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Editor’s Choice Articles

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

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28 pages, 379 KiB  
Article
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 3 | Viewed by 8247
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)
17 pages, 1845 KiB  
Article
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 2989
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  
Communication
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 22 | Viewed by 4402
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  
Article
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 3 | Viewed by 3095
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  
Article
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 22 | Viewed by 7761
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  
Article
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 2704
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 (Kd) 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  
Article
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 7 | Viewed by 2577
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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12 pages, 5155 KiB  
Article
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 12 | Viewed by 3559
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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15 pages, 4396 KiB  
Article
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 4 | Viewed by 2494
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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16 pages, 4256 KiB  
Article
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 4 | Viewed by 2862
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  
Article
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 21 | Viewed by 3207
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 (RW) and the ratio of horizontal and vertical hydraulic conductivity of dewatering aquifer (RC) are varied. The relationship between approximate hydraulic gradient (Δi) and RW (or RC) can be fitted by Boltzmann curve (or logarithmic curve). Effective, suggested and control values of RW (or RC) are proposed, of which the suggested value is recommended in practical engineering. The effective, suggested and control value of RW can be calculated by logarithmical equation considering the value of RC. Full article
(This article belongs to the Section Hydrology)
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17 pages, 2500 KiB  
Article
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 4098
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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21 pages, 4088 KiB  
Article
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 17 | Viewed by 3431
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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23 pages, 5363 KiB  
Article
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 3820
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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28 pages, 776 KiB  
Review
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 27 | Viewed by 6849
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  
Review
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 61 | Viewed by 10616
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  
Article
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 3 | Viewed by 3406
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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22 pages, 14731 KiB  
Article
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 1 | Viewed by 3698
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  
Article
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 15 | Viewed by 3717
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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18 pages, 2929 KiB  
Article
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 13 | Viewed by 3857
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  
Article
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 23 | Viewed by 4592
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  
Article
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 33 | Viewed by 4852
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  
Article
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 16 | Viewed by 4425
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  
Article
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 18 | Viewed by 5791
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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18 pages, 2507 KiB  
Article
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 3611
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  
Article
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 3282
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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13 pages, 4276 KiB  
Article
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 2505
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  
Article
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 52 | Viewed by 8775
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  
Article
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 3458
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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26 pages, 10882 KiB  
Article
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 19 | Viewed by 5548
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  
Article
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 7 | Viewed by 2723
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  
Article
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 19 | Viewed by 3782
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  
Article
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 12 | Viewed by 5669
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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21 pages, 7506 KiB  
Article
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 31 | Viewed by 3583
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  
Article
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 15 | Viewed by 2741
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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16 pages, 4307 KiB  
Article
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 15 | Viewed by 3783
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, 3420 KiB  
Article
Secondary Currents with Scour Hole at Grade Control Structures
by Mouldi Ben Meftah, Diana De Padova, Francesca De Serio and Michele Mossa
Water 2021, 13(3), 319; https://doi.org/10.3390/w13030319 - 28 Jan 2021
Cited by 6 | Viewed by 2100
Abstract
Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of [...] Read more.
Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of flow velocities in clear water scours downstream of a grade control structure in a channel with non-cohesive sediments, in this study, we attempted to investigate the generation and turbulence properties of secondary currents across a scour hole at equilibrium condition. The flow velocity distributions through the cross-sectional planes at the downstream location of the maximum equilibrium scour depth clearly show the development of secondary current cells. The secondary currents form a sort of helical-like motion, occurring in both halves of the cross-section in an axisymmetric fashion. A detailed analysis of the turbulence intensities and Reynolds shear stresses was carried out and compared with previous studies. The results highlight considerable spatial heterogeneities of flow turbulence. The anisotropy term of normal stresses dominates the secondary shear stress, giving the impression of its crucial role in generating secondary flow motion across the scour hole. The anisotropy term shows maximum values near both the scour mouth and the scour bed, caused, respectively, by the grade control structure and the sediment ridge formation, which play fundamental roles in maintaining and enhancing the secondary flow motion. Full article
(This article belongs to the Special Issue Flow Hydrodynamic in Open Channels: Interaction with Natural or Man-Made Structures)
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21 pages, 850 KiB  
Review
Blue Water Visitor Monitoring Potential: A Literature Review and Alternative Proposal
by Ross G. Andrew, Robert C. Burns, Danielle Schwarzmann, Mary E. Allen and Jasmine Cardozo Moreira
Water 2021, 13(3), 305; https://doi.org/10.3390/w13030305 - 27 Jan 2021
Cited by 3 | Viewed by 2914
Abstract
This review presents a summary of existing visitor monitoring methods and relevant studies in land and marine-based areas, with a focus on the application to unique aquatic settings. Various opportunities and challenges exist with respect to the use of each method in different [...] Read more.
This review presents a summary of existing visitor monitoring methods and relevant studies in land and marine-based areas, with a focus on the application to unique aquatic settings. Various opportunities and challenges exist with respect to the use of each method in different marine settings. These methods differ in terms of the complexity, costs, level of accuracy, and detailed information they provide. Furthermore, the feasibility of applying these methods also depends on the site attributes of a marine area. Since each marine area varies in geographical scale and environmental and social conditions, some methods will be more appropriate or perform more successfully than others in a particular location. Therefore, the consideration of these methods should be part of a proposed alternative process, focused on adaptive monitoring that scales to address visitor ebbs and flows in these aquatic areas. The proposed alternative seeks to develop consensus around quantitative goals for visitor monitoring and estimating techniques in marine settings, using a customizable mix of methods and techniques. This alternative effort progresses to subsequent tasks and discussions, and recommendations are made considering the feasibility and confidence of using these methods in particular marine settings and future pilot sites. Full article
(This article belongs to the Special Issue The Blue Economy: Evaluating the Human Benefits from and Pressures on Marine and Coastal Environments)
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25 pages, 7917 KiB  
Article
The Significance of Vertical and Lateral Groundwater–Surface Water Exchange Fluxes in Riverbeds and Riverbanks: Comparing 1D Analytical Flux Estimates with 3D Groundwater Modelling
by Gert Ghysels, Christian Anibas, Henock Awol, Abebe Debele Tolche, Uwe Schneidewind and Marijke Huysmans
Water 2021, 13(3), 306; https://doi.org/10.3390/w13030306 - 27 Jan 2021
Cited by 14 | Viewed by 3515
Abstract
Riverbed temperature profiles are frequently used to estimate vertical river–aquifer exchange fluxes. Often in this approach, strictly vertical flow is assumed. However, riverbeds are heterogeneous structures often characterised by complex flow fields, possibly violating this assumption. We characterise the meter-scale variability of river–aquifer [...] Read more.
Riverbed temperature profiles are frequently used to estimate vertical river–aquifer exchange fluxes. Often in this approach, strictly vertical flow is assumed. However, riverbeds are heterogeneous structures often characterised by complex flow fields, possibly violating this assumption. We characterise the meter-scale variability of river–aquifer interaction at two sections of the Aa River, Belgium, and compare vertical flux estimates obtained with a 1D analytical solution to the heat transport equation with fluxes simulated with a 3D groundwater model (MODFLOW) using spatially distributed fields of riverbed hydraulic conductivity. Based on 115 point-in-time riverbed temperature profiles, vertical flux estimates that are obtained with the 1D solution are found to be higher near the banks than in the center of the river. The total exchange flux estimated with the 3D groundwater model is around twice as high as the estimate based on the 1D solution, while vertical flux estimates from both methods are within a 10% margin. This is due to an important contribution of non-vertical flows, especially through the riverbanks. Quasi-vertical flow is only found near the center of the river. This quantitative underestimation should be considered when interpreting exchange fluxes based on 1D solutions. More research is necessary to assess conditions for which using a 1D analytical approach is justified to more accurately characterise river–aquifer exchange fluxes. Full article
(This article belongs to the Section Hydrology)
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15 pages, 4003 KiB  
Article
Impacts of Irrigation Water on the Hydrodynamics and Saline Behavior of the Shallow Alluvial Aquifer in the Senegal River Delta
by Abdoul Aziz Gning, Philippe Orban, Raymond Malou, Joost Wellens, Johan Derouane, Mansour Gueye and Serge Brouyère
Water 2021, 13(3), 311; https://doi.org/10.3390/w13030311 - 27 Jan 2021
Cited by 1 | Viewed by 2040
Abstract
The Senegal River Delta located in north-western Senegal is a strategic region for the development of irrigated rice cultivation for achieving rice self-sufficiency. The presence of a shallow salty water table is often considered as a brake to the development of irrigation, by [...] Read more.
The Senegal River Delta located in north-western Senegal is a strategic region for the development of irrigated rice cultivation for achieving rice self-sufficiency. The presence of a shallow salty water table is often considered as a brake to the development of irrigation, by causing salinization of the soil, although the mechanisms of operation are not well known. An experimental study was carried out in a rice paddy located in the village of Ndiaye, 35 km north from Saint Louis, to characterize the water and solute flux processes below the irrigated plots. The objective was to better understand the irrigation-driven dynamics of soil salinization processes. An experimental monitoring network was installed for monitoring the transit of water at the plot level, in the unsaturated zone and in the aquifer. The results show that the supply of water by irrigation contributes to significantly recharging the water table, as shown by the rise in piezometric level, with a concomitant dilution of the water salinity in the soil zone and in the shallow groundwater. However, when irrigation is stopped, the groundwater level and salinity return within a month to their initial level and salinity status because of the evaporative recovery, which strongly governs these processes. Thus, water flow and solute transfers operate in the delta following a recharge–discharge and dilution–concentration cycle controlled by the water balance, and we do not expect to observe in the short- to middle-term any significant reduction in soil salinization processes by drainage. Full article
(This article belongs to the Section Hydrology)
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21 pages, 4882 KiB  
Article
An RF-PCE Hybrid Surrogate Model for Sensitivity Analysis of Dams
by Mohammad Amin Hariri-Ardebili, Golsa Mahdavi, Azam Abdollahi and Ali Amini
Water 2021, 13(3), 302; https://doi.org/10.3390/w13030302 - 26 Jan 2021
Cited by 33 | Viewed by 4435
Abstract
Quantification of structural vibration characteristics is an essential task prior to perform any dynamic health monitoring and system identification. Anatomy of vibration in concrete arch dams (especially tall dams with un-symmetry shape) is very complicated and requires special techniques to solve the eigenvalue [...] Read more.
Quantification of structural vibration characteristics is an essential task prior to perform any dynamic health monitoring and system identification. Anatomy of vibration in concrete arch dams (especially tall dams with un-symmetry shape) is very complicated and requires special techniques to solve the eigenvalue problem. The situation becomes even more complicated if the material distribution is assumed to be heterogeneous within the dam body (as opposed to conventional isotropic homogeneous relationship). This paper proposes a hybrid Random Field (RF)–Polynomial Chaos Expansion (PCE) surrogate model for uncertainty quantification and sensitivity assessment of dams. For different vibration modes, the most sensitive spatial locations within dam body are identified using both Sobol’s indices and correlation rank methods. Results of the proposed hybrid model is further validated using the classical random forest regression method. The outcome of this study can improve the results of system identification and dynamic analysis by properly determining the vibration characteristics. Full article
(This article belongs to the Special Issue Soft Computing and Machine Learning in Dam Engineering)
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17 pages, 10459 KiB  
Article
Water Lice and Other Macroinvertebrates in Drinking Water Pipes: Diversity, Abundance and Health Risk
by Günter Gunkel, Ute Michels and Michael Scheideler
Water 2021, 13(3), 276; https://doi.org/10.3390/w13030276 - 24 Jan 2021
Cited by 14 | Viewed by 4850
Abstract
Activities to ensure and maintain water quality in drinking water networks, including flushing, are presented after standardized hydrant sampling combined with a stainless-steel low pressure–high flow rate (NDHF) filter and a 100 µm mesh size was used to separate pipe inhabitants. A databank [...] Read more.
Activities to ensure and maintain water quality in drinking water networks, including flushing, are presented after standardized hydrant sampling combined with a stainless-steel low pressure–high flow rate (NDHF) filter and a 100 µm mesh size was used to separate pipe inhabitants. A databank of more than 1000 hydrant samples in European lowland areas was developed and used to analyze the diversity and abundance of macroinvertebrates in drinking water networks. Load classes for water louse (Asellus aquaticus) and oligochaetes are given with three evaluation classes: normal colonization, increased colonization, and mass development. The response of Asellus aquaticus in drinking water networks to environmental conditions are presented as are their growth and reproduction, promotion of a third generation by climate change effects, food limitations, and the composition and stability of their feces. Finally, the health risks posed by dead water lice and water lice feces with bacterial regrowth and the promotion of microbe development on house filters are analyzed. Full article
(This article belongs to the Special Issue Multi-Quality Water Distribution Systems Analysis: Simulation and Management)
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18 pages, 307 KiB  
Article
Equity vs. Efficiency and the Human Right to Water
by Manuel Prieto
Water 2021, 13(3), 278; https://doi.org/10.3390/w13030278 - 24 Jan 2021
Cited by 12 | Viewed by 4350
Abstract
One of the most crucial discussions within water resource management is the debate between those who defend the concept of economic efficiency and those who privilege notions of social equity. This tension is located at the core of binary categories that currently constitute [...] Read more.
One of the most crucial discussions within water resource management is the debate between those who defend the concept of economic efficiency and those who privilege notions of social equity. This tension is located at the core of binary categories that currently constitute the public debate within comparative water law and policy. These categories are commodity/human right, private property/common property, free-market/state regulation, and market value/community value. This paper explores this tension by studying how neoclassical economics understands efficiency and tracing its rise as a key hegemonic principle for water resource management. I also present equity as a conceptual opposition to efficiency and describe its institutionalization through the human-right-to-water frame. A problematization of both the equity approach and the human-right-to-water frame follows. Finally, I propose a political ecology approach to better understand the tension between efficiency and equity and offer recommendations for informing the water research agenda on efficiency/equity. Full article
(This article belongs to the Special Issue The Politics of the Human Right to Water)
23 pages, 14115 KiB  
Article
Performance Improvement of a Drag Hydrokinetic Turbine
by Mabrouk Mosbahi, Mariem Lajnef, Mouna Derbel, Bouzid Mosbahi, Costanza Aricò, Marco Sinagra and Zied Driss
Water 2021, 13(3), 273; https://doi.org/10.3390/w13030273 - 23 Jan 2021
Cited by 11 | Viewed by 3460
Abstract
Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a [...] Read more.
Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a very low environmental impact due to their negligible effect on solid transport. Among them, kinetic turbines with vertical axis are very inexpensive and have almost zero impact on fish and local fauna. In application to tidal waves and sea waves, where vertically averaged velocities have alternate direction, a Savonius rotor also has the advantage of being productive during the whole time cycle. In this work, the effect of an upstream deflector system mounted upstream of a twisted Savonius rotor inside a channel has been investigated through numerical simulations and experimental tests. Numerical simulations were carried on using the ANSYS FLUENT 17.0 software. Based on this numerical study, it is shown that the proposed deflector system has improved the power coefficient of the Savonius rotor by 14%. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas. Full article
(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)
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21 pages, 7330 KiB  
Article
Experimental Study on Landslides in Terraced Fields in the Chinese Loessial Region under Extreme Rainfall
by Yongfu Wen, Peng Gao, Xingmin Mu, Mengzhen Li, Yongjun Su and Haixing Wang
Water 2021, 13(3), 270; https://doi.org/10.3390/w13030270 - 22 Jan 2021
Cited by 10 | Viewed by 3159
Abstract
Due to the development of the scale of tractor-ploughed terraces, terraces have been increasing in number, while global climate change is causing frequent extreme rainfall events in the Loess Plateau, resulting in many terrace landslides. To study the mechanism and process of shallow [...] Read more.
Due to the development of the scale of tractor-ploughed terraces, terraces have been increasing in number, while global climate change is causing frequent extreme rainfall events in the Loess Plateau, resulting in many terrace landslides. To study the mechanism and process of shallow landslides and deep slip surface of terraces induced by extreme rainfall in loess hill and gully area, we conducted a laboratory model test of a terrace under artificial rainfall and used the Swedish arc strip method. The research results are as follows. The mechanism of shallow landslides in terraces is rill erosion accelerating rainfall infiltration, suspending the slope, and increasing its bulk density. The destruction process of shallow landslides can be roughly divided into six processes, and the earth volume of the landslide is 0.24 m3. The mechanism of the deep sliding surface in terraces occurs under the combined action of water erosion and gravity erosion. The soil moisture content increases, which decreases the anti-sliding moment and increases the sliding moment, and the safety factor becomes less than the allowable limit for terraces. The deep sliding deformation area of the terrace was 0~1.0 m below the slope surface, slip surface radius was 1.43 m, the slip surface angle was 92°, and the deep sliding surface began to form earlier than terraced shallow landslides. The displacement of the characteristic points increased from the slope top, to the slope center, and to the slope foot, with maximum displacements of 40.3, 15.5, and 6.0 mm, respectively. Full article
(This article belongs to the Special Issue Soil–Water Conservation, Erosion, and Landslide)
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18 pages, 1408 KiB  
Review
The Impacts of Hydropower Dams in the Mekong River Basin: A Review
by Akarath Soukhaphon, Ian G. Baird and Zeb S. Hogan
Water 2021, 13(3), 265; https://doi.org/10.3390/w13030265 - 22 Jan 2021
Cited by 108 | Viewed by 31178
Abstract
The Mekong River, well known for its aquatic biodiversity, is important to the social, physical, and economic health of millions living in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. This paper explores the social and environmental impacts of several Mekong basin hydropower dams [...] Read more.
The Mekong River, well known for its aquatic biodiversity, is important to the social, physical, and economic health of millions living in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. This paper explores the social and environmental impacts of several Mekong basin hydropower dams and groupings of dams and the geographies of their impacts. Specifically, we examined the 3S (Sesan, Sekong Srepok) river system in northeastern Cambodia, the Central Highlands of Vietnam, and southern Laos; the Khone Falls area in southern Laos; the lower Mun River Basin in northeastern Thailand; and the upper Mekong River in Yunnan Province, China, northeastern Myanmar, northern Laos, and northern Thailand. Evidence shows that these dams and groupings of dams are affecting fish migrations, river hydrology, and sediment transfers. Such changes are negatively impacting riparian communities up to 1000 km away. Because many communities depend on the river and its resources for their food and livelihood, changes to the river have impacted, and will continue to negatively impact, food and economic security. While social and environmental impact assessments have been carried out for these projects, greater consideration of the scale and cumulative impacts of dams is necessary. Full article
(This article belongs to the Special Issue Channels for Change: Integrating Multiple Disciplines for New Frontiers in Managing the Mekong River Basin)
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17 pages, 3718 KiB  
Article
Estimating the Pan Evaporation in Northwest China by Coupling CatBoost with Bat Algorithm
by Liming Dong, Wenzhi Zeng, Lifeng Wu, Guoqing Lei, Haorui Chen, Amit Kumar Srivastava and Thomas Gaiser
Water 2021, 13(3), 256; https://doi.org/10.3390/w13030256 - 21 Jan 2021
Cited by 30 | Viewed by 3658
Abstract
Accurate estimation of pan evaporation (Ep) is vital for the development of water resources and agricultural water management, especially in arid and semi-arid regions where it is restricted to set up the facilities and measure pan evaporation accurately and consistently. Besides, [...] Read more.
Accurate estimation of pan evaporation (Ep) is vital for the development of water resources and agricultural water management, especially in arid and semi-arid regions where it is restricted to set up the facilities and measure pan evaporation accurately and consistently. Besides, using pan evaporation estimating models and pan coefficient (kp) models is a classic method to assess the reference evapotranspiration (ET0) which is indispensable to crop growth, irrigation scheduling, and economic assessment. This study estimated the potential of a novel hybrid machine learning model Coupling Bat algorithm (Bat) and Gradient boosting with categorical features support (CatBoost) for estimating daily pan evaporation in arid and semi-arid regions of northwest China. Two other commonly used algorithms including random forest (RF) and original CatBoost (CB) were also applied for comparison. The daily meteorological data for 12 years (2006–2017) from 45 weather stations in arid and semi-arid areas of China, including minimum and maximum air temperature (Tmin, Tmax), relative humidity (RH), wind speed (U), and global solar radiation (Rs), were utilized to feed the three models for exploring the ability in predicting pan evaporation. The results revealed that the new developed Bat-CB model (RMSE = 0.859–2.227 mm·d−1; MAE = 0.540–1.328 mm·d−1; NSE = 0.625–0.894; MAPE = 0.162–0.328) was superior to RF and CB. In addition, CB (RMSE = 0.897–2.754 mm·d−1; MAE = 0.531–1.77 mm·d−1; NSE = 0.147–0.869; MAPE = 0.161–0.421) slightly outperformed RF (RMSE = 1.005–3.604 mm·d−1; MAE = 0.644–2.479 mm·d−1; NSE = −1.242–0.894; MAPE = 0.176–0.686) which had poor ability to operate the erratic changes of pan evaporation. Furthermore, the improvement of Bat-CB was presented more comprehensively and obviously in the seasonal and spatial performance compared to CB and RF. Overall, Bat-CB has high accuracy, robust stability, and huge potential for Ep estimation in arid and semi-arid regions of northwest China and the applications of findings in this study have equal significance for adjacent countries. Full article
(This article belongs to the Section Hydrology)
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15 pages, 3737 KiB  
Article
Climate Control of Multidecadal Variability in River Discharge and Precipitation in Western Europe
by Isabel Jalón-Rojas and Bruno Castelle
Water 2021, 13(3), 257; https://doi.org/10.3390/w13030257 - 21 Jan 2021
Cited by 13 | Viewed by 2917
Abstract
The influence of large-scale climate variability on winter river discharge and precipitation across western Europe is investigated. We analyze 60 years of monthly precipitation and river flow data from 18 major western-European rivers and its relationship with dominant teleconnection patterns and climate indices [...] Read more.
The influence of large-scale climate variability on winter river discharge and precipitation across western Europe is investigated. We analyze 60 years of monthly precipitation and river flow data from 18 major western-European rivers and its relationship with dominant teleconnection patterns and climate indices in this region. Results show that winter river flow is characterized by large interannual variability, best correlates with (a) the North Atlantic Oscillation (NAO) at the far-northern (R up to 0.56) and southern latitudes (R up to −0.72), and (b) the West Europe Pressure Anomaly (WEPA) at the middle and northern latitudes, from 42° N to 55° N (R up to 0.83). These indices also explain the interannual variability in autumn and spring discharge in rivers characterized by secondary floods. Compared to the other leading modes of atmospheric variability, WEPA increases the correlations with winter precipitation up to 0.8 in many regions of western and central Europe. A positive WEPA corresponds to a southward shift and an intensification of the Icelandic-Low/Azores-High dipole, driving enhanced precipitation and river discharge in these regions. The correlations with precipitation are slightly higher than those with river discharge, particularly in France, with clear latitudinal gradient. This trend suggests that water storage variability and other catchment characteristics may also influence the interannual variability of river discharge. Seasonal forecasting of the WEPA and NAO winter indices can become a powerful tool in anticipating hydrological risks in this region. Full article
(This article belongs to the Section Hydrology)
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13 pages, 2599 KiB  
Article
Increase in Daily Household Water Demand during the First Wave of the Covid-19 Pandemic in Germany
by Deike U. Lüdtke, Robert Luetkemeier, Michael Schneemann and Stefan Liehr
Water 2021, 13(3), 260; https://doi.org/10.3390/w13030260 - 21 Jan 2021
Cited by 78 | Viewed by 6967
Abstract
Precautionary measures and governmental regulations during the COVID-19 pandemic’s first wave have drastically altered daily activities and hence water consumption patterns. Many people had to change their working routines, the organization of childcare and hygiene practices. While first evidence appears on the impacts [...] Read more.
Precautionary measures and governmental regulations during the COVID-19 pandemic’s first wave have drastically altered daily activities and hence water consumption patterns. Many people had to change their working routines, the organization of childcare and hygiene practices. While first evidence appears on the impacts of COVID-19 on, e.g., carbon emissions, energy demand and water treatment, even indicating an unexpected increase in water consumption during that period, no study has investigated the pandemic’s sole and in-depth implications for water supply so far. This paper investigates hourly and daily water consumption volumes of a utility in northern Germany for the first wave of the pandemic. We performed a linear mixed model to compare the 2020 daily water consumption volumes with previous years. We eliminated the effects of climate using Bayesian statistic in order to carve out and estimate the original COVID-19 effect. We also compared hourly water consumption of similar time periods and calculated the percentage difference between 2020 and the two previous years. Our results reveal about 14.3% (3 968 m3) higher residential water consumption per day with higher morning and evening demand peaks during the day. We hypothesis that the reasons for the increasing water demand may be found in changed behavioral routines with an important question for water utilities, if and which of these new dynamics may persist after COVID-19 and hence pose a challenge for long-term infrastructure planning. Full article
(This article belongs to the Section Water Use and Scarcity)
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15 pages, 9838 KiB  
Article
How Much Does Water Management Cost? The Case of the Water Market in the Ñuble River of South-Central Chile
by Bratian Buzolic, José Luis Arumí and Jorge Jimenez
Water 2021, 13(3), 258; https://doi.org/10.3390/w13030258 - 21 Jan 2021
Cited by 6 | Viewed by 3075
Abstract
Economic and population growth has increased the demand for freshwater worldwide, generating pressure on the environment and creating conflicts among users. Water markets have emerged as a solution for managing this resource, and Chile has been a pioneer in implementing this approach. However, [...] Read more.
Economic and population growth has increased the demand for freshwater worldwide, generating pressure on the environment and creating conflicts among users. Water markets have emerged as a solution for managing this resource, and Chile has been a pioneer in implementing this approach. However, most Chilean water markets are inefficient due to incomplete information, the poor flexibility of the water distribution system, and high transaction costs. This study analyzes the Ñuble River water market and estimates the economic and social costs of its inefficiencies through a methodology based on the marginal profitability of water, which simulates the operation of a perfect market for the Ñuble River irrigation system. Net benefit losses from market inefficiencies were estimated at 7.6 million dollars annually, which is equivalent to a 25% increase in the net returns of the current river water distribution strategy. Losses of economic benefits are even greater as the availability of water flow decreases. This is important considering that in the last decade the water flows of the Ñuble River have decreased by more than 30% compared to their historical average. Full article
(This article belongs to the Special Issue Analysis, Evaluation and Optimization of Infrastructures Serving Water Systems)
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