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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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22 pages, 4543 KiB  
Article
Exploring the Role of Reservoir Storage in Enhancing Resilience to Climate Change in Southern Europe
by Alfredo Granados, Alvaro Sordo-Ward, Bolívar Paredes-Beltrán and Luis Garrote
Water 2021, 13(1), 85; https://doi.org/10.3390/w13010085 - 1 Jan 2021
Cited by 20 | Viewed by 3653
Abstract
Recent trends suggest that streamflow discharge is diminishing in many rivers of Southern Europe and that interannual variability is increasing. This threatens to aggravate water scarcity problems that periodically arise in this region, because both effects will deteriorate the performance of reservoirs, decreasing [...] Read more.
Recent trends suggest that streamflow discharge is diminishing in many rivers of Southern Europe and that interannual variability is increasing. This threatens to aggravate water scarcity problems that periodically arise in this region, because both effects will deteriorate the performance of reservoirs, decreasing their reliable yield. Reservoir storage is the key infrastructure to overcome variability and to enhance water availability in semiarid climates. This paper presents an analysis of the role of reservoir storage in preserving water availability under climate change scenarios. The study is focused on 16 major Southern European basins. Potential water availability was calculated in these basins under current condition and for 35 different climatic projections for the period 2070–2100. The results show that the expected reduction of water availability is comparable to the decrease of the mean annual flow in basins with large storage capacity. For basins with small storage, the expected reduction of water availability is larger than the reduction of mean annual flow. Additionally, a sensitivity analysis was carried out by replicating the analysis assuming variable reservoir volumes from 25% to 175% of current storage. The results show that increasing storage capacity attenuates the reduction of water availability and reduces its uncertainty under climate change projections. This feature would allow water managers to develop suitable policies to mitigate the impacts of climate change, thus enhancing the resilience of the system. Full article
(This article belongs to the Special Issue Water Resources Management Models for Policy Assessment)
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27 pages, 5615 KiB  
Article
Assessing Reservoir Performance under Climate Change. When Is It Going to Be Too Late If Current Water Management Is Not Changed?
by Cristián Chadwick, Jorge Gironás, Pilar Barría, Sebastián Vicuña and Francisco Meza
Water 2021, 13(1), 64; https://doi.org/10.3390/w13010064 - 31 Dec 2020
Cited by 21 | Viewed by 5647
Abstract
Climate change is modifying the way we design and operate water infrastructure, including reservoirs. A particular issue is that current infrastructure and reservoir management rules will likely operate under changing conditions different to those used in their design. Thus, there is a big [...] Read more.
Climate change is modifying the way we design and operate water infrastructure, including reservoirs. A particular issue is that current infrastructure and reservoir management rules will likely operate under changing conditions different to those used in their design. Thus, there is a big need to identify the obsolescence of current operation rules under climate change, without compromising the proper treatment of uncertainty. Acknowledging that decision making benefits from the scientific knowledge, mainly when presented in a simple and easy-to-understand manner, such identification—and the corresponding uncertainty—must be clearly described and communicated. This paper presents a methodology to identify, in a simple and useful way, the time when current reservoir operation rules fail under changing climate by properly treating and presenting its aleatory and epistemic uncertainties and showing its deep uncertainty. For this purpose, we use a reliability–resilience–vulnerability framework with a General Circulation Models (GCM) ensemble under the four Representative Concentration Pathways (RCP) scenarios to compare the historical and future long-term reservoir system performances under its current operation rule in the Limarí basin, Chile, as a case study. The results include percentiles that define the uncertainty range, showing that during the 21st century there are significant changes at the time-based reliability by the 2030s, resilience between the 2030s and 2040s, volume-based reliability by the 2080s, and the maximum failure by the 2070s. Overall, this approach allows the identification of the timing of systematic failures in the performance of water systems given a certain performance threshold, which contributes to the planning, prioritization and implementation timing of adaptation alternatives. Full article
(This article belongs to the Special Issue Climate Change Impacts on Water Resources)
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17 pages, 1332 KiB  
Article
Optimization of an Autochthonous Bacterial Consortium Obtained from Beach Sediments for Bioremediation of Petroleum Hydrocarbons
by Rafaela Perdigão, C. Marisa R. Almeida, Filipa Santos, Maria F. Carvalho and Ana P. Mucha
Water 2021, 13(1), 66; https://doi.org/10.3390/w13010066 - 31 Dec 2020
Cited by 23 | Viewed by 4901
Abstract
Oil spill pollution remains a serious concern in marine environments and the development of effective oil bioremediation techniques are vital. This work is aimed at developing an autochthonous hydrocarbon-degrading consortium with bacterial strains with high potential for hydrocarbons degradation, optimizing first the growth [...] Read more.
Oil spill pollution remains a serious concern in marine environments and the development of effective oil bioremediation techniques are vital. This work is aimed at developing an autochthonous hydrocarbon-degrading consortium with bacterial strains with high potential for hydrocarbons degradation, optimizing first the growth conditions for the consortium, and then testing its hydrocarbon-degrading performance in microcosm bioremediation experiments. Bacterial strains, previously isolated from a sediment and cryopreserved in a georeferenced microbial bank, belonged to the genera Pseudomonas, Rhodococcus and Acinetobacter. Microcosms were assembled with natural seawater and petroleum, for testing: natural attenuation (NA); biostimulation (BS) (nutrients addition); bioaugmentation with inoculum pre-grown in petroleum (BA/P) and bioaugmentation with inoculum pre-grown in acetate (BA/A). After 15 days, a clear blending of petroleum with seawater was observed in BS, BA/P and BA/A but not in NA. Acetate was the best substrate for consortium growth. BA/A showed the highest hydrocarbons degradation (66%). All bacterial strains added as inoculum were recovered at the end of the experiment. This study provides an insight into the capacity of autochthonous communities to degrade hydrocarbons and on the use of alternative carbon sources for bacterial biomass growth for the development of bioremediation products to respond to oil spills. Full article
(This article belongs to the Special Issue Biotechnologies for the Environment: Strategies for Containment and Depletion of Pollution in Wastewaters, Air, Soils and Sediments)
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21 pages, 9975 KiB  
Article
Energy Loss in Steep Open Channels with Step-Pools
by Suresh Kumar Thappeta, S. Murty Bhallamudi, Venu Chandra, Peter Fiener and Abul Basar M. Baki
Water 2021, 13(1), 72; https://doi.org/10.3390/w13010072 - 31 Dec 2020
Cited by 10 | Viewed by 4112
Abstract
Three-dimensional numerical simulations were performed for different flow rates and various geometrical parameters of step-pools in steep open channels to gain insight into the occurrence of energy loss and its dependence on the flow structure. For a given channel with step-pools, energy loss [...] Read more.
Three-dimensional numerical simulations were performed for different flow rates and various geometrical parameters of step-pools in steep open channels to gain insight into the occurrence of energy loss and its dependence on the flow structure. For a given channel with step-pools, energy loss varied only marginally with increasing flow rate in the nappe and transition flow regimes, while it increased in the skimming regime. Energy loss is positively correlated with the size of the recirculation zone, velocity in the recirculation zone and the vorticity. For the same flow rate, energy loss increased by 31.6% when the horizontal face inclination increased from 2° to 10°, while it decreased by 58.6% when the vertical face inclination increased from 40° to 70°. In a channel with several step-pools, cumulative energy loss is linearly related to the number of step-pools, for nappe and transition flows. However, it is a nonlinear function for skimming flows. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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12 pages, 936 KiB  
Article
Ecosystem Organic Carbon Stock Estimations in the Sile River, North Eastern Italy
by Alessandro Buosi, Yari Tomio, Abdul-Salam Juhmani and Adriano Sfriso
Water 2021, 13(1), 80; https://doi.org/10.3390/w13010080 - 31 Dec 2020
Cited by 2 | Viewed by 3414
Abstract
River ecosystems are one of the dynamic components of the terrestrial carbon cycle that provide a crucial function in ecosystem processes and high value to ecosystem services. A large amount of carbon is transported from terrestrial to the ocean through river flows. In [...] Read more.
River ecosystems are one of the dynamic components of the terrestrial carbon cycle that provide a crucial function in ecosystem processes and high value to ecosystem services. A large amount of carbon is transported from terrestrial to the ocean through river flows. In order to evaluate the contribution of Sile River ecosystem to the global carbon stock, the river ecosystem Organic Carbon (OC) stock was quantified for sediments and dominant submerged aquatic macrophytes (SAMs) during the two sampling periods at three different stations along the Sile River (North Eastern Italy). The total mean ecosystem OC stock was 95.2 ± 13.8 Mg C ha−1 while those of SAMs ranged from 7.0 to 10.9 Mg C ha−1 which accounted for approx. 10% of the total OC stock. The total aboveground biomass retains approx. 90% of the SAM carbon stock, with a mean of 8.9 ± 1.6 Mg C ha−1. The mean sediment OC stock was 86.6 ± 14.5 Mg C ha−1 with low seasonal variations among the sites. Indeed, various environmental parameters and hydrodynamics appear to affect the accumulation of OC within the river ecosystem. The results highlight the role that freshwater river ecosystems play in the global carbon cycle, which consequently provide a baseline for future river ecosystem monitoring programs. Furthermore, future studies with additional sites and seasonal surveys of the river will enhance our understanding of the effects of global climate change on the river ecosystem and improve the ecosystem services. Full article
(This article belongs to the Special Issue Aquatic Ecosafety: Threats, Disturbances, Environmental Monitors and Bioremediation Actions)
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13 pages, 1516 KiB  
Article
Nano-TiO2 Phototoxicity in Fresh and Seawater: Daphnia magna and Artemia sp. as Proxies
by Ana C. Soler de la Vega, Alberto Cruz-Alcalde, Carmen Sans Mazón, Carlos Barata Martí and M. Silvia Diaz-Cruz
Water 2021, 13(1), 55; https://doi.org/10.3390/w13010055 - 30 Dec 2020
Cited by 12 | Viewed by 3355
Abstract
Nowadays, the industry is quite commonly using nanoparticles of titanium dioxide (nTiO2) especially in sunscreens, due to its higher reflective index in comparison to micron size TiO2. Its high demand causes its widespread environmental occurrence, thus damaging the environment. [...] Read more.
Nowadays, the industry is quite commonly using nanoparticles of titanium dioxide (nTiO2) especially in sunscreens, due to its higher reflective index in comparison to micron size TiO2. Its high demand causes its widespread environmental occurrence, thus damaging the environment. The aquatic ecosystems are the most vulnerable to contamination by nTiO2. Like other engineered nanoparticles, nTiO2 has demonstrated generation of reactive oxygen species (ROS) and reactive halogen species (RHS) in the aquatic environment under UV radiation. This study investigated the toxicity of nTiO2 towards two aquatic indicator organisms, one from freshwater (Daphnia magna) and the other from seawater (Artemia sp.), under simulated solar radiation (SSR). Daphnia magna and Artemia sp. were co-exposed in 16 h SSR and 8 h darkness cycles to different concentrations of nTiO2. The estimated EC50 at 48 h for D. magna was 3.16 mg nTiO2/L, whereas for A. sp. no toxic effects were observed. When we exposed these two organisms simultaneously to 48 h of prolonged SSR using higher nTiO2 concentrations, EC50 values of 7.60 mg/L and 5.59 mg/L nTiO2 for D. magna and A. sp., respectively, were obtained. A complementary bioassay was carried out with A. sp., by exposing this organism to a mixture of nTiO2 and organic UV filters (benzophenone 3 (oxybenzone, BP3), octocrylene (OC), and ethyl 4-aminobenzoate (EtPABA)), and then exposed to SSR. The results suggested that nTiO2 could potentially have negative impacts on these organisms, also this work outlines the different characteristics and interactions that may contribute to the mechanisms of environmental (in salted and freshwater) phototoxicity of nTiO2 and UV radiation, besides their interaction with organic compounds. Full article
(This article belongs to the Section Water Quality and Contamination)
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26 pages, 2061 KiB  
Review
Ecotoxicological Assessment of Microplastics in Freshwater Sources—A Review
by Martina Miloloža, Dajana Kučić Grgić, Tomislav Bolanča, Šime Ukić, Matija Cvetnić, Vesna Ocelić Bulatović, Dionysios D. Dionysiou and Hrvoje Kušić
Water 2021, 13(1), 56; https://doi.org/10.3390/w13010056 - 30 Dec 2020
Cited by 87 | Viewed by 9458
Abstract
High living standards and a comfortable modern way of life are related to an increased usage of various plastic products, yielding eventually the generation of an increased amount of plastic debris in the environment. A special concern is on microplastics (MPs), recently classified [...] Read more.
High living standards and a comfortable modern way of life are related to an increased usage of various plastic products, yielding eventually the generation of an increased amount of plastic debris in the environment. A special concern is on microplastics (MPs), recently classified as contaminants of emerging concern (CECs). This review focuses on MPs’ adverse effects on the environment based on their bioactivity. Hence, the main topic covered is MPs’ ecotoxicity on various aquatic (micro)organisms such as bacteria, algae, daphnids, and fish. The cumulative toxic effects caused by MPs and adsorbed organic/inorganic pollutants are presented and critically discussed. Since MPs’ bioactivity, including ecotoxicity, is strongly influenced by their properties (e.g., types, size, shapes), the most common classification of MPs types present in freshwater are provided, along with their main characteristics. The review includes also the sources of MPs discharge in the environment and the currently available characterization methods for monitoring MPs, including identification and quantification, to obtain a broader insight into the complex problem caused by the presence of MPs in the environment. Full article
(This article belongs to the Section Water Quality and Contamination)
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28 pages, 8959 KiB  
Article
Using 2D HEC-RAS Modeling and Embankment Dam Break Scenario for Assessing the Flood Control Capacity of a Multi-Reservoir System (NE Romania)
by Andrei Urzică, Alin Mihu-Pintilie, Cristian Constantin Stoleriu, Cătălin Ioan Cîmpianu, Elena Huţanu, Claudiu Ionuţ Pricop and Adrian Grozavu
Water 2021, 13(1), 57; https://doi.org/10.3390/w13010057 - 30 Dec 2020
Cited by 38 | Viewed by 9834
Abstract
Using hydraulic modeling techniques (e.g., one-dimensional/two-dimensional (1D/2D) hydraulic modeling, dam break scenarios) for extracting the flood settings is an important aspect of any action plan for dam failure (APDF) and flood mitigation strategy. For example, the flood hydraulic models and dam break scenario [...] Read more.
Using hydraulic modeling techniques (e.g., one-dimensional/two-dimensional (1D/2D) hydraulic modeling, dam break scenarios) for extracting the flood settings is an important aspect of any action plan for dam failure (APDF) and flood mitigation strategy. For example, the flood hydraulic models and dam break scenario generated based on light detection and ranging (LiDAR)-derived digital elevation models (DEMs) and processed in the dedicated geographic information systems (GIS) and hydraulic modeling software (e.g., HEC-RAS—Hydrologic Engineering Center River Analysis System, developed by USACE HEC, Davis, CA, USA) can improve the flood hazard maps in case of potentially embankment dam failure. In this study, we develop a small-scale conceptual approach using 2D HEC-RAS software according to the three embankment dam break scenarios, LiDAR data (0.5 m spatial resolution), and 2D hydraulic modeling for the Başeu multi-reservoir system which belongs to the Başeu River (NE Romania) including R1—Cal Alb reservoir, R2—Movileni reservoirs, R3—Tătărăşeni reservoirs, R4—Negreni reservoirs, and R5—Hăneşti reservoirs. In order to test the flood control capacity of the Bașeu multi-reservoir system, the Cal Alb (R1) dam break scenario (piping failure) was taken into account. Three 2D stream flow modeling configurations based on R1 inflow rate with a 1% (100 year), 0.5% (500 year), and 0.1% (1000 year) recurrence interval and the water volume which can be accumulated with that specific inflow rate (1% = 10.19 × 106 m3; 0.5% = 12.39 × 106 m3; 0.1% = 17.35 × 106 m3) were computed. The potential flood wave impact was achieved on the basis of different flood severity maps (e.g., flood extent, flood depth, flood velocity, flood hazard) generated for each recurrence interval scenario and highlighted within the built-up area of 27 settlements (S1–S27) located downstream of R1. The results showed that the multi-reservoir system of Bașeu River has an important role in flood mitigation and contributes to the APDF in the context of climate change and the intensification of hydrological hazard manifestation in northeastern Romania. Full article
(This article belongs to the Special Issue Hydrology, Water Resources Management and Protection of the Marine Environment-Selected Papers from the 16th International Conference on Environmental Science and Technology (CEST2019))
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18 pages, 5686 KiB  
Review
A Meta-Analysis of Environmental Tradeoffs of Hydropower Dams in the Sekong, Sesan, and Srepok (3S) Rivers of the Lower Mekong Basin
by Sarah E. Null, Ali Farshid, Gregory Goodrum, Curtis A. Gray, Sapana Lohani, Christina N. Morrisett, Liana Prudencio and Ratha Sor
Water 2021, 13(1), 63; https://doi.org/10.3390/w13010063 - 30 Dec 2020
Cited by 16 | Viewed by 8011
Abstract
In Mekong riparian countries, hydropower development provides energy, but also threatens biodiversity, ecosystems, food security, and an unparalleled freshwater fishery. The Sekong, Sesan, and Srepok Rivers (3S Basin) are major tributaries to the Lower Mekong River (LMB), making up 10% of the Mekong [...] Read more.
In Mekong riparian countries, hydropower development provides energy, but also threatens biodiversity, ecosystems, food security, and an unparalleled freshwater fishery. The Sekong, Sesan, and Srepok Rivers (3S Basin) are major tributaries to the Lower Mekong River (LMB), making up 10% of the Mekong watershed but supporting nearly 40% of the fish species of the LMB. Forty-five dams have been built, are under construction, or are planned in the 3S Basin. We completed a meta-analysis of aquatic and riparian environmental losses from current, planned, and proposed hydropower dams in the 3S and LMB using 46 papers and reports from the past three decades. Proposed mainstem Stung Treng and Sambor dams were not included in our analysis because Cambodia recently announced a moratorium on mainstem Mekong River dams. More than 50% of studies evaluated hydrologic change from dam development, 33% quantified sediment alteration, and 30% estimated fish production changes. Freshwater fish diversity, non-fish species, primary production, trophic ecology, and nutrient loading objectives were less commonly studied. We visualized human and environmental tradeoffs of 3S dams from the reviewed papers. Overall, Lower Sesan 2, the proposed Sekong Dam, and planned Lower Srepok 3A and Lower Sesan 3 have considerable environmental impacts. Tradeoff analyses should include environmental objectives by representing organisms, habitats, and ecosystems to quantify environmental costs of dam development and maintain the biodiversity and extraordinary freshwater fishery of the LMB. Full article
(This article belongs to the Special Issue Channels for Change: Integrating Multiple Disciplines for New Frontiers in Managing the Mekong River Basin)
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31 pages, 7677 KiB  
Article
Improving Water Sustainability through Modeling Optimum Sites for Riparian Forest Reforestation
by Daniel Henrique Alves Torres, Dácio de Castro Vivas Neto, Danilo Vieira Mendes dos Santos and Carlos Alberto Pereira Soares
Water 2021, 13(1), 46; https://doi.org/10.3390/w13010046 - 29 Dec 2020
Cited by 3 | Viewed by 3266
Abstract
The margins of Brazilian rivers are considered Permanent Preservation Areas—APPs, due to the riparian forest’s water resource preservation capacity. However, a significant portion of the Brazilian Atlantic Forest biome, in which the Jacaré River basin is located, has suffered increasing deforestation over the [...] Read more.
The margins of Brazilian rivers are considered Permanent Preservation Areas—APPs, due to the riparian forest’s water resource preservation capacity. However, a significant portion of the Brazilian Atlantic Forest biome, in which the Jacaré River basin is located, has suffered increasing deforestation over the past decades. This research aimed to use a methodology integrating Geographic Information System (GIS), fuzzy logic, Analytic Hierarchy Process (AHP), and sensitivity analysis to model the selection of riparian protected area stretches that presents the best successful riparian forest reforestation using a real case, the Jacaré river basin, whose characteristics are often in Brazilian watersheds. To identify the main drivers that influence reforestation success, we carried out a broad and detailed bibliographic research. To establish the relative importance among the drivers, we conducted a survey with experts. The results showed that areas with moderate chances of reforestation prevail in the studied region. Due to the areas’ distribution pattern, a significant portion of the best sites were grouped, forming regions that create environments that favor aquatic and riverside life development and ecological balance maintenance, thus bringing together fundamental characteristics to improve water resources sustainability. The best sites have dystrophic or eutrophic soil, with a slope of up to 15%. Besides, they are mainly covered by grass and are close to forest fragments with low vulnerability. Full article
(This article belongs to the Section Hydrology)
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31 pages, 811 KiB  
Review
Urban Water Consumption at Multiple Spatial and Temporal Scales. A Review of Existing Datasets
by Anna Di Mauro, Andrea Cominola, Andrea Castelletti and Armando Di Nardo
Water 2021, 13(1), 36; https://doi.org/10.3390/w13010036 - 28 Dec 2020
Cited by 59 | Viewed by 9055
Abstract
Over the last three decades, the increasing development of smart water meter trials and the rise of demand management has fostered the collection of water demand data at increasingly higher spatial and temporal resolutions. Counting these new datasets and more traditional aggregate water [...] Read more.
Over the last three decades, the increasing development of smart water meter trials and the rise of demand management has fostered the collection of water demand data at increasingly higher spatial and temporal resolutions. Counting these new datasets and more traditional aggregate water demand data, the literature is rich with heterogeneous urban water demand datasets. They are characterized by heterogeneous spatial scales—from urban districts, to households or individual water fixtures—and temporal sampling frequencies—from seasonal/monthly up to sub-daily (minutes or seconds). Motivated by the need of tracking the existing datasets in this rapidly evolving field of investigation, this manuscript is the first comprehensive review effort of the state-of-the-art urban water demand datasets. This paper contributes a review of 92 water demand datasets and 120 related peer-review publications compiled in the last 45 years. The reviewed datasets are classified and analyzed according to the following criteria: spatial scale, temporal scale, and dataset accessibility. This research effort builds an updated catalog of the existing water demand datasets to facilitate future research efforts end encourage the publication of open-access datasets in water demand modelling and management research. Full article
(This article belongs to the Special Issue Smart Urban Water Networks)
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23 pages, 8305 KiB  
Review
Legacy Phosphorus in Lake Okeechobee (Florida, USA) Sediments: A Review and New Perspective
by Thomas M. Missimer, Serge Thomas and Barry H. Rosen
Water 2021, 13(1), 39; https://doi.org/10.3390/w13010039 - 28 Dec 2020
Cited by 22 | Viewed by 8104
Abstract
Lake Okeechobee is one of the largest freshwater lakes in the United States. As a eutrophic lake, it has frequent algal blooms composed predominantly of the cyanobacterium genus Microcystis. Many of the algal blooms are associated with the resuspension of a thixotropic [...] Read more.
Lake Okeechobee is one of the largest freshwater lakes in the United States. As a eutrophic lake, it has frequent algal blooms composed predominantly of the cyanobacterium genus Microcystis. Many of the algal blooms are associated with the resuspension of a thixotropic benthic mud containing legacy nutrients. Since Lake Okeechobee has an area of 1732 km2 (40–50 km radius) and a mean depth of only 2.7 m, there is sufficient fetch and shallow water depth to allow frequent wind, wave, and current generated events, which cause sediment resuspension. Three types of mud exist in the lake including an immobile dark-colored, consolidated mud, a brownish-colored mud, which is poorly consolidated and mobile, and a dark-colored thixotropic, highly mobile mud that is a mixture of organic matter and clay-sized minerals. Altogether, these muds contain an estimated 4.6 × 106 kg of total phosphorus and commensurate high amounts of labile nitrogen. The thixotropic mud covers most of the lakebed and contains the suitable nutrient ratios to trigger algal blooms. A bioassay analysis of the thixotropic mud compared to the consolidated mud showed that it produced up to 50% more nutrient mass compared to the consolidated mud. The thixotropic mud does not consolidate, thus remains mobile. The mobility is maintained by the dynamics of the algal blooms and bacterial decay of extracellular secretions (transparent exopolymer particles) that bind sediment, transfer it to the bottom, and undergo bacterial digestion causing gas emissions, thus maintaining the organic/sediment matrix in suspension. Despite major efforts to control external nutrient loading into the lake, the high frequency of algal blooms will continue until the muds bearing legacy nutrients are removed from the lake. Full article
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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20 pages, 3899 KiB  
Article
Elimination of Microplastics by Downstream Sand Filters in Wastewater Treatment
by Sebastian Wolff, Felix Weber, Jutta Kerpen, Miriam Winklhofer, Markus Engelhart and Luisa Barkmann
Water 2021, 13(1), 33; https://doi.org/10.3390/w13010033 - 27 Dec 2020
Cited by 56 | Viewed by 12078
Abstract
The elimination of microplastic particles (MPP) and microplastic fibers (MPF) was investigated in the final treatment stage (sand filtration) in two municipal wastewater treatment plants (WWTP) and the final treatment stage (sand filtration) at a process WWTP of a manufacturer of polyvinyl chloride [...] Read more.
The elimination of microplastic particles (MPP) and microplastic fibers (MPF) was investigated in the final treatment stage (sand filtration) in two municipal wastewater treatment plants (WWTP) and the final treatment stage (sand filtration) at a process WWTP of a manufacturer of polyvinyl chloride (PVC). At each sampling site, three samples on three different days were taken (before/after sand filtration). The samples were filtered through a 10 μm stainless steel cartridge filter utilizing a stainless steel centrifugal pump. Microplastics (MP) were separated from the wastewater matrix by oxidative treatment and density separation and analyzed by Raman microspectroscopy. Due to precautionary measures, procedural blanks were very low with a mean number of 4.3 ± 2.7 MPP and 0.88 ± 0.56 MPF within eight blank samples. The municipal WWTPs were able to eliminate 99.2% ± 0.29% and 99.4% ± 0.15% of MP in the sand filtration stage. The sand filtration of a PVC manufacturer eliminated 99.2%–99.9%. Full article
(This article belongs to the Special Issue Microplastics and Microfibers in Water and Wastewater: A Grand Challenge)
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13 pages, 4884 KiB  
Article
Modeling the Swelling of Hydrogels with Application to Storage of Stormwater
by Hans O. Åkerstedt, T. Staffan Lundström, I. A. Sofia Larsson, Jiri Marsalek and Maria Viklander
Water 2021, 13(1), 34; https://doi.org/10.3390/w13010034 - 27 Dec 2020
Cited by 4 | Viewed by 3793
Abstract
The swelling effect in hydrogel bodies or sponge-like porous bodies (SPB) used in a specific stormwater storage concept of the down-flow type is considered. A macroscopic swelling model is proposed, in which water is assumed to penetrate into the hydrogel by diffusion described [...] Read more.
The swelling effect in hydrogel bodies or sponge-like porous bodies (SPB) used in a specific stormwater storage concept of the down-flow type is considered. A macroscopic swelling model is proposed, in which water is assumed to penetrate into the hydrogel by diffusion described by diffusion equations together with a free-moving boundary separating the interface between the water and hydrogel. Such a type of problem belongs to the certain class of problems called Stefan-problems. The main objective of this contribution is to compare how the theoretical total amount of absorbed water is modified by the inclusion of swelling, when compared to the previously studied SPB devices analyzed only for the effect of diffusion. The results can be summarized in terms of the geometrical dimensions of the storage device and the magnitude of the diffusion coefficient D. The geometrical variables influence both the maximum possible absorbed volume and the time to reach that volume. The diffusion coefficient D only influences the rate of volume growth and the time to reach the maximum volume of stored water. The initial swelling of the hydrogel SPB grows with time (Dt) until the steady state is reached and the swelling rate approaches zero. In all the cases considered, the swelling in general increases the maximum possible absorbed water volume by an amount of 14%. Full article
(This article belongs to the Special Issue Industrial and Environmental Fluid Mechanics)
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16 pages, 2545 KiB  
Article
Estimation of Hourly Flood Hydrograph from Daily Flows Using Artificial Neural Network and Flow Disaggregation Technique
by Jeongwoo Lee, Jeong Eun Lee and Nam Won Kim
Water 2021, 13(1), 30; https://doi.org/10.3390/w13010030 - 26 Dec 2020
Cited by 11 | Viewed by 4001
Abstract
Flood data on a high temporal scale are required for the design of hydraulic structures, flood risk assessment, flood protection, and reservoir operations. Such flood data are typically generated using rainfall-runoff models through an accurate calibration process. The data also can be estimated [...] Read more.
Flood data on a high temporal scale are required for the design of hydraulic structures, flood risk assessment, flood protection, and reservoir operations. Such flood data are typically generated using rainfall-runoff models through an accurate calibration process. The data also can be estimated using a simple relationship between the daily and the sub-daily flow records as an alternative to rainfall–runoff modelling. In this study, we propose an approach combining an artificial neural network (ANN) model for peak flow estimation and the steepness index unit volume flood hydrograph (SIUVFH) method for sub-daily flow disaggregation to generate hydrographs on an hourly time scale. The SIUVFH method is based on the strong relationship between the flood peak and the steepness index, which is defined as the difference between the daily flood peak and daily flow several days before the peak; it is also used for selecting a reference unit volume flood hydrograph to be scaled to obtain the sub-daily flood hydrograph. In this study, to improve the applicability of the SIUVFH method for locations with a weak relationship between the flood peak and steepness index, the ANN-based flood peak estimation was used as an additional indicator to determine a reference unit volume flood hydrograph. To apply the proposed method, ANN models for estimating the peak flows from the mean daily flows during peak and adjacent days were constructed for the studied dam sites. The optimal ANN structures were determined through Monte Carlo cross-validation. The results showed a good performance with statistical measurements of relative root mean square errors of 0.155–0.224, 0.208–0.301, and 0.244–0.382 for the training, validation, and testing datasets, respectively. An application of the combined use of the ANN-based peak estimation and the SIUVFH-based flow disaggregation revealed that the disaggregated hourly flows satisfactorily matched the observed flood hydrograph. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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22 pages, 5879 KiB  
Article
A Harmony-Based Approach for Assessing and Regulating Human-Water Relationships: A Case Study of Henan Province in China
by Qiting Zuo, Wen Li, Heng Zhao, Junxia Ma, Chunhui Han and Zengliang Luo
Water 2021, 13(1), 32; https://doi.org/10.3390/w13010032 - 26 Dec 2020
Cited by 25 | Viewed by 3733
Abstract
The conflict of the human-water relationships (HWR) has further increased the water-related risks, such as water environment deterioration, water shortages, and even regional violent conflicts for obtaining usable water resources. Knowing how to evaluate and regulate the discordant HWR to form a balanced [...] Read more.
The conflict of the human-water relationships (HWR) has further increased the water-related risks, such as water environment deterioration, water shortages, and even regional violent conflicts for obtaining usable water resources. Knowing how to evaluate and regulate the discordant HWR to form a balanced growth between sustainable socio-economy and water resources protection has become a critical issue in water resources management. The harmony theory method, which provides a new perspective for solving the conflict between humans and water, has been widely used in current studies. However, this method focuses less on the quantitative study of the balance status of HWR. This study proposes a harmony theory-based HWR evaluation method that contains a systematic process of harmony assessment, indicator identification, harmony balance constraints, and harmony regulation for assessing and regulating the discordant HWR. The Henan Province of China, which has a complicated HWR, was selected as a case study to apply and verify the approach proposed in this study. The results indicated that (1) Henan Province showed a poor harmony status. The human–water harmony degree of 18 distinctions in the province varied from 0.41 to 0.76, showing an increasing trend from 2006 to 2018, indicating that the HWR was gradually improving in recent years. (2) The human–water harmony degree showed that HWR in the southwest part of Henan Province, with less human activities, was better than that in its northeast part, which had faster social development. Sanmenxia City, located in the west part of the province, had the highest human–water harmony degree because of the recent water control projects implemented in the city, indicating that human production measures could effectively help improve HWR. (3) At present, Henan Province has serious discordant indicators in these three aspects (water system health, humanistic system development, and human-water system coordination), which proves that it is still facing pressure from both socio-economy sustainable development and water resources protection. Our results provide insight into water resources management in Henan Province and other similar regions. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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15 pages, 3603 KiB  
Article
Potential Sources of Ammonium-Nitrogen in the Coastal Groundwater Determined from a Combined Analysis of Nitrogen Isotope, Biological and Geological Parameters, and Land Use
by Anna Fadliah Rusydi, Shin-Ichi Onodera, Mitsuyo Saito, Fujio Hyodo, Morihiro Maeda, Khori Sugianti and Sunarya Wibawa
Water 2021, 13(1), 25; https://doi.org/10.3390/w13010025 - 25 Dec 2020
Cited by 28 | Viewed by 5497
Abstract
The origin of ammonium-nitrogen in Indonesian coastal groundwater has not been intensively examined, meanwhile the elevated concentration remains a concern. This research aims at tracing the potential sources of ammonium-nitrogen in the groundwater of Indramayu, Indonesia where groundwater is vital for livelihood. From [...] Read more.
The origin of ammonium-nitrogen in Indonesian coastal groundwater has not been intensively examined, meanwhile the elevated concentration remains a concern. This research aims at tracing the potential sources of ammonium-nitrogen in the groundwater of Indramayu, Indonesia where groundwater is vital for livelihood. From results, a combined examination of nitrogen isotope, coliform bacteria, land-use, and geology confirmed the natural and anthropogenic origins of ammonium-nitrogen in the groundwater. In the brackish-water aquaculture region, groundwater has δ15NNH4 values from +1.8 to +4.8‰ signifying that ammonium-nitrogen is derived from mineralization of organic nitrogen to ammonium. Furthermore, ammonium has a significantly positive relationship with sodium indicating the exchangeable ammonium is mobilized to groundwater via cation exchange. Meanwhile ammonium-nitrogen from anthropogenic waste was detected in agricultural and residential region. The groundwater has more varied δ15NNH4 values, from −2.9 to +16.1‰, which implies attenuation of ammonium-nitrogen from several sources namely manure, mineral fertilizer, sewage, and pit latrines. Also, the presence of E. coli confirms the indication of human and animal waste contamination. However, since ammonium has no relationship with sodium, cation exchange is not feasible and ammonium-nitrogen flows into the groundwater from anthropogenic sources along with liquid wastes. Full article
(This article belongs to the Section Hydrology)
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26 pages, 1010 KiB  
Review
Treatment of Wastewaters by Microalgae and the Potential Applications of the Produced Biomass—A Review
by Hareb Al-Jabri, Probir Das, Shoyeb Khan, Mahmoud Thaher and Mohammed AbdulQuadir
Water 2021, 13(1), 27; https://doi.org/10.3390/w13010027 - 25 Dec 2020
Cited by 199 | Viewed by 19459
Abstract
The treatment of different types of wastewater by physicochemical or biological (non-microalgal) methods could often be either inefficient or energy-intensive. Microalgae are ubiquitous microscopic organisms, which thrive in water bodies that contain the necessary nutrients. Wastewaters are typically contaminated with nitrogen, phosphorus, and [...] Read more.
The treatment of different types of wastewater by physicochemical or biological (non-microalgal) methods could often be either inefficient or energy-intensive. Microalgae are ubiquitous microscopic organisms, which thrive in water bodies that contain the necessary nutrients. Wastewaters are typically contaminated with nitrogen, phosphorus, and other trace elements, which microalgae require for their cell growth. In addition, most of the microalgae are photosynthetic in nature, and these organisms do not require an organic source for their proliferation, although some strains could utilize organics both in the presence and absence of light. Therefore, microalgal bioremediation could be integrated with existing treatment methods or adopted as the single biological method for efficiently treating wastewater. This review paper summarized the mechanisms of pollutants removal by microalgae, microalgal bioremediation potential of different types of wastewaters, the potential application of wastewater-grown microalgal biomass, existing challenges, and the future direction of microalgal application in wastewater treatment. Full article
(This article belongs to the Special Issue On-Site Wastewater Treatment)
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23 pages, 2972 KiB  
Review
Review: Sources of Hydrological Model Uncertainties and Advances in Their Analysis
by Edom Moges, Yonas Demissie, Laurel Larsen and Fuad Yassin
Water 2021, 13(1), 28; https://doi.org/10.3390/w13010028 - 25 Dec 2020
Cited by 177 | Viewed by 18916
Abstract
Despite progresses in representing different processes, hydrological models remain uncertain. Their uncertainty stems from input and calibration data, model structure, and parameters. In characterizing these sources, their causes, interactions and different uncertainty analysis (UA) methods are reviewed. The commonly used UA methods are [...] Read more.
Despite progresses in representing different processes, hydrological models remain uncertain. Their uncertainty stems from input and calibration data, model structure, and parameters. In characterizing these sources, their causes, interactions and different uncertainty analysis (UA) methods are reviewed. The commonly used UA methods are categorized into six broad classes: (i) Monte Carlo analysis, (ii) Bayesian statistics, (iii) multi-objective analysis, (iv) least-squares-based inverse modeling, (v) response-surface-based techniques, and (vi) multi-modeling analysis. For each source of uncertainty, the status-quo and applications of these methods are critiqued in gauged catchments where UA is common and in ungauged catchments where both UA and its review are lacking. Compared to parameter uncertainty, UA application for structural uncertainty is limited while input and calibration data uncertainties are mostly unaccounted. Further research is needed to improve the computational efficiency of UA, disentangle and propagate the different sources of uncertainty, improve UA applications to environmental changes and coupled human–natural-hydrologic systems, and ease UA’s applications for practitioners. Full article
(This article belongs to the Special Issue Hydrological Modeling in Water Cycle Processes)
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25 pages, 11772 KiB  
Article
The Effect of Geometric Parameters of the Antivortex on a Triangular Labyrinth Side Weir
by Saeed Abbasi, Sajjad Fatemi, Amir Ghaderi and Silvia Di Francesco
Water 2021, 13(1), 14; https://doi.org/10.3390/w13010014 - 24 Dec 2020
Cited by 35 | Viewed by 3500
Abstract
Side weirs are important structural measures extensively used, for instance, for regulating water levels in rivers and canals. If the length of the opening is limited, the amount of water diverted out of the channel and the effective length can be increased by [...] Read more.
Side weirs are important structural measures extensively used, for instance, for regulating water levels in rivers and canals. If the length of the opening is limited, the amount of water diverted out of the channel and the effective length can be increased by applying a labyrinth side weir. The present study deals with numerical simulations regarding the hydraulic performance of a labyrinth side weir with a triangular plan in single-cycle mode. Specifically, six different types of antivortexes embedded inside it and in various hydraulic conditions at different Froude numbers are analyzed. The antivortexes are studied using two groups, permeable and impermeable, with three different heights: 0.5 P, 0.75 P, and 1 P (P: Weir height). The comparison of the simulated water surface profiles with laboratory results shows that the numerical model is able to capture the flow characteristics on the labyrinth side weir. The use of an antivortex in a triangular labyrinth side weir reduces the secondary flows due to the interaction with the transverse vortexes of the vertical axis and increases the discharge capacity by 11%. Antivortexes in a permeable state outperform those in an impermeable state; the discharge coefficient in the permeable state increases up to 3% with respect to the impermeable state. Finally, based on an examination of the best type of antivortex, taking into account shape, permeability, and height, the discharge coefficient increases to 13.4% compared to a conventional labyrinth side weir. Full article
(This article belongs to the Special Issue Combined Numerical and Experimental Methodology for Fluid–Structure Interactions in Free Surface Flows)
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21 pages, 2659 KiB  
Review
Review: Acid Mine Drainage (AMD) in Abandoned Coal Mines of Shanxi, China
by Zhaoliang Wang, Yongxin Xu, Zhixiang Zhang and Yongbo Zhang
Water 2021, 13(1), 8; https://doi.org/10.3390/w13010008 - 23 Dec 2020
Cited by 68 | Viewed by 8249
Abstract
Excessive exploitation and massive coal mine closures have brought about extensive goafs in Shanxi where 8780 coal mines have been abandoned in the last 20 years. Acid mine drainage (AMD) poses severe environmental impact and has become a prominent problem in Shanxi abandoned [...] Read more.
Excessive exploitation and massive coal mine closures have brought about extensive goafs in Shanxi where 8780 coal mines have been abandoned in the last 20 years. Acid mine drainage (AMD) poses severe environmental impact and has become a prominent problem in Shanxi abandoned coal mine areas, which has aggravated the shortage of water resources and threatened the safety of the local drinking water supply. The purpose of this review is to protect the precious water resources and maintain sustainable use in Shanxi coal mines and downstream. By retrieving and analyzing about 90 domestic and international publications, a critical review of the AMD research results in Shanxi abandoned coal mines is conducted from the perspective of the formation mechanism, migration and transformation, prediction, treatment and management. The results shows that pyrite is the prerequisite for the formation of AMD, oxygen is the inducement, water is the carrier, and Fe3+ and microorganisms are the catalyst. The roadway system and geological structure are the dominant control factors. Finally, current difficulties and future research are pointed out. It is necessary to further strengthen the systematic research on the geological and hydrogeological conditions of abandoned coal mines, and explore an efficient, cheap, environmental technology, and construct the pollution risk assessment model for the AMD treatment. This study provides a scientific basis for the comprehensive treatment and management of AMD in abandoned coal mines in Shanxi. Full article
(This article belongs to the Section Water Quality and Contamination)
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15 pages, 4449 KiB  
Article
Biological Reduction of Organic Matter in Buji River Sediment (Shenzhen, China) with Artificial Oxygenation
by Lin Che, Wenbiao Jin, Xu Zhou, Chenbo Cao, Wei Han, Changlei Qin, Renjie Tu, Yidi Chen, Xiaochi Feng and Qilin Wang
Water 2020, 12(12), 3592; https://doi.org/10.3390/w12123592 - 21 Dec 2020
Cited by 8 | Viewed by 3575
Abstract
In this work, artificial oxygenation treatment (pure oxygen aeration or oxygen enriched water injection) combined with the introduction of exogenous microorganisms was employed to purify urban river sediment for the first time. Results showed that the developed in situ remediation strategy could increase [...] Read more.
In this work, artificial oxygenation treatment (pure oxygen aeration or oxygen enriched water injection) combined with the introduction of exogenous microorganisms was employed to purify urban river sediment for the first time. Results showed that the developed in situ remediation strategy could increase the dissolved oxygen (DO) concentration and oxidation-reduction potential (ORP) value of the sediments. Benefiting from the increase of DO concentration, the bacterial diversity was enhanced. The highest removal efficiencies of organic matter were 18.4% and 22.3% through pure oxygen aeration and oxygen enriched water injection, respectively. More importantly, overlying water quality was not affected. By comparison, oxygen enriched water injection treatment could achieve better performance on sediment purification. Introducing exogenous microorganisms further reduced the organic matter content of the sediment. In short, the current work not only proposed a promising strategy for controlling urban river sediment pollution, but also provided novel insight for the understanding of river sediment containing highly concentrated organic matter. Full article
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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20 pages, 7416 KiB  
Article
Changing Low Flow and Streamflow Drought Seasonality in Central European Headwaters
by Vojtech Vlach, Ondrej Ledvinka and Milada Matouskova
Water 2020, 12(12), 3575; https://doi.org/10.3390/w12123575 - 20 Dec 2020
Cited by 21 | Viewed by 4682
Abstract
In the context of the ongoing climate warming in Europe, the seasonality and magnitudes of low flows and streamflow droughts are expected to change in the future. Increasing temperature and evaporation rates, stagnating precipitation amounts and decreasing snow cover will probably further intensify [...] Read more.
In the context of the ongoing climate warming in Europe, the seasonality and magnitudes of low flows and streamflow droughts are expected to change in the future. Increasing temperature and evaporation rates, stagnating precipitation amounts and decreasing snow cover will probably further intensify the summer streamflow deficits. This study analyzed the long-term variability and seasonality of low flows and streamflow droughts in fifteen headwater catchments of three regions within Central Europe. To quantify the changes in the low flow regime of selected catchments during the 1968–2019 period, we applied the R package lfstat for computing the seasonality ratio (SR), the seasonality index (SI), mean annual minima, as well as for the detection of streamflow drought events along with deficit volumes. Trend analysis of summer minimum discharges was performed using the Mann–Kendall test. Our results showed a substantial increase in the proportion of summer low flows during the analyzed period, accompanied with an apparent shift in the average date of low flow occurrence towards the start of the year. The most pronounced seasonality shifts were found predominantly in catchments with the mean altitude 800–1000 m.a.s.l. in all study regions. In contrast, the regime of low flows in catchments with terrain above 1000 m.a.s.l. remained nearly stable throughout the 1968–2019 period. Moreover, the analysis of mean summer minimum discharges indicated a much-diversified pattern in behavior of long-term trends than it might have been expected. The findings of this study may help identify the potentially most vulnerable near-natural headwater catchments facing worsening summer water scarcity. Full article
(This article belongs to the Special Issue Statistical Approach to Hydrological Analysis)
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23 pages, 6364 KiB  
Review
Urban Flooding Mitigation Techniques: A Systematic Review and Future Studies
by Yinghong Qin
Water 2020, 12(12), 3579; https://doi.org/10.3390/w12123579 - 20 Dec 2020
Cited by 74 | Viewed by 24058
Abstract
Urbanization has replaced natural permeable surfaces with roofs, roads, and other sealed surfaces, which convert rainfall into runoff that finally is carried away by the local sewage system. High intensity rainfall can cause flooding when the city sewer system fails to carry the [...] Read more.
Urbanization has replaced natural permeable surfaces with roofs, roads, and other sealed surfaces, which convert rainfall into runoff that finally is carried away by the local sewage system. High intensity rainfall can cause flooding when the city sewer system fails to carry the amounts of runoff offsite. Although projects, such as low-impact development and water-sensitive urban design, have been proposed to retain, detain, infiltrate, harvest, evaporate, transpire, or re-use rainwater on-site, urban flooding is still a serious, unresolved problem. This review sequentially discusses runoff reduction facilities installed above the ground, at the ground surface, and underground. Mainstream techniques include green roofs, non-vegetated roofs, permeable pavements, water-retaining pavements, infiltration trenches, trees, rainwater harvest, rain garden, vegetated filter strip, swale, and soakaways. While these techniques function differently, they share a common characteristic; that is, they can effectively reduce runoff for small rainfalls but lead to overflow in the case of heavy rainfalls. In addition, most of these techniques require sizable land areas for construction. The end of this review highlights the necessity of developing novel, discharge-controllable facilities that can attenuate the peak flow of urban runoff by extending the duration of the runoff discharge. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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20 pages, 6455 KiB  
Article
Unravelling Climate and Anthropogenic Forcings on the Evolution of Surface Water Resources in Southern France
by Camille Labrousse, Wolfgang Ludwig, Sébastien Pinel, Mahrez Sadaoui and Guillaume Lacquement
Water 2020, 12(12), 3581; https://doi.org/10.3390/w12123581 - 20 Dec 2020
Cited by 8 | Viewed by 4425
Abstract
In the Mediterranean, climate change and human pressures are expected to significantly impact the availability of surface water resources. In order to quantify these impacts during the last 60 years (1959–2018), we examined the hydro-climatic and land use change evolution in six coastal [...] Read more.
In the Mediterranean, climate change and human pressures are expected to significantly impact the availability of surface water resources. In order to quantify these impacts during the last 60 years (1959–2018), we examined the hydro-climatic and land use change evolution in six coastal river basins of the Gulf of Lion in southern France. By combining observed water discharge, gridded climate, mapped land use and agricultural censuses data, we propose a statistical regression model which successfully reproduces the variability of annual water discharge in all basins. Our results clearly demonstrate that, despite important anthropogenic water withdrawals for irrigation, climate change is the major driver for the detected reduction of water discharge. The model can explain 78–88% of the variability of annual water discharge in the study catchments. It requires only two climatic indices that are solely computed from monthly temperature (T) and precipitation (P) data, thus allowing the estimation of the respective contributions of both parameters in the detected changes. According to our results, the study region experienced on average a warming trend of 1.6 °C during the last 60 years which alone was responsible for a reduction of almost 25% of surface water resources. Full article
(This article belongs to the Special Issue Impacts of Climate Change and Anthropogenic Activities on the Spatio-Temporal Variability of River Flow)
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22 pages, 10942 KiB  
Article
Risk Assessment of Irrigation-Related Soil Salinization and Sodification in Mediterranean Areas
by Alexandra Tomaz, Patrícia Palma, Sofia Fialho, Ana Lima, Paula Alvarenga, Miguel Potes, Maria João Costa and Rui Salgado
Water 2020, 12(12), 3569; https://doi.org/10.3390/w12123569 - 19 Dec 2020
Cited by 33 | Viewed by 8215
Abstract
Salinization and sodification are important processes of soil degradation affecting irrigated lands. A large proportion of the global irrigated area is affected by some degree of soil salinity or sodicity caused by the intensification of irrigation. The increase of the frequency of adverse [...] Read more.
Salinization and sodification are important processes of soil degradation affecting irrigated lands. A large proportion of the global irrigated area is affected by some degree of soil salinity or sodicity caused by the intensification of irrigation. The increase of the frequency of adverse climatic conditions, like high temperatures and variations in precipitation patterns caused by climate change, will potentially amplify these processes in arid, semi-arid, and Mediterranean areas. The use of integrated approaches for the spatial and temporal prediction of the risk of salinization and sodification in irrigated areas is of great value, helping in the decision-making regarding land uses and choice of more suitable agricultural practices. In this study, based on key criteria for the assessment of irrigation-related salinization processes (e.g., climate, topography, soil drainage, water quality for irrigation, and crop irrigation method), we developed a methodology for the prediction of soil salinity and sodicity risk in irrigated lands, using two composite indices, the Salinization Risk (RSA) index and the Sodification Risk (RSO) index. The application of these indices to a real scenario (a Mediterranean area in Southern Portugal) showed that 67% of the potentially irrigated area presented a low risk of salinity development, 68% had a moderate risk of sodification, and 16% was of high risk of sodicity development. Areas under moderate risk of salinization (26%) were mostly characterized by low slopes and fine-textured soils, like Luvisols and Vertisols, with limited drainage conditions. Areas with high risk of soil sodification presented a large incidence of low slope terrain, moderate-to-restricted soil drainage, in high clay content Luvisols, Vertisols and Cambisols, and land use dominated by annual crops irrigated with surface or sprinkler systems. These risk prediction tools have the potential to be used for resource use planning by policymakers and on-farm management decision by farmers, contributing to the sustainability of irrigated agriculture in Mediterranean regions. Full article
(This article belongs to the Special Issue Multiple Stressors Effects on Soil and Freshwater Ecosystems, in a Climate Change Scenario)
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19 pages, 3439 KiB  
Article
An Application of Correlation and Spectral Analysis in Hydrological Study of Neighboring Karst Springs
by Vesna Denić-Jukić, Ana Lozić and Damir Jukić
Water 2020, 12(12), 3570; https://doi.org/10.3390/w12123570 - 19 Dec 2020
Cited by 18 | Viewed by 4589
Abstract
Various methods of time series analysis have been used in studies of karst hydrological systems. Among these methods, correlation and spectral analysis have had an important role. The correlation analysis most often has been based on determination of correlation coefficients and correlation functions. [...] Read more.
Various methods of time series analysis have been used in studies of karst hydrological systems. Among these methods, correlation and spectral analysis have had an important role. The correlation analysis most often has been based on determination of correlation coefficients and correlation functions. Partial correlation functions (PCF) are a mathematical tool of the correlation analysis which practical applicability in karst hydrology is insufficiently explored. In this study, the correlation and spectral analysis are applied on the catchment of Rumin Springs located in the Dinaric karst area between Croatia and Bosnia and Herzegovina. The available daily data are the rainfall, air temperature and relative humidity from three locations, as well as the discharge from two springs. The periods before and after the construction of HPP Orlovac in 1973 are analyzed. The basic hypothesis is that a difference between PCF obtained for two neighboring karst springs describe a difference in their functioning. The results of application show that PCF can resolve some ambiguities concerning the effects included in correlation functions and can provide the additional information that cannot be obtained by other methods of time series analysis. The obtained results are mostly in accordance with the present knowledge, and they support the existing hypotheses about the functioning of Rumin Springs. Full article
(This article belongs to the Special Issue Recent Advances in Karstic Hydrogeology)
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29 pages, 3815 KiB  
Article
Stable Carbon Isotopes of Phytoplankton as a Tool to Monitor Anthropogenic CO2 Submarine Leakages
by Federica Relitti, Nives Ogrinc, Michele Giani, Federica Cerino, Mirta Smodlaka Tankovic, Ana Baricevic, Lidia Urbini, Bor Krajnc, Paola Del Negro and Cinzia De Vittor
Water 2020, 12(12), 3573; https://doi.org/10.3390/w12123573 - 19 Dec 2020
Cited by 1 | Viewed by 5373
Abstract
This study aims to validate the stable carbon isotopic composition (δ13C) of phytoplankton as a tool for detecting submarine leakages of anthropogenic CO2(g), since it is characterised by δ13C values significantly lower than the natural CO [...] Read more.
This study aims to validate the stable carbon isotopic composition (δ13C) of phytoplankton as a tool for detecting submarine leakages of anthropogenic CO2(g), since it is characterised by δ13C values significantly lower than the natural CO2 dissolved in oceans. Three culture experiments were carried out to investigate the changes in δ13C of the diatom Thalassiosira rotula during growth in an artificially modified medium (ASW). Three different dissolved inorganic carbon (DIC) concentrations were tested to verify if carbon availability affects phytoplankton δ13C. Simultaneously, at each experiment, T. rotula was cultured under natural DIC isotopic composition (δ13CDIC) and carbonate system conditions. The available DIC pool for diatoms grown in ASW was characterised by δ13CDIC values (−44.2 ± 0.9‰) significantly lower than the typical marine range. Through photosynthetic DIC uptake, microalgae δ13C rapidly changed, reaching significantly low values (until −43.4‰). Moreover, the different DIC concentrations did not affect the diatom δ13C, exhibiting the same trend in δ13C values in the three ASW experiments. The experiments prove that phytoplankton isotopic composition quickly responds to changes in the δ13C of the medium, making this approach a promising and low-impact tool for detecting CO2(g) submarine leakages from CO2(g) deposits. Full article
(This article belongs to the Section Hydrology)
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27 pages, 1135 KiB  
Review
Biochar as an Eco-Friendly and Economical Adsorbent for the Removal of Colorants (Dyes) from Aqueous Environment: A Review
by Prithvi Srivatsav, Bhaskar Sriharsha Bhargav, Vignesh Shanmugasundaram, Jayaseelan Arun, Kannappan Panchamoorthy Gopinath and Amit Bhatnagar
Water 2020, 12(12), 3561; https://doi.org/10.3390/w12123561 - 18 Dec 2020
Cited by 221 | Viewed by 18599
Abstract
Dyes (colorants) are used in many industrial applications, and effluents of several industries contain toxic dyes. Dyes exhibit toxicity to humans, aquatic organisms, and the environment. Therefore, dyes containing wastewater must be properly treated before discharging to the surrounding water bodies. Among several [...] Read more.
Dyes (colorants) are used in many industrial applications, and effluents of several industries contain toxic dyes. Dyes exhibit toxicity to humans, aquatic organisms, and the environment. Therefore, dyes containing wastewater must be properly treated before discharging to the surrounding water bodies. Among several water treatment technologies, adsorption is the most preferred technique to sequester dyes from water bodies. Many studies have reported the removal of dyes from wastewater using biochar produced from different biomass, e.g., algae and plant biomass, forest, and domestic residues, animal waste, sewage sludge, etc. The aim of this review is to provide an overview of the application of biochar as an eco-friendly and economical adsorbent to remove toxic colorants (dyes) from the aqueous environment. This review highlights the routes of biochar production, such as hydrothermal carbonization, pyrolysis, and hydrothermal liquefaction. Biochar as an adsorbent possesses numerous advantages, such as being eco-friendly, low-cost, and easy to use; various precursors are available in abundance to be converted into biochar, it also has recyclability potential and higher adsorption capacity than other conventional adsorbents. From the literature review, it is clear that biochar is a vital candidate for removal of dyes from wastewater with adsorption capacity of above 80%. Full article
(This article belongs to the Special Issue Adsorbents for Water and Wastewater Treatment and Resource Recovery)
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20 pages, 6782 KiB  
Article
Modified Convergent Flow Tracing Method for Evaluating Advective Velocity and Effective Porosity in Fractured Rock Aquifers
by Byung-Woo Kim and Hangbok Lee
Water 2020, 12(12), 3565; https://doi.org/10.3390/w12123565 - 18 Dec 2020
Cited by 1 | Viewed by 3481
Abstract
This study presented the analysis of the modified convergent flow tracing method, which is a modified virtual solute transport approach to retrieve tracer masses from a pulse image (virtual) well to an extraction well. In the convergent flow tracer test, approximate analytical solutions [...] Read more.
This study presented the analysis of the modified convergent flow tracing method, which is a modified virtual solute transport approach to retrieve tracer masses from a pulse image (virtual) well to an extraction well. In the convergent flow tracer test, approximate analytical solutions were extended for the pulse image well using a single-well tracing method. This method transformed the drift-and-pumpback conditions of the single-well tracing method. The method requires a prior information of the effective porosity. Using sodium chloride as a tracer mass, the tracer data sampled through field-scale tests were used to obtain breakthrough curves. This modified method was different from the pre-existing single method because it considers both the ambient groundwater movement (the two classes of drifts) and the constant volumetric flow rate during the pumping phase. The method was applied to the tracer test at underground research tunnel for verifying the theory inductively derived from the single tracing method. Through field tests, the values of velocity and porosity were compared to the results of the drift-and-pumpback equations of the single-well test, and the several different equations related to breakthrough curves of the two-well tests conducted on a field scale. Full article
(This article belongs to the Special Issue Applying Artificial and Environmental Tracing Techniques in Hydrogeology)
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16 pages, 5750 KiB  
Article
Modelling of Flood Inundation due to Levee Breaches: Sensitivity of Flood Inundation against Breach Process Parameters
by Yohannis Birhanu Tadesse and Peter Fröhle
Water 2020, 12(12), 3566; https://doi.org/10.3390/w12123566 - 18 Dec 2020
Cited by 9 | Viewed by 3888
Abstract
This paper analyses the sensitivity of flood inundation due to river levee breach against breach process parameters using the 1996 Awash River levee breach case at Wonji, Ethiopia. A parametric levee breach model integrated into the 2D hydrodynamic numerical model Telemac-2D is used [...] Read more.
This paper analyses the sensitivity of flood inundation due to river levee breach against breach process parameters using the 1996 Awash River levee breach case at Wonji, Ethiopia. A parametric levee breach model integrated into the 2D hydrodynamic numerical model Telemac-2D is used to simulate a levee breach flood event at Wonji, Ethiopia. Levee breach process parameters are systemically varied to find out their effect on the flood inundation. The analysis of the model results shows that the flood inundation is sensitive to the final breach dimensions and breach location. However, the parameters describing the levee breach development have negligible influence on the flood inundation. This implies that final breach dimension and breach location in an event of levee breach are the most important and decisive parameters affecting the resulting inundation of the flood plain, and as such should be given due consideration when creating flood inundation maps due to levee breach. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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15 pages, 2351 KiB  
Article
Effect of Plasma Activated Water Foliar Application on Selected Growth Parameters of Maize (Zea mays L.)
by Petr Škarpa, Daniel Klofáč, František Krčma, Jana Šimečková and Zdenka Kozáková
Water 2020, 12(12), 3545; https://doi.org/10.3390/w12123545 - 17 Dec 2020
Cited by 42 | Viewed by 5295
Abstract
Utilization of plasma activated water (PAW) for plant growing is mainly connected with the treatment of seeds and subsequent stimulation of their germination. A potential of PAW is its relatively simple and low-cost preparation that calls for studying its wider application in plant [...] Read more.
Utilization of plasma activated water (PAW) for plant growing is mainly connected with the treatment of seeds and subsequent stimulation of their germination. A potential of PAW is its relatively simple and low-cost preparation that calls for studying its wider application in plant production. For this purpose, a pot experiment was realized in order to prove effects of the foliar PAW application on maize growth. The stepped PAW foliar application, carried out in 7-day intervals, led to provable decrease of chlorophyll contents in leaves compared to the distilled water application. The PAW application significantly increased root electrical capacitance, but it had no provable effect on weight of the aboveground biomass. Chlorophyll fluorescence parameters expressing the CO2 assimilation rate and variable fluorescence of dark-adapted leaves were provably decreased by PAW, but quantum yield of photosystem II electron transport was not influenced. A provably higher amount of nitrogen was detected in dry matter of plants treated by PAW, but contents of other macro- and micro-nutrients in the aboveground biomass of maize were not affected. Results of this pilot verification of the PAW application have shown a potential for plant growth optimization and possibility for its further utilization, especially in combination with liquid fertilizers. Full article
(This article belongs to the Special Issue Applications of Plasma Activated Water and Media in Medicine and Agriculture)
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20 pages, 5820 KiB  
Article
Photocatalytic Degradation of Polyamide 66; Evaluating the Feasibility of Photocatalysis as a Microfibre-Targeting Technology
by Jae-Mee Lee, Rosa Busquets, In-Cheol Choi, Sung-Ho Lee, Jong-Kyu Kim and Luiza C. Campos
Water 2020, 12(12), 3551; https://doi.org/10.3390/w12123551 - 17 Dec 2020
Cited by 56 | Viewed by 6261
Abstract
Wastewater treatment plants (WWTPs) have been identified as main contributors to releasing microfibres into the environment, however, WWTPs do not have microfibre-targeting technologies. In this study, photocatalysis is evaluated as a potential technology to treat microfibres in WWTPs by studying the degradation of [...] Read more.
Wastewater treatment plants (WWTPs) have been identified as main contributors to releasing microfibres into the environment, however, WWTPs do not have microfibre-targeting technologies. In this study, photocatalysis is evaluated as a potential technology to treat microfibres in WWTPs by studying the degradation of polyamide 66 (PA66) microfibres using ultraviolet (UV) and titanium dioxide (TiO2). PA66 microfibres suspended in deionised water were exposed to different combinations of UV and TiO2. The degradation of the PA66 microfibres was monitored by changes in mass, carbonyl index and morphology using microbalance, infrared spectroscopy, and scanning electron microscopy. The formation of by-products from the degradation of the fibres was evaluated by measuring the chemical oxygen demand (COD) of the treated water. The degradation efficiency was optimised under UVC with a dose of 100 mg TiO2/L. Under these conditions, the PA66 microfibres presented a 97% mass loss within 48 h. The photocatalytic conditions applied generated a relatively low level of by-products (<10 mg/L of COD). Therefore, photocatalysis with TiO2 an UVC could potentially be a feasible technology to treat microfibres in WWTPs, although more investigation is required to establish if this treatment leads to the formation of nanofibres. Further work is needed to translate the present optimised conditions to WWTPs. Full article
(This article belongs to the Special Issue Microplastics and Microfibers in Water and Wastewater: A Grand Challenge)
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13 pages, 1371 KiB  
Article
Nitrogen and Phosphorus Concentration Thresholds toward Establishing Water Quality Criteria for Pennsylvania, USA
by John W. Clune, J. Kent Crawford and Elizabeth W. Boyer
Water 2020, 12(12), 3550; https://doi.org/10.3390/w12123550 - 17 Dec 2020
Cited by 12 | Viewed by 5398
Abstract
Nutrient enrichment is currently a leading cause of impairment to streams in Pennsylvania. Evaluating the water quality condition and eutrophic status of streams and rivers is a challenge without established thresholds for nutrient concentrations, which can vary depending on climate and landscape characteristics. [...] Read more.
Nutrient enrichment is currently a leading cause of impairment to streams in Pennsylvania. Evaluating the water quality condition and eutrophic status of streams and rivers is a challenge without established thresholds for nutrient concentrations, which can vary depending on climate and landscape characteristics. The US Environmental Protection Agency (USEPA) has published nutrient criteria for nutrient ecoregions nationwide that are used as regional baseline values; and has encouraged states to develop more refined values if better data are available. In this study, we quantified long-term nutrient concentrations observed in streams and rivers across Pennsylvania using a robust water quality dataset compiled from monitoring data collected over the past two decades (2000–2019) by multiple agencies. We estimated nutrient criteria concentration thresholds for each ecoregion using USEPA’s percentile approach. The 25th percentile median concentrations observed in streams and rivers ranged from 0.27 to 2.30 mg/L for total nitrogen (TN), and from 0.010 to 0.053 mg/L for total phosphorus (TP). The percent of sites with available data that exceeded the 25th percentile was 53% for TN and 60% for TP, reflecting longstanding problems with nutrient pollution of rivers and streams in Pennsylvania. The 25th percentile may overestimate background condition levels, as nutrient conditions vary substantially within and among ecoregions. We compared our contemporary concentrations at the threshold values to other published recommended criteria for the region and explored the influence of landscape heterogeneity and seasonality on nutrient concentrations. The spatial and temporal variability of nutrient conditions emphasizes the importance of using percentile analysis as only a guide toward more robust response-based methods, rather than as a method for setting nutrient criteria in Pennsylvania. Our results provide environmental managers with new insights regarding the status of nutrient conditions in streams and rivers across Pennsylvania ecoregions toward further developing numeric nutrient criteria. Full article
(This article belongs to the Special Issue Advances in Aquatic Pollution Assessment and Management)
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13 pages, 2963 KiB  
Article
Comparison of Different Anode Materials to Remove Microcystis aeruginosa Cells Using Electro-Coagulation–Flotation Process at Low Current Inputs
by Thenuwara Arachchige Omila Kasun Meetiyagoda and Takeshi Fujino
Water 2020, 12(12), 3528; https://doi.org/10.3390/w12123528 - 16 Dec 2020
Cited by 9 | Viewed by 4575
Abstract
Cyanobacterial blooms are a threat to the drinking water supply owing to their potential toxicity. Microcystins which are the most widespread cyanotoxins, are mainly produced by Microcystis spp. In this study, we cultured Microcystis aeruginosa cells in BG-11 medium at 25 °C to [...] Read more.
Cyanobacterial blooms are a threat to the drinking water supply owing to their potential toxicity. Microcystins which are the most widespread cyanotoxins, are mainly produced by Microcystis spp. In this study, we cultured Microcystis aeruginosa cells in BG-11 medium at 25 °C to investigate the efficiency of the electro-coagulation–flotation process to remove them. Different anode materials (Fe, Al, Cu, and Zn) along with a graphite cathode were compared separately in the 10–100 mA current range in a 0.025 M Na2SO4 electrolyte. Turbidity, optical density at 684 nm (OD684), OD730, Chl-a concentration, and DOC concentration were analyzed to clarify the mechanism by which M. aeruginosa cells are removed. The Al anode indicated the highest removal efficiencies in terms of turbidity (90%), OD684 and OD730 (98%), and Chl-a concentration (96%) within 30 min at 4.0 mA/cm2 current density and the lowest average electrode consumption of 0.120 ± 0.023 g/L. The energy consumption of the Al electrode was 0.80 Wh/L. From these results, we found that Al was the best among the anode materials evaluated to remove M. aeruginosa cells. However, further studies are required to optimize the Al anode in terms of pH, treatment time, electrode distance, and electrolyte concentration to enhance the removal of M. aeruginosa cells. Full article
(This article belongs to the Section Water and One Health)
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16 pages, 2632 KiB  
Article
Effect of Clay Colloid Particles on Formaldehyde Transport in Unsaturated Porous Media
by Theodosia V. Fountouli and Constantinos V. Chrysikopoulos
Water 2020, 12(12), 3541; https://doi.org/10.3390/w12123541 - 16 Dec 2020
Cited by 13 | Viewed by 2767
Abstract
This study examines the effects of two representative colloid-sized clay particles (kaolinite, KGa-1b and montmorillonite, STx-1b) on the transport of formaldehyde (FA) in unsaturated porous media. The transport of FA was examined with and without the presence of clay particles under [...] Read more.
This study examines the effects of two representative colloid-sized clay particles (kaolinite, KGa-1b and montmorillonite, STx-1b) on the transport of formaldehyde (FA) in unsaturated porous media. The transport of FA was examined with and without the presence of clay particles under various flow rates and various levels of saturation in columns packed with quartz sand, under unsaturated conditions. The experimental results clearly suggested that the presence of clay particles retarded by up to ~23% the transport of FA in unsaturated packed columns. Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction energy calculations demonstrated that permanent retention of clay colloids at air-water interfaces (AWI) and solid-water interfaces (SWI) was negligible, except for the pair (STx-1b)–SWI. The experimental results of this study showed that significant clay colloid retention occurred in the unsaturated column, especially at low flow rates. This deviation from DLVO predictions may be explained by the existence of additional non-DLVO forces (hydrophobic and capillary forces) that could be much stronger than van der Waals and double layer forces. The present study shows the important role of colloids, which may act as carriers of contaminants. Full article
(This article belongs to the Section Water Quality and Contamination)
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22 pages, 2567 KiB  
Article
Fate of Trace Organic Compounds in Hyporheic Zone Sediments of Contrasting Organic Carbon Content and Impact on the Microbiome
by Cyrus Rutere, Malte Posselt and Marcus A. Horn
Water 2020, 12(12), 3518; https://doi.org/10.3390/w12123518 - 15 Dec 2020
Cited by 11 | Viewed by 3006
Abstract
The organic carbon in streambed sediments drives multiple biogeochemical reactions, including the attenuation of organic micropollutants. An attenuation assay using sediment microcosms differing in the initial total organic carbon (TOC) revealed higher microbiome and sorption associated removal efficiencies of trace organic compounds (TrOCs) [...] Read more.
The organic carbon in streambed sediments drives multiple biogeochemical reactions, including the attenuation of organic micropollutants. An attenuation assay using sediment microcosms differing in the initial total organic carbon (TOC) revealed higher microbiome and sorption associated removal efficiencies of trace organic compounds (TrOCs) in the high-TOC compared to the low-TOC sediments. Overall, the combined microbial and sorption associated removal efficiencies of the micropollutants were generally higher than by sorption alone for all compounds tested except propranolol whose removal efficiency was similar via both mechanisms. Quantitative real-time PCR and time-resolved 16S rRNA gene amplicon sequencing revealed that higher bacterial abundance and diversity in the high-TOC sediments correlated with higher microbial removal efficiencies of most TrOCs. The bacterial community in the high-TOC sediment samples remained relatively stable against the stressor effects of TrOC amendment compared to the low-TOC sediment community that was characterized by a decline in the relative abundance of most phyla except Proteobacteria. Bacterial genera that were significantly more abundant in amended relative to unamended sediment samples and thus associated with biodegradation of the TrOCs included Xanthobacter, Hyphomicrobium, Novosphingobium, Reyranella and Terrimonas. The collective results indicated that the TOC content influences the microbial community dynamics and associated biotransformation of TrOCs as well as the sorption potential of the hyporheic zone sediments. Full article
(This article belongs to the Special Issue Environmental Fate of Contaminants in the Aquatic Environment)
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21 pages, 3431 KiB  
Article
Fish Community Responses to Human-Induced Stresses in the Lower Mekong Basin
by Vanna Nuon, Sovan Lek, Peng Bun Ngor, Nam So and Gaël Grenouillet
Water 2020, 12(12), 3522; https://doi.org/10.3390/w12123522 - 15 Dec 2020
Cited by 16 | Viewed by 5338
Abstract
The Mekong River is one of the world’s largest rivers and has an annual captured fish production of about 2.3 million tonnes, equivalent to around 11 billion USD. Although the Mekong provides important ecological and socioeconomic benefits to millions of people, it is [...] Read more.
The Mekong River is one of the world’s largest rivers and has an annual captured fish production of about 2.3 million tonnes, equivalent to around 11 billion USD. Although the Mekong provides important ecological and socioeconomic benefits to millions of people, it is facing intensive change due to anthropogenic stressors. Therefore, it is necessary to understand the changes to the spatiotemporal fish communities to inform sustainable fisheries management. Here, we aimed to characterize patterns of the fish communities and identify the ecological status of each fish community using daily catch data from 2007 to 2018 at 25 monitoring sites in the Lower Mekong Basin (LMB). The collected data were classified by a self-organizing map into four main groups. Group 4 represented the lower Vietnam Mekong Delta (VMD), while groups 1, 2, and 3 were subdivided into subgroups 1a (upper LMB), 1b (upper and middle LMB), 2a (Mekong River below the Khone Falls and Sesan River), 2b (Mekong River below the Khone Falls and Sekong, Sesan and Srepok (3S) Rivers), 3a (Floodplain-Tonle Sap and Songkhram) and 3b (upper VMD). Among the 571 species recorded, 119 were identified as indicator species. Based on the abundance and biomass comparison curves, the fish community of 2b was in a healthier condition with a positive W-statistic value while the rest had a negative W-statistic value. The highest species richness and diversity were observed in 3a and 2b, so these subgroups deserve high management and conservation priority. Likewise, 1a should also be considered as a high priority area since it harbors several endangered and long-distant migratory fishes. It was also noticed that the fish communities of groups 3 and 4, located far from the hydropower dams, remained mostly unchanged compared to those of groups 1 and 2, close to the mainstream and tributary dams in the upper LMB and 3S Rivers. 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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40 pages, 3951 KiB  
Review
Organic Matter Decomposition and Ecosystem Metabolism as Tools to Assess the Functional Integrity of Streams and Rivers–A Systematic Review
by Verónica Ferreira, Arturo Elosegi, Scott D. Tiegs, Daniel von Schiller and Roger Young
Water 2020, 12(12), 3523; https://doi.org/10.3390/w12123523 - 15 Dec 2020
Cited by 56 | Viewed by 14730
Abstract
Streams and rivers provide important services to humans, and therefore, their ecological integrity should be a societal goal. Although ecological integrity encompasses structural and functional integrity, stream bioassessment rarely considers ecosystem functioning. Organic matter decomposition and ecosystem metabolism are prime candidate indicators of [...] Read more.
Streams and rivers provide important services to humans, and therefore, their ecological integrity should be a societal goal. Although ecological integrity encompasses structural and functional integrity, stream bioassessment rarely considers ecosystem functioning. Organic matter decomposition and ecosystem metabolism are prime candidate indicators of stream functional integrity, and here we review each of these functions, the methods used for their determination, and their strengths and limitations for bioassessment. We also provide a systematic review of studies that have addressed organic matter decomposition (88 studies) and ecosystem metabolism (50 studies) for stream bioassessment since the year 2000. Most studies were conducted in temperate regions. Bioassessment based on organic matter decomposition mostly used leaf litter in coarse-mesh bags, but fine-mesh bags were also common, and cotton strips and wood were frequent in New Zealand. Ecosystem metabolism was most often based on the open-channel method and used a single-station approach. Organic matter decomposition and ecosystem metabolism performed well at detecting environmental change (≈75% studies), with performances varying between 50 and 100% depending on the type of environmental change; both functions were sensitive to restoration practices in 100% of the studies examined. Finally, we provide examples where functional tools are used to complement the assessments of stream ecological integrity. With this review, we hope to facilitate the widespread incorporation of ecosystem processes into bioassessment programs with the broader aim of more effectively managing stream and river ecosystems. Full article
(This article belongs to the Special Issue The Ecological Assessment of Rivers and Estuaries: Present and Future)
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20 pages, 6226 KiB  
Article
Evaluation of AnnAGNPS Model for Runoff Simulation on Watersheds from Glaciated Landscape of USA Midwest and Northeast
by Marzia Tamanna, Soni M. Pradhanang, Arthur J. Gold, Kelly Addy, Philippe G. Vidon and Ronald L. Bingner
Water 2020, 12(12), 3525; https://doi.org/10.3390/w12123525 - 15 Dec 2020
Cited by 10 | Viewed by 4965
Abstract
Runoff modeling of glaciated watersheds is required to predict runoff for water supply, aquatic ecosystem management and flood prediction, and to deal with questions concerning the impact of climate and land use change on the hydrological system and watershed export of contaminants of [...] Read more.
Runoff modeling of glaciated watersheds is required to predict runoff for water supply, aquatic ecosystem management and flood prediction, and to deal with questions concerning the impact of climate and land use change on the hydrological system and watershed export of contaminants of glaciated watersheds. A widely used pollutant loading model, Annualized Agricultural Non-Point Source Pollution (AnnAGNPS) was applied to simulate runoff from three watersheds in glaciated geomorphic settings. The objective of this study was to evaluate the suitability of the AnnAGNPS model in glaciated landscapes for the prediction of runoff volume. The study area included Sugar Creek watershed, Indiana; Fall Creek watershed, New York; and Pawcatuck River watershed, Rhode Island, USA. The AnnAGNPS model was developed, calibrated and validated for runoff estimation for these watersheds. The daily and monthly calibration and validation statistics (NSE > 0.50 and RSR < 0.70, and PBIAS ± 25%) of the developed model were satisfactory for runoff simulation for all the studied watersheds. Once AnnAGNPS successfully simulated runoff, a parameter sensitivity analysis was carried out for runoff simulation in all three watersheds. The output from our hydrological models applied to glaciated areas will provide the capacity to couple edge-of-field hydrologic modeling with the examination of riparian or riverine functions and behaviors. Full article
(This article belongs to the Special Issue Hydrological Processes in Small Catchments—Runoff and Sediment Yield in Changing Environment)
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22 pages, 4277 KiB  
Article
Quality and Health Risk Assessment Associated with Water Consumption—A Case Study on Karstic Springs
by Ana Moldovan, Maria-Alexandra Hoaghia, Eniko Kovacs, Ionuț Cornel Mirea, Marius Kenesz, Răzvan Adrian Arghir, Alexandru Petculescu, Erika Andrea Levei and Oana Teodora Moldovan
Water 2020, 12(12), 3510; https://doi.org/10.3390/w12123510 - 14 Dec 2020
Cited by 50 | Viewed by 5883
Abstract
In rural areas without centralized water supply systems, inhabitants often use groundwater of unknown quality as drinking water, without understanding the possible negative consequences on their health. Karstic spring waters from Dobrogea region in Romania were assessed for their potential to be used [...] Read more.
In rural areas without centralized water supply systems, inhabitants often use groundwater of unknown quality as drinking water, without understanding the possible negative consequences on their health. Karstic spring waters from Dobrogea region in Romania were assessed for their potential to be used as drinking water source, according to their quality and seasonal variation. The physico-chemical parameters of waters were compared with the guideline values for drinking water established by the World Health Organization and the Directive 98/83/EC. The nitrate and Cr concentrations exceeded the guideline value in the springs from Southern Dobrogea, but met the quality criteria in those from Northern Dobrogea, thus, to be used as drinking water, the karstic springs located in Southern Dobrogea require treatment for nitrates removal. Heavy metals pollution indices showed low to medium cumulative heavy metal pollution in all springs, while the human health risk assessment by oral exposure indicated possible noncarcinogenic risks of nitrates, both for adults and children in springs from South Dobrogea. A rigorous monitoring of the water quality before human consumption is recommended for all four studied water sources. Full article
(This article belongs to the Special Issue Research on Karst Eco-Hydrology and Sediment)
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12 pages, 1207 KiB  
Article
Dissolved Organic Matter in Continental Hydro-Geothermal Systems: Insights from Two Hot Springs of the East African Rift Valley
by Andrea Butturini, Stefano Amalfitano, Peter Herzsprung, Oliver J. Lechtenfeld, Stefania Venturi, Lydia A. Olaka, Nic Pacini, David M. Harper, Franco Tassi and Stefano Fazi
Water 2020, 12(12), 3512; https://doi.org/10.3390/w12123512 - 14 Dec 2020
Cited by 6 | Viewed by 3356
Abstract
Little is known about the quantity and quality of dissolved organic matter (DOM) in waters from continental geothermal systems, with only a few reports available from the Yellowstone US National Park. In this study, we explored the chemodiversity of DOM in water samples [...] Read more.
Little is known about the quantity and quality of dissolved organic matter (DOM) in waters from continental geothermal systems, with only a few reports available from the Yellowstone US National Park. In this study, we explored the chemodiversity of DOM in water samples collected from two geothermal hot springs from the Kenyan East African Rift Valley, a region extremely rich in fumaroles, geysers, and spouting springs, located in close proximity to volcanic lakes. The DOM characterization included in-depth assessments performed by negative electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Reduced, saturated and little aromatic DOM compounds were dominant in the hot spring waters collected from either the Ol Njorowa gorge (ON) or the south shore of the soda-saline Lake Elementaita (ELM). Oxygen-poor and sulfur-bearing DOM molecules prevailed in ON, probably reflecting abiotic sulfurization from sulfide-rich geofluids. Nitrogen-bearing aliphatic and protein-like molecules were abundant in ELM, possibly perfusing through the organic-rich sediments of the adjacent Lake Elementaita. Notably, the heat-altered DOM of ancient autochthonous derivation could represent an overlooked source of aliphatic organic carbon for connected lentic environments, with a potential direct impact on nutrient cycling in lakes that receive geothermal water inputs. Full article
(This article belongs to the Special Issue Dissolved Organic Matter Dynamics in Groundwater, Rivers, and Lakes)
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21 pages, 9458 KiB  
Article
Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators
by Elena Gershelis, Andrey Grinko, Irina Oberemok, Elizaveta Klevantseva, Natalina Poltavskaya, Alexey Ruban, Denis Chernykh, Andrey Leonov, Natalia Guseva and Igor Semiletov
Water 2020, 12(12), 3511; https://doi.org/10.3390/w12123511 - 14 Dec 2020
Cited by 8 | Viewed by 3639
Abstract
Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback [...] Read more.
Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper. Full article
(This article belongs to the Special Issue Geochemistry of Water and Sediment)
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26 pages, 6313 KiB  
Article
Observations of Nearbed Turbulence over Mobile Bedforms in Combined, Collinear Wave-Current Flows
by Hachem Kassem, Charlotte E. L. Thompson, Carl L. Amos, Ian H. Townend, David Todd, Richard J. S. Whitehouse and Elizabeth Chellew
Water 2020, 12(12), 3515; https://doi.org/10.3390/w12123515 - 14 Dec 2020
Cited by 2 | Viewed by 3178
Abstract
Collinear wave-current shear interactions are often assumed to be the same for currents following or opposing the direction of regular wave propagation; with momentum and mass exchanges restricted to the thin oscillating boundary layer (zero-flux condition) and enhanced but equal wave-averaged bed shear [...] Read more.
Collinear wave-current shear interactions are often assumed to be the same for currents following or opposing the direction of regular wave propagation; with momentum and mass exchanges restricted to the thin oscillating boundary layer (zero-flux condition) and enhanced but equal wave-averaged bed shear stresses. To examine these assumptions, a prototype-scale experiment investigated the nature of turbulent exchanges in flows with currents aligned to, and opposing, wave propagation over a mobile sandy bed. Estimated mean and maximum stresses from measurements above the bed exceeded predictions by models of bed shear stress subscribing to the assumptions above, suggesting the combined boundary layer is larger than predicted by theory. The core flow experiences upward turbulent fluxes in aligned flows, coupled with sediment entrainment by vortex shedding at flow reversal, whilst downward fluxes of eddies generated by the core flow, and strong adverse shear can enhance near-bed mass transport, in opposing currents. Current-aligned coherent structures contribute significantly to the stress and energy dissipation, and display characteristics of wall-attached eddies formed by the pairing of counter-rotating vortices. These preliminary findings suggest a notable difference in wave-following and wave-opposing wave-current interactions, and highlight the need to account for intermittent momentum-exchanges in predicting stress, boundary layer thickness and sediment transport. Full article
(This article belongs to the Special Issue Sediment Transport in Coastal Waters 2.0)
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25 pages, 8769 KiB  
Article
Assessment of Hydrology and Sediment Yield in the Mekong River Basin Using SWAT Model
by Ty Sok, Chantha Oeurng, Ilan Ich, Sabine Sauvage and José Miguel Sánchez-Pérez
Water 2020, 12(12), 3503; https://doi.org/10.3390/w12123503 - 13 Dec 2020
Cited by 35 | Viewed by 7020
Abstract
The Mekong River Basin (MRB) in Southeast Asia is among the world’s ten largest rivers, both in terms of its discharge and sediment load. The spatial and temporal resolution to accurately determine the sediment load/yield from tributaries and sub-basin that enters the Mekong [...] Read more.
The Mekong River Basin (MRB) in Southeast Asia is among the world’s ten largest rivers, both in terms of its discharge and sediment load. The spatial and temporal resolution to accurately determine the sediment load/yield from tributaries and sub-basin that enters the Mekong mainstream still lacks from the large-scale model. In this study, the SWAT model was applied to the MRB to assess long-term basin hydrology and to quantify the sediment load and spatial sediment yield in the MRB. The model was calibrated and validated (1985–2016) at a monthly time step. The overall proportions of streamflow in the Mekong River were 34% from surface runoff, 21% from lateral flow, 45% from groundwater contribution. The average annual sediments yield presented 1295 t/km2/year in the upper part of the basin, 218 t/km2/year in the middle, 78 t/km2/year in the intensive agricultural area and 138 t/km2/year in the highland area in the lower part. The annual average sediment yield for the Mekong River was 310 t/km2/year from upper 80% of the total MRB before entering the delta. The derived sediment yield and a spatial soil erosion map can explicitly illustrate the identification and prioritization of the critical soil erosion-prone areas of the MR sub-basins. Full article
(This article belongs to the Special Issue Fluvial Processes and Denudation)
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16 pages, 1224 KiB  
Article
Carbon Fixation Trends in Eleven of the World’s Largest Lakes: 2003–2018
by Michael Sayers, Karl Bosse, Gary Fahnenstiel and Robert Shuchman
Water 2020, 12(12), 3500; https://doi.org/10.3390/w12123500 - 12 Dec 2020
Cited by 20 | Viewed by 5682
Abstract
Large freshwater lakes provide immense value to the surrounding populations, yet there is limited understanding of how these lakes will respond to climate change and other factors. This study uses satellite remote sensing to estimate annual, lake-wide primary production in 11 of the [...] Read more.
Large freshwater lakes provide immense value to the surrounding populations, yet there is limited understanding of how these lakes will respond to climate change and other factors. This study uses satellite remote sensing to estimate annual, lake-wide primary production in 11 of the world’s largest lakes from 2003–2018. These lakes include the five Laurentian Great Lakes, the three African Great Lakes, Lake Baikal, and Great Bear and Great Slave Lakes. Mean annual production in these lakes ranged from under 200 mgC/m2/day to over 1100 mgC/m2/day, and the lakes were placed into one of three distinct groups (oligotrophic, mesotrophic, or eutrophic) based on their level of production. The analysis revealed only three lakes with significant production trends over the study period, with increases in Great Bear Lake (24% increase over the study period) and Great Slave Lake (27%) and a decline in Lake Tanganyika (−16%). These changes appear to be related to climate change, including increasing temperatures and solar radiation and decreasing wind speeds. This study is the first to use consistent methodology to study primary production in the world’s largest lakes, allowing for these novel between-lake comparisons and assessment of inter-annual trends. Full article
(This article belongs to the Special Issue The Impact of Environmental Stressors on Carbon Dynamics in the Aquatic System)
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27 pages, 65014 KiB  
Article
Trophic Niches, Trophic Positions, and Niche Overlaps between Non-Native and Native Fish Species in a Subalpine Lake
by Davide Cicala, Gianluca Polgar, Jordi René Mor, Roberta Piscia, Stefano Brignone, Silvia Zaupa and Pietro Volta
Water 2020, 12(12), 3475; https://doi.org/10.3390/w12123475 - 10 Dec 2020
Cited by 15 | Viewed by 6825
Abstract
In the last century, Italian freshwater ecosystems have been invaded by several non-native fish species. In the subalpine Lake Mergozzo (northern Italy), several recently introduced non-native species dramatically expanded their populations. We used carbon and nitrogen stable isotopes to describe the isotopic niches [...] Read more.
In the last century, Italian freshwater ecosystems have been invaded by several non-native fish species. In the subalpine Lake Mergozzo (northern Italy), several recently introduced non-native species dramatically expanded their populations. We used carbon and nitrogen stable isotopes to describe the isotopic niches and trophic positions of native and non-native fish species in Lake Mergozzo. We evaluated their trophic niches, trophic diversity, trophic redundancy and trophic evenness utilizing isotopic niche metrics, and estimated asymmetrical niche overlaps. The trophic traits of non-native fish species and Perca fluviatilis clearly define them as trophic generalists, in terms of among-individual variability of their isotopic niches. The historical increase in abundance of fish non-native species in this lake, their dominance by numbers and biomass within the assemblage, and their broad asymmetrical niche overlaps suggest that their higher degree of trophic generalism might have been one of the key factors that have promoted the invasion of the recipient community. Full article
(This article belongs to the Special Issue Biological Invasions in Changing Aquatic Ecosystems: Future Perspectives)
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24 pages, 11060 KiB  
Article
Natural and Anthropogenic Groundwater Contamination in a Coastal Volcanic-Sedimentary Aquifer: The Case of the Archaeological Site of Cumae (Phlegraean Fields, Southern Italy)
by Luisa Stellato, Silvio Coda, Michele Arienzo, Pantaleone De Vita, Brunella Di Rienzo, Antonio D’Onofrio, Luciano Ferrara, Fabio Marzaioli, Marco Trifuoggi and Vincenzo Allocca
Water 2020, 12(12), 3463; https://doi.org/10.3390/w12123463 - 9 Dec 2020
Cited by 20 | Viewed by 4669
Abstract
Archeological sites close to coastal volcanic-sedimentary aquifers are threatened by groundwater contaminated by natural and anthropogenic processes. The paper reports on a hydrogeological, chemical (major, minor and trace elements) and isotopic (δD-H2O, δ18O-H2O, δ15N-NO3 [...] Read more.
Archeological sites close to coastal volcanic-sedimentary aquifers are threatened by groundwater contaminated by natural and anthropogenic processes. The paper reports on a hydrogeological, chemical (major, minor and trace elements) and isotopic (δD-H2O, δ18O-H2O, δ15N-NO3, δ18O-NO3, δ11B, 222Rn) survey of groundwater at the Cumae archaeological site, which is located in the coastal north-western sector of the volcanic district of Phlegraean Fields (southern Italy), where groundwater flooding phenomena occur. Results show the presence of a complex coastal volcanic-sedimentary aquifer system where groundwater quality is influenced mainly by: (i) aquifer lithology and localized ascent of magmatic fluids along buried volcano-tectonic discontinuities, (ii) mixing of groundwater, deep mineralized fluids and seawater during groundwater pumping, and (iii) nitrate contamination >50 mg/L from non-point agricultural sources. Moreover, δD and δ18O point toward fast recharge from seasonal precipitations, while the isotopic ratios of N and O in nitrate reveal the contribution of mineral and organic fertilizers as well as leakage from septic tanks. Results can assist the local archaeological authority for the safeguarding and management of the archaeological heritage of the Cumae site. Full article
(This article belongs to the Special Issue Focus on the Salinization Issue in the Mediterranean Area)
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35 pages, 6301 KiB  
Article
A Framework for Sustainable Planning and Decision-Making on Resource Recovery from Wastewater: Showcase for São Paulo Megacity
by Mariana C. Chrispim, Fernanda de M. de Souza, Miklas Scholz and Marcelo A. Nolasco
Water 2020, 12(12), 3466; https://doi.org/10.3390/w12123466 - 9 Dec 2020
Cited by 21 | Viewed by 7054
Abstract
Currently, it is important to develop strategic frameworks to support the selection of sustainable resource recovery solutions. This study applies a new framework for planning, implementation, and assessment of resource recovery strategies for a full-scale wastewater treatment plant (WWTP) in São Paulo megacity. [...] Read more.
Currently, it is important to develop strategic frameworks to support the selection of sustainable resource recovery solutions. This study applies a new framework for planning, implementation, and assessment of resource recovery strategies for a full-scale wastewater treatment plant (WWTP) in São Paulo megacity. The framework comprises several steps based on case study-specific data and information from current literature. Data were collected from various sources: a survey with a wastewater treatment utility, national and regional databases, and review of local regulations and international literature. Treatment configuration, wastewater and by-products composition, potential demand (for water, energy, and phosphorus), stakeholder identification, and local legislation were thoroughly discussed regarding decision-making on resource recovery. Scenario analysis was used to explore suitable nutrient and energy recovery measures based on indicators. Biogas recovery and sewage sludge composting showed more favorable conditions due to similar experiences in the area and robust legislation. The proposed framework is a simplified tool, and its application can support managers to get information on resource recovery and how to plan such initiatives in easier ways to facilitate wiser decision-making, and better operation and management. The results on framework use and refinement can guide potential applications in other contexts and stimulate public policy formulation and further research. Full article
(This article belongs to the Special Issue Application of Circular Economy Principles in Water and Wastewater Utilities)
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22 pages, 1514 KiB  
Article
Integrated Assessment—How Does It Help Unpack Water Access by Marginalized Farmers?
by Serena H. Hamilton, Wendy S. Merritt, Mahanambrota Das, M. Wakilur Rahman, Sumana S. Bhuiya, Lucy Carter, Michaela Cosijn, Christian H. Roth, Sambhu Singha and Geoffrey J. Syme
Water 2020, 12(12), 3444; https://doi.org/10.3390/w12123444 - 8 Dec 2020
Cited by 3 | Viewed by 3021
Abstract
Water is critical to the lives and livelihoods of rural communities in developing countries; however, access to water can be inequitable within communities. This paper uses a generalized integrated assessment approach to explore the determinants of water access by marginalized farmers in two [...] Read more.
Water is critical to the lives and livelihoods of rural communities in developing countries; however, access to water can be inequitable within communities. This paper uses a generalized integrated assessment approach to explore the determinants of water access by marginalized farmers in two villages in coastal Bangladesh, before and after the setup of local water institutions. The study was part of a broader project aimed at promoting socially inclusive agricultural intensification. An integrative framework was developed in this study to capture and link the diverse range of factors that influence the distribution of water, including the often-overlooked role of social dynamics and governance arrangements. While interventions around improving water resource infrastructure can be critical for freshwater availability, the case studies show that a breakdown of asymmetric power structures may also be needed for water access to all individuals, especially marginalized groups. Establishing a community-based water institution on its own does not necessarily address power issues in a community. It is imperative that the agency and capacities of the marginalized members are developed and that the institutional arrangements foster an enabling environment for marginalized members to influence decision making. Integrated assessment allowed the case studies to be explored from multiple perspectives so as to gain a greater understanding of the barriers and levers to obtaining equitable outcomes from water interventions. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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