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Water, Volume 13, Issue 21 (November-1 2021) – 208 articles

Cover Story (view full-size image): Hidden away in the heart of the deep south is the Cahaba River, one of the most biodiverse ecosystems in North America. Among some of its unique species and habitats is the Cahaba lily, an iconic plant that can only be spotted in a handful of places on planet Earth. Like other aquatic species, the Cahaba lilies require very specific flow conditions to thrive. This study demonstrates how land use/cover (LULC) input data in hydrologic models affect the prediction of ecological flows. We applied our methodology to the Cahaba River watershed and results indicate that LULC information can significantly impact simulated flow regimes and the structure of aquatic and riparian habitats. View this paper
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Article
Improving GPR Imaging of the Buried Water Utility Infrastructure by Integrating the Multidimensional Nonlinear Data Decomposition Technique into the Edge Detection
Water 2021, 13(21), 3148; https://doi.org/10.3390/w13213148 - 08 Nov 2021
Viewed by 389
Abstract
Although ground-penetrating radar (GPR) is effective to detect shallow-buried objects, it still needs more effort for the application to investigate a buried water utility infrastructure. Edge detection is a well-known image processing technique that may improve the resolution of GPR images. In this [...] Read more.
Although ground-penetrating radar (GPR) is effective to detect shallow-buried objects, it still needs more effort for the application to investigate a buried water utility infrastructure. Edge detection is a well-known image processing technique that may improve the resolution of GPR images. In this study, we briefly review the theory of edge detection and discuss several popular edge detectors as examples, and then apply an enhanced edge detecting method to GPR data processing. This method integrates the multidimensional ensemble empirical mode decomposition (MDEEMD) algorithm into standard edge detecting filters. MDEEMD is implemented mainly for data reconstruction to increase the signal-to-noise ratio before edge detecting. A quantitative marginal spectrum analysis is employed to support the data reconstruction and facilitate the final data interpretation. The results of the numerical model study followed by a field example suggest that the MDEEMD edge detector is a competent method for processing and interpreting GPR data of a buried hot spring well, which cannot be efficiently handled by conventional techniques. Moreover, the proposed method should be readily considered a vital tool for processing other kinds of buried water utility infrastructures. Full article
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Article
The Impact of the Changes in Climate, Land Use and Direct Human Activity on the Discharge in Qingshui River Basin, China
Water 2021, 13(21), 3147; https://doi.org/10.3390/w13213147 - 08 Nov 2021
Viewed by 420
Abstract
Climate, land use and human activity have an impact on the Qingshui River in Chongli County. The Soil and Water Assessment Tool (SWAT) was used to separately analyze the contributions of climate, land use and direct human activity on the discharge variations. The [...] Read more.
Climate, land use and human activity have an impact on the Qingshui River in Chongli County. The Soil and Water Assessment Tool (SWAT) was used to separately analyze the contributions of climate, land use and direct human activity on the discharge variations. The results indicated that human activity had been the dominant factor for the discharge decrease, while climate and land use change had a positive influence on the discharge increase. The contributions of these three factors were −56.24%, 38.59% and 5.17%, respectively. Moreover, on the seasonal scale, the impact of those factors was consistent with their impact on the annual scale. Human activity was the main factor for discharge decrease in the summer, the contribution accounting for −77.13%. Due to the over-extraction of groundwater for irrigation and use in the mining industry, the discharge showed a decreasing tendency, which has the potential to place stress on sustainable water use in the future. The result of the study may contribute to the optimization of water resource allocation and management. Full article
(This article belongs to the Special Issue Response Mechanism of Non-point Source Nitrogen Output in Farmland)
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Article
Impacts Analysis of Alien Macroinvertebrate Species in the Hydrographic System of a Subalpine Lake on the Italian–Swiss Border
Water 2021, 13(21), 3146; https://doi.org/10.3390/w13213146 - 08 Nov 2021
Viewed by 437
Abstract
The potential invasiveness of alien macroinvertebrate species in the Italian/Swiss hydrographic system of Lake Maggiore (NW Italy) was assessed through the Aquatic Species Invasiveness Screening Kit, a risk assessment tool developed for quantifying the impacts of alien species on the commercial, environmental, and [...] Read more.
The potential invasiveness of alien macroinvertebrate species in the Italian/Swiss hydrographic system of Lake Maggiore (NW Italy) was assessed through the Aquatic Species Invasiveness Screening Kit, a risk assessment tool developed for quantifying the impacts of alien species on the commercial, environmental, and species traits sectors. Data were collected using the databases provided by two regional environmental agencies in northern Italy (Lombardy and Piedmont regions) and by the governmental monitoring program of Switzerland, which were integrated with a systematic literature search on Google scholar and ISI Web of Science. In the assessment area, 16 macroinvertebrate invasive alien species were reported: nine mollusks, four decapods, and three amphipods. The species assessment indicated seven species with a high level of invasiveness: Procambarus clarkii, Faxonius limosus (formerly, Orconectes limosus) and Pacifastacus leniusculus, Dreissena polymorpha, Corbicula fluminea, Sinanodonta woodiana, and Pseudosuccinea columella. The results allow invasive species managers to understand which species to focus their monitoring on in the near future in order to track IAS movements and limit their spread within the hydrographic system and to provide the identification and refinement of concerted bilateral strategies aimed at limiting the impacts of these species. They also account for the implications of future climate change on the invasion potential of each species. Full article
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Article
Spatiotemporal Variations of Reference Evapotranspiration and Its Determining Climatic Factors in the Taihang Mountains, China
Water 2021, 13(21), 3145; https://doi.org/10.3390/w13213145 - 08 Nov 2021
Viewed by 273
Abstract
Reference evapotranspiration (ETo) is an effective measure of atmospheric water demand of the land surface. In-depth investigations of the relationship between ETo and primary climatic factors can facilitate the adaptable agriculture and optimize water management, especially in the ecologically fragile Taihang Mountains (THM). [...] Read more.
Reference evapotranspiration (ETo) is an effective measure of atmospheric water demand of the land surface. In-depth investigations of the relationship between ETo and primary climatic factors can facilitate the adaptable agriculture and optimize water management, especially in the ecologically fragile Taihang Mountains (THM). This work assessed the spatiotemporal dynamics of ETo and its driving climatic factors from 1973 to 2016 in THM. Results showed: (1) Annual ETo slightly increased during 1973–2016; relative humidity (RH) decreased more slowly, the temperature increased more rapidly, and wind speed (WS) decreased more rapidly at higher elevation than those at lower elevations; (2) two breakpoints occurred in ETo series at 1990 and 1997, and an “evaporation paradox” existed in 1973–1990; (3) ETo at higher elevations had greater sensitivity to changes in RH and lower sensitivity to changes in Tmax and WS. Sensitivity of ETo to minimum air temperature (Tmin) at middle elevations was lowest among three elevation bands; (4) RH and sunshine duration (SD) were the dominant climatic factors of ETo for most periods and stations. This study helps us understand the impact of climate change on ETo in mountainous areas and confirms reference evapotranspiration in high-elevation areas is particularly sensitive to climate change. Full article
(This article belongs to the Section Hydrology)
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Article
Estimating Regional Evapotranspiration Using a Satellite-Based Wind Speed Avoiding Priestley–Taylor Approach
Water 2021, 13(21), 3144; https://doi.org/10.3390/w13213144 - 08 Nov 2021
Viewed by 342
Abstract
Wind speed (u) is a significant constraint in the evapotranspiration modeling over the highly heterogeneous regional surface due to its high temporal-spatial variation. In this study, a satellite-based Wind Speed Avoiding Priestley–Taylor (WAPT) algorithm was proposed to estimate the regional actual [...] Read more.
Wind speed (u) is a significant constraint in the evapotranspiration modeling over the highly heterogeneous regional surface due to its high temporal-spatial variation. In this study, a satellite-based Wind Speed Avoiding Priestley–Taylor (WAPT) algorithm was proposed to estimate the regional actual evapotranspiration by employing a u-independent theoretical trapezoidal space to determine the pixel Priestley–Taylor (PT) parameter Φ. The WAPT model was comprehensively evaluated with hydro-meteorological observations in the arid Heihe River Basin in northwestern China. The results show that the WAPT model can provide reliable latent heat flux estimations with the root-mean-square error (RMSE) of 46.0 W/m2 across 2013–2018 for 5 long-term observation stations and the RMSE of 49.6 W/m2 in the growing season in 2012 for 21 stations with intensive observations. The estimation by WAPT has a higher precision in the vegetation growing season than in the non-growing season. The estimation by WAPT has a closer agreement with the ground observations for vegetation-covered surfaces (e.g., corn and wetland) than that for dry sites (e.g., Gobi, desert, and desert steppe). Full article
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Article
Metal Pollution Assessment of Surface Water in the Emission Field of the Slovinky Tailing Impoundment (Slovakia)
Water 2021, 13(21), 3143; https://doi.org/10.3390/w13213143 - 08 Nov 2021
Viewed by 326
Abstract
The focus of this work is on the evaluation of selected water quality indicators as per the applicable regulations, taking into account European and national legislation and the evaluation of the risk of contamination of surface waters with toxic elements using the contamination [...] Read more.
The focus of this work is on the evaluation of selected water quality indicators as per the applicable regulations, taking into account European and national legislation and the evaluation of the risk of contamination of surface waters with toxic elements using the contamination factor (Cfi) and the degree of pollution (Cd). The studied area of Slovinky is an important ore region, with rich deposits of copper and silver ores that have been mined for centuries. One of the most important remnants of mining activities in this area is the Slovinky tailing impoundment. The sludge pond area has an area of 15 ha, and the height of the dam is 113 m above sea level, which makes the sludge pond one of the tallest water structures in Slovakia. The Slovinský creek was monitored in the years 2010, 2011, and 2019 at five sampling points, which were selected to map the entire length of the water flow from the source to the estuary to the river Hornád. Risk elements (As, Cu, Cd, and Fe) and physicochemical parameters (such as temperature, dissolved oxygen concentration, conductivity, resistivity, salinity, total dissolved solids, NaCl, redox potential, and pH) were included in this study and evaluated according to applicable regulations, taking into account European legislation (Act No. 269/2010 Coll., guideline value WHO 2011). The results of the experimental studies showed that the highest values of As and Cu were measured at the site where drainage waters from the Slovinky tailing impoundment and mining water of the Alžbeta shaft flow into the creek. The concentration of As exceeded the limit value by up to 31 times and the concentration of Cu 16.8–134.5 times. At the same time, the highest values of conductivity, salinity, total dissolved solids, and NaCl were found, and there was no acidification of water at the site that had the highest pollution. Water contamination was assessed based on Cfi and Cd; our findings showed that the surface water from the site of contamination, along the entire length of the stream, was very highly contaminated with risk elements in the order of As > Fe > Cu, and the level of contamination decreased with distance from the site of contamination. Our research shows that seepage of toxic substances from sludge ponds and abandoned mines has caused the requirements for the quality of surface water of the Slovinský creek not to be met. In connection with mining activities, surface streams act as a transport medium through which other components of the environment can be polluted. Full article
(This article belongs to the Topic Emerging Solutions for Water, Sanitation and Hygiene)
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Article
Determining the Optimal Biomass of Macrophytes during the Ecological Restoration Process of Eutrophic Shallow Lakes
Water 2021, 13(21), 3142; https://doi.org/10.3390/w13213142 - 08 Nov 2021
Viewed by 350
Abstract
Many studies have shown that macrophytes play a significant role in controlling eutrophication; however, only a few of these are based on macrophyte biomass. Based on the growth characteristic of macrophytes, we propose an approach for the assessment of the optimal biomass of [...] Read more.
Many studies have shown that macrophytes play a significant role in controlling eutrophication; however, only a few of these are based on macrophyte biomass. Based on the growth characteristic of macrophytes, we propose an approach for the assessment of the optimal biomass of macrophytes in the decay and growth periods in Lake Datong (a shallow lake), using a lake ecological model. The results showed that the pollution load of the lake should be reduced by 50% while conforming to the Environmental Quality Standards for Surface Water (EQSSW) Class Ⅲ. In contrast, with an increase in the pollution load of 5%, the results indicate that the lake may deteriorate to a turbid state over the next few years. The macrophyte biomass should be harvested during the decay period, when 80% biomass is beneficial to the water quality of the eutrophic shallow lake. Based on macrophyte simulation from 2020–2024, the wet biomass of macrophytes should be controlled at 5.5 kg/m2. The current macrophyte biomass in Lake Datong is four-fold higher than the simulated optimal biomass. This study provides a reference for the adequate ecological restoration of the lake and its subsequent maintenance, as well as scientific support for improving the comprehensive evaluation standard of healthy lakes and the theoretical basis of lake ecological restoration. Full article
(This article belongs to the Special Issue Lake Ecology and Restoration)
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Article
Hydrodynamic Evaluation of Five Influent Distribution Systems in a Cylindrical UASB Reactor Using CFD Simulations
Water 2021, 13(21), 3141; https://doi.org/10.3390/w13213141 - 08 Nov 2021
Viewed by 324
Abstract
UASB reactors are a promising option for environmentally friendly wastewater treatment due to their reduced carbon footprint and their capacity to treat a variety of wastewater strengths, among other recognized advantages over alternative wastewater treatment systems. The Influent Distribution System (IDS) is a [...] Read more.
UASB reactors are a promising option for environmentally friendly wastewater treatment due to their reduced carbon footprint and their capacity to treat a variety of wastewater strengths, among other recognized advantages over alternative wastewater treatment systems. The Influent Distribution System (IDS) is a critical structure for generating granules in a UASB reactor since it provides the required flow hydrodynamics for their formation. Thus, the objective of this study was to evaluate and compare the efficiency of five IDS configurations to generate ideal granulation conditions using Computational Fluid Dynamics (CFD) simulations. The IDS configurations were as follows: (C1) single radial inflow, (C2) upward axial inflow, (C3) downward distributed axial inflow, and two novel configurations in the form of (C4) double opposite radial inflow and (C5) downward tangential inflow. The hydrodynamic response of configuration C1 was validated in a physical model with dynamic Froude similitude. The granulation measurement was velocity-based in the reactor reaction zone using steady-state CFD simulations. The novel IDS configuration C4 was the one that resulted in the highest granulation volume, with up to 45.5% of the potential granulation volume of the UASB reactor, in contrast to the IDS C2 that obtained the lowest granulation with only 10.8%. Results confirm that the IDS directly impacts the hydrodynamics of the reactor and that model-based design can be used to ascertain IDS configurations that better promote granulation in UASB reactors. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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Article
Unveiling Economic Co-Benefits of Virtual Water Trades: An Empirical Analysis on China’s JingJinJi Megalopolis
Water 2021, 13(21), 3140; https://doi.org/10.3390/w13213140 - 08 Nov 2021
Viewed by 327
Abstract
The development of metropolitan cities inevitably relies on natural resources beyond their boundary through trade of materials and products, particularly within the same urban agglomeration. Meanwhile trade facilitates the optimization of resource allocations under scarcity, among cities and sectors, and therefore generates economic [...] Read more.
The development of metropolitan cities inevitably relies on natural resources beyond their boundary through trade of materials and products, particularly within the same urban agglomeration. Meanwhile trade facilitates the optimization of resource allocations under scarcity, among cities and sectors, and therefore generates economic gains. This study constructs an economic evaluation model combining a Multi-Regional Input-Output model and a Data Envelopment Analysis (DEA) to quantify the economic impacts of virtual water trades among the 13 cities in the JingJinJi region (China national capital area), one of the most water-scarce regions in China. We found that the total virtual water trade among the 13 cities amounted to 927 million m3 in 2012, among which agricultural sectors contributed 90% while the industrial sector and service sector together made up the remaining 10%. While Beijing and Tianjin are the main virtual water importers, importing respectively 300.48 and 226.92 million m3 in 2012, Shijiazhuang was the largest virtual water exporter, exporting 173.29 million m3 virtual water in the same year. Due to their more advanced economic conditions, Beijing and Tianjin also have the highest shadow prices of water, at respectively 912.21 and 831.86 CNY per m3, compared to a range of 79.31 to 263.03 CNY per m3 in cities in Hebei. Virtual water flows from cities in Hebei to Beijing and Tianjin thus generate economic gains. It is estimated that virtual water trades in the JingJinJi region have generated a net economic gain of 403.62 billion CNY in 2012, particularly owing to trades of agricultural products from Shijiazhuang to Beijing and Tianjin. Full article
(This article belongs to the Section Water Use and Scarcity)
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Article
Observation and Analysis of Water Temperature in Ice-Covered Shallow Lake: Case Study in Qinghuahu Lake
Water 2021, 13(21), 3139; https://doi.org/10.3390/w13213139 - 08 Nov 2021
Viewed by 302
Abstract
Water temperature serves as a key environmental factor of lakes and the most basic parameter for analyzing the thermal conditions of a water body. Based on the observation and analysis of the water temperature of Qinghuahu Lake in the Heilongjiang Province of China, [...] Read more.
Water temperature serves as a key environmental factor of lakes and the most basic parameter for analyzing the thermal conditions of a water body. Based on the observation and analysis of the water temperature of Qinghuahu Lake in the Heilongjiang Province of China, this paper analyzed the variation trend of the heat flux, effective thermal diffusivity of the icebound water, and revealed the temporal and spatial variation law of the water temperature and the transfer law beneath the ice on a shallow lake in a cold region. The results suggested a noticeable difference existing in the distribution of water temperature beneath the ice during different periods of ice coverage. During the third period, the water temperature vertically comprised three discrete layers, each of which remained unchanged in thickness despite the alternation of day and night. Sediment–water heat flux and water–ice heat flux both remained positive values throughout the freezing duration, averaging about 3.8–4.1 W/m2 and 9.8–10.3 W/m2, respectively. The calculated thermal diffusivity in late winter was larger than molecular, and the time-averaged values increased first and then decreased with water depth, reaching a maximum at a relative depth of 0.5. This research is expected to provide a reference for studies on the water environment of icebound shallow lakes or ponds in cold regions. Full article
(This article belongs to the Section Hydrology)
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Article
Impacts of Climate Change on the Precipitation and Streamflow Regimes in Equatorial Regions: Guayas River Basin
Water 2021, 13(21), 3138; https://doi.org/10.3390/w13213138 - 08 Nov 2021
Viewed by 435
Abstract
The effects of climate change projected for 2050 to 2079 relative to the 1968–2014 reference period were evaluated using 39 CMIP5 models under the RCP8.5 emissions scenario in the Guayas River basin. The monthly normalized precipitation index (SPI) was used in this study [...] Read more.
The effects of climate change projected for 2050 to 2079 relative to the 1968–2014 reference period were evaluated using 39 CMIP5 models under the RCP8.5 emissions scenario in the Guayas River basin. The monthly normalized precipitation index (SPI) was used in this study to assess the impact of climate change for wet events and droughts from a meteorological perspective. The GR2M model was used to project changes in the streamflow of the Daule River. The climate projection was based on the four rigorously selected models to represent the climate of the study area. On average, an increase in temperature (~2 °C) and precipitation (~6%) is expected. A 7% increase in precipitation would result in a 10% increase in streamflow for flood periods, while an 8% decrease in precipitation could result in approximately a 60% reduction in flow for dry periods. The analysis of droughts shows that they will be more frequent and prolonged in the highlands (Andes) and the middle part of the basin. In the future, wet periods will be less frequent but of greater duration and intensity on the Ecuadorian coast. These results point to future problems such as water deficit in the dry season but also increased streamflow for floods during the wet season. This information should be taken into account in designing strategies for adaptation to climate change. Full article
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Article
A Strontium and Hydro-Geochemical Perspective on Human Impacted Tributary of the Mekong River Basin: Sources Identification, Fluxes, and CO2 Consumption
Water 2021, 13(21), 3137; https://doi.org/10.3390/w13213137 - 08 Nov 2021
Viewed by 776
Abstract
As the largest and most representative tributary of the Mekong River, the Mun River Basin (MRB) provides critical understanding of regional hydro-geochemical features and rock weathering processes on a basin scale. The present study measured strontium (Sr) isotopes with hydro-geochemistry data of 56 [...] Read more.
As the largest and most representative tributary of the Mekong River, the Mun River Basin (MRB) provides critical understanding of regional hydro-geochemical features and rock weathering processes on a basin scale. The present study measured strontium (Sr) isotopes with hydro-geochemistry data of 56 water samples in detail in the MRB in northeast Thailand. The dissolved Sr contents and 87Sr/86Sr isotopic ratios were reported to be 8.7–344.6 μg/L (average 126.9 μg/L) and 0.7085–0.7281 (average 0.7156), respectively. The concentrations of dissolved Sr in the mainstream slightly decreased from upstream to downstream, while the variation trend of 87Sr/86Sr was on the contrary. Correlation analysis showed that Na+ strongly correlated with Cl (0.995, p < 0.01), while Ca2+ exhibited weak relationships with SO42 (0.356, p < 0.01). Samples of the MRB exhibited lower Mg2+/Na+, Ca2+/Na+, HCO3/Na+ and 1000Sr/Na ratios, and gathered around the end-member of evaporite dissolution, with slight shift to silicate weathering end-member, demonstrating the dominant contribution of evaporite dissolution and silicate weathering on dissolved loads. Comparing with data of major world rivers from previous research, our results remained consistency with rivers draining through similar geological conditions. The dissolved Sr flux to the adjacent Mekong River was estimated to be 20.7 tons/year. In accordance with the forward model, silicate weathering rate and CO2 consumption rate during dry season were calculated to be 0.73 tons/km2/year and 1.94 × 104 mol/km2/year, and may get underestimated due to intense water consumption by extensive agricultural activities. The superimposed effect of anthropogenic impacts on the water environment could enhance chemical weathering, and thus should be taken into account in regional ion cycles and carbon budgets. These findings highlight the coupling analysis of Sr isotopes and hydro-geochemistry in Earth surface processes and provide basic investigation for sustainable regional water treatment mechanisms in the pan basin of the Mekong River. Full article
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Article
Electrochemical Recovery to Overcome Direct Osmosis Concentrate-Bearing Lead: Optimization of Treatment Process via RSM-CCD
Water 2021, 13(21), 3136; https://doi.org/10.3390/w13213136 - 08 Nov 2021
Viewed by 351
Abstract
The use of electrochemistry is a promising approach for the treatment of direct osmosis concentrate that contains a high concentration of organic pollutants and has high osmotic pressure, to achieve the safe discharge of effluent. This work addresses, for the first time, this [...] Read more.
The use of electrochemistry is a promising approach for the treatment of direct osmosis concentrate that contains a high concentration of organic pollutants and has high osmotic pressure, to achieve the safe discharge of effluent. This work addresses, for the first time, this major environmental challenge using perforated aluminum electrodes mounted in an electrocoagulation–flotation cell (PA-ECF). The design of the experiments, the modeling, and the optimization of the PA-ECF conditions for the treatment of DO concentrate rich in Pb were explored using a central composite design (CCD) under response surface methodology (RSM). Therefore, the CCD-RSM was employed to optimize and study the effect of the independent variables, namely electrolysis time (5.85 min to 116.15 min) and current intensity (0.09 A to 2.91 A) on Pb removal. Optimal values of the process parameters were determined as an electrolysis time of 77.65 min and a current intensity of 0.9 A. In addition to Pb removal (97.8%), energy consumption, electrode mass-consumed material, and operating cost were estimated as 0.0025 kWh/m3, 0.217 kg Al/m3, and 0.423 USD/m3, respectively. In addition, it was found that DO concentrate obtained from metallurgical wastewater can be recovered through PA-ECF (almost 94% Pb removal). This work demonstrated that the PA-ECF technique could became a viable process applicable in the treatment of DO concentrate containing Pb-rich for reuse. Full article
(This article belongs to the Special Issue Application of Electrochemistry in Wastewater Treatment)
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Article
Numerical Canal Seepage Loss Evaluation for Different Lining and Crack Techniques in Arid and Semi-Arid Regions: A Case Study of the River Nile, Egypt
Water 2021, 13(21), 3135; https://doi.org/10.3390/w13213135 - 07 Nov 2021
Viewed by 495
Abstract
Owing to the potential negative impacts of climatic changes and the grand Ethiopian renaissance dam, water scarcity has become an urgent issue. Therefore, the Egyptian Ministry of Water Resources and Irrigation has started a national project of the lining and rehabilitation of canals, [...] Read more.
Owing to the potential negative impacts of climatic changes and the grand Ethiopian renaissance dam, water scarcity has become an urgent issue. Therefore, the Egyptian Ministry of Water Resources and Irrigation has started a national project of the lining and rehabilitation of canals, to reduce seepage losses and for efficient water resource management. This study presents a new approach for assessing three different lining and crack techniques for the Ismailia canal, the largest end of the river Nile, Egypt. A 2-D steady state seep/w numerical model was developed for the Ismailia canal section, in the stretch at 28.00–49.00 km. The amount of seepage was significantly dependent on the hydraulic characteristics of the liner material. The extraction from aquifers via wells also had a considerable impact on the seepage rate from the unlined canals; however, a lesser effect was present in the case of lined canals. The concrete liner revealed the highest efficiency, followed by the geomembrane liner, and then the bentonite liner; with almost 99%, 96%, and 54%, respectively, without extraction, and decreasing by 4% for bentonite and geomembrane liners during extraction; however, the concrete lining efficiency did not change considerably. Nevertheless, the efficiency dramatically decreased to 25%, regardless of the lining technique, in the case of deterioration of the liner material. The double effect of both deterioration of the liner material and extraction from the aquifer showed a 16% efficiency, irrespective of the utilized lining technique. Full article
(This article belongs to the Special Issue Assessment and Management of Flood Risk in Urban Areas)
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Article
The Holocene History of the Diatom Community in a Small Water Body on Shemya Island (Aleutian Arc, USA): The Influence of Global and Local Environmental Changes
Water 2021, 13(21), 3134; https://doi.org/10.3390/w13213134 - 07 Nov 2021
Viewed by 592
Abstract
A diatom analysis of a peat deposit from Shemya Island (Aleutian Arc, USA) is performed, and the dynamics of the diatom community are described. According to the radiocarbon dating, the formation of the deposit began 9300 cal. years BP. Principal component analysis made [...] Read more.
A diatom analysis of a peat deposit from Shemya Island (Aleutian Arc, USA) is performed, and the dynamics of the diatom community are described. According to the radiocarbon dating, the formation of the deposit began 9300 cal. years BP. Principal component analysis made it possible to relate the dynamics of the diatom community to certain environmental conditions and the factors that influenced the coastal ecosystems during its formation. The following factors (predictors) were considered: the influence of age, zoo- and anthropogenic effects, and changes in climatic conditions. Sea level change was the main driver of the diatom community in the studied water body having a continuous direct and indirect influence on the studied small water body, i.e., by bird colony formation and more humid and coastal conditions. Since 3000–2000 cal. years BP, the anthropogenic factor (hunting depression of the bird colony) also became significant. During the whole water body lifetime and following peat formation, the diatom community was influenced by groups of factors: global factors (e.g., sea level rise) caused gradual change of local factors, which resulted in smooth shifts in community. In contrast, local factor influence (bird colony rise and fall due to human activity) caused abrupt and transient shifts. We can hypothesize that the relatively stable global environmental conditions in the Late Holocene were an auspicious background to see abrupt changes due to influence of the zoogenic and anthropogenic factors. We believe that further works on the material from other islands will make it possible to form a general picture of changes in the diatom communities in the Holocene and interpret it in connection with climatic changes in the region. Full article
(This article belongs to the Special Issue Species Richness and Diversity of Aquatic Ecosystems)
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Article
Addressing Spatial Heterogeneity in the Discrete Generalized Nash Model for Flood Routing
Water 2021, 13(21), 3133; https://doi.org/10.3390/w13213133 - 07 Nov 2021
Viewed by 434
Abstract
River flood routing is one of the key components of hydrologic modeling and the topographic heterogeneity of rivers has great effects on it. It is beneficial to take into consideration such spatial heterogeneity, especially for hydrologic routing models. The discrete generalized Nash model [...] Read more.
River flood routing is one of the key components of hydrologic modeling and the topographic heterogeneity of rivers has great effects on it. It is beneficial to take into consideration such spatial heterogeneity, especially for hydrologic routing models. The discrete generalized Nash model (DGNM) based on the Nash cascade model has the potential to address spatial heterogeneity by replacing the equal linear reservoirs into unequal ones. However, it seems impossible to obtain the solution of this complex high order differential equation directly. Alternatively, the strict mathematical derivation is combined with the deeper conceptual interpretation of the DGNM to obtain the heterogeneous DGNM (HDGNM). In this work, the HDGNM is explicitly expressed as a linear combination of the inflows and outflows, whose weight coefficients are calculated by the heterogeneous S curve. Parameters in HDGNM can be obtained in two different ways: optimization by intelligent algorithm or estimation based on physical characteristics, thus available to perform well in both gauged and ungauged basins. The HDGNM expands the application scope, and becomes more applicable, especially in river reaches where the river slopes and cross-sections change greatly. Moreover, most traditional routing models are lumped, whereas the HDGNM can be developed to be semidistributed. The middle Hanjiang River in China is selected as a case study to test the model performance. The results show that the HDGNM outperforms the DGNM in terms of model efficiency and smaller relative errors and can be used also for ungauged basins. Full article
(This article belongs to the Section Hydrology)
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Sediment Transport Dynamism in the Confluence Area of Two Rivers Transporting Mainly Suspended Sediment Based on Sentinel-2 Satellite Images
Water 2021, 13(21), 3132; https://doi.org/10.3390/w13213132 - 07 Nov 2021
Viewed by 420
Abstract
Downstream of the confluence of rivers, complex hydrological and morphological processes control the flow and sediment transport. This study aimed to analyze the spatio-temporal dynamics of suspended sediment in the confluence area of the Tisza and its main tributary Maros River using Sentinel-2 [...] Read more.
Downstream of the confluence of rivers, complex hydrological and morphological processes control the flow and sediment transport. This study aimed to analyze the spatio-temporal dynamics of suspended sediment in the confluence area of the Tisza and its main tributary Maros River using Sentinel-2 images and to reveal the correlation between the hydrological parameters and the mixing process through a relatively long period (2015–2021). The surficial suspended sediment dynamism was analyzed by applying K-means unsupervised classification algorithm on 143 images. The percentages of the Tisza (TW) and Maros (MW) waters and their mixture (MIX) were calculated and compared with the hydrological parameters in both rivers. The main results revealed that the areal, lateral, and longitudinal extensions of TW and MIX have a better correlation with the hydrological parameters than the MW. The Pearson correlation matrix revealed that the discharge ratio between the rivers controls the mixing process significantly. Altogether, 11 mixing patterns were identified in the confluence area throughout the studied period. The TW usually dominates the confluence in November and January, MW in June and July, and MIX in August and September. Predictive equations for the areal distribution of the three classes were derived to support future water sampling in the confluence area. Full article
(This article belongs to the Section Water Erosion and Sediment Transport)
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Article
Instant Flood Risk Modelling (Inform) Tool for Co-Design of Flood Risk Management Strategies with Stakeholders in Can Tho City, Vietnam
Water 2021, 13(21), 3131; https://doi.org/10.3390/w13213131 - 06 Nov 2021
Viewed by 382
Abstract
Flood risk reduction strategies play an important role in flood risk management (FRM) and these strategies are being co-designed with the engagement of the stakeholder through multiple consultations and co-designing sessions. Effective participation of stakeholders in interactive work sessions requires fast and accurate [...] Read more.
Flood risk reduction strategies play an important role in flood risk management (FRM) and these strategies are being co-designed with the engagement of the stakeholder through multiple consultations and co-designing sessions. Effective participation of stakeholders in interactive work sessions requires fast and accurate modeling systems with a user-friendly interface, which can simulate the impact due to various flood reduction measures selected by the stakeholders and also generate outputs that can be understood by all stakeholders, especially those who are not FRM specialists. Presenting an easy-to-understand tool with easy inputs and outputs for a variety of stakeholders and at the same time providing reliable and accurate results for a range of scenarios and interventions is a challenge. Seven requirements that are essential for a user-friendly flood risk tool were used to develop an instant flood risk modeling tool. This paper presents a web-based hydraulic tool, i.e., instant flood risk model (Inform), to support FRM in the urban center of Can Tho city (Ninh Kieu district), Mekong Delta, Vietnam. Inform was developed based on (i) a simplified 1D model for the entire Mekong Delta; and (ii) flood hazard and damage maps, and estimated flood damage for Ninh Kieu district in Can Tho city obtained directly from the 1D/2D coupled model for Ninh Kieu district. Inform rapidly generates flood levels, flood hazard and damage maps, estimated damages. Pilot testing with experts confirmed that Inform qualifies as a reliable co-design tool for developing FRM strategies as it features an inbuilt input library, comprises flexible options, easy to use, produces quick results and has a user-friendly interface. With the help of an interactive web-based tool such as Inform presented here, it is possible to co-design FRM strategies for Can Tho or any other city that is subject to flood risk. Full article
(This article belongs to the Special Issue Integrated Approaches to Manage Floods in Urban Environments)
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Article
Groundwater Level Prediction Using a Multiple Objective Genetic Algorithm-Grey Relational Analysis Based Weighted Ensemble of ANFIS Models
Water 2021, 13(21), 3130; https://doi.org/10.3390/w13213130 - 06 Nov 2021
Viewed by 567
Abstract
Predicting groundwater levels is critical for ensuring sustainable use of an aquifer’s limited groundwater reserves and developing a useful groundwater abstraction management strategy. The purpose of this study was to assess the predictive accuracy and estimation capability of various models based on the [...] Read more.
Predicting groundwater levels is critical for ensuring sustainable use of an aquifer’s limited groundwater reserves and developing a useful groundwater abstraction management strategy. The purpose of this study was to assess the predictive accuracy and estimation capability of various models based on the Adaptive Neuro Fuzzy Inference System (ANFIS). These models included Differential Evolution-ANFIS (DE-ANFIS), Particle Swarm Optimization-ANFIS (PSO-ANFIS), and traditional Hybrid Algorithm tuned ANFIS (HA-ANFIS) for the one- and multi-week forward forecast of groundwater levels at three observation wells. Model-independent partial autocorrelation functions followed by frequentist lasso regression-based feature selection approaches were used to recognize appropriate input variables for the prediction models. The performances of the ANFIS models were evaluated using various statistical performance evaluation indexes. The results revealed that the optimized ANFIS models performed equally well in predicting one-week-ahead groundwater levels at the observation wells when a set of various performance evaluation indexes were used. For improving prediction accuracy, a weighted-average ensemble of ANFIS models was proposed, in which weights for the individual ANFIS models were calculated using a Multiple Objective Genetic Algorithm (MOGA). The MOGA accounts for a set of benefits (higher values indicate better model performance) and cost (smaller values indicate better model performance) performance indexes calculated on the test dataset. Grey relational analysis was used to select the best solution from a set of feasible solutions produced by a MOGA. A MOGA-based individual model ranking revealed the superiority of DE-ANFIS (weight = 0.827), HA-ANFIS (weight = 0.524), and HA-ANFIS (weight = 0.697) at observation wells GT8194046, GT8194048, and GT8194049, respectively. Shannon’s entropy-based decision theory was utilized to rank the ensemble and individual ANFIS models using a set of performance indexes. The ranking result indicated that the ensemble model outperformed all individual models at all observation wells (ranking value = 0.987, 0.985, and 0.995 at observation wells GT8194046, GT8194048, and GT8194049, respectively). The worst performers were PSO-ANFIS (ranking value = 0.845), PSO-ANFIS (ranking value = 0.819), and DE-ANFIS (ranking value = 0.900) at observation wells GT8194046, GT8194048, and GT8194049, respectively. The generalization capability of the proposed ensemble modelling approach was evaluated for forecasting 2-, 4-, 6-, and 8-weeks ahead groundwater levels using data from GT8194046. The evaluation results confirmed the useability of the ensemble modelling for forecasting groundwater levels at higher forecasting horizons. The study demonstrated that the ensemble approach may be successfully used to predict multi-week-ahead groundwater levels, utilizing previous lagged groundwater levels as inputs. Full article
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Article
Effect of the COVID-19 Pandemic on Residential Water Use Behavior in Japan
Water 2021, 13(21), 3129; https://doi.org/10.3390/w13213129 - 05 Nov 2021
Viewed by 487
Abstract
To investigate the effect of the COVID-19 (coronavirus) pandemic on residential water use behavior in Japan, we conducted a web-based survey of 1310 people throughout Japan in March 2021, one year after the initial spread of coronavirus. The survey was designed to provide [...] Read more.
To investigate the effect of the COVID-19 (coronavirus) pandemic on residential water use behavior in Japan, we conducted a web-based survey of 1310 people throughout Japan in March 2021, one year after the initial spread of coronavirus. The survey was designed to provide an average picture of Japan. The survey revealed that the time respondents spent at home increased during the pandemic for both men and women in all age groups by an average of 1 h, an increase of 9%. Changes in water use behavior increased almost in proportion to the increase in time spent at home, except for the frequency of defecation, which was limited to once a day. The amount of time spent in the washroom increased by 13%, an increase of more than 1.4 times the increase in the amount of time spent at home. The additional 40% increase could be considered an effect of the awareness of disease prevention. The coronavirus pandemic is expected to end in the near future. In Japan, the pandemic has led to a strong push for the reform of work styles. Therefore, even in a post-coronavirus-pandemic society, changes in work styles may normalize the increased time spent at home and the proportional increase in water use. However, because the change in water use behavior caused by quarantine awareness is a result of the fear of coronavirus infection, it is possible that water use will gradually return to pre-pandemic levels once the source of the fear is removed. To reflect the changes in water use behavior in the design of facilities in the post-coronavirus-pandemic society, it is necessary to continue this survey even once the pandemic has ended. Full article
(This article belongs to the Special Issue Assessment of Water Quality)
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Article
Stochastic Modeling for Estimating Real-Time Inundation Depths at Roadside IoT Sensors Using the ANN-Derived Model
Water 2021, 13(21), 3128; https://doi.org/10.3390/w13213128 - 05 Nov 2021
Viewed by 285
Abstract
This paper aims to develop a stochastic model (SM_EID_IOT) for estimating the inundation depths and associated 95% confidence intervals at the specific locations of the roadside water-level gauges, i.e., Internet of Things (IoT) sensors under the observed water levels/rainfalls and the precipitation forecasts [...] Read more.
This paper aims to develop a stochastic model (SM_EID_IOT) for estimating the inundation depths and associated 95% confidence intervals at the specific locations of the roadside water-level gauges, i.e., Internet of Things (IoT) sensors under the observed water levels/rainfalls and the precipitation forecasts given. The proposed SM_EID_IOT model is an ANN-derived one, a modified artificial neural network model (i.e., the ANN_GA-SA_MTF) in which the associated ANN weights are calibrated via a modified genetic algorithm with a variety of transfer functions considered. To enhance the reliability and accuracy of the proposed SM_EID_IOT model in the estimations of the inundation depths at the IoT sensors, a great number of the rainfall induced flood events as the training and validation datasets are simulated by the 2D hydraulic dynamic (SOBEK) model with the simulated rain fields via the stochastic generation model for the short-term gridded rainstorms. According to the results of model demonstration, Nankon catchment, located in northern Taiwan, the proposed SM_EID_IOT model can estimate the inundation depths at the various lead times with high reliability in capturing the validation datasets. Moreover, through the integrated real-time error correction method integrated with the proposed SM_EID_IOT model, the resulting corrected inundation-depth estimates exhibit a good agreement with the validated ones in time under an acceptable bias. Full article
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Article
Water Quality Evaluation Method Based on a T-S Fuzzy Neural Network—Application in Water Environment Trend Analysis of Taihu Lake Basin
Water 2021, 13(21), 3127; https://doi.org/10.3390/w13213127 - 05 Nov 2021
Viewed by 333
Abstract
In response to the problems of large computational volume and tedious computational process of fuzzy integrated evaluation, and general neural network models without clear water quality training criteria, this paper organically combines fuzzy rules, affiliation function, and neural network, and proposes a comprehensive [...] Read more.
In response to the problems of large computational volume and tedious computational process of fuzzy integrated evaluation, and general neural network models without clear water quality training criteria, this paper organically combines fuzzy rules, affiliation function, and neural network, and proposes a comprehensive method for the evaluation of water quality based on a T-S fuzzy neural network. On the three water quality monitoring data of six national key monitoring stations in Taihu Lake Basin, three evaluation methods—the one-factor evaluation method, the fuzzy integrated evaluation method, and the T-S fuzzy neural network evaluation method—were used to comprehensively evaluate water environment quality, and the results showed that the T-S fuzzy neural network method has the advantages of convenient calculation, strong applicability, and scientific results. Full article
(This article belongs to the Section Water Quality and Contamination)
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Review
Degradation of Micropollutants and Formation of Oxidation By-Products during the Ozone/Peroxymonosulfate System: A Critical Review
Water 2021, 13(21), 3126; https://doi.org/10.3390/w13213126 - 05 Nov 2021
Viewed by 381
Abstract
The O3/PMS system has appeared as an effective wastewater treatment method because of the simultaneous generation of hydroxyl radicals (OH) and sulfate radicals (SO4•−). Many research achievements have been made on the degradation of micropollutants and [...] Read more.
The O3/PMS system has appeared as an effective wastewater treatment method because of the simultaneous generation of hydroxyl radicals (OH) and sulfate radicals (SO4•−). Many research achievements have been made on the degradation of micropollutants and the reaction mechanism of the O3/PMS system. However, an integral understanding of the O3/PMS system is lacking, which limits the development of safe and effective AOP-based water treatment schemes. Therefore, in this review, the degradation effects, toxicity changes, and reaction mechanisms of various micropollutants in the O3/PMS system are reviewed. The formation of oxidation by-products (OBPs) is an important issue that affects the practical application of O3/PMS systems. The formation mechanism and control methods of OBPs in the O3/PMS system are overviewed. In addition, the influence of different reaction conditions on the O3/PMS system are comprehensively evaluated. Finally, future research needs are proposed based on the limited understanding of O3/PMS systems in the degradation of micropollutants and formation of OBPs. Specifically, the formation rules of several kinds of OBPs during the O3/PMS system are not completely clear yet. Furthermore, pilot-scale research, the operational costs, sustainability, and general feasibility of the O3/PMS system also need to be studied. This review can offer a comprehensive assessment on the O3/PMS system to fill the knowledge gap and provide guidance for the future research and engineering applications of the O3/PMS system. Through this effort, the O3/PMS system can be better developed and turned towards practical applications. Full article
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Article
Community Flood Impacts and Infrastructure: Examining National Flood Impacts Using a High Precision Assessment Tool in the United States
Water 2021, 13(21), 3125; https://doi.org/10.3390/w13213125 - 05 Nov 2021
Viewed by 351
Abstract
Changing environmental conditions are driving worsening flood events, with consequences for counties, cities, towns, and local communities. To understand individual flood risk within this changing climate, local community resiliency and infrastructure impacts must also be considered. Past research has attempted to capture this [...] Read more.
Changing environmental conditions are driving worsening flood events, with consequences for counties, cities, towns, and local communities. To understand individual flood risk within this changing climate, local community resiliency and infrastructure impacts must also be considered. Past research has attempted to capture this but has faced several limitations. This study provides a nation-wide model of community flooding impacts within the United States currently and in 30 years through the use of high-resolution input data (parcel-level), multi-source flood hazard information (four major flood types), multi-return period hazard information (six return periods), operational threshold integration, and future-facing projections. Impacts are quantified here as the level of flooding relative to operational thresholds. This study finds that over the next 30 years, millions of additional properties will be impacted, as aspects of risk are expected to increase for residential properties by 10%, roads by 3%, commercial properties by 7%, critical infrastructure facilities by 6%, and social infrastructure facilities by 9%. Additionally, certain counties and cities persistently display impact patterns. A high-resolution model capturing aspects of flood risk as related to community infrastructure is important for an understanding of overall community risk. Full article
(This article belongs to the Section Water and Climate Change)
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Article
Water Resource Management through Understanding of the Water Balance Components: A Case Study of a Sub-Alpine Shallow Lake
Water 2021, 13(21), 3124; https://doi.org/10.3390/w13213124 - 05 Nov 2021
Viewed by 301
Abstract
Water availability is a crucial factor for the hydrological balance of sub-alpine shallow lakes and for their ecosystems. This is the first study on water balance and water management of Lake Candia, a small sub-alpine, shallow morainic lake. The aims of this paper [...] Read more.
Water availability is a crucial factor for the hydrological balance of sub-alpine shallow lakes and for their ecosystems. This is the first study on water balance and water management of Lake Candia, a small sub-alpine, shallow morainic lake. The aims of this paper are to better understand the link between surface water and groundwater. The analyses carried out included: (i) evaluation of water balance, (ii) identification of trends for each component of water balance, (iii) detection of the presence of a break point or change in the behavior of each component, and (iv) regression analyses of the terms of hydrological balance and their relative importance. The analyses revealed a high variability mainly regarding the groundwater component, and very good correlation between rainfall and volume variation, between rainfall and the water inflow, and between groundwater source and outflow. Volume variation is linked with rainfall, outflow, groundwater source, and surface water inflow. Despite the fact that the groundwater component does not seem to have a great importance relative to direct rainfall on the lake, it is necessary to study the component with careful resource management policies that point toward the protection of the water resource, sustainable uses, and protection of the Lake Candia ecosystem. Full article
(This article belongs to the Topic Water Management in the Era of Climatic Change)
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Article
Environmental Aspects of Historical Ferromanganese Tailings in the Šibenik Bay, Croatia
Water 2021, 13(21), 3123; https://doi.org/10.3390/w13213123 - 05 Nov 2021
Viewed by 313
Abstract
The former manganese ferroalloy plant and the remaining tailings are affecting the quality of the environment in Šibenik Bay, Croatia, even though industrial activities ceased more than 25 years ago. This study has revealed that the main manganese mineral phases present in the [...] Read more.
The former manganese ferroalloy plant and the remaining tailings are affecting the quality of the environment in Šibenik Bay, Croatia, even though industrial activities ceased more than 25 years ago. This study has revealed that the main manganese mineral phases present in the recently collected tailings, as well as in the dust collected on the roof of the plant during the production period, are bustamite and Mn-oxides. The same type of Mn mineral phases was also found in recently collected sediments from Šibenik Bay. Detailed chemical and phase analyses (XRD, BCR sequential analysis, aqua regia and lithium borate fusion) of the dust sample revealed high manganese values (24.1%), while granulometric analysis showed that 50% of the particles are smaller than PM2.5. The influence of the tailings is visible in the sediment, but the concentrations of the potentially toxic elements determined by the sequential BCR analysis are within the legal limits. Some higher values (20.3 g/kg Mn, 595 mg/kg Pb and 494 mg/kg Zn) are detected in the tailings, which are still exposed to weathering and as such should be additionally monitored. On the other hand, this material contains a considerable number of elements that could be considered lucrative (∑ REE up to 700 mg/kg, Mn up to 23 g/kg, Fe up to 37 g/kg and Al up to 25 g/kg), opening the possibility of reuse and recovery. Full article
(This article belongs to the Special Issue Geochemistry of Water and Sediment Ⅱ)
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Article
A Hybrid MPI-OpenMP Parallel Algorithm for the Assessment of the Multifractal Spectrum of River Networks
Water 2021, 13(21), 3122; https://doi.org/10.3390/w13213122 - 05 Nov 2021
Viewed by 302
Abstract
The possibility to create a flood wave in a river network depends on the geometric properties of the river basin. Among the models that try to forecast the Instantaneous Unit Hydrograph (IUH) of rainfall precipitation, the so-called Multifractal Instantaneous Unit Hydrograph (MIUH) rather [...] Read more.
The possibility to create a flood wave in a river network depends on the geometric properties of the river basin. Among the models that try to forecast the Instantaneous Unit Hydrograph (IUH) of rainfall precipitation, the so-called Multifractal Instantaneous Unit Hydrograph (MIUH) rather successfully connects the multifractal properties of the river basin to the observed IUH. Such properties can be assessed through different types of analysis (fixed-size algorithm, correlation integral, fixed-mass algorithm, sandbox algorithm, and so on). The fixed-mass algorithm is the one that produces the most precise estimate of the properties of the multifractal spectrum that are relevant for the MIUH model. However, a disadvantage of this method is that it requires very long computational times to produce the best possible results. In a previous work, we proposed a parallel version of the fixed-mass algorithm, which drastically reduced the computational times almost proportionally to the number of Central Processing Unit (CPU) cores available on the computational machine by using the Message Passing Interface (MPI), which is a standard for distributed memory clusters. In the present work, we further improved the code in order to include the use of the Open Multi-Processing (OpenMP) paradigm to facilitate the execution and improve the computational speed-up on single processor, multi-core workstations, which are much more common than multi-node clusters. Moreover, the assessment of the multifractal spectrum has also been improved through a direct computation method. Currently, to the best of our knowledge, this code represents the state-of-the-art for a fast evaluation of the multifractal properties of a river basin, and it opens up a new scenario for an effective flood forecast in reasonable computational times. Full article
(This article belongs to the Special Issue Advances in River Hydraulic Characterization)
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Article
Evaluation of Paired Watershed Runoff Relationships since Recovery from a Major Hurricane on a Coastal Forest—A Basis for Examining Effects of Pinus palustris Restoration on Water Yield
Water 2021, 13(21), 3121; https://doi.org/10.3390/w13213121 - 05 Nov 2021
Viewed by 493
Abstract
The objective of this study was to test pre-treatment hydrologic calibration relationships between paired headwater watersheds (WS77 (treatment) and WS80 (control)) and explain the difference in flow, compared to earlier published data, using daily rainfall, runoff, and a water table measured during 2011–2019 [...] Read more.
The objective of this study was to test pre-treatment hydrologic calibration relationships between paired headwater watersheds (WS77 (treatment) and WS80 (control)) and explain the difference in flow, compared to earlier published data, using daily rainfall, runoff, and a water table measured during 2011–2019 in the Santee Experimental Forest in coastal South Carolina, USA. Mean monthly runoff difference between WS80 and WS77 of −6.80 mm for 2011–2019, excluding October 2015 with an extreme flow event, did not differ significantly from −8.57 mm (p = 0.27) for the 1969–1978 period or from −3.89 mm for 2004–2011, the post-Hurricane Hugo (1989) recovery period. Both the mean annual runoff coefficient and monthly runoff were non-significantly higher for WS77 than for WS80. The insignificant higher runoff by chance was attributed to WS77’s three times smaller surface storage and higher hypsometrical integral than those of WS80, but not to rainfall. The 2011–2019 geometric mean regression-based monthly runoff calibration relationship, excluding the October 2015 runoff, did not differ from the relationship for the post-Hugo recovery period, indicating complete recovery of the forest stand by 2011. The 2011–2019 pre-treatment regression relationship, which was not affected by periodic prescribed burning on WS77, was significant and predictable, providing a basis for quantifying longleaf pine restoration effects on runoff later in the future. However, the relationship will have to be used cautiously when extrapolating for extremely large flow events that exceed its flow bounds. Full article
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Article
The Reactivity of Polyethylene Microplastics in Water under Low Oxygen Conditions Using Radiation Chemistry
Water 2021, 13(21), 3120; https://doi.org/10.3390/w13213120 - 05 Nov 2021
Viewed by 330
Abstract
Polyethylene (PE) is an intensely utilized polymer, which has consequently led to it becoming a common environmental contaminant. PE and other plastic waste are known to be highly persistent in surface waters; however, chemical and physical changes do take place over time, dependent [...] Read more.
Polyethylene (PE) is an intensely utilized polymer, which has consequently led to it becoming a common environmental contaminant. PE and other plastic waste are known to be highly persistent in surface waters; however, chemical and physical changes do take place over time, dependent mostly on highly variable natural conditions, such as oxygen (O2) availability. Gamma radiation was used to generate reactive oxygen species, namely hydroxyl radicals, in initially aerated aqueous solutions to simulate the natural weathering of microplastics in waters where there are fluctuations and often depletions in dissolved O2. The headspace of the irradiated PE-containing solutions was probed for the formation of degradation products using solid-phase microextraction (SPME) fibers in combination with gas chromatography mass spectrometry (GCMS). The major species detected were n-dodecane, with trace levels of tridecane, 2-dodecanone, and hexadecane, which were believed to be predominately adsorbed in the PE microplastics in excess of their aqueous solubility limits. Surface characterization by Raman spectroscopy and light and dark field microscopy indicated no change in the chemical composition of the irradiated PE microplastics under low O2 to anaerobic conditions. However, morphological changes were observed, indicating radical combination reactions. Full article
(This article belongs to the Section Water Quality and Contamination)
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Article
Long-Term Assessment of Reference Baselines for the Determination of the Crop Water Stress Index in Maize under Mediterranean Conditions
Water 2021, 13(21), 3119; https://doi.org/10.3390/w13213119 - 05 Nov 2021
Viewed by 343
Abstract
Canopy temperature has been proposed as a relevant variable for crop water stress monitoring. Since crop temperature is highly influenced by the prevailing climatic conditions, it is usually normalized with indices such as the crop water stress index (CWSI). The index requires the [...] Read more.
Canopy temperature has been proposed as a relevant variable for crop water stress monitoring. Since crop temperature is highly influenced by the prevailing climatic conditions, it is usually normalized with indices such as the crop water stress index (CWSI). The index requires the use of two baselines that relate canopy temperature under maximum stress and non-water stress conditions with vapor pressure deficit (VPD). These reference baselines are specific to each crop and climatic region. In maize, they have been extensively studied for certain climatic regions but very little is known on their suitability to be used under Mediterranean-type conditions nor their temporal stability, both diurnally and between seasons. Thus, the objective of this work was to determine the reference baselines for maize grown under Mediterranean conditions, as well as its diurnal and long-term stability. An experiment was conducted for 3 years in a maize breeding field, under well-watered and water-stressed irrigation treatments. The determined reference baselines for computing CWSI in maize have shown to be stable in the long term but markedly influenced by the meteorological variations between 10–17 h UTC (Coordinated Universal Time). These results indicate that several reference baselines should be used for CWSI computing throughout the abovementioned time interval. The CWSI values calculated for well-watered and water-stressed maize breeding plots using the reference baselines derived in this study were successfully correlated with other physiological indicators of plant water stress. Full article
(This article belongs to the Special Issue Crop Monitoring Strategies for Precise Irrigation Management)
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