Water

13 pages, 2844 KiB

Open AccessArticle

Influence of Distribution Spacing on Intraspecific Competition in the Brown Seaweed Sargassum thunbergii Along the Luhua Coast, China

by Fukun Gui, Kai Zong, Jinhuai Ni, Sunzhaocong Lan, Jianpeng Lu, Tumusenge Daniel, Dejun Feng, Xu Yang, Guangyang Zhang, Lili Mei, Jun Li, Xueping Lin, Xunmeng Li, Hongzhou Chen and Qingping Zou

Water 2025, 17(12), 1735; https://doi.org/10.3390/w17121735 (registering DOI) - 8 Jun 2025

Abstract

Sargassum thunbergii is a dominant seaweed species in the intertidal zone along the coast of China. It provides various ecological services, such as primary productivity, marine carbon sequestration, and water purification. To investigate the population structure characteristics of Sargassum thunbergii, the Hegyi [...] Read more.

Sargassum thunbergii is a dominant seaweed species in the intertidal zone along the coast of China. It provides various ecological services, such as primary productivity, marine carbon sequestration, and water purification. To investigate the population structure characteristics of Sargassum thunbergii, the Hegyi competition model was employed to quantify intraspecific competition within populations in the intertidal zone of Luhua Island, China. The results showed that the competition intensity decreased as a power function (y = 1.93x^−0.89, R² = 0.28) with increasing seaweed height. Intraspecific competition had minimal effects on seaweeds taller than 50 cm. Seaweeds at lower population levels exhibited more stable competition indices. Therefore, the model can reliably predict intraspecific competition intensity in Sargassum thunbergii. The sample circle method was applied to identify an optimal intraspecific competitive range of 50 cm for intertidal populations of Sargassum thunbergii. This study provides scientific guidance for seaweed spacing and rational harvesting during ecological restoration. Moreover, it offers valuable insight for conserving other macroalgae, such as Sargassum fusiforme, and restoring seaweed beds ecologically. Full article

(This article belongs to the Special Issue Algae Distribution, Risk, and Prediction)

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24 pages, 3847 KiB

Open AccessArticle

Evaluation of Water-Inrush Risk and Water-Preserved Mining Under Goaf Water

by Hao Jiao, Zhijiang Lun, Yanxiao Ni, Zhiguo Chang, Limin Fan and Liqiang Ma

Water 2025, 17(12), 1734; https://doi.org/10.3390/w17121734 (registering DOI) - 8 Jun 2025

Abstract

In coal seam mining operations, the presence of overlying water bodies presents persistent challenges, particularly during multi-seam extraction, where water accumulation in upper seam goafs requires careful management. This study examined the Lingzhida Coal Mine, focusing on the geological conditions of the 3# [...] Read more.

In coal seam mining operations, the presence of overlying water bodies presents persistent challenges, particularly during multi-seam extraction, where water accumulation in upper seam goafs requires careful management. This study examined the Lingzhida Coal Mine, focusing on the geological conditions of the 3# seam (upper) and the 15# seam (lower), as well as the distribution of water accumulation in the corresponding goafs. The mechanism of water inrush from the upper goaf was studied, and the role of the water-resisting belt (WRB) is suggested. By utilizing empirical equations and field measurements, a method for calculating the floor fracture depth of the 3# seam and the roof fracture height of the 15# seam was derived through multi-linear regression analysis. Based on the relationship between the thickness of the WRB (H_w) and the protective layer (H_p), a classification criterion for the water-inrush risk (the likelihood of water entering the lower seam from the upper goaf) is proposed. The mining area was divided into four risk zones: high-risk (H_w < 0), medium-risk (0 ≤ H_w < 0.5H_p), low-risk (0.5H_p ≤ H_w < H_p), and safe (H_w ≥ H_p). Then, an adaptive zoning approach for water-preserved mining was introduced, considering the spatial distribution of goaf water. This approach incorporates water-preserved mining technologies, including the staggered layout of working faces, reduction in mining height, and the transfer–storage of water resources. These research findings provide crucial insights for ensuring the safe and efficient extraction of the multi-seam. Full article

(This article belongs to the Special Issue Groundwater Environmental Impacts and Control Strategies of Coal Mining and Energy Development/Storage Activities)

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11 pages, 553 KiB

Open AccessArticle

A Call for Action: Improving Individual Well Management in Slovakia

by Miroslava Sovičová, Tibor Baška, Jana Zibolenová, Henrieta Hudečková, Mária Tatarková, Milada Eštóková, Zuzana Valovičová, Tibor Záborský and Mária Marušiaková

Water 2025, 17(12), 1733; https://doi.org/10.3390/w17121733 (registering DOI) - 8 Jun 2025

Abstract

Background: While public water supplies are regulated by Directive (EU) 2020/2184, inconsistencies in member state legislation for individual wells pose health risks. The study investigates the management of Slovak wells, providing insights to inform and potentially strengthen national water policies. Methods: The survey-based [...] Read more.

Background: While public water supplies are regulated by Directive (EU) 2020/2184, inconsistencies in member state legislation for individual wells pose health risks. The study investigates the management of Slovak wells, providing insights to inform and potentially strengthen national water policies. Methods: The survey-based study collected data via online and in-person questionnaires during March 2024. It collected retrospective information on well characteristics, usage, stewardship practices, and water quality concerns. Results: We received 251 responses from 52 Slovak districts. The well water for drinking was used by 122 (48.6%) households, with notable regional variations. Only 41.0% of the respondents conducted a proper technical inspection of their wells within the past year. There has been an increase in the use of wells since the millennium. Individuals who drank well water were significantly more likely to conduct water quality tests (p < 0.05). The recommended frequency of technical inspections and annual testing was not reached in either well owners who drink well water or those with wells who drink water from other sources. Conclusions: The amendment of legislation specifically targeting individual wells, along with educational campaigns, appears crucial for well stewardship in Slovakia. The study provides data for further research and public health interventions. Full article

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

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23 pages, 4704 KiB

Open AccessArticle

A Hierarchical Water Supply–Demand Regulation Model Coupling System Dynamics and Feedback Control Mechanisms: A Case Study in Wu’an City, China

by Renlong Wang, Shiwei Zhang, Jinxia Sha, Bin Liu, Dasheng Zhang and Boxin Wang

Water 2025, 17(12), 1732; https://doi.org/10.3390/w17121732 (registering DOI) - 8 Jun 2025

Abstract

Water scarcity has become a critical global challenge, particularly in rapidly developing regions where water demand often exceeds sustainable supply capacities. Traditional “demand-driven” water management approaches have proven inadequate to address this imbalance, necessitating the development of more sophisticated “supply-driven” solutions. This study [...] Read more.

Water scarcity has become a critical global challenge, particularly in rapidly developing regions where water demand often exceeds sustainable supply capacities. Traditional “demand-driven” water management approaches have proven inadequate to address this imbalance, necessitating the development of more sophisticated “supply-driven” solutions. This study presents a groundbreaking System Dynamics (SD)-Feedback-Hierarchical Water Demand (SD-F-HWD) model that advances water resources management through three contributions. First, the model substantially extends conventional water demand hierarchy methods by developing a comprehensive classification framework with enhanced sector-specific criteria for industrial, agricultural, and ecological needs. Second, the innovative feedback regulation mechanism resolves persistent challenges from previous studies, including ambiguous control parameters and system instability. Third, the model establishes a unified analytical platform that effectively integrates these components for robust supply–demand equilibrium analysis. Validation in Wu’an City, Hebei Province—a representative water-stressed industrial region in northern China—demonstrated the model’s effectiveness. Under low-flow conditions (P = 75%), total water demand decreased by 11.24% while rigid demand was reduced by 8.50%. For normal flow conditions (P = 50%), corresponding reductions reached 9.88% and 6.99%, respectively. Crucially, all adjustments remained within practical policy implementation boundaries, demonstrating the model’s real-world applicability. The SD-F-HWD model offers a practical and scalable solution for sustainable water allocation in water-stressed regions through its integrated methodological framework. Full article

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

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26 pages, 3045 KiB

Open AccessArticle

Not a Drop to Drink: Addressing Nigeria’s Deepening Freshwater Crisis

by Julius Irene, Bridget Nneka Irene and Chux Daniels

Water 2025, 17(12), 1731; https://doi.org/10.3390/w17121731 (registering DOI) - 7 Jun 2025

Abstract

Nigeria is currently grappling with an acute freshwater crisis, characterized by a stark contradiction where abundant water resources coexist with a widespread lack of access to safe and reliable water. This study examines the complex interplay of factors driving this crisis. It highlights [...] Read more.

Nigeria is currently grappling with an acute freshwater crisis, characterized by a stark contradiction where abundant water resources coexist with a widespread lack of access to safe and reliable water. This study examines the complex interplay of factors driving this crisis. It highlights how climate change and the degradation of critical infrastructure and water management systems have significantly reduced the resilience of freshwater systems. This study draws on survey data to assess public perceptions of water scarcity and its causes, revealing a public consensus on the impacts and challenges of freshwater scarcity. This finding points to the pervasive nature of water insecurity in the surveyed population and suggests that reliable access to freshwater remains elusive for many. The findings emphasize the need for integrated, climate-resilient policies that include ecosystem restoration, infrastructure modernization, pollution control, and inclusive, community-based governance frameworks. Addressing these multifaceted challenges is essential not only for improving freshwater access but also for advancing public health, reducing conflict, and fostering sustainable development. This research contributes to the growing body of knowledge on water security in the Global South and outlines pathways for transformative water governance in Nigeria. Full article

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

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14 pages, 10181 KiB

Open AccessArticle

Degradation of Tetracycline Hydrochloride by Cobalt-Doped Biochar-Activated Peroxymonosulfate

by Bingliang Su, Yuecheng Zhong, Xiaojie Zhuang, Liyong Zhang, Minghai Zhang, Jia Chen, Hui Liang, Yue Mu, Tao Xu, Yonghua Chen, Rongkui Su, Xiaofeng Hao and Yiting Luo

Water 2025, 17(12), 1730; https://doi.org/10.3390/w17121730 (registering DOI) - 7 Jun 2025

Abstract

The presence of tetracycline hydrochloride (TC) in the environment poses significant risks to human health and ecological stability, necessitating the development of effective and rapid removal strategies. In this research, we investigate the efficacy of degrading tetracycline hydrochloride using cobalt-doped-biochar (Co-BC)-activated peroxymonosulfate (PMS) [...] Read more.

The presence of tetracycline hydrochloride (TC) in the environment poses significant risks to human health and ecological stability, necessitating the development of effective and rapid removal strategies. In this research, we investigate the efficacy of degrading tetracycline hydrochloride using cobalt-doped-biochar (Co-BC)-activated peroxymonosulfate (PMS) and the underlying mechanisms of this process. The research objectives and conclusions were as follows: (1) Co-BC materials were synthesized from balsa wood powder through a process of impregnation followed by high-temperature calcination. Characterization techniques such as SEM, XRD, FTIR, and XPS were used to confirm the material’s structure and composition. (2) In a TC solution of 20 mg L⁻¹, the use of 100.0 mg L⁻¹ of Co-BC and 1.0 mM PMS led to a TC degradation efficiency of 96.2% within 30 min. (3) The Co-BC+PMS system exhibited wide pH adaptability (4.34–9.02) and strong resistance to environmental matrix interference (Cl⁻,

{NO}_{3}^{-}

, and

{SO}_{4}^{2 -}

). (4) Free-radical quenching experiments indicated that sulfate radicals (

S O_{4}^{• -}

) were the primary reactive species in TC degradation. The 11 intermediates of TC were analyzed using LC-MS, and two possible degradation pathways were deduced. In summary, this study offers significant, valuable insights into and technical support for the green, efficient, and environmentally friendly removal of antibiotics from sewage. Full article

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

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20 pages, 2757 KiB

Open AccessArticle

Multi-Criteria Decision Making: Sustainable Water Desalination

by Daniel Li, Mohamed Galal Hassan-Sayed, Nuno Bimbo, Clara Bartram and Ihab M. T. Shigidi

Water 2025, 17(12), 1729; https://doi.org/10.3390/w17121729 (registering DOI) - 7 Jun 2025

Abstract

With an increasingly more urbanised global population, surface water and groundwater resources are being/have become outpaced by growing demand. The oceans could address this pertinent scarcity issue, once their high-salinity content is removed. Water desalination could thus be a crucial pathway towards addressing [...] Read more.

With an increasingly more urbanised global population, surface water and groundwater resources are being/have become outpaced by growing demand. The oceans could address this pertinent scarcity issue, once their high-salinity content is removed. Water desalination could thus be a crucial pathway towards addressing global water scarcity. However, conventional desalination is known to be highly energy-intensive, with limited scalability and potentially significant negative environmental impacts. Multi-criteria Decision Making (MCDM) presents a novel approach towards sustainable water desalination based on sustainability-related criteria. The Fuzzy Analytical Hierarchy Process (FAHP) was implemented to determine the most optimal small-scale, modularised, and remote reverse osmosis (RO) desalination plant configurations. Twelve configurations were assessed, based on four plant capacities (50, 100, 150, and 200 m³/day) and three diesel-to-solar photovoltaic energy configurations (100–0%, 75–25%, and 60–40%). The hybridised diesel-to-solar configurations were generally ranked higher, particularly when less reliant on diesel, and at small(er) capacities, in terms of the criteria: sustainability, overall efficiency, and standalone potential while maintaining competitive costs. This can likely be attributed to their relatively lower fuel and energy consumption and associated costs. Further research should aim to consider additional criteria, such as battery cost, as well as life cycle assessments that include transportation-related costs/emissions. Full article

(This article belongs to the Special Issue Novel Methods in Wastewater and Stormwater Treatment)

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19 pages, 2243 KiB

Open AccessArticle

Divergent Response of Blue Carbon Components and Microbial Communities in Sediments to Different Shellfish Zones of Geligang, Liaodong Bay, China

by Qingbiao Hu, Bingyu Li, Yongan Bai, Fangliang Zheng, Muzhan Sun, Ruiqi Zeng, Xuetong Wang, Xiaodong Li and Chunyu Zhu

Water 2025, 17(12), 1728; https://doi.org/10.3390/w17121728 (registering DOI) - 7 Jun 2025

Abstract

Coastal wetlands are critical components of blue carbon ecosystems, yet the functional roles of benthic shellfish species in regulating sediment carbon dynamics are not yet fully elucidated. To address this knowledge gap, we investigated the effects of different shellfish zones—gastropods (Bullacta exarata [...] Read more.

Coastal wetlands are critical components of blue carbon ecosystems, yet the functional roles of benthic shellfish species in regulating sediment carbon dynamics are not yet fully elucidated. To address this knowledge gap, we investigated the effects of different shellfish zones—gastropods (Bullacta exarata, Umbonium thomasi) and bivalves (Mactra veneriformis, Meretrix meretrix, Potamocorbula laevis)—on sediment carbon fractions and microbial communities in representative intertidal wetlands of Liaodong Bay, China. We analyzed dissolved organic carbon (DOC), particulate organic carbon (POC), microbial biomass carbon (MBC), enzyme activities, and microbial genomic profiles, with particular emphasis on carbon fixation gene abundance within the top 0–10 cm of sediment. The results showed that POC and MBC levels in gastropod zones were 56.11% and 99.83% higher, respectively, than in bivalve zones, while carbon fixation gene abundance was 14.54% lower. Structural equation modeling (SEM) further revealed that shellfish type had a significant direct effect on MBC (λ = 0.824, p < 0.001). This study provides novel evidence that shellfish community composition regulates blue carbon storage through both biogeochemical and microbial pathways, highlighting the importance of species-specific management in shellfish aquaculture to enhance carbon sequestration. These findings offer a theoretical foundation for future assessments of coastal wetland carbon sinks and ecosystem service valuation. Full article

(This article belongs to the Topic Dynamic Monitoring and Estimation of Coastal Wetland Blue Carbon Ecosystems)

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18 pages, 3601 KiB

Open AccessArticle

Application of COMSOL Multiphysics Model in Studying Effects of Straw Addition on Dewatering Performance of Residual Sludge During Freeze–Thaw Cycles

by Zirui Guo, Jiawei Wang, Yao Wang, Riguang Chi, Xujin Gong and Zhiqiang Chen

Water 2025, 17(12), 1727; https://doi.org/10.3390/w17121727 (registering DOI) - 7 Jun 2025

Abstract

Freeze–thaw (F/T) technology is an environmentally friendly and efficient method for residual sludge treatment. This study investigates the enhancement of sludge dewatering performance through the addition of straw during F/T cycles. A mathematical model was established using the Box–Behnken central composite design and [...] Read more.

Freeze–thaw (F/T) technology is an environmentally friendly and efficient method for residual sludge treatment. This study investigates the enhancement of sludge dewatering performance through the addition of straw during F/T cycles. A mathematical model was established using the Box–Behnken central composite design and validated via COMSOL Multiphysics simulations. The optimal conditions were identified as freezing at −16 °C for 24 h, with 12.5 freeze–thaw cycles and a straw mixing ratio of 20%, reducing the sludge moisture content from 62.7% to 35.9%. The specific resistance to filtration (SRF) and cake moisture content decreased significantly with increasing straw addition, reaching a minimum SRF of 1.30 × 10¹² m/kg at the optimal straw ratio. Straw conditioning also intensified the combustion stage of the sludge by increasing the maximum weight loss rate and elevating the thermal decomposition temperature. Numerical simulations confirmed the experimental results, demonstrating that straw addition significantly improves sludge dewaterability by modifying heat and mass transfer mechanisms. Full article

(This article belongs to the Special Issue Environmental Biotechnology Applied to Water and Wastewater Treatment Processes)

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20 pages, 16550 KiB

Open AccessArticle

Non-Negligible Influence of Gravel Content in Slip Zone Soil: From Creep Characteristics to Landslide Response Patterns

by Bo Xu, Xinhai Zhao, Jin Yuan, Shun Dong, Xuhuang Du, Longwei Yang, Bo Peng and Qinwen Tan

Water 2025, 17(12), 1726; https://doi.org/10.3390/w17121726 (registering DOI) - 7 Jun 2025

Abstract

The creep mechanical behavior of the slip zone soil is distinctive and assumes a vital role in the identification and prediction of landslide evolution, but the rock content and structure dictate its creep properties. This study examines the Outang landslide in the reservoir [...] Read more.

The creep mechanical behavior of the slip zone soil is distinctive and assumes a vital role in the identification and prediction of landslide evolution, but the rock content and structure dictate its creep properties. This study examines the Outang landslide in the reservoir region of middle Yangtze River, where the slip zone soil shows considerable variability in particle size distribution, with gravel content varying between 35% and 55%. To investigate the creep characteristics of the slip zone soil, large-scale direct shear creep tests were conducted, focusing on the variations in peak strength and long-term strength under different gravel content conditions. PFC^3D numerical simulations were subsequently performed to elucidate the internal mechanisms connecting gravel content, microstructure, and macroscopic mechanical strength. A three-dimensional continuous-discrete coupled model was built to investigate the influence of gravel content on landslide deformation features, accounting for fluctuations in gravel content. The numerical findings indicate that gravel content markedly affects the displacement and deformation characteristics of the landslide. As the gravel concentration rises, landslide displacement progressively diminishes, with elevated gravel content enhancing the structural integrity of the landslide mass. This study underscores gravel content as a pivotal element in landslide deformation and reinforces its significance in assessing landslide stability and forecasting. Full article

(This article belongs to the Special Issue Geotechnics and Geostructures Modelling for Hydrodynamic-Driven Landslides: Prediction and Control)

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29 pages, 21376 KiB

Open AccessArticle

Numerical Simulation of Fracture Failure Propagation in Water-Saturated Sandstone with Pore Defects Under Non-Uniform Loading Effects

by Gang Liu, Yonglong Zan, Dongwei Wang, Shengxuan Wang, Zhitao Yang, Yao Zeng, Guoqing Wei and Xiang Shi

Water 2025, 17(12), 1725; https://doi.org/10.3390/w17121725 (registering DOI) - 7 Jun 2025

Abstract

The instability of mine roadways is significantly influenced by the coupled effects of groundwater seepage and non-uniform loading. These interactions often induce localized plastic deformation and progressive failure, particularly in the roof and sidewall regions. Seepage elevates pore water pressure and deteriorates the [...] Read more.

The instability of mine roadways is significantly influenced by the coupled effects of groundwater seepage and non-uniform loading. These interactions often induce localized plastic deformation and progressive failure, particularly in the roof and sidewall regions. Seepage elevates pore water pressure and deteriorates the mechanical properties of the rock mass, while non-uniform loading leads to stress concentration. The combined effect facilitates the propagation of microcracks and the formation of shear zones, ultimately resulting in localized instability. This initial damage disrupts the mechanical equilibrium and can evolve into severe geohazards, including roof collapse, water inrush, and rockburst. Therefore, understanding the damage and failure mechanisms of mine roadways at the mesoscale, under the combined influence of stress heterogeneity and hydraulic weakening, is of critical importance based on laboratory experiments and numerical simulations. However, the large scale of in situ roadway structures imposes significant constraints on full-scale physical modeling due to limitations in laboratory space and loading capacity. To address these challenges, a straight-wall circular arch roadway was adopted as the geometric prototype, with a total height of 4 m (2 m for the straight wall and 2 m for the arch), a base width of 4 m, and an arch radius of 2 m. Scaled physical models were fabricated based on geometric similarity principles, using defect-bearing sandstone specimens with dimensions of 100 mm × 30 mm × 100 mm (length × width × height) and pore-type defects measuring 40 mm × 20 mm × 20 mm (base × wall height × arch radius), to replicate the stress distribution and deformation behavior of the prototype. Uniaxial compression tests on water-saturated sandstone specimens were performed using a TAW-2000 electro-hydraulic servo testing system. The failure process was continuously monitored through acoustic emission (AE) techniques and static strain acquisition systems. Concurrently, FLAC^3D 6.0 numerical simulations were employed to analyze the evolution of internal stress fields and the spatial distribution of plastic zones in saturated sandstone containing pore defects. Experimental results indicate that under non-uniform loading, the stress–strain curves of saturated sandstone with pore-type defects typically exhibit four distinct deformation stages. The extent of crack initiation, propagation, and coalescence is strongly correlated with the magnitude and heterogeneity of localized stress concentrations. AE parameters, including ringing counts and peak frequencies, reveal pronounced spatial partitioning. The internal stress field exhibits an overall banded pattern, with localized variations induced by stress anisotropy. Numerical simulation results further show that shear failure zones tend to cluster regionally, while tensile failure zones are more evenly distributed. Additionally, the stress field configuration at the specimen crown significantly influences the dispersion characteristics of the stress–strain response. These findings offer valuable theoretical insights and practical guidance for surrounding rock control, early warning systems, and reinforcement strategies in water-infiltrated mine roadways subjected to non-uniform loading conditions. Full article

(This article belongs to the Special Issue Theory and Technology of Water-Induced Geological Disaster Prevention and Water Resource Utilization in Mines)

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23 pages, 2716 KiB

Open AccessArticle

Calibration and Validation of the BMWP Index for the Assessment of Fluvial Systems in High Andean Mining Areas of Peru

by Manuel Emilio Hora Revilla, Alberto Ronal Gabriel Aguilar, José Luis Polo Corro, José Manuel Marchena Dioses, Eugenia López-López and Jacinto Elías Sedeño-Díaz

Water 2025, 17(12), 1724; https://doi.org/10.3390/w17121724 - 6 Jun 2025

Abstract

The High Andean region of Peru, characterized by a complex orography, has unique and highly biodiverse ecosystems. This region has several headwater basins that play a critical role in the hydrological cycle, providing diverse ecosystem services essential to sustain biodiversity and supply water [...] Read more.

The High Andean region of Peru, characterized by a complex orography, has unique and highly biodiverse ecosystems. This region has several headwater basins that play a critical role in the hydrological cycle, providing diverse ecosystem services essential to sustain biodiversity and supply water to human communities. Despite the importance of this region, it faces significant human intervention, particularly mining activities, which affect basin headwaters and jeopardize water security. This study aimed to calibrate the Biological Monitoring Working Party (BMWP) index to evaluate water quality in High Andean rivers in Peru affected by mining activities, using aquatic macroinvertebrates as bioindicators. We used a 15-year dataset (2008 to 2023) from three headwater basins in the High Andean region; this dataset included physicochemical water quality parameters, trace metals, and aquatic macroinvertebrates. The BMWP was calibrated for the High Andean region of Peru with this dataset (BMWP/PeIAZIM); afterward, it was validated to assess water quality in an area influenced by mining activities in this region. The results allowed us to differentiate between aquatic macroinvertebrate families tolerant to mining pollution and highly sensitive families. The sites heavily affected by mining activity returned very low BMWP/PeIAZIM scores; sites with no mining impact had the highest scores. These findings indicate that the calibrated index can be used for water resource management in the High Andean region, contributing to the conservation of its ecosystems. Full article

(This article belongs to the Special Issue Biodiversity of Freshwater Ecosystems: Monitoring and Conservation)

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14 pages, 8419 KiB

Open AccessArticle

Seasonal Water Column Stratification and Manganese and Iron Distribution in a Water Reservoir: The Case of Pinios Dam (Western Greece)

by Alexis Ramfos, Ioannis Sarris, Luca Lämmle, Dionisis Christodoulopoulos, Marinos Alexandridis, Maria Michalopoulou, Nikolaos Depountis, Sarah Faulwetter, Nikolaos Avrantinis, Evangelos Tsiotsis, Stefanos Papazisimou and Pavlos Avramidis

Water 2025, 17(12), 1723; https://doi.org/10.3390/w17121723 - 6 Jun 2025

Abstract

Climate change and extreme events such as droughts, heavy rainfall and flooding can influence the water column stratification in reservoir dams, decrease storage capacity, increase sediment and pollutant loads and, as a result, affect water quality. The seasonal variation in the water column [...] Read more.

Climate change and extreme events such as droughts, heavy rainfall and flooding can influence the water column stratification in reservoir dams, decrease storage capacity, increase sediment and pollutant loads and, as a result, affect water quality. The seasonal variation in the water column stratification of reservoirs is an important parameter for the study of dam life cycle as well as water management and use. In the present study a detailed bathymetric survey was carried out, and a digital elevation model (DEM) of the reservoir was constructed. Seasonal physicochemical monitoring data such as temperature, dissolved oxygen, pH and conductivity are presented. The seasonal thermal stratification was recorded, resulting in an isolated hypolimnion where anoxic layers formed below 17 m in summer and autumn. Manganese and iron concentrations exhibited values higher than 150 mg/L in the anoxic hypolimnion during summer and autumn, indicating solubilization from the sediment. The observed seasonal and depth-dependent variations in physicochemical parameters underline the reservoir’s susceptibility to eutrophication and metal mobilization, particularly during stratified periods. These findings are critical for designing management strategies to mitigate potential water quality issues. Full article

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

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14 pages, 1935 KiB

Open AccessArticle

Evaluation of Discharge Measurement Uncertainty of a Surface Image Velocimeter

by Junhyeong Lee, Kwonkyu Yu and Byungman Yoon

Water 2025, 17(12), 1722; https://doi.org/10.3390/w17121722 - 6 Jun 2025

Abstract

This study aims to develop a framework for evaluating the uncertainty of a surface image velocimeter (SIV) based on the Guide to the Expression of Uncertainty in Measurement (GUM) standard. To achieve this, the uncertainty factors of the SIV were thoroughly reviewed and [...] Read more.

This study aims to develop a framework for evaluating the uncertainty of a surface image velocimeter (SIV) based on the Guide to the Expression of Uncertainty in Measurement (GUM) standard. To achieve this, the uncertainty factors of the SIV were thoroughly reviewed and categorized into those that can be directly incorporated into the functional equation for surface velocity calculation and those that cannot. Factors that can be included in the velocity calculation equation primarily involve image displacement measurement and the accurate determination of the time interval between successive stationary images. Conversely, parameters and image quality were identified as uncertainty factors that are not directly integrated into the velocity calculation equation. Based on the GUM standard, equations for calculating the uncertainty of surface velocity, depth-averaged velocity, and flow discharge measurements were developed. Furthermore, using the results from the standard uncertainty evaluation, assessments were performed for the velocity uncertainty of both surface velocity and depth-averaged velocity, as well as the flow rate measurement uncertainty of the SIV. We anticipate that the velocity and flow rate measurement uncertainty framework and the uncertainty analysis results for the SIV presented in this research will enhance the reliability of SIV-derived flow rate measurements, thereby contributing to more dependable flow rate determination. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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22 pages, 3049 KiB

Open AccessArticle

A Monographic Experimental Investigation into Flood Discharge Atomized Raindrop Size Distributions Under Low Ambient Pressure Conditions

by Dan Liu, Jijian Lian, Dongming Liu, Fang Liu, Bin Ma, Jizhong Shi, Linlin Yan, Yongsheng Zheng, Cundong Xu and Jinxin Zhang

Water 2025, 17(12), 1721; https://doi.org/10.3390/w17121721 - 6 Jun 2025

Abstract

The construction and operation of high dam projects at high altitudes have led to concerns about the effectiveness of flood discharge security predictions resulting from the greater flood discharge atomized rain caused by ambient pressure reduction. In this study, self-similar characteristics and variation [...] Read more.

The construction and operation of high dam projects at high altitudes have led to concerns about the effectiveness of flood discharge security predictions resulting from the greater flood discharge atomized rain caused by ambient pressure reduction. In this study, self-similar characteristics and variation in atomized raindrop size distributions are analyzed to understand the phenomenon of increased atomized rain intensity under low ambient pressure from a mesoscopic scale. The monographic experiments are characterized by a low ambient pressure range (0.66P₀–1.02P₀) and a high waterjet velocity range (13.89–15.74 m/s). When the ambient pressure decreases by 0.10P₀ (P₀ = 101.325 kPa) from the reference atmospheric pressure condition as the other conditions remain fixed, the total number concentration in a two-dimensional atomized raindrop spectrum (number/(54 cm²)) and the peak value of the individual three-dimensional number concentration (number/(m³·mm) increase, which can lead to the required industry standard protective level of atomized zones increasing by one level in some cases. In addition, the spectrum trend and typical particle size ranges of the atomized raindrop size distributions present self-similarity as the ambient pressure decreases. The above studies further confirm the effects of low-ambient pressure enhancement on flood discharge atomized rain intensity, which can provide a theoretical basis for the development of random splash simulation models characterized by low pressure for high-altitude hydropower stations. Full article

(This article belongs to the Topic Advances in Environmental Hydraulics)

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15 pages, 2270 KiB

Open AccessArticle

Soil Infiltration Characteristics and Driving Mechanisms of Three Typical Forest Types in Southern Subtropical China

by Yanrui Guo, Chongshan Wan, Shi Qi, Shuangshuang Ma, Lin Zhang, Gong Cheng, Changjiang Fan, Xiangcheng Zheng and Tianheng Zhao

Water 2025, 17(12), 1720; https://doi.org/10.3390/w17121720 - 6 Jun 2025

Abstract

Plant roots and soil properties play crucial roles in regulating soil hydrological processes, particularly in determining soil water infiltration capacity. However, the infiltration patterns and underlying mechanisms across different forest types in subtropical regions remain poorly understood. In this study, we measured the [...] Read more.

Plant roots and soil properties play crucial roles in regulating soil hydrological processes, particularly in determining soil water infiltration capacity. However, the infiltration patterns and underlying mechanisms across different forest types in subtropical regions remain poorly understood. In this study, we measured the infiltration characteristics of three typical stands (pure Phyllostachys edulis forest, mixed Phyllostachys edulis-Cunninghamia lanceolata forest, and pure Cunninghamia lanceolata forest) using a double-ring infiltrometer. Stepwise multiple regression and structural equation modeling (SEM) were employed to analyze the effects of root traits and soil physicochemical properties on soil infiltration capacity. The results revealed the following: (1) The initial infiltration rate (IIR), stable infiltration rate (SIR), and average infiltration rate (AIR) followed the order pure Phyllostachys edulis stand > mixed stand > pure Cunninghamia lanceolata stand. (2) Compared to the pure Cunninghamia lanceolata stand, the IIR, SIR, and AIR in the pure Phyllostachys edulis stand increased by 6.66%, 35.63%, and 28.51%, respectively, while those in the mixed stand increased by 28.79%, 28.82%, and 33.51%. (3) Fine root biomass, root length density, non-capillary porosity, and soil bulk density were identified as key factors influencing soil infiltration capacity. (4) Root biomass and root length density affected infiltration capacity through both direct pathways and indirect pathways mediated by alterations in non-capillary porosity and soil bulk density. These findings provide theoretical insights into soil responses to forest types and inform sustainable water–soil management practices in Phyllostachys edulis plantations. Full article

(This article belongs to the Section Hydrology)

23 pages, 3013 KiB

Open AccessReview

Recent Advances in Antibiotic Degradation by Ionizing Radiation Technology: From Laboratory Study to Practical Application

by Yuening Song, Yulin Wang and Jianlong Wang

Water 2025, 17(12), 1719; https://doi.org/10.3390/w17121719 - 6 Jun 2025

Abstract

The widespread presence of antibiotics in aquatic environments poses significant ecological and public health risks due to their persistence, antimicrobial activity, and contribution to resistance gene proliferation. This review systematically evaluated the advancements in antibiotic degradation using ionizing radiation (γ-rays and electron beam) [...] Read more.

The widespread presence of antibiotics in aquatic environments poses significant ecological and public health risks due to their persistence, antimicrobial activity, and contribution to resistance gene proliferation. This review systematically evaluated the advancements in antibiotic degradation using ionizing radiation (γ-rays and electron beam) from laboratory studies to practical applications. By using keywords such as “antibiotic degradation” and “ionizing irradiation OR gamma radiation OR electron beam,” 328 publications were retrieved from Web of Science, with China contributing 33% of the literature, and a number of global representative studies were selected for in-depth discussion. The analysis encompassed mechanistic insights into oxidative (•OH) and reductive (e_aq⁻) pathways, degradation kinetics influenced by absorbed dose (1–10 kGy), initial antibiotic concentration, pH, and matrix complexity. The results demonstrated ≥90% degradation efficiency for major antibiotic classes (macrolides, β-lactams, quinolones, tetracyclines, and sulfonamides), though mineralization remains suboptimal (<50% TOC removal). Synergistic integration with peroxymonosulfate (PMS), H₂O₂, or O₃ enhances mineralization rates. This review revealed that ionizing radiation is a chemical-free, compatible, and highly efficient technology with effective antibiotic degradation potential. However, it still faces several challenges in practical applications, including incomplete mineralization, matrix complexity in real wastewater, and operating costs. Further improvements and optimization, such as hybrid system development (e.g., coupling electron beam with other conventional technologies, such as flocculation, membrane separation, anaerobic digestion, etc.), catalytic enhancement, and life-cycle assessments of this emerging technology would be helpful for promoting its practical environmental application. Full article

(This article belongs to the Special Issue Advanced Oxidation and Photocatalytic Approaches for Efficient Degradation of Organic Pollutants in Water Treatment)

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18 pages, 4380 KiB

Open AccessArticle

Deep Learning-Based Retrieval of Chlorophyll-a in Lakes Using Sentinel-1 and Sentinel-2 Satellite Imagery

by Bongseok Jeong, Sunmin Lee, Joonghyeok Heo, Jeongho Lee and Moung-Jin Lee

Water 2025, 17(11), 1718; https://doi.org/10.3390/w17111718 - 5 Jun 2025

Abstract

Remote sensing and AI models have been utilized for monitoring Chlorophyll-a (Chl-a), a primary indicator of eutrophication across broad water bodies. Previous studies have primarily relied on optical remote sensing data for assessing Chl-a’s spectral characteristics. Synthetic-aperture radar (SAR) data, which contain valuable [...] Read more.

Remote sensing and AI models have been utilized for monitoring Chlorophyll-a (Chl-a), a primary indicator of eutrophication across broad water bodies. Previous studies have primarily relied on optical remote sensing data for assessing Chl-a’s spectral characteristics. Synthetic-aperture radar (SAR) data, which contain valuable information about surface algae containing Chl-a, remains underutilized despite its high potential for improving Chl-a retrieval accuracy. Therefore, this study aims to develop a Convolutional neural network (CNN) based Chl-a retrieval model utilizing both SAR data and optical data in Korean lakes. The model dataset was established by acquiring Chl-a concentration data and Sentinel-1/2 imagery from the Copernicus Open Access Hub. The CNN model trained on both optical and SAR data exhibited superior performance (R² = 0.7992, RMSE = 10.3282 mg/m³, RPD = 2.2315) compared with the model trained exclusively on optical data. Moreover, SAR data exhibited moderate variable importance among all variables, demonstrating their efficacy as input variables for Chl-a concentration estimation. Furthermore, the CNN model estimated Chl-a concentrations with a spatial distribution that matched the observed spatial heterogeneity of Chl-a concentrations. These results are expected to serve as a foundation for future research on remote monitoring of Chl-a using such data. Full article

(This article belongs to the Special Issue Water Modeling Using Combined Machine Learning and Fieldwork Investigation)

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15 pages, 1004 KiB

Open AccessArticle

Survey of School Direct-Drinking Water Access for Children and Youth in Shanghai, China

by Yuan-Shen Zhu, Bing-Qing Hu, Rong Zheng, Ya-Juan Wang, Wei-Wei Zheng and Min-Juan Yang

Water 2025, 17(11), 1717; https://doi.org/10.3390/w17111717 - 5 Jun 2025

Abstract

Background: Over the past decade, Shanghai primary and middle schools have installed and updated direct-drinking water facilities in compliance with local policies, but few studies have assessed the schools providing direct-drinking water access. Methods: A cross-sectional study was conducted with 167 public primary, [...] Read more.

Background: Over the past decade, Shanghai primary and middle schools have installed and updated direct-drinking water facilities in compliance with local policies, but few studies have assessed the schools providing direct-drinking water access. Methods: A cross-sectional study was conducted with 167 public primary, middle, and high schools across Pudong New Area, Shanghai during Autumn 2024. The type, location, and working condition of all direct-drinking water facilities throughout each school were documented by trained research staff using a direct observation protocol. Information on school direct-drinking water quality was obtained from the routine monitoring program. Data were analyzed for comprehensive assessment of direct-drinking water facilities in the schools. Results: On average, each school had one faucet of direct-water facility per 41 students; 70% of the schools met the requirement for minimum direct-drinking water access, and >90% placed facilities in high-traffic areas. In addition, 83% of the schools selected water facilities with nanofiltration and a hot water system, and most only provided hot water (above 50 degrees Celsius). For school direct-drinking water quality, the concentrations of hardness, chemical oxygen demand (COD), and total dissolved solids (TDS), as well as pH values, were improved significantly, but the total bacteria count was prone to not meeting the requirement for standards in middle and high schools, which could be caused by insufficiency of chlorination in pumping stations or neglecting to clean facilities promptly. Conclusions: Wide usage of school direct-drinking water facilities could help most public schools to meet local policies for minimum student drinking water access in Shanghai, but microbial contamination was the potential threat. Water temperature is the key factor affecting students’ drinking water, providing an optional water temperature for students’ preferences and concerns. National sanitary standards of direct-drinking water quality and relevant additional regulations should be established and implemented in China. Full article

(This article belongs to the Special Issue Design and Management of Water Distribution Systems)

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