Water

15 pages, 2318 KiB

Open AccessEditor’s ChoiceReview

The Importance of Nonconventional Water Resources under Water Scarcity

by Andreas N. Angelakis, George Tchobanoglous, Andrea G. Capodaglio and Vasileios A. Tzanakakis

Water 2024, 16(7), 1015; https://doi.org/10.3390/w16071015 - 31 Mar 2024

Cited by 11 | Viewed by 3843

According to FAO, water scarcity is now affecting all five continents and is expected to intensify in the coming years as the water demands of the growing population increase and the impacts of climate variability become more pronounced. The existing unevenness of water [...] Read more.

According to FAO, water scarcity is now affecting all five continents and is expected to intensify in the coming years as the water demands of the growing population increase and the impacts of climate variability become more pronounced. The existing unevenness of water resource availability and insufficient investment in relevant infrastructure have forced the water sector to recognize the importance of nonconventional water resources (NWR) in planning for a sustainable water future. The purpose of this review is to highlight the available and potentially available NWR and to discuss the future application of these water sources. Full article

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13 pages, 3336 KiB

Open AccessEditor’s ChoiceArticle

Spatial Variations in Microplastics in the Largest Shallow Lake of Central Europe and Its Protecting Wetland Area

by Bence Prikler, Réka Svigruha, Judit Háhn, Péter Harkai, István Fodor, Edit Kaszab, Balázs Kriszt, Gergő Tóth, István Szabó, Zsolt Csenki, Gábor Bordós, Adrienn Micsinai, Brigitta Nyírő-Fekete, Zoltán Palotai, Zsófia Lovász, Zsolt Pirger and Sándor Szoboszlay

Water 2024, 16(7), 1014; https://doi.org/10.3390/w16071014 - 31 Mar 2024

Cited by 4 | Viewed by 1918

Abstract

The concentration of microplastics (MPs) in two important Hungarian freshwater habitats was determined in the size range of 50 μm–1 mm. Lake Balaton (LB) is the largest shallow lake in Central Europe, with a significant role in recreation and tourism. Its main inflow, [...] Read more.

The concentration of microplastics (MPs) in two important Hungarian freshwater habitats was determined in the size range of 50 μm–1 mm. Lake Balaton (LB) is the largest shallow lake in Central Europe, with a significant role in recreation and tourism. Its main inflow, the Zala River, enters the lake through an artificially constructed wetland, the Kis-Balaton Water Protection System and its catchment area (KB), which helps preserve the water quality of the lake. From these two areas, 15 samples were taken with an in situ filtration sampling method. After preparation, the samples were analyzed automatically by FT-IR microscopy. All samples, from both areas, contained MPs; the dominant microplastic (MP) shape was the fragment, while the most frequently polymer types were polyethylene, polypropylene and alkyd. Small MPs were dominant in both areas; around 90% of the MPs were smaller than 500 μm. On average, LB contained more MPs (21.0 ± 12.5 MPs/m³) compared to the KB, which presented an average concentration of MPs of 7.8 ± 5.9 MPs/m³. In the examined areas, two potential MP sources were determined, i.e., treated wastewater and road traffic. The importance of tourism should also be further investigated. Full article

(This article belongs to the Special Issue Contaminants in the Water Environment)

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13 pages, 3655 KiB

Open AccessEditor’s ChoiceArticle

Pollution Assessment and Spatial Distribution of Heavy Metals in Surface Waters and Bottom Sediments of the Krzna River (Poland)

by Mariusz Kluska and Joanna Jabłońska

Water 2024, 16(7), 1008; https://doi.org/10.3390/w16071008 - 30 Mar 2024

Cited by 5 | Viewed by 1534

Abstract

Due to their toxicity, lack of bioaccumulation and biodegradability, and ease of binding to sediments, heavy metals are considered the main pollutants of rivers. It is, therefore, necessary to control and monitor these pollutants. The present study analyzed the Krzna River, which flows [...] Read more.

Due to their toxicity, lack of bioaccumulation and biodegradability, and ease of binding to sediments, heavy metals are considered the main pollutants of rivers. It is, therefore, necessary to control and monitor these pollutants. The present study analyzed the Krzna River, which flows in southeastern Poland and has an outlet to the Bug River. Over much of its length, the Bug River forms Poland’s border with Belarus, while its origin is in Ukraine. The main purpose of the conducted research was a qualitative and quantitative analysis of selected heavy metals, i.e., Ni, Pb, Zn, Cd, and Cu, in bottom sediments and surface waters of the Krzna River. The secondary objectives were to evaluate the level of contamination of the studied matrices and identify the sources of pollution. Eighty samples of water and bottom sediments from the Krzna River were collected for the analysis. Due to the varying distribution of metals under the influence of changes in temperature, precipitation, and humidity, the samples were collected in May and August 2023. The average cadmium content in the sediments studied was the same in both May and August, at 0.6 mg/kg. In contrast, the nickel content of the sediments ranged from 4.6 to 6.1 mg/kg in May and from 4.8 to 6.8 in August. Only nickel and cadmium of the five heavy metals tested were present in amounts exceeding the geochemical background value. Analysis of the results indicates that only a minimal amount of heavy metals remain dissolved in the surface waters, and the remainder contaminates the sediments. The average concentrations of metals in the studied bottom sediments and surface waters were as follows: zinc > lead > nickel > copper > cadmium. The content of metals in the studied sediments was not high, but at the same time, their presence above the geochemical background indicates anthropogenic human activity. Any changes in hydrodynamic conditions and various environmental factors may result in the re-release of heavy metals contained in sediments into surface waters. Full article

(This article belongs to the Section Soil and Water)

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17 pages, 4630 KiB

Open AccessEditor’s ChoiceArticle

Temporal and Spatial Characteristics of Agricultural Drought Based on the TVDI in Henan Province, China

by Yanbin Li, Xin Wang, Fei Wang, Kai Feng, Hongxing Li, Yuhang Han and Shaodan Chen

Water 2024, 16(7), 1010; https://doi.org/10.3390/w16071010 - 30 Mar 2024

Cited by 5 | Viewed by 1561

Abstract

As a major grain-producing province in China’s Central Plains, Henan Province is severely impacted by drought, making the study of agricultural drought characteristics in the region crucial. Theil–Sen (Sen) trend analysis, the Mann–Kendall (M-K) test and the Hurst index method were used to [...] Read more.

As a major grain-producing province in China’s Central Plains, Henan Province is severely impacted by drought, making the study of agricultural drought characteristics in the region crucial. Theil–Sen (Sen) trend analysis, the Mann–Kendall (M-K) test and the Hurst index method were used to systematically analyze the spatial variation characteristics of agricultural drought based on the Temperature Vegetation Dryness Index (TVDI). The results show that: (1) The drought occurs in central, northwestern and southern Henan on an annual scale. The drought situation will continue to increase in northern, eastern northeastern and central Henan. (2) The drought in spring, summer and winter showed an increasing trend, but the opposite trend was observed in autumn. The increasing trend of drought in each season is mainly distributed in northern, central and eastern Henan. (3) The drought in January, February, April, July, September and December showed an increasing trend, while the drought in the other 6 months showed a decreasing trend. The increase in drought during July and August was not pronounced, while the drought situation in September remained largely unchanged. The distribution of drought across the other months exhibited varying patterns across different regions. Overall, the drought trend in Henan Province is on the rise, displaying distinct seasonal and regional patterns in its temporal and spatial distribution. The results can provide a reference for Henan Province to formulate effective measures of drought resistance and disaster reduction to ensure grain production. Full article

(This article belongs to the Special Issue Drought Monitoring and Risk Assessment)

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23 pages, 980 KiB

Open AccessEditor’s ChoiceReview

Process Waters from Hydrothermal Carbonization of Waste Biomasses like Sewage Sludge: Challenges, Legal Aspects, and Opportunities in EU and Germany

by Tommy Ender, Vicky Shettigondahalli Ekanthalu, Haniyeh Jalalipour, Jan Sprafke and Michael Nelles

Water 2024, 16(7), 1003; https://doi.org/10.3390/w16071003 - 29 Mar 2024

Cited by 5 | Viewed by 2610

Abstract

Hydrothermal carbonization (HTC) has developed considerably over the last 15 years and offers a viable alternative for the utilization of municipal and industrial organic waste such as sewage sludge. However, the technology has yet to establish itself as a valorization process for waste [...] Read more.

Hydrothermal carbonization (HTC) has developed considerably over the last 15 years and offers a viable alternative for the utilization of municipal and industrial organic waste such as sewage sludge. However, the technology has yet to establish itself as a valorization process for waste biomasses (2024) and is not yet a recognized state of the art. Nevertheless, the HTC technology could gain greater relevance in the future, especially as an alternative valorization pathway for sewage sludge. During HTC, significant amounts of HTC process water (PW) are produced as a byproduct. The process water is inorganically and organically polluted and has to be treated, as it would be a burden on water bodies and thus on the environment if left untreated. In the EU and specifically Germany, industrial wastewater producers like HTC-plant operators are obliged to treat their industrial wastewater before discharging it into the environment. In addition to a large amount of PW and its treatment to the required limits, the organic load and possible persistent and toxic substances pose major challenges for plant operators. Many proven processes from industrial wastewater treatment were transferred for the treatment of PW. Treatment of the PW in a manner that is industrially viable, economically viable, and efficient is crucial for the effective commercialization of HTC technology. In this, the challenges and opportunities of PW composition, management, and treatment, including legal aspects, are mainly discussed. Therefore, the legal framework in the European Union and specifically for Germany will be elaborated. Furthermore, different treatment pathways are also highlighted. Full article

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

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26 pages, 9512 KiB

Open AccessEditor’s ChoiceArticle

Post-Analysis of Daniel Extreme Flood Event in Thessaly, Central Greece: Practical Lessons and the Value of State-of-the-Art Water-Monitoring Networks

by Elias Dimitriou, Andreas Efstratiadis, Ioanna Zotou, Anastasios Papadopoulos, Theano Iliopoulou, Georgia-Konstantina Sakki, Katerina Mazi, Evangelos Rozos, Antonios Koukouvinos, Antonis D. Koussis, Nikos Mamassis and Demetris Koutsoyiannis

Water 2024, 16(7), 980; https://doi.org/10.3390/w16070980 - 28 Mar 2024

Cited by 20 | Viewed by 5053

Abstract

Storm Daniel initiated on 3 September 2023, over the Northeastern Aegean Sea, causing extreme rainfall levels for the following four days, reaching an average of about 360 mm over the Peneus basin, in Thessaly, Central Greece. This event led to extensive floods, with [...] Read more.

Storm Daniel initiated on 3 September 2023, over the Northeastern Aegean Sea, causing extreme rainfall levels for the following four days, reaching an average of about 360 mm over the Peneus basin, in Thessaly, Central Greece. This event led to extensive floods, with 17 human lives lost and devastating environmental and economic impacts. The automatic water-monitoring network of the HIMIOFoTS National Research Infrastructure captured the evolution of the phenomenon and the relevant hydrometeorological (rainfall, water stage, and discharge) measurements were used to analyse the event’s characteristics. The results indicate that the average rainfall’s return period was up to 150 years, the peak flow close to the river mouth reached approximately 1950 m³/s, and the outflow volume of water to the sea was 1670 hm³. The analysis of the observed hydrographs across Peneus also provided useful lessons from the flood-engineering perspective regarding key modelling assumptions and the role of upstream retentions. Therefore, extending and supporting the operation of the HIMIOFoTS infrastructure is crucial to assist responsible authorities and local communities in reducing potential damages and increasing the socioeconomic resilience to natural disasters, as well as to improve the existing knowledge with respect to extreme flood-simulation approaches. Full article

(This article belongs to the Topic Application of Smart Technologies in Water Resources Management)

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23 pages, 5738 KiB

Open AccessEditor’s ChoiceArticle

Socio-Economic Indicators for Water Management in the South-West Europe Territory: Sectorial Water Productivity and Intensity in Employment

by Beatriz Larraz, Noelia García-Rubio, Matías Gámez, Sabine Sauvage, Roxelane Cakir, Mélanie Raimonet and José Miguel Sánchez Pérez

Water 2024, 16(7), 959; https://doi.org/10.3390/w16070959 - 26 Mar 2024

Cited by 6 | Viewed by 1697

Abstract

Given the need for water use to be a crucial consideration in sustainable development, an adequate water allocation system across economic sectors is essential, especially in the face of increasing seasonal and perennial water scarcity. In an attempt to facilitate a socially and [...] Read more.

Given the need for water use to be a crucial consideration in sustainable development, an adequate water allocation system across economic sectors is essential, especially in the face of increasing seasonal and perennial water scarcity. In an attempt to facilitate a socially and economically efficient adaptation to the climate emergency, we propose a set of eleven socio-economic indicators to analyze the current water management. This set of indicators could help to quantify the interrelationship between water use and its economic perspective, as well as its social perspective through its impact on employment. Any demand for water not only includes the direct use of water but also its indirect use, referred to as virtual water. This is the water indirectly used through the other inputs in the production process (input–output methodology). These indicators are evaluated in the South-West Europe territory where, in light of increasing water scarcity, there is a need to orientate water allocation toward employment with less intensive water use, to more water productivity and to less environmental impacts. The results at river basin scales show that water use is more productive in the tertiary than in the secondary and primary sectors. Full article

(This article belongs to the Section Urban Water Management)

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24 pages, 2086 KiB

Open AccessEditor’s ChoiceReview

Biological Treatment of Nitroaromatics in Wastewater

by Swati Gupta and Zeev Ronen

Water 2024, 16(6), 901; https://doi.org/10.3390/w16060901 - 20 Mar 2024

Cited by 7 | Viewed by 2515

Abstract

Nitroaromatic compounds (NACs), which are widely used in pesticides, explosives, dyes, and pharmaceuticals, include nitrobenzene, nitrotoluenes, nitrophenols, and nitrobenzoates. They are also significant industrial pollutants in the environment. These substances, as well as their derivatives, frequently have toxic or mutagenic properties. Wastewater containing [...] Read more.

Nitroaromatic compounds (NACs), which are widely used in pesticides, explosives, dyes, and pharmaceuticals, include nitrobenzene, nitrotoluenes, nitrophenols, and nitrobenzoates. They are also significant industrial pollutants in the environment. These substances, as well as their derivatives, frequently have toxic or mutagenic properties. Wastewater containing nitroaromatic compounds can be effectively managed by using biological treatment methods that are accessible, cost-effective, and environmentally friendly. This review highlights the latest developments in biological treatment systems for removing NACs from wastewater. The large-scale implementation of biological treatment systems will be facilitated by future studies that focus on identifying the best operational methods and that determine how co-pollutants impact the removal of NACs from wastewater. Full article

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

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13 pages, 7368 KiB

Open AccessEditor’s ChoiceArticle

Immobilization of Horseradish Peroxidase and Myoglobin Using Sodium Alginate for Treating Organic Pollutants

by Xinyu Wang, Hossein Ghanizadeh, Shoaib Khan, Xiaodan Wu, Haowei Li, Samreen Sadiq, Jiayin Liu, Huimin Liu and Qunfeng Yue

Water 2024, 16(6), 848; https://doi.org/10.3390/w16060848 - 15 Mar 2024

Cited by 9 | Viewed by 2113

Abstract

Removing organic pollutants from wastewater is crucial to prevent environmental contamination and protect human health. Immobilized enzymes are increasingly being explored for wastewater treatment due to their specific catalytic activities, reusability, and stability under various environmental conditions. Peroxidases, such as horseradish peroxidase (HRP) [...] Read more.

Removing organic pollutants from wastewater is crucial to prevent environmental contamination and protect human health. Immobilized enzymes are increasingly being explored for wastewater treatment due to their specific catalytic activities, reusability, and stability under various environmental conditions. Peroxidases, such as horseradish peroxidase (HRP) and myoglobin (Mb), are promising candidates for immobilized enzymes utilized in wastewater treatment due to their ability to facilitate the oxidation process of a wide range of organic molecules. However, the properties of the carrier and support materials greatly influence the stability and activity of immobilized HRP and Mb. In this research, we developed immobilized HRP and Mb using support material composed of sodium alginate and CaCl₂ as carriers and glutaraldehyde as a crosslinking agent. Following this, the efficacy of immobilized HRP and Mb in removing aniline, phenol, and p-nitrophenol was assessed. Both immobilized enzymes removed all three organic pollutants from an aqueous solution, but Mb was more effective than HRP. After being immobilized, both enzymes became more resilient to changes in temperature and pH. Both immobilized enzymes retained their ability to eliminate organic pollutants through eight treatment cycles. Our study uncovered novel immobilized enzyme microspheres and demonstrated their successful application in wastewater treatment, paving the way for future research. Full article

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

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20 pages, 2317 KiB

Open AccessEditor’s ChoiceArticle

How Environmental Regulation Affects Rural Residents’ Willingness to Pay for Sustainable Domestic Sewage Treatment: Mediating and Interaction Effects

by Jian Jiao, Zihong Yang, Boyang Shi, Thomas Dogot, Hossein Azadi, Ke Xu and Changbin Yin

Water 2024, 16(5), 761; https://doi.org/10.3390/w16050761 - 2 Mar 2024

Cited by 5 | Viewed by 1977

Abstract

Exploring the construction of effective payment mechanisms for rural residents could break the dilemma of the value of a single investment by the government in environmental governance and promote the process of sustainable rural domestic sewage treatment (RDST). The effects of environmental regulations [...] Read more.

Exploring the construction of effective payment mechanisms for rural residents could break the dilemma of the value of a single investment by the government in environmental governance and promote the process of sustainable rural domestic sewage treatment (RDST). The effects of environmental regulations have been roughly approved; however, their influence mechanisms on rural residents’ willingness to pay (WTP) and payment level for sustainable RDST have not been fully revealed. Based on a database of 744 respondents, an integrated model was developed to verify the heterogeneous effects of three environmental regulations on rural residents’ WTP and further explore their interaction effects and impact mechanisms. In addition, there is an urgent necessity to explore the effectiveness of implementing different combinations of environmental regulations. Our results indicated that, firstly, the guiding regulation and incentive regulation promoted rural residents’ WTP and payment level, whereas the binding regulation had a limited impact on individuals. Secondly, rural residents’ cognition mediated the effect of the environmental regulations on their WTP and payment level. Lastly, the guiding and incentive regulations showed a substitution relationship, while both guiding and binding regulations as well as incentive and binding regulations revealed a complementary relationship. The implications of these results indicate the importance of strengthening the public attention on the environmental and health hazards of rural domestic sewage and effectively raising rural residents’ environmental cognition and environmental protection awareness, thereby increasing their WTP and payment level for sustainable RDST. This study provides credible references and recommendations for environmental regulations’ formulation and policy optimization for RDST, as well as for the construction of payment systems for rural residents, and inspiration for rural environment management in other developing countries. Full article

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

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19 pages, 543 KiB

Open AccessEditor’s ChoiceArticle

Decolonizing Indigenous Drinking Water Challenges and Implications: Focusing on Indigenous Water Governance and Sovereignty

by Margot Hurlbert, John Bosco Acharibasam, Ranjan Datta, Sharon Strongarm and Ethel Starblanket

Water 2024, 16(5), 748; https://doi.org/10.3390/w16050748 - 1 Mar 2024

Cited by 7 | Viewed by 8523

Abstract

Indigenous Peoples in Canada have shown great strength and resilience in maintaining their cultures and ways of life to date in the face of settler colonialism. Centering the Water crises within Indigenous sovereignty and self-determination, we explore the impacts these crises have on [...] Read more.

Indigenous Peoples in Canada have shown great strength and resilience in maintaining their cultures and ways of life to date in the face of settler colonialism. Centering the Water crises within Indigenous sovereignty and self-determination, we explore the impacts these crises have on community members. Particularly, the continuous failure of the Canadian government to end the Water crises in remote Indigenous communities, Star Blanket Cree Nation, is investigated in this paper. What implications have these Water governance gaps had on Indigenous Peoples’ sovereignty and self-determination? We adopted an Indigenist theoretical framework to guide the study. Additionally, a community-based participatory research approach was adopted. To achieve our research goals of investigating the implications of the current Water crises for Indigenous sovereignty and self-determination, specific methods of sharing circles were used to gather knowledge from community members, Elders, and knowledge keepers. The research findings strongly highlight the strength and resilience shown by remote Indigenous communities in the face of the current Water crises and continuous government failure. Solving the current Water crises will involve remote Indigenous communities taking charge of their own Water governance through Indigenous-led Water governance systems. Additionally, taking steps to rebuild trust through genuine reconciliation will be key. Therefore, listening to remote Indigenous communities and taking collaborative action are fundamental. Full article

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

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24 pages, 6231 KiB

Open AccessEditor’s ChoiceArticle

Removal of Chromium (VI) from Water Using Orange peel as the Biosorbent: Experimental, Modeling, and Kinetic Studies on Adsorption Isotherms and Chemical Structure

by Amel Khalfaoui, Abderrezzaq Benalia, Zineb Selama, Amira Hammoud, Kerroum Derbal, Antonio Panico and Antonio Pizzi

Water 2024, 16(5), 742; https://doi.org/10.3390/w16050742 - 29 Feb 2024

Cited by 12 | Viewed by 2814

Abstract

The present work aims to assess the effectiveness and efficiency of orange peels as a low-cost biosorbent for removing Cr(VI) from an aqueous solution by the biosorbent process. The orange peels as adsorbent was characterized using different methods, such as FTIR, pH_pzc [...] Read more.

The present work aims to assess the effectiveness and efficiency of orange peels as a low-cost biosorbent for removing Cr(VI) from an aqueous solution by the biosorbent process. The orange peels as adsorbent was characterized using different methods, such as FTIR, pH_pzc, equilibrium pH, TGA, XRD, SEM, and (BET). The tests were conducted in the batch mode, and the effects of different parameters, such as the pH, dosage of the bioadsorbent, influent Cr(VI), and time, on the biosorption of Cr(VI) were investigated. The adsorption kinetics proved that a contact time of 90 min resulted in the highest (approximately 97.8%) Cr(VI) removal, with an adsorption capacity of 4.96 mg/g. Moreover, the increase in the biosorbent dosage (from 1 to 10 g/L) resulted in the enhancement in the Cr(VI) removal effectiveness. Moreover, the pH of the solution also affected significantly the effectiveness of the removal. The tests were conducted under acidic pH solution conditions, and the prediction of the pH value at a zero charge (pH _pzc) was confirmed experimentally. Furthermore, the results from the batch-mode assays were successfully tested by an experimental design (full factorial design). The biosorption of Cr(VI) on orange peels occurred mostly according to the pseudo-second-order kinetic model and the uptake of Cr(VI) was satisfactorily described by the Langmuir model. Full article

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

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17 pages, 5357 KiB

Open AccessEditor’s ChoiceArticle

Using the Heavy Metal Indices and Benthic Indices to Assess the Ecological Quality in the Tidal Flats of Garolim Bay, South Korea

by Jian Liang, Hai-Rui Huang, Chae-Woo Ma, Dae-Sun Son and Seon-Kyu Kim

Water 2024, 16(5), 736; https://doi.org/10.3390/w16050736 - 29 Feb 2024

Cited by 8 | Viewed by 1892

Abstract

During economic growth, anthropogenic activities have exerted detrimental impacts on the tidal flat ecosystems in South Korea. Although scholars have conducted extensive research on the ecological quality of tidal flats in South Korea, most have primarily focused on benthic indices. Hence, we utilised [...] Read more.

During economic growth, anthropogenic activities have exerted detrimental impacts on the tidal flat ecosystems in South Korea. Although scholars have conducted extensive research on the ecological quality of tidal flats in South Korea, most have primarily focused on benthic indices. Hence, we utilised two heavy metal indices and five benthic indices to assess the ecological quality in the tidal flats comprehensively. In our study, although heavy metals and total organic carbon concentrations were low in Garolim Bay, the final ecological quality at most stations was unacceptable (63%). The Benthic Opportunistic Polychaetes Amphipods Index (BOPA) demonstrated commendable outcomes in correlation and kappa analyses. However, the BOPA still had some limits. We believe that using multiple indices to assess the ecological quality in the tidal flats of Garolim Bay is more robust than using a single index. Full article

(This article belongs to the Special Issue Source, Occurrence, Pathway, and Fate of Heavy Metals in the Water Environment)

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20 pages, 4109 KiB

Open AccessEditor’s ChoiceArticle

Dissolved Oxygen Forecasting for Lake Erie’s Central Basin Using Hybrid Long Short-Term Memory and Gated Recurrent Unit Networks

by Daiwei Pan, Yue Zhang, Ying Deng, Jesse Van Griensven Thé, Simon X. Yang and Bahram Gharabaghi

Water 2024, 16(5), 707; https://doi.org/10.3390/w16050707 - 28 Feb 2024

Cited by 7 | Viewed by 1872

Abstract

Dissolved oxygen (DO) concentration is a pivotal determinant of water quality in freshwater lake ecosystems. However, rapid population growth and discharge of polluted wastewater, urban stormwater runoff, and agricultural non-point source pollution runoff have triggered a significant decline in DO levels in Lake [...] Read more.

Dissolved oxygen (DO) concentration is a pivotal determinant of water quality in freshwater lake ecosystems. However, rapid population growth and discharge of polluted wastewater, urban stormwater runoff, and agricultural non-point source pollution runoff have triggered a significant decline in DO levels in Lake Erie and other freshwater lakes located in populated temperate regions of the globe. Over eleven million people rely on Lake Erie, which has been adversely impacted by anthropogenic stressors resulting in deficient DO concentrations near the bottom of Lake Erie’s Central Basin for extended periods. In the past, hybrid long short-term memory (LSTM) models have been successfully used for the time-series forecasting of water quality in rivers and ponds. However, the prediction errors tend to grow significantly with the forecasting period. Therefore, this research aimed to improve the accuracy of DO forecasting models by taking advantage of Lake Erie’s real-time water quality (water temperature and DO concentration) monitoring network to establish temporal and spatial links between adjacent monitoring stations. We developed hybrid LSTM models that combine LSTM, convolutional neuron network LSTM (CNN-LSTM), hybrid CNN with gated recurrent unit (CNN-GRU) models, and convolutional LSTM (ConvLSTM) to forecast near-bottom DO concentrations in Lake Erie’s Central Basin. These hybrid LSTM models improve their capacity to handle complicated datasets with spatial and temporal variability. These models can serve as accurate and reliable tools for forecasting DO concentrations in freshwater lakes to help environmental protection agencies better access and manage the health of these vital ecosystems. Following analysis of a 21-site Lake Erie dataset for 2020 and 2021, the ConvLSTM model emerged as the most accurate and reliable, boasting an MSE of 0.51 mg/L, MAE of 0.42 mg/L, and an R-squared of 0.95 over the 12 h prediction range. The model foresees future hypoxia in Lake Erie. Notably, the temperature near site 713 holds significance for Central Basin DO forecasting in Lake Erie, as indicated by outcomes derived from the Shapley additive explanations (SHAP). Full article

(This article belongs to the Special Issue Water Quality, Ecological Health and Ecosystem Restoration)

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15 pages, 2888 KiB

Open AccessEditor’s ChoiceArticle

Effects of Freeze–Thaw Cycles on Soil Nitrogen Transformation in Improved Saline Soils from an Irrigated Area in Northeast China

by Siyu Nie, Xian Jia, Yuanchun Zou and Jianmin Bian

Water 2024, 16(5), 653; https://doi.org/10.3390/w16050653 - 23 Feb 2024

Cited by 5 | Viewed by 1988

Abstract

Freeze–thaw cycles (FTCs) occur during the nongrowing season, and residual nitrogen (N) increases the risk of N loss with melting water. To study the effect of FTCs on soil N, rice fields in improved irrigated saline soil in northeast China were selected as [...] Read more.

Freeze–thaw cycles (FTCs) occur during the nongrowing season, and residual nitrogen (N) increases the risk of N loss with melting water. To study the effect of FTCs on soil N, rice fields in improved irrigated saline soil in northeast China were selected as the research subjects. Water content (10%, 20%, and 30%), different N fertilizer levels (180 and 220 kg/ha), and multiple FTCs of soil samples were used to clarify the effects of N fertilizer application and water content on N efficiency. The results indicate that, after the third FTC, the soil ammonium nitrogen (NH₄⁺-N) level increased significantly. NH₄⁺-N increased with an increase in the initial soil moisture content and decreased with fertilizer levels. Nitrate nitrogen (NO₃⁻-N) decreases with increasing initial soil moisture. The inorganic N increased significantly compared with that in the unfrozen stage, indicating that FTCs promote soil N mineralization. However, high fertilization rates inhibit mineralization. Analysis of variance showed that NO₃⁻-N is sensitive to the N application rate, water content, and salinity (p < 0.05). FTCs and artificial fertilization are the factors that affect N mineralization (p < 0.05). The research results are significant for preventing nitrate leaching and soil acidification during spring plowing and providing a scientific basis for fertilization systems and water environment pollution in improved saline soils. Full article

(This article belongs to the Special Issue Study of the Soil Water Movement in Irrigated Agriculture III)

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18 pages, 2134 KiB

Open AccessEditor’s ChoiceReview

Trees in Sponge Cities—A Systematic Review of Trees as a Component of Blue-Green Infrastructure, Vegetation Engineering Principles, and Stormwater Management

by Michael Richter, Kirya Heinemann, Nadine Meiser and Wolfgang Dickhaut

Water 2024, 16(5), 655; https://doi.org/10.3390/w16050655 - 23 Feb 2024

Cited by 9 | Viewed by 3510

Abstract

Combining street trees with stormwater management measures can, in some circumstances, both increase tree vitality and reduce the risk of flooding by directing stormwater into tree pits. Using systematic review methods, this study aimed to provide an overview of the vegetation engineering systems [...] Read more.

Combining street trees with stormwater management measures can, in some circumstances, both increase tree vitality and reduce the risk of flooding by directing stormwater into tree pits. Using systematic review methods, this study aimed to provide an overview of the vegetation engineering systems being researched and applied that combine tree planting with urban stormwater management. We also sought to identify the positive as well as possible negative impacts on urban hydrology and tree health. It has been shown that diverting rainwater from impervious surfaces into tree pits has considerable potential for stormwater management and for improving tree health by reducing drought stress in urban trees. Worldwide approaches to optimizing tree pits for rainwater infiltration and water supply are promising. Different systems and substrate types have been tested, and street trees generally show good vitality, although systematic long-term monitoring of tree vitality has rarely been undertaken. There is still a need for research into temporary water storage for dry periods. Full article

(This article belongs to the Special Issue Review Papers of Urban Water Management 2023)

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23 pages, 16173 KiB

Open AccessEditor’s ChoiceArticle

Surrogate-Based Uncertainty Analysis for Groundwater Contaminant Transport in a Chromium Residue Site Located in Southern China

by Yanhong Zou, Muhammad Shahzad Yousaf, Fuqiang Yang, Hao Deng and Yong He

Water 2024, 16(5), 638; https://doi.org/10.3390/w16050638 - 21 Feb 2024

Cited by 5 | Viewed by 2474

Abstract

Numerical modeling is widely acknowledged as a highly precise method for understanding the dynamics of contaminant transport in groundwater. However, due to the intricate characteristics of environmental systems and the lack of accurate information, the results are susceptible to a significant degree of [...] Read more.

Numerical modeling is widely acknowledged as a highly precise method for understanding the dynamics of contaminant transport in groundwater. However, due to the intricate characteristics of environmental systems and the lack of accurate information, the results are susceptible to a significant degree of uncertainty. Numerical models must explicitly consider related uncertainties in parameters to facilitate robust decision-making. In a Chromium Residue Site located in southern China (the study area), this study employed Monte Carlo simulation to assess the impact of variability in key parameters uncertainty on the simulation outcomes. Variogram analysis of response surface (VARS), global sensitivity analysis, and an XGBoost (version 2.0.0)-based surrogate model was employed to overcome the substantial computational cost of Monte Carlo simulation. The results of numerical simulation indicate that the contaminant is spreading downstream towards the northern boundary of contaminated site near Lianshui River, threatening water quality. Furthermore, migration patterns are complex due to both downstream convection and upstream diffusion. Sensitivity analysis identified hydraulic conductivity, recharge rate, and porosity as the most influential model parameters, selected as key parameters. Moreover, uncertainty analysis indicated that the variability in key parameters has a minimal impact on the simulation outcomes at monitoring wells near the contaminant source. In contrast, at wells positioned a considerable distance from the contaminant source, the variability in key parameters significantly influences the simulation outcomes. The surrogate model markedly mitigated computational workload and calculation time, while demonstrating superior precision and effectively capture the non-linear correlations between input and output of the simulation model. Full article

(This article belongs to the Special Issue Contaminant Transport Modeling in Aquatic Environments)

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19 pages, 7514 KiB

Open AccessEditor’s ChoiceArticle

Assessing Changes in Exceptional Rainfall in Portugal Using ERA5-Land Reanalysis Data (1981/1982–2022/2023)

by Luis Angel Espinosa, Maria Manuela Portela and Salem Gharbia

Water 2024, 16(5), 628; https://doi.org/10.3390/w16050628 - 20 Feb 2024

Cited by 6 | Viewed by 2576

Abstract

This research examines the intricate changes in the number of occurrences and cumulative rainfall of exceptional events in Portugal spanning 42 hydrological years (from 1981/1982 to 2022/2023). The study has two primary objectives: assessing the hydrological spatial dynamics of a region susceptible to [...] Read more.

This research examines the intricate changes in the number of occurrences and cumulative rainfall of exceptional events in Portugal spanning 42 hydrological years (from 1981/1982 to 2022/2023). The study has two primary objectives: assessing the hydrological spatial dynamics of a region susceptible to climate-induced variations in exceptional rainfall and evaluating the proficiency of a ERA5-Land reanalysis rainfall dataset in capturing exceptional rainfall. Confronting methodological and data-related challenges (e.g., incomplete record series), the investigation uses continuous daily ERA5-Land rainfall series. Validation against the Sistema Nacional de Informação de Recursos Hídricos (SNIRH) and the Portuguese Institute for Sea and Atmosphere (IPMA) ensures the reliability of ERA5-Land data. Empirical non-exceedance probability curves reveal a broad consensus between reanalysis data and observational records, establishing the dataset’s suitability for subsequent analysis. Spatial representations of occurrences, cumulative rainfall, and rainfall intensity of events above thresholds throughout the overall 42-year period and two subperiods (late: 1981/1982–2001/2002; and recent: 2002/2003–2022/2023) are presented, illustrating spatial and temporal variations. A noteworthy shift in the spatial distribution of intense events from south to north is observed, emphasising the dynamism of such hydrological processes. The study introduces a novel dimension with a severity heat map, combining some key findings from the occurrences and cumulative rainfall through subperiods. This study significantly contributes to the understanding of hydrological dynamics in Portugal, providing valuable insights for risk management and the development of sustainable strategies tailored to the evolving patterns of exceptional rainfall. Full article

(This article belongs to the Special Issue Climate and Water: Impacts of Climate Change on Hydrological Processes and Water Resources)

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30 pages, 410 KiB

Open AccessEditor’s ChoiceReview

Challenges to Water Resource Management: The Role of Economic and Modeling Approaches

by Ariel Dinar

Water 2024, 16(4), 610; https://doi.org/10.3390/w16040610 - 18 Feb 2024

Cited by 22 | Viewed by 12970

Abstract

The field of water management is continually changing. Water has been subject to external shocks in the form of climate change and globalization. Water management analysis is subject to disciplinary developments and inter-disciplinary interactions. Are these developments well-documented in the literature? Initial observations [...] Read more.

The field of water management is continually changing. Water has been subject to external shocks in the form of climate change and globalization. Water management analysis is subject to disciplinary developments and inter-disciplinary interactions. Are these developments well-documented in the literature? Initial observations in the interdisciplinary literature suggest that results are fragmented, implying that a state-of-the-art review is needed. This paper aims to close such a gap by reviewing recent developments in water economics that address increasing perceptions of water scarcity by looking first at changes in the supply and quality of water and then at the impacts of climate change on water supply extremes. Among responses to such challenges, this paper identifies changes to water use patterns by including and co-managing water from different sources, including surface and groundwater, reclaimed wastewater, and desalinated water. Technological advancements are also among the resources that address water challenges. Water challenges are also reflected in the management of internationally shared water. A recent surge in scientific work identified international treaties as a significant contributor to international water management. This paper reviews recently employed economic approaches, such as experimental economics, game theory, institutional economics, and valuation methods. And, finally, it explores modeling approaches, including hydro-economic and computable general equilibrium models, that are being used to deal with water challenges. Full article

17 pages, 53660 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Hydrological Responses to Land Use and Land Cover Changes in Forest-Dominated Watershed Using SWAT Model

by Hiyaw Hatiya Ware, Sun Woo Chang, Jeong Eun Lee and Il-Moon Chung

Water 2024, 16(4), 528; https://doi.org/10.3390/w16040528 - 7 Feb 2024

Cited by 6 | Viewed by 3306

Abstract

Recognizing how human activities affect hydrological systems is vital for the sustainable preservation and effective management of water resources in the watershed. Hence, this paper focuses on the hydrological response to land use and land cover (LULC) change scenarios in the Anyang watershed, [...] Read more.

Recognizing how human activities affect hydrological systems is vital for the sustainable preservation and effective management of water resources in the watershed. Hence, this paper focuses on the hydrological response to land use and land cover (LULC) change scenarios in the Anyang watershed, South Korea. We obtained LULC data maps for the years 2000, 2013, and 2022 from the local government, revealing significant changes over the years. Agricultural lands experienced a 6.2% increase from 2000 to 2022, and pastureland expanded by 8.67% over two decades. The SWAT model was utilized to assess the impact of LULC on the hydrological components of the study watershed. Model calibration and validation for each LULC change were carried out using the SWAT-CUP program, considering the recorded streamflow information of the region. An excellent agreement was reached between the simulated and measured streamflow in both the calibration and validation stages under various LULC conditions. The Nash–Sutcliffe model efficiency (NSE), the objective function, demonstrated values of 0.9, 0.89, and 0.89 during the calibration for 2000, 2013, and 2022, respectively, in the LULC scenario, while for the validation, we obtained values of 0.82, 0.78, and 0.80 for 2000, 2013, and 2022, respectively. Our findings indicate that the surface runoff rise contributed much to the water yield increase over the two decades compared to the other components in terms of the water yield, while the contribution of evapotranspiration (ET) to the watershed hydrological cycle declined by 1.66% from 2000 to 2022. The southeastern sub-basin part showed a high groundwater recharge distribution due to agricultural land, rice area, and forest area changes. Full article

(This article belongs to the Special Issue Novel Applications of Surface Water–Groundwater Modeling—2nd Edition)

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20 pages, 5765 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Propagation of Meteorological Drought to Groundwater Drought: A Case Study of the North China Plain

by Yuyin Chen, Yongqiang Zhang, Jing Tian, Zixuan Tang, Longhao Wang and Xuening Yang

Water 2024, 16(3), 501; https://doi.org/10.3390/w16030501 - 4 Feb 2024

Cited by 7 | Viewed by 2610

Abstract

As extreme climate events become more common with global warming, groundwater is increasingly vital for combating long-term drought and ensuring socio-economic and ecological stability. Currently, the mechanism of meteorological drought propagation to groundwater drought is still not fully understood. This study focuses on [...] Read more.

As extreme climate events become more common with global warming, groundwater is increasingly vital for combating long-term drought and ensuring socio-economic and ecological stability. Currently, the mechanism of meteorological drought propagation to groundwater drought is still not fully understood. This study focuses on the North China Plain (NCP), utilizing statistical theories, spatiotemporal kriging interpolation, and the Mann–Kendall trend test to examine the spatial and temporal distribution characteristics of groundwater from 2005 to 2021. Based on drought theory, the characteristics and propagation process of drought are further quantified. Key findings reveal the following: (1) Shallow groundwater depths in the NCP follow a zonal pattern from the western mountains to the eastern plains and coastal areas. Over two-thirds of this region showed an increase in groundwater depth at a rate of 0–0.05 m/a; (2) Groundwater drought frequency typically ranges from 3 to 6 times, with an average duration of 10 to 30 months and average severity between 10 and 35; (3) Delayed effects last between 0 to 60 months, with attenuation effects varying from 0 to 3 and prolonged effects extending from 0 to 16. Additionally, delayed effects intensify with increasing time scales, while prolonged effects weaken. Notably, both delayed and prolonged effects in the north of the NCP are more pronounced than in the south of the region. This study quantifies the process by which meteorological drought propagates to groundwater drought, offering a new perspective for understanding the interaction between groundwater and meteorological drought. It holds significant scientific importance for monitoring drought and managing water resources in the context of global climate change. Full article

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

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17 pages, 992 KiB

Open AccessEditor’s ChoiceArticle

Reuse of Treated Wastewater for Crop Irrigation: Water Suitability, Fertilization Potential, and Impact on Selected Soil Physicochemical Properties

by Solomon Ofori, David Kwesi Abebrese, Iveta Růžičková and Jiří Wanner

Water 2024, 16(3), 484; https://doi.org/10.3390/w16030484 - 1 Feb 2024

Cited by 13 | Viewed by 4462

Abstract

This study evaluates the suitability of treated wastewater (TWW: secondary effluent and membrane effluent) for crop irrigation and the resultant impact on crop growth and soil physicochemical characteristics. Carrot seeds (Daucus carota subsp. sativus) were grown on loam soil and irrigated [...] Read more.

This study evaluates the suitability of treated wastewater (TWW: secondary effluent and membrane effluent) for crop irrigation and the resultant impact on crop growth and soil physicochemical characteristics. Carrot seeds (Daucus carota subsp. sativus) were grown on loam soil and irrigated with tap water (Tap), secondary effluent (SE), and membrane effluent (ME) until maturity. Bacteriological analyses showed four log counts of E. coli and thermotolerant coliforms for secondary effluent, making it unsafe for the irrigation of carrots. Tap water and membrane effluent fulfilled the microbial limit for water reuse and were suitable for irrigation. The sodium absorption ratio, Kelly index, and magnesium hazard assessments indicated that all three irrigation water streams were suitable for irrigation. The average mass of carrot fruits for Tap, SE, and ME was 2.14 g, 3.96 g, and 3.03 g, respectively. A similar trend was observed for the dry matter composition: Tap had 15.9%, SE had 18.3%, and ME had 16.6%. The soil pH increased from 7.08 to 7.26, 7.39, and 7.33 for tap water-, secondary effluent-, and membrane effluent-irrigated soils, respectively. Nitrate-nitrogen and potassium levels increased in the TWW-irrigated soil, while that of the tap water-irrigated soil decreased. Sodium levels in the TWW-irrigated soil increased significantly but did not induce soil sodicity. The application of the TWW enhanced the growth of the carrot plants and increased the soil nutrient levels. Hence, using TWW in agricultural irrigation could promote food production and also limit the overdependency on freshwater resources. However, TWW should be disinfected by using UV disinfection and ozonation to reduce the risk of microbial contamination. Such disinfection methods may not lead to the formation of toxic byproducts, and therefore secondary pollution to crops is not anticipated. Full article

(This article belongs to the Special Issue Driving Water Reuse by New Technologies, Land Use and Infrastructure Planning, and Legislation Policies)

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26 pages, 1130 KiB

Open AccessEditor’s ChoiceReview

Research on Water Resource Modeling Based on Machine Learning Technologies

by Ze Liu, Jingzhao Zhou, Xiaoyang Yang, Zechuan Zhao and Yang Lv

Water 2024, 16(3), 472; https://doi.org/10.3390/w16030472 - 31 Jan 2024

Cited by 13 | Viewed by 6090

Abstract

Water resource modeling is an important means of studying the distribution, change, utilization, and management of water resources. By establishing various models, water resources can be quantitatively described and predicted, providing a scientific basis for water resource management, protection, and planning. Traditional hydrological [...] Read more.

Water resource modeling is an important means of studying the distribution, change, utilization, and management of water resources. By establishing various models, water resources can be quantitatively described and predicted, providing a scientific basis for water resource management, protection, and planning. Traditional hydrological observation methods, often reliant on experience and statistical methods, are time-consuming and labor-intensive, frequently resulting in predictions of limited accuracy. However, machine learning technologies enhance the efficiency and sustainability of water resource modeling by analyzing extensive hydrogeological data, thereby improving predictions and optimizing water resource utilization and allocation. This review investigates the application of machine learning for predicting various aspects, including precipitation, flood, runoff, soil moisture, evapotranspiration, groundwater level, and water quality. It provides a detailed summary of various algorithms, examines their technical strengths and weaknesses, and discusses their potential applications in water resource modeling. Finally, this paper anticipates future development trends in the application of machine learning to water resource modeling. Full article

(This article belongs to the Special Issue Application of Machine Learning to Water Resource Modeling)

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17 pages, 3146 KiB

Open AccessEditor’s ChoiceArticle

Estimation of Energy Consumption and CO₂ Emissions of the Water Supply Sector: A Seoul Metropolitan City (SMC) Case Study

by Li Li, Gyumin Lee and Doosun Kang

Water 2024, 16(3), 479; https://doi.org/10.3390/w16030479 - 31 Jan 2024

Cited by 4 | Viewed by 1937

Abstract

A model that computes the per-unit process energy consumption, energy intensity, CO₂ emission, and CO₂ intensity of water treatment plants is developed. This model is used to estimate the total energy consumption of six water treatment plants in Seoul Metropolitan City [...] Read more.

A model that computes the per-unit process energy consumption, energy intensity, CO₂ emission, and CO₂ intensity of water treatment plants is developed. This model is used to estimate the total energy consumption of six water treatment plants in Seoul Metropolitan City (SMC), which is comprised 80–85% for finished water pumping, 6–10% for ozone disinfection, 2–4% for rapid mixing, and 1–3% for non-process loads. The model results are validated against actual data for 2020 and 2021. The net energy consumption considering renewable energy production and use is then calculated, and the corresponding level of CO₂ emissions is predicted. Four scenarios based on the projected water requirements for the year 2045 were evaluated as follows: increased energy efficiency in finished water pumping (Scenario 1), increased renewable energy production in water treatment plants (Scenario 2), increased energy efficiency in raw water pumping (Scenario 3), and reduced water supply per capita (Scenario 4). Compared to a baseline do-nothing scenario (Scenario 0), the net energy consumption is reduced by 3.57%, 2.61%, 3.42%, and 4.67% for Scenarios 1–4, respectively. Scenario 4, which is a water-driven approach, is best for reducing CO₂ emissions, while Scenario 1 and 3, which are energy-driven approaches, are more effective at reducing CO₂ intensity. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Planning of Water-Energy Nexus under Climate Change)

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22 pages, 523 KiB

Open AccessEditor’s ChoiceReview

Natural Organic Matter Character in Drinking Water Distribution Systems: A Review of Impacts on Water Quality and Characterization Techniques

by Ammar Riyadh and Nicolas M. Peleato

Water 2024, 16(3), 446; https://doi.org/10.3390/w16030446 - 30 Jan 2024

Cited by 13 | Viewed by 4673

Abstract

Natural Organic Matter (NOM) in water arises from decomposed plant and animal matter and is ubiquitous in drinking water sources. The variation in NOM concentrations and characteristics, influenced by events like floods and droughts, plays a crucial role in water treatment efficiency and [...] Read more.

Natural Organic Matter (NOM) in water arises from decomposed plant and animal matter and is ubiquitous in drinking water sources. The variation in NOM concentrations and characteristics, influenced by events like floods and droughts, plays a crucial role in water treatment efficiency and water quality received by the public. For example, increased NOM concentrations necessitate higher levels of coagulants and disinfectants, leads to the formation of disinfection by-products (DBPs), and plays a key role in biofilm development. When considering impacts of NOM, it is not only the presence or concentration but the makeup or proportion of varying sub-groups which can impact water quality. Formation of DBPs, corrosion and scaling, pollutant transport, aesthetic deterioration, and biofilm growth are dependent on the relative composition of NOM within the distribution system. Although the role of NOM concentration and characteristics is well studied during treatment, the impacts of residual NOM in water distribution systems have received less attention. In particular, it is clear, due to the varying roles of NOM sub-groups, that greater consideration of NOM characteristics in distribution systems is needed. This paper reviews the broad implications of NOM characteristics for water distribution systems and explores challenges and opportunities in NOM characterization within distribution systems. Furthermore, the influence of NOM characteristics in premise plumbing is examined. The review highlights the necessity for precise NOM characterization and real-time monitoring, aiming to strengthen water distribution system resilience. Full article

(This article belongs to the Special Issue Monitoring and Assessment of Water Quality in Drinking Water Distribution Systems)

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20 pages, 8866 KiB

Open AccessEditor’s ChoiceArticle

Laboratory Investigation on the Hydrodynamic Response of a Draft Varying Floating Breakwater (and Wave Energy Converter)

by Sara Russo, Pasquale Contestabile, Diego Vicinanza and Claudio Lugni

Water 2024, 16(3), 445; https://doi.org/10.3390/w16030445 - 29 Jan 2024

Cited by 5 | Viewed by 1910

Abstract

The main purpose of this paper is the investigation of the feasibility of a novel hybrid module specifically designed for the Mediterranean Sea. This module is intended to work as an offshore floating breakwater in severe sea states, and alternatively as a wave [...] Read more.

The main purpose of this paper is the investigation of the feasibility of a novel hybrid module specifically designed for the Mediterranean Sea. This module is intended to work as an offshore floating breakwater in severe sea states, and alternatively as a wave energy converter in the more frequent mild sea states, depending on its level of submergence. An experimental campaign on a 1:10 module has been carried out in the wave tank of the University of Campania. The dynamic response of the device, as well as its hydraulic performances, was investigated under various wave conditions. The experimental results highlight the possibility of realizing and installing hybrid structures combining energy conversion and wave attenuation. Full article

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19 pages, 2981 KiB

Open AccessEditor’s ChoiceArticle

Debating the Rules: An Experimental Approach to Assess Cyprinid Passage Performance Thresholds in Vertical Slot Fishways

by Filipe Romão, Ana L. Quaresma, Joana Simão, Francisco J. Bravo-Córdoba, Teresa Viseu, José M. Santos, Francisco J. Sanz-Ronda and António N. Pinheiro

Water 2024, 16(3), 439; https://doi.org/10.3390/w16030439 - 29 Jan 2024

Cited by 6 | Viewed by 1556

Abstract

Throughout the world, emerging barriers in river systems block longitudinal connectivity for migrating fish, causing significant impacts by precluding them from carrying out vital life cycle activities. Fishways are still the main mitigation solution implemented, where barrier removal is not feasible. Within the [...] Read more.

Throughout the world, emerging barriers in river systems block longitudinal connectivity for migrating fish, causing significant impacts by precluding them from carrying out vital life cycle activities. Fishways are still the main mitigation solution implemented, where barrier removal is not feasible. Within the multiple technical fish passage devices, the vertical slot fishway (VSF) is considered the most reliable. Early design guidelines, established for cyprinids, indicate that the volumetric dissipation power (P_v) in the pools should be P_v < 150 Wm⁻³, while most frequent slope values range from 10 to 12%. In this study, an experimental approach was conducted to question and debate the validity of these recommendations. For this, the Iberian barbel (Luciobarbus bocagei, Steindachner, 1864) passage performance was assessed in a full-scale fishway that exceeded P_v design guidelines, under different configurations. These varied in discharge (Q) and mean pool water depth (h_m): VSF1 (Q = 81 Ls⁻¹; h_m = 0.55 m); VSF2 (Q = 110 Ls⁻¹; h_m = 0.80 m); and the same design was equipped with a deep notch: DN1 (Q = 71 Ls⁻¹; h_m = 0.55 m); DN2 (Q = 99 Ls⁻¹; h_m = 0.80 m). The slope was set to 15.2% while the head drop per pool was Δh = 0.28 m, which generated a P_v that ranged from 222 in VSF1 to 187 Wm⁻³ in DN2. Passage behaviour was assessed using PIT telemetry and time-to-event analysis to evaluate the barbel upstream passage using standardized metrics: (i) motivation (ii) ascend success, and (iii) transit time. The hydrodynamic scenarios experienced by fish were characterized through a numerical model using computational fluid dynamics (CFD). The results, contrary to what was expected, showed a higher performance in VSF1 confirmed by the ascent analysis and transit time. Although no differences were found in fish motivation, the results indicate that larger fish displayed lower times to perform the first passage attempt. The CFD results show that, although maximum velocities and turbulence (turbulent kinetic energy (TKE) and Reynolds shear stress (RSS)) do not change significantly between configurations, their distribution in the pools is quite different. Regarding TKE, larger volumes with magnitudes higher than 0.05 m²s⁻² were notorious in both DN1 and DN2 configurations compared to VSF1, influencing passage efficiency which is in line with the ascent and transit time metrics results. Overall, the present research undeniably debates the literature design guidelines and reinforces the need to jointly assess species-specific fish passage criteria and fishway hydrodynamics, whereas precaution should be taken when using very general recommendations. Full article

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21 pages, 5595 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Future Climate Change Impacts on Groundwater Recharge Using Hydrological Modeling in the Choushui River Alluvial Fan, Taiwan

by Thi-My-Linh Ngo, Shih-Jung Wang and Pei-Yuan Chen

Water 2024, 16(3), 419; https://doi.org/10.3390/w16030419 - 27 Jan 2024

Cited by 9 | Viewed by 4298

Abstract

This research delves into the crucial role of groundwater in underpinning ecosystems and human resilience amidst drastic and unpredictable climate change, particularly as water resources face increasing sustainability concerns due to population surges and climate change. Utilizing a combined approach of SWAT-MODFLOW models, [...] Read more.

This research delves into the crucial role of groundwater in underpinning ecosystems and human resilience amidst drastic and unpredictable climate change, particularly as water resources face increasing sustainability concerns due to population surges and climate change. Utilizing a combined approach of SWAT-MODFLOW models, we estimate the streamflow discharge and groundwater recharge in the Choushui River Alluvial Fan, Taiwan. These models allow evaluation of the distribution and proportion of recharge areas as well as the accuracy and the potential influence of future climate change scenarios on groundwater recharge. The findings show a strong correlation between the simulation and actual observations, evidenced by the Nash–Sutcliffe model efficiency coefficients (NSE) of 0.920 and 0.846 for calibration and validation in the Choushui River, and 0.549 and 0.548 for the Pei-Kang River, respectively. The model demonstrates a reliable representation of the watershed response, supported by robust statistical performance. The analysis reveals the variable impacts of climate change on groundwater recharge, dependent on the chosen scenario and period. Some scenarios indicate that the maximum observed increase in groundwater recharge is 66.36% under the RCP2.6 scenario in the long-term period (2061–2080), while the minimum observed increase is 29.67% under the RCP4.5 scenario in the initial time frame; however, all demonstrate a decrease ranging from 23.05% to 41.92% across different RCPs in the impact of climate change over time, suggesting a potential long-term decrease in the impact of climate change on groundwater recharge. This study provides indispensable insights into the spatial hotspots in the top fan and the potential range of impact rates of climate change on groundwater recharge, underscoring the importance of continuous research and the thorough evaluation of multiple scenarios. Moreover, we establish a primary framework for using a top-ranked MIROC5 projection of general circulation models (GCMs) to delineate an essential premise that facilitates the advanced exploration of alternative scenario augmentations, bolstering the comprehensive investigation of climate change impacts on groundwater recharge. It is proposed that these findings serve as a guidepost for sustainable water resource management and policy-making in the face of climate change and escalating water demand. Full article

(This article belongs to the Special Issue Climate Change Impact on Hydrological Cycle and Water Resources Management, 2nd Edition)

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17 pages, 3574 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Collective Irrigation Network Layout through the Application of the Analytic Hierarchy Process (AHP) Multicriteria Analysis Method

by César González-Pavón, Carmen Virginia Palau, Juan Manzano Juárez, Vicente Estruch-Guitart, Santiago Guillem-Picó and Ibán Balbastre-Peralta

Water 2024, 16(3), 370; https://doi.org/10.3390/w16030370 - 23 Jan 2024

Cited by 4 | Viewed by 1853

Abstract

On numerous occasions, we often have very little information or must make a decision considering qualitative aspects that are difficult to evaluate. This study focuses on obtaining objective criteria to assist in decision-making in the design phase of pressurized water pipes in collective [...] Read more.

On numerous occasions, we often have very little information or must make a decision considering qualitative aspects that are difficult to evaluate. This study focuses on obtaining objective criteria to assist in decision-making in the design phase of pressurized water pipes in collective irrigation networks. In the layout of these networks, various types of paths and roads for laying pipes can be encountered, and it is not always a simple task to obtain the least costly layout or the one with the fewest issues during construction. In order to obtain objective results, different layout alternatives are evaluated using the Analytic Hierarchy Process (AHP) Multicriteria Analysis Methodology and the Dijkstra algorithm to obtain optimal solutions. This is applied to twelve case studies where the types of available layout paths are identified as alternatives, and four criteria are established for their evaluation. Recognized experts in irrigation modernization conduct the evaluation to derive weighting coefficients for selecting the optimal layout. The coefficients or resistances obtained weigh the lengths of the pipes, allowing the selection of the most suitable alternative based on the defined criteria. The results are compared with a network designed by an expert using classical methodologies, revealing cost improvements in the design phase and a reduction in conflict points, thus leading to faster execution of the works. Full article

(This article belongs to the Special Issue Advances in Hydraulic and Water Resources Research)

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20 pages, 5441 KiB

Open AccessEditor’s ChoiceReview

Groundwater Depletion and Degradation in the North China Plain: Challenges and Mitigation Options

by Jun Du, Yaseen Laghari, Yi-Chang Wei, Linyi Wu, Ai-Ling He, Gao-Yuan Liu, Huan-Huan Yang, Zhong-Yi Guo and Shah Jahan Leghari

Water 2024, 16(2), 354; https://doi.org/10.3390/w16020354 - 21 Jan 2024

Cited by 11 | Viewed by 5672

Abstract

Groundwater is an important natural resource in the North China Plain (NCP) with high economic benefits and social significance. It fulfills 60% of drinking and 70% of irrigation water requirements. In this review, the information is retrieved from high-quality articles published in MEDLINE [...] Read more.

Groundwater is an important natural resource in the North China Plain (NCP) with high economic benefits and social significance. It fulfills 60% of drinking and 70% of irrigation water requirements. In this review, the information is retrieved from high-quality articles published in MEDLINE and other sources. We saw that groundwater is declining faster (>1 m yr⁻¹) and polluting with NO₃⁻ (>30 mg L⁻¹) due to excessive water pumping and application of a nitrogen (N) fertilizer, respectively. The water pumping (>600 mm ha⁻¹ yr⁻¹) for agricultural purposes in the region is higher than the recharge amount (<200 mm yr⁻¹). The low recharge is the result of low rainfall (<600 mm yr⁻¹), and high evapotranspiration (>800 mm yr⁻¹) under the impact of dominant vegetative characteristics of winter wheat–summer maize (W_W-S_M) rotations, covering >80% of the land. Furthermore, N application exceeds the crop assimilation capacity (>250 kg ha⁻¹ yr⁻¹) and leach deep down (>50 kg ha⁻¹) as well as loss in the atmosphere. Presently, Beijing, Tianjin, and Hebei are ecologically the most affected areas. We suggest that excessive water and N fertilizer use for intensive cropping systems should be controlled by paying high attention to groundwater-friendly farming practices. In addition, artificial groundwater recharge options and their safe utilization would be explored across the region to replenish aquifers. This literature review contributes valuable insights to the knowledge bank and offers a foundation for further research and policy development. Full article

(This article belongs to the Special Issue Groundwater Management in a Changing World: Challenges and Endeavors)

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19 pages, 1091 KiB

Open AccessEditor’s ChoiceArticle

Impact of Microplastic on Freshwater Sediment Biogeochemistry and Microbial Communities Is Polymer Specific

by Kristina M. Chomiak, Wendy A. Owens-Rios, Carmella M. Bangkong, Steven W. Day, Nathan C. Eddingsaas, Matthew J. Hoffman, André O. Hudson and Anna Christina Tyler

Water 2024, 16(2), 348; https://doi.org/10.3390/w16020348 - 20 Jan 2024

Cited by 5 | Viewed by 3617

Abstract

Plastic debris is a growing threat in freshwater ecosystems and transport models predict that many plastics will sink to the benthos. Among the most common plastics found in the Laurentian Great Lakes sediments are polyethylene terephthalate (especially fibers; PET), polyvinylchloride (particles; PVC), and [...] Read more.

Plastic debris is a growing threat in freshwater ecosystems and transport models predict that many plastics will sink to the benthos. Among the most common plastics found in the Laurentian Great Lakes sediments are polyethylene terephthalate (especially fibers; PET), polyvinylchloride (particles; PVC), and styrene-butadiene rubber resulting from tire wear (“crumb rubber”; SBR). These materials vary substantially in physical and chemical properties, and their impacts on benthic biogeochemistry and microbial community structure and function are largely unknown. We used a microcosm approach to evaluate the impact of these three plastics on benthic-pelagic coupling, sediment properties, and sediment microbial community structure and function using sediments from Irondequoit Bay, a major embayment of Lake Ontario in Rochester, New York, USA. Benthic metabolism and nitrogen and phosphorous cycling were all uniquely impacted by the different polymers. PET fibers and PVC particles demonstrated the most unique effects, with decreased ecosystem metabolism in sediments containing PET and greater nutrient uptake in sediments with PVC. Microbial diversity was reduced in all treatments containing plastic, but SBR had the most substantial impact on microbial community function, increasing the relative importance of metabolic pathways such as hydrocarbon degradation and sulfur metabolism. Our results suggest that individual polymers have unique impacts on the benthos, with divergent implications for ecosystem function. This provides deeper insight into the myriad ways plastic pollution may impact aquatic ecosystems and will help to inform risk assessment and policy interventions by highlighting which materials pose the greatest risk. Full article

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

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22 pages, 8098 KiB

Open AccessEditor’s ChoiceArticle

Removing Plastic Waste from Rivers: A Prototype-Scale Experimental Study on a Novel River-Cleaning Concept

by Yannic Fuchs, Susanne Scherbaum, Richard Huber, Nils Rüther and Arnd Hartlieb

Water 2024, 16(2), 248; https://doi.org/10.3390/w16020248 - 11 Jan 2024

Cited by 5 | Viewed by 7102

Abstract

Mismanaged plastic waste threatens the sustainable development goals of the United Nations in social, economic, and ecological dimensions. In the pollution process, fluvial systems are critical transport paths for mismanaged plastic waste, connecting land areas with oceans and acting as plastic reservoirs and [...] Read more.

Mismanaged plastic waste threatens the sustainable development goals of the United Nations in social, economic, and ecological dimensions. In the pollution process, fluvial systems are critical transport paths for mismanaged plastic waste, connecting land areas with oceans and acting as plastic reservoirs and accumulation zones. The complex fluid–plastic particle interaction leads to a strong distribution of transported particles over the entire river width and flow depth. Therefore, a holistic plastic removal approach must consider lateral and vertical river dimensions. This study investigates the conceptual design of a comprehensive river-cleaning system that enables the removal of both floating and suspended litter particles from watercourses withstanding flow variations. The innovative technical cleaning infrastructure is based on a self-cleaning system using rotating screen drum units. In 42 prototype-scale experiments using ten representative plastic particle types (both 3D items and fragments) of five different polymer types, we prove the self-cleaning concept of the infrastructure and define its parameters for the best cleaning performance. Its cleaning efficiency is strongly dependent on the polymer type and shape. The overall cleaning efficiency for 3D items amounts to 82%, whereas plastic fragments are removed less efficiently depending on hydraulic conditions. Adaptions to the prototype can enhance its efficiency. Full article

(This article belongs to the Special Issue River Science: Integrated Management of Water Resources in the Anthropocene)

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20 pages, 8827 KiB

Open AccessEditor’s ChoiceArticle

The Heatwave of Summer 2022 in the North-Western Mediterranean Sea: Some Species Were Winners

by Charles-François Boudouresque, Patrick Astruch, Serena André, Bruno Belloni, Aurélie Blanfuné, Éric Charbonnel, Adrien Cheminée, Jean-Michel Cottalorda, Renaud Dupuy de la Grandrive, Michel Marengo, Briac Monnier, Gérard Pergent, Christine Pergent-Martini, Michèle Perret-Boudouresque, Sandrine Ruitton, Isabelle Taupier-Letage and Thierry Thibaut

Water 2024, 16(2), 219; https://doi.org/10.3390/w16020219 - 8 Jan 2024

Cited by 10 | Viewed by 2394

Abstract

The warming trend of the Mediterranean Sea is a long-term process. It has resulted in a northwards and westwards range expansion and abundance increase of thermophilic species, both native and non-indigenous, and in a shrinking of the range of cold-affinity species. Marine heatwaves [...] Read more.

The warming trend of the Mediterranean Sea is a long-term process. It has resulted in a northwards and westwards range expansion and abundance increase of thermophilic species, both native and non-indigenous, and in a shrinking of the range of cold-affinity species. Marine heatwaves (MHWs) are relatively short-term extreme episodes that are responsible for spectacular mortality events in some species and have been extensively reported in the literature. In contrast, the species that benefit from MHWs (the ‘winners’) have been much less studied. A record-breaking MHW occurred in 2022 in the north-western Mediterranean Sea. We focus on three ‘winner’ species, the thermophilic green macroalgae Penicillus capitatus and Microdictyon umbilicatum and the endemic seagrass Posidonia oceanica. Penicillus capitatus, which is mainly present in the area as an inconspicuous turf of entangled filaments (espera stage), produced the erect paintbrush-like stage where sexual reproduction takes place. Microdictyon umbilicatum, usually uncommon, bloomed to the point of clogging fishing nets. Finally, a mass flowering of P. oceanica occurred in late August–September, followed the following year (April–May 2023) by the extensive production and dissemination of fruits and seeds. Both processes, the long-term warming trend and one-off heatwaves, both ‘losers’ and ‘winners’, shape the change in structure and functioning of Mediterranean ecosystems. Full article

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16 pages, 3742 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Degradation of Tetracycline by La-Fe Co-Doped SrTiO₃/TiO₂ Composites: Performance and Mechanism Study

by Mingzhu Hu, Weifang Chen and Jie Wang

Water 2024, 16(2), 210; https://doi.org/10.3390/w16020210 - 7 Jan 2024

Cited by 12 | Viewed by 2595

Abstract

Human health, as well as the ecosystem’s natural equilibrium, may be jeopardized by the discharge of tetracycline into the aquatic environment. In order to effectively photocatalyzed the degradation of tetracycline in aqueous solution under visible light, this study used a two-step hydrothermal approach [...] Read more.

Human health, as well as the ecosystem’s natural equilibrium, may be jeopardized by the discharge of tetracycline into the aquatic environment. In order to effectively photocatalyzed the degradation of tetracycline in aqueous solution under visible light, this study used a two-step hydrothermal approach to produce composites of SrTiO₃/TiO₂ doped with two metal elements, lanthanum (La) and iron (Fe). The crystal structure, morphology, electronic structure, particle size, specific surface area and photocatalytic properties of the catalysts were assessed using a variety of methods, such as fluorescence spectroscopy, UV-Vis diffuse reflectance, X-ray diffraction, scanning electron microscopy, BET and particle size analysis. After 120 min of exposure to visible light, the co-doped catalyst showed a degradation rate of 99.1%, which was nine times greater than that of SrTiO₃/TiO₂ at catalyst dosing of 1.6 g/L and tetracycline concentration of 20 mg/L. The synthesized photocatalyst exhibited good tolerance to changes in pH, with the degradation efficiency of tetracycline remaining stable within the pH range of 4–10. The La-Sr (Ti-Fe) O₃/TiO₂ catalyst also demonstrated excellent photostability after recycling. The mechanism of tetracycline degradation is primarily attributed to the active oxidation by photogenerated holes and •O₂⁻. Furthermore, tetracycline degradation pathways were analyzed via HPLC-MS to identify intermediates. Full article

(This article belongs to the Special Issue Aquaculture Water Safety)

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27 pages, 1890 KiB

Open AccessEditor’s ChoiceArticle

Intelligent Edge-Cloud Framework for Water Quality Monitoring in Water Distribution System

by Essa Q. Shahra, Wenyan Wu, Shadi Basurra and Adel Aneiba

Water 2024, 16(2), 196; https://doi.org/10.3390/w16020196 - 5 Jan 2024

Cited by 8 | Viewed by 2704

Abstract

Ensuring consistent high water quality is paramount in water management planning. This paper addresses this objective by proposing an intelligent edge-cloud framework for water quality monitoring within the water distribution system (WDS). Various scenarios—cloud computing, edge computing, and hybrid edge-cloud computing—are applied to [...] Read more.

Ensuring consistent high water quality is paramount in water management planning. This paper addresses this objective by proposing an intelligent edge-cloud framework for water quality monitoring within the water distribution system (WDS). Various scenarios—cloud computing, edge computing, and hybrid edge-cloud computing—are applied to identify the most effective platform for the proposed framework. The first scenario brings the analysis closer to the data generation point (at the edge). The second and third scenarios combine both edge and cloud platforms for optimised performance. In the third scenario, sensor data are directly sent to the cloud for analysis. The proposed framework is rigorously tested across these scenarios. The results reveal that edge computing (scenario 1) outperforms cloud computing in terms of latency, throughput, and packet delivery ratio obtaining 20.33 ms, 148 Kb/s, and 97.47%, respectively. Notably, collaboration between the edge and cloud enhances the accuracy of classification models with an accuracy of up to 94.43%, this improvement was achieved while maintaining the energy consumption rate at the lowest value. In conclusion, our study demonstrates the effectiveness of the proposed intelligent edge-cloud framework in optimising water quality monitoring, and the superior performance of edge computing, coupled with collaborative edge-cloud strategies, underscores the practical viability of this approach. Full article

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

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18 pages, 4243 KiB

Open AccessEditor’s ChoiceArticle

Investigating Nonpoint Source and Pollutant Reduction Effects under Future Climate Scenarios: A SWAT-Based Study in a Highland Agricultural Watershed in Korea

by Sayed Shah Jan Sadiqi, Won-Ho Nam, Kyoung-Jae Lim and Eunmi Hong

Water 2024, 16(1), 179; https://doi.org/10.3390/w16010179 - 3 Jan 2024

Cited by 4 | Viewed by 3013

Abstract

This study investigated the effects of nonpoint source (NPS) pollution reduction and pollutant dynamics in a highland agricultural watershed in Korea. We employed the SWAT model to simulate hydrological processes and pollution transport within the watershed. The model incorporates future climatic scenarios derived [...] Read more.

This study investigated the effects of nonpoint source (NPS) pollution reduction and pollutant dynamics in a highland agricultural watershed in Korea. We employed the SWAT model to simulate hydrological processes and pollution transport within the watershed. The model incorporates future climatic scenarios derived from downscaled climate projections to assess their impacts on NPS pollution and pollutant reduction methods. These changes lead to heightened surface runoff and erosion rates, resulting in elevated sediment and nutrient concentrations. The projection indicates an anticipated increase in the annual average temperature by 1.3 to 2.1 °C by the mid-century, under scenarios SSP126 and SSP585. Additionally, precipitation levels are projected to increase by 31 to 61 mm from the baseline to the end of the century. Variations in hydrological components such as evapotranspiration, streamflow, and soil moisture are expected to range from +3.2 to +17.2%, −9.1 to +8.1%, and 0.1 to 0.7%, respectively, during the years 2040 and 2080. Fluctuations in TN, SS, and TP loading are estimated to range from −4.5 to +2.3%, −5.8 to +29.0%, and +3.7 to +17.4%, respectively. This study emphasizes the importance of adaptive management options for stakeholders and the need for adaptive management options to reduce nonpoint source pollution and protect water quality to maintain sustainable water supplies and conserve the environment in this watershed. Full article

(This article belongs to the Special Issue Impact of Water and Climate Change on the Environment and Human Activities)

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19 pages, 4240 KiB

Open AccessEditor’s ChoiceArticle

Towards Groundwater-Level Prediction Using Prophet Forecasting Method by Exploiting a High-Resolution Hydrogeological Monitoring System

by Davide Fronzi, Gagan Narang, Alessandro Galdelli, Alessandro Pepi, Adriano Mancini and Alberto Tazioli

Water 2024, 16(1), 152; https://doi.org/10.3390/w16010152 - 30 Dec 2023

Cited by 12 | Viewed by 4107

Abstract

Forecasting of water availability has become of increasing interest in recent decades, especially due to growing human pressure and climate change, affecting groundwater resources towards a perceivable depletion. Numerous research papers developed at various spatial scales successfully investigated daily or seasonal groundwater level [...] Read more.

Forecasting of water availability has become of increasing interest in recent decades, especially due to growing human pressure and climate change, affecting groundwater resources towards a perceivable depletion. Numerous research papers developed at various spatial scales successfully investigated daily or seasonal groundwater level prediction starting from measured meteorological data (i.e., precipitation and temperature) and observed groundwater levels, by exploiting data-driven approaches. Barely a few research combine the meteorological variables and groundwater level data with unsaturated zone monitored variables (i.e., soil water content, soil temperature, and bulk electric conductivity), and—in most of these—the vadose zone is monitored only at a single depth. Our approach exploits a high spatial-temporal resolution hydrogeological monitoring system developed in the Conero Mt. Regional Park (central Italy) to predict groundwater level trends of a shallow aquifer exploited for drinking purposes. The field equipment consists of a thermo-pluviometric station, three volumetric water content, electric conductivity, and soil temperature probes in the vadose zone at 0.6 m, 0.9 m, and 1.7 m, respectively, and a piezometer instrumented with a permanent water-level probe. The monitored period started in January 2022, and the variables were recorded every fifteen minutes for more than one hydrologic year, except the groundwater level which was recorded on a daily scale. The developed model consists of three “virtual boxes” (i.e., atmosphere, unsaturated zone, and saturated zone) for which the hydrological variables characterizing each box were integrated into a time series forecasting model based on Prophet developed in the Python environment. Each measured parameter was tested for its influence on groundwater level prediction. The model was fine-tuned to an acceptable prediction (roughly 20% ahead of the monitored period). The quantitative analysis reveals that optimal results are achieved by expoiting the hydrological variables collected in the vadose zone at a depth of 1.7 m below ground level, with a Mean Absolute Error (MAE) of 0.189, a Mean Absolute Percentage Error (MAPE) of 0.062, a Root Mean Square Error (RMSE) of 0.244, and a Correlation coefficient of 0.923. This study stresses the importance of calibrating groundwater level prediction methods by exploring the hydrologic variables of the vadose zone in conjunction with those of the saturated zone and meteorological data, thus emphasizing the role of hydrologic time series forecasting as a challenging but vital aspect of optimizing groundwater management. Full article

(This article belongs to the Special Issue Data-Driven Approach Supporting Groundwater Resource Understanding, Protection and Management)

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19 pages, 865 KiB

Open AccessEditor’s ChoiceArticle

Planning and Design Strategies for Green Stormwater Infrastructure from an Urban Design Perspective

by Jianxi Ou, Junqi Li, Xiaojing Li and Jianqin Zhang

Water 2024, 16(1), 29; https://doi.org/10.3390/w16010029 - 20 Dec 2023

Cited by 7 | Viewed by 3698

Abstract

With the rapid advancement of ecological civilization construction, prioritizing green stormwater infrastructure to address urban stormwater management issues has become an important strategy for ecological priority and green development in sustainable urban development. Green stormwater infrastructure, as a major facility in the construction [...] Read more.

With the rapid advancement of ecological civilization construction, prioritizing green stormwater infrastructure to address urban stormwater management issues has become an important strategy for ecological priority and green development in sustainable urban development. Green stormwater infrastructure, as a major facility in the construction of sponge cities, can reduce the generation and external discharge of runoff and play a purification role. However, there are various types of green stormwater infrastructure, each with different control effects and applicable conditions. Therefore, to facilitate the planning, design, acceptance, assessment, and monitoring evaluation of sponge city green stormwater infrastructure, this study proposes the “sponge equivalent” method. By comparing the control effects of different facilities with bioretention facilities, the method standardizes the effects, making them easier to understand and apply. Taking a typical area of Beijing and its urban roads as examples, the study analyzed and applied planning and design control strategies. The results show that for a residential area of 1 km², to achieve the annual runoff total control rate target of 85%, the method of converting runoff volume control equivalents, using bioretention pools as a benchmark, allows for the calculation of various combinations of areas of different types of green stormwater infrastructure, such as sunken green spaces, permeable paving bricks, green roofs, and water storage tanks. This optimizes the planning index of Beijing, which mandates stormwater detention facilities for new projects with a hardened surface area of 2000 m² or more. The sponge equivalent method can optimize the planning and design control strategy of green stormwater infrastructure, allowing for rapid assessment and application of the design scale of green stormwater infrastructure in areas during the planning and design stage, providing theoretical and technical support for ecological and green urban stormwater management. The application of this research method helps promote green development and ecological priority in urban sustainable development strategies, and the conclusions provide valuable references for decision-makers and practitioners in related fields. Full article

(This article belongs to the Special Issue Urban Water Management and Hydrological Process)

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21 pages, 4842 KiB

Open AccessEditor’s ChoiceArticle

Reference Evapotranspiration Estimation Using Genetic Algorithm-Optimized Machine Learning Models and Standardized Penman–Monteith Equation in a Highly Advective Environment

by Shafik Kiraga, R. Troy Peters, Behnaz Molaei, Steven R. Evett and Gary Marek

Water 2024, 16(1), 12; https://doi.org/10.3390/w16010012 - 20 Dec 2023

Cited by 10 | Viewed by 2640

Abstract

Accurate estimation of reference evapotranspiration (ET_r) is important for irrigation planning, water resource management, and preserving agricultural and forest habitats. The widely used Penman–Monteith equation (ASCE-PM) estimates ET_r across various timescales using ground weather station data. However, discrepancies persist between [...] Read more.

Accurate estimation of reference evapotranspiration (ET_r) is important for irrigation planning, water resource management, and preserving agricultural and forest habitats. The widely used Penman–Monteith equation (ASCE-PM) estimates ET_r across various timescales using ground weather station data. However, discrepancies persist between estimated ET_r and measured ET_r obtained from weighing lysimeters (ET_r-lys), particularly in advective environments. This study assessed different machine learning (ML) models in comparison to ASCE-PM for ET_r estimation in highly advective conditions. Various variable combinations, representing both radiation and aerodynamic components, were organized for evaluation. Eleven datasets (DT) were created for the daily timescale, while seven were established for hourly and quarter-hourly timescales. ML models were optimized by a genetic algorithm (GA) and included support vector regression (GA-SVR), random forest (GA-RF), artificial neural networks (GA-ANN), and extreme learning machines (GA-ELM). Meteorological data and direct measurements of well-watered alfalfa grown under reference ET conditions obtained from weighing lysimeters and a nearby weather station in Bushland, Texas (1996–1998), were used for training and testing. Model performance was assessed using metrics such as root mean square error (RMSE), mean absolute error (MAE), mean bias error (MBE), and coefficient of determination (R²). ASCE-PM consistently underestimated alfalfa ET across all timescales (above 7.5 mm/day, 0.6 mm/h, and 0.2 mm/h daily, hourly, and quarter-hourly, respectively). On hourly and quarter-hourly timescales, datasets predominantly composed of radiation components or a blend of radiation and aerodynamic components demonstrated superior performance. Conversely, datasets primarily composed of aerodynamic components exhibited enhanced performance on a daily timescale. Overall, GA-ELM outperformed the other models and was thus recommended for ET_r estimation at all timescales. The findings emphasize the significance of ML models in accurately estimating ET_r across varying temporal resolutions, crucial for effective water management, water resources, and agricultural planning. Full article

(This article belongs to the Topic Hydrology and Water Resources in Agriculture and Ecology)

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16 pages, 6284 KiB

Open AccessEditor’s ChoiceArticle

A Quantitative Approach for Identifying Nitrogen Sources in Complex Yeongsan River Watershed, Republic of Korea, Based on Dual Nitrogen Isotope Ratios and Hydrological Model

by Seoyeon Hong, Youngun Han, Jihae Kim, Bo Ra Lim, Si-Young Park, Heeju Choi, Mi Rae Park, Eunmi Kim, Soohyung Lee, Yujeong Huh, Kyunghyun Kim, Won-Seok Lee, Taewoo Kang and Min-Seob Kim

Water 2023, 15(24), 4275; https://doi.org/10.3390/w15244275 - 14 Dec 2023

Cited by 8 | Viewed by 1756

Abstract

Effective management of nitrate loading in complex river systems requires quantitative estimation to trace different nitrogen sources. This study aims to validate an integrated framework using soluble nitrogen isotope ratios (δ¹⁵N–NH₄ and δ¹⁵N–NO₃) and hydrological modeling [...] Read more.

Effective management of nitrate loading in complex river systems requires quantitative estimation to trace different nitrogen sources. This study aims to validate an integrated framework using soluble nitrogen isotope ratios (δ¹⁵N–NH₄ and δ¹⁵N–NO₃) and hydrological modeling (hydrological simulation program SPARROW) of the main stream and tributaries in the Yeongsan River to determine anthropogenic nitrogen fluxes among different land-use types in the complex river watershed. The δ¹⁵N–NH₄ and δ¹⁵N–NO₃ isotopic compositions varied across different land-use types (4.9 to 15.5‰ for δ¹⁵N–NH₄ and −4.9 to 12.1‰ for δ¹⁵N–NO₃), reflecting the different sources of nitrogen in the watershed (soil N including synthetic fertilizer N, manure N, and sewage treatment plant effluent N). We compared the soluble nitrogen isotopic compositions (δ¹⁵N–NH₄ and δ¹⁵N–NO₃) of the river water with various nitrogen sources (soil N, manure N, and sewage N) to assess their contribution, revealing that N from sewage treatment plant effluent as a point source was dominant during the dry season and N from forest- and soil-derived non-point sources was dominant due to intensive rainfall during the wet season. The coefficient of determination (R²) between the measured pollution load and the predicted pollution load calculated by the SPARROW model was 0.95, indicating a high correlation. In addition, the EMMA-based nitrogen contributions compared to the SPARROW-based nitrogen fluxes were similar to each other, indicating that large amounts of forest- and soil-derived N may be transported to the Yeongsan River watershed as non-point sources, along with the effect of sewage treatment plant effluent N as a point source. This study provides valuable insights for the formulation of management policies to control nitrogen inputs from point and non-point sources across different land-use types for the restoration of water quality and aquatic ecosystems in complex river systems. Given the recent escalation in human activity near aquatic environments, this framework is effective in estimating the quantitative contribution of individual anthropogenic nitrogen sources transported along riverine systems. Full article

(This article belongs to the Special Issue Transport of Pollutants in Agricultural Watersheds)

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19 pages, 2026 KiB

Open AccessEditor’s ChoiceArticle

Mitigating Ammonia, Methane, and Carbon Dioxide Emissions from Stored Pig Slurry Using Chemical and Biological Additives

by Oumaima El bied, Martire Angélica Terrero Turbí, Amalia García-Valero, Ángel Faz Cano and José A. Acosta

Water 2023, 15(23), 4185; https://doi.org/10.3390/w15234185 - 4 Dec 2023

Cited by 6 | Viewed by 2734

Abstract

This study addresses the challenge of mitigating ammonia and greenhouse gas (GHG) emissions from stored pig slurry using chemical and biological additives. The research employs dynamic chambers to evaluate the effectiveness of these additives. Chemical agents (sulfuric acid) and biological additives (DAB bacteria) [...] Read more.

This study addresses the challenge of mitigating ammonia and greenhouse gas (GHG) emissions from stored pig slurry using chemical and biological additives. The research employs dynamic chambers to evaluate the effectiveness of these additives. Chemical agents (sulfuric acid) and biological additives (DAB bacteria) containing specific microbial strains are tested (a mixture of Rhodopseudomonas palustris, Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, Nitrosomona europea, Nictobacter winogradaskyi, and nutritional substrate). Controlled experiments simulate storage conditions and measure emissions of ammonia, methane, and carbon dioxide. Through statistical analysis of the results, this study evaluates the additives’ impact on emission reduction. Sulfuric acid demonstrated a reduction of 92% in CH₄, 99% in CO₂, and 99% in NH₃ emissions. In contrast, the biological additives showed a lesser impact on CH₄, with an 8% reduction, but more substantial reductions of 71% for CO₂ and 77% for NH₃.These results shed light on the feasibility of employing these additives to mitigate environmental impacts in pig slurry management and contribute to sustainable livestock practices by proposing strategies to reduce the ecological consequences of intensive animal farming. Full article

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

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14 pages, 4757 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Heavy Metal Contaminants and Mobility in Sewage sludge-soil Mixtures for Sustainable Agricultural Practices

by Agata Janaszek and Robert Kowalik

Water 2023, 15(22), 3992; https://doi.org/10.3390/w15223992 - 16 Nov 2023

Cited by 11 | Viewed by 2702

Abstract

This study presents a comprehensive analysis of the potential utilization of sewage sludge in agriculture, focusing on the assessment of heavy metal contaminants and their mobility in sewage sludge-soil mixtures. The innovative approach of investigating heavy metal fractions in these mixtures sheds light [...] Read more.

This study presents a comprehensive analysis of the potential utilization of sewage sludge in agriculture, focusing on the assessment of heavy metal contaminants and their mobility in sewage sludge-soil mixtures. The innovative approach of investigating heavy metal fractions in these mixtures sheds light on their environmental implications. In this study, sludge and soil samples from three different soil categories were collected, and the mobility of heavy metals was investigated using sequential BCR analysis. A thorough assessment of the risk of environmental contamination associated with the agricultural use of sludge was also carried out. This study included the calculation of various risk indicators, such as the Geoaccumulation Index of heavy metals in soil (Igeo), the risk assessment code (RAC), and the author’s element mobility ratio (EMR), which included a comparison of the overall metal concentrations in sludge, soil, and mixtures. This study demonstrates that the key to using sludge is to know the form of mobility of the metals present in the sludge and how they behave once they are introduced into the soil. Full article

(This article belongs to the Special Issue Resource Use of Sewage Sludge for Soil Application)

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18 pages, 2944 KiB

Open AccessEditor’s ChoiceArticle

Flood Forecasting Using Hybrid LSTM and GRU Models with Lag Time Preprocessing

by Yue Zhang, Zimo Zhou, Jesse Van Griensven Thé, Simon X. Yang and Bahram Gharabaghi

Water 2023, 15(22), 3982; https://doi.org/10.3390/w15223982 - 16 Nov 2023

Cited by 20 | Viewed by 4570

Abstract

Climate change and urbanization have increased the frequency of floods worldwide, resulting in substantial casualties and property loss. Accurate flood forecasting can offer governments early warnings about impending flood disasters, giving them a chance to evacuate and save lives. Deep learning is used [...] Read more.

Climate change and urbanization have increased the frequency of floods worldwide, resulting in substantial casualties and property loss. Accurate flood forecasting can offer governments early warnings about impending flood disasters, giving them a chance to evacuate and save lives. Deep learning is used in flood forecasting to improve the timeliness and accuracy of flood water level predictions. While various deep learning models similar to Long Short-Term Memory (LSTM) have achieved notable results, they have complex structures with low computational efficiency, and often lack generalizability and stability. This study applies a spatiotemporal Attention Gated Recurrent Unit (STA-GRU) model for flood prediction to increase the models’ computing efficiency. Another salient feature of our methodology is the incorporation of lag time during data preprocessing before the training of the model. Notably, for 12-h forecasting, the STA-GRU model’s R-squared (R2) value increased from 0.8125 to 0.9215. Concurrently, the model manifested reduced root mean squared error (RMSE) and mean absolute error (MAE) metrics. For a more extended 24-h forecasting, the R2 value of the STA-GRU model improved from 0.6181 to 0.7283, accompanied by diminishing RMSE and MAE values. Seven typical deep learning models—the LSTM, the Convolutional Neural Networks LSTM (CNNLSTM), the Convolutional LSTM (ConvLSTM), the spatiotemporal Attention Long Short-Term Memory (STA-LSTM), the GRU, the Convolutional Neural Networks GRU (CNNGRU), and the STA-GRU—are compared for water level prediction. Comparative analysis delineated that the use of the STA-GRU model and the application of the lag time pre-processing method significantly improved the reliability and accuracy of flood forecasting. Full article

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30 pages, 2691 KiB

Open AccessEditor’s ChoiceReview

Urban Wastewater Mining for Circular Resource Recovery: Approaches and Technology Analysis

by Andrea G. Capodaglio

Water 2023, 15(22), 3967; https://doi.org/10.3390/w15223967 - 15 Nov 2023

Cited by 18 | Viewed by 4209

Abstract

Urban areas comprise less than 1% of the Earth’s land surface, yet they host more than half the global population and are responsible for the majority of global energy use and related CO₂ emissions. Urbanization is increasing the speed and local intensity [...] Read more.

Urban areas comprise less than 1% of the Earth’s land surface, yet they host more than half the global population and are responsible for the majority of global energy use and related CO₂ emissions. Urbanization is increasing the speed and local intensity of water cycle exploitation, with a large number of cities suffering from water shortage problems globally. Wastewater (used water) contains considerable amounts of embedded energy and recoverable materials. Studies and applications have demonstrated that recovering or re-capturing water, energy, and materials from wastewater is a viable endeavor, with several notable examples worldwide. Reclaiming all these resources through more widespread application of effective technological approaches could be feasible and potentially profitable, although challenging from several points of view. This paper reviews the possibilities and technical opportunities applicable to the mining of resources within the urban water cycle and discusses emerging technologies and issues pertaining to resource recovery and reuse applications. The present and future sustainability of approaches is also discussed. Since sewage management issues are not “one size fits all”, local conditions must be carefully considered when designing optimal local resource recovery solutions, which are influenced not just by technology but also by multiple economic, geographical, and social factors. Full article

(This article belongs to the Special Issue Resource Recovery Monitoring and Circular Economy Model in Wastewater)

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16 pages, 7610 KiB

Open AccessEditor’s ChoiceReview

Systematic Review of Contaminants of Emerging Concern (CECs): Distribution, Risks, and Implications for Water Quality and Health

by Weiying Feng, Yuxin Deng, Fang Yang, Qingfeng Miao and Su Kong Ngien

Water 2023, 15(22), 3922; https://doi.org/10.3390/w15223922 - 10 Nov 2023

Cited by 22 | Viewed by 8847

Abstract

The introduction of contaminants of emerging concern (CECs) into the environment has raised concerns due to the significant risks they pose to both ecosystems and human health. In this sys-tematic review, we investigate research trends on CECs worldwide over the past 10 years, [...] Read more.

The introduction of contaminants of emerging concern (CECs) into the environment has raised concerns due to the significant risks they pose to both ecosystems and human health. In this sys-tematic review, we investigate research trends on CECs worldwide over the past 10 years, focus-ing on four critical aspects: (i) the identification and distribution of typical CECs across various media, (ii) the sources and environmental behavior of CECs, (iii) the implications of CECs expo-sure on human health, and (iv) risk assessment and control measures for CECs. The review re-veals a comprehensive understanding of the typical types and distribution of CECs in different environmental media, shedding light on their prevalence and potential impact on ecosystems. Furthermore, insights into the sources and behavior of CECs provide crucial information for de-vising effective strategies to mitigate their release into the environment. By examining the health effects of EC exposure, we highlight the importance of considering potential risks to human well-being. This aspect of the review emphasizes the significance of monitoring and managing CECs to safeguard public health. The review also synthesizes the advancements in risk assessment methodologies and control measures for CECs, which are essential for developing comprehensive regulations and guidelines to manage these contaminants effectively. Drawing from the findings, we identify future research directions for CECs in aquatic environments. Full article

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

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18 pages, 2493 KiB

Open AccessEditor’s ChoiceArticle

Use of Sawdust (Aspidosperma polyneuron) in the Preparation of a Biocarbon-Type Adsorbent Material for Its Potential Use in the Elimination of Cationic Contaminants in Wastewater

by Rodrigo Ortega-Toro, Ángel Villabona-Ortíz, Candelaria Tejada-Tovar, Adriana Herrera-Barros and Daniela Cabrales-Sanjuan

Water 2023, 15(21), 3868; https://doi.org/10.3390/w15213868 - 6 Nov 2023

Cited by 8 | Viewed by 1762

Abstract

Chemically modified bioadsorbents were prepared using sawdust (Aspidosperma polyneuron) functionalized with urea at different concentrations (BC-1M, BC-3M, and BC-6M) to evaluate their adsorption capacity by the methylene blue method. Fourier transform spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) were employed to characterize [...] Read more.

Chemically modified bioadsorbents were prepared using sawdust (Aspidosperma polyneuron) functionalized with urea at different concentrations (BC-1M, BC-3M, and BC-6M) to evaluate their adsorption capacity by the methylene blue method. Fourier transform spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) were employed to characterize the surface morphology of the biomaterials. The best adsorption capacity was obtained using the biocarbon modified with urea 6M (BC-6M), displaying a methylene blue index of 12.4 mg/g with a zero-charge point (pHpzc) at 5.5, suggesting the potential application of this chemically modified bioadsorbent for the removal of cationic contaminants in aqueous media. Full article

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

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12 pages, 725 KiB

Open AccessEditor’s ChoiceArticle

Circular Economy in Wastewater Treatment Plants—Potential Opportunities for Biogenic Elements Recovery

by Alina Dereszewska and Stanislaw Cytawa

Water 2023, 15(21), 3857; https://doi.org/10.3390/w15213857 - 6 Nov 2023

Cited by 9 | Viewed by 4071

Abstract

Technologies used in municipal wastewater treatment plants (WWTPs) allow the recovery of energy and valuable elements (phosphorus, nitrogen, and organic carbon) for the soil. This article presents, in schematic form, the carbon, nitrogen, and phosphorus cycling in a WWTP with a load of [...] Read more.

Technologies used in municipal wastewater treatment plants (WWTPs) allow the recovery of energy and valuable elements (phosphorus, nitrogen, and organic carbon) for the soil. This article presents, in schematic form, the carbon, nitrogen, and phosphorus cycling in a WWTP with a load of 70,000 Population Equivalent and develops a spreadsheet to estimate their recovery. Biogas generation enables the recovery of 1126 Mg of organic carbon per year and the generation of 12.6 GWh of energy. The most rational form of organic waste recycling is the production of compost with fertilizing parameters, but efforts should be made to reduce iron compounds in its composition. It has been estimated that compost production provides the recovery of 30% of carbon, 98% of phosphorus, and 18% of nitrogen from the streams of these elements entering the WWTP. The possibility of partially replacing the iron coagulants used to precipitate phosphorus with waste magnesium salt is presented, leading to the precipitation of struvite, which is well absorbed by plants. The article presents the advantages of combining sewage treatment with organic waste management in WWTPs. The developed spreadsheet allows for the control of energy recovery through the quantitative selection of organic waste for fermentation. Full article

(This article belongs to the Special Issue Biological Wastewater Treatment towards a Sustainable Circular Economy)

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13 pages, 9237 KiB

Open AccessEditor’s ChoiceArticle

Numerical Study on the Influence of Combined Rectification Facilities on the Flow in the Forebay of Pumping Station

by Xiaobo Zheng, Pengli Zhang, Wenjing Zhang, Yue Yu and Yaping Zhao

Water 2023, 15(21), 3847; https://doi.org/10.3390/w15213847 - 3 Nov 2023

Cited by 8 | Viewed by 1940

Abstract

The flow pattern of the forebay of the pumping station has a considerable effect on the operating efficiency and stability of the pump unit. A good forebay flow pattern can enable the pump unit to improve efficiency and operating conditions. This study takes [...] Read more.

The flow pattern of the forebay of the pumping station has a considerable effect on the operating efficiency and stability of the pump unit. A good forebay flow pattern can enable the pump unit to improve efficiency and operating conditions. This study takes a large pumping station as the research object and considers two rectification schemes, namely, a single bottom sill and a “bottom sill + diversion pier”. Without rectification facilities under different start-up schemes, the forebay flow pattern after the addition of rectification facilities is calculated, and the influence of single and combined rectification facilities is analyzed. Results show large-scale undesirable flow structures such as backflow and vortex in the forebay of the original design that without rectification facilities and uneven flow distribution occurs in the operating unit. The addition of a bottom sill in the forebay can control the central water beam from the water diversion pipe. The flow is divided to spread to both sides of the forebay and can be rectified twice after installing the diversion piers. The combined rectifier facility of “bottom sill + diversion pier” is beneficial to disperse incoming flow and make the flow distribution of each unit more uniform. The backflow and vortex inside the forepond are basically eliminated, and the flow state of the forepond is significantly improved. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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24 pages, 8585 KiB

Open AccessEditor’s ChoiceReview

Biological Invasions in Fresh Waters: Micropterus salmoides, an American Fish Conquering the World

by Maria Letizia Costantini, Jerzy Piotr Kabala, Simona Sporta Caputi, Matteo Ventura, Edoardo Calizza, Giulio Careddu and Loreto Rossi

Water 2023, 15(21), 3796; https://doi.org/10.3390/w15213796 - 30 Oct 2023

Cited by 10 | Viewed by 4776

Abstract

Biological invasions in fresh waters cause biodiversity loss and impairment of ecosystem functioning. Many freshwater invasive species are fish, including the largemouth bass Micropterus salmoides, which is considered one of the 100 worst invasive species in the world. Fast individual growth rates, [...] Read more.

Biological invasions in fresh waters cause biodiversity loss and impairment of ecosystem functioning. Many freshwater invasive species are fish, including the largemouth bass Micropterus salmoides, which is considered one of the 100 worst invasive species in the world. Fast individual growth rates, high dispersal ability, ecological tolerance, and trophic plasticity are among the characteristics contributing to its success. The negative impact of M. salmoides on littoral fish communities is believed to be mitigated by habitat structural complexity resulting from aquatic vegetation and coarse woody debris, while the main limits on its spread seem to be strong water flows and high turbidity, which impairs visual predation. Together with the human overexploitation of its potential fish antagonists, habitat alteration could result in M. salmoides having seriously detrimental effects on native biodiversity. The purpose of this study is to critically review the life history and ecology of M. salmoides, its impact on ecosystems outside North America, and the effects of anthropogenic activities on its spread. This will highlight environmental factors that favor or limit its invasive success, helping to identify management measures that might mitigate its negative effects on freshwater biodiversity. Full article

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21 pages, 4621 KiB

Open AccessEditor’s ChoiceReview

Surface Velocity to Depth-Averaged Velocity—A Review of Methods to Estimate Alpha and Remaining Challenges

by Hamish Biggs, Graeme Smart, Martin Doyle, Niklas Eickelberg, Jochen Aberle, Mark Randall and Martin Detert

Water 2023, 15(21), 3711; https://doi.org/10.3390/w15213711 - 24 Oct 2023

Cited by 14 | Viewed by 4599

Abstract

The accuracy of discharge measurements derived from surface velocities are highly dependent on the accuracy of conversions from surface velocity

u_{s}

to depth-averaged velocity

U

. This conversion factor is typically known as the ‘velocity coefficient’, ‘velocity index’, ‘calibration factor’, ‘alpha coefficient’, [...] Read more.

The accuracy of discharge measurements derived from surface velocities are highly dependent on the accuracy of conversions from surface velocity

u_{s}

to depth-averaged velocity

U

. This conversion factor is typically known as the ‘velocity coefficient’, ‘velocity index’, ‘calibration factor’, ‘alpha coefficient’, or simply ‘alpha’, where

α = {U / u}_{s}

. At some field sites detailed in situ measurements can be made to calculate alpha, while in other situations (such as rapid response flood measurements) alpha must be estimated. This paper provides a review of existing methods for estimating alpha and presents a workflow for selecting the appropriate method, based on available data. Approaches to estimating alpha include: reference discharge and surface velocimetry measurements; extrapolated ADCP velocity profiles; log law profiles; power law profiles; site characteristics; and default assumed values. Additional methods for estimating alpha that require further development or validation are also described. This paper then summarises methods for accounting for spatial and temporal heterogeneity in alpha, such as ‘stage to alpha rating curves’, ‘site alpha vs. local alpha’, and ‘the divided channel method’. Remaining challenges for the accurate estimation of alpha are discussed, as well as future directions that will help to address these challenges. Although significant work remains to improve the estimation of alpha (notably to address surface wind effects and velocity dip), the methods covered in this paper could provide a substantial accuracy improvement over selecting the ‘default value’ of 0.857 for alpha for every discharge measurement. Full article

(This article belongs to the Special Issue River Flow Monitoring: Needs, Advances and Challenges)

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