Water

20 pages, 1275 KiB

Open AccessArticle

Early-Time Recession Solution from a Steady-State Initial Condition for the Horizontal Unconfined Aquifer

by Elias Gravanis, Evangelos Akylas and Ernestos N. Sarris

Water 2025, 17(5), 771; https://doi.org/10.3390/w17050771 - 6 Mar 2025

Viewed by 424

In this work, we present the semi-analytical solution for the early-time recession phase of the horizontal unconfined aquifer of finite length for steady-state initial conditions. This is a case where self-similarity arguments are not applicable. The solution is built as linear perturbations from [...] Read more.

In this work, we present the semi-analytical solution for the early-time recession phase of the horizontal unconfined aquifer of finite length for steady-state initial conditions. This is a case where self-similarity arguments are not applicable. The solution is built as linear perturbations from the initial steady state. The solution is determined via a Sturm–Liouville eigenvalue problem, which should be solved numerically. On the other hand, the immediate response of the aquifer to the sudden switching off the recharge, i.e., in the earliest times, is obtained by deducing analytically the large eigenvalue asymptotic solutions of the problem. We find analytically that in this time regime, the outflow Q is given by Q = Q₀ − 1.4Q₀^5/3L^−4/3n^−2/3t^2/3, where Q₀ is the initial outflow rate, L is the length of the aquifer, n is the porosity of the formation and t is the time from the start of the recession. The stated result is very accurate for times t up to ~0.01 nL^3/2k^−1/2Q₀^−1/2, where k is the hydraulic conductivity of the formation. The analytical and quantitative relation of the presented solution with the classical recession phase asymptotic solutions derived in the past by Polubarinova (early-time solution) and Boussinesq (separable, late-time solution) is discussed in detail. The presented results can be used as a benchmark solution for modeling or numerical validation purposes. Full article

(This article belongs to the Special Issue Geotechnical and Underground Engineering Problems Caused by Water Action)

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20 pages, 4857 KiB

Open AccessArticle

Analysis of Precipitation Change and Its Influencing Factors Around the Lop Nor Salt Flat

by Yuke Wang, Fojun Yao, Chenglin Liu, Xinxia Geng, Yu Shao and Nan Jiang

Water 2025, 17(5), 770; https://doi.org/10.3390/w17050770 - 6 Mar 2025

Viewed by 584

Abstract

Known as the “Ear of the Earth”, Lop Nor has become one of China’s four largest uninhabited areas due to environmental changes. Lop Nor is rich in mineral resources, including potassium salt, which has good quality and has been largely mined since 2002. [...] Read more.

Known as the “Ear of the Earth”, Lop Nor has become one of China’s four largest uninhabited areas due to environmental changes. Lop Nor is rich in mineral resources, including potassium salt, which has good quality and has been largely mined since 2002. This study focuses on the surrounding area of the Lop Nor Potash Salt Field, which covers an area of 80,036.39 square kilometers, spanning from 39.29° N to 41.84° N and 88.92° E to 92.26° E. The research is based on 1 km resolution precipitation, potential evapotranspiration, temperature data, and 250 m resolution NDVI data spanning 2002–2022. This study is devoted to exploring the trend of precipitation changes in the region surrounding the Lop Nor salt field since the start of the construction of the salt field, exploring the climatic impacts of the construction of the salt field on the surrounding region, and analyzing the correlations related to the changes in precipitation by selected meteorological factors. The Sen and Trend-Free Pre-Whitening Mann–Kendall trend analysis method was used to analyze the trend of precipitation data over the years. Combining with the data of the salt field location, the influence of the development of the salt field on regional precipitation was analyzed both temporally and spatially. The bias correlation analysis method was used to explore the correlation between maximum temperature, potential evapotranspiration, Normalized Difference Vegetation Index, and precipitation. The results of this analysis indicate that between 2002 and 2022, the study area exhibited both increasing and decreasing trends in precipitation. The region experiencing decreasing precipitation is predominantly located in the southwestern part of the study area, encompassing approximately 62% of the total area. Conversely, the area showing increasing precipitation is situated in the northeastern part, accounting for 38% of the total area. Field visits and survey data further corroborated the observed trend of increased precipitation in the northeastern region. Based on these findings, it is hypothesized that the development of salt flats has contributed to the increased precipitation, thereby alleviating regional drought conditions. Additionally, a partial correlation analysis of meteorological factors and precipitation revealed significant correlation. Temperature, potential evapotranspiration (PET), and the Normalized Difference Vegetation Index (NDVI) all exhibited varying degrees of correlation with precipitation. Temperature and potential evapotranspiration were the primary meteorological factors showing significant individual correlations. This study discusses the impact of salt field development and other climatic factors on the drought situation in Lop Nor and quantitatively analyzes the trend of precipitation changes in the study area and the factors affecting it. Water resources are scarce in China’s desert areas, and this research can provide a scientific basis for the state to formulate long-term plans for ecological protection and desert management, and it can also provide guidance for industrial development in desert areas. At the same time, it can provide important data and cases for global climate change research, offering experience and technical support for international cooperation in desertification control. Full article

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

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17 pages, 11811 KiB

Open AccessArticle

Analysis of the Effect of Sea Surface Temperature on Sea Ice Concentration in the Laptev Sea for the Years 2004–2023

by Chenyao Zhang, Ziyu Zhang, Peng Qi, Yiding Zhang and Changlei Dai

Water 2025, 17(5), 769; https://doi.org/10.3390/w17050769 - 6 Mar 2025

Viewed by 514

Abstract

The Laptev Sea, as a marginal sea and a key source of sea ice for the Arctic Ocean, has a profound influence on the dynamic processes of sea ice evolution. Under a 2 °C global warming scenario, the accelerated ablation of Arctic sea [...] Read more.

The Laptev Sea, as a marginal sea and a key source of sea ice for the Arctic Ocean, has a profound influence on the dynamic processes of sea ice evolution. Under a 2 °C global warming scenario, the accelerated ablation of Arctic sea ice is projected to greatly impact Arctic warming. The ocean regulates global climate through its interactions with the atmosphere, where sea surface temperature (SST) serves as a crucial parameter in exchanging energy, momentum, and gases. SST is also a key driver of sea ice concentration (SIC). In this paper, we analyze the spatiotemporal variability of SST and SIC, along with their interrelationships in the Laptev Sea, using daily optimum interpolation SST datasets from NCEI and daily SIC datasets from the University of Bremen for the period 2004–2023. The results show that: (1) Seasonal variations are observed in the influence of SST on SIC. SIC exhibited a decreasing trend in both summer and fall with pronounced interannual variability as ice conditions shifted from heavy to light. (2) The highest monthly averages of SST and SIC were in July and September, respectively, while the lowest values occurred in August and November. (3) The most pronounced trends for SST and SIC appeared both in summer, with rates of +0.154 °C/year and −0.095%/year, respectively. Additionally, a pronounced inverse relationship was observed between SST and SIC across the majority of the Laptev Sea with correlation coefficients ranging from −1 to 0.83. Full article

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10 pages, 1715 KiB

Open AccessArticle

The Role of Climate Warming and Thermal Stratification in the Ecological Success of Diaphanosoma brachyurum in Lake Maggiore

by Roberta Piscia, Rossana Caroni, Claudia Dresti and Marina Manca

Water 2025, 17(5), 768; https://doi.org/10.3390/w17050768 - 6 Mar 2025

Viewed by 527

Abstract

Deep temperate lakes are increasingly reported to suffer consequences of climate warming, affecting thermal stratification and plankton seasonality. Long-term studies offer a unique opportunity for detecting changes in the zooplankton taxa composition related to climate change. Sampling zooplankton organisms alongside abiotic variables, such [...] Read more.

Deep temperate lakes are increasingly reported to suffer consequences of climate warming, affecting thermal stratification and plankton seasonality. Long-term studies offer a unique opportunity for detecting changes in the zooplankton taxa composition related to climate change. Sampling zooplankton organisms alongside abiotic variables, such as water column temperature, enables the linking of changes in plankton communities with variations in the stratification regime. This provides evidence of direct and indirect warming effects. Our study in Lake Maggiore investigated variations in the population density and persistence of Diaphanosoma brachyurum, a thermophile species that is a member of the original zooplankton community of the lake, along with the increase in water temperature and the duration of the thermal stratification during the period 2013–2023. Our results highlighted an increase in the abundance and persistence of Diaphanosoma during the study period, along with an increase in the mean water temperature of the layer 0–10 m and of the length of the thermal stratification. Such changes, affecting the population dynamics of predators and competitors and their food sources (i.e., small algae), might lead to a rearrangement of the structure of the pelagic food chain. Full article

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

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18 pages, 5543 KiB

Open AccessArticle

Deformation and Failure Mechanism of Bedding Rock Landslides Based on Stability Analysis and Kinematics Characteristics: A Case Study of the Xing’an Village Landslide, Chongqing

by Jingyi Zeng, Zhenwei Dai, Xuedong Luo, Weizhi Jiao, Zhe Yang, Zixuan Li, Nan Zhang and Qihui Xiong

Water 2025, 17(5), 767; https://doi.org/10.3390/w17050767 - 6 Mar 2025

Viewed by 611

Abstract

Bedding rock landslides, characterized by their distinct geological structure, are widely distributed and highly susceptible to sliding under external disturbances, resulting in catastrophic events. This study aims to unravel the geomechanical mechanisms governing rainfall-induced instability through an integrated investigation of a representative landslide [...] Read more.

Bedding rock landslides, characterized by their distinct geological structure, are widely distributed and highly susceptible to sliding under external disturbances, resulting in catastrophic events. This study aims to unravel the geomechanical mechanisms governing rainfall-induced instability through an integrated investigation of a representative landslide in Xing’an Village, Chongqing. Employing multidisciplinary approaches, including field monitoring, geotechnical testing, and dynamic numerical modeling, we systematically revealed two critical failure zones: a front failure zone and a rear potential instability zone. Under rainstorm conditions, the safety factor for both zones was 1.02, indicating a marginally unstable state. The DAN-W simulations indicate that the potential instability zone at the rear of the landslide experienced complete failure within 12 s under heavy rainfall, with a maximum run-out distance of 20 m, a maximum velocity of 4.32 m/s, and a maximum deposition thickness of 8.3 m, which could potentially bury the buildings at the toe of the landslide. The low strength and permeability of the mudstone-dominated Badong Formation, characterized by interbedded mudstone, siltstone, and sandstone within the Middle Triassic geological system, provides a fundamental prerequisite for the landslide. Rainwater infiltration into the mudstone layers degraded its mechanical properties, and excavation at the slope base ultimately triggered the landslide initiation. These findings can provide theoretical support for preventing and managing similar bedding rock landslides with similar geological backgrounds. Full article

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27 pages, 10829 KiB

Open AccessArticle

Potentiality Delineation of Groundwater Recharge in Arid Regions Using Multi-Criteria Analysis

by Heba El-Bagoury, Mahmoud H. Darwish, Sedky H. A. Hassan, Sang-Eun Oh, Kotb A. Attia and Hanaa A. Megahed

Water 2025, 17(5), 766; https://doi.org/10.3390/w17050766 - 6 Mar 2025

Viewed by 485

Abstract

This study integrates morphometric analysis, remote sensing, and GIS with the analytical hierarchical process (AHP) to identify high potential groundwater recharge areas in Wadi Abadi, Egyptian Eastern Desert, supporting sustainable water resource management. Groundwater recharge primarily comes from rainfall and Nile River water, [...] Read more.

This study integrates morphometric analysis, remote sensing, and GIS with the analytical hierarchical process (AHP) to identify high potential groundwater recharge areas in Wadi Abadi, Egyptian Eastern Desert, supporting sustainable water resource management. Groundwater recharge primarily comes from rainfall and Nile River water, particularly for Quaternary aquifers. The analysis focused on the Quaternary and Nubian Sandstone aquifers, evaluating 16 influencing parameters, including elevation, slope, rainfall, lithology, soil type, and land use/land cover (LULC). The drainage network was derived from a 30 m-resolution Digital Elevation Model (DEM). ArcGIS 10.8 was used to classify the basin into 13 sub-basins, with layers reclassified and weighted using a raster calculator. The groundwater potential map revealed that 24.95% and 29.87% of the area fall into very low and moderate potential categories, respectively, while low, high, and very high potential zones account for 18.62%, 17.65%, and 8.91%. Data from 41 observation wells were used to verify the potential groundwater resources. In this study, the ROC curve was applied to assess the accuracy of the GWPZ models generated through different methods. The validation results indicated that approximately 87% of the wells corresponded accurately with the designated zones on the GWPZ map, confirming its reliability. Over-pumping in the southwest has significantly lowered water levels in the Quaternary aquifer. This study provides a systematic approach for identifying groundwater recharge zones, offering insights that can support resource allocation, well placement, and aquifer sustainability in arid regions. This study also underscores the importance of recharge assessment for shallow aquifers, even in hyper-arid environments. Full article

(This article belongs to the Special Issue Advance in Groundwater in Arid Areas)

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19 pages, 8318 KiB

Open AccessArticle

Activation of H₂O₂/PDS/PMS by Iron-Based Biochar Derived from Fenton Sludge for Oxidative Removal of 2,4-DCP and As(III)

by Chutong Ling, Renting Huang, Wei Mao, Zhiming Wu, Cui Wei, Anze Li and Jinghong Zhou

Water 2025, 17(5), 765; https://doi.org/10.3390/w17050765 - 6 Mar 2025

Viewed by 547

Abstract

In this study, the catalytic performance of the Fenton sludge iron-based biochar catalyst (Fe@BC700), generated during the Fenton process, was investigated regarding its role in oxidizing 2,4-dichlorophenol (2,4-DCP) and As(III) from aqueous solutions in peroxymonosulfate (PMS), peroxydisulfate (PDS), and hydrogen peroxide (H₂ [...] Read more.

In this study, the catalytic performance of the Fenton sludge iron-based biochar catalyst (Fe@BC700), generated during the Fenton process, was investigated regarding its role in oxidizing 2,4-dichlorophenol (2,4-DCP) and As(III) from aqueous solutions in peroxymonosulfate (PMS), peroxydisulfate (PDS), and hydrogen peroxide (H₂O₂) systems. The characteristics of the as-prepared catalyst, operational parameters of H₂O₂/UV/Fe@BC700, PDS/UV/Fe@BC700, and PMS/UV/Fe@BC700 systems, and the kinetics of 2,4-DCP degradation were evaluated. Fe@BC700 exhibited excellent capabilities for activating persulfate and an outstanding oxidant performance as a heterogeneous photocatalyst under UV irradiation. Among the tested systems, PMS/UV/Fe@BC700 showed the highest oxidation capabilities for both 2,4-DCP and As(III) within 40 min. The total organic carbon (TOC) removal efficiency for 2,4-DCP was up to 95.9% in the PMS/UV/Fe@BC700 system. The presence of free radicals in the PMS/PDS system included ·OH, SO₄^·−, and ·O₂⁻, which were facilitated by both UV irradiation and the catalyst. The by-products generated during the PMS/UV/Fe@BC700 treatment were identified via LC-MS analysis, which showed that catalytic degradation substantially reduced the chronic and acute toxicity of 2,4-DCP intermediates. The present study demonstrates that the iron-based biochar derived from Fenton sludge exhibited remarkable persulfate activation capabilities and was highly effective in removing 2,4-DCP and As(III). Full article

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

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22 pages, 12360 KiB

Open AccessArticle

Understanding Public Perception and Preparedness for Flood Risks in Greece

by Nada Joumar, Cleo M. Gaganis, Polina N. Tourlioti, Ioannis Pantelakis, Ourania Tzoraki, Lahcen Benaabidate, Jamal Eddine Stitou El Messari and Petros Gaganis

Water 2025, 17(5), 764; https://doi.org/10.3390/w17050764 - 6 Mar 2025

Viewed by 820

Abstract

The present study examines perceptions and preparedness for flooding in Greece, a country increasingly impacted by natural hazards, particularly due to the effects of climate change. Despite the frequent occurrence of floods, public preparedness remains insufficient in many areas. Through a survey of [...] Read more.

The present study examines perceptions and preparedness for flooding in Greece, a country increasingly impacted by natural hazards, particularly due to the effects of climate change. Despite the frequent occurrence of floods, public preparedness remains insufficient in many areas. Through a survey of 1282 respondents from various regions of Greece and using R statistical software to process and analyse data, the research explores the relationship between individual flood risk perceptions, prior experiences, and household-level preparedness. The findings show most participants are aware of governmental flood plans, but a significant gap exists between perceived flood risks and actual preparedness, especially regarding insurance and relocation willingness. The findings reveal that a majority of participants are aware of governmental flood management plans; however, outcomes concerning flood insurance and the willingness to relocate highlight the significant gap between perceived flood risks and actual preparedness efforts. Many respondents expressed dissatisfaction with current measures to address flood risks, leading to a diminished trust in the respective authorities. To enhance public awareness and engagement in flood preparedness, the study underscores the importance of localized risk communication strategies tailored to different demographic groups. Given the observed gap between awareness and actual preparedness, efforts should focus on bridging this disconnect through practical, community-driven initiatives. Recommendations include implementing targeted awareness campaigns, promoting trust in government efforts through transparent policies, and providing financial incentives such as subsidized flood insurance to encourage protective actions, and, additionally, fostering community involvement in disaster risk management, particularly in historically flood-prone regions, to strengthen the resilience against future flooding events. Full article

(This article belongs to the Special Issue Global and Regional Flood Risk Modelling and Analysis in Climate Change Scenario)

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13 pages, 1727 KiB

Open AccessArticle

Degradation of Phenolic Compounds and Organic Matter from Real Winery Wastewater by Fenton and Photo-Fenton Processes Combined with Ultrasound

by Ricardo Augusto Rodrigues, Mariana Bizari Machado de Campos and Paulo Sergio Tonello

Water 2025, 17(5), 763; https://doi.org/10.3390/w17050763 - 6 Mar 2025

Viewed by 480

Abstract

Real winery wastewater (WW), with a high concentration of organic matter (OM), was treated using Fenton (FP), photo-Fenton (PFP), sono-Fenton (SFP), and sono-photo-Fenton processes (SPFP), with the primary objective of removing phenolic compounds (PhCs). Although beneficial to human health, these compounds are considered [...] Read more.

Real winery wastewater (WW), with a high concentration of organic matter (OM), was treated using Fenton (FP), photo-Fenton (PFP), sono-Fenton (SFP), and sono-photo-Fenton processes (SPFP), with the primary objective of removing phenolic compounds (PhCs). Although beneficial to human health, these compounds are considered recalcitrant and toxic to aquatic organisms, posing significant environmental risks if discharged into water bodies. They can also reduce the efficiency of biological treatment processes. After physicochemical characterization and two hours of treatment, the removal efficiencies achieved by the FP, PFP, SFP, and SPFP processes were 29.35%, 41.30%, 28.82%, and 33.95% for PhCs; 27.88%, 31.51%, 23.19%, and 29.29% for chemical oxygen demand (COD); and 12.53%, 13.92%, 9.28%, and 10.62% for dissolved organic carbon (DOC), respectively. The degradations achieved by SFP and SPFP were lower than those of FP and PFP, respectively, due to reactions that scavenge hydroxyl radicals. Treatment of a gallic acid (GA) solution, used as a model compound for PhCs, exhibited similar trends, indicating that the lower efficiency in processes involving ultrasound is not due to the OM in the effluent, but rather the interaction between ultrasound (US) and H₂O₂, which reduces hydroxyl radical concentration. However, under the conditions of the wastewater used, the technologies applied did not completely reduce the parameters analyzed, being recommended as pre- or post-treatment, and combined with other processes. Full article

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

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17 pages, 4341 KiB

Open AccessArticle

Tailoring the Structural and Morphological Properties of Biogenic Nano-Chlorapatite to Enhance the Capture Efficiency Towards Cr(VI)

by Zhuangzhuang Tian, Xinyu Huan, Yuanyi Li, Jiaqi Zhi and Wei Wei

Water 2025, 17(5), 762; https://doi.org/10.3390/w17050762 - 5 Mar 2025

Viewed by 455

Abstract

Nano-chlorapatite (nClAP) has been widely used as an efficient and environment-benign material to remediate heavy metal-contaminated water and soil. However, the adsorption capacities of nClAP to heavy metal oxyanions such as Cr(VI) are limited, which restricts its further application in environmental remediation. Herein, [...] Read more.

Nano-chlorapatite (nClAP) has been widely used as an efficient and environment-benign material to remediate heavy metal-contaminated water and soil. However, the adsorption capacities of nClAP to heavy metal oxyanions such as Cr(VI) are limited, which restricts its further application in environmental remediation. Herein, a novel carboxymethyl cellulose (CMC)-modified biogenic nClAP (CMC-nClAP) adsorbent was synthesized by a facile wet chemical method and used for Cr(VI) removal from water. The obtained CMC-nClAP materials were characterized by FTIR, XRD, TEM, and TGA analyses. Then, batch experiments were conducted to explore the effects of various factors such as the ratio of CMC and nClAP, pH, adsorbent dosage, adsorption time, and temperature on the adsorption process. The results revealed that the CMC-nClAP adsorbent displayed markedly improved stability against aggregation as well as Cr(VI) adsorption capacity as compared to that of the pristine nClAP. The Cr(VI) adsorption data obeyed the Langmuir isotherm model and pseudo-second-order kinetic model. Site energy distribution analyses revealed that Cr(VI) first occupied the high-energy sites and then diffused to the low-energy adsorption sites on the CMC-nClAP surface. Our experimental results indicated that the CMC-nClAP could be a promising material for the removal of Cr(VI) from water. Full article

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

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13 pages, 3712 KiB

Open AccessArticle

The Effect of Entrainment Model on Debris-Flow Simulation—Comparison of Two Simple 1D Models

by Song Eu and Sangjun Im

Water 2025, 17(5), 761; https://doi.org/10.3390/w17050761 - 5 Mar 2025

Viewed by 396

Abstract

Debris flows, consisting of water–sediment mixtures that travel rapidly along channels, often carry materials ranging from fine sediments, such as clay or silt, to large boulders, resulting in significant impacts on lives and infrastructure. Accurate estimation of the debris-flow behavior is crucial for [...] Read more.

Debris flows, consisting of water–sediment mixtures that travel rapidly along channels, often carry materials ranging from fine sediments, such as clay or silt, to large boulders, resulting in significant impacts on lives and infrastructure. Accurate estimation of the debris-flow behavior is crucial for establishing effective debris-flow mitigation strategies. However, the dynamic entrainment process complicates simulations because it significantly affects flow characteristics, including velocity, depth, and sediment concentration. In this study, we analyzed the effects of entrainment on debris flow simulations using two one-dimensional models for a debris-flow event that occurred in 2011 in Seoul, Republic of Korea. The results show that including entrainment improves the accuracy of the debris-flow simulation. Moreover, a scheme dealing with entrained sediment in the governing equations is important for reproducing debris-flow characteristics. These findings highlight the necessity of entrainment models for effective debris-flow simulation, with implications for enhancing debris-flow hazard mitigation strategies. Full article

(This article belongs to the Special Issue Flowing Mechanism of Debris Flow and Engineering Mitigation)

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17 pages, 2624 KiB

Open AccessArticle

Insight into Adsorption Kinetics, Equilibrium, Thermodynamics, and Modeling of Ciprofloxacin onto Iron Ore Tailings

by Nan Fang, Yanhua Xi, Jing Zhang, Jian Wu, Huicai Cheng and Qiang He

Water 2025, 17(5), 760; https://doi.org/10.3390/w17050760 - 5 Mar 2025

Cited by 1 | Viewed by 508

Abstract

To achieve the resource utilization of iron ore tailings (IOTs), two different IOTs were investigated as sustainable adsorbents for ciprofloxacin (CIP) removal from aqueous systems. Through systematic batch experiments, key adsorption parameters including initial pH, adsorbent dosage, contact time, ionic strength, and temperature [...] Read more.

To achieve the resource utilization of iron ore tailings (IOTs), two different IOTs were investigated as sustainable adsorbents for ciprofloxacin (CIP) removal from aqueous systems. Through systematic batch experiments, key adsorption parameters including initial pH, adsorbent dosage, contact time, ionic strength, and temperature were comprehensively evaluated. The results showed that CIP adsorption by IOTs remained relatively stable across a broad initial pH range (2–10), with maximum adsorption capacities of 5-IOT and 14-IOT observed at the initial pH values of 10.1 and 9.16, respectively. Competitive ion experiments revealed a gradual decrease in CIP adsorption capacity with increasing ionic strength (Na⁺, Mg²⁺, and Ca²⁺). Thermodynamic analyses indicated an inverse relationship between adsorption capacity and temperature, yielding maximum adsorption capacities (Q_max) of 16.64 mg/g (5-IOT) and 13.68 mg/g (14-IOT) at 288.15 K. Mechanistic investigations combining material characterization and adsorption modeling identified ion exchange as the predominant interaction mechanism. Notably, trace elements (Cd, Co, Cr, Cu, Fe, Ni, Pb, and Zn) were released during leaching tests, with concentrations consistently below environmental safety thresholds. A back-propagation artificial neural network (BP-ANN) with optimized architecture (8-11-1 topology) demonstrated high predictive accuracy (MSE = 0.0031, R² = 0.9907) for adsorption behavior. These findings suggested IOTs as cost-effective, environmentally compatible adsorbents for CIP remediation, offering the dual advantages of pharmaceutical pollutant removal and industrial waste valorization. Full article

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

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26 pages, 7498 KiB

Open AccessArticle

Coordinated Development Model of Coal–Water–Ecology in Open-Pit Combined Underground Mining Area

by Yanghui Duan, Tingting Chen, Xiaojiao Li, Liangliang Guo and Xinxin Xie

Water 2025, 17(5), 759; https://doi.org/10.3390/w17050759 - 5 Mar 2025

Viewed by 395

Abstract

In this paper, a coal–water–ecology (CWE) index system is firstly constructed based on an analysis of the current situation regarding coal mining, water resource utilization, and the ecological environment in an open-pit combined underground mining area. Three methods are used to determine the [...] Read more.

In this paper, a coal–water–ecology (CWE) index system is firstly constructed based on an analysis of the current situation regarding coal mining, water resource utilization, and the ecological environment in an open-pit combined underground mining area. Three methods are used to determine the weights of each index in the system. Then, the TOPSIS model and coupling coordination degree model are adopted to construct the coordinated development model for CWE. Finally, the coordinated development status of CWE in the mine area is analyzed, and the next improvement measures are pointed out. The CWE index system contains 3 dimensions, 6 aspects, and 21 indicators. Combining the weights with game theory makes the weight coefficients more concentrated, reduces the dispersion of single weights, and makes the results of the fusion weights more reliable. The TOPSIS model and coupling coordination degree model can successfully characterize the coordinated development of CWE system factors. The proximity degrees of the CWE system in the study area show an increasing trend year by year. Although the coupling degree of CWE increases slowly year by year, it exhibits little coordination, with an average value of 0.4. Economic benefits, the water resource utilization rate, and the green land area are the three indices with the greatest weights. While ensuring the economic benefits of coal mining, coal enterprises should focus on improving the water resource utilization rate. The reduction in the green land area should also be emphasized in open-pit mining. Full article

(This article belongs to the Section Ecohydrology)

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18 pages, 266 KiB

Open AccessArticle

Evaluation of Hydraulic and Irrigation Performances of Drip Systems in Nectarine Orchards (Prunus persica var. nucipersica) in The Mediterranean Region

by Alper Baydar, Yeşim Bozkurt Çolak, Cenk Küçükyumuk and Burak Dalkılıç

Water 2025, 17(5), 758; https://doi.org/10.3390/w17050758 - 5 Mar 2025

Viewed by 479

Abstract

This study focused on evaluating the performance of the drip irrigation systems installed in 18 different nectarines (Prunus persica var. nucipersica) orchards in the Tarsus Plain in the Mediterranean region from 2017 through 2018. The performance of the drip systems was [...] Read more.

This study focused on evaluating the performance of the drip irrigation systems installed in 18 different nectarines (Prunus persica var. nucipersica) orchards in the Tarsus Plain in the Mediterranean region from 2017 through 2018. The performance of the drip systems was evaluated based on parameters like average emitter discharge (Qavg), Christiansen uniformity coefficient (CU), distribution uniformity (DU), emission uniformity (EU), and system application efficiency (Ea). The results indicated that the CU varied between 81 and 98%; DU changed from 82 to 97%; EU 61–92%; absolute emission uniformity (EUa) ranged between 93 and 98%; statistical uniformity (Us) changed from 85 to 97%; application efficiency of low-quarter (AELQ) varied between 45 and 97%; potential application efficiency of low-quarter (PELQ) ranged between 55 and 83%; system application efficiency (Ea) changed from 56 to 96%; storage efficiency (Es) fluctuated between 45 and 97%; and pressure variation (Pv) 17–81% and emitter flow variations (qv) of 2–36% were determined. Although the CU, DU, and EU values were acceptable, the variations in emitter flow rates and pressures were not acceptable. The results revealed that the lower performances might be attributed to physical clogging and/or lack of system design and application practices by the farmers. It is recommended that the farmers receive appropriate training on the operation and management of drip irrigation systems. Full article

(This article belongs to the Special Issue Agricultural Practices to Improve Irrigation Sustainability, 2nd Edition)

21 pages, 3383 KiB

Open AccessArticle

Spatial and Seasonal Water Quality and Heavy Metal Pollution for Irrigation Use in Awash River, Ethiopia

by Elias Kebede Hailu, Tena Alamirew Agumassie, Solomon Gebreyohannis Gebrehiwot, Abebe Demissie Chukalla and Katrina Jane Charles

Water 2025, 17(5), 757; https://doi.org/10.3390/w17050757 - 5 Mar 2025

Viewed by 552

Abstract

Irrigation water quality impacts the agro-ecosystem, human health, and the overall well-being of the environment. The purpose of this study was to investigate upstream municipal and industrial pollution impacts on irrigated farming and ecosystem health. The suitability indices and Heavy Metal Pollution Index [...] Read more.

Irrigation water quality impacts the agro-ecosystem, human health, and the overall well-being of the environment. The purpose of this study was to investigate upstream municipal and industrial pollution impacts on irrigated farming and ecosystem health. The suitability indices and Heavy Metal Pollution Index methods have been used to identify the contamination extent and corresponding spatial and seasonal variability. Samples were collected twice per annum, i.e., during the low-flow season and high-flow season (rainy season) in the 2022/23 year. Results showed that during the low-flow season, the salinity hazard was 0.7 dS/m to 2.5 dS/m and medium to high. Sodicity hazards were obtained below <10 for the low-flow season, and for the rainy season, medium (16.63), high (18–26), and very high (>26). The toxic level of chloride for low-flow season showed slight to moderate at 3.6 mg/L and 6.07 mg/L, and toxicity was severe at Deho (14.6 mg/L), slight to moderate at Ambash (4 mg/L), Ertaale Lake (5 mg/L), and Gewanie (4.6 mg/L) in high-flow seasons. No heavy metal contamination was observed for low-flow periods except at Werer Research, which had a Heavy Metal Pollution Index (HPI) > 100. But, during the rainy season, Kesem Dam, Sedi Weir, WARC Pumping, WARC Offtake, and Ambash had a HPI > 100, which implied contamination by metals. Cadmium (Cd) was at moderate to ecological risk at low flow in sites Kesem factory, WARC Offtake, Ertaale, Meteka, and Gewanie, whereas Sedi Weir (Cd and Hg) and WARC Offtake (Cd) were at moderate risk during high flow. To conclude, metal pollution is a serious concern that needs upstream quality monitoring. Full article

(This article belongs to the Section Water Use and Scarcity)

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17 pages, 28541 KiB

Open AccessArticle

Utilizing Deep Learning Models to Predict Streamflow

by Habtamu Alemu Workneh and Manoj K. Jha

Water 2025, 17(5), 756; https://doi.org/10.3390/w17050756 - 5 Mar 2025

Viewed by 660

Abstract

This study employs convolutional neural network (CNN), long short-term memory (LSTM), bidirectional long short-term memory (BiLSTM), and gated recurrent unit (GRU) deep learning models to simulate daily streamflow using precipitation data. Two approaches were explored: one without dimension reduction and another incorporating dimensionality [...] Read more.

This study employs convolutional neural network (CNN), long short-term memory (LSTM), bidirectional long short-term memory (BiLSTM), and gated recurrent unit (GRU) deep learning models to simulate daily streamflow using precipitation data. Two approaches were explored: one without dimension reduction and another incorporating dimensionality reduction technique. Principal component analysis (PCA) was employed for dimensionality reduction, and partial autocorrelation function (PACF) was used to determine time lags. An augmented Dickey–Fuller (ADF) test was utilized to ascertain the stationarity of the data, ensuring optimal model performance. The data were normalized and then partitioned into features and target variables, before being split into training, validation, and test sets. The developed models were tested for their performance, robustness, and stability at three locations along the Neuse River, which is in the Neuse River Basin, North Carolina, USA, covering an area of about 14,500 km². Furthermore, the model’s performance was tested during peak flood events to assess their ability to capture the temporal resolution of streamflow. The results revealed that the CNN model could capture the variability in daily streamflow prediction, as evidenced by excellent statistical measures, including mean absolute error, root mean square error, and Nush–Sutcliffe efficiency. The study also found that incorporating dimensionality reduction significantly improved model performance. Full article

(This article belongs to the Special Issue Hydrological Simulation and Forecasting Based on Artificial Intelligence)

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25 pages, 30212 KiB

Open AccessArticle

Hydrogeology of a Volcano-Sedimentary Multi-Aquifer System: The Skydra, Northern Greece, Case Study

by Dimitra Rapti

Water 2025, 17(5), 755; https://doi.org/10.3390/w17050755 - 4 Mar 2025

Viewed by 494

Abstract

Due to climate change, water scarcity, and overexploitation of aquifers, the sustainable management and protection of groundwater resources will be one of the main challenges in the future. Therefore, the knowledge of hydrogeological characteristics, which must be as robust as possible, becomes crucial [...] Read more.

Due to climate change, water scarcity, and overexploitation of aquifers, the sustainable management and protection of groundwater resources will be one of the main challenges in the future. Therefore, the knowledge of hydrogeological characteristics, which must be as robust as possible, becomes crucial for defining groundwater management plans. On the other hand, the earliest evidence of the fertile plains and abundant water resources of Skydra and its surroundings dates back to the Neolithic period (6500–3200 B.C.), confirming the area’s current agricultural vocation and productivity. In this perspective, the aim of the present study is to define the conceptual hydrogeological model of a complex confined multi-aquifer system characterizing the volcano-sedimentary deposits of the Skydra area, northern Greece. In particular, the architecture of the hydrostratigraphic units, the hydraulic parameters, and the hydrodynamic behavior of the multi-aquifer system were analyzed. The geological, geomorphological, and structural evolution affecting the area has influenced the geometric and hydraulic characteristics of the aquifer, and consequently its productivity. The thickness of the multi-aquifer system varies between 25.0 and 94.5 m and the hydraulic conductivity, calculated through the analysis of data from 72 pumping tests, and the application of empirical method (42 wells), ranges between 2.2 · 10⁻⁶ and 2.5 · 10⁻³ m/s. Higher hydraulic conductivity values are calculated in areas where tuffaceous formations are fractured and/or interlayered with sandy layers; while lower values occur where tuffs present only primary porosity and are interspersed with frequent clay layers. In the central area, due to overexploitation of the aquifer, an annual piezometric level drop of approximately 6 m has been recorded. The information acquired could serve as the basis for the sustainable development of groundwater resources in the test area and could also be applied in other similar hydrogeological settings. Full article

(This article belongs to the Section Hydrogeology)

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13 pages, 213 KiB

Open AccessReview

Challenges in Designing Electrochemical Disinfection Systems for Reducing Microbial Contamination in Drinking Water Distribution Networks

by Sergio Ferro

Water 2025, 17(5), 754; https://doi.org/10.3390/w17050754 - 4 Mar 2025

Viewed by 600

Abstract

Electrochemical disinfection systems are gaining attention as potential solutions for reducing microbial contamination in drinking water distribution networks. While numerous recent studies suggest that these systems are easy to implement, real-world application reveals significant challenges. Many published works suffer from fundamental flaws, including [...] Read more.

Electrochemical disinfection systems are gaining attention as potential solutions for reducing microbial contamination in drinking water distribution networks. While numerous recent studies suggest that these systems are easy to implement, real-world application reveals significant challenges. Many published works suffer from fundamental flaws, including inappropriate material selection, unrealistic operating conditions, and non-compliance with regulatory standards. This review critically examines studies published over the past 24 months, highlighting key issues that limit practical applicability. It discusses common pitfalls, such as the use of unstable or toxic electrode materials and the failure to provide residual disinfectant effects. Additionally, the review outlines essential characteristics for effective electrochemical disinfection systems, emphasizing compliance with health regulations, scalability to real-world conditions, and long-term operational stability. By identifying these gaps, this review article aims to guide future research toward more viable, safe, and sustainable electrochemical disinfection solutions for drinking water treatment. Full article

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

19 pages, 4359 KiB

Open AccessArticle

Consistent Coupled Patterns of Teleconnection Between Rainfall in the Ogooué River Basin and Sea Surface Temperature in Tropical Oceans

by Sakaros Bogning, Frédéric Frappart, Valentin Brice Ebode, Raphael Onguene, Gil Mahé, Michel Tchilibou, Jacques Étamé and Jean-Jacques Braun

Water 2025, 17(5), 753; https://doi.org/10.3390/w17050753 - 4 Mar 2025

Viewed by 611

Abstract

This study investigates teleconnections between rainfall in the Ogooué River Basin (ORB) and sea surface temperature (SST) in the tropical ocean basins. The Maximum Covariance Analysis (MCA) is used to determine coupled patterns of SST in the tropical oceans and rainfall in the [...] Read more.

This study investigates teleconnections between rainfall in the Ogooué River Basin (ORB) and sea surface temperature (SST) in the tropical ocean basins. The Maximum Covariance Analysis (MCA) is used to determine coupled patterns of SST in the tropical oceans and rainfall in the ORB, depicting regions and modes of SST dynamics that influence rainfall in the ORB. The application of MCA to rainfall and SST fields results in three coupled patterns with squared covariance fractions of 84.5%, 76.5%, and 77.5% for the Atlantic, Pacific, and Indian tropical basins, respectively. Computation of the correlations of the Savitzky–Golay-filtered resulting expansion coefficients reached 0.65, 0.5 and 0.72, respectively. The SST variation modes identified in this study can be related to the Atlantic Meridional Mode for the tropical Atlantic and the El Niño Southern Oscillation for the tropical Pacific. Over the Indian Ocean, it is a homogeneous mode over the entire basin, instead of the popular dipole mode. Then, the time-dependent correlation method is used to remove any ambiguity on the relationships established from the MCA. Full article

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

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28 pages, 33355 KiB

Open AccessArticle

Identifying Persistent Drought Regions for Mediterranean Basin Using Simple Coincidence Deficit Index Approach

by Gökçe Ceylan Akan, Abdurrahman Ufuk Şahin and Arzu Özkaya

Water 2025, 17(5), 752; https://doi.org/10.3390/w17050752 - 4 Mar 2025

Viewed by 579

Abstract

This study introduces the Simple Coincidence Deficit Index (SCDI) and employs Drought Severity Analysis (DSA) to enhance drought detection and assess patterns and persistency across the Mediterranean basin. Utilizing the Global Land Data Assimilation System (GLDAS) based multi-satellite data for precipitation (P) and [...] Read more.

This study introduces the Simple Coincidence Deficit Index (SCDI) and employs Drought Severity Analysis (DSA) to enhance drought detection and assess patterns and persistency across the Mediterranean basin. Utilizing the Global Land Data Assimilation System (GLDAS) based multi-satellite data for precipitation (P) and groundwater storage (GWS), this research applies both SCDI and DSA to visualize and interpret hydrological event time series across the region. The SCDI uniquely combines precipitation and groundwater levels to provide a comprehensive view of drought intensity. DSA tracks the persistence of water deficit and allows straightforward analysis without requiring transformation or normalization, making it easier to use with remote sensing data. The DSA determines the longest drought periods across various time windows, quantifying the number of months a hydrological deficit persists based on groundwater and precipitation data. Findings show that significant deficits are observed in specific months, which become less apparent in shorter time windows (

Δ

= 1) due to their rarity. Conversely, in broader time windows (

Δ

= 12), the cumulative effects of these deficits significantly impact seasonal and yearly averages, with implications extending from lower to higher latitudes. Additionally, as time windows extend, the variability in SCDI values increases across all regions, rendering long-term drought conditions more visible, particularly in North Africa. These findings form the basis of future studies focusing on understanding of drought phenomena and enhancing drought predictability using remote sensing data. The proposed DSA and SCDI methodologies represent a significant advancement over traditional indices by offering new tools for more effective drought analysis. Full article

(This article belongs to the Section Hydrology)

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16 pages, 10090 KiB

Open AccessArticle

Hybrid System of Fenton Process and Sequencing Batch Reactor for Coking Wastewater Treatment

by Anna Grosser, Ewa Neczaj, Dorota Krzemińska and Izabela Ratman-Kłosińska

Water 2025, 17(5), 751; https://doi.org/10.3390/w17050751 - 4 Mar 2025

Viewed by 507

Abstract

The aim of the work was to investigate the treatment efficiency of coking wastewater in a hybrid system combining the Fenton process with an SBR reactor. The Fenton reaction was optimised using variable reagent doses of 0.75, 1.0, 1.25 and 1.5 g/L for [...] Read more.

The aim of the work was to investigate the treatment efficiency of coking wastewater in a hybrid system combining the Fenton process with an SBR reactor. The Fenton reaction was optimised using variable reagent doses of 0.75, 1.0, 1.25 and 1.5 g/L for iron ions and 750, 1000, 1250, and 1500 mg/L for H₂O₂. The effects of Fe²⁺ and H₂O₂ concentration on BOD, COD, TOC, TN N-NH₄⁺ and BOD/COD ratio were studied in detail to optimise the pretreatment performance. The selection of the most favourable parameters for the Fenton reaction was based on the frequency of occurrence of a different combination of the chemical reagents. The most beneficial doses were found to be 0.75 g/L of iron (II) ion and 1000 mg/L of hydrogen peroxide, at which the COD reduction rate was about 40% and a high increase in the BOD₅/COD ratio from 0.1 to 0.31 was observed. Moreover, the obtained results showed that the efficiency of removing organic pollutants and nitrogen compounds was higher in the SBR reactor fed with pretreated wastewater. However, the relatively low efficiency of removing TKN (25%) and NH₄⁺ (21%) indicates the presence of toxic substances in them that may inhibit the removal of nitrogen compounds. Full article

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14 pages, 17234 KiB

Open AccessArticle

A Grid-Based Long Short-Term Memory Framework for Runoff Projection and Uncertainty in the Yellow River Source Area Under CMIP6 Climate Change

by Haibo Chu, Yulin Jiang and Zhuoqi Wang

Water 2025, 17(5), 750; https://doi.org/10.3390/w17050750 - 4 Mar 2025

Viewed by 530

Abstract

Long-term runoff projection and uncertainty estimates can provide both the changing trends and confidence intervals of water resources, provide basic information for decision makers, and reduce risks for water resource management. In this paper, a grid-based runoff projection and uncertainty framework was proposed [...] Read more.

Long-term runoff projection and uncertainty estimates can provide both the changing trends and confidence intervals of water resources, provide basic information for decision makers, and reduce risks for water resource management. In this paper, a grid-based runoff projection and uncertainty framework was proposed through input selection and long short-term memory (LSTM) modelling coupled with uncertainty analysis. We simultaneously considered dynamic variables and static variables in the candidate input combinations. Different input combinations were compared. We employed LSTM to develop a relationship between monthly runoff and the selected variables and demonstrated the improvement in forecast accuracy through comparison with the MLR, RBFNN, and RNN models. The LSTM model achieved the highest mean Kling–Gupta Efficiency (KGE) score of 0.80, representing respective improvements of 45.45%, 33.33%, and 2.56% over the other three models. The uncertainty sources originating from the parameters of the LSTM models were considered, and the Monte Carlo approach was used to provide uncertainty estimates. The framework was applied to the Yellow River Source Area (YRSR) at the 0.25° grid scale to better show the temporal and spatial features. The results showed that extra information about static variables can improve the accuracy of runoff projections. Annual runoff tended to increase, with projection ranges of 148.44–296.16 mm under the 95% confidence level, under various climate scenarios. Full article

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19 pages, 6902 KiB

Open AccessArticle

Predictive Modeling of Cyanobacterial Blooms and Diurnal Variation Analysis Based on GOCI

by Chichang Luo, Xiang Wang, Yuan Chen, Hongde Luo, Heng Dong and Sicong He

Water 2025, 17(5), 749; https://doi.org/10.3390/w17050749 - 4 Mar 2025

Viewed by 534

Abstract

Algal bloom is a major ecological and environmental problem caused by abnormal algal reproduction in water, and it poses a serious threat to the aquatic ecosystem, drinking water safety, and public health. Because of the high dynamic and spatiotemporal heterogeneity of bloom outbreaks, [...] Read more.

Algal bloom is a major ecological and environmental problem caused by abnormal algal reproduction in water, and it poses a serious threat to the aquatic ecosystem, drinking water safety, and public health. Because of the high dynamic and spatiotemporal heterogeneity of bloom outbreaks, the process often presents significant changes in a short time. Therefore, it has important scientific research value and practical application significance to construct an accurate and effective bloom warning model. This study constructs an integrated model combining sequence features, attention mechanisms, and random forest using machine learning algorithms for bloom prediction, based on watercolor geostationary satellite observations and meteorological data from GOCI in South Korea. In the process, high spatial resolution Sentinel-2 satellite data is also utilized for sample extraction. With a 10-m resolution, Sentinel-2 provides more precise spatial information compared to the 500-m resolution of GOCI, which significantly enhances the accuracy of the model, especially in monitoring local water body changes. The experimental results demonstrate that the model exhibits excellent accuracy and stability in the spatiotemporal prediction of water blooms. The average AUC value is 0.88, the F1 score is 0.72, and the accuracy is 0.79 when identifying the dynamic change of water bloom on the hourly scale. At the same time, this study summarized four typical diurnal change modes of effluent bloom, including dispersal mode, persistent outbreak mode, dispersal-regression mode, and subsidence mode, revealing the main characteristics of diurnal dynamic change of bloom. The research results provided strong technical support for water environment monitoring and water quality safety management and showed a good application prospect. Full article

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18 pages, 5447 KiB

Open AccessArticle

Coupling Interpretable Feature Selection with Machine Learning for Evapotranspiration Gap Filling

by Lizheng Wang, Lixin Dong and Qiutong Zhang

Water 2025, 17(5), 748; https://doi.org/10.3390/w17050748 - 4 Mar 2025

Viewed by 657

Abstract

Evapotranspiration (ET) plays a pivotal role in linking the water and carbon cycles between the land and atmosphere, with latent heat flux (LE) representing the energy manifestation of ET. Due to adverse meteorological conditions, data quality filtering, and instrument malfunctions, LE measured by [...] Read more.

Evapotranspiration (ET) plays a pivotal role in linking the water and carbon cycles between the land and atmosphere, with latent heat flux (LE) representing the energy manifestation of ET. Due to adverse meteorological conditions, data quality filtering, and instrument malfunctions, LE measured by the eddy covariance (EC) is temporally discontinuous at the hourly and daily scales. Machine-learning (ML) models effectively capture the complex relationships between LE and its influencing factors, demonstrating superior performance in filling LE data gaps. However, the selection of features in ML models often relies on empirical knowledge, with identical features frequently used across stations, leading to reduced modeling accuracy. Therefore, this study proposes an LE gap-filling model (SHAP-AWF-BO-LightGBM) that combines the Shapley additive explanations adaptive weighted fusion method with the Bayesian optimization light gradient-boosting machine algorithm. This is tested using data from three stations in the Heihe River Basin, China, representing different plant functional types. For 30 min interval missing LE data, the RMSE ranges from 17.90 W/m² to 20.17 W/m², while the MAE ranges from 10.74 W/m² to 14.04 W/m². The SHAP-AWF method is used for feature selection. First, the importance of SHAP features from multiple ensemble-learning models is adaptively weighted as the basis for feature input into the BO-LightGBM algorithm, which enhances the interpretability and transparency of the model. Second, data redundancy and the cost of collecting other feature data during model training are reduced, improving model calculation efficiency (reducing the initial number of features of different stations from 42, 46, and 48 to 10, 15, and 8, respectively). Third, under the premise of ensuring accuracy as much as possible, the gap-filling ratio for missing LE data at different stations is improved, and the adaptability of using only automatic weather station observation is enhanced (the improvement range is between 7.46% and 11.67%). Simultaneously, the hyperparameters of the LightGBM algorithm are optimized using a Bayesian algorithm, further enhancing the accuracy of the model. This study provides a new approach and perspective to fill the missing LE in EC measurement. Full article

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

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15 pages, 3129 KiB

Open AccessArticle

Evaluating Modeling Approaches for Phytoplankton Productivity in Estuaries

by Reed Hoshovsky, Frances Wilkerson, Alexander Parker and Richard Dugdale

Water 2025, 17(5), 747; https://doi.org/10.3390/w17050747 - 4 Mar 2025

Viewed by 474

Abstract

Phytoplankton comprise the base of the food web in estuaries and their biomass and rates of growth (productivity) exert a bottom-up control in pelagic ecosystems. Reliable means to quantify biomass and productivity are crucial for managing estuarine ecosystems. In many estuaries, direct productivity [...] Read more.

Phytoplankton comprise the base of the food web in estuaries and their biomass and rates of growth (productivity) exert a bottom-up control in pelagic ecosystems. Reliable means to quantify biomass and productivity are crucial for managing estuarine ecosystems. In many estuaries, direct productivity measurements are rare and instead are estimated with biomass-based models. A seminal example of this is a light utilization model (LUM) used to predict productivity in the San Francisco Estuary and Delta (SFED) from long timeseries data using an efficiency factor, ψ. Applications of the LUM in the SFED, Chesapeake Bay, and the Dutch Scheldt Estuary highlight significant interannual and regional variability, indicating the model must be recalibrated often. The objectives of this study are to revisit the LUM approach in the SFED and assess a chlorophyll-a to carbon model (CCM) that produces a tuning parameter, Ω. To assess the estimates of primary productivity resulting from the models, productivity was directly measured with a ¹³C-tracer at nine locations during 22 surveys using field-derived phytoplankton incubations between March and November of 2023. For this study, ψ was determined to be 0.42 ± 0.02 (r² = 0.89, p < 0.001, CI₉₅ = 319). Modeling productivity using an alternative CCM approach (Ω = 3.47 × 10⁴ ± 1.7 × 10³, r² = 0.84, p < 0.001, CI₉₅ = 375) compared well to the LUM approach, expanding the toolbox for estuarine researchers to cross-examine productivity models. One practical application of this study is that it confirms an observed decline in ψ, suggesting a decline in light utilization by phytoplankton in the SFED. This highlights the importance of occasionally recalibrating productivity models in estuaries and leveraging multiple modeling approaches to validate estimations before application in ecological management decision making. Full article

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

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18 pages, 3483 KiB

Open AccessArticle

Bibliometric Analysis of Hydrothermal Wastewater Treatment in the Last Two Decades

by Abel Santillan-Angeles, Candido Mendoza-Perez, Edwin Villagrán, Francisco Garcia and Jorge Flores-Velazquez

Water 2025, 17(5), 746; https://doi.org/10.3390/w17050746 - 4 Mar 2025

Viewed by 510

Abstract

The reuse of wastewater expands its area of influence due in part to the water crisis and the increase in population in urban areas. Technologically, the methods of the treatment and separation of toxic agents have been diversified to provide water with a [...] Read more.

The reuse of wastewater expands its area of influence due in part to the water crisis and the increase in population in urban areas. Technologically, the methods of the treatment and separation of toxic agents have been diversified to provide water with a second use. The objective of this work was to evaluate the growth and development of science in the hydrothermal wastewater treatment (HTAR) through a bibliometric analysis. The keywords directly obtained from the treatment method were used in order to carry out the integration of related published research, and the terms used in the search both separately and crossly were “treatment, hydrothermal, wastewater” in the database from SCOPUS; 97 response records were filtered to 87 documents that were analyzed using BIBLIMETRIX as the R Statistical interface. According to the results obtained, the trend of documents published is shown, with 17 articles in 2023 and 21 in 2024. The author with the highest number of contributions on the topic is Yuanhui Zhang. The countries most involved in this issue are China, the U.S.A., and Japan; China was the one with the highest number of publications. The scientific and technological development regarding the HTAR is shown; and that, technology is aimed at the use and generation of energy. In addition, hydrothermal liquefaction treatment is being investigated to generate biocrude and bio-oils; the hydrothermal carbonization treatment for the generation of hydrochar; and the hydrothermal gasification treatment to produce methane and hydrogen; all from biomass with a high moisture content. Full article

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

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19 pages, 2233 KiB

Open AccessArticle

Quantifying Temporal Dynamics of E. coli Concentration and Quantitative Microbial Risk Assessment of Pathogen in a Karst Basin

by Shishir K. Sarker, Ryan T. Dapkus, Diana M. Byrne, Alan E. Fryar and Justin M. Hutchison

Water 2025, 17(5), 745; https://doi.org/10.3390/w17050745 - 4 Mar 2025

Viewed by 648

Abstract

Karst aquifers can be highly productive water sources but are vulnerable to contamination by pathogens because of integrated surface and subsurface drainage. Our study focuses on the karstic Royal Spring basin in Kentucky, encompassing urban and agricultural land uses. The city of Georgetown [...] Read more.

Karst aquifers can be highly productive water sources but are vulnerable to contamination by pathogens because of integrated surface and subsurface drainage. Our study focuses on the karstic Royal Spring basin in Kentucky, encompassing urban and agricultural land uses. The city of Georgetown distributes treated water from Royal Spring to over 33,000 customers. We examined E. coli dynamics at Royal Spring from June 2021 through June 2022, assessing variability under wet versus dry weather conditions. We also used quantitative microbial risk assessment (QMRA) to estimate potential health risks from the pathogenic bacterium E. coli O157:H7. E. coli concentrations in weekly water samples varied from 12 to 1732.8 MPN/100 mL, with a geometric mean of 117.2 MPN/100 mL. The mean concentration in wet periods was approximately double that during dry conditions. Because the pathogen was not detected by quantitative PCR (qPCR), we conducted QMRA based on literature data for water treatment plant operations (occupational) and recreational activities near the spring. The median probability of annual infection was 5.11 × 10⁻³ for occupational exposure and 1.45 × 10⁻² for recreational exposure. Uncertainty and sensitivity analyses revealed that health risks were most sensitive to the pathogen/E. coli ratio and ingestion rate. Although the pathogen was not detected by qPCR, the presence of E. coli suggests potential fecal contamination. This highlights the importance of continued monitoring and investigation of different detection methods to better understand potential health risks in karst systems. Full article

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

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15 pages, 9675 KiB

Open AccessArticle

Regenerable Biochar Catalyst from Biogas Residue for Peroxymonosulfate Activation in Bisphenol A-Containing Wastewater Treatment

by Yating Pan, Xue Yang, Haijuan Wei, Xiang Liu, Pan Wang, Nina Duan and Miao Lin

Water 2025, 17(5), 744; https://doi.org/10.3390/w17050744 - 4 Mar 2025

Viewed by 608

Abstract

The biogas residue (BR) from the anaerobic digestion of sludge poses a threat to the environment due to the presence of toxic and hazardous substances. Furthermore, emerging contaminants, such as bisphenol A (BPA), are widespread in domestic and industrial wastewater, requiring efficient and [...] Read more.

The biogas residue (BR) from the anaerobic digestion of sludge poses a threat to the environment due to the presence of toxic and hazardous substances. Furthermore, emerging contaminants, such as bisphenol A (BPA), are widespread in domestic and industrial wastewater, requiring efficient and sustainable treatment technologies. In this study, the BR-based biochar was pyrolyzed from urea-modified BR and employed as a catalyst to activate peroxymonosulfate (PMS) for BPA degradation. With BR-based biochar pyrolyzed at 750 °C as a catalyst, 20 mg/L of BPA was completely removed. Free radical detection confirmed that hydroxyl radical (•OH) and sulfate radical (•SO₄⁻) generation decreased with the increase in catalyst reuse times. The X-ray photoelectron spectra showed that the catalyst deactivation mainly resulted from -COOH and C-OH group loss, which acted as active sites for generating •OH and •SO₄⁻, and HCl or NaOH regeneration for catalysts could recover oxygen-containing functional groups, boosting BPA removal from 54.7% to 91.5% and 100%, respectively. Thermal regeneration could only enlarge the catalyst’s specific surface area (SSA) to recover adsorption capacity, but might not restore the free radical generation capability. This research offered a theoretical basis for the sustainable utilization of BR and provided a reference for reusing catalysts in wastewater treatment. Full article

(This article belongs to the Topic Advanced Oxidation Processes for Wastewater Purification)

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29 pages, 7495 KiB

Open AccessArticle

Failure Mechanism and Risk Evaluation of Water Inrush in Floor of Extra-Thick Coal Seam

by Min Cao, Shangxian Yin, Huiqing Lian, Xu Wang, Guoan Wang, Shuqian Li, Qixing Li and Wei Xu

Water 2025, 17(5), 743; https://doi.org/10.3390/w17050743 - 3 Mar 2025

Viewed by 444

Abstract

In this paper, we investigate the evolution characteristics of floor failure during pressured mining in extra-thick coal seams. A mechanical expression relating floor failure depth to seam thickness is established based on soil mechanics and mine pressure theory. The findings reveal a linear [...] Read more.

In this paper, we investigate the evolution characteristics of floor failure during pressured mining in extra-thick coal seams. A mechanical expression relating floor failure depth to seam thickness is established based on soil mechanics and mine pressure theory. The findings reveal a linear relationship between seam thickness and floor failure depth; specifically, as the coal seam thickens, the depth of floor failure increases. To simulate the mining process of extra-thick coal seams, FLAC3D numerical simulation software is utilized. We analyze the failure process, failure depth, and the behavior of water barriers at the coal seam floor under the influence of extra-thick coal seam mining from three perspectives: rock displacement evolution in the floor, stress evolution in the floor, and plastic deformation. Based on geological characteristics observed in the Longwanggou mine field, we establish a main control index system for assessing floor water-inrush risk. This system comprises 11 primary control factors: water abundance, permeability, water pressure, complexity of geological structure, structural intersection points, thickness of both actual and equivalent water barriers, thickness ratio of brittle–plastic rocks to coal seams, as well as depths related to both coal seams and instances of floor failure. Furthermore, drawing upon grey system theory and fuzzy mathematics within uncertainty mathematics frameworks leads us to propose an innovative approach—the interval grey optimal clustering model—designed specifically for risk assessment concerning potential floor water inrush during pressured mining operations involving extra-thick coal seams. This method of mine water inrush risk assessment is applicable for popularization and implementation in mines with analogous conditions, and it holds practical significance for the prevention of mine water damage. Full article

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19 pages, 7180 KiB

Open AccessArticle

Self-Excited Oscillating Cavitation Jet Combined with Fenton’s Reagent for Tetracycline Degradation in Water: Optimization of Geometric Structure and Operating Parameters

by Jian Wang, Chang Yang, Yanqing Wang, Mingzhan Zhu, Jingfeng Sun, Bin Ji and Shiwei Xie

Water 2025, 17(5), 742; https://doi.org/10.3390/w17050742 - 3 Mar 2025

Viewed by 484

Abstract

This study utilizes a novel self-excited oscillatory hydrodynamic cavitation (HC) device for tetracycline degradation. The effects of key parameters, including cavity length, inlet-to-outlet diameter ratio, and operational conditions (inlet pressure of 0.3–0.8 MPa), as well as the initial tetracycline concentration (5.0–20.0 mg/L) and [...] Read more.

This study utilizes a novel self-excited oscillatory hydrodynamic cavitation (HC) device for tetracycline degradation. The effects of key parameters, including cavity length, inlet-to-outlet diameter ratio, and operational conditions (inlet pressure of 0.3–0.8 MPa), as well as the initial tetracycline concentration (5.0–20.0 mg/L) and the addition of common inorganic anions, on tetracycline degradation are systematically explored. The results show that the self-excited oscillating hydrodynamic cavitator, with a cavity length of 23.0 mm and an inlet-to-outlet diameter ratio of 0.75 (inlet diameter: 3.0 mm; outlet diameter: 4.0 mm), generates a strong HC effect. Under an inlet pressure of 0.5 MPa and an initial tetracycline concentration of 10.0 mg/L, the degradation rate reaches 51.32 ± 0.56%. The three common inorganic anions, CO₃²⁻, NO₃⁻, and SO₄²⁻, all inhibit tetracycline degradation. The addition of Fenton’s reagent further enhances the degradation efficiency of tetracycline via hydrodynamic cavitation. The optimal molar ratio of Fenton’s reagent (TC:Fe²⁺:H₂O₂ = 1:1:10) is determined, resulting in a tetracycline degradation rate of 85.91 ± 0.29% after 120 min of reaction. The self-excited oscillatory hydrodynamic cavitator proposed in this study offers a simple structure, high reliability, and improved degradation efficiency, providing a novel approach to antibiotic treatment. Full article

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

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Water, Volume 17, Issue 5 (March-1 2025) – 166 articles

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