Water

19 pages, 4944 KiB

Open AccessArticle

2D-URANS Study on the Impact of Relative Diameter on the Flow and Drag Characteristics of Circular Cylinder Arrays

by Mengyang Liu, Yisen Wang, Yiqing Gong and Shuxia Wang

Water 2024, 16(16), 2264; https://doi.org/10.3390/w16162264 (registering DOI) - 11 Aug 2024

The flow structure around limited-size vegetation patches is crucial for understanding sediment transport and vegetation succession trends. While the influence of vegetation density has been extensively explored, the impact of the relative diameter of vegetation stems remains relatively unclear. After validating the reliability [...] Read more.

The flow structure around limited-size vegetation patches is crucial for understanding sediment transport and vegetation succession trends. While the influence of vegetation density has been extensively explored, the impact of the relative diameter of vegetation stems remains relatively unclear. After validating the reliability of the numerical model with experimental data, this study conducted 2D-URANS simulations (SST k-ω) to investigate the impact of varying relative diameters d/D under different vegetation densities λ on the hydrodynamic characteristics and drag force of vegetation patches. The results show that increasing d/D and decreasing λ are equivalent, both contributing to increased spacing between cylinder elements, allowing for the formation of element-scale Kármán vortices. Compared to vegetation density λ, the non-dimensional frontal area aD is a better predictor for the presence of array-scale Kármán vortex streets. Within the parameter range covered in this study, array-scale Kármán vortex streets appear when aD ≥ 1.4, which will significantly alter sediment transport patterns. For the same vegetation density, increasing the relative diameter d/D leads to a decrease in the array drag coefficient

{\bar{C}}_{D}

and an increase in the average element drag coefficient

{\bar{C}}_{d}

. When parameterizing vegetation resistance using aD, all data points collapse onto a single curve, following the relationships

{\bar{C}}_{D} = 0.34 \ln (a D) + 0.78

and

{\bar{C}}_{d} = - 0.42 \ln (a D) + 0.82

. Full article

(This article belongs to the Special Issue The Safety Operations and Intelligent Control of Water Network Engineering Systems)

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13 pages, 8158 KiB

Open AccessArticle

Towards Non-Region Specific Large-Scale Inundation Modelling with Machine Learning Methods

by Lachlan Tychsen-Smith, Mohammad Ali Armin and Fazlul Karim

Water 2024, 16(16), 2263; https://doi.org/10.3390/w16162263 (registering DOI) - 11 Aug 2024

Abstract

Traditional flood inundation modelling methods are computationally expensive and not suitable for near-real time inundation prediction. In this study we explore a data-driven machine learning method to complement and, in some cases, replace existing methods. Given sufficient training data and model capacity, our [...] Read more.

Traditional flood inundation modelling methods are computationally expensive and not suitable for near-real time inundation prediction. In this study we explore a data-driven machine learning method to complement and, in some cases, replace existing methods. Given sufficient training data and model capacity, our design enables a single neural network instance to approximate the flow characteristics of any input region, opening the possibility of applying the model to regions without available training data. To demonstrate the method we apply it to a very large >8000 km² region of the Fitzroy river basin in Western Australia with a spatial resolution of 30 m × 30 m, placing an emphasis on efficiency and scalability. In this work we identify and address a range of practical limitations, e.g., we develop a novel water height regression method and cost function to address extreme class imbalances and by carefully constructing the input data, we introduce some natural physical constraints. Furthermore, a compact neural network design and training method was developed to enable the training problem to fit within GPU memory constraints and a novel dataset was constructed from the output of a calibrated two-dimensional hydrodynamic model. A good correlation between the predicted and groundtruth water heights was observed. Full article

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Figure 1
Proposed ML inundation estimation system. Recursion is used to propagate forward through time. Full article ">Figure 2
Driving inflows for Baseline scenario (top left), Dry scenario (top right), Wet scenario (bottom left) and Topographic DEM data (bottom right) for modelling region. DG and MK markers provide location of Dimond Gorge and Mount Krauss inflows. Dashed line indicates when simulation starts after river fill initialization. Two large inflows are present around the 12 and 24 day marks. Full article ">Figure 3
Groundtruth water height and Inflow model prediction for 7 day baseline sequence (sampled daily) from the Mt. Krauss inflow region. Red indicates a water height <math display="inline"><semantics> <mrow> <mo>≥</mo> <mn>15</mn> </mrow> </semantics></math> m, blue is a water height of 0 m. Large flood event occurs around day 2 then gradually declines. Full article ">Figure 4
Time evolution of root mean squared error (left) and mean absolute error (right) for inundation models trained from scratch with 1 Hr, 6 Hr, 12 Hr and 24 Hr time-steps. In general, longer time-steps produced improved modelling performance. Full article ">Figure 5
Groundtruth water height (above) and 24 h Interior model prediction (below) for 7 day Baseline test sequence. Red indicates a water height <math display="inline"><semantics> <mrow> <mo>≥</mo> <mn>5</mn> </mrow> </semantics></math> m, blue is a water height of 0 m. A large flood event occurs around Day 1–2 then gradually declines. Full article ">

26 pages, 5548 KiB

Open AccessArticle

Pore-Scale Formation Characteristics of Impermeable Frozen Walls for Shallow Groundwater Contamination Remediation

by Yunfeng Zhang, Zhiqiang Zhao, Guantao Ding, Caiping Hu, Yuan Wang and Shuai Gao

Water 2024, 16(16), 2262; https://doi.org/10.3390/w16162262 (registering DOI) - 11 Aug 2024

Abstract

Impermeability and water blocking are crucial for remediating shallow groundwater contamination. Traditional methods often employ curtain-grouting technology to create impermeable layers. However, cement slurry curing is irreversible, leading to permanent closure of underground aquifers and secondary pollution. This study employs an innovative approach [...] Read more.

Impermeability and water blocking are crucial for remediating shallow groundwater contamination. Traditional methods often employ curtain-grouting technology to create impermeable layers. However, cement slurry curing is irreversible, leading to permanent closure of underground aquifers and secondary pollution. This study employs an innovative approach by fabricating cylindrical models that simulate actual strata and utilizing a high-temperature and high-pressure displacement device. It systematically analyzes the variations in soil pore structure, distribution, porosity, and permeability under different temperatures, pressures, and freezing durations. The microscopic characteristics of the freezing process in water-bearing soils were studied. Results demonstrate that longer freezing time improves the effectiveness of soil freezing, reaching complete freezing at temperatures as low as −4 °C for samples with low water content. For water-saturated samples, freezing below −6 °C results in nearly zero porosity. Increased pressure at a certain freezing temperature significantly reduces permeability. When freezing temperature falls below −4 °C, water permeability in saturated samples after freezing reaches near-zero levels, while unsaturated samples experience complete freezing. These findings provide a theoretical foundation for constructing freezing curtains in remediating shallow groundwater pollution. Full article

(This article belongs to the Section Hydrogeology)

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14 pages, 14651 KiB

Open AccessArticle

Effects of Fallen Posidonia Oceanica Seagrass Leaves on Wave Energy at Sandy Beaches

by Ogan Sevim and Emre N. Otay

Water 2024, 16(16), 2261; https://doi.org/10.3390/w16162261 (registering DOI) - 11 Aug 2024

Abstract

Posidonia Oceanica (PO) is an endemic marine plant in the Mediterranean Sea. In an experimental study conducted in the Eastern Mediterranean, the effects of natural PO leaves on reducing the height of incident waves impacting a beach were measured. The transmission coefficient ( [...] Read more.

Posidonia Oceanica (PO) is an endemic marine plant in the Mediterranean Sea. In an experimental study conducted in the Eastern Mediterranean, the effects of natural PO leaves on reducing the height of incident waves impacting a beach were measured. The transmission coefficient (K_t) was found to vary between 0.73 and 0.94, which is equivalent to a wave height decay of 6–27%. The results show that in their natural environment, free-floating dead PO leaves dissipate incoming wave energy and have the capacity to protect beaches against erosion. Further analysis in separate frequency bands showed that waves with periods between 4.5–6.2 s were more sensitive to PO leaves in terms of energy dissipation. The transmission coefficient for medium-period waves, calculated using the medium-frequency part of the wave spectrum, delivered a maximum transmission coefficient of 0.5, corresponding to a 50% decay in wave height due to PO leaves. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in Ocean Engineering)

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32 pages, 17629 KiB

Open AccessCase Report

Engineering Regulation of the Weird Branches in a Branching Estuary and its Mechanics: Using the North Branch of the Yangtze Estuary as an Example

by Dechao Hu, Zhanfeng Cui, Xin Zeng, Jianyin Zhou and Yuan Yuan

Water 2024, 16(16), 2260; https://doi.org/10.3390/w16162260 (registering DOI) - 11 Aug 2024

Abstract

Weird horizontal shapes of branches, in large branching estuaries, often cause significant flood risks and environment-related problems. People usually resort to engineering methods to improve the horizontal shape of the weird branches and solve related issues. The responses of the riverbed evolution of [...] Read more.

Weird horizontal shapes of branches, in large branching estuaries, often cause significant flood risks and environment-related problems. People usually resort to engineering methods to improve the horizontal shape of the weird branches and solve related issues. The responses of the riverbed evolution of a branching estuary to anthropogenic activity are complicated because of complex estuarine hydrodynamics and sediment transports, especially when the project locates specially (e.g., at estuary outlets). The North Branch of the Yangtze Estuary has a narrow upper reach which is almost orthogonal to the South Branch and has a trumpet-shaped lower reach with a wide outlet. The weird horizontal shape of the North Branch brings significant flood risks to cities along this branch, the shrinkage of its entrance, and other problems. In this study, a regulation of the North Branch, which is launched at Guyuan Sand (GYS) just outside the exit of the North Branch, is taken as an example. The GYS regulation aims to improve the weird horizontal shape of the North Branch by building new layouts of outlets, by which people decrease the flood risk of the surrounding cities. The GYS regulation is studied using a 2D numerical model. The riverbed evolution of the Yangtze Estuary in a typical hydrological year is simulated, while the water/sediment fluxes at cross-sections of branches in the estuary during a spring/neap tide are quantitatively calculated. It is found that the regulation changes the rotational flows near the shore, and further reshapes the estuarine circulations of mass inside the outlets, especially exchanges of water/sediment between different branches. The regulation directly changes the riverbed evolution at the outlet of the North Branch, and meanwhile has significant indirect influences on the riverbed evolution of the entrance of the North Branch. The varying riverbed evolution at the entrance of the North Branch and the varying water/sediment fluxes, under different designs of regulations, are related and analyzed. An essential improvement for the weird horizontal shape of the North Branch by an engineering method is shown to be possible, while the regulation mechanism of the engineering method and the response of estuarine riverbed evolution to the regulation are clarified. This study provides a new insight for improving estuarine branches with weird horizontal shapes, by reshaping the tidal processes and the accompanying sediment transports in a branching estuary. Full article

(This article belongs to the Special Issue Coast Sediment Dynamics: Historical Development, Current Situation and Perspectives)

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20 pages, 2907 KiB

Open AccessArticle

Image Influence on Concern about Stormwater Flooding: Exploratory Focus Groups

by Kristan Cockerill and Tanga Mohr

Water 2024, 16(16), 2259; https://doi.org/10.3390/w16162259 (registering DOI) - 11 Aug 2024

Abstract

Increased urbanization coupled with climate change is increasing the number and intensity of stormwater flooding events. Implementing efforts to successfully manage stormwater flooding depends on understanding how people perceive these events. While images of stormwater flooding abound, how these images influence perceptions about [...] Read more.

Increased urbanization coupled with climate change is increasing the number and intensity of stormwater flooding events. Implementing efforts to successfully manage stormwater flooding depends on understanding how people perceive these events. While images of stormwater flooding abound, how these images influence perceptions about flooding events or management options remains understudied. Our objective is to contribute to the general understanding of how various types of images depicting stormwater runoff and stormwater related flooding influence individual and group interpretations of causes of events, major impacts of those events, and responsibility for managing stormwater related events. To this end, we convened focus groups, gave participants numerous photos of stormwater flooding, asked them to identify which images were most concerning, and to then discuss the specific aspects of the photos that prompted concern. We also tested whether a priming image implicating climate change or development as a cause of stormwater flooding influenced viewer reactions. Finally, we asked participants about preferences for who should manage stormwater. Our results revealed that photo location, the water’s appearance, and what people were doing in the photo influenced levels of concern. We also found that priming seems to affect opinions regarding urban stormwater management. Finally, there is some evidence that the absence of people in the photo may affect beliefs about who should manage stormwater. Full article

(This article belongs to the Section Hydrology)

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Figure 1
The general project design. Full article ">Figure 2
Clockwise from upper left, photos N, P, U, S, from Boone, North Carolina represent the kinds of photos shown to focus group participants. Full article ">Figure 3
Photos and captions used to prime the focus groups. Photo sources: US Geological Survey (development) and US National Aeronautics and Space Administration (climate change). Full article ">Figure 4
Codes applied to focus group transcripts and used for analysis with total number of mentions included in parentheses. Full article ">Figure 5
Frequency of mentions in focus group discussions for each photo organized by climate change or development prime. Focus Group 3 mentioned all 12 photos in their scenario and is therefore excluded to provide a comparison. Full article ">Figure 6
(a) Proportion of participants who strongly agreed or agreed with statements about who should be responsible for managing stormwater, organized by the project scenarios 1, 2, and 3. (b) Proportion of participants who strongly agreed or agreed with statements about who should pay for stormwater management, organized by the project scenarios 1, 2, and 3. Full article ">

17 pages, 7508 KiB

Open AccessArticle

A Risk Assessment of the Vegetation Ecological Degradation in Hunshandake Sandy Land, China: A Case Study of Dabusennur Watershed

by Peng Chen, Rong Ma, Letian Si, Lefan Zhao, Ruirui Jiang and Wanggang Dong

Water 2024, 16(16), 2258; https://doi.org/10.3390/w16162258 (registering DOI) - 10 Aug 2024

Abstract

In the context of climate change, it is essential for sustainable development to assess the risks associated with climate change and human-induced vegetation degradation. The Hunshandake Sandy Land provides a variety of ecosystem services and is a substantial ecological security barrier in the [...] Read more.

In the context of climate change, it is essential for sustainable development to assess the risks associated with climate change and human-induced vegetation degradation. The Hunshandake Sandy Land provides a variety of ecosystem services and is a substantial ecological security barrier in the Beijing–Tianjin–Hebei area of China. This study used the Normalized Difference Vegetation Index (NDVI) to analyze the spatiotemporal variation trend in vegetation in the Dabusennur Watershed using linear trend analysis and the GeoDetector model to identify the main drivers of vegetation change in the watershed. Finally, the study assessed the risk of ecological degradation in the vegetation of the watershed. The results show that the NDVI in the study area has had a fluctuating trend in the last 22 years, and the change has been small. Precipitation and groundwater depth are the key factors affecting vegetation change. The NDVI reaches its maximum value when the groundwater depth is at 2.75 m. The vegetation ecology of the basin is relatively fragile, mainly with medium risk and large risk. To cope with the ecological risk of vegetation degradation caused by climate change, appropriate water use strategies should be formulated to ensure ecological water use. The present study’s outcomes provide the basis for developing ecological engineering solutions in the arid and semi-arid parts of northern China. Full article

(This article belongs to the Special Issue Soil and Groundwater Quality and Resources Assessment)

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13 pages, 2822 KiB

Open AccessArticle

Disinfection Efficacy and Eventual Harmful Effect of Chemical Peracetic Acid (PAA) and Probiotic Phaeobacter inhibens Tested on Isochrisys galbana (var. T-ISO) Cultures

by Elia Casoni, Gloria Contis, Leonardo Aguiari, Michele Mistri and Cristina Munari

Water 2024, 16(16), 2257; https://doi.org/10.3390/w16162257 (registering DOI) - 10 Aug 2024

Abstract

One of the main threats to aquaculture is represented by microbial pathogens, causing mass mortality episodes in hatcheries, which result in huge economic losses. Among the many disinfection methods applied to reduce this issue, the use of chemicals and beneficial microorganisms (probiotics) seems [...] Read more.

One of the main threats to aquaculture is represented by microbial pathogens, causing mass mortality episodes in hatcheries, which result in huge economic losses. Among the many disinfection methods applied to reduce this issue, the use of chemicals and beneficial microorganisms (probiotics) seems to be the most efficient. The aim of this study is to test the efficacy of two of them: a chemical, peracetic acid (PAA), and a probiotic, Phaeobacter inhibens. Tests were run on microalgae of the species Isochrysis galbana (var T-ISO). For both remedies, the microalgae survival rate and final cell concentration (cell/mL) were monitored. PAA analysis tested six different concentrations of the chemical: 7.5 µg, 10 µg/L, 20 µg/L, 30 µg/L, 40 µg/L, and 60 µg/L. Meanwhile, P. inhibens was tested with a concentration of 104 CFU/mL. Analysis for both the remedies was conducted on a laboratory scale using glass flasks, and on an industrial scale inside photobioreactors (PBRs). Among all the treatments, the one with PAA dosed with a concentration of 60 µg/L gave the best results, as the culture reached a final density of 8.61 × 10⁶ cell/mL. However, none of the remedies involved in the experiment harmed microalgae or their growth. The results match perfectly with the condition requested for the tested remedies: to obtain an optimal breakdown of pathogens without interfering with culture growth. These features make PAA and P. inhibens good candidates for disinfection methods in aquaculture facilities. Full article

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I. galbana growth expressed as 106 cell/mL (±SD) (left graphs) and relative pH variation (±SD) (right graphs) for every treatment tested in the laboratory trial involving PAA. Each graph shows the results of two treatments and the control group (CTRL): (a) 7.5 µg/L and 10 µg/L treatments; (b) 20 µg/L and 30 µg/L treatments; (c) 40 µg/L and 60 µg/L treatments. The trial lasted from T0 (0 h) to T2 (48 h). Full article ">Figure 2
I. galbana average specific growth rate (µ) related to every treatment tested in each trial, expressed as 106 cell/mL/h. (a) PAA laboratory trial: the blue square contains the treatments with µ values grouping under the 0.025 × 106 cell/mL/h threshold (bold horizontal line); the red square contains the µ values grouping above the 0.025 × 106 cell/mL/h. No statistical differences were detected among treatments. (b) P. inhibens laboratory trial. No statistical differences were detected among treatments. (c) PBR trial: different letters (“x”, “y”) indicate a significant statistical difference, according to Tukey’s HSD test (p-value < 0.05). Full article ">Figure 3
I. galbana growth related to the laboratory trial involving P. inhibens strain DSM17395, expressed as 106 cell/mL (±SD). The trial lasted from T0 (0 h) to T3 (72 h). Full article ">Figure 4
Growth curve and pH variation related to the PBR trial involving the 60 µg/L PAA treatment, P. inhibens treatment, and a control group. The results for cell growth are expressed as 106 cell/mL (±SD). The trial lasted from T0 (0 h) to T2 (48 h). Full article ">Figure 5
Rapid efficacy evaluation test results, to assess the presence/absence of pathogen bacteria belonging to genus Vibrio in cultures analyzed during the PBR trial: (a) PBR control group; (b) PBR treated with PAA; (c) PBR treated with probiotic P. inhibens. Full article ">

24 pages, 6188 KiB

Open AccessArticle

Optimal Coordinated Operation for Hydro–Wind Power System

by Huanhuan Li, Huiyang Jia, Zhiwang Zhang and Tian Lan

Water 2024, 16(16), 2256; https://doi.org/10.3390/w16162256 (registering DOI) - 10 Aug 2024

Abstract

The intermittent and stochastic characteristics of wind power pose a higher demand on the complementarity of hydropower. Studying the optimal coordinated operation of hydro–wind power systems has become an extremely effective way to create safe and efficient systems. This paper aims to study [...] Read more.

The intermittent and stochastic characteristics of wind power pose a higher demand on the complementarity of hydropower. Studying the optimal coordinated operation of hydro–wind power systems has become an extremely effective way to create safe and efficient systems. This paper aims to study the optimal coordinated operation of a hybrid power system based on a newly established Simulink model. The analysis of the optimal coordinated operation undergoes two simulation steps, including the optimization of the complementary mode and the optimization of capacity allocation. The method of multiple complementary indicators is adopted to enable the optimization analysis. The results from the complementary analysis show that the hydraulic tracing effect obviously mitigates operational risks and reduces power losses under adverse wind speeds. The results from the analysis of capacity allocation also show that the marginal permeation of installed wind capacity will not exceed 250 MW for a 100 MW hydropower plant under random wind speeds. These simulation results are obtained based on the consideration of some real application scenarios, which help power plants to make the optimal operation plan with a high efficiency of wind energy and high hydro flexibility. Full article

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

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20 pages, 4128 KiB

Open AccessArticle

The Role and Significance of Operational Flood Defense Plans on the Waters Second-Order in Republic of Serbia

by Aleksandar Drobnjak, Ratko Ristić and Nada Dragović

Water 2024, 16(16), 2255; https://doi.org/10.3390/w16162255 (registering DOI) - 10 Aug 2024

Abstract

The aim of this research is to present the role and importance of planning documents for flood defense during the development of the Flood Risk Management Plan (FRMP) in the Republic of Serbia. The scope of the work is the Operational Plans for [...] Read more.

The aim of this research is to present the role and importance of planning documents for flood defense during the development of the Flood Risk Management Plan (FRMP) in the Republic of Serbia. The scope of the work is the Operational Plans for Flood Defense on Second-Order Waters (OPFDSWs), which are the responsibility of local governments units (LGU). The paper contains an overview analysis of the implementation of the Flood Risk Management Directive (FRMD) in the legal framework of the Republic of Serbia, as well as an analysis of the legislative framework in the field of flood defense. The method of multi-criteria analysis was used for a qualitative assessment of the elements that are part of the OPFDSW. Through the results and discussion of the work, the similarities between the OPFDSW and FRMP were highlighted and explained, which can serve to better understand the importance of quality production of the OPFDSW. In order to harmonize all activities on the territory of LGU, care should be taken that planning documentation for flood protection occupies one of the priority activities in the management of planning acts. The conclusion is that it is necessary to clearly define the rulebook on the methodology for the preparation of the OPFDSW, all in the function of the preparation of the FRMP. Full article

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23 pages, 16349 KiB

Open AccessArticle

Enhancing Hydraulic Efficiency of Side Intakes Using Spur Dikes: A Case Study of Hemmat Water Intake, Iran

by Saman Abbasi Chenari, Hossein Azizi Nadian, Javad Ahadiyan, Mohammad Valipour, Giuseppe Oliveto and Seyed Mohsen Sajjadi

Water 2024, 16(16), 2254; https://doi.org/10.3390/w16162254 (registering DOI) - 9 Aug 2024

Abstract

This study investigates the problem of low efficiency and the lack of a water supply at the Hemmat Water Intake, in Iran, where severe sediment accumulation was observed at the intake mouth. The Flow-3D software was used to simulate the flow patterns under [...] Read more.

This study investigates the problem of low efficiency and the lack of a water supply at the Hemmat Water Intake, in Iran, where severe sediment accumulation was observed at the intake mouth. The Flow-3D software was used to simulate the flow patterns under various scenarios of hydraulic regimentation works. The considered parameters include: (i) three alternative locations of the spur dike (i.e., a spur dike placed on the opposite side of the intake inlet and aligned with the upstream edge of the intake, to be regarded as a witness spur dike; a spur dike at a distance D_S of 7 m downstream of the witness spur dike, which implies a dimensionless distance D_S/b_i₁ of 1/3, with b_i₁ being the intake opening width; and a spur dike at a distance of 7 m upstream of the witness spur dike with a dimensionless distance, still, of 1/3); (ii) four spur dike lengths, L_S/B_r, with L_S being the effective spur dike length and B_r the approach river width; and (iii) five spur dike deviation angles of 75, 90, 105, 120, and 135 degrees (the deviation angle is the angle between the spur dike axis and the original river-bank line from which the spur dike extends). The results showed that, with the increase in the relative spur dike length (L_S/B_r), the velocity of the flow entering the water intake increases by 11%. A spur deviation angle of 135 degrees increases the flow depth at the intake inlet by 9% compared to a smaller deviation angle of 75 degrees. In addition, the spur dike increases the flow shear stresses at the intake inlet by up to 50%. Overall, the main flow of the river with the highest velocity and depth, and best directed towards the water intake, occurs for the placement of the longest spur dike (i.e., L_S/B_r = 0.46) in front of the inlet (i.e., witness spur dike) and for a spur dike deviation angle of 135 degrees. The spur dike increases the shear stress at the intake entrance by more than five times with respect to the case of its absence. In general, the presence of a spur dike on the opposite bank and with a deviation angle in the direction of the intake inlet well directs the main flow towards the canal intake. Moreover, it reduces the possibility of sedimentation in the canal inlet by increasing the flow velocity. Therefore, the results of this study could also be useful in increasing the hydraulic efficiency of lateral intakes by reducing the sedimentation phenomena. Full article

(This article belongs to the Topic Research on River Engineering)

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20 pages, 4046 KiB

Open AccessArticle

Predicting Coastal Water Quality with Machine Learning, A Case Study of Beibu Gulf, China

by Yucai Bai, Zhefeng Xu, Wenlu Lan, Xiaoyan Peng, Yan Deng, Zhibiao Chen, Hao Xu, Zhijian Wang, Hui Xu, Xinglong Chen and Jinping Cheng

Water 2024, 16(16), 2253; https://doi.org/10.3390/w16162253 (registering DOI) - 9 Aug 2024

Abstract

Coastal ecosystems are facing critical water quality deterioration, while the most convenient passage to the South China Sea, Beibu Gulf, has been under considerable pressure to its ecological environment due to rapid development and urbanization. In this study, we characterized the spatiotemporal change [...] Read more.

Coastal ecosystems are facing critical water quality deterioration, while the most convenient passage to the South China Sea, Beibu Gulf, has been under considerable pressure to its ecological environment due to rapid development and urbanization. In this study, we characterized the spatiotemporal change in the water quality in Beibu Gulf and proposed a machine learning approach to predict the water pollution level in Beibu Gulf on the basis of 5-year (2018–2022) observation data of ten water quality parameters from ten selected sites. Random forest (rf) and linear algorithms were utilized. Results show that a high frequency of exceedance of water quality parameters was observed particularly in summer and autumn, e.g., the exceeding rate of Dissolved Inorganic Nitrogen (DIN) at GX01, GX03, GX06, and GX07 station were 28.2~78.1% (average is 52.0%), 6.0~21.7% (average is 52.0%), 23.0~44.7% (average is 31.9%), and 5.2~33.4% (average is 21.2%), respectively. With regard to the spatial distribution, the pH, Water Salinity (WS), and Dissolved Oxygen (DO) values of stations inside the bay were overall lower than those of corresponding stations at the mouth of the bay and stations outside the bay. The concentrations of Chlorophyll-a concentration (except QZB) and nutrient salts showed a clearly opposite trend compared with the above concerned three parameters. For instance, the average Chl-a value of station GX09 was 22.5% higher than that of GX08 and GX10 between 2018 and 2022. Correlation analysis among water quality factors shows a significant positive correlation (r > 0.85) between Dissolved Inorganic Nitrogen (DIN) and NO₃-N, followed by NO₂-N and NH₄-N, indicating that the main component of DIN is NO₃-N. The forecasting results with machine learning also demonstrate the possibility to estimate the water quality parameters, such as chl-a concentration, DIN, and NH₄-N in a cost-effective manner with prediction accuracy of approximately 60%, and thereby could provide near-real-time information to monitor the water quality of the Beibu Gulf. Predicting models initiated in this study could be of great interest for local authorities and the tourism and fishing industries. Full article

(This article belongs to the Section Oceans and Coastal Zones)

15 pages, 6318 KiB

Open AccessArticle

An Assessment of the Embedding of Francis Turbines for Pumped Hydraulic Energy Storage

by Georgi Todorov, Ivan Kralov, Konstantin Kamberov, Evtim Zahariev, Yavor Sofronov and Blagovest Zlatev

Water 2024, 16(16), 2252; https://doi.org/10.3390/w16162252 (registering DOI) - 9 Aug 2024

Abstract

In this paper, analyses of Francis turbine failures for powerful Pumped Hydraulic Energy Storage (PHES) are conducted. The structure is part of PHES Chaira, Bulgaria (HA4—Hydro-Aggregate 4). The aim of the study is to assess the structure-to-concrete embedding to determine the possible causes [...] Read more.

In this paper, analyses of Francis turbine failures for powerful Pumped Hydraulic Energy Storage (PHES) are conducted. The structure is part of PHES Chaira, Bulgaria (HA4—Hydro-Aggregate 4). The aim of the study is to assess the structure-to-concrete embedding to determine the possible causes of damage and destruction of the HA4 Francis spiral casing units. The embedding methods that have been applied in practice for decades are discussed and compared to those used for HA4. A virtual prototype is built based on the finite-element method to clarify the influence of workloads under the generator mode. The stages of the simulation include structural analysis of the spiral casing and concrete under load in generator mode, as well as structural analysis of the spiral casing under loads in generator mode without concrete. Both simulations are of major importance. Since the failure of the surface between the turbine, the spiral casing, and the concrete is observed, the effect of the growing contact gap (no contact) is analyzed. The stresses, strains, and displacements of the turbine units are simulated, followed by an analysis for reliability. The conclusions reveal the possible reasons for cracks and destruction in the main elements of the structure. Full article

(This article belongs to the Special Issue Hydraulic Engineering and Numerical Simulation of Two-Phase Flows)

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17 pages, 6630 KiB

Open AccessArticle

Interpreting Controls of Stomatal Conductance across Different Vegetation Types via Machine Learning

by Runjia Xue, Wenjun Zuo, Zhaowen Zheng, Qin Han, Jingyan Shi, Yao Zhang, Jianxiu Qiu, Sheng Wang, Yan Zhu, Weixing Cao and Xiaohu Zhang

Water 2024, 16(16), 2251; https://doi.org/10.3390/w16162251 - 9 Aug 2024

Abstract

Plant stomata regulate transpiration (T) and CO₂ assimilation, essential for the water–carbon cycle. Quantifying how environmental factors influence stomatal conductance will provide a scientific basis for understanding the vegetation–atmosphere water–carbon exchange process and water use strategies. Based on eddy covariance [...] Read more.

Plant stomata regulate transpiration (T) and CO₂ assimilation, essential for the water–carbon cycle. Quantifying how environmental factors influence stomatal conductance will provide a scientific basis for understanding the vegetation–atmosphere water–carbon exchange process and water use strategies. Based on eddy covariance and hydro-metrological observations from FLUXNET sites with four plant functional types and using three widely applied methods to estimate ecosystem T from eddy covariance data, namely uWUE, Perez-Priego, and TEA, we quantified the regulation effect of environmental factors on canopy stomatal conductance (G_s). The environmental factors considered here include radiation (net radiation and solar radiation), water (soil moisture, relative air humidity, and vapor pressure deficit), temperature (air temperature), and atmospheric conditions (CO₂ concentration and wind speed). Our findings reveal variation in the influence of these factors on G_s across biomes, with air temperature, relative humidity, soil water content, and net radiation being consistently significant. Wind speed had the least influence. Incorporating the leaf area index into a Random Forest model to account for vegetation phenology significantly improved model accuracy (R² increased from 0.663 to 0.799). These insights enhance our understanding of the primary factors influencing stomatal conductance, contributing to a broader knowledge of vegetation physiology and ecosystem functioning. Full article

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Locations of the study sites. Full article ">Figure 2
Histogram of the importance of Gs characteristics at each site. The y-axis starts at −0.5 because the importance and error bars exceed 0 for some sites, and the negative y indicates that the feature hurts the RF prediction results. Full article ">Figure 2 Cont.
Histogram of the importance of Gs characteristics at each site. The y-axis starts at −0.5 because the importance and error bars exceed 0 for some sites, and the negative y indicates that the feature hurts the RF prediction results. Full article ">Figure 3
Model accuracy of before (Benchmark) and after adding LAI (LAI). The darker colors in the panels correspond to higher values. (a) presents R2 results for the training set, while (b) displays R2 results for the test set. (c) shows RMSE outcomes for the training set, and (d) outlines RMSE results for the test set. Full article ">Figure A1
Histogram of the importance of Gs characteristics at each site (adding LAI). The y-axis starts at −0.5 because the importance and error bars exceed 0 for some sites, and the negative y indicates that the feature hurts the RF prediction results. Full article ">Figure A1 Cont.
Histogram of the importance of Gs characteristics at each site (adding LAI). The y-axis starts at −0.5 because the importance and error bars exceed 0 for some sites, and the negative y indicates that the feature hurts the RF prediction results. Full article ">

22 pages, 1210 KiB

Open AccessReview

Water Poverty Index over the Past Two Decades: A Comprehensive Review and Future Prospects—The Middle East as a Case Study

by Ashraf Isayed, Juan M. Menendez-Aguado, Hatem Jemmali and Nidal Mahmoud

Water 2024, 16(16), 2250; https://doi.org/10.3390/w16162250 - 9 Aug 2024

Abstract

This paper summarises the evolution of the Water Poverty Index (WPI) application at different scales since its emergence. The review captures the main milestones and remarkable developments around the world. It sets the foundation for identifying the most appropriate version of the WPI, [...] Read more.

This paper summarises the evolution of the Water Poverty Index (WPI) application at different scales since its emergence. The review captures the main milestones and remarkable developments around the world. It sets the foundation for identifying the most appropriate version of the WPI, building on learning from previous versions. In addition, the paper sheds light on the linkages between the WPI and sustainable development goals and applications to fragile contexts. Therefore, it provides a synthesis of knowledge researchers and practitioners’ need in sustainable water resources management that helps boost human development in unstable/fragile arid and semi-arid contexts. The methodology included (i) WPI literature shortlisting and reviewing, (ii) review literature links WPI with sustainable human development and fragility, and (iii) data analysis, identification of gaps and future trends. Intensive research was found to address the limitations of the WPI. However, further research is needed to shortlist the multiple versions of the WPI and match them to their respective scale, purpose and context (including fragile contexts). In addition, a time-based WPI was rarely touched to forecast the impact of decisions on community welfare. Full article

(This article belongs to the Special Issue Water Management in Arid and Semi-arid Regions)

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17 pages, 9774 KiB

Open AccessArticle

New Insights into Changes in DOM Fractions in a Crab Farming Park and Key Factors in the Removal Process Using Fluorescence Spectra with MW-2DCOS and SEM

by Ruijuan Zhou, Yan Hao, Benxin Yu, Junwen Hou, Kuotian Lu, Fang Yang and Qingqian Li

Water 2024, 16(16), 2249; https://doi.org/10.3390/w16162249 - 9 Aug 2024

Abstract

With the explosion of crab farming in China, the urgent need to treat crab wastewater can never be overemphasized. Hence, in this study, excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC), moving window two-dimensional correlation spectroscopy (MW-2DCOS) and structural equation modeling [...] Read more.

With the explosion of crab farming in China, the urgent need to treat crab wastewater can never be overemphasized. Hence, in this study, excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC), moving window two-dimensional correlation spectroscopy (MW-2DCOS) and structural equation modeling (SEM) were employed to identify changes in the dissolved organic matter (DOM) fractions in a crab farming park and reveal latent factors associated with removal processes. Seven components (C1–C7) were extracted from DOMs by EEM-PARAFAC as follows: C1: microbial byproduct-like substances, C2: visible-tryptophan-like substances, C3: fulvic-like substances, C4: phenolic-like substances, C5: ultraviolet tyrosine-like substances, C6: D-tryptophan-like substances and C7: L-tryptophan-like substances. Interestingly, C7 (39.20%), a representative component of DOM in the crab farming pond, was deeply degraded in the aeration pond by aerobic microbes, whereas C6 was absent in the crab pond. According to 2DCOS, the changing order of the components was C7 → C4 → C6 → C5 → C2 → C1 → C3, and the changing order of the functional groups was carboxylic → phenolic → aromatic. As assessed by MW-2DCOS, the Fmax of the components, especially components C2, C5 and C6 (and with the exception of C4 and C7) exponentially increased in the aeration pond, where an accumulative effect occurred. C2, C5 and C7 were removed by 24.26%, 39.42% and 98.25% in the crab farming system, and were deeply degraded in the paddy-field, purification pond and aeration pond, respectively. As assessed by SEM, the latent factors of organic matter removal were C1, C2, C4, C5, SUVA254, COD_Mn and DO. This study could be conducive to comprehensively characterizing the removal of components and functional groups of DOMs in crab farming parks. Full article

(This article belongs to the Special Issue Water Environment Pollution and Control, Volume III)

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28 pages, 10501 KiB

Open AccessArticle

Hydrological Monitoring System of the Navío-Quebrado Coastal Lagoon (Colombia): A Very Low-Cost, High-Value, Replicable, Semi-Participatory Solution with Preliminary Results

by Andrea Gianni Cristoforo Nardini, Jairo R. Escobar Villanueva and Jhonny I. Pérez-Montiel

Water 2024, 16(16), 2248; https://doi.org/10.3390/w16162248 - 9 Aug 2024

Abstract

Like many coastal lagoons in several countries, the “Navío Quebrado” lagoon (La Guajira, Colombia) is a very delicate and precious environment; indeed, it is a nationally recognized Flora and Fauna Sanctuary. Several factors, including climate change, are threatening its existence because of changes [...] Read more.

Like many coastal lagoons in several countries, the “Navío Quebrado” lagoon (La Guajira, Colombia) is a very delicate and precious environment; indeed, it is a nationally recognized Flora and Fauna Sanctuary. Several factors, including climate change, are threatening its existence because of changes in the governing hydro-morphological and biological processes. Certainly, the first step to addressing this problem is to understand its hydrological behavior and to be able to replicate, via simulation, its recent history before inferring likely futures. These potential futures will be marked by changes in the water input by its tributary, the Camarones River, and by modified water exchange with the sea, according to a foreseen sea level rise pattern, as well as by a different evaporation rate from the free surface, according to temperature changes. In order to achieve the required ability to simulate future scenarios, data on the actual behavior have to be gathered, i.e., a monitoring system has to be set up, which to date is non-existent. Conceptually, designing a suitable monitoring system is not a complex issue and seems easy to implement. However, the environmental, socio-cultural, and socio-economic context makes every little step a hard climb. An extremely simple—almost “primitive”—monitoring system has been set up in this case, which is based on very basic measurements of river flow velocity and water levels (river, lagoon, and sea) and the direct participation of local stakeholders, the most important of which is the National Park unit of the Sanctuary. All this may clash with the latest groovy advances of science, such as in situ automatized sensors, remote sensing, machine learning, and digital twins, and several improvements are certainly possible and desirable. However, it has a strong positive point: it provides surprisingly reasonable data and operates at almost zero additional cost. Several technical difficulties made this exercise interesting and worthy of being shared. Its novelty lies in showing how old, simple methods may offer a working solution to new challenges. This humble experience may be of help in several other similar situations across the world. Full article

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

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25 pages, 12790 KiB

Open AccessArticle

Numerical Simulation Study on Three-Dimensional Flow Characteristics and Probability Density Distribution of Water-Permeable Gabion Backflow Zone in Different Curvature Bends

by Peng Xie, Suiju Lv, Zelin Li, Ying Zhang and Jianping Lv

Water 2024, 16(16), 2247; https://doi.org/10.3390/w16162247 - 9 Aug 2024

Abstract

This study explored the three-dimensional flow characteristics in a recirculation zone near a permeable buttress in curved channels with varying curvatures. Understanding these characteristics is crucial for managing natural river bends, as rivers often meander, with backwater zones formed behind obstructions, such as [...] Read more.

This study explored the three-dimensional flow characteristics in a recirculation zone near a permeable buttress in curved channels with varying curvatures. Understanding these characteristics is crucial for managing natural river bends, as rivers often meander, with backwater zones formed behind obstructions, such as mountains in the riverbed. The direct comparison of the recirculation zones across different bend types revealed the correlation between the flow characteristics and bend curvature. However, previous studies have focused on flow velocities and turbulent kinetic energy without a probability density analysis. This analysis provided a more comprehensive understanding of the flow characteristics. Gaussian kernel density estimation was applied in this study to observe the distribution of the flow velocities, turbulent kinetic energy, and turbulent kinetic energy dissipation rate. The results indicated that the longitudinal time-averaged flow velocity in the recirculation zone typically ranged from −0.2 m/s to −0.8 m/s, with all the skewness coefficients exceeding 0. The horizontal time-averaged flow velocity in the recirculation zone fell between −0.175 m/s and −0.1 m/s. The skewness coefficients were negative at water depths of 16%, 33%, and 50% within the 90° and 180° bends, indicating a non-normal distribution. The probability density distribution of turbulent kinetic energy in the recirculation zone was skewed, ranging from 0 to 0.02 m²·s⁻², with the skewness coefficient almost always greater than 0. The plot demonstrated multiple peaks, indicating a broad distribution of turbulent kinetic energy rather than a concentration within a specific interval. This distribution included both the high and low regions of turbulent kinetic energy. Although the overall rate of turbulent kinetic energy dissipation in the recirculation zone was relatively low, there were multiple peaks, suggesting the localized areas with higher dissipation rates alongside the regions with lower rates. These findings were significant for managing the meandering river channels, restoring the subaqueous ecosystems, understanding the pollutant diffusion mechanisms in backwater areas, the sedimentation of nutrient-laden sediments, and optimizing the parameters for spur dike design. Full article

(This article belongs to the Special Issue Mathematical Models of Fluid Dynamics)

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14 pages, 4368 KiB

Open AccessArticle

The Relationship between Ribosomal RNA Operon Copy Number and Ecological Characteristics of Activated Sludge Microbial Communities across China

by Jiaying Li, Yunwei Zhao, Ruisi Ye, Jingyue Zhang, Qianhui Chen, Ting Yang, Tan Chen and Bing Zhang

Water 2024, 16(16), 2246; https://doi.org/10.3390/w16162246 - 9 Aug 2024

Abstract

It is well accepted that the high performance of wastewater treatment plants (WWTPs) relies on the microbial community in activated sludge (AS). Hence, it is crucial to illuminate the geographic distributions and influencing factors of the ecological strategies employed by the AS microbial [...] Read more.

It is well accepted that the high performance of wastewater treatment plants (WWTPs) relies on the microbial community in activated sludge (AS). Hence, it is crucial to illuminate the geographic distributions and influencing factors of the ecological strategies employed by the AS microbial community. Here, we investigated how the ecological strategies of AS microbial communities influenced their ecological characteristics in 60 WWTPs across 15 cities in China. Our study showed that the average rrn copy number of the whole AS microbial community across China was 2.25 ± 0.12. The highest average rrn copy number of the core community indicated that core members tend to be r-strategists with an advantage in rapid pollutant removal and recovery of the community after environmental disturbances. High nutrient availability promoted microorganisms with higher average rrn copy numbers, while long sludge retention time (SRT) was preferred to the microorganisms with lower average rrn copy numbers. Homogenous selection and dispersal limitation were the predominant assembling processes at the city level, with a shift from deterministic to stochastic processes with increasing average rrn copy numbers. Furthermore, more r-strategists participated in chemoheterotrophic functions, while more K-strategists were related to the nitrification processes. Overall, our findings enrich the knowledge of AS microbial ecology and lay the theoretical foundation for the precise regulation of WWTPs. Full article

(This article belongs to the Special Issue Wastewater Pollution and Control)

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Geographic distributions of sampled cities across China. Full article ">Figure 2
Average rrn copy numbers of the whole, core, rare, and abundant communities (** indicates P < 0.01; *** indicates P < 0.001; ◆ indicates outliers). Full article ">Figure 3
Comparison of the whole, core, rare, and abundant average rrn copy numbers and intra-group differences among 15 cities (* indicates P < 0.05; ** indicates P < 0.01; *** indicates P < 0.001). Full article ">Figure 4
Spearman correlation analysis of copy number and environmental factors in four groups. NH3, F/M, TN, and COD loading describe the nutrient level of AS, while Inf.COD, Inf.BOD, and Inf.TN characterize the nutrient level of the influent wastewater (* indicates P < 0.05; ** indicates P < 0.01; *** indicates P < 0.001; black lines indicate cluster analysis). Full article ">Figure 5
Correlation analysis (Pearson correlation) between the average rrn copy number of the whole microbial community and (a–c) taxonomic and (d–f) phylogenetic α diversity. q0 represents microbial richness, q1 represents Shannon–Wiener Index, and q2 represents inverse Simpson index (Red line indicates linear fit). Full article ">Figure 6
Relative contributions of (a) each assembling process and (b) the deterministic and stochastic processes of the whole AS microbial community at the city level. Full article ">Figure 7
Relationship between the (a) deterministic process and (b) stochastic process and the average rrn copy number of the three groups (Blue line indicates linear fit). Full article ">Figure 8
Relationships (Spearman correlation) between average rrn copy numbers: (a) the whole microbial communities, (b) the core community, (c) the rare community, and (d). the abundant community and their corresponding predicted functions based on FAPROTAX. Full article ">

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