ranvir Singh, Inderpreet Kaur, Pranav K. Singh and Katrin Drastig
Water 2026, 18(8), 973; https://doi.org/10.3390/w18080973 - 19 Apr 2026
Viewed by 944
Abstract
A robust analysis of water use in major food production systems is crucial for improving their productivity and sustainability in water-scarce arid and semi-arid regions like Punjab (India) facing the depletion of groundwater resources. This study aimed to assess blue water use and [...] Read more.
A robust analysis of water use in major food production systems is crucial for improving their productivity and sustainability in water-scarce arid and semi-arid regions like Punjab (India) facing the depletion of groundwater resources. This study aimed to assess blue water use and blue water productivity in dairy farming systems across different farm sizes in Punjab. Comprehensive monitoring and assessment of water use over a full year (from July 2022 to June 2023) was conducted on 24 dairy farm sheds in Punjab, revealing significant variability in their blue water use (measured in L per adult animal per day) and blue water productivity quantified as kg of fat- and protein-corrected milk (FPCM) produced per m3 of the blue water consumed. The variability was influenced by factors such as livestock species, farm size (medium with 15–25 livestock, large with 25–100 livestock, and commercial with >100 livestock), bathing and servicing routines, and energy use patterns. The average dairy livestock total blue water consumption varied from 112 ± 14 to 131 ± 19 L per adult animal per day, with 20–40% higher livestock drinking water and about six times higher livestock bathing and serving water used during the summer months. Interestingly, a large share (45%) of the average total blue water consumption is contributed by indirect water consumption via the use of energy (electricity and diesel) in dairy farm sheds. Dairy milk blue water productivity was quantified higher, ranging from 154 ± 11 to 225 ± 59 kg FPCM per m3 in buffalo- and crossbred cattle-based dairy farm sheds. However, indigenous cattle showed a lower blue water productivity ranging from 56 to 97 kg FPCM per m3, reflecting their lower milk yields and limited use of intensified management practices. The state-level water scarcity footprint (WSF) of Punjab dairy farm sheds was quantified at 4870 million m3 world-eq, which showed a significant spatial variation among Punjab districts. However, the results of this study offer novel seasonally and spatially disaggregated benchmarks of blue water consumption, blue water productivity, and the water scarcity footprint of Punjab’s dairy farming sheds. This new information is crucial for the development of locally calibrated and validated models for improving the water productivity and sustainability of dairy farming across Punjab and other similar arid and semi-arid regions in Southeast Asian countries. Full article
(This article belongs to the Special Issue Climate Change Adaptation and Water Governance)
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14 pages, 2764 KB  
Article
Dissolved Inorganic Carbon Cycling in Karst Groundwater of Semi-Arid Regions: A Case Study from the Liulin Spring System, North China
by Zhenxing Jia, Hongfei Zang and Zhenxing Wang
Water 2026, 18(8), 972; https://doi.org/10.3390/w18080972 - 19 Apr 2026
Viewed by 689
Abstract
Investigating the cycling characteristics of dissolved inorganic carbon (DIC) in karst groundwater within arid and semi-arid regions is crucial for understanding its role in the global carbon cycle and its contribution to atmospheric carbon sinks. This study is centered on the Liulin Spring [...] Read more.
Investigating the cycling characteristics of dissolved inorganic carbon (DIC) in karst groundwater within arid and semi-arid regions is crucial for understanding its role in the global carbon cycle and its contribution to atmospheric carbon sinks. This study is centered on the Liulin Spring area of North China, based on sampling data from April 2019. We employed hydrogeochemical analysis and environmental isotopic tracing methods to (1) characterize the spatial distribution of DIC along the groundwater flow path; (2) elucidate the sources of HCO3−; (3) calibrate groundwater 14C ages. Results indicate that the HCO3− concentration initially increases and then decreases along the flow path, peaking in the spring discharge zone. Conversely, δ13C values initially decrease and then increase, reaching a minimum in the discharge zone, exhibiting a negative correlation with the HCO3− concentration. The contribution of soil/biogenic CO2 dissolution to HCO3− ranges from 26% to 62%, with the highest values (56–62%) observed in recharge, runoff, and discharge zones and lower values (26–49%) observed in stagnant zones; this contribution generally decreases towards the western boundary. Calibrated 14C ages are significantly reduced and align better with expected groundwater dynamics. Full article
(This article belongs to the Section Hydrogeology)
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17 pages, 6524 KB  
Article
Chitosan Aerogel Composited with Cu-Functionalized UiO-66-NO2 as Recyclable Adsorption of Primary Aromatic Amines in Wastewater
by Chenyang Meng, Zhongxi Lu, Gengli Huang and Zhouping Wang
Water 2026, 18(8), 971; https://doi.org/10.3390/w18080971 - 19 Apr 2026
Viewed by 777
Abstract
Primary aromatic amines (PAAs), such as 4,4′-methylenedianiline (MDA) and 4-chloroaniline (4-CA), are toxic, carcinogenic, and persistent pollutants widely detected in aquatic environments. To address this issue, UiO-66 was modified through nitro functionalization, copper doping, and defect regulation, and further integrated with chitosan (CS) [...] Read more.
Primary aromatic amines (PAAs), such as 4,4′-methylenedianiline (MDA) and 4-chloroaniline (4-CA), are toxic, carcinogenic, and persistent pollutants widely detected in aquatic environments. To address this issue, UiO-66 was modified through nitro functionalization, copper doping, and defect regulation, and further integrated with chitosan (CS) to construct a composite aerogel (CS@CuUiO-66-NO2) for the removal of MDA and 4-CA from wastewater. The adsorbent demonstrated relatively fast adsorption kinetics (MDA: 6 h; 4-CA: 4 h) and high adsorption capacities (MDA: 643.74 mg·g−1; 4-CA: 491.54 mg·g−1), showing improved performance compared to pristine UiO-66 and many previously reported adsorbents under similar conditions. The enhanced adsorption performance is likely attributed to the synergistic effects of multiple interactions, including hydrogen bonding, π-π interactions, and possible coordination interactions between functional groups of the adsorbent and PAAs. Moreover, the adsorbent maintained good adsorption performance after five adsorption–desorption cycles, with only a slight decrease in efficiency (~8%), and exhibited limited interference from coexisting anions. Overall, this study presents a feasible strategy for designing porous composite adsorbents with favorable reusability for potential applications in aqueous pollutant remediation. Full article
(This article belongs to the Special Issue Adsorption Technology in Water and Wastewater Treatment)
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15 pages, 2540 KB  
Article
Delineating the Role of Direct and Indirect Photolysis on Trichloroacetaldehyde (TCAL) and Dichloroacetonitrile (DCAN) in Water Degradation by Ultraviolet Irradiation
by Kiattisak Nakboon, Jenyuk Lohwacharin and On-anong Larpparisudthi
Water 2026, 18(8), 970; https://doi.org/10.3390/w18080970 - 19 Apr 2026
Viewed by 532
Abstract
Haloacetaldehydes (HALs) and haloacetonitriles (HANs) are groups of carcinogenic disinfection by products (DBPs) present in water supplies, of which trichloroacetaldehyde (TCAL) and dichloroacetonitrile (DCAN) are frequently detected. The efficiency of ultraviolet (UV) irradiation processes in the removal of DBPs depends strongly on the [...] Read more.
Haloacetaldehydes (HALs) and haloacetonitriles (HANs) are groups of carcinogenic disinfection by products (DBPs) present in water supplies, of which trichloroacetaldehyde (TCAL) and dichloroacetonitrile (DCAN) are frequently detected. The efficiency of ultraviolet (UV) irradiation processes in the removal of DBPs depends strongly on the contribution of direct and indirect photolysis. Significant gaps exist in research regarding kinetics of photodegradation in multi-solute systems. Therefore, in this study the efficiency of vacuum UV (VUV) and UV-C processes was tested on batch photodegradation with synthetic waters containing either TCAL or DCAN and bi-solutes. A radical scavenger test was performed to determine the presence of OH radicals. The VUV (185 + 254 nm) degraded TCAL and DCAN more effectively than UV-C (254 nm), achieving absolute elimination after 30 min (>99.9%, 113 mW/cm2) for TCAL, but only an 84% reduction in DCAN after 120 min of irradiation at fluence of >450 mW/cm2. The experimental results demonstrate that the main mechanism in TCAL reduction was indirect photolysis, but for DCAN it was direct photolysis by VUV photolysis. When indirect photolysis dominated, HALs and HANs in the mixture competed for OH radicals under VUV photolysis. A degradation pathway study indicated that TCAL was degraded and transformed to formic acid, while DCAN was dechlorinated by OH radicals. Overall, this study confirms that the VUV process is more effective than UV-C in photodegrading carbonaceous DBPs. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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26 pages, 6310 KB  
Article
Hydrochemical Characterization and Origins of Groundwater in the Semi-Arid Batna Belezma Region Using PCA and Supervised Machine Learning
by Zineb Mansouri, Abdeldjalil Belkendil, Haythem Dinar, Hamdi Bendif, Anis Ahmad Chaudhary, Ouafa Tobbi and Lotfi Mouni
Water 2026, 18(8), 969; https://doi.org/10.3390/w18080969 - 19 Apr 2026
Cited by 1 | Viewed by 833
Abstract
In the semi-arid Batna Belezma region of northeastern Algeria, groundwater is a vital resource for agriculture and drinking water. However, the climate leads to intense evaporation, which affects its quality. This study aims to identify the key hydrogeochemical processes that control groundwater composition [...] Read more.
In the semi-arid Batna Belezma region of northeastern Algeria, groundwater is a vital resource for agriculture and drinking water. However, the climate leads to intense evaporation, which affects its quality. This study aims to identify the key hydrogeochemical processes that control groundwater composition in the Merouana Basin and to evaluate the predictive performance of machine learning (ML) models. A total of 30 groundwater samples were analyzed using multivariate statistical techniques, including Principal Component Analysis (PCA), and were modeled using PHREEQC to assess mineral saturation states. Additionally, ML-based regression models, including K-Nearest Neighbors (KNN), Support Vector Machine (SVM), Random Forest (RF), and Extreme Gradient Boosting (XGB),were employed to predict groundwater chemistry. The results indicate that the dominant ion distribution follows the following trend: Ca2+ > Mg2+ > Na+ and HCO3− > SO42− > Cl−. Alkaline earth metals (Ca2+ and Mg2+) constitute the major fraction of total dissolved cations, reflecting carbonate equilibrium and dolomite dissolution processes. In contrast, Na+ represents a smaller proportion of the cationic load; however, its hydro-agronomic significance is substantial due to its influence on sodium adsorption ratio (SAR) and soil permeability. The PHREEQC modeling showed that calcite and dolomite precipitation promote evaporite dissolution, while most samples remain undersaturated with respect to gypsum. The PCA results reveal high positive loadings of Mg2+, Cl−, SO42−, HCO3−, and EC, suggesting that ion exchange and seawater mixing are the primary controlling processes, with carbonate weathering playing a secondary role. To enhance predictive assessment, several supervised machine learning models were tested. Among them, the Random Forest model achieved the highest predictive performance (R2 = 0.96) with low RMSE and MAE values, confirming its robustness and reliability. The results indicate that silicate weathering and mineral dissolution are the primary mechanisms governing groundwater chemistry. The integration of multivariate statistics and machine learning provides a comprehensive understanding of groundwater evolution and offers a reliable predictive framework for sustainable water resource management in semi-arid environments. Geochemical model performance showed a high global accuracy (GPI = 0.91), confirming a strong agreement between observed and simulated chemical data. However, the HH value (0.81) indicates some discrepancies, particularly for specific ions or extreme conditions. Full article
(This article belongs to the Special Issue Water Supply System Reliability, Resilience, Safety and Risk Modelling & Assessment, 3rd Edition)
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26 pages, 22374 KB  
Article
Spatio-Temporal Evolution and Associated Factors of Water Retention in Huaihe River Economic Belt
by Wanling Zhu, Jinshan Hu, Yuanzhi Cao, Tao Peng, Qingxiang Mo, Xue Bai and Tianxiang Gao
Water 2026, 18(8), 968; https://doi.org/10.3390/w18080968 - 18 Apr 2026
Viewed by 556
Abstract
As a critical link between regional economic development and ecological security, understanding the dynamics of water retention is essential for sustainable water resource management in the Huaihe River Economic Belt. This study explores the spatio-temporal evolution and spatial explanatory factors of water retention [...] Read more.
As a critical link between regional economic development and ecological security, understanding the dynamics of water retention is essential for sustainable water resource management in the Huaihe River Economic Belt. This study explores the spatio-temporal evolution and spatial explanatory factors of water retention across five temporal snapshots (2003, 2008, 2013, 2018, and 2023). Based on the InVEST model, we assessed water retention capacity at both grid and spatial development levels, thereby obtaining the retention characteristics of different land-use types and their responses to land-use transitions. Furthermore, a parameter-optimized geographical detector was employed to quantify the relative contributions of climatic-environmental and social-economic factors to the spatial variance of the modeled water retention index. Results indicate that the total water retention capacity exhibited significant interannual fluctuations, with the net capacity in 2023 being lower than the initial level in 2003. Retention values displayed obvious spatial heterogeneity, with high levels concentrated in the southwest and north and low levels distributed in the central area, closely mirroring precipitation distribution. While forest land exhibited the strongest unit water retention capacity, cropland contributed the most to the total volume (50.49%) due to its predominant areal proportion (73.92%). Notably, the conversion of forest to cropland was spatially associated with the most substantial loss in the modeled retention capacity. Soil saturated hydraulic conductivity and land-use type were identified as the dominant factors explaining the spatial variance of water retention. These findings underscore the methodological utility of coupling the InVEST model with a parameter-optimized geographical detector. For practical ecosystem management, the results suggest that spatial planning policies should strictly limit the conversion of ecological lands to agricultural use and prioritize targeted soil hydrological improvements in the central plains to secure long-term water resources. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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31 pages, 7341 KB  
Article
Primary Disruptions of Extreme Storms and Floods on Critical Entities Under the Framework of the CER EU Directive: The Case of Storm Daniel in Greece
by Michalis Diakakis, Vasiliki Besiou, Dimitris Falagas, Aikaterini Gkika, Petros Andriopoulos, Andromachi Sarantopoulou, Georgios Deligiannakis and Triantafyllos Falaras
Water 2026, 18(8), 967; https://doi.org/10.3390/w18080967 - 18 Apr 2026
Viewed by 930
Abstract
The growing complexity of human systems and the increasing frequency of climate-driven hazards have transformed some disasters from isolated events into cascading phenomena which propagate through critical infrastructure networks, disrupting essential services and amplifying systemic risk. This work examines the impacts of extreme [...] Read more.
The growing complexity of human systems and the increasing frequency of climate-driven hazards have transformed some disasters from isolated events into cascading phenomena which propagate through critical infrastructure networks, disrupting essential services and amplifying systemic risk. This work examines the impacts of extreme storms and subsequent flooding on critical entities as defined under the new EU Directive (Critical Entities Resilience, CER). This study introduces a structured Critical Entities Disruption Database—Greece (CEDD-GR), as a methodological framework for systematically recording and analysing disruptions to critical entities, and applies it to the case of Storm Daniel (2023), one of the most severe flood events recorded in Greece. The analysis identified direct impacts across eight of the eleven sectors defined in the CER Directive, namely, energy, transport, health, drinking water, wastewater, public administration, digital infrastructure and food production, processing and distribution. A total of 21 different types of critical entities were documented, revealing the mechanisms through which failures affected different subsectors. The results underscore the systemic fragility of critical entities when exposed to extreme storms, compound flooding, and mass wasting processes (landslides, ground subsidence) and highlight the need for integrated resilience planning in line with the CER framework. Full article
(This article belongs to the Section Hydrology)
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22 pages, 1116 KB  
Review
Microbial Electrochemical Technologies in Wastewater Treatment: Scale-Up Challenges, Pilot Testing, and Practical Implementation
by Thobeka Pearl Makhathini
Water 2026, 18(8), 966; https://doi.org/10.3390/w18080966 - 18 Apr 2026
Cited by 6 | Viewed by 1319
Abstract
Microbial electrochemical technologies (METs) have emerged as promising approaches for coupling wastewater treatment with energy and resource recovery. Considerable progress has been made in elucidating extracellular electron transfer, biofilm behavior, and electrode development, enabling laboratory systems to achieve high removal efficiencies under controlled [...] Read more.
Microbial electrochemical technologies (METs) have emerged as promising approaches for coupling wastewater treatment with energy and resource recovery. Considerable progress has been made in elucidating extracellular electron transfer, biofilm behavior, and electrode development, enabling laboratory systems to achieve high removal efficiencies under controlled conditions. Despite these advances, implementation in real treatment infrastructure remains limited. This review evaluates the progression of METs from laboratory studies to pilot-scale and field applications within the wider landscape of electrochemical wastewater treatment. The effects of reactor setup, material strength, and operational difficulty on performance at different scales are emphasized. Evidence from recent pilots consistently shows reduced energy recovery, along with challenges such as internal resistance, mass-transfer constraints, fouling, and cathode degradation. Laboratory-scale MFC systems have reported peak power densities of up to 23,000 mW/m2 and normalized energy recoveries of up to 1.2 kWh/kg COD removed under optimized, controlled conditions; however, pilot-scale systems typically recover only 0.01–0.05 kWh/kg COD removed, representing one to two orders of magnitude below laboratory-reported values. This contrast underscores the persistent gap between controlled experimental performance and operational reality. Proposed solutions, such as modular scale-out, membrane simplification, and the use of low-cost, replaceable materials, are assessed based on their maturity and practical applicability. Techno-economic and life-cycle analyses indicate that component longevity and integration strategy are often more decisive than peak electrochemical output. METs are therefore most likely to provide near-term benefits in hybrid or niche applications rather than as standalone replacements. Advancement toward wider implementation will require standardized metrics, long-term demonstrations, and engineering designs prioritizing robustness and maintainability. Full article
(This article belongs to the Special Issue Electrochemical Technology for Wastewater Treatment: Challenges and Solutions)
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31 pages, 4793 KB  
Systematic Review
Evaluating Pollutant Removal Performance of Biofiltration Systems for Urban Stormwater Management: A Systematic Literature Review
by Gettie Ezolestine Shiinda, Louise Ann Fletcher, Martin Robert Tillotson and Maryam Asachi
Water 2026, 18(8), 965; https://doi.org/10.3390/w18080965 - 18 Apr 2026
Cited by 1 | Viewed by 1007
Abstract
Rapid urbanisation and climate-induced extreme weather events have intensified urban stormwater runoff challenges. Biofiltration systems have emerged as effective, sustainable urban drainage solutions for mitigating these impacts. A total of 78 peer-reviewed studies were assessed to synthesise findings on how design parameters influence [...] Read more.
Rapid urbanisation and climate-induced extreme weather events have intensified urban stormwater runoff challenges. Biofiltration systems have emerged as effective, sustainable urban drainage solutions for mitigating these impacts. A total of 78 peer-reviewed studies were assessed to synthesise findings on how design parameters influence pollutant removal performance in biofiltration systems treating urban stormwater runoff. Peer-reviewed articles published from 1 January 1995 to 3 June 2025 were retrieved from Scopus and Web of Science (WoS). Non-peer-reviewed, non-empirical, incomplete, or non-relevant studies were excluded. Rigorous application of a standardised review protocol and predefined criteria was employed to mitigate bias. The findings reveal high removal efficiencies for certain trace metals, ammonium, Escherichia coli (E. coli), hydrocarbons, and microplastics, with inconsistent removal for total nitrogen, nitrates, and phosphorus. The primary pollutant removal mechanisms were adsorption, ion exchange with select media, and denitrification in saturated zones. Only 22% of the reviewed studies incorporated a saturated zone, while 18% included a protective surface layer, despite both design elements being associated with improved pollutant removal performance. Variations in media composition and stormwater quality limit comparability across studies. This review highlights the need for context-specific design guidance and further exploration of multi-functional media to enhance multi-pollutant removal. Full article
(This article belongs to the Section Urban Water Management)
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33 pages, 3914 KB  
Article
Interpreting Satellite Rainfall Bias Correction Through a Rainfall–Runoff Framework in a Monsoon-Influenced River Basin: The Phetchaburi River Basin, Thailand
by Jutithep Vongphet, Thirasak Saion, Ketvara Sittichok, Songsak Puttrawutichai, Chaiyapong Thepprasit, Polpech Samanmit, Bancha Kwanyuen and Sasiwimol Khawkomol
Water 2026, 18(8), 964; https://doi.org/10.3390/w18080964 - 18 Apr 2026
Viewed by 655
Abstract
Accurate rainfall information is essential for rainfall–runoff modeling in monsoon-influenced basins, where pronounced spatial variability and limited gauge coverage introduce significant uncertainty. Satellite precipitation products provide spatially continuous estimates but are affected by systematic biases, and improvements in statistical rainfall accuracy do not [...] Read more.
Accurate rainfall information is essential for rainfall–runoff modeling in monsoon-influenced basins, where pronounced spatial variability and limited gauge coverage introduce significant uncertainty. Satellite precipitation products provide spatially continuous estimates but are affected by systematic biases, and improvements in statistical rainfall accuracy do not necessarily translate into hydrologically consistent model forcing. This study interpreted satellite rainfall bias correction through a rainfall–runoff framework in the Phetchaburi River Basin, Thailand, using the DWCM-AgWU hydrological model. Simulations were driven by gauge observations and multiple satellite-based rainfall products (GSMaP, CMORPH, CHIRPS, and PERSIANN-CCS), with bias correction applied using Linear Scaling and Quantile Mapping under rainfall-specific calibration. Results showed that bias correction significantly modified rainfall characteristics in distinct ways. Linear Scaling primarily preserved temporal and spatial structure while adjusting rainfall magnitude, whereas Quantile Mapping improved the distributional representation of rainfall intensities. These differences propagated through hydrological processes, leading to systematic variations in runoff responses across multiple metrics, including water balance consistency, peak magnitude, and timing errors. This suggests that each method performs differently depending on the aspect of system response. Rather than identifying a universally optimal method, the findings highlight trade-offs in how rainfall correction strategies influence hydrological system response. Runoff behavior is interpreted as a process-level indicator of rainfall representation, emphasizing that hydrological consistency depends not only on rainfall accuracy but also on its interaction with model structure. These results suggest a process-oriented perspective for interpreting the role of satellite rainfall products in regulated and monsoon-affected basins. Full article
(This article belongs to the Section Hydrology)
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21 pages, 2487 KB  
Article
Hybrid Conv1D–LSTM Modelling of Short-Term Reservoir Water-Level Dynamics for Scenario-Based Operational Analysis
by Jelena Marković Branković, Milica Marković and Bojan Branković
Water 2026, 18(8), 963; https://doi.org/10.3390/w18080963 - 18 Apr 2026
Cited by 1 | Viewed by 646
Abstract
Accurate representation of short-term reservoir water-level dynamics is essential for operational analysis and scenario-based assessment under prescribed inflow–outflow conditions. In many practical applications, physically based modelling is limited by incomplete process knowledge, unavailable boundary conditions, or insufficient temporal resolution of input data. This [...] Read more.
Accurate representation of short-term reservoir water-level dynamics is essential for operational analysis and scenario-based assessment under prescribed inflow–outflow conditions. In many practical applications, physically based modelling is limited by incomplete process knowledge, unavailable boundary conditions, or insufficient temporal resolution of input data. This study presents a data-driven framework for hourly conditional simulation of reservoir water level based on a hybrid Conv1D–LSTM architecture. The model learns nonlinear relationships among hydraulic forcing, operational control, and system state from historical observations, and is evaluated in a recursive multi-step simulation (rollout) mode to reflect its intended use and capture error accumulation over time. A systematic analysis of input sequence length and activation function is performed to identify a robust model configuration. On the test set, the selected configuration (L = 24, GELU) achieved RMSE = 0.1057 m, MAE = 0.0881 m, and R2 = 0.972 in rollout evaluation. The proposed framework is designed for scenario-based simulation rather than one-step deterministic forecasting, enabling rapid operational screening of alternative inflow–outflow regimes. Unlike many previous studies that emphasize one-step predictive accuracy, this work explicitly assesses model stability in recursive multi-step simulation, which is more relevant for reservoir scenario analysis. Full article
(This article belongs to the Section New Sensors, New Technologies and Machine Learning in Water Sciences)
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19 pages, 12167 KB  
Article
Evaluation of Hydrochemical Characteristics and Irrigation Suitability of Mine Water from the Feicheng Coal Mine
by Dejun Lian, Lei Ma, Ying Su, Baoxing Zhang, Xinxiu Liu, Qing Yang, Yingquan Wang, Man Mei, Yiming Hu, Zongjun Gao and Jiutan Liu
Water 2026, 18(8), 962; https://doi.org/10.3390/w18080962 - 18 Apr 2026
Viewed by 450
Abstract
For the purpose of investigating the hydrochemical signatures and formation processes of mine water at the Feicheng Coal Mine, a total of 61 samples, including fifth limestone water (FLW), old goaf water (OGW), and ordovician limestone water (OLW), were collected and examined via [...] Read more.
For the purpose of investigating the hydrochemical signatures and formation processes of mine water at the Feicheng Coal Mine, a total of 61 samples, including fifth limestone water (FLW), old goaf water (OGW), and ordovician limestone water (OLW), were collected and examined via statistical and hydrochemical approaches. The assessment of mine water suitability for irrigation employed sodium percentage (Na%), sodium adsorption ratio (SAR), permeability index (PI), and magnesium hazard ratio (MHR). The mine water proves slightly alkaline, featuring Na+ as the leading cation and SO42−/HCO3− as the leading anions. By average concentration, cations decrease in the order Na+ > Ca2+ > Mg2+, and anions decrease as SO42− > HCO3− > Cl−. The hydrochemical types of OLW and FLW samples were primarily Ca-HCO3 and Ca-Mg-Cl, whereas the OGW samples were predominantly of the Na-Cl-SO4 and Na-HCO3 types. Rock weathering serves as the main control on water chemistry, with hydrochemical components sourced largely from evaporite and carbonate dissolution. The sodium present in the water is likely attributable to silicate mineral dissolution or cation exchange processes. Cation exchange, with forward exchange dominant, is also a key hydrogeochemical process in the study area. SI results reveal that calcite and dolomite have reached saturation, while gypsum and halite remain undersaturated and tend to dissolve further. Irrigation suitability assessments indicate that most of the water quality in the Feicheng Coal Mine is excellent or good. A limited number of samples exhibited relatively high salinity, and most of them can be directly irrigated. To this end, this study proposes targeted treatment solutions, thus facilitating mine water development and utilization. Full article
(This article belongs to the Topic Advances in Hydrogeological Research)
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51 pages, 7241 KB  
Review
Artificial Sweeteners as Emerging Environmental Pollutants: Global Research Trends, Environmental Behavior, and Future Perspectives
by Setyo Budi Kurniawan, Nor Sakinah Mohd Said, Faiza Salsabilla, Bieby Voijant Tangahu and Muhammad Fauzul Imron
Water 2026, 18(8), 961; https://doi.org/10.3390/w18080961 - 18 Apr 2026
Cited by 2 | Viewed by 1408
Abstract
Artificial sweeteners have emerged as contaminants of increasing concern due to their widespread consumption, environmental persistence, and resistance to conventional wastewater treatment. This review provides an integrated assessment of global research trends and the environmental behavior of major artificial sweeteners, including sucralose, acesulfame [...] Read more.
Artificial sweeteners have emerged as contaminants of increasing concern due to their widespread consumption, environmental persistence, and resistance to conventional wastewater treatment. This review provides an integrated assessment of global research trends and the environmental behavior of major artificial sweeteners, including sucralose, acesulfame potassium, saccharin, and aspartame. Bibliometric analysis of SCOPUS-indexed publications reveals rapid growth in research since 2010, with key themes focusing on environmental occurrence, treatment technologies, and ecotoxicological effects. These compounds are frequently detected in wastewater effluents, surface waters, groundwater, and even drinking water systems, driven by their high solubility and limited biodegradability. Their persistence raises concerns regarding ecological impacts, including potential alterations to microbial communities and aquatic organisms. In addition, emerging evidence suggests potential human health implications, including gut microbiota disruption, metabolic effects, and risks associated with chronic low-dose exposure, although these remain poorly understood. The performance of existing treatment technologies, including biological processes, adsorption, advanced oxidation, and membrane filtration, is critically evaluated, highlighting limitations in complete removal and in the formation of transformation products. Future research should prioritize sustainable treatment strategies, comprehensive risk assessment, and improved monitoring frameworks to better address both environmental and human health risks associated with artificial sweeteners. Full article
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25 pages, 6970 KB  
Article
Dominant Factor Analysis and Threshold Inflection Point Determination in Deep Learning-Based SWAT-LSTM Training Models with SHAP Interpretability Analysis
by Jiake Tian, Jun Zhang, Jianjie Tong, Huaxiang He, Ruidan Gu and Fenjie Shang
Water 2026, 18(8), 960; https://doi.org/10.3390/w18080960 - 17 Apr 2026
Viewed by 643
Abstract
Climate change has intensified extreme hydrological risks, particularly in basins characterized by frequent seasonal streamflow interruptions and discontinuous hydrological records, where traditional process-based models exhibit limited capability for adaptive water resource management. This study develops a hybrid SWAT-LSTM framework that integrates SWAT-derived hydrological [...] Read more.
Climate change has intensified extreme hydrological risks, particularly in basins characterized by frequent seasonal streamflow interruptions and discontinuous hydrological records, where traditional process-based models exhibit limited capability for adaptive water resource management. This study develops a hybrid SWAT-LSTM framework that integrates SWAT-derived hydrological variables with meteorological factors and applies SHAP interpretability analysis to quantify dominant drivers and identify threshold inflection points of runoff variability. Using the upper and middle reaches of the Huolin River Basin as a case study, the coupled model outperformed the standalone SWAT model during the test period (NSE: 0.876 vs. 0.710; R2: 0.884 vs. 0.736) and more accurately reproduced extreme flood and drought events. Future projections (2026–2100), driven by the optimized FGOALS-g3 climate model under SSP2-4.5 and SSP5-8.5 scenarios, indicate increasing precipitation, accelerated minimum temperature rise, and a non-stationary runoff pattern characterized by a mid-century decline followed by a late-century increase. The SHAP results reveal strengthened meteorological dominance, particularly for precipitation and minimum temperature, while soil moisture, evapotranspiration, and percolation remain key hydrological controls. The upward shift in the minimum temperature threshold reflects strengthened temperature control on runoff dynamics under warming. The proposed framework improves extreme runoff prediction and provides a quantitative basis for climate-adaptive basin management. Full article
(This article belongs to the Section Ecohydrology)
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