Water

25 pages, 2906 KiB

Open AccessEditor’s ChoiceArticle

Passive Detection of Phosphorus in Agricultural Tile Waters Using Reactive Hybrid Anion Exchange Resins

by Zhe Li, Maria Librada Chu, Lowell Gentry, Ying Li, Corey Mitchell and Yuji Arai

Water 2020, 12(10), 2808; https://doi.org/10.3390/w12102808 - 10 Oct 2020

Cited by 1 | Viewed by 1687

Tile drainage waters carry considerable loads of phosphorus (P) from agricultural fields to rivers and streams in the Midwestern U.S. An innovative and economical approach to monitor dissolved reactive P (DRP) flux in tile waters is needed to understand the extent of P [...] Read more.

Tile drainage waters carry considerable loads of phosphorus (P) from agricultural fields to rivers and streams in the Midwestern U.S. An innovative and economical approach to monitor dissolved reactive P (DRP) flux in tile waters is needed to understand the extent of P loss in field-scale. In this study, a passive sampling technique was developed using iron oxide-coated polyacrylic/polystyrene anion exchange resins (hybrid resins) a P sink. Laboratory batch adsorption isotherm and kinetic experiments indicated that the hybrid resins had high P adsorption capacity (7.69–19.84 mg/g) and high kinetic performance. The passive sampling method with field-calibrated hybrid polyacrylic resin and hybrid polystyrene resins (sampling rate: 0.1351 and 0.0763 L/h, respectively) predicted the average DRP concentrations of 0.006–0.020 mg/L, which did not differ significantly (p > 0.05) from the auto-sampling data. A rapid increase in DRP concentration during storm events and subsequent flooding events was also predicted well. In conclusion, a passive detection method using iron oxide coated hybrid resins can be recommended for monitoring seasonally fluctuating DRP flux in agricultural waters as long as the hybrid resins are well-calibrated under specific field conditions (e.g., flow rate and concentration range). Full article

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

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22 pages, 7631 KiB

Open AccessEditor’s ChoiceArticle

Phytoplankton–Macrophyte Interaction in the Lagoon of Venice (Northern Adriatic Sea, Italy)

by Fabrizio Bernardi Aubry, Francesco Acri, Gian Marco Scarpa and Federica Braga

Water 2020, 12(10), 2810; https://doi.org/10.3390/w12102810 - 10 Oct 2020

Cited by 8 | Viewed by 3199

Abstract

The coexistence of phytoplankton and macrophytes in the Lagoon of Venice (Northern Adriatic Sea, Italy) was investigated using in situ data collected monthly as part of International Long Term Ecosystem Research (LTER), together with satellite imagery for the period 1998–2017. The concentrations of [...] Read more.

The coexistence of phytoplankton and macrophytes in the Lagoon of Venice (Northern Adriatic Sea, Italy) was investigated using in situ data collected monthly as part of International Long Term Ecosystem Research (LTER), together with satellite imagery for the period 1998–2017. The concentrations of chlorophyll a and hydrochemical parameters were measured in three areas of the lagoon, where the expansion of well-developed stands of submerged vegetation was observed by remote sensing. Our results suggest interaction between phytoplankton and macrophytes (macroalgae and seagrasses) in the last few years of the time series, evidenced by decreasing chlorophyll a concentrations in the vicinity of the macrophyte stands. The integration of LTER and remotely sensed data made it possible to evaluate the interaction of macrophytes and phytoplankton at the ecosystem scale for the first time in the Lagoon of Venice. Full article

(This article belongs to the Special Issue Anthropogenic and Climatic Disturbances in Freshwater and Coastal Ecosystems: Interactive Impacts and Expected Threats)

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21 pages, 2154 KiB

Open AccessEditor’s ChoiceArticle

Benthic Diatom Communities in Urban Streams and the Role of Riparian Buffers

by Petra Thea Mutinova, Maria Kahlert, Benjamin Kupilas, Brendan G. McKie, Nikolai Friberg and Francis J. Burdon

Water 2020, 12(10), 2799; https://doi.org/10.3390/w12102799 - 9 Oct 2020

Cited by 18 | Viewed by 4343

Abstract

Urbanization impacts stream ecosystems globally through degraded water quality, altered hydrology, and landscape disturbances at the catchment and riparian scales, causing biodiversity losses and altered system functioning. Addressing the “urban stream syndrome” requires multiple mitigation tools, and rehabilitation of riparian vegetation may help [...] Read more.

Urbanization impacts stream ecosystems globally through degraded water quality, altered hydrology, and landscape disturbances at the catchment and riparian scales, causing biodiversity losses and altered system functioning. Addressing the “urban stream syndrome” requires multiple mitigation tools, and rehabilitation of riparian vegetation may help improve stream ecological status and provide key ecosystem services. However, the extent to which forested riparian buffers can help support stream biodiversity in the face of numerous environmental contingencies remains uncertain. We assessed how a key indicator of stream ecological status, benthic diatoms, respond to riparian habitat conditions using 10 urban site pairs (each comprising of one unbuffered and one buffered reach), and additional urban downstream and forest reference upstream sites in the Oslo Fjord basin. Diatom communities were structured by multiple drivers including spatial location, land use, water quality, and instream habitat. Among these, riparian habitat condition independently explained 16% of variation in community composition among site pairs. Changes in community structure and indicator taxa, along with a reduction in pollution-tolerant diatoms, suggested tangible benefits of forested riparian buffers for stream biodiversity in urban environments. Managing urban impacts requires multiple solutions, with forested riparian zones providing a potential tool to help improve biodiversity and ecosystem services. Full article

(This article belongs to the Special Issue Ecosystem Functioning in Rivers and Riparian Zones)

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28 pages, 1620 KiB

Open AccessEditor’s ChoiceReview

Big Data Analytics and Its Role to Support Groundwater Management in the Southern African Development Community

by Zaheed Gaffoor, Kevin Pietersen, Nebo Jovanovic, Antoine Bagula and Thokozani Kanyerere

Water 2020, 12(10), 2796; https://doi.org/10.3390/w12102796 - 9 Oct 2020

Cited by 20 | Viewed by 7870

Abstract

Big data analytics (BDA) is a novel concept focusing on leveraging large volumes of heterogeneous data through advanced analytics to drive information discovery. This paper aims to highlight the potential role BDA can play to improve groundwater management in the Southern African Development [...] Read more.

Big data analytics (BDA) is a novel concept focusing on leveraging large volumes of heterogeneous data through advanced analytics to drive information discovery. This paper aims to highlight the potential role BDA can play to improve groundwater management in the Southern African Development Community (SADC) region in Africa. Through a review of the literature, this paper defines the concepts of big data, big data sources in groundwater, big data analytics, big data platforms and framework and how they can be used to support groundwater management in the SADC region. BDA may support groundwater management in SADC region by filling in data gaps and transforming these data into useful information. In recent times, machine learning and artificial intelligence have stood out as a novel tool for data-driven modeling. Managing big data from collection to information delivery requires critical application of selected tools, techniques and methods. Hence, in this paper we present a conceptual framework that can be used to manage the implementation of BDA in a groundwater management context. Then, we highlight challenges limiting the application of BDA which included technological constraints and institutional barriers. In conclusion, the paper shows that sufficient big data exist in groundwater domain and that BDA exists to be used in groundwater sciences thereby providing the basis to further explore data-driven sciences in groundwater management. Full article

(This article belongs to the Special Issue The Application of Artificial Intelligence in Hydrology)

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28 pages, 959 KiB

Open AccessFeature PaperEditor’s ChoiceReview

What We Know about Water: A Water Literacy Review

by Meghan McCarroll and Hillary Hamann

Water 2020, 12(10), 2803; https://doi.org/10.3390/w12102803 - 9 Oct 2020

Cited by 34 | Viewed by 14188

Abstract

Water literacy, or the culmination of water-related knowledge, attitudes and behaviors, is a relatively new field of study with growing importance for sustainable water management and social water equity. However, its definition and use across existing literature are varied and often inconsistent. This [...] Read more.

Water literacy, or the culmination of water-related knowledge, attitudes and behaviors, is a relatively new field of study with growing importance for sustainable water management and social water equity. However, its definition and use across existing literature are varied and often inconsistent. This paper seeks to synthesize and streamline the conception of water literacy. We conducted a systematic review of literature that defines or describes in detail either “water literacy” or “watershed literacy”. From this, we suggest a new holistic framework for water literacy to guide a more inclusive, relevant use of the concept. We utilized the framework to examine existing surveys and studies of water knowledge, attitudes and behaviors in both student and adult populations, and summarized water literacy levels and knowledge gaps that exist around the world. To address knowledge gaps, we suggest using a suite of approaches drawn from the published literature, including enhanced visuals, place-based learning, interdisciplinary curricula, and reflective and iterative development of future water literacy initiatives. Full article

(This article belongs to the Special Issue Water Literacy and Education)

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24 pages, 1255 KiB

Open AccessEditor’s ChoiceReview

Addressing Challenges of Urban Water Management in Chinese Sponge Cities via Nature-Based Solutions

by Yunfei Qi, Faith Ka Shun Chan, Colin Thorne, Emily O’Donnell, Carlotta Quagliolo, Elena Comino, Alessandro Pezzoli, Lei Li, James Griffiths, Yanfang Sang and Meili Feng

Water 2020, 12(10), 2788; https://doi.org/10.3390/w12102788 - 8 Oct 2020

Cited by 79 | Viewed by 15320

Abstract

Urban flooding has become a serious issue in most Chinese cities due to rapid urbanization and extreme weather, as evidenced by severe events in Beijing (2012), Ningbo (2013), Guangzhou (2015), Wuhan (2016), Shenzhen (2019), and Chongqing (2020). The Chinese “Sponge City Program” (SCP), [...] Read more.

Urban flooding has become a serious issue in most Chinese cities due to rapid urbanization and extreme weather, as evidenced by severe events in Beijing (2012), Ningbo (2013), Guangzhou (2015), Wuhan (2016), Shenzhen (2019), and Chongqing (2020). The Chinese “Sponge City Program” (SCP), initiated in 2013 and adopted by 30 pilot cities, is developing solutions to manage urban flood risk, purify stormwater, and provide water storage opportunities for future usage. Emerging challenges to the continued implementation of Sponge Cities include (1) uncertainty regarding future hydrological conditions related to climate change projections, which complicates urban planning and designing infrastructure that will be fit for purpose over its intended operating life, and (2) the competing priorities of stakeholders and their reluctance to make trade-offs, which obstruct future investment in the SCP. Nature-Based Solutions (NBS) is an umbrella concept that emerged from Europe, which encourages the holistic idea of considering wider options that combine “Blue–Green” practices with traditional engineering to deliver “integrated systems of Blue–Green–Grey infrastructure”. NBS includes interventions making use of natural processes and ecosystem services for functional purposes, and this could help to improve current pilot SCP practices. This manuscript reviews the development of the SCP, focusing on its construction and design aspects, and discusses how approaches using NBS could be included in the SCP to tackle not only urban water challenges but also a wide range of social and environmental challenges, including human health, pollution (via nutrients, metals, sediments, plastics, etc.), flood risk, and biodiversity. Full article

(This article belongs to the Special Issue Integrated Approaches to Manage Floods in Urban Environments)

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20 pages, 3299 KiB

Open AccessEditor’s ChoiceArticle

Estimating Human Impacts on Soil Erosion Considering Different Hillslope Inclinations and Land Uses in the Coastal Region of Syria

by Safwan Mohammed, Hazem G. Abdo, Szilard Szabo, Quoc Bao Pham, Imre J. Holb, Nguyen Thi Thuy Linh, Duong Tran Anh, Karam Alsafadi, Ali Mokhtar, Issa Kbibo, Jihad Ibrahim and Jesus Rodrigo-Comino

Water 2020, 12(10), 2786; https://doi.org/10.3390/w12102786 - 7 Oct 2020

Cited by 42 | Viewed by 4989

Abstract

Soils in the coastal region of Syria (CRoS) are one of the most fragile components of natural ecosystems. However, they are adversely affected by water erosion processes after extreme land cover modifications such as wildfires or intensive agricultural activities. The main goal of [...] Read more.

Soils in the coastal region of Syria (CRoS) are one of the most fragile components of natural ecosystems. However, they are adversely affected by water erosion processes after extreme land cover modifications such as wildfires or intensive agricultural activities. The main goal of this research was to clarify the dynamic interaction between erosion processes and different ecosystem components (inclination, land cover/land use, and rainy storms) along with the vulnerable territory of the CRoS. Experiments were carried out in five different locations using a total of 15 erosion plots. Soil loss and runoff were quantified in each experimental plot, considering different inclinations and land uses (agricultural land (AG), burnt forest (BF), forest/control plot (F)). Observed runoff and soil loss varied greatly according to both inclination and land cover after 750 mm of rainfall (26 events). In the cultivated areas, the average soil water erosion ranged between 0.14 ± 0.07 and 0.74 ± 0.33 kg/m²; in the BF plots, mean soil erosion ranged between 0.03 ± 0.01 and 0.24 ± 0.10 kg/m². The lowest amount of erosion was recorded in the F plots where the erosion ranged between 0.1 ± 0.001 and 0.07 ± 0.03 kg/m². Interestingly, the General Linear Model revealed that all factors (i.e., inclination, rainfall and land use) had a significant (p < 0.001) effect on the soil loss. We concluded that human activities greatly influenced soil erosion rates, being higher in the AG lands, followed by BF and F. Therefore, the current study could be very useful to policymakers and planners for proposing immediate conservation or restoration plans in a less studied area which has been shown to be vulnerable to soil erosion processes. Full article

(This article belongs to the Special Issue Soil–Water Conservation, Erosion, and Landslide)

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24 pages, 1697 KiB

Open AccessEditor’s ChoiceReview

Water and Land as Shared Resources for Agriculture and Aquaculture: Insights from Asia

by Steven G. Pueppke, Sabir Nurtazin and Weixin Ou

Water 2020, 12(10), 2787; https://doi.org/10.3390/w12102787 - 7 Oct 2020

Cited by 15 | Viewed by 11084

Abstract

Although agriculture and aquaculture depend on access to increasingly scarce, shared water resources to produce food for human consumption, they are most often considered in isolation. We argue that they should be treated as integrated components of a single complex system that is [...] Read more.

Although agriculture and aquaculture depend on access to increasingly scarce, shared water resources to produce food for human consumption, they are most often considered in isolation. We argue that they should be treated as integrated components of a single complex system that is prone to direct or indirect tradeoffs that should be avoided while also being amenable to synergies that should be sought. Direct tradeoffs such as competition for space or the pollution of shared water resources usually occur when the footprints of agriculture and aquaculture overlap or when the two practices coexist in close proximity to one another. Interactions can be modulated by factors such as hydropower infrastructure and short-term economic incentives, both of which are known to disrupt the balance between aquaculture and agriculture. Indirect tradeoffs, on the other hand, play out across distances, i.e., when agricultural food sources are diverted to feed animals in aquaculture. Synergies are associated with the culture of aquatic organisms in rice paddies and irrigation waters, seasonal rotations of crop cultivation with aquaculture, and various forms of integrated agriculture–aquaculture (IAA), including jitang, a highly developed variant of pond-dike IAA. Policy decisions, socioeconomic considerations, and technology warrant increased scrutiny as determinants of tradeoffs and synergies. Priority issues for the future include guiding the expansion of aquaculture from its traditional base in Asia, taking advantage of the heterogeneity that exists within both agricultural and aquaculture systems, the development of additional metrics of tradeoffs and synergies, and adapting to the effects of climate change. Full article

(This article belongs to the Special Issue Feature Papers of Water, Agriculture and Aquaculture)

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15 pages, 2966 KiB

Open AccessEditor’s ChoiceArticle

Metal Distribution and Sediment Quality Variation across Sediment Depths of a Subtropical Ramsar Declared Wetland

by Tatenda Dalu, Rolindela Tshivhase, Ross N. Cuthbert, Florence M. Murungweni and Ryan J. Wasserman

Water 2020, 12(10), 2779; https://doi.org/10.3390/w12102779 - 6 Oct 2020

Cited by 20 | Viewed by 3014

Abstract

The study of wetlands is particularly important as these systems act as natural water purifiers and thus can act as sinks for contaminated particles. Wetland sediments are important as they provide an indication of potential contamination across temporal and spatial scales. The current [...] Read more.

The study of wetlands is particularly important as these systems act as natural water purifiers and thus can act as sinks for contaminated particles. Wetland sediments are important as they provide an indication of potential contamination across temporal and spatial scales. The current study aimed to investigate the distributions of selected metals and nutrients in different sites in relation to sediment depth, and identify relationships among sediment metals. Significant differences in nutrient (i.e., N, P) and metal (i.e., K, Mg, Na, Fe, Cu, B) concentrations were found across study sites, whereas nutrients (i.e., N, P) and metals (i.e., Ca, Mg, Fe, Cu, Zn) were significantly different with sediment depths. When compared against Canadian sediment standards, most of the assessed metals were within the “no effect” level across the different sites and depths. The K, Ca, and Mg concentration showed extreme contamination across all sites and depths. The enrichment factor values for K, Ca, and Mg showed extremely high enrichment levels for all sites and sediment depths. The Na, Mn, Fe, Cu, Zn, and B concentration showed mostly background enrichment levels. All sediments across the different sites and sediment depths indicated deterioration of sediment quality. Pearson correlations suggest that most metals might have originated in a similar source as that of Mn and B, owing to a lack of significant differences. These results provide baseline information for the general management of the Nylsvley Wetland in relation to sediment metal pollution. The specific sources of metal contaminants also require further elucidation to further inform management efforts. Full article

(This article belongs to the Special Issue Geochemistry of Water and Sediment)

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22 pages, 9722 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Assessment of Surface Hydrological Connectivity in an Ungauged Multi-Lake System with a Combined Approach Using Geostatistics and Spaceborne SAR Observations

by Yueqing Chen, Lili Wu, Guangxin Zhang, Y. Jun Xu, Zhiqiang Tan and Sijia Qiao

Water 2020, 12(10), 2780; https://doi.org/10.3390/w12102780 - 6 Oct 2020

Cited by 3 | Viewed by 2828

Abstract

Connectivity metrics for surface water are important for predicting floods and droughts, and improving water management for human use and ecological integrity at the landscape scale. The integrated use of synthetic aperture radar (SAR) observations and geostatistics approach can be useful for developing [...] Read more.

Connectivity metrics for surface water are important for predicting floods and droughts, and improving water management for human use and ecological integrity at the landscape scale. The integrated use of synthetic aperture radar (SAR) observations and geostatistics approach can be useful for developing and quantifying these metrics and their changes, including geostatistical connectivity function (GCF), maximum distance of connection (MDC), surface water extent (SWE), and connection frequency. In this study, we conducted a geostatistical analysis based on 52 wet and dry binary state (i.e., water and non-water) rasters derived from Sentinel-1 A/B GRD products acquired from 2015 to 2019 for China’s Momoge National Nature Reserve to investigate applicability and dynamics of the hydrologic connectivity metrics in an ungauged (i.e., data such as flow and water level are scarce) multi-lake system. We found: (1) generally, the change of GCF in North–South and Northeast–Southwest directions was greater than that in the West–East and Northwest–Southeast directions; (2) MDC had a threshold effect, generally at most 25 km along the W–E, NW–SE and NE–SW directions, and at most 45 km along the N–S direction; (3) the flow paths between lakes are diverse, including channelized flow, diffusive overbank flow, over-road flow and “fill-and-merge”; (4) generally, the values of the three surface hydrological connectivity indicators (i.e., the MDC, the SWE, and the conneciton frequency) all increased from May to August, and decreased from August to October; (5) generally, the closer the distance between the lakes, the greater the connection frequency, but it is also affected by the dam and road barrier. The study demonstrates the usefulness of the geostatistical method combining Sentinel-1 SAR image analysis in quantifying surface hydrological connectivity in an ungagged area. This approach should be applicable for other geographical regions, in order help resource managers and policymakers identify changes in surface hydrological connectivity, as well as address potential impacts of these changes on water resources for human use and/or ecological integrity at the landscape level. Full article

(This article belongs to the Special Issue Wetland Ecohydrology and Water Resource Management)

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19 pages, 4351 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Analysis of Water Quality Using Multivariate Statistical Techniques and the Water Quality Identification Index for the Qinhuai River Basin, East China

by Xiaoxue Ma, Lachun Wang, Hong Yang, Na Li and Chang Gong

Water 2020, 12(10), 2764; https://doi.org/10.3390/w12102764 - 4 Oct 2020

Cited by 43 | Viewed by 5411

Abstract

Monitoring water quality is indispensable for the identification of threats to water environment and later management of water resources. Accurate monitoring and assessment of water quality have been long-term challenges. In this study, multivariate statistical techniques (MST) and water quality identification index (WQII) [...] Read more.

Monitoring water quality is indispensable for the identification of threats to water environment and later management of water resources. Accurate monitoring and assessment of water quality have been long-term challenges. In this study, multivariate statistical techniques (MST) and water quality identification index (WQII) were applied to analyze spatiotemporal variation in water quality and determine the major pollution sources in the Qinhuai River, East China. A rotated principal component analysis (PCA) identified three potential pollution sources during the wet season (mixed pollution, physicochemical, and nonpoint sources of nutrients) and the dry season (nutrient, primary environmental, and organic sources) and they explained 81.14% of the total variances in the wet season and 78.42% of total variances in the dry season. The result of redundancy analysis (RDA) showed that population density, urbanization, and wastewater discharge are the main sources of organic pollution, while agricultural fertilizer consumption and industrial wastewater discharge are the main sources of nutrients such as nitrogen and phosphorus. The water quality of the Qinhuai River basin was determined to be mainly Class III (slightly polluted) and Class IV (moderately polluted) based on WQII. Temporally, the change trend of WQII showed that water quality gradually deteriorated between 1990 and 2005, improved between 2006 and 2010, and then deteriorated again. Spatially, the WQII distribution map showed that areas with more developed urbanization were relatively more polluted. Our results show that MST and WQII are useful tools to help the public and decision makers to evaluate the water quality of aquatic environment. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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26 pages, 1925 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Institutional Framework for Modeling Water Availability and Allocation

by Ralph A. Wurbs

Water 2020, 12(10), 2767; https://doi.org/10.3390/w12102767 - 4 Oct 2020

Cited by 11 | Viewed by 3697

Abstract

Effective water resources management requires assessments of water availability within a framework of complex institutions and infrastructure employed to manage extremely variable stream flow shared by numerous, often competing, water users and diverse types of use. The Water Rights Analysis Package (WRAP) modeling [...] Read more.

Effective water resources management requires assessments of water availability within a framework of complex institutions and infrastructure employed to manage extremely variable stream flow shared by numerous, often competing, water users and diverse types of use. The Water Rights Analysis Package (WRAP) modeling system is fundamental to water allocation and planning in the state of Texas in the United States. Integration of environmental flow standards into both the modeling system and comprehensive statewide water management is a high priority for continuing research and development. The public domain WRAP software and documentation are generalized for application any place in the world. Lessons learned in developing and implementing the modeling system in Texas are relevant worldwide. The modeling system combines: (1) detailed simulation of water right systems, interstate compacts, international treaties, federal/state/local agreements, and operations of storage and conveyance facilities, (2) simulation of river system hydrology, and (3) statistical frequency and reliability analyses. The continually evolving modeling system has been implemented in Texas by a water management community that includes the state legislature, planning and regulatory agencies, river authorities, water districts, cities, industries, engineering consulting firms, and university researchers. The shared modeling system contributes significantly to integration of water allocation, planning, system operations, and research. Full article

(This article belongs to the Special Issue Feature Papers of Water Resources Management, Policy and Governance)

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17 pages, 6318 KiB

Open AccessEditor’s ChoiceReview

Nutrient Retention in Ecologically Functional Floodplains: A Review

by Brad A. Gordon, Olivia Dorothy and Christian F. Lenhart

Water 2020, 12(10), 2762; https://doi.org/10.3390/w12102762 - 4 Oct 2020

Cited by 30 | Viewed by 11190

Abstract

Nutrient loads in fresh and coastal waters continue to lead to harmful algal blooms across the globe. Historically, floodplains—low-lying areas adjacent to streams and rivers that become inundated during high-flow events—would have been nutrient deposition and/or removal sites within riparian corridors, but many [...] Read more.

Nutrient loads in fresh and coastal waters continue to lead to harmful algal blooms across the globe. Historically, floodplains—low-lying areas adjacent to streams and rivers that become inundated during high-flow events—would have been nutrient deposition and/or removal sites within riparian corridors, but many floodplains have been developed and/or disconnected. This review synthesizes literature and data available from field studies quantifying nitrogen (N) and phosphorus (P) removal within floodplains across North America and Europe to determine how effective floodplain restoration is at removing nutrients. The mean removal of nitrate-N (NO₃⁻-N), the primary form of N in floodplain studies, was 200 (SD = 198) kg-N ha⁻¹ year⁻¹, and of total or particulate P was 21.0 (SD = 31.4) kg-P ha⁻¹ year⁻¹. Based on the literature, more effective designs of restored floodplains should include optimal hydraulic load, permanent wetlands, geomorphic diversity, and dense vegetation. Floodplain restorations along waterways with higher nutrient concentrations could lead to a more effective investment for nutrient removal. Overall, restoring and reconnecting floodplains throughout watersheds is a viable and effective means of removing nutrients while also restoring the many other benefits that floodplains provide. Full article

(This article belongs to the Special Issue River Floodplain Restoration)

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23 pages, 7848 KiB

Open AccessEditor’s ChoiceArticle

A Modified HYDRUS Model for Simulating PFAS Transport in the Vadose Zone

by Jeff Allen Kai Silva, Jiří Šimůnek and John E. McCray

Water 2020, 12(10), 2758; https://doi.org/10.3390/w12102758 - 3 Oct 2020

Cited by 67 | Viewed by 7752

Abstract

The HYDRUS unsaturated flow and transport model was modified to simulate the effects of non-linear air-water interfacial (AWI) adsorption, solution surface tension-induced flow, and variable solution viscosity on the unsaturated transport of per- and polyfluoroalkyl substances (PFAS) within the vadose zone. These modifications [...] Read more.

The HYDRUS unsaturated flow and transport model was modified to simulate the effects of non-linear air-water interfacial (AWI) adsorption, solution surface tension-induced flow, and variable solution viscosity on the unsaturated transport of per- and polyfluoroalkyl substances (PFAS) within the vadose zone. These modifications were made and completed between March 2019 and May 2019, and were implemented into both the one-dimensional (1D) and two-dimensional (2D) versions of HYDRUS. Herein, the model modifications are described and validated against the available literature-derived PFAS transport data (i.e., 1D experimental column transport data). The results of both 1D and 2D example simulations are presented to highlight the function and utility of the model to capture the dynamic and transient nature of the temporally and spatially variable interfacial area of the AWI (

A_{a w}

) as it changes with soil moisture content (

Θ_{w}

) and how it affects PFAS unsaturated transport. Specifically, the simulated examples show that while AWI adsorption of PFAS can be a significant source of retention within the vadose zone, it is not always the dominant source of retention. The contribution of solid-phase sorption can be considerable in many PFAS-contaminated vadose zones. How the selection of an appropriate

A_{a w} (Θ_{w})

function can impact PFAS transport and how both mechanisms contribute to PFAS mass flux to an underlying groundwater source is also demonstrated. Finally, the effects of soil textural heterogeneities on PFAS unsaturated transport are demonstrated in the results of both 1D and 2D example simulations. Full article

(This article belongs to the Special Issue Contaminant Transport and Fate)

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19 pages, 5115 KiB

Open AccessEditor’s ChoiceArticle

Impacts of Extreme Weather Events on Bacterial Community Composition of a Temperate Humic Lake

by Alexa Hoke, Jason Woodhouse, Luca Zoccarato, Valerie McCarthy, Elvira de Eyto, Maria Calderó-Pascual, Ewan Geffroy, Mary Dillane, Hans-Peter Grossart and Eleanor Jennings

Water 2020, 12(10), 2757; https://doi.org/10.3390/w12102757 - 3 Oct 2020

Cited by 9 | Viewed by 3755

Abstract

Extreme weather events are projected to increase in frequency and intensity as climate change continues. Heterotrophic bacteria play a critical role in lake ecosystems, yet little research has been done to determine how they are affected by such extremes. The purpose of this [...] Read more.

Extreme weather events are projected to increase in frequency and intensity as climate change continues. Heterotrophic bacteria play a critical role in lake ecosystems, yet little research has been done to determine how they are affected by such extremes. The purpose of this study was to use high-throughput sequencing to explore the bacterial community composition of a humic oligotrophic lake on the North Atlantic Irish coast and to assess the impacts on composition dynamics related to extreme weather events. Samples for sequencing were collected from Lough Feeagh on a fortnightly basis from April to November 2018. Filtration was used to separate free-living and particle-associated bacterial communities and amplicon sequencing was performed for the 16S rRNA V4 region. Two named storms, six high discharge events, and one drought period occurred during the sampling period. These events had variable, context-dependent effects on bacterial communities in Lough Feeagh. The particle-associated community was found to be more likely to respond to physical changes, such as mixing, while the free-living population responded to changes in nutrient and carbon concentrations. Generally, however, the high stability of the bacterial community observed in Lough Feeagh suggests that the bacterial community is relatively resilient to extreme weather events. Full article

(This article belongs to the Special Issue Effect of Extreme Climate Events on Lake Ecosystems)

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27 pages, 3881 KiB

Open AccessEditor’s ChoiceReview

Recent Advancements in the Removal of Cyanotoxins from Water Using Conventional and Modified Adsorbents—A Contemporary Review

by Tauqeer Abbas, George William Kajjumba, Meena Ejjada, Sayeda Ummeh Masrura, Erica J. Marti, Eakalak Khan and Tammy L. Jones-Lepp

Water 2020, 12(10), 2756; https://doi.org/10.3390/w12102756 - 3 Oct 2020

Cited by 38 | Viewed by 5182

Abstract

The prevalence of cyanobacteria is increasing in freshwaters due to climate change, eutrophication, and their ability to adapt and thrive in changing environmental conditions. In response to various environmental pressures, they produce toxins known as cyanotoxins, which impair water quality significantly. Prolonged human [...] Read more.

The prevalence of cyanobacteria is increasing in freshwaters due to climate change, eutrophication, and their ability to adapt and thrive in changing environmental conditions. In response to various environmental pressures, they produce toxins known as cyanotoxins, which impair water quality significantly. Prolonged human exposure to cyanotoxins, such as microcystins, cylindrospermopsin, saxitoxins, and anatoxin through drinking water can cause severe health effects. Conventional water treatment processes are not effective in removing these cyanotoxins in water and advanced water treatment processes are often used instead. Among the advanced water treatment methods, adsorption is advantageous compared to other methods because of its affordability and design simplicity for cyanotoxins removal. This article provides a current review of recent developments in cyanotoxin removal using both conventional and modified adsorbents. Given the different cyanotoxins removal capacities and cost of conventional and modified adsorbents, a future outlook, as well as suggestions are provided to achieve optimal cyanotoxin removal through adsorption. Full article

(This article belongs to the Special Issue Environmental Chemistry of Water Quality Monitoring)

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19 pages, 2128 KiB

Open AccessEditor’s ChoiceArticle

Heavy Metals in Wastewater and Sewage Sludge from Selected Municipal Treatment Plants in Eastern Cape Province, South Africa

by Mojeed A. Agoro, Abiodun O. Adeniji, Martins A. Adefisoye and Omobola O. Okoh

Water 2020, 12(10), 2746; https://doi.org/10.3390/w12102746 - 1 Oct 2020

Cited by 176 | Viewed by 21226

Abstract

This study assessed the distribution of five heavy metals (Cd, Pb, Cu, Zn, and Fe) across the various stages of treatment in three selected sewage treatment facilities and their receiving waterbodies in the Eastern Cape Province, South Africa. Aqueous and solid (sludge) samples [...] Read more.

This study assessed the distribution of five heavy metals (Cd, Pb, Cu, Zn, and Fe) across the various stages of treatment in three selected sewage treatment facilities and their receiving waterbodies in the Eastern Cape Province, South Africa. Aqueous and solid (sludge) samples were collected monthly from September 2015 to February 2016. Quantitation was achieved by atomic absorption spectrometry after necessary sample preparations. Concentrations of heavy metal cations in the sludge generally varied from <DL (below detection limit) to 1.17 mg kg⁻¹, <DL to 0.14 mg kg⁻¹, 27.588 to 69.789 mg kg⁻¹, and <DL to 0.099 mg kg⁻¹ for Cu, Cd, Fe and Pb; while Zn was below detection all through. Similarly, the levels of Cu, Cd, and Fe in the influents, effluents, upstream and downstream across the three plants ranged from <DL–6.588 mg L⁻¹, <DL–0.636 mg L⁻¹, <DL–0.878 mg L⁻¹ and <DL–0.711 mg L⁻¹, respectively; Zn and Pb were less than DL in all the matrices and study locations. All the contaminants were below hazardous levels in all the sludge and aqueous samples except Cd which was higher in effluents and surface waters across the board. Wastewater Treatment Plant (WWTP)-A exhibited better removal capacity for Fe (86.6%), compared to WWTP-B (34.7%) and WWTP-C (56.9%). However, the removal of Cu and Zn was very poor in all the treatment facilities studied. Carcinogenic and non-carcinogenic risks evaluated were sufficiently low. This suggests that the levels of contamination, even with respect to Cd, was minimal. Nevertheless, efforts should be made to keep the concentrations of these contaminants at levels safe for humans and aquatic organisms. Furthermore, the use of the effluents from these facilities for irrigation should be discouraged to prevent unnecessary build-up of metals in the soil and plants grown with such, as well as subsequent bioaccumulation and biomagnification in the food chain. Full article

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

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22 pages, 5524 KiB

Open AccessEditor’s ChoiceArticle

Investigating an Innovative Sea-Based Strategy to Mitigate Coastal City Flood Disasters and Its Feasibility Study for Brisbane, Australia

by Usman Khalil, Shu-Qing Yang, Muttucumaru Sivakumar, Keith Enever, Mariam Sajid and Muhammad Zain Bin Riaz

Water 2020, 12(10), 2744; https://doi.org/10.3390/w12102744 - 30 Sep 2020

Cited by 6 | Viewed by 3577

Abstract

This study examines an innovative Coastal Reservoir (CR) technique as a feasible solution for flood adaptation and mitigation in the Brisbane River Estuary (BRE), Australia, which is vulnerable to coastal flooding. The study analysed the operation of a CR by using the MIKE [...] Read more.

This study examines an innovative Coastal Reservoir (CR) technique as a feasible solution for flood adaptation and mitigation in the Brisbane River Estuary (BRE), Australia, which is vulnerable to coastal flooding. The study analysed the operation of a CR by using the MIKE 21 hydrodynamic modelling package. The 2D hydrodynamic model was calibrated and validated for the 2013 and 2011 flood events respectively, with a Nash-Sutcliffe coefficient (E_ns) between 0.87 to 0.97 at all gauges. River right branch widening and dredging produced a 0.16 m reduction in water level at the Brisbane city gauge. The results show that by suitable gate operation of CR, the 2011 flood normal observed level of 4.46 m, with reference to the Australian Height Datum (AHD) at Brisbane city, could have been reduced to 3.88 m AHD, while under the improved management operation of the Wivenhoe Dam, the flood level could be lowered to 4 m AHD at Brisbane city, which could have been reduced with CR to 2.87 m AHD with an overall water level reduction below the maximum flood level. The results demonstrated that the innovative use of a CR could considerably decrease the overall flood peak and lessen flood severity in the coastal city of Brisbane. Full article

(This article belongs to the Special Issue Hydrodynamics in Estuaries and Coast: Analysis and Modeling)

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27 pages, 16227 KiB

Open AccessEditor’s ChoiceArticle

Integrating C- and L-Band SAR Imagery for Detailed Flood Monitoring of Remote Vegetated Areas

by Alberto Refice, Marina Zingaro, Annarita D’Addabbo and Marco Chini

Water 2020, 12(10), 2745; https://doi.org/10.3390/w12102745 - 30 Sep 2020

Cited by 26 | Viewed by 5336

Abstract

Flood detection and monitoring is increasingly important, especially on remote areas such as African tropical river basins, where ground investigations are difficult. We present an experiment aimed at integrating multi-temporal and multi-source data from the Sentinel-1 and ALOS 2 synthetic aperture radar (SAR) [...] Read more.

Flood detection and monitoring is increasingly important, especially on remote areas such as African tropical river basins, where ground investigations are difficult. We present an experiment aimed at integrating multi-temporal and multi-source data from the Sentinel-1 and ALOS 2 synthetic aperture radar (SAR) sensors, operating in C band, VV polarization, and L band, HH and HV polarizations, respectively. Information from the globally available CORINE land cover dataset, derived over Africa from the Proba V satellite, and available publicly at the resolution of 100 m, is also exploited. Integrated multi-frequency, multi-temporal, and multi-polarizations analysis allows highlighting different drying dynamics for floodwater over various land cover classes, such as herbaceous vegetation, wetlands, and forests. They also enable detection of different scattering mechanisms, such as double bounce interaction of vegetation stems and trunks with underlying floodwater, giving precious information about the distribution of flooded areas among the different ground cover types present on the site. The approach is validated through visual analysis from Google Earth^TM imagery. This kind of integrated analysis, exploiting multi-source remote sensing to partially make up for the unavailability of reliable ground truth, is expected to assume increasing importance as constellations of satellites, observing the Earth in different electromagnetic radiation bands, will be available. Full article

(This article belongs to the Special Issue Improving Flood Detection and Monitoring through Remote Sensing)

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27 pages, 8537 KiB

Open AccessEditor’s ChoiceArticle

Simulating the Impact of Climate Change with Different Reservoir Operating Strategies on Sedimentation of the Mangla Reservoir, Northern Pakistan

by Muhammad Adnan Khan, Jürgen Stamm and Sajjad Haider

Water 2020, 12(10), 2736; https://doi.org/10.3390/w12102736 - 30 Sep 2020

Cited by 12 | Viewed by 4376

Abstract

Reservoir sedimentation reduces the gross storage capacity of dams and also negatively impacts turbine functioning, posing a danger to turbine inlets. When the sediment delta approaches the dam, further concerns arise regarding sediments passing through turbine intakes, blades abrasion due to increased silt/sand [...] Read more.

Reservoir sedimentation reduces the gross storage capacity of dams and also negatively impacts turbine functioning, posing a danger to turbine inlets. When the sediment delta approaches the dam, further concerns arise regarding sediments passing through turbine intakes, blades abrasion due to increased silt/sand concentration, choking of outlets, and dam safety. Thus, slowing down the delta advance rate is a worthy goal from a dam manager’s viewpoint. These problems can be solved through a flexible reservoir operation strategy that prioritize sediment deposition further away from the dam face. As a case study, the Mangla Reservoir in Pakistan is selected to elaborate the operational strategy. The methodology rests upon usage of a 1D sediment transport model to quantify the impact of different reservoir operating strategies on sedimentation. Further, in order to assess the long-term effect of a changing climate, a global climate model under representative concentration pathways scenarios 4.5 and 8.5 for the 21st century is used. The reduction of uncertainty in the suspended sediments concentration is achieved by employing an artificial neural networking technique. Moreover, a sensitivity analysis focused on estimating the impact of various parameters on sediment transport modelling was conducted. The results show that a gradual increase in the reservoir minimum operating level slows down the delta movement rate and the bed level close to the dam. However, it may compromise the downstream irrigation demand during periods of high water demand. The findings may help the reservoir managers to improve the reservoir operation rules and ultimately support the objective of a sustainable reservoir use for the societal benefit. Full article

(This article belongs to the Section Water Erosion and Sediment Transport)

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17 pages, 5305 KiB

Open AccessEditor’s ChoiceArticle

Infiltration Characteristics and Spatiotemporal Distribution of Soil Moisture in Layered Soil under Vertical Tube Irrigation

by Cheng Wang, Dan Bai, Yibo Li, Xinduan Wang, Zhen Pei and Zuochao Dong

Water 2020, 12(10), 2725; https://doi.org/10.3390/w12102725 - 29 Sep 2020

Cited by 4 | Viewed by 2646

Abstract

The limited quantity of irrigation water in Xinjiang has hindered agricultural development in the region and water-saving irrigation technologies are crucial to addressing this water shortage. Vertical tube irrigation, a type of subsurface irrigation, is a new water-efficient technology. In this study, field [...] Read more.

The limited quantity of irrigation water in Xinjiang has hindered agricultural development in the region and water-saving irrigation technologies are crucial to addressing this water shortage. Vertical tube irrigation, a type of subsurface irrigation, is a new water-efficient technology. In this study, field and laboratory experiments were conducted to analyze (1) the infiltration characteristics and spatiotemporal distribution of moisture in layered soil and (2) the water-saving mechanism of vertical tube irrigation. In the field experiments, we analyzed jujube yield, irrigation water productivity (IWP), and soil moisture in the jujube root zone. In the laboratory irrigation experiments, two soil types (silty and sandy loam) were selected to investigate homogeneous and layered soil, respectively. Cumulative infiltration, wetting body, and soil water moisture distribution were also analyzed. Relative to surface drip irrigation, vertical tube irrigation resulted in slightly lower jujube yields but higher savings in water use (47–68%) and improved IWP. The laboratory experiments demonstrated that layered soil had less cumulative infiltration, a larger ellipsoid wetted body, slower vertical wetting front migration (hindered by layer interface), and faster horizontal wetting front migration than homogenous soil had. The irrigation amount for vertical tube irrigation decreased in layered soil, and water content increased at the layer interface. Vertical tube irrigation in layered soil facilitates the retention of water in the root zone, prevents deep leakage, reduces irrigation amount, and improves the IWP of jujube trees. This study aids the popularization and application of vertical tube irrigation technology. Full article

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

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15 pages, 1774 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Aggregate-Pouring Sequence on the Efficiency of Plugging Inundated Tunnels through Drilling Ground Boreholes

by Xiangming Jiang, Shuang Hui, Wanghua Sui, Zhiyuan Shi and Jiahao Wang

Water 2020, 12(10), 2698; https://doi.org/10.3390/w12102698 - 27 Sep 2020

Cited by 3 | Viewed by 1987

Abstract

This paper presents an experimental and field investigation on the efficiency of plugging by pouring aggregate in different sequences through multiple boreholes in a tunnel with flowing water. There have been controversies surrounding the selection of the pouring order for different particle sizes [...] Read more.

This paper presents an experimental and field investigation on the efficiency of plugging by pouring aggregate in different sequences through multiple boreholes in a tunnel with flowing water. There have been controversies surrounding the selection of the pouring order for different particle sizes of aggregates and the order in different boreholes. A visualized experimental setup is used to investigate the influence of the pouring orders on the efficiency of plugging through multiple boreholes under the flowing-water condition. A case study of the salvage of a flooded mine using ground directional boreholes was investigated and compared with the experimental results. The water-pressure difference at the aggregate-capping moment, when fine aggregate was poured first and coarse aggregate later, was relatively small, compared to that when fine aggregate was poured upstream and coarse aggregate, downstream. The result implies that the efficiency of plugging with the order of pouring fine aggregate first and coarse aggregate later in different boreholes is better than that with the order of pouring fine aggregate upstream and coarse aggregate downstream. When the poured aggregate is about to be capped, increasing the pouring intensity with the same or a larger particle size is more conducive to capping. The case study shows that pouring fine materials in the early stage reduced the cross-sectional area; in the later stage, the aggregate particle size was gradually increased, which can be helpful in forming an effective water-barrier section in the tunnel. The pouring of aggregate provided a base for cement grouting to form a water-plug section with a length of 106 m, resulting in a sealing efficiency of 100% for the case. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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18 pages, 3805 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Variation in Phytoplankton Community Driven by Environmental Factors in the Northern East China Sea

by Yejin Kim, Seok-Hyun Youn, Hyun Ju Oh, Jae Joong Kang, Jae Hyung Lee, Dabin Lee, Kwanwoo Kim, Hyo Keun Jang, Junbeom Lee and Sang Heon Lee

Water 2020, 12(10), 2695; https://doi.org/10.3390/w12102695 - 26 Sep 2020

Cited by 14 | Viewed by 3975

Abstract

The East China Sea (ECS) is the largest marginal sea in the northern western Pacific Ocean. In comparison to various physical studies, little information on the seasonal patterns in community structure of phytoplankton is currently available. Based on high performance liquid chromatography (HPLC) [...] Read more.

The East China Sea (ECS) is the largest marginal sea in the northern western Pacific Ocean. In comparison to various physical studies, little information on the seasonal patterns in community structure of phytoplankton is currently available. Based on high performance liquid chromatography (HPLC) pigment analysis, spatiotemporal variations in phytoplankton community compositions were investigated in the northern ECS. Water temperature and salinity generally decreased toward the western part of the study area but warmer conditions in August led to strong vertical stratification of the water column. In general, major inorganic nutrient concentrations were considerably higher in the western part with a shallow water depth, and consistent with previous results, had no discernable vertical pattern during our observation period except in August. This study also revealed PO₄-limited environmental conditions in May and August. The monthly averaged integral chlorophyll-a concentration varied seasonally, highest (35.2 ± 20.22 mg m⁻²) in May and lowest (5.2 ± 2.54 mg m⁻²) in February. No distinct vertical differences in phytoplankton community compositions were observed for all the sampling seasons except in August when cyanobacteria predominated in the nutrient-deficient surface layer and diatoms prevailed at deep layer. Canonical correlation analysis results revealed that nutrient distribution and the water temperature were the major drivers of the vertical distribution of phytoplankton communities in August. Spatially, a noticeable difference in phytoplankton community structure between the eastern and western parts was observed in November with diatom domination in the western part and cyanobacteria domination in the eastern part, which were significantly (p < 0.01) correlated with water temperature, salinity, light conditions, and nutrient concentrations. Overall, the two major phytoplankton groups were diatoms (32.0%) and cyanobacteria (20.6%) in the northern ECS and the two groups were negatively correlated, which holds a significant ecological meaning under expected warming ocean conditions. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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12 pages, 1696 KiB

Open AccessEditor’s ChoiceReview

The Water Footprint of Global Food Production

by Mesfin M. Mekonnen and Winnie Gerbens-Leenes

Water 2020, 12(10), 2696; https://doi.org/10.3390/w12102696 - 26 Sep 2020

Cited by 115 | Viewed by 36623

Abstract

Agricultural production is the main consumer of water. Future population growth, income growth, and dietary shifts are expected to increase demand for water. The paper presents a brief review of the water footprint of crop production and the sustainability of the blue water [...] Read more.

Agricultural production is the main consumer of water. Future population growth, income growth, and dietary shifts are expected to increase demand for water. The paper presents a brief review of the water footprint of crop production and the sustainability of the blue water footprint. The estimated global consumptive (green plus blue) water footprint ranges from 5938 to 8508 km³/year. The water footprint is projected to increase by as much as 22% due to climate change and land use change by 2090. Approximately 57% of the global blue water footprint is shown to violate the environmental flow requirements. This calls for action to improve the sustainability of water and protect ecosystems that depend on it. Some of the measures include increasing water productivity, setting benchmarks, setting caps on the water footprint per river basin, shifting the diets to food items with low water requirements, and reducing food waste. Full article

(This article belongs to the Special Issue In Memory of Prof. Arjen Y. Hoekstra)

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23 pages, 3227 KiB

Open AccessEditor’s ChoiceArticle

Technical Efficiency of China’s Agriculture and Output Elasticity of Factors Based on Water Resources Utilization

by Shiliang Yang, Huimin Wang, Jinping Tong, Jianfeng Ma, Fan Zhang and Shijuan Wu

Water 2020, 12(10), 2691; https://doi.org/10.3390/w12102691 - 26 Sep 2020

Cited by 18 | Viewed by 3821

Abstract

A stochastic frontier approach (SFA) model of translog production function was constructed to analyze the growth effect of agricultural production factors on grain production in China. Under the condition of unchanged cultivated land, the agricultural labor, capital, and water were regarded as input [...] Read more.

A stochastic frontier approach (SFA) model of translog production function was constructed to analyze the growth effect of agricultural production factors on grain production in China. Under the condition of unchanged cultivated land, the agricultural labor, capital, and water were regarded as input elements of the agricultural production function. The maximum likelihood estimation (MLE) method was used to analyze the technical efficiency, output elasticity, substitution elasticity, and relative variability of grain production in China from 2004 to 2018. The results showed that: (1) For the technical efficiency and output elasticity of the input factors of grain production, there were significant differences in different provinces. For example, the water resource was insufficient in Beijing and Shanghai, but the output elasticity of water was high. Heilongjiang was rich in water and had high technical efficiency. For Xinjiang, water was sufficient, but its output elasticity was deficient and the technical efficiency didn’t increase. (2) The overall technical efficiency level was relatively low and was still declining year by year; the output elasticity of water was much greater than that of capital. There was still great potential for grain growth. (3) Optimizing resource allocation and controlling the appropriate ratio of input factors to develop grain production could achieve the maximum benefits. Finally, according to the empirical results, this paper put forward some practical policy suggestions for optimizing the allocation of input factors, especially water and capital, which can ultimately improve agricultural productivity by improving technical efficiency. Full article

(This article belongs to the Special Issue The Water-Energy-Food Nexus: Sustainable Development)

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18 pages, 4121 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Hybridised Artificial Neural Network Model with Slime Mould Algorithm: A Novel Methodology for Prediction of Urban Stochastic Water Demand

by Salah L. Zubaidi, Iqbal H. Abdulkareem, Khalid S. Hashim, Hussein Al-Bugharbee, Hussein Mohammed Ridha, Sadik Kamel Gharghan, Fuod F. Al-Qaim, Magomed Muradov, Patryk Kot and Rafid Al-Khaddar

Water 2020, 12(10), 2692; https://doi.org/10.3390/w12102692 - 26 Sep 2020

Cited by 114 | Viewed by 6620

Abstract

Urban water demand prediction based on climate change is always challenging for water utilities because of the uncertainty that results from a sudden rise in water demand due to stochastic patterns of climatic factors. For this purpose, a novel combined methodology including, firstly, [...] Read more.

Urban water demand prediction based on climate change is always challenging for water utilities because of the uncertainty that results from a sudden rise in water demand due to stochastic patterns of climatic factors. For this purpose, a novel combined methodology including, firstly, data pre-processing techniques were employed to decompose the time series of water and climatic factors by using empirical mode decomposition and identifying the best model input via tolerance to avoid multi-collinearity. Second, the artificial neural network (ANN) model was optimised by an up-to-date slime mould algorithm (SMA-ANN) to predict the medium term of the stochastic signal of monthly urban water demand. Ten climatic factors over 16 years were used to simulate the stochastic signal of water demand. The results reveal that SMA outperforms a multi-verse optimiser and backtracking search algorithm based on error scale. The performance of the hybrid model SMA-ANN is better than ANN (stand-alone) based on the range of statistical criteria. Generally, this methodology yields accurate results with a coefficient of determination of 0.9 and a mean absolute relative error of 0.001. This study can assist local water managers to efficiently manage the present water system and plan extensions to accommodate the increasing water demand. Full article

(This article belongs to the Special Issue Advanced Applications of Electrocoagulation in Water and Wastewater)

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17 pages, 3611 KiB

Open AccessEditor’s ChoiceArticle

Risk Assessment of China’s Water-Saving Contract Projects

by Qian Li, Ziheng Shangguan, Mark Yaolin Wang, Dengcai Yan, Ruizhi Zhai and Chuanhao Wen

Water 2020, 12(10), 2689; https://doi.org/10.3390/w12102689 - 25 Sep 2020

Cited by 12 | Viewed by 2965

Abstract

In order to alleviate the problem of water shortage, the Ministry of Water Resources of China proposed a Water-Saving Contract (WSC) project management model in 2014, which is similar to the Energy Performance Contract (EPC). In this context, this research aims to explore [...] Read more.

In order to alleviate the problem of water shortage, the Ministry of Water Resources of China proposed a Water-Saving Contract (WSC) project management model in 2014, which is similar to the Energy Performance Contract (EPC). In this context, this research aims to explore the applicability of China’s WSC projects by risk assessment, and to help promote WSC projects in China. Different from traditional risk assessment, this paper takes into account the uncertainty of the EPC project’s risks, and adopts the multielement connection degree set pair analysis to evaluate both the level and trend of the risks. The results show: (1) the overall risk of China’s WSC projects is low, so WSC projects are very suitable for promotion in China. However, the overall risk shows a trend of decelerated ascent, which shows that there are some potential high-risk factors in China’s WSC projects; (2) among the many risks of the WSC projects, audit risk, financing risk, and payment risk are at a high-risk level; market competition risk is at a medium-risk level; the remaining risks are at a low-risk level; (3) among the medium and high risks, audit risk, financing risk, and market competition risk have a trend of accelerated ascent, while payment risk has a trend of decelerated decline; in low risks, inflation risk has a trend of decelerated ascent, while the remaining risks have a trend of accelerated decline. Full article

(This article belongs to the Special Issue Water Resources Management Models for Policy Assessment)

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14 pages, 2214 KiB

Open AccessEditor’s ChoiceArticle

The Role of Sewer Network Structure on the Occurrence and Magnitude of Combined Sewer Overflows (CSOs)

by Julian D. Reyes-Silva, Emmanuel Bangura, Björn Helm, Jakob Benisch and Peter Krebs

Water 2020, 12(10), 2675; https://doi.org/10.3390/w12102675 - 24 Sep 2020

Cited by 12 | Viewed by 3665

Abstract

Combined sewer overflows (CSOs) prevent surges in sewer networks by releasing untreated wastewater into nearby water bodies during intense storm events. CSOs can have acute and detrimental impacts on the environment and thus need to be managed. Although several gray, green and hybrid [...] Read more.

Combined sewer overflows (CSOs) prevent surges in sewer networks by releasing untreated wastewater into nearby water bodies during intense storm events. CSOs can have acute and detrimental impacts on the environment and thus need to be managed. Although several gray, green and hybrid CSO mitigation measures have been studied, the influence of network structure on CSO occurrence is not yet systematically evaluated. This study focuses on evaluating how the variation of urban drainage network structure affects the frequency and magnitude of CSO events. As a study case, a sewer subnetwork in Dresden, Germany, where 11 CSOs are present, was selected. Scenarios corresponding to the structures with the lowest and with the highest number of possible connected pipes, are developed and evaluated using long-term hydrodynamic simulation. Results indicate that more meshed structures are associated to a decrease on the occurrence and magnitude of CSO. Event frequency reductions vary between 0% and 68%, while reduction of annual mean volumes and annual mean loads ranged between 0% and 87% and 0% and 92%. These rates were mainly related to the additional sewer storage capacity provided in the more meshed scenarios, following a sigmoidal behavior. However, increasing network connections causes investment costs, therefore optimization strategies for selecting intervention areas are needed. Furthermore, the present approach of reducing CSO frequency may provide a new gray solution that can be integrated in the development of hybrid mitigation strategies for the CSO management. Full article

(This article belongs to the Section Urban Water Management)

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21 pages, 1906 KiB

Open AccessEditor’s ChoiceReview

Environmental Flows in the Lower Ebro River and Delta: Current Status and Guidelines for a Holistic Approach

by Carles Ibáñez, Nuno Caiola and Oscar Belmar

Water 2020, 12(10), 2670; https://doi.org/10.3390/w12102670 - 24 Sep 2020

Cited by 17 | Viewed by 4156

Abstract

Deltas are a particular type of estuarine system in which the dependence on river flow (water, sediments and nutrients) is very strong, especially in river-dominated deltas such as the Mediterranean ones, but environmental flow (e-flow) proposals for deltaic systems are scarce. The Ebro [...] Read more.

Deltas are a particular type of estuarine system in which the dependence on river flow (water, sediments and nutrients) is very strong, especially in river-dominated deltas such as the Mediterranean ones, but environmental flow (e-flow) proposals for deltaic systems are scarce. The Ebro Delta is one of the largest wetland areas in the western Mediterranean and one of the most important estuarine systems in Europe. The aim of this paper is to review the state of the art regarding e-flows and to carry out a critical analysis of the proposals for the lower Ebro River and Delta, in order to highlight the possible environmental and socioeconomic impacts arising from the e-flow regime currently approved. Additionally, based on existing scientific information, methods to establish an e-flow regime that allows the maintenance of the main socio-ecological functions and values are discussed; including those functions and values for which not enough information is available. The study concludes that the currently approved e-flows are not suitable for maintaining most functions and values, as they would not prevent the proliferation of alien fish species and macrophytes in the river, the intrusion of the salt wedge in the estuary, the deficit of sediment/nutrient transport and the degradation of riparian habitats or the decline of coastal fisheries. Socioeconomic consequences on coastal fisheries, river navigation, salt water intrusion, sediment deficit, biodiversity, water quality, aquaculture and hydropower are also considered. Other e-flow proposals such as the proposed by the Catalan government would be more suitable to maintain the main socioecological functions and values of the lower Ebro River and Delta. Nevertheless, additional studies are needed to validate e-flows in some relevant aspects such as the capacity of the river to transport sediments to the delta to avoid coastal regression and mitigate the effects of sea level rise and subsidence, as well as the capacity of floods to control the spread of macrophytes. The lower Ebro River and delta is among the case studies where more quantitative and qualitative criteria to set e-flows with a holistic approach have been established. Full article

(This article belongs to the Special Issue Environmental Flows, Ecological Quality and Ecosystem Services)

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23 pages, 40132 KiB

Open AccessEditor’s ChoiceArticle

A Stepwise Approach to Beach Restoration at Calabaia Beach

by Mario Maiolo, Riccardo Alvise Mel and Salvatore Sinopoli

Water 2020, 12(10), 2677; https://doi.org/10.3390/w12102677 - 24 Sep 2020

Cited by 20 | Viewed by 4533

Abstract

Sea hazards are increasingly threatening worldwide coastal areas, which are among the most strategic resources of the Earth in supporting human population, economy and the environment. These hazards enhance erosion processes and flooding events, producing severe socio-economic impacts and posing a challenge to [...] Read more.

Sea hazards are increasingly threatening worldwide coastal areas, which are among the most strategic resources of the Earth in supporting human population, economy and the environment. These hazards enhance erosion processes and flooding events, producing severe socio-economic impacts and posing a challenge to ocean engineers and stakeholders in finding the optimal strategy to protect both the coastal communities and the health of the environment. The impact of coastal hazards is actually worsened not only by an enhancing rate of relative sea level rise and storminess driven by climate changes, but also by increasing urban pressure related to the development of the sea economy. With regard to larger environmental awareness and climate change adaptation needs, the present study focuses on a stepwise approach that supports the actions for coastal protection at Calabaia Beach, which is located in the Marine Experimental Station of Capo Tirone (Cosenza, Italy). These actions first aim to protect humans and coastal assets, then to restore the environment and the local habitat, overcoming the need for the emergency interventions carried out in the last decades and pointing out that healthy ecosystems are more productive and support a sustainable marine economy (“Blue Growth”). Full article

(This article belongs to the Special Issue Nature-Based Solutions for Coastal Engineering and Management)

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15 pages, 1160 KiB

Open AccessEditor’s ChoiceArticle

Cost Effectiveness of Ecosystem-Based Nutrient Targets—Findings from a Numerical Model for the Baltic Sea

by Ing-Marie Gren and Wondmagegn Tafesse Tirkaso

Water 2020, 12(10), 2679; https://doi.org/10.3390/w12102679 - 24 Sep 2020

Cited by 2 | Viewed by 1875

Abstract

An ecosystem-based management of a large sea can give heterogeneous nutrient load targets for different parts of the sea. Cost effective solutions to heterogeneous nutrient reductions targets based on ecological conditions are compared with the same overall nutrient reductions to the Baltic Sea. [...] Read more.

An ecosystem-based management of a large sea can give heterogeneous nutrient load targets for different parts of the sea. Cost effective solutions to heterogeneous nutrient reductions targets based on ecological conditions are compared with the same overall nutrient reductions to the Baltic Sea. To this end, a numerical programming model is used, which includes eight different nutrient abatement measures (fertilizer and livestock reduction, cultivation of catch crops, reduced airborne nitrogen emissions, improved cleaning at sewage treatment plants, construction of wetlands and buffer strips, and mussel farming) in 21 catchments of the Baltic Sea. The results indicate that the cost for the international agreement on maximum load targets to different marine basins amounts to 5.3 billion euro. This is more than twice as large as the cost for the same total nutrient load targets to the Baltic Sea without specific targets for the marine basins. However, the resulting nutrient loads to the different marine basins deviate from the basin targets where the loads are lower for some basins but can exceed that for one basin, Baltic Proper, by approximately 22 per cent. Whether or not the ecological costs and benefits from deviations in basin targets under the Baltic Sea targets exceed the excess abatement cost of 2.9 billion euro for achieving the marine basin targets remains to be verified. Full article

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

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17 pages, 3201 KiB

Open AccessEditor’s ChoiceReview

Climate Change Impacts on Water and Agriculture Sectors in Southern Africa: Threats and Opportunities for Sustainable Development

by Charles Nhemachena, Luxon Nhamo, Greenwell Matchaya, Charity R. Nhemachena, Binganidzo Muchara, Selma T. Karuaihe and Sylvester Mpandeli

Water 2020, 12(10), 2673; https://doi.org/10.3390/w12102673 - 24 Sep 2020

Cited by 94 | Viewed by 17097

Abstract

Agriculture remains important in driving economic transformation, sustainable livelihoods, and development in developing countries. This paper provides a comprehensive analysis and discussion of climate change impacts on water and agriculture sectors and implications for the attainment of developmental outcomes such as food security, [...] Read more.

Agriculture remains important in driving economic transformation, sustainable livelihoods, and development in developing countries. This paper provides a comprehensive analysis and discussion of climate change impacts on water and agriculture sectors and implications for the attainment of developmental outcomes such as food security, poverty reduction, and sustainable development in Southern Africa. The review gives policy messages for coping, adapting, and building resilience of water and agricultural production systems in the face of projected changes in climate and variability. The aim is to guide the region towards the achievement of the Sustainable Development Goals. Future projections for Southern Africa indicate reduced rainfall, increased temperatures, and high variability for the greater part of the region with severe reductions on the drier and marginal western parts. These impacts have profound implications for agriculture performance and contribution to national and regional developmental goals. The region is projected to experience reductions of between 15% and 50% in agricultural productivity, a scenario that would exacerbate food insecurity in the region. The challenge is to increase productivity on current arable land through efficient and sustainable management of available water and energy, and at the same time reducing pressure on the environment. Affordability and accessibility of innovative adaptation measures on water resources remain critical and these strategies should be part of broader sustainable development efforts. Overall, efforts to enhance agricultural productivity need to emphasise investments in sustainable management and use of water and energy resources in agriculture to achieve sustainable economic growth and livelihoods. Full article

(This article belongs to the Section Water, Agriculture and Aquaculture)

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19 pages, 2784 KiB

Open AccessEditor’s ChoiceArticle

Effect of Diverse Abiotic Conditions on the Structure and Biodiversity of Ichthyofauna in Small, Natural Water Bodies Located on Agricultural Lands

by Adam Brysiewicz, Przemysław Czerniejewski and Małgorzata Bonisławska

Water 2020, 12(10), 2674; https://doi.org/10.3390/w12102674 - 24 Sep 2020

Cited by 4 | Viewed by 3086

Abstract

Mid-field natural ponds promote regional biodiversity, providing alternative habitats for many valuable animal species. The study’s objective was to determine the most important abiotic factors, including hydrochemical and morphometric parameters, affecting fish occurrence in natural, small water bodies on agricultural lands. The studies [...] Read more.

Mid-field natural ponds promote regional biodiversity, providing alternative habitats for many valuable animal species. The study’s objective was to determine the most important abiotic factors, including hydrochemical and morphometric parameters, affecting fish occurrence in natural, small water bodies on agricultural lands. The studies were conducted in nine randomly selected water bodies located in Poland (the North European Plain). Eleven species of fish were recorded in the waterbodies, with the most abundant being cyprinids (mainly crucian carp). Canonical correspondence analysis (CCA) showed that an increase in oxygenation, temperature, amount of macrophytes, and K concentration and a decrease in the concentration of phosphates, electrical conductivity (EC), Mg, and Cl is associated with the most beneficial living conditions for the most frequently occurring species in the studied water bodies—crucian carp and tench. Aside from the hydrochemical parameters of water in the natural ponds, the number of fish correlates with the basin area and the pond area, maximum depth, area of the buffer zone surrounding the water bodies, and the number of macrophytes. This last factor also has a significant influence on the species’ abundance in the water bodies. Fish occurrences in mid-field ponds and common knowledge on their important role in the environment require taking steps to provide fish protection. Full article

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

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14 pages, 2645 KiB

Open AccessEditor’s ChoiceArticle

Machine Learning-Based Water Level Prediction in Lake Erie

by Qi Wang and Song Wang

Water 2020, 12(10), 2654; https://doi.org/10.3390/w12102654 - 23 Sep 2020

Cited by 31 | Viewed by 4768

Abstract

Predicting water levels of Lake Erie is important in water resource management as well as navigation since water level significantly impacts cargo transport options as well as personal choices of recreational activities. In this paper, machine learning (ML) algorithms including Gaussian process (GP), [...] Read more.

Predicting water levels of Lake Erie is important in water resource management as well as navigation since water level significantly impacts cargo transport options as well as personal choices of recreational activities. In this paper, machine learning (ML) algorithms including Gaussian process (GP), multiple linear regression (MLR), multilayer perceptron (MLP), M5P model tree, random forest (RF), and k-nearest neighbor (KNN) are applied to predict the water level in Lake Erie. From 2002 to 2014, meteorological data and one-day-ahead observed water level are the independent variables, and the daily water level is the dependent variable. The predictive results show that MLR and M5P have the highest accuracy regarding root mean square error (

RMSE)

and mean absolute error (MAE). The performance of ML models has also been compared against the performance of the process-based advanced hydrologic prediction system (AHPS), and the results indicate that ML models are superior in predictive accuracy compared to AHPS. Together with their time-saving advantage, this study shows that ML models, especially MLR and M5P, can be used for forecasting Lake Erie water levels and informing future water resources management. Full article

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11 pages, 1924 KiB

Open AccessEditor’s ChoiceArticle

Performance of Three Sorghum Cultivars under Excessive Rainfall and Waterlogged Conditions in the Sudano-Sahelian Zone of West Africa: A Case Study at the Climate-Smart Village of Cinzana in Mali

by Manuel Müller, Siaka Dembélé, Robert B. Zougmoré, Thomas Gaiser and Samuel T. Partey

Water 2020, 12(10), 2655; https://doi.org/10.3390/w12102655 - 23 Sep 2020

Cited by 7 | Viewed by 3888

Abstract

Recent climate analyses show trends for increasing precipitation variability with increasing precipitation sums in Mali. The increasing occurrence of temporary intra-seasonal droughts and waterlogging longer than a week demands climate-smart solutions. Research has focused on water deficits since the 1980s. However, besides droughts, [...] Read more.

Recent climate analyses show trends for increasing precipitation variability with increasing precipitation sums in Mali. The increasing occurrence of temporary intra-seasonal droughts and waterlogging longer than a week demands climate-smart solutions. Research has focused on water deficits since the 1980s. However, besides droughts, waterlogging can restrict productivity of sensitive cash and staple crops as cotton and corn. The year 2019 offered the historically unique opportunity to monitor waterlogging effects with 1088 mm precipitation in the rural commune Cinzanawith an isohyet of 681 mm. Impacts of two extreme downpours on three sorghum cultivars were monitored in a farmers-field experiment with three replications. All sorghum cultivars performed well in 2019 with significantly higher grain and above ground biomass yields than in the reference year 2007, with well distributed rainfall in Cinzana. “Jakumbè” (CSM63E) produced significantly higher grain yields than the hybrid cultivar “PR3009B” bred for high harvest index. The local cultivar “Gnofing” selected by local farmers produced significantly higher above ground biomass. All cultivars tolerated without severe stress symptoms 20 days waterlogging and 72 h inundation. Further waterlogging resilience research of other crops and other sorghum cultivars is needed to strengthen food security in Mali with expected increasing precipitation variation in the future. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Plant Water Use, Carbon Balance, Nutrient Economy, and Their Interactions)

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30 pages, 14004 KiB

Open AccessEditor’s ChoiceArticle

New Geomorphological and Historical Elements on Morpho-Evolutive Trends and Relative Sea-Level Changes of Naples Coast in the Last 6000 Years

by Gaia Mattei, Pietro P. C. Aucelli, Claudia Caporizzo, Angela Rizzo and Gerardo Pappone

Water 2020, 12(9), 2651; https://doi.org/10.3390/w12092651 - 22 Sep 2020

Cited by 22 | Viewed by 4372

Abstract

This research aims to present new data regarding the relative sea-level variations and related morpho-evolutive trends of Naples coast since the mid-Holocene, by interpreting several geomorphological and historical elements. The geomorphological analysis, which was applied to the emerged and submerged sector between Chiaia [...] Read more.

This research aims to present new data regarding the relative sea-level variations and related morpho-evolutive trends of Naples coast since the mid-Holocene, by interpreting several geomorphological and historical elements. The geomorphological analysis, which was applied to the emerged and submerged sector between Chiaia plain and Pizzofalcone promontory, took into account a dataset that is mainly composed of: measurements from direct surveys; bibliographic data from geological studies; historical sources; ancient pictures and maps; high-resolution digital terrain model (DTM) from Lidar; and, geo-acoustic and optical data from marine surveys off Castel dell’ Ovo carried out by using an USV (Unmanned Surface Vehicle). The GIS analysis of those data combined with iconographic researches allowed for reconstructing the high-resolution geomorphological map and three new palaeoenvironmental scenarios of the study area during the Holocene, deriving from the evaluation of the relative sea-level changes and vertical ground movements of volcano-tectonic origin affecting the coastal sector in the same period. In particular, three different relative sea-level stands were identified, dated around 6.5, 4.5, and 2.0 ky BP, respectively at +7, −5, and −3 m MSL, due to the precise mapping of several paleo-shore platforms that were ordered based on the altimetry and dated thanks to archaeological and geological interpretations. Full article

(This article belongs to the Special Issue Coastal Dynamic and Evolution)

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17 pages, 1566 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Grain Size Distribution on the Hydraulic Gradient for Initiating Backward Erosion

by Willem-Jan Dirkx, Rens van Beek and Marc Bierkens

Water 2020, 12(9), 2644; https://doi.org/10.3390/w12092644 - 22 Sep 2020

Cited by 8 | Viewed by 3012

Abstract

Backward erosion by piping is one of the processes that threaten the stability of river embankments in the Netherlands. During high river stages, groundwater flow velocities underneath the embankment increase as a result of the steepened hydraulic gradient. If a single outflow point [...] Read more.

Backward erosion by piping is one of the processes that threaten the stability of river embankments in the Netherlands. During high river stages, groundwater flow velocities underneath the embankment increase as a result of the steepened hydraulic gradient. If a single outflow point exists or forms, the concentrated flow can entrain soil particles, leading to the formation of a subsurface pipe. The processes controlling this phenomenon are still relatively unknown due to their limited occurrence and because piping is a subsurface phenomenon. To study the initiation of piping, we performed laboratory experiments in which we induced water flow through a porous medium with a vertically orientated outflow point. In these experiments, we explicitly considered grain size variations, thus adding to the existing database of experiments. Our experiments showed that the vertical velocity needed for the initiation of particle transport can be described well by Stokes’ law using the median grain size. We combine this with a novel method to relate bulk hydraulic conductivity to the grain size distribution. This shows that knowledge of the grain size distribution and the location of the outflow point are sufficient to estimate the hydraulic gradient needed to initiate pipe formation in the experiment box. Full article

(This article belongs to the Special Issue Local Erosion of Hydraulic Structures and Flood Protection)

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15 pages, 8076 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modelling Pluvial Flooding in Urban Areas Coupling the Models Iber and SWMM

by Esteban Sañudo, Luis Cea and Jerónimo Puertas

Water 2020, 12(9), 2647; https://doi.org/10.3390/w12092647 - 22 Sep 2020

Cited by 49 | Viewed by 7880

Abstract

Dual urban drainage models allow users to simulate pluvial urban flooding by analysing the interaction between the sewer network (minor drainage system) and the overland flow (major drainage system). This work presents a free distribution dual drainage model linking the models Iber and [...] Read more.

Dual urban drainage models allow users to simulate pluvial urban flooding by analysing the interaction between the sewer network (minor drainage system) and the overland flow (major drainage system). This work presents a free distribution dual drainage model linking the models Iber and Storm Water Management Model (SWMM), which are a 2D overland flow model and a 1D sewer network model, respectively. The linking methodology consists in a step by step calling process from Iber to a Dynamic-link Library (DLL) that contains the functions in which the SWMM code is split. The work involves the validation of the model in a simplified urban street, in a full-scale urban drainage physical model and in a real urban settlement. The three study cases have been carefully chosen to show and validate the main capabilities of the model. Therefore, the model is developed as a tool that considers the main hydrological and hydraulic processes during a rainfall event in an urban basin, allowing the user to plan, evaluate and design new or existing urban drainage systems in a realistic way. Full article

(This article belongs to the Special Issue Modelling of Floods in Urban Areas)

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18 pages, 8046 KiB

Open AccessEditor’s ChoiceArticle

Where Does the Chilean Aconcagua River Come from? Use of Natural Tracers for Water Genesis Characterization in Glacial and Periglacial Environments

by Sebastián Andrés Crespo, Céline Lavergne, Francisco Fernandoy, Ariel A. Muñoz, Leandro Cara and Simón Olfos-Vargas

Water 2020, 12(9), 2630; https://doi.org/10.3390/w12092630 - 21 Sep 2020

Cited by 12 | Viewed by 5601

Abstract

The Aconcagua river basin (Chile, 32 °S) has suffered the effects of the megadrought over the last decade. The severe snowfall deficiency drastically modified the water supply to the catchment headwaters. Despite the recognized snowmelt contribution to the basin, an unknown streamflow buffering [...] Read more.

The Aconcagua river basin (Chile, 32 °S) has suffered the effects of the megadrought over the last decade. The severe snowfall deficiency drastically modified the water supply to the catchment headwaters. Despite the recognized snowmelt contribution to the basin, an unknown streamflow buffering effect is produced by glacial, periglacial and groundwater inputs, especially in dry periods. Hence, each type of water source was characterized and quantified for each season, through the combination of stable isotope and ionic analyses as natural water tracers. The δ¹⁸O and electric conductivity were identified as the key parameters for the differentiation of each water source. The use of these parameters in the stable isotope mixing “simmr” model revealed that snowmelt input accounted 52% in spring and only 22–36% during the rest of the year in the headwaters. While glacial supply contributed up to 34%, both groundwater and periglacial exhibited a remarkable contribution around 20% with some seasonal variations. Downstream, glacial contribution averaged 15–20%, groundwater seasonally increased up to 46%, and periglacial input was surprisingly high (i.e., 14–21%). The different water sources contribution quantification over time for the Aconcagua River reported in this work provides key information for water security in this territory. Full article

(This article belongs to the Special Issue Application of Isotopic Data to Water Resource Management)

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29 pages, 435 KiB

Open AccessEditor’s ChoiceReview

Microplastics and Nanoplastics in the Freshwater and Terrestrial Environment: A Review

by Kellie Boyle and Banu Örmeci

Water 2020, 12(9), 2633; https://doi.org/10.3390/w12092633 - 21 Sep 2020

Cited by 167 | Viewed by 17744

Abstract

This review is a critical analysis of current freshwater and terrestrial research with an emphasis on transport, behaviour, fate and subsequent ecological impacts that plastic pollution poses. The current methods of extraction and evaluation of organic-rich samples are also explored for both micro- [...] Read more.

This review is a critical analysis of current freshwater and terrestrial research with an emphasis on transport, behaviour, fate and subsequent ecological impacts that plastic pollution poses. The current methods of extraction and evaluation of organic-rich samples are also explored for both micro- and nanoplastics. Furthermore, micro- and nanoplastics are discussed with reference to their environmental and health implications for biota. Regulations imposed on the manufacture and distribution of plastics globally are also noted. Within the review, the current literature has been presented and knowledge gaps identified. These include the characterization and quantification of micro- and nanoplastics entering and forming within the freshwater and terrestrial environment, the fate and behaviour of micro- and nanoplastics under varying conditions and the impacts of micro- and nanoplastics on freshwater and terrestrial ecosystems. Full article

18 pages, 5823 KiB

Open AccessEditor’s ChoiceArticle

COVID-19 Pandemic Consequences on Coastal Water Quality Using WST Sentinel-3 Data: Case of Tangier, Morocco

by El Khalil Cherif, Martin Vodopivec, Nezha Mejjad, Joaquim C.G. Esteves da Silva, Simona Simonovič and Hakim Boulaassal

Water 2020, 12(9), 2638; https://doi.org/10.3390/w12092638 - 21 Sep 2020

Cited by 48 | Viewed by 7585

Abstract

The west coast of Tangier, in northern Morocco, has been affected by industrial wastewater discharge that reaches the ocean through the Boukhalef river. Therefore, the Jbila and Sidikacem beaches near to the Boukhalef river mouth have been classified as polluted for many years. [...] Read more.

The west coast of Tangier, in northern Morocco, has been affected by industrial wastewater discharge that reaches the ocean through the Boukhalef river. Therefore, the Jbila and Sidikacem beaches near to the Boukhalef river mouth have been classified as polluted for many years. With the aim of determining the COVID-19 pandemic consequences on the Tangier coastal environment, a linear model using Sentinel 3 water surface temperature (WST) has been tested in several locations. Data from April 2019 and April 2020, before and during the COVID-19 pandemic related emergency status in Morocco, were compared. The results from April 2019 showed high WST values and consequently, the poorest water quality in the sites closest to the Boukhalef river mouth. On the other hand, the results from April 2020 showed normal WST values and high water quality in the same study area. These results illustrate the usefulness of Sentinel 3 WST for the estimation of bathing water quality on the west coast of Tangier. The study shows the positive impact of the COVID-19 pandemic consequences on the coastal environment quality in the study area and indicates the importance of decreasing the industrial discharge on the west coast of Tangier. The same methodology could be used in decision-making processes and to reduce cost, time and human resources for coastal monitoring systems. We demonstrate the potential of using the Sentinel 3 data for coastal waters monitoring, as well as the need for stricter controls of pollutant discharges into the world’s rivers. Full article

(This article belongs to the Special Issue SARS-CoV-2 in Waters: Rational)

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19 pages, 9176 KiB

Open AccessEditor’s ChoiceArticle

A Comprehensive Evaluation Model of Regional Water Resource Carrying Capacity: Model Development and a Case Study in Baoding, China

by Siyu Mou, Jingjing Yan, Jinghua Sha, Shen Deng, Zhenxing Gao, Wenlan Ke and Shule Li

Water 2020, 12(9), 2637; https://doi.org/10.3390/w12092637 - 21 Sep 2020

Cited by 13 | Viewed by 3183

Abstract

Scientific water resource carrying capacity (WRCC) evaluations are necessary for providing guidance for the sustainable utilization of water resources. Based on the driving-pressure-state-impact-response feedback loop, this paper selects 21 indicators under five dimensions to construct a regional WRCC comprehensive evaluation framework. The projection [...] Read more.

Scientific water resource carrying capacity (WRCC) evaluations are necessary for providing guidance for the sustainable utilization of water resources. Based on the driving-pressure-state-impact-response feedback loop, this paper selects 21 indicators under five dimensions to construct a regional WRCC comprehensive evaluation framework. The projection pursuit clustering (PPC) method is implemented with the matter-element extension (MEE) model to overcome the limitations of subjective deviation and indicator attribute incompatibility in traditional comprehensive assessment methods affecting the accuracy of evaluations. The application of the integrated evaluation model is demonstrated in Baoding city in the Jing-Jin-Ji area from 2010 to 2017. The results indicate that the economic water consumption intensity is the most influential factor that impacts the WRCC change in Baoding, and the pressure subsystem and response subsystem are dominant in the entire system. The WRCC in Baoding significantly improved between 2010 and 2017 from a grade V extremely unsafe state to a grade III critical state. Natural water shortages and large population scales are the main negative factors during this period; however, the existing measures are still insufficient to achieve an optimal WRCC status. Considering the future population and industry inflow, additional actions must be proposed to maintain and promote harmonious conditions. Full article

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

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20 pages, 3698 KiB

Open AccessEditor’s ChoiceArticle

Comparison Study of Multiple Precipitation Forcing Data on Hydrological Modeling and Projection in the Qujiang River Basin

by Yongyu Song, Jing Zhang, Xianyong Meng, Yuyan Zhou, Yuequn Lai and Yang Cao

Water 2020, 12(9), 2626; https://doi.org/10.3390/w12092626 - 19 Sep 2020

Cited by 18 | Viewed by 3398

Abstract

As a key factor in the water cycle and climate change, the quality of precipitation data directly affects the hydrological processes of the river basin. Although many precipitation products with high spatial and temporal resolutions are now widely used, it is meaningful and [...] Read more.

As a key factor in the water cycle and climate change, the quality of precipitation data directly affects the hydrological processes of the river basin. Although many precipitation products with high spatial and temporal resolutions are now widely used, it is meaningful and necessary to investigate and evaluate their merits and demerits in hydrological applications. In this study, two satellite-based precipitation products (Tropical Rainfall Measurement Mission, TRMM; Integrated Multi-satellite Retrievals for GPM, IMERG) and one reanalysis precipitation product (China Meteorological Assimilation Driving Datasets for the Soil and Water Assessment Tool (SWAT) model, CMADS) are studied to compare their streamflow simulation performance in the Qujiang River Basin, China, using the SWAT model with gauged rainfall data as a reference. The main conclusions are as follows: (1) CMADS has stronger precipitation detection capabilities compared to gauged rainfall, while TRMM results in the most obvious overestimation in the four sub-basins. (2) In daily and monthly streamflow simulations, CMADS + SWAT mode offers the best performance. CMADS and IMERG can provide high quality precipitation data for data-scarce areas, and IMERG can effectively avoid the overestimation of streamflow caused by TRMM, especially on a daily scale. (3) The runoff projections of the three modes under RCP (Representative Concentration Pathway) 4.5 was higher than that of RCP 8.5 on the whole. IMERG + SWAT overestimates the surface water resources of the basin compared to CMADS + SWAT, while TRMM + SWAT provides the most stable uncertainty. These findings contribute to the comparison of the differences among the three precipitation products and provides a reference for the selection of precipitation data in similar regions. Full article

(This article belongs to the Special Issue Precipitation Measurement Instruments: Calibration, Accuracy and Performance)

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16 pages, 3819 KiB

Open AccessEditor’s ChoiceArticle

Patterns of Mekong Mollusc Biodiversity: Identification of Emerging Threats and Importance to Management and Livelihoods in a Region of Globally Significant Biodiversity and Endemism

by Ratha Sor, Peng Bun Ngor, Pieter Boets, Peter L. M. Goethals, Sovan Lek, Zeb S. Hogan and Young-Seuk Park

Water 2020, 12(9), 2619; https://doi.org/10.3390/w12092619 - 18 Sep 2020

Cited by 15 | Viewed by 4730

Abstract

The Lower Mekong Basin (LMB) is a key biodiversity hotspot. To facilitate conservation and management, we examine mollusc biodiversity patterns and distribution along LMB’s longitudinal gradients, identify environmental drivers, and discuss the importance of these drivers to management. Cluster analysis, redundancy analysis (RDA), [...] Read more.

The Lower Mekong Basin (LMB) is a key biodiversity hotspot. To facilitate conservation and management, we examine mollusc biodiversity patterns and distribution along LMB’s longitudinal gradients, identify environmental drivers, and discuss the importance of these drivers to management. Cluster analysis, redundancy analysis (RDA), and variation partitioning were conducted using mollusc data collected from 63 sampling sites. Results indicated that species diversity is dominated by gastropods (61%) and bivalves (39%) and feeding trait diversity by scrapers (52%) and filter-collectors (37%). Only 48 species (49%) out of 98 taxa have been assessed by the International Union for Conservation of Nature (IUCN) including a growing number of invasive species. The lack of complete, up-to-date information highlights the need for more research on both native and alien species. Cluster analysis revealed a clear mollusc biodiversity structure along the LMB’s longitudinal segments. Diversity was lowest in upstream tributaries, increased in upstream main channels, and was highest in downstream channels and the Mekong delta, the exception being the observed high gastropod abundance in Chi-Mun river mouth and Luang Prabang areas. The RDA and variation partitioning demonstrated that combined physical–chemical and climatic conditions are the key drivers of biodiversity patterns. Given the potential spread of invasive alien species and increasing anthropogenic impacts, further ecological research, regular monitoring, and adaptive management are needed to sustain mollusc biodiversity and associated ecosystem services, which contribute to food security, nutrition, and livelihoods in the LMB. Full article

(This article belongs to the Special Issue Channels for Change: Integrating Multiple Disciplines for New Frontiers in Managing the Mekong River Basin)

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21 pages, 3024 KiB

Open AccessEditor’s ChoiceArticle

Autumn Phenological Response of European Beech to Summer Drought and Heat

by Veronika Lukasová, Jaroslav Vido, Jana Škvareninová, Svetlana Bičárová, Helena Hlavatá, Peter Borsányi and Jaroslav Škvarenina

Water 2020, 12(9), 2610; https://doi.org/10.3390/w12092610 - 18 Sep 2020

Cited by 23 | Viewed by 2808

Abstract

The changes in precipitation and temperature regimes brought on by the current climate change have influenced ecosystems globally. The consequences of climate change on plant phenology have been widely investigated during the last few years. However, the underlying causes of the timing of [...] Read more.

The changes in precipitation and temperature regimes brought on by the current climate change have influenced ecosystems globally. The consequences of climate change on plant phenology have been widely investigated during the last few years. However, the underlying causes of the timing of autumn phenology have not been fully clarified yet. Here, we focused on the onset (10%) of leaf colouring—LCO—(Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) 92) of European beech (Fagus sylvatica, L.) as an important native tree species growing throughout Europe. Studied beech stands are located along the natural distribution range of the European beech in Western Carpathians (Slovakia) at different altitudes from lowlands (300 m a.s.l.) to uplands (1050 m a.s.l.) and climatic regions from warm to cold. To define limiting climate conditions for LCO, we established several bioclimatic indices as indicators of meteorological drought: climatic water balance (CWB), standardized precipitation index (SPI), standardized precipitation-evapotranspiration index (SPEI), dry period index (DPI), and heat waves (HW). In addition, meteorological variables such as monthly mean temperatures and precipitation totals were taken into account. Throughout the 23-year period (1996–2018) of ground-based phenological observations of temperate beech forests, the timing of LCO was significantly delayed (p ≤ 0.05) in the middle to high altitudes, while in the lowest altitude, it remained unchanged. Over the last decade, 2009–2018, LCO in middle altitudes started at comparable to low altitudes and, at several years, even later. This resulted mainly from the significant negative effect of drought prior to this phenological phase (p ≤ 0.01) expressed through a 1-month SPI in September (SPI_IX) at the stand at the low-altitude and warm-climatic region. Our results indicate that the meteorological drought conditioned by lower total precipitation and higher evapotranspirative demands in the warmer climate advance leaf senescence. However, at present time, growth in rising temperature and precipitation is acceptable for most beech stands at middle to high altitudes. Beech utilizes these conditions and postpones the LCO by 0.3–0.5 and 0.6–1.2 day per year at high and middle altitudes, respectively. Although we show the commencing negative effect of drought at mid-altitudes with lower (below 700 mm) total annual precipitation, the trend of LCO in favourable warm climates is still significantly delayed. The ongoing warming trend of summer months suggests further intensification of drought as has started to occur in middle altitudes, spreading from the continual increase of evapotranspiration over the next decades. Full article

(This article belongs to the Special Issue Impact of Natural Hazards on Forest Ecosystems and Their Surrounding Landscape under Climate Change)

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24 pages, 1020 KiB

Open AccessEditor’s ChoiceArticle

A Nation-Wide Framework for Evaluating Freshwater Health in China: Background, Administration, and Indicators

by Chen Xie, Yifan Yang, Yang Liu, Guoqing Liu, Ziwu Fan and Yun Li

Water 2020, 12(9), 2596; https://doi.org/10.3390/w12092596 - 17 Sep 2020

Cited by 11 | Viewed by 2915

Abstract

This study reviewed the existing experience of implementing the nation-wide freshwater health evaluation in China and around the world and proposes a new framework that works in collaboration with the River Chief System (RCS). The institutional context of China with intertwined political and [...] Read more.

This study reviewed the existing experience of implementing the nation-wide freshwater health evaluation in China and around the world and proposes a new framework that works in collaboration with the River Chief System (RCS). The institutional context of China with intertwined political and scientific considerations makes it essential to establish a concise and quantitative approach to assess the effectiveness of the RCS as well as local freshwater health conditions that can be easily understood by non-experts for decision-making. To fulfil this objective, we reconstructed the indicator categories based on the best practices in major western countries and the existing regional standards in China. The new indicator framework includes two main aspects: Ecosystem integrity (physical habitat, water quantity, water quality, and aquatic life) and non-ecological performance (social services and water governance). Specifically, the non-ecological attributes of freshwaters are in accordance with the purposes of the RCS and are usually ignored in many countries. The final health grade for a specific water body is determined by a weighted averaging method; this grade is the core element of an evaluation protocol designed to produce reliable data for adaptable water resources governance in China. The research findings in this study will also be integrated into the new national standard to be issued by the Ministry of Water Resources of China in late 2020. Full article

(This article belongs to the Special Issue Water Resources Management Models for Policy Assessment)

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20 pages, 3941 KiB

Open AccessEditor’s ChoiceArticle

Water Body Extraction from Sentinel-3 Image with Multiscale Spatiotemporal Super-Resolution Mapping

by Xiaohong Yang, Yue Li, Yu Wei, Zhanlong Chen and Peng Xie

Water 2020, 12(9), 2605; https://doi.org/10.3390/w12092605 - 17 Sep 2020

Cited by 13 | Viewed by 3315

Abstract

Water body mapping is significant for water resource management. In the view of 21 spectral bands and a short revisit time of no more than two days, a Sentinel-3 OLCI (Ocean and Land Colour Instrument) image could be the optimum data source in [...] Read more.

Water body mapping is significant for water resource management. In the view of 21 spectral bands and a short revisit time of no more than two days, a Sentinel-3 OLCI (Ocean and Land Colour Instrument) image could be the optimum data source in the near-real-time mapping of water bodies. However, the image is often limited by its low spatial resolution in practice. Super-resolution mapping (SRM) is a good solution to generate finer spatial resolution maps than the input data allows. In this paper, a multiscale spatiotemporal super-resolution mapping (MSST_SRM) method for water bodies is proposed, particularly for Sentinel-3 OLCI images. The proposed MSST_SRM method employs the integrated Normalized Difference Water Index (NDWI) images calculated from four near-infrared (NIR) bands and Green Band 6 of the Sentinel-3 OLCI image as input data and combined the spectral, multispatial, and temporal terms into one objective function to generate a fine water body map. Two experiments in the Tibet Plate and Daye lakes were employed to test the effectiveness of the MSST_SRM method. Results revealed that by using multiscale spatial dependence under the framework of spatiotemporal super-resolution Mapping, MSST_SRM could generate finer water body maps than the hard classification method and the other three SRM-based methods. Therefore, the proposed MSST_SRM method shows marked efficiency and potential in water body mapping using Sentinel-3 OLCI images. Full article

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

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22 pages, 2542 KiB

Open AccessEditor’s ChoiceArticle

Overview of 12 Years of Special Rapporteurs on the Human Rights to Water and Sanitation: Looking Forward to Future Challenges

by Léo Heller, Catarina De Albuquerque, Virginia Roaf and Alejandro Jiménez

Water 2020, 12(9), 2598; https://doi.org/10.3390/w12092598 - 17 Sep 2020

Cited by 13 | Viewed by 3488

Abstract

The year 2020 marks the 10th anniversary of the United Nations (UN) resolution that recognized the human rights to water and sanitation (HRtWS), and is the last year of the second mandate of the Special Rapporteurs (SRs), spanning 12 years in total. This [...] Read more.

The year 2020 marks the 10th anniversary of the United Nations (UN) resolution that recognized the human rights to water and sanitation (HRtWS), and is the last year of the second mandate of the Special Rapporteurs (SRs), spanning 12 years in total. This paper discusses the challenges in the fulfilment of the rights through the work of the SRs, based on an analysis of the twenty-three country visits, seven follow-up reports, and twenty-two thematic reports elaborated during this time. While policy, regulation and finance receive the most attention from the SRs, the analysis of the follow-up reports show that the SRs’ recommendations alone might not be enough to trigger structural changes at country level. Aspects of accountability, equality and nondiscrimination also stand out in the work of the SRs. Based on the analysis, the last section identifies topics, settings, and groups that require further attention from a human rights perspective including: extraterritorial obligations, including transboundary waters; the UN and the HRtWS; climate change; public provision of water and sanitation services; drinking water quality control and surveillance; rural sanitation; indigenous peoples; sanitation workers; informal settlements; and capacity development. Full article

(This article belongs to the Special Issue Human Rights to Water and Sanitation)

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20 pages, 2705 KiB

Open AccessEditor’s ChoiceArticle

Kernel Extreme Learning Machine: An Efficient Model for Estimating Daily Dew Point Temperature Using Weather Data

by Meysam Alizamir, Sungwon Kim, Mohammad Zounemat-Kermani, Salim Heddam, Nam Won Kim and Vijay P. Singh

Water 2020, 12(9), 2600; https://doi.org/10.3390/w12092600 - 17 Sep 2020

Cited by 17 | Viewed by 2645

Abstract

Accurate estimation of dew point temperature (T_dew) has a crucial role in sustainable water resource management. This study investigates kernel extreme learning machine (KELM), boosted regression tree (BRT), radial basis function neural network (RBFNN), multilayer perceptron neural network (MLPNN), and multivariate [...] Read more.

Accurate estimation of dew point temperature (T_dew) has a crucial role in sustainable water resource management. This study investigates kernel extreme learning machine (KELM), boosted regression tree (BRT), radial basis function neural network (RBFNN), multilayer perceptron neural network (MLPNN), and multivariate adaptive regression spline (MARS) models for daily dew point temperature estimation at Durham and UC Riverside stations in the United States. Daily time scale measured hydrometeorological data, including wind speed (WS), maximum air temperature (TMAX), minimum air temperature (TMIN), maximum relative humidity (RHMAX), minimum relative humidity (RHMIN), vapor pressure (VP), soil temperature (ST), solar radiation (SR), and dew point temperature (T_dew) were utilized to investigate the applied predictive models. Results of the KELM model were compared with other models using eight different input combinations with respect to root mean square error (RMSE), coefficient of determination (R²), and Nash–Sutcliffe efficiency (NSE) statistical indices. Results showed that the KELM models, using three input parameters, VP, TMAX, and RHMIN, with RMSE = 0.419 °C, NSE = 0.995, and R² = 0.995 at Durham station, and seven input parameters, VP, ST, RHMAX, TMIN, RHMIN, TMAX, and WS, with RMSE = 0.485 °C, NSE = 0.994, and R² = 0.994 at UC Riverside station, exhibited better performance in the modeling of daily T_dew. Finally, it was concluded from a comparison of the results that out of the five models applied, the KELM model was found to be the most robust by improving the performance of BRT, RBFNN, MLPNN, and MARS models in the testing phase at both stations. Full article

(This article belongs to the Section Hydrology)

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13 pages, 4067 KiB

Open AccessEditor’s ChoiceArticle

Did the COVID-19 Lockdown-Induced Hydrological Residence Time Intensify the Primary Productivity in Lakes? Observational Results Based on Satellite Remote Sensing

by Ram Avtar, Pankaj Kumar, Hitesh Supe, Dou Jie, Netranada Sahu, Binaya Kumar Mishra and Ali P. Yunus

Water 2020, 12(9), 2573; https://doi.org/10.3390/w12092573 - 15 Sep 2020

Cited by 19 | Viewed by 4623

Abstract

The novel coronavirus pandemic (COVID-19) has brought countries around the world to a standstill in the early part of 2020. Several nations and territories around the world insisted their population stay indoors for practicing social distance in order to avoid infecting the disease. [...] Read more.

The novel coronavirus pandemic (COVID-19) has brought countries around the world to a standstill in the early part of 2020. Several nations and territories around the world insisted their population stay indoors for practicing social distance in order to avoid infecting the disease. Consequently, industrial activities, businesses, and all modes of traveling have halted. On the other hand, the pollution level decreased ‘temporarily’ in our living environment. As fewer pollutants are supplied in to the hydrosphere, and human recreational activities are stopped completely during the lockdown period, we hypothesize that the hydrological residence time (HRT) has increased in the semi-enclosed or closed lake bodies, which can in turn increase the primary productivity. To validate our hypothesis, and to understand the effect of lockdown on primary productivity in aquatic systems, we quantitatively estimated the chlorophyll-a (Chl-a) concentrations in different lake bodies using established Chl-a retrieval algorithm. The Chl-a monitored using Landsat-8 and Sentinel-2 sensor in the lake bodies of Wuhan, China, showed an elevated concentration of Chl-a. In contrast, no significant changes in Chl-a are observed for Vembanad Lake in India. Further analysis of different geo-environments is necessary to validate the hypothesis. Full article

(This article belongs to the Special Issue Water Quality Assessments for Urban Water Environment)

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