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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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17 pages, 9236 KiB  
Article
Stratigraphic Analysis of Firn Cores from an Antarctic Ice Shelf Firn Aquifer
by Shelley MacDonell, Francisco Fernandoy, Paula Villar and Arno Hammann
Water 2021, 13(5), 731; https://doi.org/10.3390/w13050731 - 8 Mar 2021
Cited by 7 | Viewed by 4370
Abstract
In recent decades, several large ice shelves in the Antarctic Peninsula region have experienced significant ice loss, likely driven by a combination of oceanic, atmospheric and hydrological processes. All three areas need further research, however, in the case of the role of liquid [...] Read more.
In recent decades, several large ice shelves in the Antarctic Peninsula region have experienced significant ice loss, likely driven by a combination of oceanic, atmospheric and hydrological processes. All three areas need further research, however, in the case of the role of liquid water the first concern is to address the paucity of field measurements. Despite this shortage of field observations, several authors have proposed the existence of firn aquifers on Antarctic ice shelves, however little is known about their distribution, formation, extension and role in ice shelf mechanics. In this study we present the discovery of saturated firn at three drill sites on the Müller Ice Shelf (67°14′ S; 66°52′ W), which leads us to conclude that either a large contiguous or several disconnected smaller firn aquifers exist on this ice shelf. From the stratigraphic analysis of three short firn cores extracted during February 2019 we describe a new classification system to identify the structures and morphological signatures of refrozen meltwater, identify evidence of superficial meltwater percolation, and use this information to propose a conceptual model of firn aquifer development on the Müller Ice Shelf. The detailed stratigraphic analysis of the sampled cores will provide an invaluable baseline for modelling studies. Full article
(This article belongs to the Special Issue Review and Progress in Hydrological and Meteorological Monitoring of Glaciers)
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22 pages, 3363 KiB  
Article
An Enhanced Innovative Triangular Trend Analysis of Rainfall Based on a Spectral Approach
by Bilel Zerouali, Nadhir Al-Ansari, Mohamed Chettih, Mesbah Mohamed, Zaki Abda, Celso Augusto Guimarães Santos, Bilal Zerouali and Ahmed Elbeltagi
Water 2021, 13(5), 727; https://doi.org/10.3390/w13050727 - 7 Mar 2021
Cited by 17 | Viewed by 4418
Abstract
The world is currently witnessing high rainfall variability at the spatiotemporal level. In this paper, data from three representative rain gauges in northern Algeria, from 1920 to 2011, at an annual scale, were used to assess a relatively new hybrid method, which combines [...] Read more.
The world is currently witnessing high rainfall variability at the spatiotemporal level. In this paper, data from three representative rain gauges in northern Algeria, from 1920 to 2011, at an annual scale, were used to assess a relatively new hybrid method, which combines the innovative triangular trend analysis (ITTA) with the orthogonal discrete wavelet transform (DWT) for partial trend identification. The analysis revealed that the period from 1950 to 1975 transported the wettest periods, followed by a long-term dry period beginning in 1973. The analysis also revealed a rainfall increase during the latter decade. The combined method (ITTA–DWT) showed a good efficiency for extreme rainfall event detection. In addition, the analysis indicated the inter- to multiannual phenomena that explained the short to medium processes that dominated the high rainfall variability, masking the partial trend components existing in the rainfall time series and making the identification of such trends a challenging task. The results indicate that the approaches—combining ITTA and selected input combination models resulting from the DWT—are auspicious compared to those found using the original rainfall observations. This analysis revealed that the ITTA–DWT method outperformed the ITTA method for partial trend identification, which proved DWT’s efficiency as a coupling method. Full article
(This article belongs to the Special Issue Advanced Research on Sustainable Water Resources Management and Planning under Climate Change)
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13 pages, 2054 KiB  
Article
Comparison between the Lagrangian and Eulerian Approach in Simulation of Free Surface Air-Core Vortices
by Maryam Azarpira, Amir Reza Zarrati and Pouya Farrokhzad
Water 2021, 13(5), 726; https://doi.org/10.3390/w13050726 - 7 Mar 2021
Cited by 14 | Viewed by 9370
Abstract
The problematic consequences regarding formation of air-core vortices at the intakes and the drastic necessity of a thorough investigation into the phenomenon has resulted in particular attention being placed on Computational Fluid Dynamics (CFD) as an economically viable method. Two main approaches could [...] Read more.
The problematic consequences regarding formation of air-core vortices at the intakes and the drastic necessity of a thorough investigation into the phenomenon has resulted in particular attention being placed on Computational Fluid Dynamics (CFD) as an economically viable method. Two main approaches could be taken using CFD, namely the Eulerian and Lagrangian methods each of which is characterized by specific advantages and disadvantages. Whereas many researchers have used the Eulerian approach for vortex simulation, the Lagrangian approach has not been found in the literature. The present study dealt with the comparison of the Lagrangian and Eulerian approaches in the simulation of vortex flow. Simulations based on both approaches were carried out by solving the Navier–Stokes equations accompanied by the LES turbulence model. The results of the numerical model were evaluated in accordance with a physical model for steady vortex flow using particle image velocimetry (PIV), revealing that both approaches are sufficiently capable of simulating the vortex flow but with the difference that the Lagrangian method has greater computational cost with less accuracy. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Hydraulics)
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17 pages, 6352 KiB  
Article
Performance Assessment of Posidonia oceanica (L.) Delile Restoration Experiment on Dead matte Twelve Years after Planting—Structural and Functional Meadow Features
by Sebastiano Calvo, Roberta Calvo, Filippo Luzzu, Vincenzo Raimondi, Mauro Assenzo, Federica Paola Cassetti and Agostino Tomasello
Water 2021, 13(5), 724; https://doi.org/10.3390/w13050724 - 7 Mar 2021
Cited by 22 | Viewed by 5667
Abstract
Following the restoration of natural conditions by reducing human pressures, reforestation is currently considered a possible option to accelerate the recovery of seagrass habitats. Long-term monitoring programs theoretically represent an ideal solution to assess whether a reforestation plan has produced the desired results. [...] Read more.
Following the restoration of natural conditions by reducing human pressures, reforestation is currently considered a possible option to accelerate the recovery of seagrass habitats. Long-term monitoring programs theoretically represent an ideal solution to assess whether a reforestation plan has produced the desired results. Here, we report on the performance of a 20 m2 patch of Posidonia oceanica transplanted on dead matte twelve years after transplantation in the Gulf of Palermo, northwestern Sicily. Photo mosaic performed in the area allowed us to detect 23 transplanted patches of both regular and irregular shape, ranging from 0.1 to 2.7 m2 and an overall surface close to 19 m2. Meadow density was 331.6 ± 17.7 shoot m−2 (currently five times higher than the initial value of 66 shoots m−2), and it did not show statistical differences from a close by natural meadow (331.2 ± 14.9). Total primary production, estimated by lepidochronology, varied from 333.0 to 332.7 g dw m2/year, at the transplanted and natural stand, respectively. These results suggest that complete restoration of P. oceanica on dead matte is possible in a relatively short time (a decade), thus representing a good starting point for upscaling the recovery of the degraded meadows in the area. Full article
(This article belongs to the Special Issue Restore Degraded Marine Coastal Areas in the Mediterranean Sea)
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27 pages, 7155 KiB  
Article
Interdecadal Variability in Myanmar Rainfall in the Monsoon Season (May–October) Using Eigen Methods
by Zin Mie Mie Sein, Irfan Ullah, Farhan Saleem, Xiefei Zhi, Sidra Syed and Kamran Azam
Water 2021, 13(5), 729; https://doi.org/10.3390/w13050729 - 7 Mar 2021
Cited by 37 | Viewed by 6939
Abstract
In this study, we investigated the interdecadal variability in monsoon rainfall in the Myanmar region. The gauge-based gridded rainfall dataset of the Global Precipitation Climatology Centre (GPCC) and Climatic Research Unit version TS4.0 (CRU TS4.0) were used (1950–2019) to investigate the interdecadal variability [...] Read more.
In this study, we investigated the interdecadal variability in monsoon rainfall in the Myanmar region. The gauge-based gridded rainfall dataset of the Global Precipitation Climatology Centre (GPCC) and Climatic Research Unit version TS4.0 (CRU TS4.0) were used (1950–2019) to investigate the interdecadal variability in summer monsoon rainfall using empirical orthogonal function (EOF), singular value decomposition (SVD), and correlation approaches. The results reveal relatively negative rainfall anomalies during the 1980s, 1990s, and 2000s, whereas strong positive rainfall anomalies were identified for the 1970s and 2010s. The dominant spatial variability mode showed a dipole pattern with a total variance of 47%. The power spectra of the principal component (PC) from EOF revealed a significant peak during decadal timescales (20–30 years). The Myanmar summer monsoon rainfall positively correlated with Atlantic multidecadal oscillation (AMO) and negatively correlated with Pacific decadal oscillation (PDO). The results reveal that extreme monsoon rainfall (flood) events occurred during the negative phase of the PDO and below-average rainfall (drought) occurred during the positive phase of the PDO. The cold phase (warm phase) of AMO was generally associated with negative (positive) decadal monsoon rainfall. The first SVD mode indicated the Myanmar rainfall pattern associated with the cold and warm phase of the PDO and AMO, suggesting that enhanced rainfall for about 53% of the square covariance fraction was related to heavy rain over the study region except for the central and eastern parts. The second SVD mode demonstrated warm sea surface temperature (SST) in the eastern equatorial Pacific (El Niño pattern) and cold SST in the North Atlantic Ocean, implying a rainfall deficit of about 33% of the square covariance fraction, which could be associated with dry El Niño conditions (drought). The third SVD revealed that cold SSTs in the central and eastern equatorial Pacific (La Niña pattern) caused enhance rainfall with a 6.7% square covariance fraction related to flood conditions. Thus, the extra-subtropical phenomena may affect the average summer monsoon trends over Myanmar by enhancing the cross-equatorial moisture trajectories into the North Atlantic Ocean. Full article
(This article belongs to the Section Water Use and Scarcity)
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22 pages, 3422 KiB  
Article
Construction of Critical Periods for Water Resources Management and Their Application in the FEW Nexus
by Val Z. Schull, Sushant Mehan, Margaret W. Gitau, David R. Johnson, Shweta Singh, Juan P. Sesmero and Dennis C. Flanagan
Water 2021, 13(5), 718; https://doi.org/10.3390/w13050718 - 6 Mar 2021
Cited by 4 | Viewed by 4411
Abstract
Amidst the growing population, urbanization, globalization, and economic growth, along with the impacts of climate change, decision-makers, stakeholders, and researchers need tools for better assessment and communication of the highly interconnected food–energy–water (FEW) nexus. This study aimed to identify critical periods for water [...] Read more.
Amidst the growing population, urbanization, globalization, and economic growth, along with the impacts of climate change, decision-makers, stakeholders, and researchers need tools for better assessment and communication of the highly interconnected food–energy–water (FEW) nexus. This study aimed to identify critical periods for water resources management for robust decision-making for water resources management at the nexus. Using a 4610 ha agricultural watershed as a pilot site, historical data (2006–2012), scientific literature values, and SWAT model simulations were utilized to map out critical periods throughout the growing season of corn and soybeans. The results indicate that soil water deficits are primarily seen in June and July, with average deficits and surpluses ranging from −134.7 to +145.3 mm during the study period. Corresponding water quality impacts include average monthly surface nitrate-N, subsurface nitrate-N, and soluble phosphorus losses of up to 0.026, 0.26, and 0.0013 kg/ha, respectively, over the growing season. Estimated fuel requirements for the agricultural practices ranged from 24.7 to 170.3 L/ha, while estimated carbon emissions ranged from 0.3 to 2.7 kg CO2/L. A composite look at all the FEW nexus elements showed that critical periods for water management in the study watershed occurred in the early and late season—primarily related to water quality—and mid-season, related to water quantity. This suggests the need to adapt agricultural and other management practices across the growing season in line with the respective water management needs. The FEW nexus assessment methodologies developed in this study provide a framework in which spatial, temporal, and literature data can be implemented for improved water resources management in other areas. Full article
(This article belongs to the Special Issue The Water-Energy-Food Nexus: Sustainable Development)
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18 pages, 4720 KiB  
Article
Urban Groundwater Contamination by Non-Steroidal Anti-Inflammatory Drugs
by Anna Jurado, Enric Vázquez-Suñé and Estanislao Pujades
Water 2021, 13(5), 720; https://doi.org/10.3390/w13050720 - 6 Mar 2021
Cited by 33 | Viewed by 4647
Abstract
Pharmaceuticals, such as non-steroidal anti-inflammatory drugs (NSAIDs) and their metabolites, have become a major concern due to their increasing consumption and their widespread occurrence in the environment. In this paper, we investigate the occurrence of NSAIDs and their metabolites in an urban aquifer, [...] Read more.
Pharmaceuticals, such as non-steroidal anti-inflammatory drugs (NSAIDs) and their metabolites, have become a major concern due to their increasing consumption and their widespread occurrence in the environment. In this paper, we investigate the occurrence of NSAIDs and their metabolites in an urban aquifer, which may serve as a potential resource for drinking water, and propose a methodology to assess the removal of these substances in the river–groundwater interface. Then, risk quotients (RQs) are computed, in order to determine the risk posed by the single NSAIDs and their mixture to human health. To this end, six NSAIDs and two metabolites were collected from an urban aquifer located in the metropolitan area of Barcelona (NE, Spain), in which the major pollution source is a contaminated river. All of the target NSAIDs were detected in groundwater samples, where the concentrations in the aquifer were higher than those found in the river water (except for ibuprofen). Diclofenac, ketoprofen, propyphenazone and salicylic acid were detected at high mean concentrations (ranging from 91.8 ng/L to 225.2 ng/L) in the aquifer. In contrast, phenazone and mefenamic acid were found at low mean concentrations (i.e., lower than 25 ng/L) in the aquifer. According to the proposed approach, the mixing of river water recharge into the aquifer seemed to some extent to promote the removal of the NSAIDs under the sub-oxic to denitrifying conditions found in the groundwater. The NSAIDs that presented higher mean removal values were 4OH diclofenac (0.8), ibuprofen (0.78), salicylic acid (0.35) and diclofenac (0.28), which are likely to be naturally attenuated under the aforementioned redox conditions. Concerning human health risk assessment, the NSAIDs detected in groundwater and their mixture do not pose any risk for all age intervals considered, as the associated RQs were all less than 0.05. Nevertheless, this value must be taken with caution, as many pharmaceuticals might occur simultaneously in the groundwater. Full article
(This article belongs to the Special Issue Urban Groundwater)
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15 pages, 4110 KiB  
Article
Influence of Groundwater Discharge on Temporal Evolution in Two Wetlands of an Intensely Anthropized Area: Analysis Using an Integrated Approach
by Francisco Sánchez-Martos, José Manuel López-Martos, Luis Molina Sánchez, Juan Gisbert-Gallego and Francisco Navarro-Martínez
Water 2021, 13(5), 697; https://doi.org/10.3390/w13050697 - 5 Mar 2021
Cited by 2 | Viewed by 2986
Abstract
The Campo de Dalías is a coastal plain, which has undergone a significant change in land use and intensive exploitation of groundwater. A series of diverse data has been analyzed: aerial and satellite images (1956–2013), evolution of the water table (1973–2019), and exploitation [...] Read more.
The Campo de Dalías is a coastal plain, which has undergone a significant change in land use and intensive exploitation of groundwater. A series of diverse data has been analyzed: aerial and satellite images (1956–2013), evolution of the water table (1973–2019), and exploitation of different aquifers (1964–2017). The results indicate: (1) increase in the surface area occupied by greenhouses, (2) increase in abstraction of groundwater, and (3) an opposite trend in the piezometric evolution of the two aquifers (deep and shallow). All this has had a significant effect on the evolution of the “Punta Entinas” wetland, which has shown a continuous increase in flooded surface area, especially pronounced since 1994. Its waters have intermediate hydrochemical characteristics between seawater and groundwater and reflect the local influence of groundwater on the wetland. The applied methodology is useful in areas with sustained human activity, land use changes, and intensive groundwater exploitation, and can contribute to the understanding of surface water-groundwater dependence and wetland management. Full article
(This article belongs to the Special Issue Advances in the Study and Understanding of Groundwater Discharge to Surface Water)
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25 pages, 25677 KiB  
Article
Evaluation of Water Social Service and Comprehensive Water Management Linked with Integrated River Evaluation
by Da Ye Kim, Su Hee Park and Chul Min Song
Water 2021, 13(5), 706; https://doi.org/10.3390/w13050706 - 5 Mar 2021
Cited by 9 | Viewed by 2647
Abstract
Various factors like climate change and population increase have limited water management evaluation. In South Korea particularly, although the management of water quality and water quantity has recently been integrated, a comprehensive policy has not yet been identified. This study, therefore, aims to [...] Read more.
Various factors like climate change and population increase have limited water management evaluation. In South Korea particularly, although the management of water quality and water quantity has recently been integrated, a comprehensive policy has not yet been identified. This study, therefore, aims to propose a methodology for evaluating water social service for 18 basins near major water resources in South Korea. It aims to promote advanced water resource management, secure water equity, and improve inadequate policy implementation. In addition, it proposes a methodology for comprehensive water management evaluation linked with integrated river evaluation with respect to water quality and water quantity. Accordingly, contrary to the common assumption that the entire population has easy access to the supplied water, the status of water service was assessed objectively. The status of water management per sector was also visually represented, through which the vulnerabilities of water management could be intuitively diagnosed. Based on the possibility of utilizing the study results to determine the basic direction for water management, the methodology of this study has been proposed as a tool for establishing an efficient water management policy. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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25 pages, 17640 KiB  
Article
Numerical Study on the Hydraulic Properties of Flow over Different Pooled Stepped Spillways
by Amir Ghaderi, Saeed Abbasi and Silvia Di Francesco
Water 2021, 13(5), 710; https://doi.org/10.3390/w13050710 - 5 Mar 2021
Cited by 29 | Viewed by 4135
Abstract
This work presents numerical simulations carried out to study the influence of geometric characteristics of pooled steps on the energy dissipation performance, flow patterns properties, velocity rates, and pressure distributions over a spillway. The localization of the inception point of air entrainment was [...] Read more.
This work presents numerical simulations carried out to study the influence of geometric characteristics of pooled steps on the energy dissipation performance, flow patterns properties, velocity rates, and pressure distributions over a spillway. The localization of the inception point of air entrainment was also assessed, being a key design parameter of spillways. With this aim, different configurations of steps were taken in account, including flat, pooled, and notch pooled types. The computational procedure was first validated with experimental results from the literature and then used to test the hydraulic behavior derived from different geometric configurations. The flat step configuration showed the best energy dissipation performance as compared with other configurations. With the notched pooled step configuration, the efficiency performance of the pooled structure improved by about 5.8%. The interfacial velocities of the flat stepped spillway were smaller than those of the pooled structure. The pressure value at the beginning of the step in the pooled configuration was larger than the flat configuration, while for the notched pool the maximum pressure values decreased near the step pool. Pool configuration (simple or notched) did not have a significant influence on the location of air entrainment. Full article
(This article belongs to the Special Issue Ecohydraulics Modeling and Simulation)
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16 pages, 7584 KiB  
Article
Integrating GIS-Based MCDA Techniques and the SCS-CN Method for Identifying Potential Zones for Rainwater Harvesting in a Semi-Arid Area
by Hussein Al-Ghobari and Ahmed Z. Dewidar
Water 2021, 13(5), 704; https://doi.org/10.3390/w13050704 - 5 Mar 2021
Cited by 46 | Viewed by 6069
Abstract
An increasing scarcity of water, as well as rapid global climate change, requires more effective water conservation alternatives. One promising alternative is rainwater harvesting (RWH). Nevertheless, the evaluation of RWH potential together with the selection of appropriate sites for RWH structures is significantly [...] Read more.
An increasing scarcity of water, as well as rapid global climate change, requires more effective water conservation alternatives. One promising alternative is rainwater harvesting (RWH). Nevertheless, the evaluation of RWH potential together with the selection of appropriate sites for RWH structures is significantly difficult for the water managers. This study deals with this difficulty by identifying RWH potential areas and sites for RWH structures utilizing geospatial and multi-criteria decision analysis (MCDA) techniques. The conventional data and remote sensing data were employed to set up needed thematic layers using ArcGIS software. The soil conservation service curve number (SCS-CN) method was used to determine surface runoff, centered on which yearly runoff potential map was produced in the ArcGIS environment. Thematic layers such as drainage density, slope, land use/cover, and runoff were allotted appropriate weights to produced RWH potential areas and zones appropriate for RWH structures maps of the study location. Results analysis revealed that the outcomes of the spatial allocation of yearly surface runoff depth ranging from 83 to 295 mm. Moreover, RWH potential areas results showed that the study areas can be categorized into three RWH potential areas: (a) low suitability, (b) medium suitability, and (c) high suitability. Nearly 40% of the watershed zone falls within medium and high suitability RWH potential areas. It is deduced that the integrated MCDA and geospatial techniques provide a valuable and formidable resource for the strategizing of RWH within the study zones. Full article
(This article belongs to the Section Hydrology)
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27 pages, 26491 KiB  
Article
Incorporating the Effects of Complex Soil Layering and Thickness Local Variability into Distributed Landslide Susceptibility Assessments
by Francesco Fusco, Benjamin B. Mirus, Rex L. Baum, Domenico Calcaterra and Pantaleone De Vita
Water 2021, 13(5), 713; https://doi.org/10.3390/w13050713 - 5 Mar 2021
Cited by 31 | Viewed by 3949
Abstract
Incorporating the influence of soil layering and local variability into the parameterizations of physics-based numerical models for distributed landslide susceptibility assessments remains a challenge. Typical applications employ substantial simplifications including homogeneous soil units and soil-hydraulic properties assigned based only on average textural classifications; [...] Read more.
Incorporating the influence of soil layering and local variability into the parameterizations of physics-based numerical models for distributed landslide susceptibility assessments remains a challenge. Typical applications employ substantial simplifications including homogeneous soil units and soil-hydraulic properties assigned based only on average textural classifications; the potential impact of these assumptions is usually disregarded. We present a multi-scale approach for parameterizing the distributed Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model that accounts for site-specific spatial variations in both soil thickness and complex layering properties by defining homogeneous soil properties that vary spatially for each model grid cell. These effective properties allow TRIGRS to accurately simulate the timing and distribution of slope failures without any modification of the model structure. We implemented this approach for the carbonate ridge of Sarno Mountains (southern Italy) whose slopes are mantled by complex layered soils of pyroclastic origin. The urbanized foot slopes enveloping these mountains are among the most landslide-prone areas of Italy and have been subjected to repeated occurrences of damaging and deadly rainfall-induced flow-type shallow landslides. At this scope, a primary local-scale application of TRIGRS was calibrated on physics-based rainfall thresholds, previously determined by a coupled VS2D (version 1.3) hydrological modeling and slope stability analysis. Subsequently, by taking into account the spatial distribution of soil thickness and vertical heterogeneity of soil hydrological and mechanical properties, a distributed assessment of landslide hazard was carried out by means of TRIGRS. The combination of these approaches led to the spatial assessment of landslide hazard under different hypothetical rainfall intensities and antecedent hydrological conditions. This approach to parameterizing TRIGRS can be adapted to other spatially variable soil layering and thickness to improve hazard assessments. Full article
(This article belongs to the Special Issue Rainfall-Induced Shallow Landslides Modeling and Warning)
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27 pages, 4363 KiB  
Article
Validation of Water Quality Monitoring Algorithms for Sentinel-2 and Sentinel-3 in Mediterranean Inland Waters with In Situ Reflectance Data
by Xavier Sòria-Perpinyà, Eduardo Vicente, Patricia Urrego, Marcela Pereira-Sandoval, Carolina Tenjo, Antonio Ruíz-Verdú, Jesús Delegido, Juan Miguel Soria, Ramón Peña and José Moreno
Water 2021, 13(5), 686; https://doi.org/10.3390/w13050686 - 3 Mar 2021
Cited by 41 | Viewed by 5700
Abstract
Freshwater quality maintenance is essential for human use and ecological functions. To ensure this objective, governments establish programs for a continuous monitoring of the inland waters state. This could be possible with Sentinel-2 (S2) and Sentinel-3 (S3), two remote sensing satellites of the [...] Read more.
Freshwater quality maintenance is essential for human use and ecological functions. To ensure this objective, governments establish programs for a continuous monitoring of the inland waters state. This could be possible with Sentinel-2 (S2) and Sentinel-3 (S3), two remote sensing satellites of the European Space Agency, equipped with spectral optical sensors. To determine optimal water quality algorithms applicable to their spectral bands, 36 algorithms were tested for different key variables (chlorophyll a (Chl_a), colored dissolved organic matter (CDOM), colored dissolved organic matter (TSS), phycocyanin (PC) and Secchi disk depth (SDD)). A database of 296 water-leaving reflectance spectra were used, as well as concomitant water quality measurements of Mediterranean reservoirs and lakes of Spain. Two equal data sets were used for calibration and validation. The best algorithms were recalculated using all database and used the following band relations: SDD, R560/R700; CDOM, R665/R490; PC, R705/R665 for S2 and R620, R665, R709 and R779 for S3, using a semi-analytical algorithm; R700 for TSS < 20 mg/L and R783/R492 (S2) or R779/R510 (S3) for TSS > 20 mg/L; and for Chl_a, the maximum (R443; R492)/R560 for Chl_a < 5 mg/m3 and R700/R665 for Chl_a > 5 mg/m3. A preliminary test with a satellite image in a well-known reservoir showed results consistent with the expected ranges and spatial patterns of the variables. Full article
(This article belongs to the Special Issue Methods for Assessing Water Quality and Its Impacts on Ecological Status in Reservoirs)
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15 pages, 6161 KiB  
Article
Minimum Residual Flows for Catchments in the Czech Republic
by Pavel Balvín, Adam Vizina, Magdalena Nesládková, Johanna Blöcher, Marcela Makovcová, Vojtěch Moravec and Martin Hanel
Water 2021, 13(5), 689; https://doi.org/10.3390/w13050689 - 3 Mar 2021
Cited by 7 | Viewed by 2961
Abstract
The determination of minimum residual flow (MRF) follows diverse methodology in Europe due to differing hydrological conditions, ecosystem requirements, water abstraction requirements, and legislation. Methodologies in individual countries are difficult to compare qualitatively. However, individual approaches can serve as examples for countries undergoing [...] Read more.
The determination of minimum residual flow (MRF) follows diverse methodology in Europe due to differing hydrological conditions, ecosystem requirements, water abstraction requirements, and legislation. Methodologies in individual countries are difficult to compare qualitatively. However, individual approaches can serve as examples for countries undergoing the process of developing new methodologies, either for legislative purposes or to improve environmental standards on watercourses. This is exactly the situation in the Czech Republic which, has been working on the Regulation of the Government of the Czech Republic for ten years, since the amendment to the Water Act in 2010, defines the methods and criteria for determining the MRF on watercourses. T.G. Masaryk Water Research Institute, p.r.i., was commissioned to develop a new methodology to serve as the basis for the wording of aforementioned regulation. The new methodological approach took into account modern trends concerning the preservation of ecological standards, and used standard hydrological characteristics for its calculations. The newly proposed approach is undergoing a complicated approval process as the authors seek to increase the MRF compared to the current approach. The new approach assumes an MRF setting between Q97 and Q90. It defines four areas within the Czech Republic, by their hydrological and hydrogeological conditions, where the MRF is determined in different ways. This article describes the development of a new methodological approach, including the use the available Czech Hydrometeorological Institute data sets, the proposed regional division for MRF calculations, the determination the MRF below reservoirs, and the current state of the issue. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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24 pages, 9316 KiB  
Article
Numerical Simulations of the Flow Field of a Submerged Hydraulic Jump over Triangular Macroroughnesses
by Amir Ghaderi, Mehdi Dasineh, Francesco Aristodemo and Costanza Aricò
Water 2021, 13(5), 674; https://doi.org/10.3390/w13050674 - 2 Mar 2021
Cited by 29 | Viewed by 5733
Abstract
The submerged hydraulic jump is a sudden change from the supercritical to subcritical flow, specified by strong turbulence, air entrainment and energy loss. Despite recent studies, hydraulic jump characteristics in smooth and rough beds, the turbulence, the mean velocity and the flow patterns [...] Read more.
The submerged hydraulic jump is a sudden change from the supercritical to subcritical flow, specified by strong turbulence, air entrainment and energy loss. Despite recent studies, hydraulic jump characteristics in smooth and rough beds, the turbulence, the mean velocity and the flow patterns in the cavity region of a submerged hydraulic jump in the rough beds, especially in the case of triangular macroroughnesses, are not completely understood. The objective of this paper was to numerically investigate via the FLOW-3D model the effects of triangular macroroughnesses on the characteristics of submerged jump, including the longitudinal profile of streamlines, flow patterns in the cavity region, horizontal velocity profiles, streamwise velocity distribution, thickness of the inner layer, bed shear stress coefficient, Turbulent Kinetic Energy (TKE) and energy loss, in different macroroughness arrangements and various inlet Froude numbers (1.7 < Fr1 < 9.3). To verify the accuracy and reliability of the present numerical simulations, literature experimental data were considered. Full article
(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)
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11 pages, 2868 KiB  
Article
The FLOod Probability Interpolation Tool (FLOPIT): A Simple Tool to Improve Spatial Flood Probability Quantification and Communication
by Mahkameh Zarekarizi, K. Joel Roop-Eckart, Sanjib Sharma and Klaus Keller
Water 2021, 13(5), 666; https://doi.org/10.3390/w13050666 - 1 Mar 2021
Cited by 2 | Viewed by 4210
Abstract
Understanding flood probabilities is essential to making sound decisions about flood-risk management. Many people rely on flood probability maps to inform decisions about purchasing flood insurance, buying or selling real-estate, flood-proofing a house, or managing floodplain development. Current flood probability maps typically use [...] Read more.
Understanding flood probabilities is essential to making sound decisions about flood-risk management. Many people rely on flood probability maps to inform decisions about purchasing flood insurance, buying or selling real-estate, flood-proofing a house, or managing floodplain development. Current flood probability maps typically use flood zones (for example the 1 in 100 or 1 in 500-year flood zones) to communicate flooding probabilities. However, this choice of communication format can miss important details and lead to biased risk assessments. Here we develop, test, and demonstrate the FLOod Probability Interpolation Tool (FLOPIT). FLOPIT interpolates flood probabilities between water surface elevation to produce continuous flood-probability maps. FLOPIT uses water surface elevation inundation maps for at least two return periods and creates Annual Exceedance Probability (AEP) as well as inundation maps for new return levels. Potential advantages of FLOPIT include being open-source, relatively easy to implement, capable of creating inundation maps from agencies other than FEMA, and applicable to locations where FEMA published flood inundation maps but not flood probability. Using publicly available data from the Federal Emergency Management Agency (FEMA) flood risk databases as well as state and national datasets, we produce continuous flood-probability maps at three example locations in the United States: Houston (TX), Muncy (PA), and Selinsgrove (PA). We find that the discrete flood zones generally communicate substantially lower flood probabilities than the continuous estimates. Full article
(This article belongs to the Section Hydrology)
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25 pages, 5952 KiB  
Article
Sustainable Surface Water Storage Development Pathways and Acceptable Limits for River Basins
by Nishadi Eriyagama, Vladimir Smakhtin and Lakshika Udamulla
Water 2021, 13(5), 645; https://doi.org/10.3390/w13050645 - 28 Feb 2021
Cited by 2 | Viewed by 4676
Abstract
This paper addresses the questions of acceptable upper limits for storage development and how best to deploy storage capacity in the long-term planning of built surface water storage in river basins. Storage-yield curves are used to establish sustainable storage development pathways and limits [...] Read more.
This paper addresses the questions of acceptable upper limits for storage development and how best to deploy storage capacity in the long-term planning of built surface water storage in river basins. Storage-yield curves are used to establish sustainable storage development pathways and limits for a basin under a range of environmental flow release scenarios. Optimal storage distribution at a sub-basin level, which complies with an identified storage development pathway, can also be estimated. Two new indices are introduced—Water Supply Sustainability and Environmental Flow Sustainability—to help decide which pathways and management strategies are the most appropriate for a basin. Average pathways and conservative and maximum storage limits are illustrated for two example basins. Conservative and maximum withdrawal limits from storage are in the range of 45–50% and 60–65% of the mean annual runoff. The approach can compare the current level of basin storage with an identified pathway and indicate which parts of a basin are over- or under-exploited. A global storage–yield–reliability relationship may also be developed using statistics of annual basin precipitation to facilitate water resource planning in ungauged basins. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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21 pages, 3670 KiB  
Article
Distributed-Framework Basin Modeling System: Ⅲ. Hydraulic Modeling System
by Xiaoning Li, Chuanhai Wang, Gang Chen, Xing Fang, Pingnan Zhang and Wenjuan Hua
Water 2021, 13(5), 649; https://doi.org/10.3390/w13050649 - 28 Feb 2021
Cited by 6 | Viewed by 2654
Abstract
A distributed-framework basin modeling system (DFBMS) was developed to simulate the runoff generation and movement on a basin scale. This study is part of a series of papers on DFBMS that focuses on the hydraulic calculation methods in runoff concentration on underlying surfaces [...] Read more.
A distributed-framework basin modeling system (DFBMS) was developed to simulate the runoff generation and movement on a basin scale. This study is part of a series of papers on DFBMS that focuses on the hydraulic calculation methods in runoff concentration on underlying surfaces and flow movement in river networks and lakes. This paper introduces the distributed-framework river modeling system (DF-RMS) that is a professional modeling system for hydraulic modeling. The DF-RMS contains different hydrological feature units (HFUs) to simulate the runoff movement through a system of rivers, storage units, lakes, and hydraulic structures. The river network simulations were categorized into different types, including one-dimensional river branch, dendritic river network, loop river network, and intersecting river network. The DF-RMS was applied to the middle and downstream portions of the Huai River Plain in China using different HFUs for river networks and lakes. The simulation results showed great consistency with the observed data, which proves that DF-RMS is a reliable system to simulate the flow movement in river networks and lakes. Full article
(This article belongs to the Special Issue Modelling Hydrologic Response of Non­-homogeneous Catchments)
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15 pages, 1032 KiB  
Article
Modeling the Effect of Different Forest Types on Water Balance in the Three Gorges Reservoir Area in China, with CoupModel
by Zhi Yang, Fang Hou, Jinhua Cheng and Youyan Zhang
Water 2021, 13(5), 654; https://doi.org/10.3390/w13050654 - 28 Feb 2021
Cited by 3 | Viewed by 2540
Abstract
Precipitation, throughfall, stemflow, and soil water content were measured, whereas interception, transpiration, evaporation, deep percolation, and soil water recharge were estimated in three plots, including oak (Lithocarpus glaber), Chinese fir (Cunninghamia lanceolata) forestlands, and maize (Zea mays) [...] Read more.
Precipitation, throughfall, stemflow, and soil water content were measured, whereas interception, transpiration, evaporation, deep percolation, and soil water recharge were estimated in three plots, including oak (Lithocarpus glaber), Chinese fir (Cunninghamia lanceolata) forestlands, and maize (Zea mays) farmland in the Three Gorges Reservoir in China. A physical process-based model (CoupModel) was set up with climatic measurements as input and was calibrated with throughfall and vertical frequency domain reflectometry measurements from January 2018 to December 2019. Simulated values of soil moisture were fairly consistent with measured ones, with a determination coefficient (R2) of 0.73–0.91. Evapotranspiration was the main output of water balance, with a percentage of up to 61%, and such output was ranked as follows: oak forest (720 mm/y) > Chinese fir forest (700 mm/y) > maize farmland (600 mm/y). Afforestation influenced water balance, and water recharge was generally less significant in oak forestland than in Chinese fir forestland. Annual simulated deep percolation decreased by 60 mm for oak and 47 mm for Chinese fir compared with that for farmland (452 mm/y) and even more significantly in wet years. This decrease was mainly attributed to increased interception (122–159 mm/y) and transpiration (49–84 mm/y) after afforestation. Simulations indicated that vegetation species significantly influenced the magnitude of water balance components, calling for further attention to the selection of regrown tree species in the planning for afforestation projects, particularly for such projects that aim to improve the quantity of water infiltrating groundwater. Soil and water conservation measures should also be applied scientifically when converting farmland to forest in this area, particularly in the oak forest stand. Full article
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29 pages, 2604 KiB  
Review
Electrocoagulation as a Promising Defluoridation Technology from Water: A Review of State of the Art of Removal Mechanisms and Performance Trends
by Milad Mousazadeh, S. M. Alizadeh, Zacharias Frontistis, Işık Kabdaşlı, Elnaz Karamati Niaragh, Zakaria Al Qodah, Zohreh Naghdali, Alaa El Din Mahmoud, Miguel A. Sandoval, Erick Butler and Mohammad Mahdi Emamjomeh
Water 2021, 13(5), 656; https://doi.org/10.3390/w13050656 - 28 Feb 2021
Cited by 68 | Viewed by 8956
Abstract
Fluoride ions present in drinking water are beneficial to human health when at proper concentration levels (0.5–1.5 mg L−1), but an excess intake of fluoride (>1.5 mg L−1) may pose several health problems. In this context, reducing high fluoride [...] Read more.
Fluoride ions present in drinking water are beneficial to human health when at proper concentration levels (0.5–1.5 mg L−1), but an excess intake of fluoride (>1.5 mg L−1) may pose several health problems. In this context, reducing high fluoride concentrations in water is a major worldwide challenge. The World Health Organization has recommended setting a permissible limit of 1.5 mg L−1. The application of electrocoagulation (EC) processes has received widespread and increasing attention as a promising treatment technology and a competitive treatment for fluoride control. EC technology has been favourably applied due to its economic effectiveness, environmental versatility, amenability of automation, and low sludge production. This review provides more detailed information on fluoride removal from water by the EC process, including operating parameters, removal mechanisms, energy consumption, and operating costs. Additionally, it also focuses attention on future trends related to improve defluoridation efficiency. Full article
(This article belongs to the Special Issue Application of Electrochemistry in Wastewater Treatment)
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20 pages, 7470 KiB  
Article
Groundwater-Potential Mapping Using a Self-Learning Bayesian Network Model: A Comparison among Metaheuristic Algorithms
by Sadegh Karimi-Rizvandi, Hamid Valipoori Goodarzi, Javad Hatami Afkoueieh, Il-Moon Chung, Ozgur Kisi, Sungwon Kim and Nguyen Thi Thuy Linh
Water 2021, 13(5), 658; https://doi.org/10.3390/w13050658 - 28 Feb 2021
Cited by 39 | Viewed by 4033
Abstract
Owing to the reduction of surface-water resources and frequent droughts, the exploitation of groundwater resources has faced critical challenges. For optimal management of these valuable resources, careful studies of groundwater potential status are essential. The main goal of this study was to determine [...] Read more.
Owing to the reduction of surface-water resources and frequent droughts, the exploitation of groundwater resources has faced critical challenges. For optimal management of these valuable resources, careful studies of groundwater potential status are essential. The main goal of this study was to determine the optimal network structure of a Bayesian network (BayesNet) machine-learning model using three metaheuristic optimization algorithms—a genetic algorithm (GA), a simulated annealing (SA) algorithm, and a Tabu search (TS) algorithm—to prepare groundwater-potential maps. The methodology was applied to the town of Baghmalek in the Khuzestan province of Iran. For modeling, the location of 187 springs in the study area and 13 parameters (altitude, slope angle, slope aspect, plan curvature, profile curvature, topography wetness index (TWI), distance to river, distance to fault, drainage density, rainfall, land use/cover, lithology, and soil) affecting the potential of groundwater were provided. In addition, the statistical method of certainty factor (CF) was utilized to determine the input weight of the hybrid models. The results of the OneR technique showed that the parameters of altitude, lithology, and drainage density were more important for the potential of groundwater compared to the other parameters. The results of groundwater-potential mapping (GPM) employing the receiver operating characteristic (ROC) area under the curve (AUC) showed an estimation accuracy of 0.830, 0.818, 0.810, and 0.792, for the BayesNet-GA, BayesNet-SA, BayesNet-TS, and BayesNet models, respectively. The BayesNet-GA model improved the GPM estimation accuracy of the BayesNet-SA (4.6% and 7.5%) and BayesNet-TS (21.8% and 17.5%) models with respect to the root mean square error (RMSE) and mean absolute error (MAE), respectively. Based on metric indices, the GA provides a higher capability than the SA and TS algorithms for optimizing the BayesNet model in determining the GPM. Full article
(This article belongs to the Section Hydrology)
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31 pages, 7154 KiB  
Review
A Review of 50 Years of Study of Hydrology, Wetland Dynamics, Aquatic Metabolism, Water Quality and Trophic Status, and Nutrient Biogeochemistry in the Barataria Basin, Mississippi Delta—System Functioning, Human Impacts and Restoration Approaches
by John W. Day, William H. Conner, Ronald D. DeLaune, Charles S. Hopkinson, Rachael G. Hunter, Gary P. Shaffer, Demetra Kandalepas, Richard F. Keim, G. Paul Kemp, Robert R. Lane, Victor H. Rivera-Monroy, Charles E. Sasser, John R. White and Ivan A. Vargas-Lopez
Water 2021, 13(5), 642; https://doi.org/10.3390/w13050642 - 27 Feb 2021
Cited by 31 | Viewed by 6246
Abstract
Here we review an extensive series of studies of Barataria Basin, an economically and ecologically important coastal basin of the Mississippi Delta. Human activity has greatly altered the hydrology of the basin by decreasing riverine inflows from leveeing of the river and its [...] Read more.
Here we review an extensive series of studies of Barataria Basin, an economically and ecologically important coastal basin of the Mississippi Delta. Human activity has greatly altered the hydrology of the basin by decreasing riverine inflows from leveeing of the river and its distributaries, increasing runoff with high nutrient concentrations from agricultural fields, and channelization of wetlands of the basin interior that has altered flow paths to often bypass wetlands. This has resulted in degraded water quality in the upper basin and wetland loss in the lower basin. Trophic state analysis found the upper basin to be eutrophic and the lower basin to be mesotrophic. Gross aquatic primary production (GAPP) was highest in the upper basin, lowest in the mid basin, and intermediate in the lower basin. Forested wetlands in the upper basin have degraded over the past several decades due to increased periods of flooding, while there has been massive loss of emergent wetlands in the lower basin due to increasing water levels and pervasive alteration of hydrology. Restoration will entail reconnection of waterways with surrounding wetlands in the upper basin, and implementation of river sediment diversions, marsh creation using dredged sediments and barrier island restoration. Findings from this review are discussed in terms of the functioning of deltas globally. Full article
(This article belongs to the Special Issue Sustainable Management, Conservation and Restoration in Deltaic Ecosystems with Special Emphasis on the Mississippi Delta)
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24 pages, 10585 KiB  
Article
Supply and Demand Forecasting of Water Resource Coupling System in Upstream Yangtze River under Changing Environmental Conditions
by Sijing Lou, Li Mo, Jianzhong Zhou, Yongqiang Wang and Wenhao He
Water 2021, 13(5), 640; https://doi.org/10.3390/w13050640 - 27 Feb 2021
Cited by 5 | Viewed by 3191
Abstract
The upstream Yangtze River is located in the southwest of central China, where it flows through several ecosystems and densely populated regions that constitute a unique complex coupled system. To determine how the characteristics of supply and demand in a water-coupled system will [...] Read more.
The upstream Yangtze River is located in the southwest of central China, where it flows through several ecosystems and densely populated regions that constitute a unique complex coupled system. To determine how the characteristics of supply and demand in a water-coupled system will vary under the influence of climate change and human activity in this area in the next 85 years, the upper Yangtze basin was considered as the study area and was divided into seven sub-basins according to seven main control sections: Shigu, Panzhihua, Xiluodu, Xiangjiaba, Zhutuo, Cuntan, and Yichang; a method for water supply and demand research considering climate change was proposed. Based on simulated runoff in the study area under changing environmental conditions, this study analyzed the available water supply and constructed a long-term water demand forecasting model using the classified water use index method under macro regulation in the study area from 2016 to 2100. The results show that the total water demand in the upstream Yangtze River appears to first increase and then decrease in 2016–2100 and will reach its peak around 2028. The ecological pressure in the upstream Yangtze River increases gradually from upstream to downstream but will not reach the surface water utilization stress threshold (hereinafter referred to as stress threshold) for the next 85 years. The contradiction between monthly supply and demand is more prominent under ecological restrictions. Under the RCP4.5 scenario, water demand exceeds the stress threshold in each sub-basin across several months (mainly March, April, and May), and the water demand nearly reaches the damage threshold in May as the basin extends below the Zhutuo section. Full article
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19 pages, 5870 KiB  
Article
Climatic Controls on Mean and Extreme Streamflow Changes Across the Permafrost Region of Canada
by Rajesh R. Shrestha, Jennifer Pesklevits, Daqing Yang, Daniel L. Peters and Yonas B. Dibike
Water 2021, 13(5), 626; https://doi.org/10.3390/w13050626 - 27 Feb 2021
Cited by 9 | Viewed by 3479
Abstract
Climatic change is affecting streamflow regimes of the permafrost region, altering mean and extreme streamflow conditions. In this study, we analyzed historical trends in annual mean flow (Qmean), minimum flow (Qmin), maximum flow (Qmax) and Qmax [...] Read more.
Climatic change is affecting streamflow regimes of the permafrost region, altering mean and extreme streamflow conditions. In this study, we analyzed historical trends in annual mean flow (Qmean), minimum flow (Qmin), maximum flow (Qmax) and Qmax timing across 84 hydrometric stations in the permafrost region of Canada. Furthermore, we related streamflow trends with temperature and precipitation trends, and used a multiple linear regression (MLR) framework to evaluate climatic controls on streamflow components. The results revealed spatially varied trends across the region, with significantly increasing (at 10% level) Qmin for 43% of stations as the most prominent trend, and a relatively smaller number of stations with significant Qmean, Qmax and Qmax timing trends. Temperatures over both the cold and warm seasons showed significant warming for >70% of basin areas upstream of the hydrometric stations, while precipitation exhibited increases for >15% of the basins. Comparisons of the 1976 to 2005 basin-averaged climatological means of streamflow variables with precipitation and temperature revealed a positive correlation between Qmean and seasonal precipitation, and a negative correlation between Qmean and seasonal temperature. The basin-averaged streamflow, precipitation and temperature trends showed weak correlations that included a positive correlation between Qmin and October to March precipitation trends, and negative correlations of Qmax timing with October to March and April to September temperature trends. The MLR-based variable importance analysis revealed the dominant controls of precipitation on Qmean and Qmax, and temperature on Qmin. Overall, this study contributes towards an enhanced understanding of ongoing changes in streamflow regimes and their climatic controls across the Canadian permafrost region, which could be generalized for the broader pan-Arctic regions. Full article
(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)
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16 pages, 3918 KiB  
Article
Human Health Risk Assessment for Exposure to Potentially Toxic Elements in Polluted Rivers in the Ecuadorian Amazon
by Samantha Jiménez-Oyola, Kenny Escobar Segovia, María-Jesús García-Martínez, Marcelo Ortega, David Bolonio, Iker García-Garizabal and Bryan Salgado
Water 2021, 13(5), 613; https://doi.org/10.3390/w13050613 - 26 Feb 2021
Cited by 27 | Viewed by 5923
Abstract
Anthropogenic activities performed in the Ecuadorian Amazon have released potentially toxic elements (PTEs) into the rivers, causing severe environmental pollution and increasing the risk of exposure to the residents of the surrounding areas. This study aims to carry out a human health risk [...] Read more.
Anthropogenic activities performed in the Ecuadorian Amazon have released potentially toxic elements (PTEs) into the rivers, causing severe environmental pollution and increasing the risk of exposure to the residents of the surrounding areas. This study aims to carry out a human health risk assessment using deterministic and probabilistic methods to estimate the hazard index (HI) and total cancer risk (TCR) related to multi-pathway human exposure to PTEs in polluted rivers. Concentrations of Al, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in surface water and sediment samples from rivers on the Ecuadorian Amazon were considered to assess the potential adverse human health effects. As a result, deterministic and probabilistic estimations of cancer and non-cancer risk through exposure to surface waters and sediments were above the safety limit. A sensitivity analysis identified the concentration of PTEs and the exposure duration (ED) as the two most important variables for probabilistic health risk assessment. The highest risk for receptors was related to exposure to polluted sediments through incidental ingestion and dermal contact routes. According to the deterministic estimation, the human health risk through ingestion of water was above the threshold in specific locations. This study reveals the potential health risk to which the population is exposed. This information can be used as a baseline to develop public strategies to reduce anthropogenic pollution and exposure to PTEs in Ecuadorian Amazon rivers. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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20 pages, 6437 KiB  
Article
Distributed-Framework Basin Modeling System: IV. Application in Taihu Basin
by Gang Chen, Chuanhai Wang, Xing Fang, Xiaoning Li, Pingnan Zhang and Wenjuan Hua
Water 2021, 13(5), 611; https://doi.org/10.3390/w13050611 - 26 Feb 2021
Cited by 9 | Viewed by 2750
Abstract
This paper presents the application of a distributed-framework basin modeling system (DFBMS) in Taihu Basin, China. The concepts of professional modeling systems and system integration/coupling have been summarized in the first three series papers. This study builds a hydrologic and hydrodynamic model for [...] Read more.
This paper presents the application of a distributed-framework basin modeling system (DFBMS) in Taihu Basin, China. The concepts of professional modeling systems and system integration/coupling have been summarized in the first three series papers. This study builds a hydrologic and hydrodynamic model for Taihu Basin, which is in the lowland plain areas with numerous polder areas. Digital underlying surface area data agree with the survey results from the water resource development and utilization. The runoff generated in each cell was calculated with the model based on the digital underlying surface data. According to the hydrological feature units (HFU) concept from the DFBMS, Taihu Basin was conceptualized into six different HFUs. The basic data of rainfall, evaporation, water surface elevation (WSE), discharge, tide level, and water resources for consumption and discharge in 2000 were used to calibrate the model. The simulated results of WSE and discharge matched the observed data well. The observed data of 1998, 1999, 2002, and 2003 were used to validate the model, with good agreement with the simulation results. Finally, the basic data from 2003 were used to simulate and evaluate the management scheme of water diversion from the Yangtze River to Taihu Lake. Overall, the DFBMS application in Taihu Basin showed good performance and proved that the proposed structure for DFBMS was effective and reliable. Full article
(This article belongs to the Special Issue Modelling Hydrologic Response of Non­-homogeneous Catchments)
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22 pages, 5919 KiB  
Article
Evaluating Vulnerability of Central Asian Water Resources under Uncertain Climate and Development Conditions: The Case of the Ili-Balkhash Basin
by Tesse de Boer, Homero Paltan, Troy Sternberg and Kevin Wheeler
Water 2021, 13(5), 615; https://doi.org/10.3390/w13050615 - 26 Feb 2021
Cited by 20 | Viewed by 10519
Abstract
The Ili-Balkhash basin (IBB) is considered a key region for agricultural development and international transport as part of China’s Belt and Road Initiative (BRI). The IBB is exemplary for the combined challenge of climate change and shifts in water supply and demand in [...] Read more.
The Ili-Balkhash basin (IBB) is considered a key region for agricultural development and international transport as part of China’s Belt and Road Initiative (BRI). The IBB is exemplary for the combined challenge of climate change and shifts in water supply and demand in transboundary Central Asian closed basins. To quantify future vulnerability of the IBB to these changes, we employ a scenario-neutral bottom-up approach with a coupled hydrological-water resource modelling set-up on the RiverWare modelling platform. This study focuses on reliability of environmental flows under historical hydro-climatic variability, future hydro-climatic change and upstream water demand development. The results suggest that the IBB is historically vulnerable to environmental shortages, and any increase in water consumption will increase frequency and intensity of shortages. Increases in precipitation and temperature improve reliability of flows downstream, along with water demand reductions upstream and downstream. Of the demand scenarios assessed, extensive water saving is most robust to climate change. However, the results emphasize the competition for water resources among up- and downstream users and between sectors in the lower Ili, underlining the importance of transboundary water management to mitigate cross-border impacts. The modelling tool and outcomes may aid decision-making under the uncertain future in the basin. Full article
(This article belongs to the Special Issue Feature Papers of Water, Agriculture and Aquaculture)
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18 pages, 5592 KiB  
Article
Climate Change Patterns of Wild Blueberry Fields in Downeast, Maine over the Past 40 Years
by Rafa Tasnim, Francis Drummond and Yong-Jiang Zhang
Water 2021, 13(5), 594; https://doi.org/10.3390/w13050594 - 25 Feb 2021
Cited by 21 | Viewed by 9078
Abstract
Maine, USA is the largest producer of wild blueberries (Vaccinium angustifolium Aiton), an important native North American fruit crop. Blueberry fields are mainly distributed in coastal glacial outwash plains which might not experience the same climate change patterns as the whole region. [...] Read more.
Maine, USA is the largest producer of wild blueberries (Vaccinium angustifolium Aiton), an important native North American fruit crop. Blueberry fields are mainly distributed in coastal glacial outwash plains which might not experience the same climate change patterns as the whole region. It is important to analyze the climate change patterns of wild blueberry fields and determine how they affect crop health so fields can be managed more efficiently under climate change. Trends in the maximum (Tmax), minimum (Tmin) and average (Tavg) temperatures, total precipitation (Ptotal), and potential evapotranspiration (PET) were evaluated for 26 wild blueberry fields in Downeast Maine during the growing season (May–September) over the past 40 years. The effects of these climate variables on the Maximum Enhanced Vegetation Index (EVImax) were evaluated using Remote Sensing products and Geographic Information System (GIS) tools. We found differences in the increase in growing season Tmax, Tmin, Tavg, and Ptotal between those fields and the overall spatial average for the region (state of Maine), as well as among the blueberry fields. The maximum, minimum, and average temperatures of the studied 26 wild blueberry fields in Downeast, Maine showed higher rates of increase than those of the entire region during the last 40 years. Fields closer to the coast showed higher rates of warming compared with the fields more distant from the coast. Consequently, PET has been also increasing in wild blueberry fields, with those at higher elevations showing lower increasing rates. Optimum climatic conditions (threshold values) during the growing season were explored based on observed significant quadratic relationships between the climate variables (Tmax and Ptotal), PET, and EVImax for those fields. An optimum Tmax and PET for EVImax at 22.4 °C and 145 mm/month suggest potential negative effects of further warming and increasing PET on crop health and productivity. These climate change patterns and associated physiological relationships, as well as threshold values, could provide important information for the planning and development of optimal management techniques for wild blueberry fields experiencing climate change. 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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29 pages, 2298 KiB  
Review
Advancing the Science of Environmental Flow Management for Protection of Temporarily Closed Estuaries and Coastal Lagoons
by Eric D. Stein, Eleanor M. Gee, Janine B. Adams, Katie Irving and Lara Van Niekerk
Water 2021, 13(5), 595; https://doi.org/10.3390/w13050595 - 25 Feb 2021
Cited by 36 | Viewed by 5303
Abstract
The science needed to inform management of environmental flows to temporarily closed estuaries and coastal lagoons is decades behind the state of knowledge for rivers and large embayments. These globally ubiquitous small systems, which are often seasonally closed to the ocean’s influence, are [...] Read more.
The science needed to inform management of environmental flows to temporarily closed estuaries and coastal lagoons is decades behind the state of knowledge for rivers and large embayments. These globally ubiquitous small systems, which are often seasonally closed to the ocean’s influence, are under particular threat associated with hydrologic alteration because of changes in atershed land use, water use practices, and climate change. Managing environmental flows in these systems is complicated by their tight coupling with watershed processes, variable states because of intermittently closing mouths, and reliance on regional scale sediment transport and littoral processes. Here we synthesize our current understanding of ecohydrology in temporarily closed estuaries (TCEs) and coastal lagoons and propose a prioritized research agenda aimed at advancing understanding of ecological responses to altered flow regimes in TCEs. Key research needs include agreeing on a consistent typology, improving models that couple watershed and ocean forcing at appropriate spatial and temporal scales, quantifying stress–response relationships associated with hydrologic alteration, improving tools to establish desired conditions that account for climate change and consider cultural/indigenous objectives, improving tools to measure ecosystem function and social/cultural values, and developing monitoring and adaptive management programs that can inform environmental flow management in consideration of other stressors and across different habitat types. Coordinated global efforts to address the identified research gaps can help guide management actions aimed at reducing or mitigating potential impacts of hydrologic alteration and climate change through informed management of freshwater inflows. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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17 pages, 11528 KiB  
Article
Transfer Learning with Convolutional Neural Networks for Rainfall Detection in Single Images
by Nicla Maria Notarangelo, Kohin Hirano, Raffaele Albano and Aurelia Sole
Water 2021, 13(5), 588; https://doi.org/10.3390/w13050588 - 24 Feb 2021
Cited by 24 | Viewed by 5592
Abstract
Near real-time rainfall monitoring at local scale is essential for urban flood risk mitigation. Previous research on precipitation visual effects supports the idea of vision-based rain sensors, but tends to be device-specific. We aimed to use different available photographing devices to develop a [...] Read more.
Near real-time rainfall monitoring at local scale is essential for urban flood risk mitigation. Previous research on precipitation visual effects supports the idea of vision-based rain sensors, but tends to be device-specific. We aimed to use different available photographing devices to develop a dense network of low-cost sensors. Using Transfer Learning with a Convolutional Neural Network, the rainfall detection was performed on single images taken in heterogeneous conditions by static or moving cameras without adjusted parameters. The chosen images encompass unconstrained verisimilar settings of the sources: Image2Weather dataset, dash-cams in the Tokyo Metropolitan area and experiments in the NIED Large-scale Rainfall Simulator. The model reached a test accuracy of 85.28% and an F1 score of 0.86. The applicability to real-world scenarios was proven with the experimentation with a pre-existing surveillance camera in Matera (Italy), obtaining an accuracy of 85.13% and an F1 score of 0.85. This model can be easily integrated into warning systems to automatically monitor the onset and end of rain-related events, exploiting pre-existing devices with a parsimonious use of economic and computational resources. The limitation is intrinsic to the outputs (detection without measurement). Future work concerns the development of a CNN based on the proposed methodology to quantify the precipitation intensity. Full article
(This article belongs to the Special Issue Observation-Driven Understanding, Prediction, and Management in Hydrological/Hydraulic Hazard and Risk Studies)
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24 pages, 9555 KiB  
Article
Mapping Groundwater Potential Zones Using a Knowledge-Driven Approach and GIS Analysis
by Qiande Zhu and Mohamed Abdelkareem
Water 2021, 13(5), 579; https://doi.org/10.3390/w13050579 - 24 Feb 2021
Cited by 75 | Viewed by 6866
Abstract
Despite the Sahara being one of the most arid regions on Earth, it has experienced rainfall conditions in the past and could hold plentiful groundwater resources. Thus, groundwater is one of the most precious water resources in this region, which suffers from water [...] Read more.
Despite the Sahara being one of the most arid regions on Earth, it has experienced rainfall conditions in the past and could hold plentiful groundwater resources. Thus, groundwater is one of the most precious water resources in this region, which suffers from water shortage due to the limited rainfall caused by climatic conditions. This article will assess the knowledge-driven techniques employed to develop a model to integrate the multicriteria derived from geologic, geomorphic, structural, seismic, hydrologic, and remotely sensed data. This model was tested on the defunct Kom Ombo area of Egypt’s Nile river basin in the eastern Sahara, which covers ~28,200 km2, to reveal the promising areas of groundwater resources. To optimize the output map, we updated the model by adding the automated depression resulting from a fill-difference approach and seismic activity layers combined with other evidential maps, including slope, topography, geology, drainage density, lineament density, soil characteristics, rainfall, and morphometric characteristics, after assigning a weight for each using a Geographic Information System (GIS)-based knowledge-driven approach. The paleochannels and soil characteristics were visualized using Advanced Land Observing Satellite (ALOS)/Phased Array type L-band Synthetic Aperture Radar (PALSAR) data. Several hydromorphic characteristics, sinks/depressions, and sub-basin characteristics were extracted using Shuttle Radar Topography Mission (SRTM) data. The results revealed that the assessed groundwater potential zones (GPZs) can be arranged into five distinctive groups, depending on their probability for groundwater, namely very low (6.56%), low (22.62%), moderate (30.75%), high (29.71%), and very high (10.34%). The downstream areas and Wadi Garara have very high recharge and storage potential. Interferometry Synthetic Aperture Radar (InSAR) coherence change detection (CCD) derived from Sentinel-1 data revealed a consistency between areas with high InSAR CCD (low change) that received a plausible amount of surface water and those with very low InSAR CCD values close to 0 (high change). Landsat data validated the areas that received runoff and are of high potentiality. The twenty-nine groundwater well locations overlaid on the GPZs, to assess the predicted model, indicated that about 86.17% of the wells were matched with very good to moderate potential zones. Full article
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18 pages, 1851 KiB  
Article
Monitoring Groundwater Use as a Domestic Water Source by Urban Households: Analysis of Data from Lagos State, Nigeria and Sub-Saharan Africa with Implications for Policy and Practice
by Kerstin Danert and Adrian Healy
Water 2021, 13(4), 568; https://doi.org/10.3390/w13040568 - 23 Feb 2021
Cited by 17 | Viewed by 7815
Abstract
The fundamental importance of groundwater for urban drinking water supplies in sub-Saharan Africa is increasingly recognised. However, little is known about the trends in urban groundwater development by individual households and its role in securing safely-managed drinking water supplies. Anecdotal evidence indicates a [...] Read more.
The fundamental importance of groundwater for urban drinking water supplies in sub-Saharan Africa is increasingly recognised. However, little is known about the trends in urban groundwater development by individual households and its role in securing safely-managed drinking water supplies. Anecdotal evidence indicates a thriving self-supply movement to exploit groundwater in some urban sub-Saharan African settings, but empirical evidence, or analysis of the benefits and drawbacks, remains sparse. Through a detailed analysis of official datasets for Lagos State, Nigeria we examine the crucial role played by groundwater and, specifically, by household self-supply for domestic water provision. We then set this in the context of Nigeria and of sub-Saharan Africa. One of the novelties of this multi-scalar approach is that it provides a granular understanding from large-scale datasets. Our analysis confirms the importance of non-piped water supplies in meeting current and future drinking water demand by households in parts of sub-Saharan Africa and the role played, through self-supply, by groundwater. Our results demonstrate inconsistencies between datasets, and we make recommendations for the future. We argue that a key actor in the provision of drinking water supplies, the individual household, is largely overlooked by officially reported data, with implications for both policy and practice. Full article
(This article belongs to the Special Issue Present and Future of Drinking Water Supplies in Low-Income Regions)
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19 pages, 11841 KiB  
Article
Trend Analyses of Baseflow and BFI for Undisturbed Watersheds in Michigan—Constraints from Multi-Objective Optimization
by Benjamin Hagedorn and Christina Meadows
Water 2021, 13(4), 564; https://doi.org/10.3390/w13040564 - 23 Feb 2021
Cited by 7 | Viewed by 4482
Abstract
Documenting how ground- and surface water systems respond to climate change is crucial to understanding water resources, particularly in the U.S. Great Lakes region, where drastic temperature and precipitation changes are observed. This study presents baseflow and baseflow index (BFI) trend analyses for [...] Read more.
Documenting how ground- and surface water systems respond to climate change is crucial to understanding water resources, particularly in the U.S. Great Lakes region, where drastic temperature and precipitation changes are observed. This study presents baseflow and baseflow index (BFI) trend analyses for 10 undisturbed watersheds in Michigan using (1) multi-objective optimization (MOO) and (2) modified Mann–Kendall (MK) tests corrected for short-term autocorrelation (STA). Results indicate a variability in mean baseflow (0.09–8.70 m3/s) and BFI (67.9–89.7%) that complicates regional-scale extrapolations of groundwater recharge. Long-term (>60 years) MK trend tests indicate a significant control of total precipitation (P) and snow- to rainfall transitions on baseflow and BFI. In the Lower Peninsula Rifle River watershed, increasing P and a transition from snow- to rainfall has increased baseflow at a lower rate than streamflow; an overall pattern that may contribute to documented flood frequency increases. In the Upper Peninsula Ford River watershed, decreasing P and a transition from rain- to snowfall had no significant effects on baseflow and BFI. Our results highlight the value of an objectively constrained BFI parameter for shorter-term (<50 years) hydrologic trend analysis because of a lower STA susceptibility. Full article
(This article belongs to the Section Hydrology)
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23 pages, 5453 KiB  
Article
Assessing Multi-Hazard Vulnerability and Dynamic Coastal Flood Risk in the Mississippi Delta: The Global Delta Risk Index as a Social-Ecological Systems Approach
by Carl C. Anderson, Fabrice G. Renaud, Michael Hagenlocher and John W. Day
Water 2021, 13(4), 577; https://doi.org/10.3390/w13040577 - 23 Feb 2021
Cited by 20 | Viewed by 8177
Abstract
The tight coupling of the social-ecological system (SES) of the Mississippi Delta calls for balanced natural hazard vulnerability and risk assessments. Most existing assessments have approached these components in isolation. To address this, we apply the Global Delta Risk Index (GDRI) in the [...] Read more.
The tight coupling of the social-ecological system (SES) of the Mississippi Delta calls for balanced natural hazard vulnerability and risk assessments. Most existing assessments have approached these components in isolation. To address this, we apply the Global Delta Risk Index (GDRI) in the Mississippi Delta at high-resolution census tract level. We assess SES spatial patterns of drought, hurricane-force wind, and coastal flood vulnerability and integrate hazard and exposure data for the assessment of coastal flood risk. Moreover, we compare current coastal flood risk to future risk in 2025 based on the modelled effects of flood depth, exposure, and changes in ecosystem area in the context of ongoing efforts under the 2017 Louisiana Coastal Master Plan. Results show that the Master Plan will lead to decreases in risk scores by 2025, but the tracts that are currently the most vulnerable benefit less from risk reduction efforts. Along with our index output, we discuss the need for further advancements in SES methodology and the potential for catastrophic hazard events beyond the model parameters, such as extreme rainfall events and very strong hurricanes. Assessing SES risk components can lead to more targeted policy recommendations, demonstrated by the need for Master Plan projects to consider their unequal spatial effects on vulnerability and risk reduction. Full article
(This article belongs to the Special Issue Sustainable Management, Conservation and Restoration in Deltaic Ecosystems with Special Emphasis on the Mississippi Delta)
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16 pages, 3191 KiB  
Article
Deep Learning Framework with Time Series Analysis Methods for Runoff Prediction
by Zhenghe Li, Ling Kang, Liwei Zhou and Modi Zhu
Water 2021, 13(4), 575; https://doi.org/10.3390/w13040575 - 23 Feb 2021
Cited by 27 | Viewed by 6200
Abstract
Recent advances in deep learning, especially the long short-term memory (LSTM) networks, provide some useful insights on how to tackle time series prediction problems, not to mention the development of a time series model itself for prediction. Runoff forecasting is a time series [...] Read more.
Recent advances in deep learning, especially the long short-term memory (LSTM) networks, provide some useful insights on how to tackle time series prediction problems, not to mention the development of a time series model itself for prediction. Runoff forecasting is a time series prediction problem with a series of past runoff data (water level and discharge series data) as inputs and a fixed-length series of future runoff as output. Most previous work paid attention to the sufficiency of input data and the structural complexity of deep learning, while less effort has been put into the consideration of data quantity or the processing of original input data—such as time series decomposition, which can better capture the trend of runoff—or unleashing the effective potential of deep learning. Mutual information and seasonal trend decomposition are two useful time series methods in handling data quantity analysis and original data processing. Based on a former study, we proposed a deep learning model combined with time series analysis methods for daily runoff prediction in the middle Yangtze River and analyzed its feasibility and usability with frequently used counterpart models. Furthermore, this research also explored the data quality that affect the performance of the deep learning model. With the application of the time series method, we can effectively get some information about the data quality and data amount that we adopted in the deep learning model. The comparison experiment resulted in two different sites, implying that the proposed model improved the precision of runoff prediction and is much easier and more effective for practical application. In short, time series analysis methods can exert great potential of deep learning in daily runoff prediction and may unleash great potential of artificial intelligence in hydrology research. Full article
(This article belongs to the Special Issue Research of the Relationship between Climate Change and Runoff in Watershed)
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20 pages, 2765 KiB  
Article
A Forecast-Skill-Based Dynamic Pre-Storm Level Control for Reservoir Flood-Control Operation
by Wenhua Wan, Xiaohui Lei, Jianshi Zhao, Mingna Wang, Soon-Thiam Khu and Chao Wang
Water 2021, 13(4), 556; https://doi.org/10.3390/w13040556 - 22 Feb 2021
Cited by 6 | Viewed by 3378
Abstract
The design and operation of reservoirs based on conventional flood-limited water levels (FLWL) implicitly adopts the assumption of hydrological stationarity. As such, historical-record-based FLWL may not be the best choice for flood-control operations due to the inherent non-stationarity of rainfall inputs. With maturing [...] Read more.
The design and operation of reservoirs based on conventional flood-limited water levels (FLWL) implicitly adopts the assumption of hydrological stationarity. As such, historical-record-based FLWL may not be the best choice for flood-control operations due to the inherent non-stationarity of rainfall inputs. With maturing flood forecasts, this study focuses on establishing linkage between FLWL and skill of forecast, thus developing a “dynamic pre-storm level” approach for reservoir flood-control operations. The approach utilizes forecast flood magnitude, forecast skill and exceedance probability of forecast error to determine the pre-storm reservoir storage for each flood event. The exceedance probability of forecast error for each incoming flood is used as the reservoir flood control standard instead of the probability of a static return interval flood. This approach is demonstrated in a hypothetical situation in the Three Gorges Reservoir in China. The results show that under zero-forecast-skill conditions, the proposed dynamic pre-storm level matches well with the Three Gorges Reservoir-designed FLWL; and, as the forecast accuracy/skill increase, the proposed approach can make better use of the increased forecast accuracy, thereby maximizing floodwater utilization and reservoir storage. In this way, coupling the new approach with FLWL allows for more efficient and economic day-to-day reservoir operations without adding any flood risk. This study validates the usefulness of dynamic water level control during flood season, considering the improvement of flood forecast accuracy. Full article
(This article belongs to the Special Issue Sustainable Development of Lakes and Reservoirs)
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23 pages, 3630 KiB  
Review
Salt Marsh Hydrogeology: A Review
by Julia Guimond and Joseph Tamborski
Water 2021, 13(4), 543; https://doi.org/10.3390/w13040543 - 20 Feb 2021
Cited by 57 | Viewed by 10060
Abstract
Groundwater–surface water exchange in salt marsh ecosystems mediates nearshore salt, nutrient, and carbon budgets with implications for biological productivity and global climate. Despite their importance, a synthesis of salt marsh groundwater studies is lacking. In this review, we summarize drivers mediating salt marsh [...] Read more.
Groundwater–surface water exchange in salt marsh ecosystems mediates nearshore salt, nutrient, and carbon budgets with implications for biological productivity and global climate. Despite their importance, a synthesis of salt marsh groundwater studies is lacking. In this review, we summarize drivers mediating salt marsh hydrogeology, review field and modeling techniques, and discuss patterns of exchange. New data from a Delaware seepage meter study are reported which highlight small-scale spatial variability in exchange rates. A synthesis of the salt marsh hydrogeology literature reveals a positive relationship between tidal range and submarine groundwater discharge but not porewater exchange, highlighting the multidimensional drivers of marsh hydrogeology. Field studies are heavily biased towards microtidal systems of the US East Coast, with little global information available. A preliminary estimate of marsh porewater exchange along the Mid-Atlantic and South Atlantic Bights is 8–30 × 1013 L y−1, equivalent to recirculating the entire volume of seawater overlying the shelf through tidal marsh sediments in ~30–90 years. This review concludes with a discussion of critical questions to address that will decrease uncertainty in global budget estimates and enhance our capacity to predict future responses to global climate change. Full article
(This article belongs to the Special Issue Advances in the Study and Understanding of Groundwater Discharge to Surface Water)
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18 pages, 2985 KiB  
Article
Prediction of Combined Terrestrial Evapotranspiration Index (CTEI) over Large River Basin Based on Machine Learning Approaches
by Ahmed Elbeltagi, Nikul Kumari, Jaydeo K. Dharpure, Ali Mokhtar, Karam Alsafadi, Manish Kumar, Behrouz Mehdinejadiani, Hadi Ramezani Etedali, Youssef Brouziyne, Abu Reza Md. Towfiqul Islam and Alban Kuriqi
Water 2021, 13(4), 547; https://doi.org/10.3390/w13040547 - 20 Feb 2021
Cited by 68 | Viewed by 6343
Abstract
Drought is a fundamental physical feature of the climate pattern worldwide. Over the past few decades, a natural disaster has accelerated its occurrence, which has significantly impacted agricultural systems, economies, environments, water resources, and supplies. Therefore, it is essential to develop new techniques [...] Read more.
Drought is a fundamental physical feature of the climate pattern worldwide. Over the past few decades, a natural disaster has accelerated its occurrence, which has significantly impacted agricultural systems, economies, environments, water resources, and supplies. Therefore, it is essential to develop new techniques that enable comprehensive determination and observations of droughts over large areas with satisfactory spatial and temporal resolution. This study modeled a new drought index called the Combined Terrestrial Evapotranspiration Index (CTEI), developed in the Ganga river basin. For this, five Machine Learning (ML) techniques, derived from artificial intelligence theories, were applied: the Support Vector Machine (SVM) algorithm, decision trees, Matern 5/2 Gaussian process regression, boosted trees, and bagged trees. These techniques were driven by twelve different models generated from input combinations of satellite data and hydrometeorological parameters. The results indicated that the eighth model performed best and was superior among all the models, with the SVM algorithm resulting in an R2 value of 0.82 and the lowest errors in terms of the Root Mean Squared Error (RMSE) (0.33) and Mean Absolute Error (MAE) (0.20), followed by the Matern 5/2 Gaussian model with an R2 value of 0.75 and RMSE and MAE of 0.39 and 0.21 mm/day, respectively. Moreover, among all the five methods, the SVM and Matern 5/2 Gaussian methods were the best-performing ML algorithms in our study of CTEI predictions for the Ganga basin. Full article
(This article belongs to the Section Hydrology)
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17 pages, 6314 KiB  
Article
Hydrochemical and Isotopic Characterization of the Waters of the Manglaralto River Basin (Ecuador) to Contribute to the Management of the Coastal Aquifer
by Paúl Carrión-Mero, F. Javier Montalván, Fernando Morante-Carballo, Javier Heredia, F. Javier Elorza, Joselyne Solórzano and Héctor Aguilera
Water 2021, 13(4), 537; https://doi.org/10.3390/w13040537 - 19 Feb 2021
Cited by 17 | Viewed by 4970
Abstract
Coastal aquifers are strategic and fundamental in the development of touristic areas. The coastal aquifer within the Manglaralto River Basin in Ecuador is essential, as it is the only source of water supply for a large part of the northern part of the [...] Read more.
Coastal aquifers are strategic and fundamental in the development of touristic areas. The coastal aquifer within the Manglaralto River Basin in Ecuador is essential, as it is the only source of water supply for a large part of the northern part of the Santa Elena province. It is a semi-arid region where high volumes of water are pumped from the aquifer, causing a significant drawdown of groundwater levels, thus affecting the water quality. This work aims to characterize the characteristics of groundwater in the coastal aquifer using hydrochemistry and stable isotopes to propose a hydrogeological conceptual model. The methodology for determining the chemical and isotopic characteristics of groundwater follows the following scheme: (i) studies of ionic concentrations using the Piper diagram, (ii) assessment of the origin of salinity through the Cl/Br ratio, the presence of seawater intrusion through the Hydrochemical Facies Evolution Diagram HFE-D, (iii) characterization of precipitation events using stable isotopes (18O and 2H), and, (iv) development of a hydrogeological conceptual model of the study area. The results indicate that in the basin there are mixing processes of the existing water in the aquifer with recharge water, direct cation exchange processes in the freshening process during recharge, and evaporation in the unsaturated zone. A conceptual model of the flow system in the basin is built, based on the mentioned processes. The main conclusions are: seawater intrusion is present in the areas of the wells located closest to the coast, urban activity through septic tanks is affecting the quality of the aquifer, and rainfall is highly relevant in the different hydrochemical and isotopic processes that operate in the basin. Full article
(This article belongs to the Special Issue Geochemistry of Groundwater)
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26 pages, 4937 KiB  
Article
Comparison of Multicriteria Decision-Making Techniques for Groundwater Recharge Potential Zonation: Case Study of the Willochra Basin, South Australia
by Alaa Ahmed, Chathuri Ranasinghe-Arachchilage, Abdullah Alrajhi and Guna Hewa
Water 2021, 13(4), 525; https://doi.org/10.3390/w13040525 - 18 Feb 2021
Cited by 24 | Viewed by 4320
Abstract
In semi-arid regions, groundwater resources play a crucial role in all economic, environmental, and social processes. However, the occurrence, movement, and recharge of these hidden and valuable resources vary from place to place. Therefore, better management practices and mapping of groundwater recharge potential [...] Read more.
In semi-arid regions, groundwater resources play a crucial role in all economic, environmental, and social processes. However, the occurrence, movement, and recharge of these hidden and valuable resources vary from place to place. Therefore, better management practices and mapping of groundwater recharge potential zones are needed for the sustainable groundwater resources. For an example, groundwater resources in Willochra Basin are vitally important for drinking, irrigation, and stock use. This study shows the significance of the application of three decision-making approaches, including multi-influencing factor, analytical hierarchy process, and frequency ratio techniques in the identification of groundwater potential zones. A total of seven criteria, including lithology, slope, soil texture, land-use, rainfall, drainage density, and lineament density, were extracted from conventional and remote sensing data sources. The parameters and their assigned weights were integrated using Geographic Information System (GIS) software to generate recharge potential maps. The resultant maps were evaluated using the area under the curve method. The results showed that the southern regions of the Willochra Basin are more promising for groundwater recharge potential. The map produced using the frequency ratio model was the most efficient (84%), followed by the multi-influencing factor model (70%) and then the analytical hierarchy process technique (62%). The area under the curve method agreed when evaluated using published weights and rating values. Full article
(This article belongs to the Special Issue Water and Irrigation Management in Arid and Semiarid Zones)
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17 pages, 5608 KiB  
Article
Distribution of Groundwater Arsenic in Uruguay Using Hybrid Machine Learning and Expert System Approaches
by Ruohan Wu, Elena M. Alvareda, David A. Polya, Gonzalo Blanco and Pablo Gamazo
Water 2021, 13(4), 527; https://doi.org/10.3390/w13040527 - 18 Feb 2021
Cited by 23 | Viewed by 5861
Abstract
Groundwater arsenic in Uruguay is an important environmental hazard, hence, predicting its distribution is important to inform stakeholders. Furthermore, occurrences in Uruguay are known to variably show dependence on depth and geology, arguably reflecting different processes controlling groundwater arsenic concentrations. Here, we present [...] Read more.
Groundwater arsenic in Uruguay is an important environmental hazard, hence, predicting its distribution is important to inform stakeholders. Furthermore, occurrences in Uruguay are known to variably show dependence on depth and geology, arguably reflecting different processes controlling groundwater arsenic concentrations. Here, we present the distribution of groundwater arsenic in Uruguay modelled by a variety of machine learning, basic expert systems, and hybrid approaches. A pure random forest approach, using 26 potential predictor variables, gave rise to a groundwater arsenic distribution model with a very high degree of accuracy (AUC = 0.92), which is consistent with known high groundwater arsenic hazard areas. These areas are mainly in southwest Uruguay, including the Paysandú, Río Negro, Soriano, Colonia, Flores, San José, Florida, Montevideo, and Canelones departments, where the Mercedes, Cuaternario Oeste, Raigón, and Cretácico main aquifers occur. A hybrid approach separating the country into sedimentary and crystalline aquifer domains resulted in slight material improvement in a high arsenic hazard distribution. However, a further hybrid approach separately modelling shallow (<50 m) and deep aquifers (>50 m) resulted in the identification of more high hazard areas in Flores, Durazno, and the northwest corner of Florida departments in shallow aquifers than the pure model. Both hybrid models considering depth (AUC = 0.95) and geology (AUC = 0.97) produced improved accuracy. Hybrid machine learning models with expert selection of important environmental parameters may sometimes be a better choice than pure machine learning models, particularly where there are incomplete datasets, but perhaps, counterintuitively, this is not always the case. Full article
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24 pages, 3455 KiB  
Article
The Development of a Framework for the Integrated Assessment of SDG Trade-Offs in the Sundarban Biosphere Reserve
by Charlotte L. J. Marcinko, Robert J. Nicholls, Tim M. Daw, Sugata Hazra, Craig W. Hutton, Chris T. Hill, Derek Clarke, Andy Harfoot, Oindrila Basu, Isha Das, Sandip Giri, Sudipa Pal and Partho P. Mondal
Water 2021, 13(4), 528; https://doi.org/10.3390/w13040528 - 18 Feb 2021
Cited by 27 | Viewed by 9562
Abstract
The United Nations Sustainable Development Goals (SDGs) and their corresponding targets are significantly interconnected, with many interactions, synergies, and trade-offs between individual goals across multiple temporal and spatial scales. This paper proposes a framework for the Integrated Assessment Modelling (IAM) of a complex [...] Read more.
The United Nations Sustainable Development Goals (SDGs) and their corresponding targets are significantly interconnected, with many interactions, synergies, and trade-offs between individual goals across multiple temporal and spatial scales. This paper proposes a framework for the Integrated Assessment Modelling (IAM) of a complex deltaic socio-ecological system in order to analyze such SDG interactions. We focused on the Sundarban Biosphere Reserve (SBR), India, within the Ganges-Brahmaputra-Meghna Delta. It is densely populated with 4.4 million people (2011), high levels of poverty, and a strong dependence on rural livelihoods. It is adjacent to the growing megacity of Kolkata. The area also includes the Indian portion of the world’s largest mangrove forest––the Sundarbans––hosting the iconic Bengal Tiger. Like all deltaic systems, this area is subject to multiple drivers of environmental change operating across scales. The IAM framework is designed to investigate socio-environmental change under a range of explorative and/or normative scenarios and explore associated policy impacts, considering a broad range of subthematic SDG indicators. The following elements were explicitly considered: (1) agriculture; (2) aquaculture; (3) mangroves; (4) fisheries; and (5) multidimensional poverty. Key questions that can be addressed include the implications of changing monsoon patterns, trade-offs between agriculture and aquaculture, or the future of the Sundarbans’ mangroves under sea-level rise and different management strategies. The novel, high-resolution analysis of SDG interactions allowed by the IAM will provide stakeholders and policy makers the opportunity to prioritize and explore the SDG targets that are most relevant to the SBR and provide a foundation for further integrated analysis. Full article
(This article belongs to the Special Issue Sustainable Management, Conservation and Restoration in Deltaic Ecosystems with Special Emphasis on the Mississippi Delta)
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20 pages, 1895 KiB  
Article
The U.S.-Mexico Transboundary Aquifer Assessment Program as a Model for Transborder Groundwater Collaboration
by Elia M. Tapia-Villaseñor and Sharon B. Megdal
Water 2021, 13(4), 530; https://doi.org/10.3390/w13040530 - 18 Feb 2021
Cited by 23 | Viewed by 5527
Abstract
The assessment of transboundary aquifers is essential for the development of groundwater management strategies and the sustainable use of groundwater resources. The Transboundary Aquifer Assessment Program (TAAP) is a joint effort by the United States and Mexico to evaluate shared aquifers. This study [...] Read more.
The assessment of transboundary aquifers is essential for the development of groundwater management strategies and the sustainable use of groundwater resources. The Transboundary Aquifer Assessment Program (TAAP) is a joint effort by the United States and Mexico to evaluate shared aquifers. This study examines the TAAP Cooperative Framework as a guide for further transboundary groundwater collaboration. We compared lessons learned from six transboundary aquifers that currently have mechanisms for groundwater collaboration to identify common elements of collaboration. Though the TAAP Cooperative Framework governs an assessment-only program, the elements of collaboration included are consistent with the principles of other institutional agreements around the world. Importantly, all the analyzed agreements included a knowledge-improvement phase, which is the main objective of the TAAP Cooperative Framework. The present study finds evidence of successful outcomes within the TAAP Cooperative Framework consistent with available transboundary groundwater management agreements, demonstrating that this approach is suited to serve as a model for those wishing to engage in transborder aquifer assessments. Furthermore, the TAAP elements of collaboration can help to establish the meaningful and robust binational cooperation necessary for the development of U.S.-Mexico groundwater management agreements at the aquifer level. Full article
(This article belongs to the Special Issue Advances in Transboundary Aquifer Assessment)
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22 pages, 6752 KiB  
Article
A Planning Tool for Optimizing Investment to Reduce Drinking Water Risk to Multiple Water Treatment Plants in Open Catchments
by Chris Thompson, Morag Stewart, Nick Marsh, Viet Phung and Thomas Lynn
Water 2021, 13(4), 531; https://doi.org/10.3390/w13040531 - 18 Feb 2021
Viewed by 3139
Abstract
Supplying safe, secure, and reliable drinking water is a growing challenge particularly in regions where catchments have diverse land uses, rapidly growing populations, and are subject to increasing weather extremes such as in the subtropics. Catchments represent the first barrier in providing ecosystem [...] Read more.
Supplying safe, secure, and reliable drinking water is a growing challenge particularly in regions where catchments have diverse land uses, rapidly growing populations, and are subject to increasing weather extremes such as in the subtropics. Catchments represent the first barrier in providing ecosystem services for water quality protection and bulkwater suppliers are therefore investing in mitigation measures to reduce risk to drinking water quality for consumers. This paper presents an approach to combine data on erosion processes, pathogenic bacteria and protozoa from several sources, determine the highest risks from these hazards and identify an optimum portfolio of intervention activities that provide maximum risk reduction at water treatment plants (WTP) for a given budget using a simulated annealing optimizer. The approach is demonstrated in a catchment with six WTPs servicing small rural to urban populations. The catchment is predominantly used for agriculture. Results show that drinking water risk from protozoa can be reduced for most WTPs for moderate investment budget, while bacteria risk reduction requires significantly larger budget due to the greater number of significant source sites relative to protozoa. Total suspended sediment loads remain a very high risk to most of the WTPs due to the large extent of channel and gully erosion and landslides. A map of priority areas and associated suite of interventions are produced to guide on groundwork. Full article
(This article belongs to the Special Issue Impact of Land-Use Changes on Surface Hydrology and Water Quality)
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15 pages, 807 KiB  
Article
Building the Treaty #3 Nibi Declaration Using an Anishinaabe Methodology of Ceremony, Language and Engagement
by Aimée Craft and Lucas King
Water 2021, 13(4), 532; https://doi.org/10.3390/w13040532 - 18 Feb 2021
Cited by 18 | Viewed by 6205
Abstract
Ratified in 2019, the Nibi Declaration of Treaty #3 voices the relationship with water (Nibi) and jurisdictional responsibility that all Anishinaabe citizens have within the Treaty #3 territory. It affirms the responsibilities and relationships that others living within the territory should have with [...] Read more.
Ratified in 2019, the Nibi Declaration of Treaty #3 voices the relationship with water (Nibi) and jurisdictional responsibility that all Anishinaabe citizens have within the Treaty #3 territory. It affirms the responsibilities and relationships that others living within the territory should have with the water and ensures that the spirit of Nibi is central to decision-making and water governance. This article details the process of developing The Declaration, in accordance with the Treaty #3 lawmaking process and, which was driven by women, in ceremony, with the help of Gitiizii m-inaanik, and with the input of The Nation as a whole. This process embodies nationhood, sovereignty, and Anishinaabe jurisdiction as it relates to the environment and water, in accordance with the Manito Aki Inakonigaawin (Mother Earth law). Every person has a relationship with water. The process of nurturing that relationship through the teachings exemplified in the implementation of The Declaration will provide clarity on the responsibilities and partnerships that must be developed to protect the water for future generations. Full article
(This article belongs to the Special Issue Sustainable Water Governance through Indigenous Research Approaches)
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17 pages, 5472 KiB  
Article
Operational Implementation of Satellite-Rain Gauge Data Merging for Hydrological Modeling
by Alejandra De Vera, Pablo Alfaro and Rafael Terra
Water 2021, 13(4), 533; https://doi.org/10.3390/w13040533 - 18 Feb 2021
Cited by 10 | Viewed by 4059
Abstract
Systems exposed to hydroclimatic variability, such as the integrated electric system in Uruguay, increasingly require real-time multiscale information to optimize management. Monitoring of the precipitation field is key to inform the future hydroelectric energy availability. We present an operational implementation of an algorithm [...] Read more.
Systems exposed to hydroclimatic variability, such as the integrated electric system in Uruguay, increasingly require real-time multiscale information to optimize management. Monitoring of the precipitation field is key to inform the future hydroelectric energy availability. We present an operational implementation of an algorithm that merges satellite precipitation estimates with rain gauge data, based on a 3-step technique: (i) Regression of station data on the satellite estimate using a Generalized Linear Model; (ii) Interpolation of the regression residuals at station locations to the entire grid using Ordinary Kriging and (iii) Application of a rain/no rain mask. The operational implementation follows five steps: (i) Data download and daily accumulation; (ii) Data quality control; (iii) Merging technique; (iv) Hydrological modeling and (v) Electricity-system simulation. The hydrological modeling is carried with the GR4J rainfall-runoff model applied to 17 sub-catchments of the G. Terra basin with routing up to the reservoir. The implementation became operational at the Electricity Market Administration (ADME) on June 2020. The performance of the merged precipitation estimate was evaluated through comparison with an independent, dense and uniformly distributed rain gauge network using several relevant statistics. Further validation is presented comparing the simulated inflow to the estimate derived from a reservoir mass budget. Results confirm that the estimation that incorporates the satellite information in addition to the surface observations has a higher performance than the one that only uses rain gauge data, both in the rainfall statistical evaluation and hydrological simulation. Full article
(This article belongs to the Special Issue Hydrometeorological Observation and Modeling)
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18 pages, 3662 KiB  
Article
Inclusion of Hydraulic Controls in Rehabilitation Models of Drainage Networks to Control Floods
by Leonardo Bayas-Jiménez, F. Javier Martínez-Solano, Pedro L. Iglesias-Rey, Daniel Mora-Melia and Vicente S. Fuertes-Miquel
Water 2021, 13(4), 514; https://doi.org/10.3390/w13040514 - 17 Feb 2021
Cited by 3 | Viewed by 3584
Abstract
A problem for drainage systems managers is the increase in extreme rain events that are increasing in various parts of the world. Their occurrence produces hydraulic overload in the drainage system and consequently floods. Adapting the existing infrastructure to be able to receive [...] Read more.
A problem for drainage systems managers is the increase in extreme rain events that are increasing in various parts of the world. Their occurrence produces hydraulic overload in the drainage system and consequently floods. Adapting the existing infrastructure to be able to receive extreme rains without generating consequences for cities’ inhabitants has become a necessity. This research shows a new way to improve drainage systems with minimal investment costs, using for this purpose a novel methodology that considers the inclusion of hydraulic control elements in the network, the installation of storm tanks and the replacement of pipes. The presented methodology uses the Storm Water Management Model for the hydraulic analysis of the network and a modified Genetic Algorithm to optimize the network. In this algorithm, called the Pseudo-Genetic Algorithm, the coding of the chromosomes is integral and has been used in previous studies of hydraulic optimization. This work evaluates the cost of the required infrastructure and the damage caused by floods to find the optimal solution. The main conclusion of this study is that the inclusion of hydraulic controls can reduce the cost of network rehabilitation and decrease flood levels. Full article
(This article belongs to the Special Issue Urban Hydraulic Engineering Simulation and Calculation)
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20 pages, 2105 KiB  
Review
Phosphorus Removal from Wastewater: The Potential Use of Biochar and the Key Controlling Factors
by Khatereh Nobaharan, Sepideh Bagheri Novair, Behnam Asgari Lajayer and Eric D. van Hullebusch
Water 2021, 13(4), 517; https://doi.org/10.3390/w13040517 - 17 Feb 2021
Cited by 75 | Viewed by 14200
Abstract
In recent years, a large volume of literature has been published regarding the removal of phosphorus (P) from wastewater. Various sorbing materials, such as metal oxides and hydroxides, carbonates and hydroxides of calcium (Ca) and magnesium (Mg), hydrotalcite, activated carbon, anion exchange resins, [...] Read more.
In recent years, a large volume of literature has been published regarding the removal of phosphorus (P) from wastewater. Various sorbing materials, such as metal oxides and hydroxides, carbonates and hydroxides of calcium (Ca) and magnesium (Mg), hydrotalcite, activated carbon, anion exchange resins, industrial solid wastes and organic solid wastes, have been suggested for P removal. Many of these sorbents are expensive and/or may cause some environmental problems. In contrast, biochar, as an economical and environmentally friendly sorbing material, has received much attention in recent years and has been used as a novel sorbent for the removal of different organic and inorganic pollutants. Biochar is a type of sustainable carbonaceous material that is produced from the thermal treatment of agricultural organic residues and other organic waste streams under oxygen free conditions. This paper reviews the potential use of biochar and the key controlling factors affecting P removal from wastewater. The ability of biochar to remove P from wastewater depends on its physical and chemical properties. Some of the most important physicochemical properties of biochar (structural characteristics, electrical conductivity (EC), mineral composition, pH, zeta potential, cation exchange capacity (CEC) and anion exchange capacity (AEC)) are affected by the feedstock type as well as temperature of pyrolysis and the P sorption capacity is highly dependent on these properties. The P removal is also affected by the water matrix chemistry, such as the presence of competing ions and bulk pH conditions. Finally, several recommendations for future research have been proposed to facilitate and enhance the environmental efficiency of biochar application. Full article
(This article belongs to the Special Issue Biotechnological Wastewater Treatment for Pollution Control and Resource Recovery)
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19 pages, 1056 KiB  
Review
Modelling Watershed and River Basin Processes in Cold Climate Regions: A Review
by Junye Wang, Narayan Kumar Shrestha, Mojtaba Aghajani Delavar, Tesfa Worku Meshesha and Soumendra N. Bhanja
Water 2021, 13(4), 518; https://doi.org/10.3390/w13040518 - 17 Feb 2021
Cited by 17 | Viewed by 5643
Abstract
Watersheds in cold regions provide water, food, biodiversity and ecosystem service. However, the increasing demand for water resources and climate change challenge our ability to provide clean freshwater. Particularly, watersheds in cold regions are more sensitive to changing climate due to their glaciers’ [...] Read more.
Watersheds in cold regions provide water, food, biodiversity and ecosystem service. However, the increasing demand for water resources and climate change challenge our ability to provide clean freshwater. Particularly, watersheds in cold regions are more sensitive to changing climate due to their glaciers’ retreat and permafrost. This review revisits watershed system and processes. We analyze principles of watershed modelling and characteristics of watersheds in cold regions. Then, we show observed evidence of their impacts of cold processes on hydrological and biogeochemical processes and ecosystems, and review the watershed modeling and their applications in cold regions. Finally, we identify the knowledge gaps in modeling river basins according to model structures and representations of processes and point out research priorities in future model development. Full article
(This article belongs to the Special Issue Integrated Watershed Management Modeling)
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15 pages, 1598 KiB  
Article
An Initial Framework for Understanding the Resilience of Aquifers to Groundwater Pumping
by África de la Hera-Portillo, Julio López-Gutiérrez, Beatriz Mayor, Elena López-Gunn, Hans Jørgen Henriksen, Ryle Nørskov Gejl, Pedro Zorrilla-Miras and Pedro Martínez-Santos
Water 2021, 13(4), 519; https://doi.org/10.3390/w13040519 - 17 Feb 2021
Cited by 5 | Viewed by 3323
Abstract
Groundwater stored in aquifers experiences a wide variety of natural, induced and/or anthropogenic disturbances. Among them, groundwater extraction is the main disturbance that affects most of the aquifers in the world. Aquifer’s resilience, understood as the potential of the aquifer to sustain disturbances [...] Read more.
Groundwater stored in aquifers experiences a wide variety of natural, induced and/or anthropogenic disturbances. Among them, groundwater extraction is the main disturbance that affects most of the aquifers in the world. Aquifer’s resilience, understood as the potential of the aquifer to sustain disturbances on the long term and to guarantee essential qualities and functions, provides a key tool when assessing sustainable groundwater management alternatives. The aim of this work is to illustrate an aquifer resilience framework that can support groundwater sustainable management. A theoretical framework is based on the identification of the key variables that parameterize the quantitative and qualitative responses of the groundwater flow system to pumping. An example from the literature based in Denmark is provided as an illustration of the proposed framework. The results show that long-term high quality data are essential to make a step further in aquifers dynamic responses. The quantitative understanding of the aquifer’s behavior before, during and after groundwater extraction provides a valuable source of information in order to identify thresholds of change (tipping points, transitions or regime shifts) which could permit pro-active groundwater management decisions. Moreover, a deeper understanding on the aquifer’s dynamics provides useful information in order to avert threats that may put the sustainability of the system at risk. Full article
(This article belongs to the Special Issue Water Management to Protect Aquatic Ecosystems Function and Health in the Face of Climate Change)
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