Water

19 pages, 8019 KiB

Open AccessArticle

Migration and Transformation of Nitrogen in Clay-Rich Soil Under Shallow Groundwater Depth: In Situ Experiment and Numerical Simulation

by Jinting Huang, Qiu Lv, Zhan Yang, Fang Pu, Ge Song, Jiawei Wang, Zongze Li, Tuo Fang, Tian Huang, Fang Zhang and Fangqiang Sun

Water 2025, 17(3), 427; https://doi.org/10.3390/w17030427 - 3 Feb 2025

Abstract

Excessive use of nitrogen fertilizer in agricultural activities can easily induce nitrogen pollution in groundwater, which may deteriorate groundwater quality. Generally, nitrogen fertilizer passes through the unsaturated zone to groundwater. Therefore, it is of great significance to investigate the migration and transformation of [...] Read more.

Excessive use of nitrogen fertilizer in agricultural activities can easily induce nitrogen pollution in groundwater, which may deteriorate groundwater quality. Generally, nitrogen fertilizer passes through the unsaturated zone to groundwater. Therefore, it is of great significance to investigate the migration and transformation of nitrogen pollutants in unsaturated zones for the prevention and control of groundwater nitrogen pollution. Clay-rich soil is often considered a barrier layer to prevent pollutant leakage because of its lower relative permeability, while its prevention capacity is seldom reported under shallow groundwater table conditions. Motivated by this, an in situ experiment and numerical simulation were conducted to investigate the migration and transformation of nitrogen fertilizer in a clay-unsaturated zone with a shallow groundwater table. Systematic measurements and numerical simulation results revealed that nitrogen can pollute groundwater via the infiltration through clay-rich soil in the in situ experiment site. This finding clarified that the difference in hydraulic head under the shallow groundwater table, rather than soil permeability, is the dominant factor in controlling the downward migration of nitrogen pollutants in the clay-unsaturated zone. More importantly, the nitrogen migration is convection dominant during precipitation in this experiment, indicating nitrogen polluted groundwater much faster in humid climate areas. These findings suggest that nitrogen contaminates groundwater easily under shallow groundwater tables in humid climate areas, even with clay-rich soil texture. Full article

(This article belongs to the Special Issue Water-Related Geoenvironmental Issues, 2nd Edition)

► Show Figures

Figure 1

16 pages, 15870 KiB

Open AccessArticle

Optimizing Irrigation and Nitrogen Application for Greenhouse Tomato Using the DSSAT–CROPGRO–Tomato Model

by Zhijie Shan, Junwei Chen, Xiping Zhang, Zhuanyun Si, Ruochen Yi and Haiyan Fan

Water 2025, 17(3), 426; https://doi.org/10.3390/w17030426 - 3 Feb 2025

Abstract

The aim of this study was to optimize water-saving and high-efficiency irrigation and nitrogen application scheduling for greenhouse tomato cultivation in North China. Using experimental data on water and nitrogen inputs, the DSSAT-GLUE parameter adjustment tool was employed to calibrate the genetic parameters [...] Read more.

The aim of this study was to optimize water-saving and high-efficiency irrigation and nitrogen application scheduling for greenhouse tomato cultivation in North China. Using experimental data on water and nitrogen inputs, the DSSAT-GLUE parameter adjustment tool was employed to calibrate the genetic parameters of the DSSAT–CROPGRO–Tomato model. Simulations were conducted to assess greenhouse tomato growth, water use, and yield under varying water and nitrogen conditions. After calibration, the model showed average relative errors of 3.19% for the phenological stages, 3.33% for plant height, and 4.52% for yield dry weight, meeting accuracy standards. The results from the calibrated model indicated that increasing irrigation or nitrogen levels initially enhanced yield but led to diminishing returns beyond optimal ranges. The maximum tomato yield and water–nitrogen use efficiency were achieved with irrigation quotas between 320 and 340 mm and nitrogen applications between 360 and 400 kg·ha⁻¹. These findings provide a guideline for efficient water and nitrogen management for greenhouse tomatoes under drip irrigation conditions. Full article

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

► Show Figures

Figure 1

16 pages, 1485 KiB

Open AccessArticle

Identification of Critical and Tolerable Fish Habitat Requirements Based on Pre- and Post-Typhoon Data

by Hung-Pin Chiu, Jian-Ping Suen and Pin-Han Chen

Water 2025, 17(3), 425; https://doi.org/10.3390/w17030425 - 3 Feb 2025

Abstract

Catastrophic typhoons with heavy rainfall introduce massive flow and fine sediments into stream channels. In addition, the natural disturbances and engineering practices afterward may strongly alter the fish abundance and their environment. This study compared physical habitat parameters and fish abundance before and [...] Read more.

Catastrophic typhoons with heavy rainfall introduce massive flow and fine sediments into stream channels. In addition, the natural disturbances and engineering practices afterward may strongly alter the fish abundance and their environment. This study compared physical habitat parameters and fish abundance before and after two major typhoons using two sampling period datasets (November 2008–March 2009 and May 2011–March 2012). The study area was in the Cishan Stream, a tributary of the Gaoping River in southern Taiwan. This area experienced two strong typhoons (Morakot and Fanapi) between the two sampling periods, providing an opportunity to compare pre- and post-typhoon conditions. The collected species were Hemimyzon formosanus, Rhinogobius nantaiensis, Onychostoma alticorpus, Candidia barbata, Acrossocheilus paradoxus, and Spinibarbus hollandi. Our results show a decrease in substrate size, fish size, and fish weight after typhoons. The river channel transformed into an unstable condition after the heavy rains, as major habitat types in our sampling stations changed from riffles with coarse substrate to runs with fine substrate. The results of statistical tests indicate the different habitat requirements of three major fish species (H. formosanus, R. nantaiensis, and O. alticorpus) and can indicate whether species’ requirements change between the two sampling periods. Water depth and pebbles were critical habitat requirements for the adults of H. formosanus; water depth, pebbles, and sand were critical habitat requirements for the adults of R. nantaiensis; and flow velocity and standard deviation of flow velocity were critical requirements for the juveniles of O. alticorpus. Understanding habitat requirements can provide useful information for post-disaster restoration and contribute to eco-sensitive river engineering. Full article

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

► Show Figures

Figure 1

22 pages, 1644 KiB

Open AccessArticle

Wave–Structure Interaction Modeling of Transient Flow Around Channel Obstacles and Contractions

by Shahin Oodi, Saeed Gohari, Silvia Di Francesco, Rouzbeh Nazari, Mohammad Reza Nikoo, Payam Heidarian, Ali Eidi and Alireza Khoshkonesh

Water 2025, 17(3), 424; https://doi.org/10.3390/w17030424 - 3 Feb 2025

Viewed by 109

Abstract

This study investigated the effects of downstream channel obstacles and the lateral transition distance to the dam on dam-break wave evolution as a wave–structure interaction problem. Numerical simulations were conducted using three-dimensional Navier–Stokes equations and solved using the finite volume method. The model [...] Read more.

This study investigated the effects of downstream channel obstacles and the lateral transition distance to the dam on dam-break wave evolution as a wave–structure interaction problem. Numerical simulations were conducted using three-dimensional Navier–Stokes equations and solved using the finite volume method. The model accurately predicted interactions between dam-break waves and downstream structures. The numerical results showed that turbulence intensity increased where the cross-section significantly changed in the downstream channel. Accordingly, transcritical flow and lateral transitions were developed around the dam site. Additionally, reducing the distance of the obstacle to the dam resulted in a significant decrease in wave height and kinetic energy. The transient flow velocity direction changed around the structures, and pressure fluctuations were pronounced. Moreover, the entrainment of air bubbles and the vortex shedding were observed due to the interaction of the wave and downstream structures. The peak discharge in the downstream channel was reduced by increasing the distance of obstacles to the dam. The model successfully captured the flow disturbance, wave reflectance from the sidewalls, and formation of hydraulic jumps. The validation of the model with experimental data in the literature showed that the model performed well in predicting the wave dynamic characteristics around the downstream structures. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

25 pages, 8378 KiB

Open AccessArticle

Enhancing the Operating Efficiency of Mixed-Flow Pumps Through Adjustable Guide Vanes

by Chenhan Su, Zhe Zhang, Di Zhu and Ran Tao

Water 2025, 17(3), 423; https://doi.org/10.3390/w17030423 - 3 Feb 2025

Viewed by 150

Abstract

The guide vane mixed-flow pump is a crucial component in medium-to-low-head pumping stations. The guide vanes are mostly fixed in traditional designs. The efficiency of these pumps under off-design operating conditions tends to be low, leading to higher energy consumption. This study explores [...] Read more.

The guide vane mixed-flow pump is a crucial component in medium-to-low-head pumping stations. The guide vanes are mostly fixed in traditional designs. The efficiency of these pumps under off-design operating conditions tends to be low, leading to higher energy consumption. This study explores the design of an adjustable guide vane for the conventional guide vane of a mixed-flow pump at a certain pumping station. Through numerical simulations and two sets of three-factor, five-level orthogonal experiments, we investigate the impact of flow rate, guide vane angle, and impeller angle on efficiency. Through numerical simulation, we identify the optimal relationships between an impeller angle of ±2° and 0° and guide vane angles of ±6°, ±3°, and 0°, focusing on the entropy production rate (EPR) as a key performance metric. The results demonstrate that adjustable guide vanes significantly improve the performance of mixed-flow pumps under off-design conditions. Efficiency increases by up to 17.71% at high flow rates, and by up to 5.48% at low flow rates. Energy consumption is notably reduced. As the flow rate and impeller blade angle vary, the adjustable guide vane rotates to match with the impeller, enhancing flow adaptation, expanding the high-efficiency operating range, and reducing overall energy consumption. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

15 pages, 12466 KiB

Open AccessArticle

Development of a Block-Scale Spatial Flood Vulnerability Index—Case Study: Morelia, Mexico

by Claudia Ximena Roblero-Escobar, Jaime Madrigal, Sonia Tatiana Sánchez-Quispe, Julio César Orantes-Avalos and Liliana García-Romero

Water 2025, 17(3), 422; https://doi.org/10.3390/w17030422 - 3 Feb 2025

Viewed by 159

Abstract

The study of urban floods is increasingly crucial due to their growing frequency and impact on densely populated areas, often characterized by inadequate drainage and located in flood-prone zones. The consequences extend beyond physical damage, significantly affecting economies and livelihoods, necessitating substantial economic [...] Read more.

The study of urban floods is increasingly crucial due to their growing frequency and impact on densely populated areas, often characterized by inadequate drainage and located in flood-prone zones. The consequences extend beyond physical damage, significantly affecting economies and livelihoods, necessitating substantial economic resources for recovery and infrastructure rebuilding. Urban planning now must integrate flood risk management, emphasizing not only infrastructural resilience but also comprehensive policies that address environmental and social vulnerabilities to better prepare and protect urban environments against future flood risks. This study addresses the critical issue of urban flood vulnerability through a focused analysis of Morelia, a city known for its susceptibility to flooding due to its geographical and hydrological characteristics and accelerated urban growth. Employing a multifaceted approach that integrates hydrological, socio-economic, and land use data within a Geographic Information Systems (GIS) framework, the research develops a Spatial Flood Vulnerability Index (SFVI). This index is meticulously applied at the urban block level, offering a precise mapping of flood risks across the city. By correlating the SFVI results with historical flood data, the study identifies the most vulnerable areas in Morelia, which are primarily impacted due to their proximity to water bodies, economic density, and infrastructural settings. The methodology not only highlights immediate flood risks but also aids in strategic urban planning to enhance resilience against future flooding events. This paper contributes a novel approach to flood risk assessment, providing a replicable model for similarly affected cities worldwide, aiming to balance structural measures with strategic planning tailored to local needs. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

► Show Figures

Figure 1

4 pages, 131 KiB

Open AccessEditorial

Advances in Aquifer Systems Analysis: Flows, Interactions, Quality Status, and Remediation

by Andrea Zanini and Fulvio Celico

Water 2025, 17(3), 421; https://doi.org/10.3390/w17030421 - 3 Feb 2025

Viewed by 195

Abstract

The impact of human activities and climate change on water systems is becoming severe [...] Full article

(This article belongs to the Special Issue Advances in Aquifer Systems Analysis: Flows, Interactions, Quality Status, and Remediation)

13 pages, 2519 KiB

Open AccessArticle

Impacts of Changing Temperatures on the Water Budget in the Great Salt Lake Basin

by Grace Affram, Jihad Othman, Reza Morovati, Saddy Pineda Castellanos, Sajad Khoshnoodmotlagh, Diana Dunn, Braedon Dority, Katherine Osorio Diaz, Cody Ratterman and Wei Zhang

Water 2025, 17(3), 420; https://doi.org/10.3390/w17030420 - 2 Feb 2025

Viewed by 480

Abstract

Quantifying the water budget in the Great Salt Lake (GSL) basin is a nontrivial task, especially under a changing climate that contributes to increasing temperatures and a shift towards more rainfall and less snowfall. This study examines the potential impacts of temperature thresholds [...] Read more.

Quantifying the water budget in the Great Salt Lake (GSL) basin is a nontrivial task, especially under a changing climate that contributes to increasing temperatures and a shift towards more rainfall and less snowfall. This study examines the potential impacts of temperature thresholds on the water budget in the GSL, emphasizing the influence on snowmelt, evapotranspiration (ET), and runoff under varying climate warming scenarios. Current hydrological models such as the Variable Infiltration Capacity (VIC) model use a universal temperature threshold to partition snowfall and rainfall across different regions. Previous studies have argued that there is a wide range of thresholds for partitioning rainfall and snowfall across the globe. However, there is a clear knowledge gap in quantifying water budget components in the Great Salt Lake (GSL) basin corresponding to varying temperature thresholds for separating rainfall and snowfall under the present and future climates. To address this gap, the study applied temperature thresholds derived from observation-based data available from National Center for Environmental Prediction (NCEP) to the VIC model. We also performed a suite of hydrological experiments to quantify the water budget of the Great Salt Lake basin by perturbing temperature thresholds and climate forcing. The results indicate that higher temperature thresholds contribute to earlier snowmelt, reduced snowpack, and lower peak runoff values in the early spring that are likely due to increased ET before peak runoff periods. The results show that the GSL undergoes higher snow water equivalent (SWE) values during cold seasons due to snow accumulation and lower values during warm seasons as increased temperatures intensify ET. Projected climate warming may result in further reductions in SWE (~71%), increased atmospheric water demand, and significant impacts on water availability (i.e., runoff reduced by ~20%) in the GSL basin. These findings underscore the potential challenges that rising temperatures pose to regional water availability. Full article

(This article belongs to the Special Issue Global Perspective on Hydrology and Water Resources Management in Complex Urban Areas)

► Show Figures

Figure 1

23 pages, 4459 KiB

Open AccessArticle

Assessment of the Potential of Small Beads Reservoirs to Mitigate Climate Change Impacts in Urban Areas

by Wanda Jarosz, Witold Mandrysz, Barbara Kalinowska-Wójcik, Jakub Grudniewski, Natalia Janczewska, Edyta Sierka, Damian Absalon, Łukasz Pieron, Marcin Lipowczan, Anna Piekarska-Stachowiak, Magdalena Matysik, Dawid Depta, Weronika Walkowiak, Magdalena Biela and Andrzej Woźnica

Water 2025, 17(3), 419; https://doi.org/10.3390/w17030419 - 2 Feb 2025

Viewed by 499

Abstract

This study examines historical water management practices as a means of addressing climate change, focusing on the Tyski Stream catchment in Upper Silesia, Poland, a region marked by extensive urbanization and industrial evolution. It investigates the effectiveness of historical hydrotechnical systems, such as [...] Read more.

This study examines historical water management practices as a means of addressing climate change, focusing on the Tyski Stream catchment in Upper Silesia, Poland, a region marked by extensive urbanization and industrial evolution. It investigates the effectiveness of historical hydrotechnical systems, such as bead-like ponds from the 15th to 18th centuries, in enhancing water retention, reducing flood risks, and supporting ecosystem services. In a critical period, over 54 years (1827–1881), the number of reservoirs decreased from 142 to 31 (the area of ponds decreased from 161 to 32 ha). Throughout the entire period, between 1748 and 2017, the surface area of the analyzed reservoirs decreased from 163 ha to 16.8 ha. This was related to progressive industrialization, urban sprawl, and changes in legal frameworks, such as land ownership laws, leading to ecosystem degradation, loss of biodiversity, and altered hydrological processes. The research emphasizes the potential of reviving historical water management systems on natural processes to mitigate the impacts of climate change. By analyzing historical cartographic resources, this study assesses the feasibility of reconstructing lake systems in areas with similar topographic and hydrological features. It also stresses the necessity of community engagement and securing widespread social and political support to ensure public acceptance and the success of renaturation initiatives. The findings indicate that restoring these systems can offer diverse benefits, including improved water management, enhanced biodiversity, and greater urban resilience, while addressing the socio-political complexities of implementing large-scale environmental restoration projects. The aim of this study is to utilize archival materials for engineering solutions to prevent flooding and enhance water retention. Full article

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

► Show Figures

Figure 1

17 pages, 6960 KiB

Open AccessArticle

Estimation of Rain Garden Field Hydraulic Conductivity Based on Spot Infiltration Tests

by Andrea Welker, James Press, Kristin Sample-Lord and Virginia Smith

Water 2025, 17(3), 418; https://doi.org/10.3390/w17030418 - 2 Feb 2025

Viewed by 322

Abstract

Rain gardens are increasingly being used to control stormwater. Infiltration is a key component of volume control. Thus, determining the infiltration rate or field saturated hydraulic conductivity (K_sat) of rain gardens is critical to their continued successful operation. Designers and [...] Read more.

Rain gardens are increasingly being used to control stormwater. Infiltration is a key component of volume control. Thus, determining the infiltration rate or field saturated hydraulic conductivity (K_sat) of rain gardens is critical to their continued successful operation. Designers and inspectors of rain gardens need to rapidly and efficiently determine the field K_sat. Prior research has found that single-ring infiltrometers (Princeton Hydro, Trenton, NJ, USA) can reliably be used to determine the infiltration rates of soils. The question often posed by designers and inspectors is “how many spot-infiltration tests are needed to sufficiently characterize the infiltration capacity of a rain garden?” Five rain gardens, varying in size from 62 to 429 m², were analyzed for this study. Three different spot infiltration methods were used: single-ring (Princeton Hydro, Trenton, NJ, USA) (least sophisticated and expensive), modified Philip–Dunne (Villanova University, Villanova, PA, USA), and SATURO (METER Group, Pullman, WA, USA) (most sophisticated and expensive). These rain gardens also had been instrumented to capture the recession rates during either natural or artificial ponding events. The linear portion of the recession curve obtained during ponding events was used to provide the rain-garden-wide K_sat. It was found that the geometric mean of six spot infiltration tests provided a reliable K_sat value similar to that found by the recession rate, which best represents the value of K_sat for the entire rain garden. This indicates that an inspector can reliably determine the infiltration capacity of a rain garden in less than a day. Full article

(This article belongs to the Section Urban Water Management)

► Show Figures

Figure 1

15 pages, 3429 KiB

Open AccessArticle

Hydrological Dynamics and Climate Variability in the Sava River Basin: Streamflow Reconstructions Using Tree-Ring-Based Paleo Proxies

by Abel Andrés Ramírez Molina, Igor Leščešen, Glenn Tootle, Jiaqi Gong and Milan Josić

Water 2025, 17(3), 417; https://doi.org/10.3390/w17030417 - 2 Feb 2025

Viewed by 454

Abstract

This study reconstructs historical streamflow in the Sava River Basin (SRB), focusing on hydrological variability over extended timescales. Using a combination of Machine Learning (ML) and Deep Learning (DL) models, streamflow patterns were reconstructed from self-calibrated Palmer Drought Severity Index (scPDSI) proxies. The [...] Read more.

This study reconstructs historical streamflow in the Sava River Basin (SRB), focusing on hydrological variability over extended timescales. Using a combination of Machine Learning (ML) and Deep Learning (DL) models, streamflow patterns were reconstructed from self-calibrated Palmer Drought Severity Index (scPDSI) proxies. The analysis included nine ML models and two DL architectures, with a post-prediction bias correction applied uniformly using the RQUANT method. Results indicate that ensemble methods, such as Random Forest and Gradient Boosted Tree, along with a six-layer DL model, effectively captured streamflow dynamics. Bias correction improved predictive consistency, particularly for models exhibiting greater initial variability, aligning predictions more closely with observed data. The findings reveal that the 2000–2022 period ranks as the lowest 23-year flow interval in the observed record and one of the driest over the past ~500 years, offering historical context for prolonged low-flow events in the region. This study demonstrates the value of integrating advanced computational methods with bias correction techniques to extend hydrological records and enhance the reliability of reconstructions. By addressing data limitations, this approach provides a foundation for supporting evidence-based water resource management in Southeastern Europe under changing climatic conditions. Full article

(This article belongs to the Section Hydrology)

► Show Figures

Figure 1

17 pages, 4130 KiB

Open AccessReview

The Potential Role of Africa in Green Hydrogen Production: A Short-Term Roadmap to Protect the World’s Future from Climate Crisis

by Moustafa Gamal Snousy, Ashraf R. Abouelmagd, Yasser M. Moustafa, Dimitra E. Gamvroula, Dimitrios E. Alexakis and Esam Ismail

Water 2025, 17(3), 416; https://doi.org/10.3390/w17030416 - 2 Feb 2025

Viewed by 477

Abstract

The global need for energy has risen sharply recently. A global shift to clean energy is urgently needed to avoid catastrophic climate impacts. Hydrogen (H₂) has emerged as a potential alternative energy source with near-net-zero emissions. In the African continent, for [...] Read more.

The global need for energy has risen sharply recently. A global shift to clean energy is urgently needed to avoid catastrophic climate impacts. Hydrogen (H₂) has emerged as a potential alternative energy source with near-net-zero emissions. In the African continent, for sustainable access to clean energy and the transition away from fossil fuels, this paper presents a new approach through which waste energy can produce green hydrogen from biomass. Bio-based hydrogen employing organic waste and biomass is recommended using biological (anaerobic digestion and fermentation) processes for scalable, cheaper, and low-carbon hydrogen. By reviewing all methods for producing green hydrogen, dark fermentation can be applied in developed and developing countries without putting pressure on natural resources such as freshwater and rare metals, the primary feedstocks used in producing green hydrogen by electrolysis. It can be expanded to produce medium- and long-term green hydrogen without relying heavily on energy sources or building expensive infrastructure. Implementing the dark fermentation process can support poor communities in producing green hydrogen as an energy source regardless of political and tribal conflicts, unlike other methods that require political stability. In addition, this approach does not require the approval of new legislation. Such processes can ensure the minimization of waste and greenhouse gases. To achieve cost reduction in hydrogen production by 2030, governments should develop a strategy to expand the use of dark fermentation reactors and utilize hot water from various industrial processes (waste energy recovery from hot wastewater). Full article

(This article belongs to the Special Issue Advances in Water Conservancy and Hydropower Engineering: Modelling, Performances, Optimization Application and Environmental Effects)

► Show Figures

Figure 1

14 pages, 2759 KiB

Open AccessArticle

Optimization of Scale Inhibitor Addition Scheme and Control of Phosphorus Content in External Cooling System of Synchronous Condenser

by Xiantao Gu, Yuquan Wu, Yunqing Xu, Hongwei Zhao, Lin Yang, Xiaochun Chen, Peipei Fan, Junjie Zhang, Zhikui Liu, Tao Zhu, Yuxiang Gao and Haosheng Dong

Water 2025, 17(3), 415; https://doi.org/10.3390/w17030415 - 2 Feb 2025

Viewed by 221

Abstract

Scaling is one of the common problems in circulating cooling water systems, which can significantly affect the cooling efficiency of equipment in severe cases. At present, the problem of scaling is usually controlled by adding water treatment agents. However, taking the external cooling [...] Read more.

Scaling is one of the common problems in circulating cooling water systems, which can significantly affect the cooling efficiency of equipment in severe cases. At present, the problem of scaling is usually controlled by adding water treatment agents. However, taking the external cooling system of the synchronous condenser in an ultra-high-voltage converter station as an example, due to the lack of scientific understanding of scale inhibitors, there is often a problem of excessive dosing, resulting in unsatisfactory scale inhibition effects and difficulties in wastewater treatment and discharge. In addition, the extensive use of phosphorus-containing agents has led to the enrichment of phosphorus elements in water bodies. Therefore, the optimal amount of AS-582 scale inhibitor used in the converter station with the best scale inhibition effect was determined through static calcium carbonate deposition experiments, with the scale inhibition rate of 91.4% at 90 mg/L. And the scale inhibition mechanism was explored, where the lattice distortion mechanism and threshold effect play important roles. The AS-582 scale inhibitor was mixed with two green scale inhibitors, PASP and PESA, to obtain a phosphorus reduction formula that combined excellent scale inhibition performance and low phosphorus content. When using the optimal composite scale inhibitor of n(AS-582):n(PASP):n(PESA) = 4:1:1, the scale inhibition rate is 91.8% and the phosphorus content is reduced by one-third. The effectiveness of the formula was tested using dynamic circulating water experimental equipment under practical application conditions, proving its practical value. Full article

(This article belongs to the Special Issue Green and Low Carbon Development of Water Treatment Technology, 2nd Edition)

► Show Figures

Figure 1

21 pages, 33528 KiB

Open AccessArticle

Simulating the Failure Mechanism of High-Slope Angles Under Rainfall-Mining Coupling Using MatDEM

by Qihang Li, Yunmin Wang, Di Hou, Song Jiang, Bin Gong and Xiaoshuang Li

Water 2025, 17(3), 414; https://doi.org/10.3390/w17030414 - 2 Feb 2025

Viewed by 258

Abstract

The safety production of gold, silver, copper, and other important metals is seriously threatened in the process of mining from open-pit to underground due to various factors such as infiltration caused by rainfall and unloading during mining. Furthermore, the current situation of open-pit [...] Read more.

The safety production of gold, silver, copper, and other important metals is seriously threatened in the process of mining from open-pit to underground due to various factors such as infiltration caused by rainfall and unloading during mining. Furthermore, the current situation of open-pit mining in an increasing number of mines presents a high and steep terrain, which poses significant security risks. Accordingly, it is of great practical significance to investigate the failure mechanism of high-slope angles to ensure the long-term safe mining of mines, considering factors such as rainfall infiltration and excavation unloading. In this study, the slope failure of high-slope angles (45°, 55°, and 65°) under rainfall-mining coupling was analyzed using the discrete element MatDEM numerical simulation software. Herein, the stress distribution, failure characteristics, and energy conversion of the model were simulated under different slope angles to analyze the failure mechanism at each stage. The simulation results show that the damage scale is smallest at 55° and largest at 65°. This indicates that setting the slope angle to 55° can reduce the risk of slope instability. Moreover, the reduction of elastic potential energy during the mine room mining stage is similar to that of mechanical energy. During the pillar mining stage, stress is concentrated in each goaf, resulting in a greater reduction in mechanical energy compared to elastic potential energy. Finally, after the completion of the continuous pillar mining stage, stress becomes concentrated in the failure area, and the effect of the slope angle on mechanical energy reduction becomes evident after the complete collapse of the model. Full article

(This article belongs to the Special Issue Slope Stability Analyses and Risk Assessment for Rainfall-Induced Landslides)

► Show Figures

Figure 1

20 pages, 4238 KiB

Open AccessArticle

Is Industrial-Scale Wastewater Treatment Possible with a Commercially Available Atmospheric Pressure Plasma System? A Practical Study Using the Example of a Car Wash

by Michał Szulc, Carmen Kirner, Jörg Götz and Jochen Schein

Water 2025, 17(3), 413; https://doi.org/10.3390/w17030413 - 2 Feb 2025

Viewed by 238

Abstract

The topic of water reuse is becoming increasingly important. It might be possible to use the well-known antibacterial effect of atmospheric pressure plasma due to its special mixture of reactive species, UV, and electromagnetic fields in a scaled-up, industrially interesting area to remove [...] Read more.

The topic of water reuse is becoming increasingly important. It might be possible to use the well-known antibacterial effect of atmospheric pressure plasma due to its special mixture of reactive species, UV, and electromagnetic fields in a scaled-up, industrially interesting area to remove bacteria from wastewater, and thus, make it usable again. To review this question, water volumes of

5 L

and of different qualities (turbidity and different degrees of hardness) were treated with a commercially available plasma system. The change in water-specific values such as pH, EC, ORP, nitrate, and nitrite content was determined. To test the antibacterial effect, both direct and indirect treatment of the test germ Pseudomonas aeruginosa was conducted. In the first case, the inoculated water samples were plasma-treated, while in the second case, the water samples were treated before inoculation with the germ. The viable bacteria were counted via the spread plate method. The best reduction rate of at least 6 log levels was achieved when inoculated deionized water samples were treated directly with plasma. A significant reduction in viability was also observed in directly treated clear tap water samples, whereby the different degrees of hardness did not influence the effectiveness of the plasma. The bacterial load remained almost unchanged when reused water samples from a car wash were treated. Based on the results, a possible application in a car wash was discussed including a cost estimation and possible limitations. Full article

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

► Show Figures

Figure 1

16 pages, 6142 KiB

Open AccessArticle

Migration and Transformation of Greenhouse Gases in Constructed Wetlands: A Bibliometric Analysis and Trend Forecast

by Ruiyao Qi, Jiahao Dong, Yan Kang, Huijun Xie, Haiming Wu, Zhen Hu and Zizhang Guo

Water 2025, 17(3), 412; https://doi.org/10.3390/w17030412 - 2 Feb 2025

Viewed by 221

Abstract

Constructed wetlands (CWs), serving as an advanced wastewater treatment system, play a vital role in both the emission and sequestration of diverse GHGs. However, there are few papers reviewing and analyzing developments in the field. In this study, bibliometrics were used as an [...] Read more.

Constructed wetlands (CWs), serving as an advanced wastewater treatment system, play a vital role in both the emission and sequestration of diverse GHGs. However, there are few papers reviewing and analyzing developments in the field. In this study, bibliometrics were used as an essential tool for identifying and establishing connections among key elements within a discipline, as well as for analyzing the research status and developmental trends of the research fields. CiteSpace 6.3.1 was utilized to conduct an analysis of the references from the Web of Science Core Collection pertaining to GHG emissions from CWs over the period from 1993 to 2023. This study showed the following conclusions. (1) Organic nitrogen conversion produces N₂O, which is eventually transformed into N₂ and released from CWs. Anammox represents an attractive route for nitrogen removal. (2) The CO₂ is the final product of the oxidation of organic matter in the influent of CWs and can be fixed by plant photosynthesis. Anaerobic fermentation and CO₂ reduction produce CH₄. The two are emitted through aerenchyma transport, bubble diffusion, and other forms. (3) In the past 30 years, the number of publications and citation frequency shows an increasing trend. China and the United States published more papers. The top ten authors contributed to 20.607% of the total 1019, and the cooperation between different author groups needs to be strengthened. (4) The emerging burst keywords following 2020 are “microbial fuel cell” and “microbial community”, which highlights the current hotspots in research related to GHG emissions from CWs. (5) There is still a lack of long-term and applied discussion on the role of CWs in promoting GHG emission reduction. The relevant reaction conditions and mechanisms need to be explored and the possible research directions can be genetic regulation and information technology. Full article

(This article belongs to the Special Issue Constructed Wetlands as a Sustainable Technology for Wastewater Treatment: Current Trends and Future Potential)

► Show Figures

Figure 1

22 pages, 1515 KiB

Open AccessArticle

Cellular Responses of Astrangia poculata (Ellis and Solander, 1786) and Its Symbiont to Experimental Heat Stress

by Tyler E. Harman, Daniel Barshis, Briana Hauff Salas and Kevin B. Strychar

Water 2025, 17(3), 411; https://doi.org/10.3390/w17030411 - 1 Feb 2025

Viewed by 427

Abstract

Climate change has had devastating effects on tropical coral reefs; however, much less is known regarding how heat stress affects temperate coral. This research focuses on Astrangia poculata (Ellis and Solander, 1786) collected from Narragansett Bay, RI, during the summer and winter seasons [...] Read more.

Climate change has had devastating effects on tropical coral reefs; however, much less is known regarding how heat stress affects temperate coral. This research focuses on Astrangia poculata (Ellis and Solander, 1786) collected from Narragansett Bay, RI, during the summer and winter seasons and understanding the effect of experimental thermal extremes (i.e., 26 °C) on seasonally different populations. Photosynthetic efficiency (Fv/Fm), symbiont density (via an inverse relationship with pixel intensity), and oxidative stress via reactive oxygen species (ROS) concentrations were measured on symbiotic and aposymbiotic A. poculata. Higher Fv/Fm rates were observed in summer- vs. winter-collected corals (p ≤ 0.05). Lower symbiont density within symbiotic and aposymbiotic A. poculata were observed at elevated temperatures, and higher intensities as well as symbiotic coral were observed in winter compared to the summer collections (p ≤ 0.05). No differences in ROS were observed in host tissue cells, suggesting that ROS produced in the algal symbionts was not translocated into host tissues. Overall, higher ROS concentrations were observed in summer- vs. winter-collected corals (p ≤ 0.05) in both symbiotic states. ROS concentrations were higher in symbiotic compared to aposymbitoic colonies (p ≤ 0.05), albeit no differences were observed between temperature treatments, suggesting that antioxidants mitigate the deleterious effects of ROS on host tissues. Full article

25 pages, 5948 KiB

Open AccessArticle

Spatiotemporal Variability of Groundwater Quality for Irrigation: A Case Study in Mimoso Alluvial Valley, Semiarid Region of Brazil

by Thayná A. B. Almeida, Abelardo A. A. Montenegro, João L. M. P. de Lima, Carolyne W. L. A. Farias, Ailton A. Carvalho and Anderson L. R. de Paiva

Water 2025, 17(3), 410; https://doi.org/10.3390/w17030410 - 1 Feb 2025

Viewed by 430

Abstract

Alluvial aquifers are vital for agricultural communities in semiarid regions, where groundwater quality is often constrained by seasonal and spatial salinity variations. This study employed geostatistical methods to analyze the spatial and temporal variability of electrical conductivity (EC) and the sodium adsorption ratio [...] Read more.

Alluvial aquifers are vital for agricultural communities in semiarid regions, where groundwater quality is often constrained by seasonal and spatial salinity variations. This study employed geostatistical methods to analyze the spatial and temporal variability of electrical conductivity (EC) and the sodium adsorption ratio (SAR) and elaborate an indicative quality map in the Mimoso Alluvial Aquifer, Pernambuco, Brazil. Groundwater samples were collected and analyzed for cations, total hardness (TH), and the percentage of sodium (PS). Moreover, the relation between EC and the SAR was used to determine the groundwater quality for irrigation. Cation concentrations followed the order Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. EC and the SAR exhibited medium to high variability, with spatial dependence ranging from moderate to strong, and presented a strong cross-spatial dependence. Results showed that sequential Gaussian simulation (SGS) provided a more reliable groundwater classification for agricultural purposes compared to kriging methods, enabling a more rigorous evaluation. Based on the strong geostatistical cross correlation between EC and RAS, a novel water quality index was proposed, properly identifying regions with lower groundwater quality. The resulting spatial indicator maps classified groundwater as suitable (64.7%), restricted use (2.08%) and unsuitable (2.38%) for irrigation. The groundwater quality maps indicated that groundwater was mostly suitable for agriculture, except in silty areas, also corresponding to regions with low hydraulic conductivity at the saturated zone. Soil texture, rainfall, and water extraction significantly influenced spatial and temporal patterns of groundwater quality. Such correlations allow a better understanding of the groundwater quality in alluvial valleys, being highly relevant for water resources management in semiarid areas. Full article

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

► Show Figures

Figure 1

17 pages, 5159 KiB

Open AccessArticle

The Role of the Heterogeneity of Volcanic Aquifer Properties in Assessing Sustainable Well Yield: Study Cases from Latium (Central Italy)

by Chiara Sbarbati, Matteo Paoletti and Vincenzo Piscopo

Water 2025, 17(3), 409; https://doi.org/10.3390/w17030409 - 1 Feb 2025

Viewed by 282

Abstract

Groundwater resources from the volcanic aquifers of northern Latium (central Italy) are widely used to supply local water needs and are mainly captured through wells. Nevertheless, despite the detailed hydrogeological knowledge of these aquifers, not enough information is available on the long-term pumping [...] Read more.

Groundwater resources from the volcanic aquifers of northern Latium (central Italy) are widely used to supply local water needs and are mainly captured through wells. Nevertheless, despite the detailed hydrogeological knowledge of these aquifers, not enough information is available on the long-term pumping yield necessary to define the sustainable yield of a well. In this study, data from about 230 pumping tests (mainly step-drawdown and a few constant-flow-rate tests) performed in the volcanic aquifers of the Latium region were analyzed. Specifically, the aquifer formations intercepted by the wells are the fall and flow pyroclastic deposits of the Vico, Vulsini, and Sabatini volcanic districts; lava from the Vico, Cimino, and Vulsini volcanic districts; and Ignimbrite Cimina, one of the main pyroclastic products of the Cimino eruptions. These aquifers were grouped and analyzed by considering the type of permeability, hydrostratigraphic succession, and frequency and thickness of the aquifer horizons intercepted by wells. The results obtained in terms of specific capacity and transmissivity values are comparable among the identified different aquifer formations, showing a good correlation between the two parameters, a strong hydraulic heterogeneity (variability within five orders of magnitude), and variable responses regarding drawdown to pumping. This study highlights that the analysis of drawdown over time at a constant flow is fundamental in heterogeneous hydrogeological environments such as volcanic ones, where the trend in drawdown is often affected by the reduced spatial continuity of the most productive aquifer formations. Knowledge of the trend in drawdown over time, the thickness of the aquifer intercepted by the well, and the operating time of the well is an essential element in defining the sustainable yield of a well. Full article

► Show Figures

Figure 1

24 pages, 2297 KiB

Open AccessArticle

Filling the Gap: Explaining Foreign Participation in China’s Water PPP Projects from a Local Government Perspective

by Dan Li, Zhen Zhang and Zhirong Jerry Zhao

Water 2025, 17(3), 408; https://doi.org/10.3390/w17030408 - 1 Feb 2025

Viewed by 345

Abstract

Foreign capital has dominated over half of the public–private partnership (PPP) projects in developing countries over the past three decades. As such, attracting and regulating foreign participation in water PPP projects presents a critical challenge for both practitioners and scholars. Using a dataset [...] Read more.

Foreign capital has dominated over half of the public–private partnership (PPP) projects in developing countries over the past three decades. As such, attracting and regulating foreign participation in water PPP projects presents a critical challenge for both practitioners and scholars. Using a dataset of 2024 water PPP projects from 1994 to 2021, this study investigates foreign participation and its fall in China’s water PPP projects. Our findings highlight three key points: First, the proportion of projects undertaken by foreign capital decreased from 100% to less than 0.5%, with Chinese domestic capital taking its place. Second, resource dependence on foreign capital and the local government’s need for control lead to four types of foreign participation: financing water plants under user-pays, financing and operating water utilities under government-pays, participating with mainly an O&M role, and nearly no participation. Third, a better balance between efficiency gains and control needs via cooperation with domestic capital by local governments had driven the decline in foreign participation. This study makes two key contributions: (1) it is one of the pioneer studies on systematically tracing the evolution of foreign participation in PPP projects, and (2) it explains the fall of foreign participation from a local government perspective, complementing market-based explanations. Full article

► Show Figures

Figure 1

33 pages, 8519 KiB

Open AccessArticle

Comprehensive Assessment of the Jebel Zaghouan Karst Aquifer (Northeastern Tunisia): Availability, Quality, and Vulnerability, in the Context of Overexploitation and Global Change

by Emna Gargouri-Ellouze, Fairouz Slama, Samiha Kriaa, Ali Benhmid, Jean-Denis Taupin and Rachida Bouhlila

Water 2025, 17(3), 407; https://doi.org/10.3390/w17030407 - 1 Feb 2025

Viewed by 321

Abstract

Karst aquifers in the Mediterranean region are crucial for water supply and agriculture but are increasingly threatened by climate change and overexploitation. The Jebel Zaghouan aquifer, historically significant for supplying Carthage and Tunis, serves as the focus of this study, which aims to [...] Read more.

Karst aquifers in the Mediterranean region are crucial for water supply and agriculture but are increasingly threatened by climate change and overexploitation. The Jebel Zaghouan aquifer, historically significant for supplying Carthage and Tunis, serves as the focus of this study, which aims to evaluate its availability, quality, and vulnerability to ensure its long-term sustainability. To achieve this, various methods were employed, including APLIS and COP for recharge assessment and vulnerability mapping, SPEI and SGI drought indices, and stable and radioactive isotope analysis. The findings revealed severe groundwater depletion, primarily caused by overexploitation linked to urban expansion. Minimal recharge was observed, even during wet periods. APLIS analysis indicated moderate infiltration rates, consistent with prior reservoir models and the MEDKAM map. Isotopic analysis highlighted recharge from the Atlantic and mixed rainfall, while Tritium and Carbon-14 dating showed a mix of ancient and recent water, emphasizing the aquifer’s complex hydrodynamics. COP mapping classified 80% of the area as moderately vulnerable. Monitoring of nitrate levels indicated fluctuations, with peaks during wet years at Sidi Medien Spring, necessitating control measures to safeguard water quality amid agricultural activities. This study provides valuable insights into the aquifer’s dynamics, guiding sustainable management and preservation efforts. Full article

(This article belongs to the Special Issue Recent Advances in Karstic Hydrogeology, 2nd Edition)

► Show Figures

Figure 1

23 pages, 13298 KiB

Open AccessArticle

A Case Study of the Debris Flows Event in the Chalk Cliffs Basin, Colorado, USA: Numerical Simulations Based on a Multi-Phase Flow Model

by Mohammad Wasif Naqvi, Diwakar KC and Liangbo Hu

Water 2025, 17(3), 406; https://doi.org/10.3390/w17030406 - 1 Feb 2025

Viewed by 303

Abstract

Debris flows are among the severe gravity-driven mass phenomena that pose a significant threat to the environment and communities. Recent events and studies in the Chalk Cliffs basin in Colorado suggest that it is very susceptible to debris flow incidents that initiate from [...] Read more.

Debris flows are among the severe gravity-driven mass phenomena that pose a significant threat to the environment and communities. Recent events and studies in the Chalk Cliffs basin in Colorado suggest that it is very susceptible to debris flow incidents that initiate from surface run-off, which involves significant entrainment of material along the hill slope and channel sediments. The entrainment of material along the flow makes these events destructive, with large travel distances s well as high velocity, flow pressure, kinetic energy, etc. This paper presents a case study of a debris flow event on 15 September 2009 based on a multi-phase flow model. The model provides the ability to investigate the effect of fluid and solid phases individually. Three sensitivity analyses are presented investigating the effect of bed roughness on solid and fluid phases separately, and also the effect of the entrainment of bed material. The findings demonstrate that the numerical model effectively replicates the observed field data, with the simulated peak discharge and runout distance closely aligning with the observed measurements. The analysis reveals that lower bed roughness promotes higher flow mobility and longer runout distances, while entrainment significantly influences flow height, velocity, and deposition pattern. Furthermore, the analysis highlights the dominant role of entrainment in debris flow evolution and emphasizes its importance in determining deposition and erosion patterns. These findings provide critical insights into the key processes of debris flows and could contribute to the development of accurate numerical models for debris flow events. Full article

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

► Show Figures

Figure 1

17 pages, 2027 KiB

Open AccessArticle

Comparison of the Effectiveness of Artificial Neural Networks and Elastic Net Regression in Surface Runoff Modeling

by Jacek Dawidowicz and Rafał Buczyński

Water 2025, 17(3), 405; https://doi.org/10.3390/w17030405 - 1 Feb 2025

Viewed by 243

Abstract

This study compares Artificial Neural Networks (ANN) and Elastic Net regression for predicting surface runoff in urban stormwater catchments. Both models were trained on a data set derived from the Stormwater Management Model that included parameters such as imperviousness, flow path width, slope, [...] Read more.

This study compares Artificial Neural Networks (ANN) and Elastic Net regression for predicting surface runoff in urban stormwater catchments. Both models were trained on a data set derived from the Stormwater Management Model that included parameters such as imperviousness, flow path width, slope, Manning coefficients, and depression storage. ANN exhibited greater predictive accuracy and stability, especially when modeling nonlinear hydrologic interactions, while Elastic Net offered faster inference and clearer interpretability, but showed reduced accuracy in low-flow conditions. Validation on real-world data revealed the sensitivity of the models to scenarios not fully represented during training. Despite higher computational demands, the ANN proved more adaptable, while the more resource-efficient Elastic Net remains suitable for time-critical or large-scale applications. These findings provide practical insights for urban water resource management, indicating when each approach can be most effectively used in flood risk assessment and stormwater infrastructure planning. Full article

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

► Show Figures

Figure 1

17 pages, 2942 KiB

Open AccessArticle

Response of Trichoptera and Oligochaeta Communities to Modifications of Mountain River Channels with Low-Head Barriers

by Ewa Szarek-Gwiazda, Elżbieta Dumnicka, Bronisław Szczęsny, Andrzej Kownacki and Dariusz Ciszewski

Water 2025, 17(3), 404; https://doi.org/10.3390/w17030404 - 1 Feb 2025

Viewed by 249

Abstract

The responses of benthic fauna to channel modifications of mountain rivers by low-head barriers are poorly understood. The study aimed (1) to estimate the impact of two different low-head barrier types: concrete sills and block ramps, on Oligochaeta and Trichoptera communities in two [...] Read more.

The responses of benthic fauna to channel modifications of mountain rivers by low-head barriers are poorly understood. The study aimed (1) to estimate the impact of two different low-head barrier types: concrete sills and block ramps, on Oligochaeta and Trichoptera communities in two small Carpathian rivers (Porębianka and Mszanka) in southern Poland, and (2) to determine changes in these communities in the mountain Porębianka River after 50 years by comparing current data with historical data. Both types of channel modifications led to a transformation from lotic to more lentic habitats. The research shows that habitat conditions and induced bed siltation greatly influenced the studied communities. In both rivers, the taxa richness and dominant taxa of Oligochaeta and Trichoptera were similar, alongside similar species compositions of Trichoptera. However, the river with the lower bed siltation rate had a higher Trichoptera density and a greater diversity in their density among habitats. After 50 years, the taxonomic richness of Oligochaeta and Trichoptera remained similar, unlike the considerable shift in their species compositions. Many species typical of mountain rivers have been replaced by species more tolerant to siltation, characteristic of lowland rivers. The family Tubificidae (Oli-gochaeta) and the genus Hydropsyche (Trichoptera) became dominant in both rivers in the early 2020s. Additionally, the functional feeding group (FFG) of Trichoptera changed considerably. Oligochaeta and Trichoptera communities serve as valuable indicators for moni-toring the environmental changes in these ecosystems. Full article

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

► Show Figures

Figure 1

22 pages, 16461 KiB

Open AccessArticle

Water Management Instructions as an Element of Improving the State of the Pakoski Reservoir (Central–Western Poland)

by Bogumił Nowak, Grzegorz Dumieński and Agnieszka Ławniczak-Malińska

Water 2025, 17(3), 403; https://doi.org/10.3390/w17030403 - 1 Feb 2025

Viewed by 293

Abstract

The management of reservoir dams in the context of observed climate changes and changing environmental conditions is becoming an increasingly significant challenge. Changes in the regimes of rivers feeding the reservoirs, sudden floods, long periods of drought, shallowing of reservoirs, water pollution, and [...] Read more.

The management of reservoir dams in the context of observed climate changes and changing environmental conditions is becoming an increasingly significant challenge. Changes in the regimes of rivers feeding the reservoirs, sudden floods, long periods of drought, shallowing of reservoirs, water pollution, and algal blooms create unprecedented threats to the operation of these reservoirs. Among these challenges, the most crucial seems to be the proper management of available water resources, which condition the existence of the reservoir. The location of the reservoir has a significant impact on how water management is conducted. In the case of mountain and upland reservoirs created for flood protection of areas downstream, water management practices differ significantly from those for lowland reservoirs, which primarily serve to retain water for industrial and agricultural needs in the area, with an additional flood protection function. The aim of this study was to assess the factors determining the supply of lowland reservoirs using the example of the Pakoski Reservoir (Central–Western Poland) and to propose actions that would allow more efficient management of water resources in the catchment and reservoir, enabling the preservation of the current morphometric parameters in the face of climate change, adverse environmental phenomena, and increased anthropogenic pressure in the catchment area. This study focused on the Pakoski Reservoir, located in the southern part of the Kuyavian–Pomeranian Voivodeship. It was constructed fifty years ago as a result of damming water in the river systems of the Noteć and Mała Noteć Rivers. For decades, it served its functions, and its management posed no major issues. However, over the past decade, due to environmental changes and human activities in the catchment area, the reservoir has increasingly faced problems with filling. Full article

(This article belongs to the Special Issue Climate Change and Hydrological Processes)

► Show Figures

Figure 1

23 pages, 3668 KiB

Open AccessArticle

Optimization of Selected Parameters in Vertical, Horizontal, and Hybrid Surface Flow Constructed Wetland Systems for Improving the Treatment Efficiency of Textile and Sewage Effluents

by Faisal Javeed, Firdaus-e-Bareen, Muhammad Shafiq, Aisha Nazir and Miklas Scholz

Water 2025, 17(3), 402; https://doi.org/10.3390/w17030402 - 1 Feb 2025

Viewed by 272

Abstract

Constructed wetland systems (CWSs) can offer cost-effective wastewater treatment in developing countries like Pakistan. This study focused on optimizing design and operational parameters of CWSs in horizontal surface flow (HSF), vertical surface flow (VSF), and hybrid mesocosms for treating sewage and textile effluents [...] Read more.

Constructed wetland systems (CWSs) can offer cost-effective wastewater treatment in developing countries like Pakistan. This study focused on optimizing design and operational parameters of CWSs in horizontal surface flow (HSF), vertical surface flow (VSF), and hybrid mesocosms for treating sewage and textile effluents using local hydrophytes: Lemna minor, Typha latifolia, and Eichhornia crassipes. Pollutants and heavy metals (Cd, Cr, Cu, Pb, Ni, and Zn) were removed under different flow configurations, bedding materials, hydrophyte species, and hydraulic retention times (HRT) to optimize the overall contaminant removal efficiency (RE). Key findings indicated that the hybrid CWS achieved a maximum RE of 63.62% for total suspended solids (TSS) and 57.9% for biochemical oxygen demand (BOD) at an HRT of 3 days, with efficiencies declining at longer retention times. Additionally, the hybrid system showed maximum metal removal, with Cd and Cr RE reaching 75.2% and 70.5%, respectively. The study also highlighted the critical role of hydrophyte species and HRT in optimizing RE. Furthermore, the choice of hydrophyte species significantly influenced pollutant removal, with treatment cells containing mixed hydrophytes achieving the highest removal efficiencies (63.62%), followed by Eichhornia crassipes with high Cd (643.33 mgkg⁻¹) and Cr (1103.72 mgkg⁻¹) uptake. A lower HRT of 3 days resulted in the highest overall removal efficiency of 57.5%, which decreased with longer HRTs (from 6 to 9 days). Optimizing design and operational parameters is crucial for maximizing CWS treatment potential. Full article

(This article belongs to the Special Issue Constructed Wetland Systems for Wastewater Treatment and Water Remediation)

► Show Figures

Figure 1

28 pages, 1446 KiB

Open AccessArticle

Efficient Naval Surveillance: Addressing Label Noise with Rockafellian Risk Minimization for Water Security

by Gabriel Custódio Rangel, Victor Benicio Ardilha da Silva Alves, Igor Pinheiro de Araújo Costa, Miguel Ângelo Lellis Moreira, Arthur Pinheiro de Araújo Costa, Marcos dos Santos and Eric Charles Eckstrand

Water 2025, 17(3), 401; https://doi.org/10.3390/w17030401 - 31 Jan 2025

Viewed by 338

Abstract

This study proposes developing a resilient machine learning algorithm based on neural networks to classify naval images used in surveillance, search, and detection operations in vast coastal and marine environments. Coastal areas critical for water resource management often face challenges such as illegal [...] Read more.

This study proposes developing a resilient machine learning algorithm based on neural networks to classify naval images used in surveillance, search, and detection operations in vast coastal and marine environments. Coastal areas critical for water resource management often face challenges such as illegal fishing, trafficking, piracy, and other illicit activities that require robust monitoring systems powered by computer vision. However, real-world datasets in such environments can be compromised by label noise due to random inaccuracies or deliberate adversarial attacks, leading to decreased accuracy in machine learning models. Our innovative approach employs Rockafellian Risk Minimization (RRM) to mitigate the impact of label noise contamination, crucial to maintaining data integrity in water-related security and governance operations. Unlike existing methodologies that rely on extensively cleaned datasets, our two-step process adjusts neural network weights and manipulates nominal probabilities of data points to isolate potential data corruption effectively. This technique reduces dependence on meticulous data cleaning, thereby increasing data processing efficiency in water resources and coastal management. To validate the effectiveness and reliability of the proposed model, we apply RRM in various parameter settings to datasets specific to naval environments and evaluate its classification accuracy against traditional methods. By leveraging the proposed model, we aim to reinforce the robustness of ship detection models, ultimately contributing to developing more reliable automated maritime surveillance systems. Such systems are essential for strengthening governance, security, and water management and curbing illegal activities at sea. Full article

(This article belongs to the Special Issue Coastal and Marine Governance and Protection)

20 pages, 4545 KiB

Open AccessArticle

An Investigation of the Thickness of Huhenuoer Lake Ice and Its Potential as a Temporary Ice Runway

by Ying Wang, Qiuming Zhao, Bo Zhang, Qingjiang Wang, Peng Lu, Qingkai Wang, Xinghua Bao and Jiahuan He

Water 2025, 17(3), 400; https://doi.org/10.3390/w17030400 - 31 Jan 2025

Viewed by 317

Abstract

The study of ice runways has significant practical importance. Regarding inland lake ice, while little of the practicality of ice runways during the ice formation period was explored in the published articles, the analysis of the time period and suitable locations may be [...] Read more.

The study of ice runways has significant practical importance. Regarding inland lake ice, while little of the practicality of ice runways during the ice formation period was explored in the published articles, the analysis of the time period and suitable locations may be used. This study focused on Huhenuoer Lake, located in Chen Barag Banner in northeastern China. The time-dependent law of ice growth in this lake has been investigated over a study period from 2023 to 2024. Utilizing the drilling approach, the ice thickness, recorded at each site on 29 February 2024, has surpassed 100 cm. On 14 March 2024, the recorded ice thickness at site #2 reached a record high of 139 cm. Second, to assess the project’s ease of use and safety, we used the Stefan equation to model the lake’s ice growth processes, resulting in a fitted Stefan coefficient of 2.202. For safety considerations, the Stefan coefficient used for the construction of the ice runway was set at 1.870. We investigated the distribution of lake ice and concluded that the lake ice runway should be established in the north. We established the relationship between ice thickness, cumulative snowfall, and negative accumulated temperature by integrating the fitting technique with the Stefan model. Utilizing the P-III method, the minimum value of the maximum negative accumulated temperature for the 50-year return period is 2092.46 °C·d, while the maximum cumulative snowfall for the 50-year period is 58.4 mm. We can apply these values to the aforementioned relationship to derive the ice thickness patterns across varying return periods. Finally, the study provides recommendations for the construction of the ice runway at Huhenuoer Lake. This study introduces ice field research and an ice growth model into the analysis of lake ice runway operations to provide technical assistance for ice runways. Full article

(This article belongs to the Special Issue Ice and Snow Properties and Their Applications)

16 pages, 3126 KiB

Open AccessArticle

A Soil Refractive Index (SRI) Model Characterizing the Functional Relationship Between Soil Moisture Content and Permittivity

by Erji Du, Lin Zhao, Guojie Hu, Zanpin Xing, Tonghua Wu, Xiaodong Wu, Ren Li, Defu Zou, Guangyue Liu, Lingxiao Wang, Zhibin Li, Yuxin Zhang, Yao Xiao and Yonghua Zhao

Water 2025, 17(3), 399; https://doi.org/10.3390/w17030399 - 31 Jan 2025

Viewed by 330

Abstract

The functional relationship between soil permittivity and soil water content serves as the theoretical foundation for electromagnetic wave-based techniques used to determine soil moisture levels. However, the response of permittivity to changes in soil water content varies significantly across different soil types. Current [...] Read more.

The functional relationship between soil permittivity and soil water content serves as the theoretical foundation for electromagnetic wave-based techniques used to determine soil moisture levels. However, the response of permittivity to changes in soil water content varies significantly across different soil types. Current models that utilize soil permittivity to estimate soil water content are often based on empirical statistical relationships specific to particular soil types. Moreover, existing physical models are hindered by an excessive number of parameters, which can be difficult to measure or calculate. This study introduces a universal model, termed the Soil Refractive Index (SRI) model, to describe the relationship between soil permittivity and soil water content. The SRI model is derived from the propagation velocity of electromagnetic waves in various soil components and the functional relationship between electromagnetic wave velocity and relative permittivity. The SRI model expresses soil water content as a linear function of the square root of the relative permittivity for any soil type with the slope and intercept as the two undetermined parameters. The slope is primarily influenced by the relative permittivity of soil water, while the intercept is mainly affected by both the slope and the soil porosity. The applicability of the SRI model is validated through tested soil samples and comparison with previously published empirical statistical models. For dielectric lossless soil, the theoretical value of the slope is calculated to be 0.126. The intercept varies across different soil types and increases linearly with soil porosity. The SRI model provides a theoretical basis for calculating soil water content using permittivity across various soil types. Full article

(This article belongs to the Section Soil and Water)

► Show Figures

Figure 1

25 pages, 4497 KiB

Open AccessArticle

Regional Gaps, Spatial Distribution Patterns, and Evolutionary Trends of Marine New Quality Productivity in China

by Renhong Wu, Wei Wang, Lihua Yang and Yao Wu

Water 2025, 17(3), 398; https://doi.org/10.3390/w17030398 - 31 Jan 2025

Viewed by 327

Abstract

By analyzing a comprehensive dataset of marine economic activity in China’s 11 coastal provincial administrative regions from 2006 to 2021, we constructed productivity indices to identify regional differences, spatial distribution patterns, and evolutionary trends at the national level, with particular focus on the [...] Read more.

By analyzing a comprehensive dataset of marine economic activity in China’s 11 coastal provincial administrative regions from 2006 to 2021, we constructed productivity indices to identify regional differences, spatial distribution patterns, and evolutionary trends at the national level, with particular focus on the three major maritime economic circles. The results indicate that China’s marine economy is generally growing, and development of marine new quality productivity (MNQP) in the eastern maritime economic circle is better than that in the northern and southern maritime economic circles. This regional gap in coastal areas at low, high, and higher levels gradually increases, while the regional gap decreases in coastal areas at lower levels. The gaps in the degree of openness to the outside world (X4) and in the level of financial development (X7) are the main factors contributing to regional differences in China’s marine new quality productivity. The overall center of gravity of marine new quality productivity is in the south, indicating the rapid growth momentum of the southern maritime economic circle; China’s marine new quality productivity shows a northeast–southwest distribution pattern; and the degree of agglomeration of China’s marine new quality productivity has increased. In the process of moving towards balanced and coordinated regional development of China’s marine industry, there are both opportunities and challenges. Breaking the self-locking tendencies of the lower-level state and preventing its downgrading are the biggest challenges for achieving this goal. However, China’s marine new quality productivity will be stabilized in states at high and higher levels. Full article

Journal Menu

Journal Browser

Water, Volume 17, Issue 3 (February-1 2025) – 142 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI