Water

18 pages, 7485 KiB

Open AccessArticle

Flow Pattern and Turbulent Kinetic Energy Analysis Around Tandem Piers: Insights from k-ε Modelling and Acoustic Doppler Velocimetry Measurements

by Nima Ikani, Jaan H. Pu and Saba Soori

Water 2025, 17(7), 1100; https://doi.org/10.3390/w17071100 (registering DOI) - 7 Apr 2025

Abstract

This study investigated the distribution and dynamics of the Turbulent Kinetic Energy (TKE) around a group of three tandem piers using a combination of numerical simulations and experimental measurements. The Volume of Fluid (VOF) method, coupled with the k-

ε

turbulence model, [...] Read more.

This study investigated the distribution and dynamics of the Turbulent Kinetic Energy (TKE) around a group of three tandem piers using a combination of numerical simulations and experimental measurements. The Volume of Fluid (VOF) method, coupled with the k-

ε

turbulence model, was implemented in ANSYS FLUENT to replicate the free-surface flow conditions. An experimental validation was conducted using Acoustic Doppler Velocimetry (ADV) to assess the model’s capability at capturing the turbulence characteristics. While the model effectively reproduced the near-bed turbulence, it consistently underestimated the TKE magnitudes across the flow domain, particularly in regions of strong vortex-induced turbulence. Discrepancies emerged in the confined regions between the piers, where the velocity profiles were overestimated at the surface and underestimated near the bed and mid-depth, impacting the TKE predictions. Despite these inconsistencies, the general pattern of the TKE distribution aligned with the experimental trends, though the absolute values remained underestimated due to the inherent limitations of the k-

ε

model. The model’s performance in less turbulent regions demonstrated improved accuracy, reinforcing its applicability for moderate turbulence simulations. To further examine the interaction between vortex structures and the TKE, velocity distributions were analyzed at three specific depths (z/h = 0.15, 0.4, and 0.62). The findings showed the critical role of vortex shedding in TKE generation and dissipation, with notable variations in the turbulence intensity influenced by structural confinement effects. This study offers a novel, high-resolution evaluation of the k-ε model’s ability to predict TKE distributions around tandem piers, using spatially detailed comparisons with the experimental data. Unlike previous studies that broadly acknowledged the model’s limitations, this work systematically identifies the specific regions, particularly vortex-dominated zones, where its predictive accuracy significantly degrades. Full article

(This article belongs to the Special Issue Bridging the Gaps: Hydrological Research for Sustainable River Management)

► Show Figures

Figure 1

19 pages, 4770 KiB

Open AccessArticle

Enhanced Three-Dimensional (3D) Drought Tracking for Future Migration Patterns in China Under CMIP6 Projections

by Sijia Wu, Ximing Chen, Jiejun Huang, Yanbin Yuan, Han Zhou and Liangcun Jiang

Water 2025, 17(7), 1099; https://doi.org/10.3390/w17071099 (registering DOI) - 7 Apr 2025

Abstract

Analyzing drought evolution requires dynamic three-dimensional methods to capture spatiotemporal continuity. Existing approaches oversimplify drought patch connectivity by relying on overlapping logic, thereby neglecting dynamic evolution. We propose a novel three-dimensional identification method incorporating spatial autocorrelation and anisotropy. Using the ERA5 dataset and [...] Read more.

Analyzing drought evolution requires dynamic three-dimensional methods to capture spatiotemporal continuity. Existing approaches oversimplify drought patch connectivity by relying on overlapping logic, thereby neglecting dynamic evolution. We propose a novel three-dimensional identification method incorporating spatial autocorrelation and anisotropy. Using the ERA5 dataset and the multi-model ensemble mean (MEM) of CMIP6, we investigate meteorological drought characteristics and migration patterns in China during 1961–2010 (historical) and 2031–2080 (future, SSP2-4.5/SSP5-8.5). Results indicate future drought frequency may decline by over 70% compared to historical levels, but severity, duration, affected area, and migration distance could increase significantly. Most future droughts (96.3% for SSP2-4.5; 95.0% for SSP5-8.5) are projected in spring and summer. Drought trajectories may predominantly shift northeastward (33% for SSP2-4.5; 38% for SSP5-8.5), with migration hotspots transitioning from the upper Yangtze River Basin to the upper Yellow River Basin. These findings enhance the understanding of drought dynamics and support the development of improved drought monitoring frameworks. The methodology and projections provide critical insights for drought risk management and adaptive water resource planning under climate change. Full article

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

► Show Figures

Figure 1

23 pages, 6099 KiB

Open AccessArticle

Evaluation of ICESat-2 Laser Altimetry for Inland Water Level Monitoring: A Case Study of Canadian Lakes

by Yunus Kaya

Water 2025, 17(7), 1098; https://doi.org/10.3390/w17071098 (registering DOI) - 6 Apr 2025

Abstract

This study evaluates the performance of the ICESat-2 ATL13 altimetry product for estimating water levels in 182 Canadian lakes by integrating satellite-derived observations with in situ gauge measurements and applying spatial filtering using the HydroLAKES dataset. The analysis compares ATL13-derived lake surface elevations [...] Read more.

This study evaluates the performance of the ICESat-2 ATL13 altimetry product for estimating water levels in 182 Canadian lakes by integrating satellite-derived observations with in situ gauge measurements and applying spatial filtering using the HydroLAKES dataset. The analysis compares ATL13-derived lake surface elevations with hydrometric data from national monitoring stations, providing a robust framework for assessing measurement accuracy. Statistical metrics—including root mean square error (RMSE), mean absolute error (MAE), and mean bias error (MBE)—are employed to quantify discrepancies between the datasets. Importantly, the application of HydroLAKES-based filtering reduces the mean RMSE from 1.53 m to 1.40 m, and the further exclusion of high-error lakes lowers it to 0.96 m. Larger and deeper lakes exhibit lower error margins, while smaller lakes with complex shorelines show greater variability. Regression analysis confirms the excellent agreement between satellite and gauge measurements (R² = 0.9999; Pearson’s r = 0.9999, n = 182 lakes, p < 0.0001). Temporal trends reveal declining water levels in 134 lakes and increasing levels in 48 lakes from 2018 to 2024, potentially reflecting climatic variability and human influence. These findings highlight the potential utility of ICESat-2 ATL13 altimetry for large-scale inland water monitoring when combined with spatial filtering techniques such as HydroLAKES. Full article

(This article belongs to the Special Issue Use of Remote Sensing Technologies for Water Resources Management)

► Show Figures

Figure 1

30 pages, 2923 KiB

Open AccessFeature PaperArticle

Assessing the Relationship Between Groundwater Availability, Access, and Contamination Risk in Arizona’s Drinking Water Sources

by Simone A. Williams, Adriana A. Zuniga-Teran, Sharon B. Megdal, David M. Quanrud and Gary Christopherson

Water 2025, 17(7), 1097; https://doi.org/10.3390/w17071097 (registering DOI) - 6 Apr 2025

Abstract

Groundwater is a critical drinking water source in arid regions globally, where reliance on groundwater is highest. However, disparities in groundwater availability, access, and quality pose challenges to water security. This case study employs geostatistical tools, multivariate regression, and clustering analysis to examine [...] Read more.

Groundwater is a critical drinking water source in arid regions globally, where reliance on groundwater is highest. However, disparities in groundwater availability, access, and quality pose challenges to water security. This case study employs geostatistical tools, multivariate regression, and clustering analysis to examine the intersection of groundwater level changes (availability), socioeconomic and regulatory factors (access), and nitrate and arsenic contamination (quality) across 1881 groundwater-supplied drinking water service areas in Arizona. Groundwater availability declined over 20-year and 10-year periods, particularly outside designated management areas, with mean annual decline rates ranging from −15.97 to −0.003 m/year. In contrast, increases (0.003 to 13.41 m/year) were concentrated in urban and managed areas. Karst aquifers show long-term resilience but short-term vulnerability. Non-designated areas exhibit mixed effects, reflecting variable management effectiveness. Disparities in groundwater access emerge along various socioeconomic and regulatory lines. Communities with higher Black populations are twice as likely (OR = 2.01, p < 0.001) to experience groundwater declines, while Hispanic/Latino communities have lower depletion risks (OR = 0.92, p < 0.001). Tribal oversight significantly reduces groundwater decline risk (OR = 0.62, p < 0.001), whereas state–primacy areas show mixed effects. Higher female populations correlate with increased groundwater declines, while older populations (65+) experience greater stability. Married-family households and institutional housing are associated with greater declines. Migrant worker housing shows protective effects in long-term models. Rising groundwater levels are associated with higher nitrate and arsenic detection, reinforcing recharge-driven contaminant mobilization. Nitrate exceedance (OR = 1.05) responds more to short-term groundwater changes, while arsenic exceedance persists over longer timescales (OR = 1.01–1.05), reflecting their distinct hydrogeochemical behaviors. Community water systems show higher pollutant detection rates than domestic well areas, suggesting monitoring and infrastructure differences influence contamination patterns. Tribal primacy areas experience lower groundwater declines but show mixed effects on water quality, with reduced nitrate exceedance probabilities; yet they show variable arsenic contamination patterns, suggesting that governance influences availability and contamination dynamics. These findings advance groundwater sustainability research by quantifying disparities across multiple timescales and socio-hydrogeological drivers of groundwater vulnerability. The results underscore the need for expanded managed aquifer recharge, targeted regulatory interventions, and strengthened Tribal water governance to reduce inequities in availability, access, and contamination risk to support equitable and sustainable groundwater management. Full article

(This article belongs to the Special Issue Field Monitoring, GIS, Remote Sensing, Geophysical Techniques, and Hydrochemical Analysis in Groundwater Investigations)

► Show Figures

Figure 1

19 pages, 7042 KiB

Open AccessArticle

Hydrological Effects of Bioretention Facilities in an Environment with a High Groundwater Table and Their Impacts on Groundwater

by Yuhui Wang, Yilan Yang, Haolang Liu, Zizhen Qi, Siyu Tian, Xiangjing Mo, Hanbo Chen and Yongwei Gong

Water 2025, 17(7), 1096; https://doi.org/10.3390/w17071096 (registering DOI) - 6 Apr 2025

Abstract

With urbanization accelerating, low-impact development (LID) facilities, particularly bioretention facilities, play a crucial role in urban water management. However, rising groundwater tables present challenges for their application in high-water-table areas. This study experimentally evaluated the impact of shallow groundwater tables on the hydrological [...] Read more.

With urbanization accelerating, low-impact development (LID) facilities, particularly bioretention facilities, play a crucial role in urban water management. However, rising groundwater tables present challenges for their application in high-water-table areas. This study experimentally evaluated the impact of shallow groundwater tables on the hydrological performance of bioretention facilities. The experiment was designed to evaluate the effects of different groundwater table levels, soil media types, runoff ratios, and rainfall characteristics on hydrological responses. It also examined their impact on drainage pipe design and groundwater recharge. Results showed that as the groundwater table rose from 0.2 m to 0.5 m, the drainage pipe discharge increased (Facility #1: 52%→76%, Facility #3: 31%→58%) while the groundwater recharge decreased (Facility #1: 44%→17%, Facility #3: 63%→39%). This indicates that a higher groundwater table intensifies the diversion effect of the drainage pipe, increasing the proportion of stormwater discharged while reducing the proportion infiltrating to recharge the groundwater. Under moderate to heavy rainfall, sandy loam reduced the drainage time by 41–43% and increased the groundwater recharge by up to 80%. Without drainage pipes, sandy loam enhanced the recharge rates (α = 0.87), and #3 exhibited superior infiltration. Rainfall intensity and interval significantly influenced the hydrological performance. Full article

(This article belongs to the Special Issue Urban Water Management: Challenges and Prospects)

► Show Figures

Figure 1

32 pages, 753 KiB

Open AccessReview

A Comprehensive Review and Application of Bayesian Methods in Hydrological Modelling: Past, Present, and Future Directions

by Khaled Haddad

Water 2025, 17(7), 1095; https://doi.org/10.3390/w17071095 (registering DOI) - 6 Apr 2025

Abstract

Bayesian methods have revolutionised hydrological modelling by providing a framework for managing uncertainty, improving model calibration, and enabling more accurate predictions. This paper reviews the evolution of Bayesian methods in hydrology, from their initial applications in flood-frequency analysis to their current use in [...] Read more.

Bayesian methods have revolutionised hydrological modelling by providing a framework for managing uncertainty, improving model calibration, and enabling more accurate predictions. This paper reviews the evolution of Bayesian methods in hydrology, from their initial applications in flood-frequency analysis to their current use in streamflow forecasting, flood risk assessment, and climate-change adaptation. It discusses the development of key Bayesian techniques, such as Markov Chain Monte Carlo (MCMC) methods, hierarchical models, and approximate Bayesian computation (ABC), and their integration with remote sensing and big data analytics. The paper also presents simulated examples demonstrating the application of Bayesian methods to flood, drought, and rainfall data, showcasing the potential of these methods to inform water-resource management, flood risk mitigation, and drought prediction. The future of Bayesian hydrology lies in expanding the use of machine learning, improving computational efficiency, and integrating large-scale datasets from remote sensing. This review serves as a resource for hydrologists seeking to understand the evolution and future potential of Bayesian methods in addressing complex hydrological challenges. Full article

(This article belongs to the Section Hydrology)

17 pages, 13692 KiB

Open AccessArticle

Numerical Simulation of the Hydrodynamic Behavior of Immersed Tunnel in Waves

by Hang Shi, Xianlin Jia, Tiaojian Xu and Wo Zhang

Water 2025, 17(7), 1094; https://doi.org/10.3390/w17071094 (registering DOI) - 6 Apr 2025

Abstract

The hydrodynamic response of immersed tunnel in waves is important for the design of immersed tunnel. The numerical wave tank that considers the coupling of wave field and floating body motion is established based on the OpenFOAM. The overset mesh method is adopted [...] Read more.

The hydrodynamic response of immersed tunnel in waves is important for the design of immersed tunnel. The numerical wave tank that considers the coupling of wave field and floating body motion is established based on the OpenFOAM. The overset mesh method is adopted to refresh the meshes around the immersed tunnel in waves. In addition, the experimental data of floating body motion and wave force is applied to validate the numerical model. The hydrodynamic characteristics of the immersed tunnel under wave loads are numerically studied, focusing on the motion response and the force of the immersed tunnel. The results show that with the increase in wave height, the roll of the immersed tunnel increases, the amplitude of the horizontal force increases significantly, the amplitude of the vertical force remains basically unchanged, and the nonlinear enhancement of the roll motion response is observed. When the wave period is close to the natural period of the floating body, the roll angle reaches its maximum. Under irregular wave conditions, with the increase in significant wave height, the average amplitude of the immersed tunnel’s roll motion increases, which is significantly greater (about 2–3 times) than that under regular wave conditions. With the increasing average amplitude of horizontal force, the change in vertical force is not significant. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

22 pages, 8036 KiB

Open AccessArticle

Research on the Characteristics of Sediment Erosion in Pump-Turbine Runners Under Different Solid-Phase Conditions

by Jiaxing Lu, Yanjun He, Yuzhuo Zhou, Chuan Zhang, Yuanyuan Pan and Jiarui Li

Water 2025, 17(7), 1093; https://doi.org/10.3390/w17071093 (registering DOI) - 6 Apr 2025

Abstract

Sediment erosion in turbine components presents a major challenge to the reliable operation of pumped storage power plants, particularly in sediment-laden rivers. While extensive research has been conducted on hydraulic machinery erosion, studies focusing on the combined effects of sediment particle size and [...] Read more.

Sediment erosion in turbine components presents a major challenge to the reliable operation of pumped storage power plants, particularly in sediment-laden rivers. While extensive research has been conducted on hydraulic machinery erosion, studies focusing on the combined effects of sediment particle size and concentration on erosion within the runner region of pump turbines remain limited. To bridge this gap, this study investigates the influence of sediment characteristics on erosion patterns and deposition mechanisms in pump-turbine runners through a combination of numerical simulations and experimental validation. The results demonstrate that sediment concentration primarily governs the overall erosion intensity, while particle size significantly influences the spatial distribution of erosion zones. Higher sediment concentrations lead to intensified surface wear and broader erosion regions, whereas larger particles cause localized shifts in erosion-prone areas across different blade surfaces. Furthermore, a strong correlation is identified between erosion zones and sediment accretion regions, highlighting the interplay between material loss and deposition dynamics. By accurately predicting erosion trends, numerical simulations minimize the reliance on costly and time-consuming physical experiments, offering valuable insights for turbine optimization. This study enhances the understanding of sediment-induced erosion mechanisms in pump turbines and provides guidance for improving turbine design and operational strategies in sediment-laden environments. Full article

► Show Figures

Figure 1

20 pages, 12609 KiB

Open AccessArticle

Response of Riverbed Shaping to a Flood Event in the Reach from Alar to Xinquman in the Mainstream of the Tarim River

by Mingcheng Zhao, Yujian Li, Lin Li and Wenhong Dai

Water 2025, 17(7), 1092; https://doi.org/10.3390/w17071092 (registering DOI) - 6 Apr 2025

Abstract

As the largest inland river in China, the Tarim River’s flood events significantly influence its riverbed formation. This paper took the Alar to Xinquman section of the Tarim River as the study area. The study area’s digital elevation model of the river was [...] Read more.

As the largest inland river in China, the Tarim River’s flood events significantly influence its riverbed formation. This paper took the Alar to Xinquman section of the Tarim River as the study area. The study area’s digital elevation model of the river was constructed using historical Google images and Copernicus DEM 30. Six different flood events were selected, corresponding to flood events with varying sediment loads, flood volumes, and peak flow volumes. The MIKE 21 software was used to simulate and investigate the response of the riverbed shape to different flood events. The experimental findings indicate that the sand content constitutes a pivotal factor in the formation of the riverbed during flood events. Flood sediment load goes through stages linked to changes in riverbed erosion and deposition. The combination of high peak flow and bed-forming flow after the peak effectively shapes the central channel’s morphology. The fourth type of flood event had the highest sediment transport coefficient Φ among the six types of floods and caused the most significant scouring effect on the riverbed under low sediment load conditions. Full article

(This article belongs to the Special Issue Flow Dynamics and Sediment Transport in Rivers and Coasts)

► Show Figures

Figure 1

26 pages, 12924 KiB

Open AccessArticle

A Comparative Analysis of In-Situ Wave Measurements and Reanalysis Models for Predicting Coastline Evolution: A Case Study of IJmuiden, The Netherlands

by Joaquim Pais-Barbosa, Frederico Romão, Márcia Lima and Carlos Coelho

Water 2025, 17(7), 1091; https://doi.org/10.3390/w17071091 (registering DOI) - 5 Apr 2025

Abstract

This study investigates the influence of wave-climate datasets derived from in situ measurements and reanalysis models on predictive modelling accuracy for coastline evolution, focusing on the IJmuiden coastal stretch in The Netherlands. By analyzing wave parameters, sediment dynamics, and nourishment interventions, the research [...] Read more.

This study investigates the influence of wave-climate datasets derived from in situ measurements and reanalysis models on predictive modelling accuracy for coastline evolution, focusing on the IJmuiden coastal stretch in The Netherlands. By analyzing wave parameters, sediment dynamics, and nourishment interventions, the research evaluates the performance of a numerical model in simulating shoreline changes over a 40-year period. Using the LTC (Long-Term Configuration) model, scenarios incorporating artificial sand nourishment volumes of 200,000 m³/year and 250,000 m³/year were tested against conditions without nourishment. The results highlighted the critical role of significant wave height, direction, and dataset variability in sediment accretion and erosion patterns. Datasets from in situ measurements (Measured-YM6) and reanalysis sources (ERA5, AENWS-WPR, and AENWS-WPR North) demonstrate variable performance, with ERA5 proving to be the most reliable under both nourished and non-nourished scenarios. The findings emphasize the importance of integrating high-resolution wave datasets into numerical models to improve predictions, optimize nourishment strategies, and enhance coastal resilience against erosion. The study underscores the necessity of nourishment interventions to mitigate sediment loss, stabilize shorelines, and support sustainable coastal-management practices in the face of climate change. Full article

(This article belongs to the Special Issue Coastal Geomorphology Response to Environmental and Climate Change)

► Show Figures

Figure 1

14 pages, 4634 KiB

Open AccessArticle

Characteristics of Medium Resistivity Response During the Water–Oil Displacement Process

by Guizhang Zhao, Jie An, Huan Zhu and Hongli Zhang

Water 2025, 17(7), 1090; https://doi.org/10.3390/w17071090 (registering DOI) - 5 Apr 2025

Abstract

Oil leakage during the processes of extraction, storage, and transportation poses a significant challenge due to the complex nature of pollution caused by frequent fluctuations in groundwater levels and variations in the water–oil interface. To effectively identify and monitor the position of the [...] Read more.

Oil leakage during the processes of extraction, storage, and transportation poses a significant challenge due to the complex nature of pollution caused by frequent fluctuations in groundwater levels and variations in the water–oil interface. To effectively identify and monitor the position of the water–oil interface and displacement processes, geophysical methods have proven to be an efficient approach. This study utilizes electrical resistivity measurements to analyze changes in medium resistivity during water–oil displacement, enabling simulation of the spatial relationship between groundwater levels and petroleum contaminants based on resistivity characteristics and natural potential responses. After analysis, the following conclusions can be drawn: (1) During the water displacement process, when water forms a connected flow channel between sand and gravel, the resistivity decreases abruptly. Conversely, during oil displacement by water, when oil fills soil pores and creates a high-resistance conductive path, the resistivity increases abruptly. (2) Changes in resistivity are determined by the position of the water–oil interface. By observing characteristic changes in resistivity, it is possible to verify whether soil is undergoing water–oil displacement. (3) The direction of displacement significantly affects changes in resistivity for all three media involved due to gravity effects during water displacement by the oil process. (4) Resistance values during the water–oil displacement process are directly influenced by the size of sand particles used in experiments. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

16 pages, 5810 KiB

Open AccessArticle

Deep Learning Downscaling of Precipitation Projection over Central Asia

by Yichang Jiang, Jianing Guo, Lei Fan, Hui Sun and Xiaoning Xie

Water 2025, 17(7), 1089; https://doi.org/10.3390/w17071089 (registering DOI) - 5 Apr 2025

Abstract

Central Asia, as a chronically water-stressed region marked by extreme aridity, faces significant environmental challenges from intensifying desertification and deteriorating ecological stability. The region’s vulnerability to shifting precipitation regimes and extreme hydrometeorological events has been magnified under anthropogenic climate forcing. Although global climate [...] Read more.

Central Asia, as a chronically water-stressed region marked by extreme aridity, faces significant environmental challenges from intensifying desertification and deteriorating ecological stability. The region’s vulnerability to shifting precipitation regimes and extreme hydrometeorological events has been magnified under anthropogenic climate forcing. Although global climate models (GCMs) remain essential tools for climate projections, their utility in Central Asia’s complex terrain is constrained by inherent limitations: coarse spatial resolution (~100–250 km) and imperfect parameterization of orographic precipitation mechanisms. This investigation advances precipitation modeling through deep learning-enhanced statistical downscaling, employing convolutional neural networks (CNNs) to generate high-resolution precipitation data at approximately 10 km resolution. Our results show that the deep learning models successfully simulate the high center of precipitation and extreme precipitation near the Tianshan Mountains, exhibiting high spatial applicability. Under intermediate (SSP-245) and high-emission (SSP-585) future scenarios, the increase in extreme precipitation over the next century is significantly more pronounced compared to mean precipitation. By the end of the 21st century, the interannual variability of mean precipitation and extreme precipitation will become even larger under SSP-585, indicating an increased risk of extreme droughts/floods in Central Asia under high greenhouse gas emissions. Our findings provide technical support for climate change impact assessments in the region and highlight the potential of CNN-based downscaling for future climate change studies. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Water Resources and Water Risks, 2nd Edition)

► Show Figures

Figure 1

15 pages, 9265 KiB

Open AccessArticle

Numerical Simulation of the Unsteady 3D Flow in Vertical Slot Fishway—The Impact of Macro-Roughness

by Gérard Pineau, Aurélien Ballu, Laurent David and Damien Calluaud

Water 2025, 17(7), 1088; https://doi.org/10.3390/w17071088 (registering DOI) - 5 Apr 2025

Abstract

Vertical slot fishways (VSFs) are crossing devices that are built on rivers or streams. They were initially designed to help salmons to complete their migratory cycle by crossing permanent obstructions. In order to favor the passage of smaller or benthic species, stones or [...] Read more.

Vertical slot fishways (VSFs) are crossing devices that are built on rivers or streams. They were initially designed to help salmons to complete their migratory cycle by crossing permanent obstructions. In order to favor the passage of smaller or benthic species, stones or concrete cylinders, called macro-roughnesses, are often inserted at the bottom of the fishway. To study the effects of macro-roughnesses on the flow inside a VSF, three-dimensional unsteady simulations were carried out using the volume of fluid method to model the free surface. In this paper, kinematic quantities obtained by CFD are used to detail the flow inside a VSF with and without macro-roughnesses. It can provide valuable information about the flow characteristics, especially in areas where the experimental measurements are difficult to implement. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

► Show Figures

Figure 1

20 pages, 5003 KiB

Open AccessArticle

Assessment of Mercury Contamination in the Chalk Aquifer of the Pays de Caux and Its Implications for Public Health (France)

by Lahcen Zouhri, Jacques Delépine and Lockman Zouhri

Water 2025, 17(7), 1087; https://doi.org/10.3390/w17071087 (registering DOI) - 5 Apr 2025

Abstract

Mercury is naturally present in soils at trace concentrations, but its cycle is increasingly disrupted by anthropogenic activities, which affect its distribution and behavior. Due to its toxic nature, mercury has become a significant focus in environmental and public health policies. Following the [...] Read more.

Mercury is naturally present in soils at trace concentrations, but its cycle is increasingly disrupted by anthropogenic activities, which affect its distribution and behavior. Due to its toxic nature, mercury has become a significant focus in environmental and public health policies. Following the detection of mercury anomalies during groundwater quality monitoring at the Pays de Caux study site (France), a comprehensive multidisciplinary research effort was initiated. This included geological and hydrogeological studies aimed at tracking mercury concentrations in piezometric wells and identifying the sources of these anomalies. This study seeks to assess the groundwater quality and characteristics from ten hydrogeological wells. The evaluation will focus on key hydrogeological parameters, including pH, redox potential (Eh), suspended solids, and groundwater levels, as well as a detailed geochemical analysis of elements such as Hg, Fe, Mn, Zn, Pb, and Cu. The mobilization of mercury and other metallic traces elements is strongly governed by environmental factors. Hydrochemical analyses highlight the complex interplay of various parameters that influence the chemical forms and behavior of mercury in both soil and groundwater. The results from the piezometric measurement campaigns (Pz1 to Pz7) have provided crucial insights, enabling the development of hypotheses about mercury’s behavior in the chalk aquifer. It is hypothesized that impermeable areas may trap groundwater for extended periods, leading to the accumulation and abnormal concentration of mercury. This could cause mercury to be intermittently released, potentially affecting the surrounding environment. Mercury concentrations in groundwater are highly sensitive to pH and redox potential (Eh), with low pH and reducing conditions promoting mercury mobilization and the formation of toxic methylated species. The study suggests the chalk aquifer is generally in equilibrium with mercury, but fluctuations in mercury levels between Pz7 and Pz4 are likely due to the heterogeneity of the clay and geological factors such as mineral composition and fracturing. This research provides insights into mercury transfer in heterogeneous environments and emphasizes the need for continuous hydrogeological monitoring, including piezometer readings, to manage mercury dispersion in the aquifer. Full article

(This article belongs to the Section Hydrology)

► Show Figures

Figure 1

13 pages, 5010 KiB

Open AccessArticle

Quantifying the Rainy Season in the Brazilian Northeast Through a Modification of the Relative Entropy Method

by Borko Stosic, Vladimir Djurdjević, Ivana Tošić, Antonio Samuel Alves da Silva and Tatijana Stosic

Water 2025, 17(7), 1086; https://doi.org/10.3390/w17071086 (registering DOI) - 5 Apr 2025

Abstract

In this work, we introduce a modification of the relative entropy method in order to perform geographically explicit quantification of the rainy season across the Brazilian Northeast (NE). We apply this novel approach to data from the ERA5-Land project for the period 1980 [...] Read more.

In this work, we introduce a modification of the relative entropy method in order to perform geographically explicit quantification of the rainy season across the Brazilian Northeast (NE). We apply this novel approach to data from the ERA5-Land project for the period 1980 to 2022, with ~9 km spatial resolution, to obtain the strength of seasonality, the duration of the rainy season (in months), and the center of the rainy season, throughout the NE, both on the ERA5-Land grid and at municipality level. Our results agree well with the results of a number of other publications for several municipalities and regions within the NE. We also provide user-friendly software with graphical user interface for ease of extraction of rainy season parameters (strength, duration, and the center of the rainy season), together with the monthly precipitation series for any point or municipality average. Full article

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

► Show Figures

Figure 1

17 pages, 10920 KiB

Open AccessArticle

Effect of Twist Angle Regulation via Flexible Variable-Twist Blades on External Characteristics of Axial-Flow Pumps

by Jiayuan Liang, Weidong Liu, Xiaocui Chen and Yongjian Wang

Water 2025, 17(7), 1085; https://doi.org/10.3390/w17071085 (registering DOI) - 5 Apr 2025

Abstract

In the field of marine resource development, conventional axial-flow adjustable-blade pumps rely on the monolithic rotation of rigid blades for operational condition regulation, a mechanism constrained by simplistic angular adjustments that inadequately adapt to the dynamic and complex marine operational environment. To address [...] Read more.

In the field of marine resource development, conventional axial-flow adjustable-blade pumps rely on the monolithic rotation of rigid blades for operational condition regulation, a mechanism constrained by simplistic angular adjustments that inadequately adapt to the dynamic and complex marine operational environment. To address this limitation, this study proposes a novel angle-adjustment scheme utilizing flexible variable-twist blades, where operational condition regulation is achieved through active blade twisting, enabling refined and adaptive angle modulation. Four typical blade profiles were selected for the variable-twist blades at distinct angular positions (−1°, +1°, −2°, and +2°), corresponding to the four conventional angle-adjustment positions of axial-flow adjustable-blade pumps. Numerical simulations were conducted to investigate the hydraulic performance impacts of the proposed flexible variable-twist blades compared to traditional rigid blades under identical angular configurations. The results demonstrate that under high-flow conditions (1.2 Q), the torsion-based angle-adjustment strategy exhibits superior efficiency across all four angular positions: −1° configuration: 11.1% efficiency improvement; +1° configuration: comparable efficiency; −2° configuration: 78% efficiency improvement; and +2° configuration: 3.2% efficiency improvement. Moreover, at equivalent angular settings, the variable-twist blades significantly enhance hydraulic performance and expand the high-efficiency operating range of the pump compared to conventional rigid blades. The implementation of flexible variable-twist blade technology not only advances the performance of axial-flow pumps in marine engineering applications but also provides a new approach for high-efficiency research on axial-flow pumps. Full article

(This article belongs to the Special Issue Recent Advances in Hydraulic Machinery and Its Application in Marine Engineering)

► Show Figures

Figure 1

21 pages, 8341 KiB

Open AccessArticle

Flood Risk Management-Level Analysis of Subway Station Spaces

by Yan Li, Xinxin Xu, Shaoxuan Hou, Xin Dang, Zhuolun Li and Yongwei Gong

Water 2025, 17(7), 1084; https://doi.org/10.3390/w17071084 (registering DOI) - 5 Apr 2025

Abstract

In recent years, heavy rainfall-induced flood incidents have occurred frequently in subway stations worldwide. Flooding in complex underground facilities, such as subway stations, can result in significant casualties and property damage. Therefore, it is crucial to determine flood risk management levels within subway [...] Read more.

In recent years, heavy rainfall-induced flood incidents have occurred frequently in subway stations worldwide. Flooding in complex underground facilities, such as subway stations, can result in significant casualties and property damage. Therefore, it is crucial to determine flood risk management levels within subway stations. This study proposes a comprehensive flood management-level evaluation method based on spatial network importance, spatial functional importance, and flood risk, focusing on the relationship between the complex spatial structure of subway stations and flood risk. The research integrates complex network theory and hydrodynamic simulation techniques to construct a spatial network model within subway stations, assessing the importance index of each subspace in the network. Simultaneously, the spatial functional importance index is calculated through quantitative analysis of different subspace functions. Additionally, the Volume of Fluid (VOF) model is used to simulate flood distribution, obtaining the flood risk index for each subspace. By applying the entropy weight method for comprehensive analysis, the flood risk management levels of various areas within the subway station are determined. The results indicate that among all evaluation indicators, the importance of the subway network is assigned the highest weight, accounting for 50%. Specifically, the spatial network importance of the S6 station hall, S11 station hall, and the connecting corridors between S1–S6 and S11–S6 exceeds 0.48, with these areas constituting 75% of the total subway station space. This highlights their central role in crowd flow and spatial connectivity. The study found that areas with a flood risk management level of five occupy 11.43% of the total space, indicating that prioritizing the management and flood prevention measures in critical areas is essential for enhancing the subway station’s resilience. This study provides both theoretical support and practical references for the risk management of subway station spaces. Full article

(This article belongs to the Special Issue Recent Advances in Flood Risk Assessment and Management)

► Show Figures

Figure 1

23 pages, 69587 KiB

Open AccessArticle

Investigating Steady-State Interpolation and Transient Hydraulic Modelling to Evaluate European Grayling Habitat in a Hydropeaking River

by Frida M. Niemi, Anders G. Andersson, J. Gunnar I. Hellström, Mahboobeh Hajiesmaeili and David Aldvén

Water 2025, 17(7), 1083; https://doi.org/10.3390/w17071083 - 4 Apr 2025

Abstract

Renewable energy sources such as hydropower are important to reduce the global emissions. Hydropower, however, comes with other environmental challenges by altering the ecological conditions in the rivers. Hydraulic models connected with fish habitat models could be one tool to assess the environmental [...] Read more.

Renewable energy sources such as hydropower are important to reduce the global emissions. Hydropower, however, comes with other environmental challenges by altering the ecological conditions in the rivers. Hydraulic models connected with fish habitat models could be one tool to assess the environmental impacts and evaluate mitigation measures for fish habitats. This study examines the limitations of steady-state hydraulic simulations in a low-sloping river located between two hydropower plants, where downstream regulations significantly influence the river flow dynamics. A 2D hydrodynamic model in Delft3D FM was applied to compare steady-state and transient simulations, focusing on how hydraulic variables affect the spawning habitat. The results show that steady-state models fail to capture time-dependent damping and delayed water level responses, leading to systematic underestimation of hydraulic variability. Peak bed shear stress values were under-predicted by the steady-state interpolation, which may under-predict spawning ground stability. Additionally, the steady-state approach failed to capture daily habitat fluctuations, resulting in a mean absolute error of 2910 m² in spawning habitat area per hour. This study demonstrates how errors in hydraulic calculations propagate into habitat assessments, potentially leading to misleading long-term evaluations of fish populations. This study highlights the importance of selecting appropriate hydraulic modelling approaches based on river-specific flow dynamics. Future studies should investigate the sensitivity of fish habitat models to hydraulic inputs from steady-state and transient simulations by integrating these approaches into advanced fish modelling tools, such as individual-based models. This will help determine the optimal balance between computational efficiency and accuracy in long-term habitat assessments. Full article

► Show Figures

Figure 1

24 pages, 3356 KiB

Open AccessArticle

Inflows into Wastewater and Stormwater Systems: Sources, Causes, and Assessment

by Maria do Céu Almeida, Rita Salgado Brito and Catarina Jorge

Water 2025, 17(7), 1082; https://doi.org/10.3390/w17071082 - 4 Apr 2025

Abstract

Illicit or inappropriate inflows into urban drainage systems cause significant operational issues, impacting utilities, communities, and the environment. The continued deterioration of system assets increases these inflows. Groundwater infiltration, rain-derived inflows, and misconnections contribute to reduced system performance, amongst other detrimental inflows. Climate [...] Read more.

Illicit or inappropriate inflows into urban drainage systems cause significant operational issues, impacting utilities, communities, and the environment. The continued deterioration of system assets increases these inflows. Groundwater infiltration, rain-derived inflows, and misconnections contribute to reduced system performance, amongst other detrimental inflows. Climate change effects and the revised EU Wastewater Treatment Directive put pressure on utilities to reduce combined sewage and polluted stormwater discharges and overflows while promoting carbon neutrality. The effective management of undue inflows requires identifying cause–effect relationships and quantifying their consequences. This paper proposes a performance-based methodology with metrics and reference values to assess and categorise various undue inflows in wastewater, stormwater, or combined systems. This approach allows the tracking of performance over time, the comparing of systems, and requires data commonly available to utilities. The reliable quantification of inflows depends on the availability and accuracy of flow data from relevant system locations, rainfall data, and pertinent contextual information. This paper uses data from eight utilities and the Portuguese regulator to validate its approach, calculate metrics, refine reference values and enable better-targeted control measures. The results enhance the value of a unified approach to this problem in making better decisions to improve the urban water drainage system’s performance, enhance pollution control, and promote sustainable water management. Full article

(This article belongs to the Section Urban Water Management)

► Show Figures

Figure 1

Journal Description

Water

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI