Water

18 pages, 21201 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Controls on Streamflow Densities in Semiarid Rocky Mountain Catchments

by Caroline Martin, Stephanie K. Kampf, John C. Hammond, Codie Wilson and Suzanne P. Anderson

Water 2021, 13(4), 521; https://doi.org/10.3390/w13040521 - 17 Feb 2021

Cited by 9 | Viewed by 3299

Developing accurate stream maps requires both an improved understanding of the drivers of streamflow spatial patterns and field verification. This study examined streamflow locations in three semiarid catchments across an elevation gradient in the Colorado Front Range, USA. The locations of surface flow [...] Read more.

Developing accurate stream maps requires both an improved understanding of the drivers of streamflow spatial patterns and field verification. This study examined streamflow locations in three semiarid catchments across an elevation gradient in the Colorado Front Range, USA. The locations of surface flow throughout each channel network were mapped in the field and used to compute active drainage densities. Field surveys of active flow were compared to National Hydrography Dataset High Resolution (NHD HR) flowlines, digital topographic data, and geologic maps. The length of active flow declined with stream discharge in each of the catchments, with the greatest decline in the driest catchment. Of the tributaries that did not dry completely, 60% had stable flow heads and the remaining tributaries had flow heads that moved downstream with drying. The flow heads were initiated at mean contributing areas of 0.1 km² at the lowest elevation catchment and 0.5 km² at the highest elevation catchment, leading to active drainage densities that declined with elevation and snow persistence. The field mapped drainage densities were less than half the drainage densities that were represented using NHD HR. Geologic structures influenced the flow locations, with multiple flow heads initiated along faults and some tributaries following either fault lines or lithologic contacts. Full article

(This article belongs to the Special Issue Hydrology, Geomorphology, and Ecology of Intermittent Rivers and Streams)

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20 pages, 8470 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Pore Water Pressure and Piping of Hydraulic Well

by Jinman Kim, Heuisoo Han and Yoonhwa Jin

Water 2021, 13(4), 502; https://doi.org/10.3390/w13040502 - 15 Feb 2021

Cited by 1 | Viewed by 2687

Abstract

This paper shows the results of a field appliance study of the hydraulic well method to prevent embankment piping, which is proposed by the Japanese Matsuyama River National Highway Office. The large-scale embankment experiment and seepage analysis were conducted to examine the hydraulic [...] Read more.

This paper shows the results of a field appliance study of the hydraulic well method to prevent embankment piping, which is proposed by the Japanese Matsuyama River National Highway Office. The large-scale embankment experiment and seepage analysis were conducted to examine the hydraulic well. The experimental procedure is focused on the pore water pressure. The water levels of the hydraulic well were compared with pore water pressure data, which were used to look over the seepage variations. Two different types of large-scale experiments were conducted according to the installation points of hydraulic wells. The seepage velocity results by the experiment were almost similar to those of the analyses. Further, the pore water pressure oriented from the water level variations in the hydraulic well showed similar patterns between the experiment and numerical analysis; however, deeper from the surface, the larger pore water pressure of the numerical analysis was calculated compared to the experimental values. In addition, the piping effect according to the water level and location of the hydraulic well was quantitatively examined for an embankment having a piping guide part. As a result of applying the hydraulic well to the point where piping occurred, the hydraulic well with a 1.0 m water level reduced the seepage velocity by up to 86%. This is because the difference in the water level between the riverside and the protected side is reduced, and it resulted in reducing the seepage pressure. As a result of the theoretical and numerical hydraulic gradient analysis according to the change in the water level of the hydraulic well, the hydraulic gradient decreased linearly according to the water level of the hydraulic well. From the results according to the location of the hydraulic well, installation of it at the point where piping occurred was found to be the most effective. A hydraulic well is a good device for preventing the piping of an embankment if it is installed at the piping point and the proper water level of the hydraulic well is applied. Full article

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

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17 pages, 2733 KiB

Open AccessEditor’s ChoiceArticle

Assessing the Potential of Agricultural Reservoirs as the Source of Environmental Flow

by Young-Jun Jo, Jung-Hun Song, Younggu Her, Giorgio Provolo, Jina Beom, Minhyuk Jeung, Young-Joo Kim, Seung-Hwan Yoo and Kwang-Sik Yoon

Water 2021, 13(4), 508; https://doi.org/10.3390/w13040508 - 15 Feb 2021

Cited by 8 | Viewed by 3711

Abstract

Excessive nutrient loadings from drainage areas and resulting water quality degradation in rivers are the major environmental issues around the world. The water quality further deteriorates for the large seasonal variation of precipitation and water flow. Environmental decision makers have been exploring affordable [...] Read more.

Excessive nutrient loadings from drainage areas and resulting water quality degradation in rivers are the major environmental issues around the world. The water quality further deteriorates for the large seasonal variation of precipitation and water flow. Environmental decision makers have been exploring affordable and effective ways of securing environmental flow (EF) to improve the water quality, especially in dry seasons, and agricultural reservoirs have attracted the attention of policymakers as an alternative source of EF. This study proposed an analysis framework for assessing the EF supply potential of agricultural reservoirs as alternative sources of EF. A reservoir water balance model was prepared to mathematically represent the reservoir water balance and quantify temporal variations of the amount of water available for the EF supply. The simulation model was designed to explicitly consider inflow from the upstream drainage areas, irrigation water requirement, and hydrological processes happening in the reservoirs. The proposed framework was applied to four agricultural reservoirs located in South Korea to evaluate its efficiency. Results showed that the additional storage capacity added by the dam reinforcement enabled the study reservoirs to satisfy both needs, EF and irrigation water supply. The surplus capacity turned out to be enough to satisfy various EF supply scenarios at the annual time scale. However, the current operation plans do not consider the seasonal variations of reservoir hydrology and thus cannot supply EF without violating the original operational goal, irrigation water, especially in dry months. The results demonstrate that it is necessary to consider the temporal variations of EF when developing reservoir operation rules and plans to secure EF. This study also highlights the unconventional roles of agricultural reservoirs as resources for improved environmental quality. The methods presented in this study are expected to be a useful tool for the assessment of agricultural reservoirs’ EF supply potential. Full article

(This article belongs to the Special Issue Water Management for Agricultural, Environmental and Urban Uses)

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22 pages, 5223 KiB

Open AccessEditor’s ChoiceArticle

Reconstructing Spatiotemporal Dynamics in Hydrological State Along Intermittent Rivers

by Michael Eastman, Simon Parry, Catherine Sefton, Juhyun Park and Judy England

Water 2021, 13(4), 493; https://doi.org/10.3390/w13040493 - 14 Feb 2021

Cited by 7 | Viewed by 3917

Abstract

Despite the impact of flow cessation on aquatic ecology, the hydrology of intermittent rivers has been largely overlooked. This has resulted in a lack of monitoring projects, and consequently, datasets spanning a period of sufficient duration to characterise both hydrological extremes. This report [...] Read more.

Despite the impact of flow cessation on aquatic ecology, the hydrology of intermittent rivers has been largely overlooked. This has resulted in a lack of monitoring projects, and consequently, datasets spanning a period of sufficient duration to characterise both hydrological extremes. This report documents an investigation into the potential for statistical modelling to simulate the spatiotemporal dynamics of flowing, ponded and dry hydrological states in an internationally rare hydrological state dataset. The models presented predict unrecorded hydrological state data with performance metrics exceeding 95%, providing insights into the relationship between ponding prevalence and the performance of statistical simulation of this ecologically important intermediate state between drying and flowing conditions. This work demonstrates the potential for hydrological intermittence to be simulated in areas where hydrological state data are often sparse, providing opportunities for quality control and data infilling. This further understanding of the processes driving intermittence will inform future water resource assessments and the influence of climate change on hydrological intermittence. Full article

(This article belongs to the Special Issue Hydrology, Geomorphology, and Ecology of Intermittent Rivers and Streams)

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18 pages, 4243 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Intensive Agriculture on Benthic Macroinvertebrate Assemblages and Water Quality in the Aconcagua River Basin (Central Chile)

by Pablo Fierro, Claudio Valdovinos, Carlos Lara and Gonzalo S. Saldías

Water 2021, 13(4), 492; https://doi.org/10.3390/w13040492 - 14 Feb 2021

Cited by 19 | Viewed by 4637

Abstract

This study assessed natural variation in the macroinvertebrate assemblages (MIB) and water quality in one of the main basins with the largest agricultural activities in Chile (Aconcagua River Basin). We sampled throughout the annual cycle; nine sampling sites were established along the basin, [...] Read more.

This study assessed natural variation in the macroinvertebrate assemblages (MIB) and water quality in one of the main basins with the largest agricultural activities in Chile (Aconcagua River Basin). We sampled throughout the annual cycle; nine sampling sites were established along the basin, classifying according to agricultural area coverage as least-disturbed, intermediate, and most-disturbed. We collected 56 macroinvertebrate taxa throughout the entire study area. Multivariate analysis shows significant differences among the three disturbance categories in different seasons, both water quality variables and the MIB structure. Distance-based linear model (DistLM) analysis for all seasons explained more than 95.9% of the macroinvertebrate assemblages, being significantly explained by chemical oxygen demand, pH, total coliforms, nitrites, elevation, and water temperature. ANOVA test revealed significant differences in the proportion of noninsect individuals, macroinvertebrates density, and the number of taxa among the three disturbance categories (p < 0.05). In general, water temperature, conductivity, chemical oxygen demand, ammonium, nitrites, and nitrates increased their values downstream in the basin. Our results indicate that the elevation gradient and increment in agricultural land use in the basin had a strong influence on water quality and MIB. A better understanding of these ecosystems could help conservation and integrated watershed management. Full article

(This article belongs to the Special Issue Impact of Land-Use Changes on Surface Hydrology and Water Quality)

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19 pages, 7032 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Seasonal Variations of Dissolved Organic Matter by Fluorescent Analysis in a Typical River Catchment in Northern China

by Zenglei Han, Min Xiao, Fujun Yue, Yuanbi Yi and K. M. G. Mostofa

Water 2021, 13(4), 494; https://doi.org/10.3390/w13040494 - 14 Feb 2021

Cited by 21 | Viewed by 3749

Abstract

Fluorescence (excitation-emission matrices, EEMs) spectroscopy coupled with PARAFAC (parallel factor) modelling and UV-Vis (ultraviolet visible) spectra were used to ascertain the sources, distribution and biogeochemical transformation of dissolved organic matter (DOM) in the Duliujian River catchment. Dissolved organic carbon (DOC), chromophoric dissolved organic [...] Read more.

Fluorescence (excitation-emission matrices, EEMs) spectroscopy coupled with PARAFAC (parallel factor) modelling and UV-Vis (ultraviolet visible) spectra were used to ascertain the sources, distribution and biogeochemical transformation of dissolved organic matter (DOM) in the Duliujian River catchment. Dissolved organic carbon (DOC), chromophoric dissolved organic matter (a₃₃₅) (CDOM), and hydrophobic components (a₂₆₀) were higher in summer than in other seasons with 53.3 m⁻¹, while aromaticity (SUVA₂₅₄) was higher in spring. Four fluorescent components, namely terrestrial humic acid (HA)-like (A/C), terrestrial fulvic acid (FA)-like (A/M), autochthonous fulvic acid (FA)-like (A/M), and protein-like substances (Tuv/T), were identified using EEM-PARAFAC modelling in this river catchment. The results demonstrated that terrestrial HA-like substances enhance its contents in summer ARE compared with BRE, whilst terrestrial FA-like substances were newly input in summer ARE, which was entirely absent upstream and downstream, suggesting that rain events could significantly input the terrestrial soil-derived DOM in the ambient downward catchments. Autochthonous FA-like substances in summer BRE could derive from phytoplankton in the downstream waters. The results also showed that DOM from wetland exhibited lower fluorescent intensity of humic-like peak A/C and fulvic-like peak A/M, molecular weight (S_R) and humification index (HIX) during the low-flow season. Built-up land, cropland, and unused land displayed higher a₃₃₅ (CDOM). A higher proportion of forest and industrial land in the SCs showed higher SUVA₂₅₄ values. Humic-like moiety, molecular weight and aromaticity were more responsive to land use during stormflow in summer. Rainfall could increase the export of soil DOM from cropland and unused land, which influences the spatial variation of HIX. The results in this study highlighted that terrestrial DOM has a significant influence on the biogeochemical alterations of DOM compositions and thus water quality in the downward watershed catchments, which might significantly vary according to the land-use types and their alterations by human activities. Full article

(This article belongs to the Section Hydrology)

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26 pages, 5654 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modelling of the Discharge Response to Climate Change under RCP8.5 Scenario in the Alata River Basin (Mersin, SE Turkey)

by Ümit Yıldırım, Cüneyt Güler, Barış Önol, Michael Rode and Seifeddine Jomaa

Water 2021, 13(4), 483; https://doi.org/10.3390/w13040483 - 13 Feb 2021

Cited by 16 | Viewed by 5205

Abstract

This study investigates the impacts of climate change on the hydrological response of a Mediterranean mesoscale catchment using a hydrological model. The effect of climate change on the discharge of the Alata River Basin in Mersin province (Turkey) was assessed under the worst-case [...] Read more.

This study investigates the impacts of climate change on the hydrological response of a Mediterranean mesoscale catchment using a hydrological model. The effect of climate change on the discharge of the Alata River Basin in Mersin province (Turkey) was assessed under the worst-case climate change scenario (i.e., RCP8.5), using the semi-distributed, process-based hydrological model Hydrological Predictions for the Environment (HYPE). First, the model was evaluated temporally and spatially and has been shown to reproduce the measured discharge consistently. Second, the discharge was predicted under climate projections in three distinct future periods (i.e., 2021–2040, 2046–2065 and 2081–2100, reflecting the beginning, middle and end of the century, respectively). Climate change projections showed that the annual mean temperature in the Alata River Basin rises for the beginning, middle and end of the century, with about 1.35, 2.13 and 4.11 °C, respectively. Besides, the highest discharge timing seems to occur one month earlier (February instead of March) compared to the baseline period (2000–2011) in the beginning and middle of the century. The results show a decrease in precipitation and an increase in temperature in all future projections, resulting in more snowmelt and higher discharge generation in the beginning and middle of the century scenarios. However, at the end of the century, the discharge significantly decreased due to increased evapotranspiration and reduced snow depth in the upstream area. The findings of this study can help develop efficient climate change adaptation options in the Levant’s coastal areas. Full article

(This article belongs to the Special Issue Research of the Relationship between Climate Change and Runoff in Watershed)

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15 pages, 831 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Utilization of Biomass Derived from Cyanobacteria-Based Agro-Industrial Wastewater Treatment and Raisin Residue Extract for Bioethanol Production

by Olga N. Tsolcha, Vasiliki Patrinou, Christina N. Economou, Marianna Dourou, George Aggelis and Athanasia G. Tekerlekopoulou

Water 2021, 13(4), 486; https://doi.org/10.3390/w13040486 - 13 Feb 2021

Cited by 40 | Viewed by 4222

Abstract

Biofuels produced from photosynthetic microorganisms such as microalgae and cyanobacteria could potentially replace fossil fuels as they offer several advantages over fuels produced from lignocellulosic biomass. In this study, energy production potential in the form of bioethanol was examined using different biomasses derived [...] Read more.

Biofuels produced from photosynthetic microorganisms such as microalgae and cyanobacteria could potentially replace fossil fuels as they offer several advantages over fuels produced from lignocellulosic biomass. In this study, energy production potential in the form of bioethanol was examined using different biomasses derived from the growth of a cyanobacteria-based microbial consortium on a chemical medium and on agro-industrial wastewaters (i.e., dairy wastewater, winery wastewater and mixed winery–raisin effluent) supplemented with a raisin residue extract. The possibility of recovering fermentable sugars from a microbial biomass dominated by the filamentous cyanobacterium Leptolynbgya sp. was demonstrated. Of the different acid hydrolysis conditions tested, the best results were obtained with sulfuric acid 2.5 N for 120 min using dried biomass from dairy wastewater and mixed winery–raisin wastewaters. After optimizing sugar release from the microbial biomass by applying acid hydrolysis, alcoholic fermentation was performed using the yeast Saccharomyces cerevisiae. Raisin residue extract was added to the treated biomass broth in all experiments to enhance ethanol production. Results showed that up to 85.9% of the theoretical ethanol yield was achieved, indicating the potential use of cyanobacteria-based biomass in combination with a raisin residue extract as feedstock for bioethanol production. Full article

(This article belongs to the Special Issue Application of Circular Economy Principles in Water and Wastewater Utilities)

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24 pages, 13996 KiB

Open AccessEditor’s ChoiceArticle

Rainfall-Induced Shallow Landslide Detachment, Transit and Runout Susceptibility Mapping by Integrating Machine Learning Techniques and GIS-Based Approaches

by Mariano Di Napoli, Diego Di Martire, Giuseppe Bausilio, Domenico Calcaterra, Pierluigi Confuorto, Marco Firpo, Giacomo Pepe and Andrea Cevasco

Water 2021, 13(4), 488; https://doi.org/10.3390/w13040488 - 13 Feb 2021

Cited by 50 | Viewed by 6386

Abstract

Rainfall-induced shallow landslides represent a serious threat in hilly and mountain areas around the world. The mountainous landscape of the Cinque Terre (eastern Liguria, Italy) is increasingly popular for both Italian and foreign tourists, most of which visit this outstanding terraced coastal [...] Read more.

Rainfall-induced shallow landslides represent a serious threat in hilly and mountain areas around the world. The mountainous landscape of the Cinque Terre (eastern Liguria, Italy) is increasingly popular for both Italian and foreign tourists, most of which visit this outstanding terraced coastal landscape to enjoy a beach holiday and to practice hiking. However, this area is characterized by a high level of landslide hazard due to intense rainfalls that periodically affect its rugged and steep territory. One of the most severe events occurred on 25 October 2011, causing several fatalities and damage for millions of euros. To adequately address the issues related to shallow landslide risk, it is essential to develop landslide susceptibility models as reliable as possible. Regrettably, most of the current land-use and urban planning approaches only consider the susceptibility to landslide detachment, neglecting transit and runout processes. In this study, the adoption of a combined approach allowed to estimate shallow landslide susceptibility to both detachment and potential runout. At first, landslide triggering susceptibility was assessed using Machine Learning techniques and applying the Ensemble approach. Nine predisposing factors were chosen, while a database of about 300 rainfall-induced shallow landslides was used as input. Then, a Geographical Information System (GIS)-based procedure was applied to estimate the potential landslide runout using the “reach angle” method. Information from such analyses was combined to obtain a susceptibility map describing detachment, transit, and runout. The obtained susceptibility map will be helpful for land planning, as well as for decision makers and stakeholders, to predict areas where rainfall-induced shallow landslides are likely to occur in the future and to identify areas where hazard mitigation measures are needed. Full article

(This article belongs to the Special Issue Rainfall-Induced Shallow Landslides Modeling and Warning)

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16 pages, 12277 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Use of Constructed Wetland for Mitigating Nitrogen and Phosphorus from Agricultural Runoff: A Review

by Jiayu Li, Bohong Zheng, Xiao Chen, Zhe Li, Qi Xia, Hua Wang, Yuan Yang, Yaoyu Zhou and Hong Yang

Water 2021, 13(4), 476; https://doi.org/10.3390/w13040476 - 12 Feb 2021

Cited by 49 | Viewed by 14055

Abstract

The loss of nitrogen and phosphate fertilizers in agricultural runoff is a global environmental problem, attracting worldwide attention. In the last decades, the constructed wetland has been increasingly used for mitigating the loss of nitrogen and phosphate from agricultural runoff, while the substrate, [...] Read more.

The loss of nitrogen and phosphate fertilizers in agricultural runoff is a global environmental problem, attracting worldwide attention. In the last decades, the constructed wetland has been increasingly used for mitigating the loss of nitrogen and phosphate from agricultural runoff, while the substrate, plants, and wetland structure design remain far from clearly understood. In this paper, the optimum substrates and plant species were identified by reviewing their treatment capacity from the related studies. Specifically, the top three suitable substrates are gravel, zeolite, and slag. In terms of the plant species, emergent plants are the most widely used in the constructed wetlands. Eleocharis dulcis, Typha orientalis, and Scirpus validus are the top three optimum emergent plant species. Submerged plants (Hydrilla verticillata, Ceratophyllum demersum, and Vallisneria natans), free-floating plants (Eichhornia crassipes and Lemna minor), and floating-leaved plants (Nymphaea tetragona and Trapa bispinosa) are also promoted. Moreover, the site selection methods for constructed wetland were put forward. Because the existing research results have not reached an agreement on the controversial issue, more studies are still needed to draw a clear conclusion of effective structure design of constructed wetlands. This review has provided some recommendations for substrate, plant species, and site selections for the constructed wetlands to reduce nutrients from agricultural runoff. Full article

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

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23 pages, 3439 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Use of Fixed and Variable Speed Pumps in Water Distribution Networks with Different Control Strategies

by Christian X. Briceño-León, Pedro L. Iglesias-Rey, F. Javier Martinez-Solano, Daniel Mora-Melia and Vicente S. Fuertes-Miquel

Water 2021, 13(4), 479; https://doi.org/10.3390/w13040479 - 12 Feb 2021

Cited by 15 | Viewed by 5956

Abstract

The control system’s point is to bring the pumping curve close to the set-point curve. That concept is essential for proper design of a pumping station. An adequate design is focused not only on selecting the total number of pumps and the type [...] Read more.

The control system’s point is to bring the pumping curve close to the set-point curve. That concept is essential for proper design of a pumping station. An adequate design is focused not only on selecting the total number of pumps and the type of control to use (flow or pressure), but it also is important to determine the optimal number of fixed speed pumps (FSPs) and variable speed pumps (VSPs) for each flow rate. This work discusses the most common methods and procedures for control systems on a design of pumping stations with a proposed methodology. This methodology consists of expressing the characteristics of the pumping curve and the set-point curve in a dimensionless form so that the methodology is standardized for any pump model and set-point curve. These formulations allow us to discuss how the characteristic of a pump and the set-point curve of the network influence the optimal number of FSPs and VSPs in energy terms. In general, the objective of this work is to determine the most suitable total number of pumps in a pumping station design and to determine the optimal pumping configuration in every flow rate, thus the consumed energy would be the minimum. Additionally, this methodology develops an expression to estimate the performance of a frequency inverter when a VSP operates at different rotational speeds. This work will be applied to different study cases, and the obtained results allow us to question several usual procedures for pumping control system. In general, it can be concluded that the number of pumps of a pumping system cannot be inferred in a simple form without a deep analysis of a control system. Full article

(This article belongs to the Special Issue Urban Hydraulic Engineering Simulation and Calculation)

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21 pages, 9591 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Advantages of the Open Levee (Kasumi-Tei), a Traditional Japanese River Technology on the Matsuura River, from an Ecosystem-Based Disaster Risk Reduction Perspective

by Jun Teramura and Yukihiro Shimatani

Water 2021, 13(4), 480; https://doi.org/10.3390/w13040480 - 12 Feb 2021

Cited by 13 | Viewed by 5096

Abstract

Large-scale disasters, such as hurricanes, cyclones, tsunamis, and forest fires, have caused considerable damage in recent years. This study investigated two case studies of discontinuous open levees (kasumi-tei), which are a traditional Japanese river technology, on the Matsuura River at the sites of [...] Read more.

Large-scale disasters, such as hurricanes, cyclones, tsunamis, and forest fires, have caused considerable damage in recent years. This study investigated two case studies of discontinuous open levees (kasumi-tei), which are a traditional Japanese river technology, on the Matsuura River at the sites of Okawano and Azame-no-se, and evaluated the advantages of these levees from the perspective of ecosystem-based disaster risk reduction (Eco-DRR). These case studies were conducted through literature surveys, flood observations, and oral interviews. The systems in both the cases were flood control systems utilizing ecosystem services. The traditional river technology (the flood plain open levee) served as an effective Eco-DRR in both cases. Additionally, the flood plain levee technology enhanced the ecosystem services at both sites, including not only flood control capabilities, but also other ecosystem services. Furthermore, the open levees offered substantial cost advantages over their alternatives. These results suggest that other traditional Japanese river technologies may also be effective in strengthening Eco-DRR. Full article

(This article belongs to the Special Issue Flood Risk Management and Resilience)

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13 pages, 2030 KiB

Open AccessFeature PaperEditor’s ChoiceReview

An Overview of Flood Risk Analysis Methods

by Daniel Constantin Diaconu, Romulus Costache and Mihnea Cristian Popa

Water 2021, 13(4), 474; https://doi.org/10.3390/w13040474 - 11 Feb 2021

Cited by 34 | Viewed by 11422

Abstract

Scientific papers present a wide range of methods of flood analysis and forecasting. Floods are a phenomenon with significant socio-economic implications, for which many researchers try to identify the most appropriate methodologies to analyze their temporal and spatial development. This research aims to [...] Read more.

Scientific papers present a wide range of methods of flood analysis and forecasting. Floods are a phenomenon with significant socio-economic implications, for which many researchers try to identify the most appropriate methodologies to analyze their temporal and spatial development. This research aims to create an overview of flood analysis and forecasting methods. The study is based on the need to select and group papers into well-defined methodological categories. The article provides an overview of recent developments in the analysis of flood methodologies and shows current research directions based on this overview. The study was performed taking into account the information included in the Web of Science Core Collection, which brought together 1326 articles. The research concludes with a discussion on the relevance, ease of application, and usefulness of the methodologies. Full article

(This article belongs to the Special Issue Flash-Flood Susceptibility, Forecast and Warning)

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28 pages, 379 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Theoretical and Empirical Characterization of Water as a Factor: Examples and Related Issues with the World Trade Model

by Ignacio Cazcarro and Albert E. Steenge

Water 2021, 13(4), 459; https://doi.org/10.3390/w13040459 - 10 Feb 2021

Cited by 4 | Viewed by 9664

Abstract

This article originates from the theoretical and empirical characterization of factors in the World Trade Model (WTM). It first illustrates the usefulness of this type of model for water research to address policy questions related to virtual water trade, water constraints and water [...] Read more.

This article originates from the theoretical and empirical characterization of factors in the World Trade Model (WTM). It first illustrates the usefulness of this type of model for water research to address policy questions related to virtual water trade, water constraints and water scarcity. It also illustrates the importance of certain key decisions regarding the heterogeneity of water and its relation to the technologies being employed and the prices obtained. With regard to WTM, the global economic input–output model in which multiple technologies can produce a “homogeneous output”, it was recently shown that two different mechanisms should be distinguished by which multiple technologies can arise, i.e., from “technology-specific” or from “shared” factors, which implies a mechanism-specific set of prices, quantities and rents. We discuss and extend these characterizations, notably in relation to the real-world characterization of water as a factor (for which we use the terms technology specific, fully shared and “mixed”). We propose that the presence of these separate mechanisms results in the models being sensitive to relatively small variations in specific numerical values. To address this sensitivity, we suggest a specific role for specific (sub)models or key choices to counter unrealistic model outcomes. To support our proposal we present a selection of simulations for aggregated world regions, and show how key results concerning quantities, prices and rents can be subject to considerable change depending on the precise definitions of resource endowments and the technology-specificity of the factors. For instance, depending on the adopted water heterogeneity level, outcomes can vary from relatively low-cost solutions to higher cost ones and can even reach infeasibility. In the main model discussed here (WTM) factor prices are exogenous, which also contributes to the overall numerical sensitivity of the model. All this affects to a large extent our interpretation of the water challenges, which preferably need to be assessed in integrated frameworks, to account for the main socioeconomic variables, technologies and resources. Full article

(This article belongs to the Special Issue Virtual Water Trade and Water Resources Economics)

28 pages, 9690 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Methodology for Determining the Maximum Potentially Recoverable Energy in Water Distribution Networks

by Elkin Duván Cubides-Castro, Carlos S. López-Aburto, Pedro L. Iglesias-Rey, F. Javier Martínez-Solano, Daniel Mora-Meliá and Marta Iglesias-Castelló

Water 2021, 13(4), 464; https://doi.org/10.3390/w13040464 - 10 Feb 2021

Cited by 7 | Viewed by 3266

Abstract

The excess pressure available in water distribution networks (WDNs) is a relevant aspect in the management and appropriate handling of water resources. If a WDN meets the minimum performance criteria (minimum pressure and maximum flow), excess pressure can occur throughout the day, which [...] Read more.

The excess pressure available in water distribution networks (WDNs) is a relevant aspect in the management and appropriate handling of water resources. If a WDN meets the minimum performance criteria (minimum pressure and maximum flow), excess pressure can occur throughout the day, which is usually lost. These excesses could be considered as potentially recoverable energy (PRE). One way of taking advantage of this energy is to find the nodes on the network where this excess pressure is evident and try to analyze the possible amount of PRE. This work presents a methodology to determine the maximum PRE in a WDN. This methodology includes the locations of the points where the installation of recovery devices leads to this maximum PRE. The method is based on reducing pressures but maintaining circulating points through the lines. Additionally, a new energy balance that allows visualizing and breaking down in more detail all the energy found in a WDN is proposed. The analysis is carried out in an extended period considering different feeding points either by gravity or pumping. Finally, a network resilience index called the Potentially Recoverable Energy Index (PREI) in WDNs is proposed, with which it is possible to diagnose and determine how much energy could be recovered from the network. Study cases presented demonstrate the effectiveness of the methodology and will allow the development of optimizations in the operation of WDNs in favor of the good management of water and energy resources. Full article

(This article belongs to the Special Issue Urban Hydraulic Engineering Simulation and Calculation)

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17 pages, 1845 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Deriving Natural Background Levels of Arsenic at the Meso-Scale Using Site-Specific Datasets: An Unorthodox Method

by Maria Filippini, Chiara Zanotti, Tullia Bonomi, Vito G. Sacchetti, Alessandro Amorosi, Enrico Dinelli and Marco Rotiroti

Water 2021, 13(4), 452; https://doi.org/10.3390/w13040452 - 9 Feb 2021

Cited by 7 | Viewed by 3373

Abstract

Arsenic is found in groundwater above regulatory limits in many countries and its origin is often from natural sources, making the definition of Natural Background Levels (NBLs) crucial. NBL is commonly assessed based on either dedicated small-scale monitoring campaigns or large-scale national/regional groundwater [...] Read more.

Arsenic is found in groundwater above regulatory limits in many countries and its origin is often from natural sources, making the definition of Natural Background Levels (NBLs) crucial. NBL is commonly assessed based on either dedicated small-scale monitoring campaigns or large-scale national/regional groundwater monitoring networks that may not grab local-scale heterogeneities. An alternative method is represented by site-specific monitoring networks in contaminated/polluted sites under remediation. As a main drawback, groundwater quality at these sites is affected by human activities. This paper explores the potential for groundwater data from an assemblage of site-specific datasets of contaminated/polluted sites to define NBLs of arsenic (As) at the meso-scale (order of 1000 km²). Common procedures for the assessment of human influence cannot be applied to this type of dataset due to limited data homogeneity. Thus, an “unorthodox” method is applied involving the definition of a consistent working dataset followed by a statistical identification and critical analysis of the outliers. The study was conducted in a highly anthropized area (Ferrara, N Italy), where As concentrations often exceed national threshold limits in a shallow aquifer. The results show that site-specific datasets, if properly pre-treated, are an effective alternative for the derivation of NBLs when regional monitoring networks fail to catch local-scale variability. Full article

(This article belongs to the Special Issue Natural Background Levels in Groundwater)

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6 pages, 1562 KiB

Open AccessEditor’s ChoiceCommunication

Exposure to SARS-CoV-2 in Aerosolized Wastewater: Toilet Flushing, Wastewater Treatment, and Sprinkler Irrigation

by Muhammad Usman, Muhammad Farooq, Muhammad Farooq and Ioannis Anastopoulos

Water 2021, 13(4), 436; https://doi.org/10.3390/w13040436 - 8 Feb 2021

Cited by 24 | Viewed by 5157

Abstract

The existence of SARS-CoV-2, the etiologic agent of coronavirus disease 2019 (COVID-19), in wastewater raises the opportunity of tracking wastewater for epidemiological monitoring of this disease. However, the existence of this virus in wastewater has raised health concerns regarding the fecal–oral transmission of [...] Read more.

The existence of SARS-CoV-2, the etiologic agent of coronavirus disease 2019 (COVID-19), in wastewater raises the opportunity of tracking wastewater for epidemiological monitoring of this disease. However, the existence of this virus in wastewater has raised health concerns regarding the fecal–oral transmission of COVID-19. This short review is intended to highlight the potential implications of aerosolized wastewater in transmitting this virus. As aerosolized SARS-CoV-2 could offer a more direct respiratory pathway for human exposure, the transmission of this virus remains a significant possibility in the prominent wastewater-associated bioaerosols formed during toilet flushing, wastewater treatment, and sprinkler irrigation. Implementing wastewater disinfection, exercising precautions, and raising public awareness would be essential. Additional research is needed to evaluate the survival, fate, and dissemination of SARS-CoV-2 in wastewater and the environment and rapid characterization of aerosols and their risk assessment. Full article

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

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20 pages, 7157 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Formation Patterns of Mediterranean High-Mountain Water-Bodies in Sierra-Nevada, SE Spain

by Jose Luis Diaz-Hernandez and Antonio Jose Herrera-Martinez

Water 2021, 13(4), 438; https://doi.org/10.3390/w13040438 - 8 Feb 2021

Cited by 4 | Viewed by 3625

Abstract

At present, there is a lack of detailed understanding on how the factors converging on water variables from mountain areas modify the quantity and quality of their watercourses, which are features determining these areas’ hydrological contribution to downstream regions. In order to remedy [...] Read more.

At present, there is a lack of detailed understanding on how the factors converging on water variables from mountain areas modify the quantity and quality of their watercourses, which are features determining these areas’ hydrological contribution to downstream regions. In order to remedy this situation to some extent, we studied the water-bodies of the western sector of the Sierra Nevada massif (Spain). Since thaw is a necessary but not sufficient contributor to the formation of these fragile water-bodies, we carried out field visits to identify their number, size and spatial distribution as well as their different modelling processes. The best-defined water-bodies were the result of glacial processes, such as overdeepening and moraine dams. These water-bodies are the highest in the massif (2918 m mean altitude), the largest and the deepest, making up 72% of the total. Another group is formed by hillside instability phenomena, which are very dynamic and are related to a variety of processes. The resulting water-bodies are irregular and located at lower altitudes (2842 m mean altitude), representing 25% of the total. The third group is the smallest (3%), with one subgroup formed by anthropic causes and another formed from unknown origin. It has recently been found that the Mediterranean and Atlantic watersheds of this massif are somewhat paradoxical in behaviour, since, despite its higher xericity, the Mediterranean watershed generally has higher water contents than the Atlantic. The overall cause of these discrepancies between watersheds is not connected to their formation processes. However, we found that the classification of water volumes by the manners of formation of their water-bodies is not coherent with the associated green fringes because of the anomalous behaviour of the water-bodies formed by moraine dams. This discrepancy is largely due to the passive role of the water retained in this type of water-body as it depends on the characteristics of its hollows. The water-bodies of Sierra Nevada close to the peak line (2918 m mean altitude) are therefore highly dependent on the glacial processes that created the hollows in which they are located. Slope instability created water-bodies mainly located at lower altitudes (2842 m mean altitude), representing tectonic weak zones or accumulation of debris, which are influenced by intense slope dynamics. These water-bodies are therefore more fragile, and their existence is probably more short-lived than that of bodies created under glacial conditions. Full article

(This article belongs to the Special Issue Hydrology, Geomorphology, and Ecology of Intermittent Rivers and Streams)

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24 pages, 7078 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Assessment of the Impact of Small Hydropower Plants on the Ecological Status Indicators of Water Bodies: A Case Study in Lithuania

by Laima Česonienė, Midona Dapkienė and Petras Punys

Water 2021, 13(4), 433; https://doi.org/10.3390/w13040433 - 7 Feb 2021

Cited by 27 | Viewed by 9909

Abstract

Hydropower plants produce renewable and sustainable energy but affect the river’s physico-chemical characteristics and change the abundance and composition of the aquatic organisms. The impact of large HPPs on the ecological conditions of surface water bodies have been extensively studied, but less attention [...] Read more.

Hydropower plants produce renewable and sustainable energy but affect the river’s physico-chemical characteristics and change the abundance and composition of the aquatic organisms. The impact of large HPPs on the ecological conditions of surface water bodies have been extensively studied, but less attention has been paid to environmental impact studies of small hydropower plants (SHPs). The impact of hydropeaking on both the river flow regime and ecosystems has been well-studied for peaking mode plants, mainly medium to large-sized ones. However, for small hydroelectric power plants, and especially for those in lowland rivers, the available information on water quality, benthic macroinvertebrates communities and fish abundance, and biomass is not sufficient. Ten small hydropower plants were selected, and the ecological status of water bodies was assessed in different parts of Lithuania. The studies were performed at the riverbed upstream from the SHPs, where the hydrological regime has not changed, and downstream from the SHPs. It was found that the small hydropower plants do not affect the physico-chemical values of the water quality indicators. This study demonstrated that the total number of benthic macroinvertebrates taxa (TS) is influenced by the concentration of nitrogen and suspended solids, the water flow, the river area, and the current speed; the number of EPT (Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies)) taxa is influenced by the concentration of nitrogen and suspended solids. The studied indicators do not have a significant impact on biomass. The SHPs affect the fish abundance and biomass. The Lithuanian fish index (LFI) is influenced by the average depth and area of the river. Some SHPs operating in lowland areas may yield somewhat significant hydrograph ramping but more detailed investigation is needed to support the significance of this impact on the biological indices. Full article

(This article belongs to the Section Hydrology)

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20 pages, 6639 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Power Take-Off Modelling on the Far-Field Effects of Wave Energy Converter Farms

by Gael Verao Fernandez, Vasiliki Stratigaki, Nicolas Quartier and Peter Troch

Water 2021, 13(4), 429; https://doi.org/10.3390/w13040429 - 6 Feb 2021

Cited by 6 | Viewed by 3102

Abstract

The study of the potential impact of wave energy converter (WEC) farms on the surrounding wave field at long distances from the WEC farm location (also know as “far field” effects) has been a topic of great interest in the past decade. Typically, [...] Read more.

The study of the potential impact of wave energy converter (WEC) farms on the surrounding wave field at long distances from the WEC farm location (also know as “far field” effects) has been a topic of great interest in the past decade. Typically, “far-field” effects have been studied using phase average or phase resolving numerical models using a parametrization of the WEC power absorption using wave transmission coefficients. Most recent studies have focused on using coupled models between a wave-structure interaction solver and a wave-propagation model, which offer a more complex and accurate representation of the WEC hydrodynamics and PTO behaviour. The difference in the results between the two aforementioned approaches has not been studied yet, nor how different ways of modelling the PTO system can affect wave propagation in the lee of the WEC farm. The Coastal Engineering Research Group of Ghent University has developed both a parameterized model using the sponge layer technique in the mild slope wave propagation model MILDwave and a coupled model MILDwave-NEMOH (NEMOH is a boundary element method-based wave-structure interaction solver), for studying the “far-field” effects of WEC farms. The objective of the present study is to perform a comparison between both numerical approaches in terms of performance for obtaining the “far-field” effects of two WEC farms. Results are given for a series of regular wave conditions, demonstrating a better accuracy of the MILDwave-NEMOH coupled model in obtaining the wave disturbance coefficient (

K_{d}

) values around the considered WEC farms. Subsequently, the analysis is extended to study the influence of the PTO system modelling technique on the “far-field” effects by considering: (i) a linear optimal, (ii) a linear sub-optimal and (iii) a non-linear hydraulic PTO system. It is shown that modelling a linear optimal PTO system can lead to an unrealistic overestimation of the WEC motions than can heavily affect the wave height at a large distance in the lee of the WEC farm. On the contrary, modelling of a sub-optimal PTO system and of a hydraulic PTO system leads to a similar, yet reduced impact on the “far-field” effects on wave height. The comparison of the PTO systems’ modelling technique shows that when using coupled models, it is necessary to carefully model the WEC hydrodynamics and PTO behaviour as they can introduce substantial inaccuracies into the WECs’ motions and the WEC farm “far-field” effects. Full article

(This article belongs to the Special Issue Numerical and Experimental Modelling of Wave Field Variations around Arrays of Wave Energy Converters)

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19 pages, 5355 KiB

Open AccessEditor’s ChoiceArticle

Regional-Scale Model Analysis of Climate Changes Impact on the Water Budget of the Critical Zone and Groundwater Recharge in the European Part of Russia

by Sergey O. Grinevskiy, Sergey P. Pozdniakov and Ekaterina A. Dedulina

Water 2021, 13(4), 428; https://doi.org/10.3390/w13040428 - 6 Feb 2021

Cited by 10 | Viewed by 2910

Abstract

Groundwater recharge by precipitation is the main source of groundwater resources, which are widely used in the European part of Russia (ER). The main goal of the presented studies is to analyze the effect of observed climate changes on the processes of groundwater [...] Read more.

Groundwater recharge by precipitation is the main source of groundwater resources, which are widely used in the European part of Russia (ER). The main goal of the presented studies is to analyze the effect of observed climate changes on the processes of groundwater recharge. For this purpose analysis of long-term meteorological data as well as water budget and groundwater recharge simulation were used. First, meteorological data of 22 weather stations, located from south (Lat 46°) to north (Lat 66°) of ER for historical (1965–1988) and modern (1989–2018) periods were compared to investigate the observed latitudinal changes in annual and seasonal averages of precipitation, wind speed, air temperature, and humidity. Second, water budget in critical zone was simulated, using codes SURFBAL and HYDRUS-1D. SURFBAL generates upper boundary conditions for unsaturated flow modelling with HYDRUS-1D, taking into account snow accumulation and melting as well as topsoil freezing, which are important processes that affect runoff generation and the infiltration of meltwater. Water budget and groundwater recharge simulations based on long-term meteorological data and soil and vegetation parameters, typical for the investigated region. The simulation results for the historical and modern periods were compared to find out the impact of climate change on the average annual and seasonal averages of surface runoff, evapotranspiration, and groundwater recharge, as well as to assess latitudinal differences in water budget changes. The results of the simulation showed, that despite a significant increase in air temperature, groundwater recharge in the southern regions did not change, but even increased up to 50–60 mm/year in the central and northern regions of ER. There are two main reasons for this. First, the observed increase in air temperature is compensated by a decrease in wind speed, so there was no significant increase in evapotranspiration in the modern period. Also, the observed increase in air temperature and precipitation in winter is the main reason for the increase in groundwater recharge, since these climate changes lead to an increase in water infiltration into the soil in the cold period, when there is no evapotranspiration. Full article

(This article belongs to the Section Hydrology)

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21 pages, 4088 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effects of Wave-Induced Processes in a Coupled Wave–Ocean Model on Particle Transport Simulations

by Joanna Staneva, Marcel Ricker, Ruben Carrasco Alvarez, Øyvind Breivik and Corinna Schrum

Water 2021, 13(4), 415; https://doi.org/10.3390/w13040415 - 5 Feb 2021

Cited by 23 | Viewed by 4059

Abstract

This study investigates the effects of wind–wave processes in a coupled wave–ocean circulation model on Lagrangian transport simulations. Drifters deployed in the southern North Sea from May to June 2015 are used. The Eulerian currents are obtained by simulation from the coupled circulation [...] Read more.

This study investigates the effects of wind–wave processes in a coupled wave–ocean circulation model on Lagrangian transport simulations. Drifters deployed in the southern North Sea from May to June 2015 are used. The Eulerian currents are obtained by simulation from the coupled circulation model (NEMO) and the wave model (WAM), as well as a stand-alone NEMO circulation model. The wave–current interaction processes are the momentum and energy sea state dependent fluxes, wave-induced mixing and Stokes–Coriolis forcing. The Lagrangian transport model sensitivity to these wave-induced processes in NEMO is quantified using a particle drift model. Wind waves act as a reservoir for energy and momentum. In the coupled wave–ocean circulation model, the momentum that is transferred into the ocean model is considered as a fraction of the total flux that goes directly to the currents plus the momentum lost from wave dissipation. Additional sensitivity studies are performed to assess the potential contribution of windage on the Lagrangian model performance. Wave-induced drift is found to significantly affect the particle transport in the upper ocean. The skill of particle transport simulations depends on wave–ocean circulation interaction processes. The model simulations were assessed using drifter and high-frequency (HF) radar observations. The analysis of the model reveals that Eulerian currents produced by introducing wave-induced parameterization into the ocean model are essential for improving particle transport simulations. The results show that coupled wave–circulation models may improve transport simulations of marine litter, oil spills, larval drift or transport of biological materials. Full article

(This article belongs to the Special Issue Tracer and Timescale Methods for Passive and Reactive Transport in Fluid Flows)

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16 pages, 4256 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Hydrogeological and Geochemical Characteristics of the Coastal Aquifer of Stromboli Volcanic Island (Italy)

by Paolo Madonia, Gloria Campilongo, Marianna Cangemi, Maria Luisa Carapezza, Salvatore Inguaggiato, Massimo Ranaldi and Fabio Vita

Water 2021, 13(4), 417; https://doi.org/10.3390/w13040417 - 5 Feb 2021

Cited by 5 | Viewed by 3299

Abstract

Although groundwater is a strategic source in volcanic islands, most hydrogeochemical research on this topic has been focused on volcanic activity monitoring, overlooking general hydrogeological aspects. The same applies to one of the most studied volcanoes in the world, Stromboli Island (Italy). Here, [...] Read more.

Although groundwater is a strategic source in volcanic islands, most hydrogeochemical research on this topic has been focused on volcanic activity monitoring, overlooking general hydrogeological aspects. The same applies to one of the most studied volcanoes in the world, Stromboli Island (Italy). Here, we provide a hydrogeological scheme of its coastal aquifer, retrieving inferences about its potential use as a water supply source and for optimizing monitoring protocols for volcanic surveillance. Starting from the hydrogeochemical literature background, we analyzed new data, acquired both for volcano monitoring purposes and during specific surveys. Among these, there were saturated hydraulic conductivity measurements of selected rock samples and precise determinations of water table elevations based on GNSS surveys of wells. We identified a ubiquitous thin lens of brackish water floating on seawater and composed of a variable mixing of marine and meteoric components; inlets of hydrothermal fluids to the aquifer are basically gases, mainly CO₂. Based on its hydrogeochemical character, the coastal aquifer of Stromboli could be used as a water supply source after desalinization by reverse osmosis, while the wells located far from the seashore are the most interesting for volcano monitoring, because they are less disturbed by the shallow geochemical noise. Full article

(This article belongs to the Special Issue Geochemistry of Groundwater)

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15 pages, 6029 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impact of the Depth of Diaphragm Wall on the Groundwater Drawdown during Foundation Dewatering Considering Anisotropic Permeability of Aquifer

by Xu-wei Wang and Ye-shuang Xu

Water 2021, 13(4), 418; https://doi.org/10.3390/w13040418 - 5 Feb 2021

Cited by 22 | Viewed by 3867

Abstract

Foundation dewatering combined with a waterproof curtain is widely applied to ensure the safety of the foundation pit in areas with multi-aquifer–aquitard alternative strata. The buried depth of the diaphragm wall can influence the environmental effect due to dewatering obviously. This paper investigates [...] Read more.

Foundation dewatering combined with a waterproof curtain is widely applied to ensure the safety of the foundation pit in areas with multi-aquifer–aquitard alternative strata. The buried depth of the diaphragm wall can influence the environmental effect due to dewatering obviously. This paper investigates the impact of the buried depth of the diaphragm wall on the groundwater drawdown considering the anisotropic permeability of the dewatering aquifer. Numerical simulation is conducted based on an engineering case. The ratio of penetrating depth of diaphragm wall to thickness of dewatering aquifer (R_W) and the ratio of horizontal and vertical hydraulic conductivity of dewatering aquifer (R_C) are varied. The relationship between approximate hydraulic gradient (Δi) and R_W (or R_C) can be fitted by Boltzmann curve (or logarithmic curve). Effective, suggested and control values of R_W (or R_C) are proposed, of which the suggested value is recommended in practical engineering. The effective, suggested and control value of R_W can be calculated by logarithmical equation considering the value of R_C. Full article

(This article belongs to the Section Hydrology)

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17 pages, 2500 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Campus Study of the Impact of Ultra-Low Flush Toilets on Sewerage Networks and Water Usage

by Peter Melville-Shreeve, Sarah Cotterill, Alex Newman and David Butler

Water 2021, 13(4), 419; https://doi.org/10.3390/w13040419 - 5 Feb 2021

Cited by 5 | Viewed by 5028

Abstract

Water demand management often focuses on quantifying the benefits of water efficiency rather than the potential impact of reduced flows on the sewer network. This study assessed the impact of a high-density deployment of ultra-low flush toilets (ULFT). A pre-installation washroom survey was [...] Read more.

Water demand management often focuses on quantifying the benefits of water efficiency rather than the potential impact of reduced flows on the sewer network. This study assessed the impact of a high-density deployment of ultra-low flush toilets (ULFT). A pre-installation washroom survey was carried out in July 2018. Water demand and sewer network condition were assessed ahead of the installation of 119 ULFTs and a real-time monitoring system across seven buildings on the University of Exeter campus. ULFTs were flushed 257,925 times in 177 days saving an estimated 2287 m³ per annum (compared to traditional 6 litre WCs). The annual cost saving of this reduction is approximately £12,580/annum, assuming a volumetric cost of £5.50/m³ of water. Mean discharge to the sewer network reduced by 6 m³/day. In the six-month period, 95 maintenance issues were reported, equating to 1 in 2700 flushes (0.037%). However, the frequency of incidents decreased after an initial commissioning period. There is no evidence, from blockage reports or photographs of manhole flow conditions, that the risk of blockage in the sewer network increased as a result of the ULFT installation programme. Full article

(This article belongs to the Special Issue Water Demand Management)

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15 pages, 4396 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on the Optimal Strategy for Power Regulation of Governing System of Hydropower Station

by Cong Wang, De-Kuan Wang and Jian-Ming Zhang

Water 2021, 13(4), 421; https://doi.org/10.3390/w13040421 - 5 Feb 2021

Cited by 5 | Viewed by 2919

Abstract

Active power instability during the power regulation process is a problem that affects the operation security of hydropower stations and the power grid. This paper focuses on the dynamic response to power regulation of a hydro-turbine governor in the power control mode. Firstly, [...] Read more.

Active power instability during the power regulation process is a problem that affects the operation security of hydropower stations and the power grid. This paper focuses on the dynamic response to power regulation of a hydro-turbine governor in the power control mode. Firstly, the mathematical model for the hydro-turbine governing system connected to the power grid is established. Then, considering the effect of water hammer and the guide vane operating speed on power oscillation and reverse power regulation, a novel control strategy based on the S-curve acceleration and deceleration control algorithm (S-curve control algorithm) is proposed to improve power regulation. Furthermore, we carried out field tests in a real hydropower station in order to compare the regulation quality of the novel control strategy based on the S-curve control algorithm with the traditional linear control strategy. Finally, the obtained results show that the proposed optimal control strategy for the hydro-turbine governor improves the stability of power regulation by effectively suppressing reverse power regulation and overshoot. This study provides a good solution for the instability of power and reverse power regulation during the regulation process of the hydro-turbine governor in the power control mode. Full article

(This article belongs to the Special Issue Hydraulic Transient of Hydropower Station and Pump Station)

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23 pages, 5363 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Watershed Delineation and Climate Datasets Density on Runoff Predictions for the Upper Mississippi River Basin Using SWAT within HAWQS

by Manyu Chen, Yuanlai Cui, Philip W. Gassman and Raghavan Srinivasan

Water 2021, 13(4), 422; https://doi.org/10.3390/w13040422 - 5 Feb 2021

Cited by 11 | Viewed by 4498

Abstract

The quality of input data and the process of watershed delineation can affect the accuracy of runoff predictions in watershed modeling. The Upper Mississippi River Basin was selected to evaluate the effects of subbasin and/or hydrologic response unit (HRU) delineations and the density [...] Read more.

The quality of input data and the process of watershed delineation can affect the accuracy of runoff predictions in watershed modeling. The Upper Mississippi River Basin was selected to evaluate the effects of subbasin and/or hydrologic response unit (HRU) delineations and the density of climate dataset on the simulated streamflow and water balance components using the Hydrologic and Water Quality System (HAWQS) platform. Five scenarios were examined with the same parameter set, including 8- and 12-digit hydrologic unit codes, two levels of HRU thresholds and two climate data densities. Results showed that statistic evaluations of monthly streamflow from 1983 to 2005 were satisfactory at some gauge sites but were relatively worse at others when shifting from 8-digit to 12-digit subbasins, revealing that the hydrologic response to delineation schemes can vary across a large basin. Average channel slope and drainage density increased significantly from 8-digit to 12-digit subbasins. This resulted in higher lateral flow and groundwater flow estimates, especially for the lateral flow. Moreover, a finer HRU delineation tends to generate more runoff because it captures a refined level of watershed spatial variability. The analysis of climate datasets revealed that denser climate data produced higher predicted runoff, especially for summer months. Full article

(This article belongs to the Section Hydrology)

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12 pages, 5155 KiB

Open AccessEditor’s ChoiceArticle

Spatial Characteristics of Groundwater Chemistry in Unzen, Nagasaki, Japan

by Kei Nakagawa, Hiroki Amano and Ronny Berndtsson

Water 2021, 13(4), 426; https://doi.org/10.3390/w13040426 - 5 Feb 2021

Cited by 15 | Viewed by 4156

Abstract

Nitrate pollution in groundwater is a serious problem in Shimabara Peninsula, Nagasaki, Japan. A better understanding of the hydrogeochemical evolution of groundwater in vulnerable aquifers is important for health and environment. In this study, groundwater samples were collected at 12 residential and 57 [...] Read more.

Nitrate pollution in groundwater is a serious problem in Shimabara Peninsula, Nagasaki, Japan. A better understanding of the hydrogeochemical evolution of groundwater in vulnerable aquifers is important for health and environment. In this study, groundwater samples were collected at 12 residential and 57 municipal water supply wells and springs in July and August 2018. Nitrate (NO₃−N) concentration at eight sampling sites (12%) exceeded Japanese drinking water standard for NO₃ + NO₂−N (10 mg L⁻¹). The highest nitrate concentration was 19.9 mg L⁻¹. Polluted groundwater is distributed in northeastern, northwestern, and southwestern areas, where land is used for intensive agriculture. Correlation analysis suggests that nitrate sources are agricultural fertilizers and livestock waste. Dominant groundwater chemistry is (Ca+Mg)−HCO₃ or (Ca+Mg)−(SO₄+NO₃) type. Groundwater with higher nitrate concentration is of (Ca+Mg)−(SO₄+NO₃) type, indicating nitrate pollution affecting water chemistry. Principal component analysis extracted two important factors controlling water chemistry. The first principal component explained dissolved ions through water–rock interaction and agricultural activities. The second principal component explained cation exchange and dominant agricultural effects from fertilizers. Hierarchical cluster analysis classified groundwater into four groups. One of these is related to the dissolution of major ions. The other three represent nitrate pollution. Full article

(This article belongs to the Section Hydrology)

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22 pages, 14731 KiB

Open AccessEditor’s ChoiceArticle

Clustering Simultaneous Occurrences of the Extreme Floods in the Neckar Catchment

by Ehsan Modiri and András Bárdossy

Water 2021, 13(4), 399; https://doi.org/10.3390/w13040399 - 4 Feb 2021

Cited by 2 | Viewed by 4362

Abstract

Flood protection is crucial for making socioeconomic policies due to the high losses of extreme floods. So far, the synchronous occurrences of flood events have not been deeply investigated. In this paper, multivariate analysis was implemented to reveal the interconnection between these floods [...] Read more.

Flood protection is crucial for making socioeconomic policies due to the high losses of extreme floods. So far, the synchronous occurrences of flood events have not been deeply investigated. In this paper, multivariate analysis was implemented to reveal the interconnection between these floods in spatiotemporal resolution. The discharge measurements of 46 gauges with a continuous daily time series for 55 years were taken over the Neckar catchment. Initially, the simultaneous floods were identified. The Kendall correlation between the pair sets of peaks was determined to scrutinize the similarities between the simultaneous events. Agglomerative hierarchical clustering tree (AHCT) and multidimensional scaling (MDS) were employed, and obtained clusters were compared and evaluated with the Silhouette verification method. AHCT shows that the Average and Ward algorithms are appropriate to detect reasonable clusters. The Neckar catchment has been divided into three major clusters: the first cluster mainly covers the western part and is bounded by the Black Forest and Swabian Alps. The second cluster is mostly located in the eastern part of the upper Neckar. The third cluster contains the remaining lowland areas of the Neckar basin. The results illustrate that the clusters act relatively as a function of topography, geology, and anthropogenic alterations of the catchment. Full article

(This article belongs to the Special Issue Stochastic Modelling of Hydrometeorological Processes for Engineering Applications)

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19 pages, 20428 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

An Operational High-Performance Forecasting System for City-Scale Pluvial Flash Floods in the Southwestern Plain Areas of Taiwan

by Tzu-Yin Chang, Hongey Chen, Huei-Shuin Fu, Wei-Bo Chen, Yi-Chiang Yu, Wen-Ray Su and Lee-Yaw Lin

Water 2021, 13(4), 405; https://doi.org/10.3390/w13040405 - 4 Feb 2021

Cited by 18 | Viewed by 4454

Abstract

A pluvial flash flood is rapid flooding induced by intense rainfall associated with a severe weather system, such as thunderstorms or typhoons. Additionally, topography, ground cover, and soil conditions also account for the occurrence of pluvial flash floods. Pluvial flash floods are among [...] Read more.

A pluvial flash flood is rapid flooding induced by intense rainfall associated with a severe weather system, such as thunderstorms or typhoons. Additionally, topography, ground cover, and soil conditions also account for the occurrence of pluvial flash floods. Pluvial flash floods are among the most devastating natural disasters that occur in Taiwan, and these floods always /occur within a few minutes or hours of excessive rainfall. Pluvial flash floods usually threaten large plain areas with high population densities; therefore, there is a great need to implement an operational high-performance forecasting system for pluvial flash flood mitigation and evacuation decisions. This study developed a high-performance two-dimensional hydrodynamic model based on the finite-element method and unstructured grids. The operational high-performance forecasting system is composed of the Weather Research and Forecasting (WRF) model, the Storm Water Management Model (SWMM), a two-dimensional hydrodynamic model, and a map-oriented visualization tool. The forecasting system employs digital elevation data with a 1-m resolution to simulate city-scale pluvial flash floods. The extent of flooding during historical inundation events derived from the forecasting system agrees well with the surveyed data for plain areas in southwestern Taiwan. The entire process of the operational high-performance forecasting system prediction of pluvial flash floods in the subsequent 24 h is accomplished within 8–10 min, and forecasts are updated every six hours. Full article

(This article belongs to the Special Issue Mitigation Techniques for Water-Induced Natural Disasters: The State of the Art)

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28 pages, 776 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Seagrass Holobiont: What We Know and What We Still Need to Disclose for Its Possible Use as an Ecological Indicator

by Chiara Conte, Alice Rotini, Loredana Manfra, Marco Maria D’Andrea, Gidon Winters and Luciana Migliore

Water 2021, 13(4), 406; https://doi.org/10.3390/w13040406 - 4 Feb 2021

Cited by 37 | Viewed by 8124

Abstract

Microbes and seagrass establish symbiotic relationships constituting a functional unit called the holobiont that reacts as a whole to environmental changes. Recent studies have shown that the seagrass microbial associated community varies according to host species, environmental conditions and the host’s health status, [...] Read more.

Microbes and seagrass establish symbiotic relationships constituting a functional unit called the holobiont that reacts as a whole to environmental changes. Recent studies have shown that the seagrass microbial associated community varies according to host species, environmental conditions and the host’s health status, suggesting that the microbial communities respond rapidly to environmental disturbances and changes. These changes, dynamics of which are still far from being clear, could represent a sensitive monitoring tool and ecological indicator to detect early stages of seagrass stress. In this review, the state of art on seagrass holobiont is discussed in this perspective, with the aim of disentangling the influence of different factors in shaping it. As an example, we expand on the widely studied Halophila stipulacea’s associated microbial community, highlighting the changing and the constant components of the associated microbes, in different environmental conditions. These studies represent a pivotal contribution to understanding the holobiont’s dynamics and variability pattern, and to the potential development of ecological/ecotoxicological indices. The influences of the host’s physiological and environmental status in changing the seagrass holobiont, alongside the bioinformatic tools for data analysis, are key topics that need to be deepened, in order to use the seagrass-microbial interactions as a source of ecological information. Full article

(This article belongs to the Special Issue Aquatic Ecotoxicity Assessment)

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11 pages, 1548 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Role of Biochar in Improving Sandy Soil Water Retention and Resilience to Drought

by Ling Li, Yong-Jiang Zhang, Abigayl Novak, Yingchao Yang and Jinwu Wang

Water 2021, 13(4), 407; https://doi.org/10.3390/w13040407 - 4 Feb 2021

Cited by 89 | Viewed by 14189

Abstract

In recent years, plants in sandy soils have been impacted by increased climate variability due to weak water holding and temperature buffering capacities of the parent material. The projected impact spreads all over the world, including New England, USA. Many regions of the [...] Read more.

In recent years, plants in sandy soils have been impacted by increased climate variability due to weak water holding and temperature buffering capacities of the parent material. The projected impact spreads all over the world, including New England, USA. Many regions of the world may experience an increase in frequency and severity of drought, which can be attributed to an increased variability in precipitation and enhanced water loss due to warming. The overall benefits of biochar in environmental management have been extensively investigated. This review aims to discuss the water holding capacity of biochar from the points of view of fluid mechanics and propose several prioritized future research topics. To understand the impacts of biochar on sandy soils in-depth, sandy soil properties (surface area, pore size, water properties, and characteristics) and how biochar could improve the soil quality as well as plant growth, development, and yield are reviewed. Incorporating biochar into sandy soils could result in a net increase in the surface area, a stronger hydrophobicity at a lower temperature, and an increase in the micropores to maximize gap spaces. The capability of biochar in reducing fertilizer drainage through increasing water retention can improve crop productivity and reduce the nutrient leaching rate in agricultural practices. To advance research in biochar products and address the impacts of increasing climate variability, future research may focus on the role of biochar in enhancing soil water retention, plant water use efficiency, crop resistance to drought, and crop productivity. 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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18 pages, 6363 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Climate Change Adaptations for Food Security in Vulnerable Areas of the Egyptian Nile—For Tackling the Overlooked Nexus Hazards of Hydrological Extremes and Waste Pollutions

by Otto Chen, Ahmed Abdelhalim, Ying Liu, Miguel Rico-Ramirez and Dawei Han

Water 2021, 13(4), 412; https://doi.org/10.3390/w13040412 - 4 Feb 2021

Cited by 4 | Viewed by 4263

Abstract

The Nile Delta has been suffering from complex environmental hazards caused by climate change and human-induced evolvements, which have led to adverse impacts on national food security. An unfavourable nexus between solid waste management issues and extreme hydrological events is examined mainly through [...] Read more.

The Nile Delta has been suffering from complex environmental hazards caused by climate change and human-induced evolvements, which have led to adverse impacts on national food security. An unfavourable nexus between solid waste management issues and extreme hydrological events is examined mainly through extensive field investigation and literature research, which is an emerging issue affecting food safety and security whilst still being overlooked so far. The findings not only reveal the significance of the emerging issue but also support our proposed recommendations in the policy/legislation and technology sphere. This interdisciplinary research employs a holistic lens that covers diverse perspectives, including systemic problems, wastewater treatment, and environmental neuroscience, to explore the relationship between food, climate change, water management, and waste pollution, and to achieve novel discoveries for the practical adaptations of Egypt’s challenges. Full article

(This article belongs to the Section Hydrology)

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18 pages, 2929 KiB

Open AccessEditor’s ChoiceArticle

Satellite Imageries and Field Data of Macrophytes Reveal a Regime Shift of a Tropical Lake (Lake Ziway, Ethiopia)

by Yohannes Tefera Damtew, Boud Verbeiren, Aymere Awoke and Ludwig Triest

Water 2021, 13(4), 396; https://doi.org/10.3390/w13040396 - 3 Feb 2021

Cited by 14 | Viewed by 4491

Abstract

Lake Ziway is one of the largest freshwater lakes located in the central Ethiopian rift valley. The lake shoreline is dominated by macrophytes which play an important role in immobilizing run-off pollution, stabilize sediments and support biodiversity. Monitoring the spatio-temporal changes of great [...] Read more.

Lake Ziway is one of the largest freshwater lakes located in the central Ethiopian rift valley. The lake shoreline is dominated by macrophytes which play an important role in immobilizing run-off pollution, stabilize sediments and support biodiversity. Monitoring the spatio-temporal changes of great lakes requires standardized methods. The aim of this study was to assess the current and long-term trends of macrophyte distribution, surface water area and the water level of Lake Ziway using remote sensing images from 1986 to 2016 with additional hydro-meteorological data. A supervised image classification with classification enhancement using Normalized Difference Aquatic Vegetation Index (NDAVI) and Normalized Difference Vegetation Index (NDVI) was applied. The classification based on NDAVI revealed eight target classes which were identified with an overall producer’s accuracy of 79.6%. Contemporary open water and macrophyte fringes occupied most of the study area with a total area of 407.4 km² and 60.1 km², respectively. The findings also revealed a regime shift in the mean water level of the lake and a decline in macrophyte distribution. The long-term water surface area of Lake Ziway also decreased between 1986 and 2016. The changes in water level could be explained by climate variability in the region and strong anthropogenic disturbance. A decline in water level was also associated with lowered surface water area, lakeward retreated macrophyte fringes and enhanced landward encroachment of mudflats, and resulted in a succession of macrophytes with semi-terrestrial vegetations. Full article

(This article belongs to the Section Hydrology)

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23 pages, 1947 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of the Drag Force on the Average Absorbed Power of Heaving Wave Energy Converters Using Smoothed Particle Hydrodynamics

by Nicolas Quartier, Pablo Ropero-Giralda, José M. Domínguez, Vasiliki Stratigaki and Peter Troch

Water 2021, 13(3), 384; https://doi.org/10.3390/w13030384 - 2 Feb 2021

Cited by 27 | Viewed by 5360

Abstract

In this paper, we investigated how the added mass, the hydrodynamic damping and the drag coefficient of a Wave Energy Converter (WEC) can be calculated using DualSPHysics. DualSPHysics is a software application that applies the Smoothed Particle Hydrodynamics (SPH) method, a Lagrangian meshless [...] Read more.

In this paper, we investigated how the added mass, the hydrodynamic damping and the drag coefficient of a Wave Energy Converter (WEC) can be calculated using DualSPHysics. DualSPHysics is a software application that applies the Smoothed Particle Hydrodynamics (SPH) method, a Lagrangian meshless method used in a growing range of applications within the field of Computational Fluid Dynamics (CFD). Furthermore, the effect of the drag force on the WEC’s motion and average absorbed power is analyzed. Particularly under controlled conditions and in the resonance region, the drag force becomes significant and can greatly reduce the average absorbed power of a heaving point absorber. Once the drag coefficient has been determined, it is used in a modified equation of motion in the frequency domain, taking into account the effect of the drag force. Three different methods were compared for the calculation of the average absorbed power: linear potential flow theory, linear potential flow theory modified to take the drag force into account and DualSPHysics. This comparison showed the considerable effect of the drag force in the resonance region. Calculations of the drag coefficient were carried out for three point absorber WECs: one spherical WEC and two cylindrical WECs. Simulations in regular waves were performed for one cylindrical WEC with two different power take-off (PTO) systems: a linear damping and a Coulomb damping PTO system. The Coulomb damping PTO system was added in the numerical coupling between DualSPHysics and Project Chrono. Furthermore, we considered the optimal PTO system damping coefficient taking the effect of the drag force into account. Full article

(This article belongs to the Special Issue Numerical and Experimental Modelling of Wave Field Variations around Arrays of Wave Energy Converters)

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24 pages, 24572 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Flood Suspended Sediment Transport: Combined Modelling from Dilute to Hyper-Concentrated Flow

by Jaan H. Pu, Joseph T. Wallwork, Md. Amir Khan, Manish Pandey, Hanif Pourshahbaz, Alfrendo Satyanaga, Prashanth R. Hanmaiahgari and Tim Gough

Water 2021, 13(3), 379; https://doi.org/10.3390/w13030379 - 1 Feb 2021

Cited by 36 | Viewed by 5693

Abstract

During flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground conditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the [...] Read more.

During flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground conditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the differences between hyper-concentrated and dilute flows, a linear-power coupled model is proposed to integrate these considerations. A parameterised method combining the sediment size, Rouse number, mean concentration, and flow depth parameters has been used for modelling the sediment profile. The accuracy of the proposed model has been verified against the reported laboratory measurements and comparison with other published analytical methods. The proposed method has been shown to effectively compute the concentration profile for a wide range of suspended sediment conditions from hyper-concentrated to dilute flows. Detailed comparisons reveal that the proposed model calculates the dilute profile with good correspondence to the measured data and other modelling results from literature. For the hyper-concentrated profile, a clear division of lower (bed-load) to upper layer (suspended-load) transport can be observed in the measured data. Using the proposed model, the transitional point from this lower to upper layer transport can be calculated precisely. Full article

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

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23 pages, 75708 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Classification and Prediction of Natural Streamflow Regimes in Arid Regions of the USA

by Angela M. Merritt, Belize Lane and Charles P. Hawkins

Water 2021, 13(3), 380; https://doi.org/10.3390/w13030380 - 1 Feb 2021

Cited by 17 | Viewed by 5184

Abstract

Understanding how natural variation in flow regimes influences stream ecosystem structure and function is critical to the development of effective stream management policies. Spatial variation in flow regimes among streams is reasonably well understood for streams in mesic regions, but a more robust [...] Read more.

Understanding how natural variation in flow regimes influences stream ecosystem structure and function is critical to the development of effective stream management policies. Spatial variation in flow regimes among streams is reasonably well understood for streams in mesic regions, but a more robust characterization of flow regimes in arid regions is needed, especially to support biological monitoring and assessment programs. In this paper, we used long-term (41 years) records of mean daily streamflow from 287 stream reaches in the arid and semi-arid western USA to develop and compare several alternative flow-regime classifications. We also evaluated how accurately we could predict the flow-regime classes of ungauged reaches. Over the 41-year record examined (water years 1972–2013), the gauged reaches varied continuously from always having flow > zero to seldom having flow. We predicted ephemeral and perennial reaches with less error than reaches with an intermediate number of zero-flow days or years. We illustrate application of our approach by predicting the flow-regime classes at ungauged reaches in Arizona, USA. Maps based on these predictions were generally consistent with qualitative expectations of how flow regimes vary spatially across Arizona. These results represent a promising step toward more effective assessment and management of streams in arid regions. Full article

(This article belongs to the Special Issue Hydrology, Geomorphology, and Ecology of Intermittent Rivers and Streams)

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18 pages, 4251 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Rainfall Erosivity Factor Estimation Using Machine and Deep Learning Models

by Jimin Lee, Seoro Lee, Jiyeong Hong, Dongjun Lee, Joo Hyun Bae, Jae E. Yang, Jonggun Kim and Kyoung Jae Lim

Water 2021, 13(3), 382; https://doi.org/10.3390/w13030382 - 1 Feb 2021

Cited by 22 | Viewed by 6930

Abstract

Rainfall erosivity factor (R-factor) is one of the Universal Soil Loss Equation (USLE) input parameters that account for impacts of rainfall intensity in estimating soil loss. Although many studies have calculated the R-factor using various empirical methods or the USLE method, these methods [...] Read more.

Rainfall erosivity factor (R-factor) is one of the Universal Soil Loss Equation (USLE) input parameters that account for impacts of rainfall intensity in estimating soil loss. Although many studies have calculated the R-factor using various empirical methods or the USLE method, these methods are time-consuming and require specialized knowledge for the user. The purpose of this study is to develop machine learning models to predict the R-factor faster and more accurately than the previous methods. For this, this study calculated R-factor using 1-min interval rainfall data for improved accuracy of the target value. First, the monthly R-factors were calculated using the USLE calculation method to identify the characteristics of monthly rainfall-runoff induced erosion. In turn, machine learning models were developed to predict the R-factor using the monthly R-factors calculated at 50 sites in Korea as target values. The machine learning algorithms used for this study were Decision Tree, K-Nearest Neighbors, Multilayer Perceptron, Random Forest, Gradient Boosting, eXtreme Gradient Boost, and Deep Neural Network. As a result of the validation with 20% randomly selected data, the Deep Neural Network (DNN), among seven models, showed the greatest prediction accuracy results. The DNN developed in this study was tested for six sites in Korea to demonstrate trained model performance with Nash–Sutcliffe Efficiency (NSE) and the coefficient of determination (R²) of 0.87. This means that our findings show that DNN can be efficiently used to estimate monthly R-factor at the desired site with much less effort and time with total monthly precipitation, maximum daily precipitation, and maximum hourly precipitation data. It will be used not only to calculate soil erosion risk but also to establish soil conservation plans and identify areas at risk of soil disasters by calculating rainfall erosivity factors. Full article

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

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13 pages, 4276 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

On Neglecting Free-Stream Turbulence in Numerical Simulation of the Wind-Induced Bias of Snow Gauges

by Arianna Cauteruccio, Matteo Colli and Luca G. Lanza

Water 2021, 13(3), 363; https://doi.org/10.3390/w13030363 - 31 Jan 2021

Cited by 4 | Viewed by 2909

Abstract

Numerical studies of the wind-induced bias of precipitation measurements assume that turbulence is generated by the interaction of the airflow with the gauge body, while steady and uniform free-stream conditions are imposed. However, wind is turbulent in nature due to the roughness of [...] Read more.

Numerical studies of the wind-induced bias of precipitation measurements assume that turbulence is generated by the interaction of the airflow with the gauge body, while steady and uniform free-stream conditions are imposed. However, wind is turbulent in nature due to the roughness of the site and the presence of obstacles, therefore precipitation gauges are immersed in a turbulent flow. Further to the turbulence generated by the flow-gauge interaction, we investigated the natural free-stream turbulence and its influence on precipitation measurement biases. Realistic turbulence intensity values at the gauge collector height were derived from 3D sonic anemometer measurements. Large Eddy Simulations of the turbulent flow around a chimney-shaped gauge were performed under uniform and turbulent free-stream conditions, using geometrical obstacles upstream of the gauge to provide the desired turbulence intensity. Catch ratios for dry snow particles were obtained using a Lagrangian particle tracking model, and the collection efficiency was calculated based on a suitable particle size distribution. The collection efficiency in turbulent conditions showed stronger undercatch at the investigated wind velocity and snowfall intensity below 10 mm h⁻¹, demonstrating that adjustment curves based on the simplifying assumption of uniform free-stream conditions do not accurately portray the wind-induced bias of snow measurements. Full article

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

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24 pages, 6512 KiB

Open AccessEditor’s ChoiceArticle

Potential Dam Breach Analysis and Flood Wave Risk Assessment Using HEC-RAS and Remote Sensing Data: A Multicriteria Approach

by Emmanouil Psomiadis, Lefteris Tomanis, Antonis Kavvadias, Konstantinos X. Soulis, Nikos Charizopoulos and Spyros Michas

Water 2021, 13(3), 364; https://doi.org/10.3390/w13030364 - 31 Jan 2021

Cited by 65 | Viewed by 10573

Abstract

Dam breach has disastrous consequences for the economy and human lives. Floods are one of the most damaging natural phenomena, and some of the most catastrophic flash floods are related to dam collapses. The goal of the present study is to analyse the [...] Read more.

Dam breach has disastrous consequences for the economy and human lives. Floods are one of the most damaging natural phenomena, and some of the most catastrophic flash floods are related to dam collapses. The goal of the present study is to analyse the impact of a possible failure–collapse on a potentially affected area downstream of the existing Bramianos dam on southern Crete Island. HEC-RAS hydraulic analysis software was used to study the dam breach, the flood wave propagation, and estimate the extent of floods. The analysis was performed using two different relief datasets of the same area: a digital elevation model (DEM) taken from very high-resolution orthophoto images (OPH) of the National Cadastre and Mapping Agency SA and a detailed digital surface model (DSM) extracted from aerial images taken by an unmanned aerial vehicle (UAV). Remote sensing data of the Sentinel-2 satellite and OPH were utilised to create the geographic information system (GIS) layers of a thorough land use/cover classification (LULC) for the potentially flooded area, which was used to assess the impact of the flood wave. Different dam breach and flood scenarios, where the water flows over man-made structures, settlements, and olive tree cultivations, were also examined. The study area is dominated mainly by three geological formations with different hydrogeological characteristics that dictated the positioning and structure of the dam and determine the processes that shape the geomorphology and surface roughness of the floodplain, affecting flow conditions. The results show that the impact of a potential dam break at Bramianos dam is serious, and appropriate management measures should be taken to reduce the risk. The water flow downstream of the collapsed dam depends on the water volume stored in the reservoir. Moreover, the comparison of DSM and DEM cases shows that the detailed DSM may indicate more accurately the surface relief and existing natural obstacles such as vegetation, buildings, and greenhouses, enabling more realistic hydraulic simulation results. Dam breach flood simulations and innovative remote sensing data can provide valuable outcomes for engineers and stakeholders for decision-making and planning in order to confront the consequences of similar incidents worldwide. Full article

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18 pages, 6407 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Using AHP and Spatial Analysis to Determine Water Surface Storage Suitability in Cambodia

by Michael Ward, Cristina Poleacovschi and Michael Perez

Water 2021, 13(3), 367; https://doi.org/10.3390/w13030367 - 31 Jan 2021

Cited by 9 | Viewed by 4069

Abstract

Cambodia suffers from devastating droughts in the dry season and floods in the wet season. These events’ impacts are further amplified by ineffective water resources infrastructure that cannot retain water during the dry season. Water harvesting (the collection and management of floodwater or [...] Read more.

Cambodia suffers from devastating droughts in the dry season and floods in the wet season. These events’ impacts are further amplified by ineffective water resources infrastructure that cannot retain water during the dry season. Water harvesting (the collection and management of floodwater or rainwater runoff to increase water supply for domestic and agricultural use) is an approach that could improve Cambodia’s resiliency against droughts and floods. Despite the known benefits of water harvesting, there are currently few studies on water harvesting suitability in Cambodia. This research argues that suitable water harvesting sites can be identified by combining various expertise and evaluating hydrologic site conditions. Thirty-one local and USA water infrastructure experts made pairwise comparisons between essential engineering criteria: soil drainage, geologic porosity, precipitation, land cover, and slope. Then, model weights were calculated based on the comparisons. Using the model weights, a water harvesting suitability model showed that 19% of Cambodian land has high suitability, and about 13% of the land has the best suitability. This water harvesting model can help guide future water infrastructure projects to improve climate resiliency by identifying suitable sites for water harvesting reservoirs. Full article

(This article belongs to the Section Hydrology)

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18 pages, 2507 KiB

Open AccessEditor’s ChoiceArticle

Technological Spaces in the Semi-Arid High Plains: Examining Well Ownership and Investment in Water-Saving Appliances

by Brock Ternes

Water 2021, 13(3), 365; https://doi.org/10.3390/w13030365 - 31 Jan 2021

Cited by 2 | Viewed by 3993

Abstract

Groundwater depletion has been a consequential problem in Kansas, a drought-prone state widely reliant on the High Plains aquifer. This manuscript explores well ownership’s moderating effects on the relationships between awareness of water supplies and the use of water-saving devices. It assesses one [...] Read more.

Groundwater depletion has been a consequential problem in Kansas, a drought-prone state widely reliant on the High Plains aquifer. This manuscript explores well ownership’s moderating effects on the relationships between awareness of water supplies and the use of water-saving devices. It assesses one of the only quantitative datasets of private water well owners used in social scientific research (n = 864) and discusses the intricate results of multi-group structural equation models with respondents organized by their water supplies. Well ownership and water literacy are significantly correlated to owning water-conservation technologies, and well ownership combined with access to municipal water weakens the correlations between awareness and owning water-saving appliances. Full article

(This article belongs to the Special Issue Advances in Ecohydrology for Water Resources Optimization in Arid and Semi-arid Areas)

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15 pages, 8362 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analysis of the Arbovirosis Potential Occurrence in Dobrogea, Romania

by Carmen Maftei, Alina Bărbulescu, Sorin Rugina, Cristian Dorin Nastac and Irina Magdalena Dumitru

Water 2021, 13(3), 374; https://doi.org/10.3390/w13030374 - 31 Jan 2021

Cited by 7 | Viewed by 3864

Abstract

Climate change creates new challenges for preventing and protecting human health against different diseases that could appear and propagate. The Aedes albopictus mosquito species is an important vector for different diseases like dengue fever or zika. Although this species is not “indigenous” in [...] Read more.

Climate change creates new challenges for preventing and protecting human health against different diseases that could appear and propagate. The Aedes albopictus mosquito species is an important vector for different diseases like dengue fever or zika. Although this species is not “indigenous” in Europe, its presence is noticed in many countries on the continent. The Ae. albopictus establishment is conditioned by the species’ characteristics and environmental factors. To assess the possible spread of Ae. albopictus in the Dobrogea region (situated in the Southeast of Romania), we conducted the following analysis: (1) Investigation of the current distribution and climatic factors favoring Ae. albopictus’ establishment in Europe; (2) Analysis of climate dynamics in Dobrogea in terms of the parameters identified at stage (1); (3) Testing the hypothesis that the climate from Dobrogea favors Ae. albopictus’ establishment in the region; (4) Building a Geographic Information System (GIS)-based model of the potential geographic distribution of Ae. albopictus in Dobrogea. Results show that the climate of Dobrogea favors the apparition of the investigated species and its proliferation. Full article

(This article belongs to the Special Issue Climate Change and Water, Sanitation and Hygiene (WASH): Resilience, Adaptation and Emissions)

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26 pages, 10882 KiB

Open AccessEditor’s ChoiceArticle

Long-Term Spatiotemporal Variation of Droughts in the Amazon River Basin

by Franklin Paredes-Trejo, Humberto Alves Barbosa, Jason Giovannettone, T. V. Lakshmi Kumar, Manoj Kumar Thakur and Catarina de Oliveira Buriti

Water 2021, 13(3), 351; https://doi.org/10.3390/w13030351 - 30 Jan 2021

Cited by 25 | Viewed by 6748

Abstract

The Amazon River Basin (ARB) plays an important role in the hydrological cycle at the regional and global scales. According to the Intergovernmental Panel on Climate Change (IPCC), the incidence and severity of droughts could increase in this basin due to human-induced climate [...] Read more.

The Amazon River Basin (ARB) plays an important role in the hydrological cycle at the regional and global scales. According to the Intergovernmental Panel on Climate Change (IPCC), the incidence and severity of droughts could increase in this basin due to human-induced climate change. Therefore, the assessment of the impacts of extreme droughts in the ARB is of vital importance to develop appropriate drought mitigation strategies. The purpose of this study is to provide a comprehensive characterization of dry spells and extreme drought events in terms of occurrence, persistence, spatial extent, severity, and impacts on streamflow and vegetation in the ARB during the period 1901–2018. The Standardized Precipitation-Evapotranspiration Index (SPEI) at multiple time scales (i.e., 3, 6, and 12 months) was used as a drought index. A weak basin-wide drying trend was observed, but there was no evidence of a trend in extreme drought events in terms of spatial coverage, intensity, and duration for the period 1901–2018. Nevertheless, a progressive transition to drier-than-normal conditions was evident since the 1970s, coinciding with different patterns of coupling between the El Niño/Southern Oscillation (ENSO) phenomenon and the Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and Madden–Julian Oscillation (MJO) as well as an increasing incidence of higher-than-normal surface air temperatures over the basin. Furthermore, a high recurrence of short-term drought events with high level of exposure to long-term drought conditions on the sub-basins Ucayali, Japurá-Caquetá, Jari, Jutaí, Marañón, and Xingu was observed in recent years. These results could be useful to guide social, economic, and water resource policy decision-making processes in the Amazon basin countries. Full article

(This article belongs to the Special Issue Global Changes in Drought Frequency and Severity)

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14 pages, 9964 KiB

Open AccessEditor’s ChoiceArticle

Effect of Shallow-Buried High-Intensity Mining on Soil Water Content in Ningtiaota Minefield

by Fan Cui, Yunfei Du, Jianyu Ni, Zhirong Zhao and Shiqi Peng

Water 2021, 13(3), 361; https://doi.org/10.3390/w13030361 - 30 Jan 2021

Cited by 8 | Viewed by 3238

Abstract

Shallow-buried high-intensity mining (SHM) activities commonly in China’s western mining area will lead to the decrease of groundwater level and soil water content (SWC), which will aggravate the further deterioration of the local fragile ecological environment. In this study, the applicability and limitations [...] Read more.

Shallow-buried high-intensity mining (SHM) activities commonly in China’s western mining area will lead to the decrease of groundwater level and soil water content (SWC), which will aggravate the further deterioration of the local fragile ecological environment. In this study, the applicability and limitations of six typical soil dielectric models were comprehensively evaluated based on ground penetrating radar (GPR) technology and shallow drilling methods. Moreover, experiments were performed to test the variation of SWC in Ningtiaota minefield affected by the SHM. The results show that the fitting effect of the four empirical models and two semi-empirical models on the clay is better than that of the medium sand. Among the six models, the Ledieu model has the best performance for medium sand, and the Topp model for clay. After SHM, the shallow SWC decreases as a whole. The decreasing range is 4.37–15.84%, showing a gradual downward trend compared with the one before mining. The shorter the lagging working face distance, the greater the drop of SWC will be. The longer the lagging working face distance, the smaller the drop of SWC will be showing a gradual and stable trend. Full article

(This article belongs to the Special Issue Recent Progress in Linking Soil Science and Hydrology)

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25 pages, 7621 KiB

Open AccessEditor’s ChoiceArticle

Projection of Climate Change and Consumptive Demands Projections Impacts on Hydropower Generation in the São Francisco River Basin, Brazil

by Marx Vinicius Maciel da Silva, Cleiton da Silva Silveira, José Micael Ferreira da Costa, Eduardo Sávio Passos Rodrigues Martins and Francisco das Chagas Vasconcelos Júnior

Water 2021, 13(3), 332; https://doi.org/10.3390/w13030332 - 29 Jan 2021

Cited by 23 | Viewed by 4369

Abstract

Climate change impacts may influence hydropower generation, especially with the intensification of extreme events and growing demand. In this study, we analyzed future hydroelectric generation using a set of scenarios considering both climate change and consumptive demands in the São Francisco River Basin. [...] Read more.

Climate change impacts may influence hydropower generation, especially with the intensification of extreme events and growing demand. In this study, we analyzed future hydroelectric generation using a set of scenarios considering both climate change and consumptive demands in the São Francisco River Basin. This project will increase consumptive demands for the coming decades. Five models from the recently released Coupled Model Intercomparison Project Phase 6 and two scenarios, SSP2-4.5 and SSP5-8.5, were considered to estimate climate change projections. The affluent natural flows, regulated flows, and the hydroelectric energy generated were estimated for four multi-purpose reservoirs considering all existing and new demands. The conjunction of scenarios indicated a possible significant reduction in water availability, increased consumptive demands, especially for irrigation, and reduced power generation. Only at the Sobradinho hydroelectric plant, the decrease ranged from −30% to −50% for the period 2021 to 2050 compared to the historical period (1901 to 2000). The results can provide insights into future energy generation and water resources management in the basin. Full article

(This article belongs to the Special Issue Hydro-Meteorological Hazards under Climate Change)

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20 pages, 6906 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Remote Sensing and Re-Analysis Estimates of Regional Precipitation over Mato Grosso, Brazil

by Altemar L. Pedreira Junior, Marcelo S. Biudes, Nadja G. Machado, George L. Vourlitis, Hatim M. E. Geli, Luiz Octávio F. dos Santos, Carlos A. S. Querino, Israel O. Ivo and Névio Lotufo Neto

Water 2021, 13(3), 333; https://doi.org/10.3390/w13030333 - 29 Jan 2021

Cited by 14 | Viewed by 6179

Abstract

The spatial and temporal distribution of precipitation is of great importance for the rain-fed agricultural production and the socioeconomics of Mato Grosso (MT), Brazil. MT has a sparse network of ground rain gauges that limits the effective use of precipitation information for sustainable [...] Read more.

The spatial and temporal distribution of precipitation is of great importance for the rain-fed agricultural production and the socioeconomics of Mato Grosso (MT), Brazil. MT has a sparse network of ground rain gauges that limits the effective use of precipitation information for sustainable agricultural production and water resources in the region. Several gridded precipitation products from remote sensing and reanalysis of land surface models are currently available that can enhance the use of such information. However, these products are available at different spatial and temporal resolutions which add some challenges to stakeholders (users) to identify their appropriateness for specific applications (e.g., irrigation requirements, length of growing season, and drought monitoring). Thus, it is necessary to provide an assessment of the reliability of these precipitation estimates. The objective of this work was to compare regional precipitation estimates over MT as provided by the Global Land Data Assimilation (GLDAS), Modern-Era Retrospective Analysis for Research and Applications (MERRA), Tropical Rainfall Measurement Mission (TRMM), Global Precipitation Measurement (GPM), and the Global Precipitation Climatology Project (GPCP) with ground-based measurements. The comparison was conducted for the 2000–2018 period at eleven ground-based weather stations that covered different climate zones in MT using daily, monthly, and annual temporal resolutions. The comparison used the Pearson correlation index–r, Willmott index–d, root mean square error—RMSE, and the Wilks methods. The results showed GPM and GLDAS estimates did not differ significantly with the measured daily, monthly, and annual precipitation. TRMM estimates slightly overestimated daily precipitation by about 4.7% but did not show significant difference on the monthly and annual scales when compared with local measurements. The GPCP underestimated annual precipitation by about 7.1%. MERRA underestimated daily, monthly, and annual precipitation by about 22.9% on average. In general, all products satisfactorily estimated monthly precipitation, and most of them satisfactorily estimated annual precipitation; however, they showed low accuracy when estimating daily precipitation. The TRMM, GPM, GPCP, and GLDAS estimates had the highest performance, from high to low, while MERRA showed the lowest performance. The findings of this study can be used to support the decision-making process in the region in application related to water resources management, sustainability of agriculture production, and drought management. Full article

(This article belongs to the Special Issue Remote Sensing in Water Cycle Management)

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16 pages, 4307 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Operationalizing Urban Resilience to Floods in Island Territories—Application in Punaauia, French Polynesia

by Yoann Lamaury, Jérémy Jessin, Charlotte Heinzlef and Damien Serre

Water 2021, 13(3), 337; https://doi.org/10.3390/w13030337 - 29 Jan 2021

Cited by 19 | Viewed by 4586

Abstract

In the context of climate change and increasing urbanization, Small Island Developing States are increasingly vulnerable to natural disasters. In response to urbanization in at risk areas, the concept of territorial resilience has potential as an approach to urban flood issues. The objective [...] Read more.

In the context of climate change and increasing urbanization, Small Island Developing States are increasingly vulnerable to natural disasters. In response to urbanization in at risk areas, the concept of territorial resilience has potential as an approach to urban flood issues. The objective of this research is to develop a spatial decision support tool based on a collaborative assessment method of territorial resilience. The proposed methodology consists of: the adaptation to the French Polynesian context, three existing resilience assessment methods applied to a case study in the Punaruu Valley’s (Punaauia, French Polynesia) and the use of geovisualization techniques: use of GIS for data processing and analysis, visualization, mapping and model processing. This methodology integrates the technical, urban and social components of the territory, while highlighting the various levers available to improve territorial resilience and facilitate its understanding through collaborative work efforts and the use of a visual tool. The results demonstrate the reproducibility of these methods for assessing resilience in French Polynesia. They underline the potential of a collaborative approach to highlight critical infrastructures and generate possible decision support to improve the territory’s ability to function despite a disruption and the ability to rebuild following this disruption. Full article

(This article belongs to the Special Issue GIS Application: Flood Risk Management)

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21 pages, 7506 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Uncertainty Analysis of SWAT Modeling in the Lancang River Basin Using Four Different Algorithms

by Xiongpeng Tang, Jianyun Zhang, Guoqing Wang, Junliang Jin, Cuishan Liu, Yanli Liu, Ruimin He and Zhenxin Bao

Water 2021, 13(3), 341; https://doi.org/10.3390/w13030341 - 29 Jan 2021

Cited by 44 | Viewed by 5461

Abstract

The hydrological model is the primary tool for regional water resources management, allocation, and prediction. However, these models always suffer from large uncertainties from multiple sources. Therefore, it is necessary to conduct an uncertainty analysis before performing hydrological simulation. Sequential Uncertainty Fitting (SUFI-2), [...] Read more.

The hydrological model is the primary tool for regional water resources management, allocation, and prediction. However, these models always suffer from large uncertainties from multiple sources. Therefore, it is necessary to conduct an uncertainty analysis before performing hydrological simulation. Sequential Uncertainty Fitting (SUFI-2), Parameter Solution (ParaSol), Generalized Likelihood Uncertainty Estimation (GLUE), and Particle Swarm Optimization (PSO) integrated with the SWAT-CUP software were used to calibrate the Soil and Water Assessment Tool (SWAT) model and quantify the parameter sensitivity and prediction uncertainty of the SWAT in the Lancang River (LR) Basin, which is located in the southwest of China. This model was calibrated and validated using the four algorithms both at the daily scale, and the optimal simulation results derived by the four methods showed that the SWAT model performed well over the Yunjinghong station with Nash–Sutcliffe efficiency coefficient (NSE) and coefficient of determination (R²) values greater than 0.8 both in the calibration (1975 to 1989) and validation (1990 to 2004) periods. Among the four algorithms, the ParaSol algorithm produced the best simulation result at the daily scale with NSE values of 0.89 and 0.90 for the calibration and validation periods, respectively. Furthermore, the ParaSol algorithm has the greatest proportion of simulations (94%) with an NSE greater than 0.5. Parameter sensitivity analysis results demonstrated that the four methods all can be used for parameter sensitivity analysis in streamflow simulation, and they all identified that the base flow factor for bank storage (ALPHA_BNK) and effective hydraulic conductivity in the main channel alluvium (CH_K2) were more sensitive. The uncertainty analysis of model parameters showed that the parameter 95PPU (95% prediction uncertainty) width yielded by the ParaSol algorithm was the smallest compared with that of the other methods, followed by PSO, SUFI-2, and GLUE. The uncertainty analysis of the model simulation indicated that the SUFI-2 and PSO methods can achieve satisfactory results (with P-factor > 0.7 and R-factor < 1.5) at the daily scale; among them, SUFI-2 (P-factor = 0.93, R-factor = 1.17) performed much better than PSO (P-factor = 0.78, R-factor = 1.14). In general, by comparing its evaluation criteria (NSE, R², RE, P-factor, and R-factor) to other methods, ParaSol stood out as the most efficient tool for model calibration. However, SUFI-2 remains the most robust method to perform uncertainty analysis considering its uncertainties of model structure, model inputs, and parameters. This study provides insight into hydrological simulation of the LR Basin using the appropriate algorithm to calibrate the model and implement the uncertainty analysis. Full article

(This article belongs to the Special Issue Hydrological Modeling in Water Cycle Processes)

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15 pages, 27861 KiB

Open AccessEditor’s ChoiceArticle

Effect of Freeze-Thaw Cycles on Soil Detachment Capacities of Three Loamy Soils on the Loess Plateau of China

by Jian Lu, Baoyang Sun, Feipeng Ren, Hao Li and Xiyun Jiao

Water 2021, 13(3), 342; https://doi.org/10.3390/w13030342 - 29 Jan 2021

Cited by 28 | Viewed by 3488

Abstract

Soil detachment is the initial phase of soil erosion and is of great significance to study in seasonal freeze-thaw regions. In order to elucidate the effects mechanism of freeze-thaw cycles on soil detachment capacity of different soils, a sandy loam, a silt loam, [...] Read more.

Soil detachment is the initial phase of soil erosion and is of great significance to study in seasonal freeze-thaw regions. In order to elucidate the effects mechanism of freeze-thaw cycles on soil detachment capacity of different soils, a sandy loam, a silt loam, and a clay loam were subjected to 0, 1, 5, 10, 15, and 20 freeze-thaw cycles before they were scoured. The results revealed that with increased freeze-thaw cycles, soil bulk density and water-stable aggregates content decreased after the first few times and then kept nearly stable after about 10 cycles, especially for sandy loam. The shear strength of all soils gradually decreased as freeze-thaw cycles increased, except the values of clay loam increased subsequent to the 5th and 15th cycles. After the 20th cycle, the degree of decline of silt loam was the greatest (77.72%), followed by sandy loam (63.18%) and clay loam (39.77%). The soil organic matter of clay loam was much greater than silt loam and sandy loam and all significantly increased after freeze-thaw. Soil detachment capacity of silt loam and sandy loam was positively correlated with freeze-thaw cycle, which was contrary to findings for clay loam. The values of clay loam increased at first and then decreased during the cycles, reaching minimum values at about the 15–20th cycle. After the 20th cycle, the values of sandy loam and silt loam significantly increased 1.62 and 4.74 times over unfrozen, respectively, which was greater than clay loam (0.53 times). A nonlinear regression analysis indicated that the soil detachment capacity of silt loam could be estimated well by soil properties (R² = 0.87, p < 0.05). This study can provide references for the study of the soil erosion mechanism in seasonal freeze-thaw regions. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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