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Volume 12
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Water, Volume 12, Issue 2 (February 2020) – 307 articles

Cover Story (view full-size image): Phosphorus (P) removal structures are an edge-of-field practice for removing dissolved P from flowing water that comes from soils built-up with excessive P concentrations (i.e. legacy soils). These landscape-scale filters contain P sorption materials (PSMs) that sorb P by various reactions. Already proven effective, current research is dedicated to increasing efficiency and decreasing cost of structures. Cover photo shows a 35 Mg slag subsurface P removal structure for treating agricultural tile drainage with flow from the bottom-up. The structure handled 12 L s-1 flow and removed 19 kg (55%) of the cumulative dissolved P load. View this paper.
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24 pages, 11505 KiB  
Article
Topographic Effects on Three-Dimensional Slope Stability for Fluctuating Water Conditions Using Numerical Analysis
by Yue Zhou, Shun-Chao Qi, Gang Fan, Ming-Liang Chen and Jia-Wen Zhou
Water 2020, 12(2), 615; https://doi.org/10.3390/w12020615 - 24 Feb 2020
Cited by 7 | Viewed by 4338
Abstract
With recent advances in calculation methods, the external factors that affect slope stability, such as water content fluctuations and self-configuration, can be more easily assessed. In this study, a three-dimensional finite element strength reduction method was used to analyze the stability of three-dimensional [...] Read more.
With recent advances in calculation methods, the external factors that affect slope stability, such as water content fluctuations and self-configuration, can be more easily assessed. In this study, a three-dimensional finite element strength reduction method was used to analyze the stability of three-dimensional slopes under fluctuating water conditions. Based on soil parameter variations in engineering practice, the calculation models were established using heterogeneous layers, including a cover layer with inferior properties. An analysis of seepage, deformation and slope stability was carried out with 27 different models, including three different slope gradients and nine different corner angles under five different hydraulic conditions. The failure mechanism has been shown to be closely related to the change in matric suction of unsaturated soils and the geometric slope configuration. Finally, the effect of geometry (surface shape, turning corner and slope gradient) and water (fluctuations) on slope stability are discussed in detail. Emphasis is given to comparing safety factors obtained considering or ignoring matric suction. Full article
(This article belongs to the Special Issue Water-Induced Landslides: Prediction and Control)
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21 pages, 9536 KiB  
Article
Importance of Precipitation on the Upper Ocean Salinity Response to Typhoon Kalmaegi (2014)
by Fu Liu, Han Zhang, Jie Ming, Jiayu Zheng, Di Tian and Dake Chen
Water 2020, 12(2), 614; https://doi.org/10.3390/w12020614 - 24 Feb 2020
Cited by 17 | Viewed by 3958
Abstract
Using multiple-satellite datasets, in situ observations, and numerical simulations, the influence of typhoon-induced precipitation on the oceanic response to Typhoon Kalmaegi has been discussed. It is found that the convective system and precipitation distribution of Kalmaegi was asymmetric, which leaded to the asymmetric [...] Read more.
Using multiple-satellite datasets, in situ observations, and numerical simulations, the influence of typhoon-induced precipitation on the oceanic response to Typhoon Kalmaegi has been discussed. It is found that the convective system and precipitation distribution of Kalmaegi was asymmetric, which leaded to the asymmetric rainfall at observational stations. The sea surface salinity (SSS) of the buoy to the right of storm track increased with a 0.176 practical salinity units (psu) maximal positive anomaly, while the two buoys on the left side underwent several desalination processes, with a maximum decreases of 0.145 psu and 0.278 psu. Numerical simulations with and without precipitation forcing were also performed. Model results showed that typhoon-induced precipitation can weaken sea surface cooling by approximately 0.03–0.40 °C and suppress the SSS increase by approximately 0.074–0.152 psu. The effect of precipitation can be divided into the direct effect and indirect effect. On one hand, freshwater from precipitation directly dilutes the salinity. On the other hand, when salinity decreases, the ocean stratification will be enhanced, the vertical mixing will be restrained, and then the temperature and salinity can be further affected by weakened vertical mixing. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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19 pages, 5226 KiB  
Article
Ubiquitous Fractal Scaling and Filtering Behavior of Hydrologic Fluxes and Storages from A Mountain Headwater Catchment
by Ravindra Dwivedi, John F. Knowles, Christopher Eastoe, Rebecca Minor, Nathan Abramson, Bhaskar Mitra, William E. Wright, Jennifer McIntosh, Thomas Meixner, Paul A. “Ty” Ferre, Christopher Castro, Guo-Yue Niu, Greg A. Barron-Gafford, Michael Stanley and Jon Chorover
Water 2020, 12(2), 613; https://doi.org/10.3390/w12020613 - 24 Feb 2020
Cited by 2 | Viewed by 3159
Abstract
We used the weighted wavelet method to perform spectral analysis of observed long-term precipitation, streamflow, actual evapotranspiration, and soil water storage at a sub-humid mountain catchment near Tucson, Arizona, USA. Fractal scaling in precipitation and the daily change in soil water storage occurred [...] Read more.
We used the weighted wavelet method to perform spectral analysis of observed long-term precipitation, streamflow, actual evapotranspiration, and soil water storage at a sub-humid mountain catchment near Tucson, Arizona, USA. Fractal scaling in precipitation and the daily change in soil water storage occurred up to a period of 14 days and corresponded to the typical duration of relatively wet and dry intervals. In contrast, fractal scaling could be observed up to a period of 0.5 years in streamflow and actual evapotranspiration. By considering long-term observations of hydrologic fluxes and storages, we show that, in contrast to previous findings, the phase relationships between water balance components changed with component period and were not perfectly in or out of phase at all periods. Self-averaging behavior was apparent, but the temporal scales over which this behavior was applicable differed among the various water balance components. Conservative tracer analysis showed that this catchment acted as a fractal filter by transforming white noise in the precipitation input signal to a 1/f flicker in the streamflow output signal by means of both spatial and temporal subsurface advection and dispersion processes and soil wetting properties. This study provides an improved understanding of hydrological filtering behavior in mountain critical zones that are critical sources of water and ecosystem services throughout the world. Full article
(This article belongs to the Special Issue Catchments as Observatories of the Hydrological and Biogeochemical Functioning of the Critical Zone)
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12 pages, 9517 KiB  
Article
Marine Litter in Transitional Water Ecosystems: State of The Art Review Based on a Bibliometric Analysis
by Monia Renzi, Valentina H. Pauna, Francesca Provenza, Cristina Munari and Michele Mistri
Water 2020, 12(2), 612; https://doi.org/10.3390/w12020612 - 24 Feb 2020
Cited by 15 | Viewed by 3899
Abstract
Transitional water ecosystems (TWEs), despite their ecological and economic importance, are largely affected by human pressures that could be responsible for significant inputs of litter in the marine environment. Plastic input in coastal ponds, lagoons, river deltas and estuaries, could be driven by [...] Read more.
Transitional water ecosystems (TWEs), despite their ecological and economic importance, are largely affected by human pressures that could be responsible for significant inputs of litter in the marine environment. Plastic input in coastal ponds, lagoons, river deltas and estuaries, could be driven by a wide range of human activities such as agriculture, waste disposal, municipal and industrial wastewater effluents, aquaculture, fishing and touristic activities and urban impacts. However, it remains unknown what the impact of plastic input in these TWEs could have on natural capital and, therefore, the ability for an ecosystem to provide goods and services to human beings. Given the large interest with regards to the conservation of transitional water ecosystems and the clear exposure risk to plastic and microplastic pollution, this study aims to perform: (i) a bibliometric analyses on existing literature regarding the levels of marine litter in such environments; (ii) a selection among the available literature of homogeneous data; and (iii) statistical analyses to explore data variability. Results suggest that: (i) research on microplastics in these ecosystems did not begin to be published until 2013 for lagoons, 2014 for river mouths and 2019 for coastal ponds. The majority of articles published on studies of microplastics in lagoons did not occur until 2019; (ii) sediments represent the matrix on which sampling and extraction variability allow the statistical analyses on data reported by the literature; (iii) the Analysis of Similarities (ANOSIM) test two-way evidenced that the level of protection of marine and terrestrial areas produced similar values while the habitat type showed low significance in terms of its effect on microplastic levels, shape and size in sediments. Full article
(This article belongs to the Section Water Quality and Contamination)
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18 pages, 32267 KiB  
Article
Impact of Sea Ice on the Hydrodynamics and Suspended Sediment Concentration in the Coastal Waters of Qinhuangdao, China
by Man Jiang, Chongguang Pang, Zhiliang Liu and Jingbo Jiang
Water 2020, 12(2), 611; https://doi.org/10.3390/w12020611 - 24 Feb 2020
Viewed by 2811
Abstract
The influence of sea ice on the hydrodynamics, sediment resuspension, and suspended sediment concentration (SSC) in the coastal area of Qinhuangdao was systematically investigated using 45-day in situ measurements at two stations (with ice at station M1 and without ice at station M2) [...] Read more.
The influence of sea ice on the hydrodynamics, sediment resuspension, and suspended sediment concentration (SSC) in the coastal area of Qinhuangdao was systematically investigated using 45-day in situ measurements at two stations (with ice at station M1 and without ice at station M2) in the Bohai Sea in the winter of 2018. It was found that the daily fluctuations of temperature and salinity at M1 are more significant than those at M2. During a typical seawater icing event on January 28, the temperature and salinity of the bottom water at M1 were decreased by 1.77 °C and increased by 0.4 psu, respectively. Moreover, due to the shielding effect of the sea ice, the residual current was much less affected by the wind at M1 than at M2. For the vertical distribution of current velocity, it changed from a traditional logarithmic type under ice-free conditions to parabolic type under ice-covered conditions due to the larger drag coefficient of the water body on the solid ice surface. For the SSC and turbidity at the bottom layer, the average values were 4.9 μL/L and 8.6 NTU at M1, respectively, approximately half of those at M2. The smaller SSC and turbidity at M1 can be attributed to the lower near-bottom turbulent kinetic energy (TKE). At M2, however, the larger SSC is closely related to the strong wind forcing, which could induce higher TKE without sea ice cover, and hence stronger turbulent resuspension. The seabed sediment analysis results showed that in the study area, fine sand is most likely to resuspend, while cohesive particles would resuspend only under strong hydrodynamic conditions. Full article
(This article belongs to the Special Issue Observation and Numerical Modeling of Sediment Transport in Coastal Areas)
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14 pages, 2427 KiB  
Article
Revisiting the Statistical Scaling of Annual Discharge Maxima at Daily Resolution with Respect to the Basin Size in the Light of Rainfall Climatology
by Anastasios Perdios and Andreas Langousis
Water 2020, 12(2), 610; https://doi.org/10.3390/w12020610 - 24 Feb 2020
Cited by 7 | Viewed by 3385
Abstract
Over the years, several studies have been carried out to investigate how the statistics of annual discharge maxima vary with the size of basins, with diverse findings regarding the observed type of scaling (i.e., simple scaling vs. multiscaling), especially in cases where the [...] Read more.
Over the years, several studies have been carried out to investigate how the statistics of annual discharge maxima vary with the size of basins, with diverse findings regarding the observed type of scaling (i.e., simple scaling vs. multiscaling), especially in cases where the data originated from regions with significantly different hydroclimatic characteristics. In this context, an important question arises on how one can effectively conclude on an approximate type of statistical scaling of annual discharge maxima with respect to the basin size. The present study aims at addressing this question, using daily discharges from 805 catchments located in different parts of the United Kingdom, with at least 30 years of recordings. To do so, we isolate the effects of the catchment area and the local rainfall climatology, and examine how the statistics of the standardized discharge maxima vary with the basin scale. The obtained results show that: (a) the local rainfall climatology is an important contributor to the observed statistics of peak annual discharges, and (b) when the effects of the local rainfall climatology are properly isolated, the scaling of the standardized annual discharge maxima with the area of the catchment closely follows that commonly met in actual rainfields, deviating significantly from the simple scaling rule. The aforementioned findings explain to a large extent the diverse results obtained by previous studies in the absence of rainfall information, shedding light on the approximate type of scaling of annual discharge maxima with the basin size. Full article
(This article belongs to the Special Issue Techniques for Mapping and Assessing Surface Runoff)
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19 pages, 7533 KiB  
Article
A Borehole-Based Approach for Seawater Intrusion in Heterogeneous Coastal Aquifers, Eastern Part of Jeju Island, Korea
by Jehyun Shin and Seho Hwang
Water 2020, 12(2), 609; https://doi.org/10.3390/w12020609 - 24 Feb 2020
Cited by 15 | Viewed by 4139
Abstract
Understanding the basaltic aquifer system and seawater intrusion on the volcanic island of Jeju, Korea, has received significant attention over the years, and various methodologies have been suggested in the contributions. Nevertheless, it is still difficult to effectively characterize groundwater systems due to [...] Read more.
Understanding the basaltic aquifer system and seawater intrusion on the volcanic island of Jeju, Korea, has received significant attention over the years, and various methodologies have been suggested in the contributions. Nevertheless, it is still difficult to effectively characterize groundwater systems due to the long period of volcanic activity and the lithological variability of basalt. In this study, geophysical well logging in seawater intrusion monitoring boreholes detected a sudden decrease of electrical conductivity within the saltwater zone in the eastern part of Jeju Island. This anomalous condition cannot be explained by the Ghyben-Herzberg model, which has historically been considered as the basic groundwater model of Jeju Island. This paper focuses on fine-scale temporal and spatial variability of groundwater flow using electrical conductivity and temperature logs and borehole temperature monitoring by a thermal line sensor. On the basis of the results, we evaluate an alternative model to replace the traditional conceptual model in the eastern part of Jeju Island. It is revealed that the area consists of heterogeneous aquifer systems, and the behavior of freshwater and saltwater is understood by temperature monitoring over the entire depth of boreholes. Coastal aquifers flow through two or more independent channels with weak vertical connections. In addition, seawater intrusion does not occur continuously in the vertical direction from the bottom depth, but instead occurs through these multilayered aquifers. In particular, the multilayered aquifers that are responsible for flow pathway, as well as the freshwater–saltwater interface form mainly at lithological boundaries. Our preliminary conceptual model is expected to be improved and revised by various measurements of hydrodynamic parameters such as flowmeter or packer test. Full article
(This article belongs to the Section Hydrology)
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17 pages, 15097 KiB  
Article
An Integrated Urban Flood Vulnerability Index for Sustainable Planning in Arid Zones of Developing Countries
by Carlos Salazar-Briones, José Mizael Ruiz-Gibert, Marcelo A. Lomelí-Banda and Alejandro Mungaray-Moctezuma
Water 2020, 12(2), 608; https://doi.org/10.3390/w12020608 - 24 Feb 2020
Cited by 30 | Viewed by 6417
Abstract
Floods are among the most recurring and devastating natural hazards, impacting human lives and causing severe economic damage. Urbanization can increase the risk of flooding due to increased peak discharge and volume. Over arid urban areas of developing countries, flood disaster management is [...] Read more.
Floods are among the most recurring and devastating natural hazards, impacting human lives and causing severe economic damage. Urbanization can increase the risk of flooding due to increased peak discharge and volume. Over arid urban areas of developing countries, flood disaster management is reactive, responding to prevailing disaster situations, mainly because of the lack of budget, equipment, facilities, and human resources. The approach required in a new city requires a different operative planning process, ruled by different kinds of specific indicators to be incorporated in the sustainable planning process. This study focuses on an approach to assess flood vulnerability as a planning tool using an integrated flood vulnerability index (FVI) with variables that are accessible in developing countries and arid urban areas. The research took place in the city of Mexicali, Baja, California. México. This index was determined by coupling the variables of three components: social, economic, and physical. The FVI reflects the status of an urban scale’s vulnerability. Variables were obtained from government data for the social and economic components, and a hydrological and hydraulic model approach as a physical component. The correlation of each variable to the flood was taken into account by using a general linear transformation. GIS was used as a tool for the development of spatial analysis. The results showed the spatial distribution of vulnerability at an urban district scale. It was found that 55% of the population is exposed to a vulnerability above the average value of the urban area. Integrating all the components will help decision-makers to implement strategies to improve the resilience of the area by attending the needs of the particular component that is more vulnerable. Full article
(This article belongs to the Special Issue Integrated Flood Management: Concepts, Methods, Tools and Results)
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16 pages, 7732 KiB  
Article
Effect of Wastewater Irrigation on Photosynthesis, Growth, and Anatomical Features of Two Wheat Cultivars (Triticum aestivum L.)
by Shokoofeh Hajihashemi, Sonia Mbarki, Milan Skalicky, Fariba Noedoost, Marzieh Raeisi and Marian Brestic
Water 2020, 12(2), 607; https://doi.org/10.3390/w12020607 - 24 Feb 2020
Cited by 47 | Viewed by 6179
Abstract
The wastewater from the Razi petrochemical complex contains high levels of salts and heavy metals. In the present research, the effects of different wastewater dilution levels (0, 25%, 50%, and 100%) were studied on two wheat cultivars—Chamran and Behrang. The wastewater contained high [...] Read more.
The wastewater from the Razi petrochemical complex contains high levels of salts and heavy metals. In the present research, the effects of different wastewater dilution levels (0, 25%, 50%, and 100%) were studied on two wheat cultivars—Chamran and Behrang. The wastewater contained high levels of NH4+, NO3-, PO43-, and SO42-, and Mg, Ca, K, Na, Cu, Zn, Fe, M, and Ni. The toxic levels of mineral elements in the wastewater resulted in a significant decline in the K, P, Si, and Zn content of leaves. Irrigation with the wastewater resulted in a significant reduction in photosynthetic characteristics including chlorophyll fluorescence (Fv/Fm and PIABS), intercellular CO2, net photosynthesis, water use efficiency, and photosynthetic pigments. The reduction in photosynthesis was followed by a significant decrease in the carbohydrate content and, subsequently, plant height, leaf area, and grain yield. Increasing the wastewater concentration reduced leaf thickness and root diameter, accounting for the decrease in xylem and phloem vessels, the root cortical parenchyma, and mesophyll thickness. The bulliform cell size increased under wastewater treatment, which may suggest induction of a defense system against water loss through leaf rolling. Based on the observed negative effect of wastewater on physiology, morphology, anatomy, and yield of two wheat cultivars, reusing wastewater with high levels of total suspended solids and salts for irrigation cannot be approved for wheat crops. Full article
(This article belongs to the Special Issue Advances in the Technologies for Water and Wastewater Treatment)
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21 pages, 2447 KiB  
Article
Mathematical Study on Wave Propagation through Emergent Vegetation
by Yuan-Jyh Lan
Water 2020, 12(2), 606; https://doi.org/10.3390/w12020606 - 23 Feb 2020
Viewed by 2449
Abstract
In this paper, the problem of the interaction between a periodic linear wave and offshore aquatic vegetation is investigated. The aquatic vegetation field is considered as a flexible permeable system. A vegetation medium theory is proposed based on Lan–Lee’s poro-elastomer theory, in which [...] Read more.
In this paper, the problem of the interaction between a periodic linear wave and offshore aquatic vegetation is investigated. The aquatic vegetation field is considered as a flexible permeable system. A vegetation medium theory is proposed based on Lan–Lee’s poro-elastomer theory, in which linearizing vegetation friction resistance is used to describe fluid motion in the vegetation medium. The study involves boundary conditions for free surface water in emergent vegetation media that have been of less concern in previous studies. The analytical solutions of the vegetation medium and wave fields are derived by the partitioning method combined with matching boundary conditions for neighboring regions. An estimation formula for a modification factor is proposed to evaluate the linear vegetation friction coefficient, which can reasonably compare the analytical solution with relevant past cases in terms of wave transmission. Wave reflection, transmission, and attenuation induced by the effects of the characteristics of the vegetation are studied. The results indicate that an increase in the drag coefficient, stem diameter, stem density, spatial coverage, and plant stiffness leads to the emergency vegetation inducing higher wave energy dissipation and reducing the wave transmission. Vegetation stiffness is a significant factor affecting the drag coefficient. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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17 pages, 13465 KiB  
Article
Flood Routing Process and High Dam Interception of Natural Discharge from the 2018 Baige Landslide-Dammed Lake
by Bin-Rui Gan, Xing-Guo Yang, Hai-Mei Liao and Jia-Wen Zhou
Water 2020, 12(2), 605; https://doi.org/10.3390/w12020605 - 23 Feb 2020
Cited by 7 | Viewed by 3663
Abstract
The outburst flood of the Baige landslide dam caused tremendous damage to infrastructure, unfinished hydraulic buildings, roads, and bridges that were built or under construction along the Jinsha River. Can downstream hydraulic buildings, such as high dams with flood control and discharge function, [...] Read more.
The outburst flood of the Baige landslide dam caused tremendous damage to infrastructure, unfinished hydraulic buildings, roads, and bridges that were built or under construction along the Jinsha River. Can downstream hydraulic buildings, such as high dams with flood control and discharge function, accommodate outburst floods or generate more serious losses due to wave overtopping? In this study, the unsteady flow of a one-dimensional hydraulic calculation was used to simulate natural flood discharge. Assuming a high dam (Yebatan arch dam) is constructed downstream, the flood processes were carried out in two forms of high dam interception (complete interception, comprehensive flood control of blocking and draining). Moreover, three-dimensional visualization of the inundation area was performed. Simulation results indicate that the Yebatan Hydropower Station can completely eliminate the outburst flood risk even under the most dangerous situations. This station can reduce the flood peak and delay the peak flood arrival time. Specifically, the flood peak decreased more obviously when it was closer to the upstream area, and the flood peak arrival time was more delayed when the flood spread further downstream. In addition, the downstream water depth was reduced by approximately 10 m, and the inundation area was reduced to half of the natural discharge. This phenomenon shows that hydraulic buildings such as high dams can reduce the inundation area of downstream farmlands and extend the evacuation time for downstream residents during the flood process, thus reducing the loss of life and property. Full article
(This article belongs to the Special Issue Hydrological Prediction and Flooding Risk Assessment)
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14 pages, 3120 KiB  
Article
Estimation and Mapping of the Transmissivity of the Nubian Sandstone Aquifer in the Kharga Oasis, Egypt
by Mustafa El-Rawy and Florimond De Smedt
Water 2020, 12(2), 604; https://doi.org/10.3390/w12020604 - 23 Feb 2020
Cited by 14 | Viewed by 4843
Abstract
The Nubian sandstone aquifer is the only water source for domestic use and irrigation in the Kharga oasis, Egypt. In this study, 46 pumping tests are analyzed to estimate the transmissivity of the aquifer and to derive a spatial distribution map by geostatistical [...] Read more.
The Nubian sandstone aquifer is the only water source for domestic use and irrigation in the Kharga oasis, Egypt. In this study, 46 pumping tests are analyzed to estimate the transmissivity of the aquifer and to derive a spatial distribution map by geostatistical analysis and kriging interpolation. The resulting transmissivity values are log-normally distributed and spatially correlated over a distance of about 20 km. Representative values for the transmissivity are a geometric average of about 400 m2/d and a 95% confidence interval of 100–1475 m2/d. There is no regional trend in the spatial distribution of the transmissivity, but there are local clusters with higher or lower transmissivity values. The error map indicates that the highest prediction accuracy is obtained along the central north-south traffic route along which most agricultural areas and major well sites are located. This study can contribute to a better understanding of the hydraulic properties of the Nubian sandstone aquifer in the Kharga oasis for an effective management strategy. Full article
(This article belongs to the Special Issue Sustainable Management of Aquifers in Semi-Arid Tropics)
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17 pages, 4792 KiB  
Article
Towards an Assessment of the Ephemeral Gully Erosion Potential in Greece Using Google Earth
by Christos Karydas and Panos Panagos
Water 2020, 12(2), 603; https://doi.org/10.3390/w12020603 - 23 Feb 2020
Cited by 27 | Viewed by 5019
Abstract
Gully erosion may cause considerable soil losses and produce large volumes of sediment. The aim of this study was to perform a preliminary assessment on the presence of ephemeral gullies in Greece by sampling representative cultivated fields in 100 sites randomly distributed throughout [...] Read more.
Gully erosion may cause considerable soil losses and produce large volumes of sediment. The aim of this study was to perform a preliminary assessment on the presence of ephemeral gullies in Greece by sampling representative cultivated fields in 100 sites randomly distributed throughout the country. The almost 30-ha sampling surfaces were examined with visual interpretation of multi-temporal imagery from the online Google Earth for the period 2002–2019. In parallel, rill and sheet erosion signs, land uses, and presence of terraces and other anti-erosion features, were recorded within every sample. One hundred fifty-three ephemeral gullies were identified in total, inside 22 examined agricultural surfaces. The mean length of the gullies was 55.6 m, with an average slope degree of 9.7%. Vineyards showed the largest proportion of gullies followed by olive groves and arable land, while pastures exhibited limited presence of gullies. Spatial clusters of high gully severity were observed in the north and east of the country. In 77% of the surfaces with gullies, there were no terraces, although most of these surfaces were situated in slopes higher than 8%. It was the first time to use visual interpretation with Google Earth image time-series on a country scale producing a gully erosion inventory. Soil conservation practices such as contour farming and terraces could mitigate the risk of gully erosion in agricultural areas. Full article
(This article belongs to the Special Issue The Effect of Hydrology on Soil Erosion)
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19 pages, 8712 KiB  
Article
Climate Change Impacts on Cold Season Runoff in the Headwaters of the Yellow River Considering Frozen Ground Degradation
by Pan Wu, Sihai Liang, Xu-Sheng Wang, Jeffrey M. McKenzie and Yuqing Feng
Water 2020, 12(2), 602; https://doi.org/10.3390/w12020602 - 22 Feb 2020
Cited by 10 | Viewed by 4105
Abstract
Climate change has effects on hydrological change in multiple aspects, particularly in the headwaters of the Yellow River (HWYR), which is widely covered by climate-sensitive frozen ground. In this study, the annual runoff was partitioned into four runoff compositions: winter baseflow, snowmelt runoff, [...] Read more.
Climate change has effects on hydrological change in multiple aspects, particularly in the headwaters of the Yellow River (HWYR), which is widely covered by climate-sensitive frozen ground. In this study, the annual runoff was partitioned into four runoff compositions: winter baseflow, snowmelt runoff, rainy season runoff, and recession flow. In addition, the effects of global warming, precipitation change, and frozen ground degradation were considered in long-term variation analyses of the runoff compositions. The moving t-test was employed to detect change points of the hydrometeorological data series from 1961 to 2013, and flow duration curves were used to analyze daily runoff regime change in different periods. It was found that the abrupt change points of cold season runoff, such as recession flow, winter baseflow, and snowmelt runoff, are different from that of the rainy season runoff. The increase in winter baseflow and decrease in snowmelt runoff at the end of 1990s was closely related to global warming. In the 21st century, winter baseflow presented a larger relative increase compared to rainy season runoff. The correlation analyses indicate that winter baseflow and snowmelt runoff are mainly controlled by water-resource-related factors, such as rainy season runoff and the accumulated precipitation in cold season. To analyze the global warming impacts, two runoff coefficients—winter baseflow discharge rate (Rw) and direct snowmelt runoff coefficients (Rs)—were proposed, and their correlation with freezing–thawing indices were analyzed. The increase of Rw is related to the increase in the air temperature thawing index (DDT), but Rs is mainly controlled by the air temperature freezing index (DDF). Meanwhile, the direct snowmelt runoff coefficient (Rs) is significantly and positively correlated to DDF and has decreased at a rate of 0.0011/year since 1980. Under global warming, the direct snowmelt runoff (runoff increment between March to May) of the HWYR could decrease continuously in the future due to the decrease of accumulative snow in cold season and frozen ground degradation. This study provides a better understanding of the long-term runoff characteristic changes in the HWYR. Full article
(This article belongs to the Special Issue Climate Change Effects on Hydrological Processes, Water Resources, Ecosystems and Agriculture)
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19 pages, 6050 KiB  
Article
Transient-Flow Induced Compressed Air Energy Storage (TI-CAES) System towards New Energy Concept
by Mohsen Besharat, Avin Dadfar, Maria Teresa Viseu, Bruno Brunone and Helena M. Ramos
Water 2020, 12(2), 601; https://doi.org/10.3390/w12020601 - 22 Feb 2020
Cited by 9 | Viewed by 4581
Abstract
In recent years, interest has increased in new renewable energy solutions for climate change mitigation and increasing the efficiency and sustainability of water systems. Hydropower still has the biggest share due to its compatibility, reliability and flexibility. This study presents one such technology [...] Read more.
In recent years, interest has increased in new renewable energy solutions for climate change mitigation and increasing the efficiency and sustainability of water systems. Hydropower still has the biggest share due to its compatibility, reliability and flexibility. This study presents one such technology recently examined at Instituto Superior Técnico based on a transient-flow induced compressed air energy storage (TI-CAES) system, which takes advantage of a compressed air vessel (CAV). The CAV can produce extra required pressure head, by compressing air, to be used for either hydropower generation using a water turbine in a gravity system or to be exploited in a pumping system. The results show a controlled behaviour of the system in storing the pressure surge as compressed air inside a vessel. Considerable power values are achieved as well, while the input work is practically neglected. Higher power values are attained for bigger air volumes. The TI-CAES offers an efficient and flexible solution that can be exploited in exiting water systems without putting the system at risk. The induced transients in the compressed air allow a constant outflow discharge characteristic, making the energy storage available in the CAV to be used as a pump storage hydropower solution. Full article
(This article belongs to the Special Issue Environmental Hydraulics Research)
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18 pages, 12635 KiB  
Article
Using a Data Driven Approach to Predict Waves Generated by Gravity Driven Mass Flows
by Zhenzhu Meng, Yating Hu and Christophe Ancey
Water 2020, 12(2), 600; https://doi.org/10.3390/w12020600 - 22 Feb 2020
Cited by 23 | Viewed by 4239
Abstract
When colossal gravity-driven mass flows enter a body of water, they may generate waves which can have destructive consequences on coastal areas. A number of empirical equations in the form of power functions of several dimensionless groups have been developed to predict wave [...] Read more.
When colossal gravity-driven mass flows enter a body of water, they may generate waves which can have destructive consequences on coastal areas. A number of empirical equations in the form of power functions of several dimensionless groups have been developed to predict wave characteristics. However, in some complex cases (for instance, when the mass striking the water is made up of varied slide materials), fitting an empirical equation with a fixed form to the experimental data may be problematic. In contrast to previous empirical equations that specified the mathematical operators in advance, we developed a purely data-driven approach which relies on datasets and does not need any assumptions about functional form or physical constraints. Experiments were carried out using Carbopol Ultrez 10 (a viscoplastic polymeric gel) and polymer–water balls. We selected an artificial neural network model as an example of a data-driven approach to predicting wave characteristics. We first validated the model by comparing it with best-fit empirical equations. Then, we applied the proposed model to two scenarios which run into difficulty when modeled using those empirical equations: (i) predicting wave features from subaerial landslide parameters at their initial stage (with the mass beginning to move down the slope) rather than from the parameters at impact; and (ii) predicting waves generated by different slide materials, specifically, viscoplastic slides, granular slides, and viscoplastic–granular mixtures. The method proposed here can easily be updated when new parameters or constraints are introduced into the model. Full article
(This article belongs to the Special Issue Non-Newtonian Fluids in Environmental Hydraulics: Modelling and Applications)
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13 pages, 2918 KiB  
Article
Ammonium-Nitrogen (NH4+-N) Removal from Groundwater by a Dropping Nitrification Reactor: Characterization of NH4+-N Transformation and Bacterial Community in the Reactor
by Amit Kumar Maharjan, Tatsuru Kamei, Iswar Man Amatya, Kazuhiro Mori, Futaba Kazama and Tadashi Toyama
Water 2020, 12(2), 599; https://doi.org/10.3390/w12020599 - 22 Feb 2020
Cited by 14 | Viewed by 8565
Abstract
A dropping nitrification reactor was proposed as a low-cost and energy-saving option for the removal of NH4+-N from contaminated groundwater. The objectives of this study were to investigate NH4+-N removal performance and the nitrogen removal pathway and [...] Read more.
A dropping nitrification reactor was proposed as a low-cost and energy-saving option for the removal of NH4+-N from contaminated groundwater. The objectives of this study were to investigate NH4+-N removal performance and the nitrogen removal pathway and to characterize the microbial communities in the reactor. Polyolefin sponge cubes (10 mm × 10 mm × 10 mm) were connected diagonally in a nylon thread to produce 1 m long dropping nitrification units. Synthetic groundwater containing 50 mg L−1 NH4+-N was added from the top of the hanging units at a flow rate of 4.32 L day−1 for 56 days. Nitrogen-oxidizing microorganisms in the reactor removed 50.8–68.7% of the NH4+-N in the groundwater, which was aerated with atmospheric oxygen as it flowed downwards through the sponge units. Nitrogen transformation and the functional bacteria contributing to it were stratified in the sponge units. Nitrosomonadales-like AOB predominated and transformed NH4+-N to NO2−-N in the upper part of the reactor. Nitrospirales-like NOB predominated and transformed NO2−-N to NO3−-N in the lower part of the reactor. The dropping nitrification reactor could be a promising technology for oxidizing NH4+-N in groundwater and other similar contaminated wastewaters. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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14 pages, 1851 KiB  
Article
The Effect of Soil Iron on the Estimation of Soil Water Content Using Dielectric Sensors
by George Kargas, Paraskevi Londra, Marianthi Anastasatou and Nick Moustakas
Water 2020, 12(2), 598; https://doi.org/10.3390/w12020598 - 22 Feb 2020
Cited by 8 | Viewed by 2994
Abstract
Nowadays, the estimation of volumetric soil water content (θ) through apparent dielectric permittivity (εa) is the most widely used method. The purpose of this study is to investigate the effect of the high iron content of two sandy loam soils on [...] Read more.
Nowadays, the estimation of volumetric soil water content (θ) through apparent dielectric permittivity (εa) is the most widely used method. The purpose of this study is to investigate the effect of the high iron content of two sandy loam soils on estimating their water content using two dielectric sensors. These sensors are the WET sensor operating at 20 MHz and the ML2 sensor operating at 100 MHz. Experiments on specific soil columns, in the laboratory, by mixing different amounts of water in the soils to obtain a range of θ values under constant temperature conditions were conducted. Analysis of the results showed that both sensors, based on manufacturer calibration, led to overestimation of θ. This overestimation is due to the high measured values of εa by both sensors used. The WET sensor, operating at a lower frequency and being strongly affected by soil characteristics, showed the greatest overestimation. The difference of εa values between the two sensors ranged from 14 to 19 units at the maximum actual soil water content (θm). Compared to the Topp equation, the WET sensor measures 2.3 to 2.8 fold higher value of εa. From the results, it was shown that the relationship θm-εa0.5 remained linear even in the case of these soils with high iron content and the multi-point calibration (CALALL) is a good option where individual calibration is needed. Full article
(This article belongs to the Special Issue Study of the Soil Water Movement in Irrigated Agriculture)
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15 pages, 4625 KiB  
Article
Changes in Planktivory and Herbivory Regimes in a Shallow South American Lake (Lake Blanca Chica, Argentina) Over the Last 250 Years
by David Carrozzo, Simona Musazzi, Andrea Lami, Francisco E. Córdoba and María de los Ángeles González Sagrario
Water 2020, 12(2), 597; https://doi.org/10.3390/w12020597 - 22 Feb 2020
Cited by 3 | Viewed by 2890
Abstract
Shallow lakes are vulnerable ecosystems impacted by human activities and climate change. The Cladocera occupy a central role in food webs and are an excellent paleoecological indicator of food web structure and trophic status. We conducted a paleolimnological study in Lake Blanca Chica [...] Read more.
Shallow lakes are vulnerable ecosystems impacted by human activities and climate change. The Cladocera occupy a central role in food webs and are an excellent paleoecological indicator of food web structure and trophic status. We conducted a paleolimnological study in Lake Blanca Chica (Argentina) to detect changes on the planktivory and herbivory regimes over the last 250 years. Generalized additive models were fitted to the time series of fish predation indicators (ephippial abundance and size, mucrone size, fish scales, and the planktivory index) and pheophorbide a concentration. The cladoceran assemblage changed from littoral-benthic to pelagic species dominance and zooplankton switched from large-bodied (Daphnia) to small-bodied grazers (Bosmina) ca. 1900 due to increased predation. The shift in planktivory regime (ca. 1920–1930), indicated by fish scales and the planktivory index, as well as herbivory (ca. 1920–1950), was triggered by eutrophication. Changes in planktivory affected the size structure of Bosmina, reducing its body size. This study describes the baseline for the lake as well as the profound changes in the composition and size structure of the zooplankton community due to increased predation and the shift in the planktivory regime. These findings will provide a reference status for future management strategies of this ecosystem. Full article
(This article belongs to the Special Issue Zooplankton Diversity and Pelagic Food Webs: Investigating Present and Past with Different Techniques)
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18 pages, 3910 KiB  
Review
An Integrated Review of River Bars for Engineering, Management and Transdisciplinary Research
by Alessandra Crosato and Erik Mosselman
Water 2020, 12(2), 596; https://doi.org/10.3390/w12020596 - 21 Feb 2020
Cited by 28 | Viewed by 5308
Abstract
River training and river restoration often imply modifying the patterns and dimensions of bars, channels, and pools. Research since the 1980s has greatly advanced and matured our knowledge on the formation and behavior of river bars, thanks to field work, laboratory experiments, theoretical [...] Read more.
River training and river restoration often imply modifying the patterns and dimensions of bars, channels, and pools. Research since the 1980s has greatly advanced and matured our knowledge on the formation and behavior of river bars, thanks to field work, laboratory experiments, theoretical analyses, and numerical modelling by several research groups. However, this knowledge is not easily accessible to design engineers, river managers, and ecologists who need to apply it. This is mainly due to confusing differences in terminology as well as to difficult mathematical theories. Moreover, existing scientific publications generally focus on specific aspects, so an overall review of the findings and their applications is still lacking. In many cases, the knowledge achieved so far would allow minimizing hard engineering interventions and thus obtaining more natural rivers. We present an integrated review of the major findings of river bar studies. Our aim is to provide accessible state-of-the-art knowledge for nature-based bar management and successful river training and river restoration. To this end we review the results from analytical, numerical, experimental, and field studies, explain the background of bar theories, and discuss applications in river engineering and river restoration. Full article
(This article belongs to the Special Issue Studies on River Training)
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12 pages, 2684 KiB  
Article
Electrocoagulation: A Promising Method to Treat and Reuse Mineral Processing Wastewater with High COD
by Gaogui Jing, Shuai Ren, Yuesheng Gao, Wei Sun and Zhiyong Gao
Water 2020, 12(2), 595; https://doi.org/10.3390/w12020595 - 21 Feb 2020
Cited by 46 | Viewed by 5111
Abstract
Mineral processing wastewater contains large amounts of reagents which can lead to severe environmental problems, such as high chemical oxygen demand (COD). Inspired by the wastewater treatment in such industries as those of textiles, food, and petrochemistry, in the present work, electrocoagulation (EC) [...] Read more.
Mineral processing wastewater contains large amounts of reagents which can lead to severe environmental problems, such as high chemical oxygen demand (COD). Inspired by the wastewater treatment in such industries as those of textiles, food, and petrochemistry, in the present work, electrocoagulation (EC) is applied for the first time to explore its feasibility in the treatment of wastewater with an initial COD of 424.29 mg/L from a Pb/Zn sulfide mineral flotation plant and its effect on water reuse. Typical parameters, such as anode materials, current density, initial pH, and additives, were characterized to evaluate the performance of the EC method. The results showed that, under optimal conditions, i.e., iron anode, pH 7.1, electrolysis time 70 min, 19.23 mA/cm2 current density, and 4.1 g/L activated carbon, the initial COD can be reduced to 72.9 mg/L, corresponding to a removal rate of 82.8%. In addition, compared with the untreated wastewater, EC-treated wastewater was found to benefit the recovery of galena and sphalerite, with galena recovery increasing from 25.01% to 36.06% and sphalerite recovery increasing from 59.99% to 65.33%. This study confirmed that EC is a promising method for the treatment and reuse of high-COD-containing wastewater in the mining industry, and it possesses great potential for wide industrial applications. Full article
(This article belongs to the Special Issue Wastewater Treatment, Valorization and Reuse)
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13 pages, 15936 KiB  
Article
Preliminary Characterization of Underground Hydrological Processes under Multiple Rainfall Conditions and Rocky Desertification Degrees in Karst Regions of Southwest China
by Guijing Li, Matteo Rubinato, Long Wan, Bin Wu, Jiufu Luo, Jianmei Fang and Jinxing Zhou
Water 2020, 12(2), 594; https://doi.org/10.3390/w12020594 - 21 Feb 2020
Cited by 6 | Viewed by 2873
Abstract
Karst regions are widely distributed in Southwest China and due to the complexity of their geologic structure, it is very challenging to collect data useful to provide a better understanding of surface, underground and fissure flows, needed to calibrate and validate numerical models. [...] Read more.
Karst regions are widely distributed in Southwest China and due to the complexity of their geologic structure, it is very challenging to collect data useful to provide a better understanding of surface, underground and fissure flows, needed to calibrate and validate numerical models. Without characterizing these features, it is very problematic to fully establish rainfall–runoff processes associated with soil loss in karst landscapes. Water infiltrated rapidly to the underground in rocky desertification areas. To fill this gap, this experimental work was completed to preliminarily determine the output characteristics of subsurface and underground fissure flows and their relationships with rainfall intensities (30 mm h−1, 60 mm h−1 and 90 mm h−1) and bedrock degrees (30%, 40% and 50%), as well as the role of underground fissure flow in the near-surface rainfall–runoff process. Results indicated that under light rainfall conditions (30 mm h−1), the hydrological processes observed were typical of Dunne overland flows; however, under moderate (60 mm h−1) and high rainfall conditions (90 mm h−1), hydrological processes were typical of Horton overland flows. Furthermore, results confirmed that the generation of underground runoff for moderate rocky desertification (MRD) and severe rocky desertification (SRD) happened 18.18% and 45.45% later than the timing recorded for the light rocky desertification (LRD) scenario. Additionally, results established that the maximum rate of underground runoff increased with the increase of bedrock degrees and the amount of cumulative underground runoff measured under different rocky desertification was SRD > MRD > LRD. In terms of flow characterization, for the LRD configuration under light rainfall intensity the underground runoff was mainly associated with soil water, which was accounting for about 85%–95%. However, under moderate and high rainfall intensities, the underground flow was mainly generated from fissure flow. Full article
(This article belongs to the Special Issue Advances in Modelling and Prediction on the Impact of Human Activities and Extreme Events on Environments)
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18 pages, 5477 KiB  
Article
Understanding Complexity in Freshwater Management: Practitioners’ Perspectives in The Netherlands
by Guido Rutten, Steve Cinderby and Jennie Barron
Water 2020, 12(2), 593; https://doi.org/10.3390/w12020593 - 21 Feb 2020
Cited by 3 | Viewed by 3302
Abstract
Ecosystems have been stabilized by human interventions to optimize delivery of certain ecosystem services, while at the same time awareness has grown that these systems are inherently dynamic rather than steady state. Applied research fields have emerged that try to increase adaptive capacity [...] Read more.
Ecosystems have been stabilized by human interventions to optimize delivery of certain ecosystem services, while at the same time awareness has grown that these systems are inherently dynamic rather than steady state. Applied research fields have emerged that try to increase adaptive capacity in these ecosystems, using concepts deriving from the theory of complex adaptive systems. How are these concepts of complexity interpreted and applied by practitioners? This study applies a mixed-methods approach to analyze the case of freshwater management in The Netherlands, where a management paradigm promoting nature-fixating interventions is recently being replaced with a new paradigm of nature-based solutions. We find that practitioners have widely varying interpretations of concepts and of how the ecosystems they work in have evolved over time when described with complex system attributes. This study allows for the emergence of key complexity-related considerations among practitioners that are not often discussed in literature: (i) the need for physical and institutional space for self-organization of nature; (ii) the importance of dependency and demand management; and (iii) trade-offs between robustness and flexibility. This study, furthermore, stresses the importance of using practitioners’ views to guide applied research and practice in this field. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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16 pages, 3807 KiB  
Article
Nutrient Recovery from Anaerobically Treated Blackwater and Improving Its Effluent Quality through Microalgae Biomass Production
by Melesse Eshetu Moges, Arve Heistad and Thorsten Heidorn
Water 2020, 12(2), 592; https://doi.org/10.3390/w12020592 - 21 Feb 2020
Cited by 20 | Viewed by 4333
Abstract
The blackwater stream of domestic wastewater contains energy and the majority of nutrients that can contribute to a circular economy. Hygienically safe and odor-free nutrient solution produced from anaerobically treated source-separated blackwater through an integrated post-treatment unit can be used as a source [...] Read more.
The blackwater stream of domestic wastewater contains energy and the majority of nutrients that can contribute to a circular economy. Hygienically safe and odor-free nutrient solution produced from anaerobically treated source-separated blackwater through an integrated post-treatment unit can be used as a source of liquid fertilizer. However, the high water content in the liquid fertilizer represents a storage or transportation challenge when utilized on agricultural areas, which are often situated far from the urban areas. Integration of microalgae into treated source-separated blackwater (BW) has been shown to effectively assimilate and recover phosphorus (P) and nitrogen (N) in the form of green biomass to be used as slow release biofertilizer and hence close the nutrient loop. With this objective, a lab-scale flat panel photobioreactor was used to cultivate Chlorella sorokiniana strain NIVA CHL 176 in a chemostat mode of operation. The growth of C. sorokiniana on treated source-separated blackwater as a substrate was monitored by measuring dry biomass concentration at a dilution rate of 1.38 d−1, temperature of 37 °C and pH of 7. The results indicate that the N and P recovery rates of C. sorokiniana were 99 mg N L−1d−1 and 8 mg P L−1d−1 for 10% treated BW and reached 213 mg N L−1d−1 and 35 mg P L−1d−1, respectively when using 20% treated BW as a substrate. The corresponding biomass yield on light, N and P on the 20% treated BW substrate were 0.37 g (mol photon)−1, 9.1 g g−1 and 54.1 g g−1, respectively, and up to 99% of N and P were removed from the blackwater. Full article
(This article belongs to the Special Issue Hybrid Systems Using Different Technologies for Wastewater Treatment and Reuse)
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12 pages, 3552 KiB  
Article
An Experimental Method for Generating Shear-Free Turbulence Using Horizontal Oscillating Grids
by Wenjie Li, Peng Zhang, Shengfa Yang, Xuhui Fu and Yi Xiao
Water 2020, 12(2), 591; https://doi.org/10.3390/w12020591 - 21 Feb 2020
Cited by 2 | Viewed by 2315
Abstract
An experimental apparatus driven by horizontal oscillating grids in a water tank is proposed for generating shear-free turbulence, which is measured using Particle Image Velocimetry (PIV). The performances of the proposed apparatus are investigated through the instantaneous and root-mean-square (RMS) velocity, Reynolds stress, [...] Read more.
An experimental apparatus driven by horizontal oscillating grids in a water tank is proposed for generating shear-free turbulence, which is measured using Particle Image Velocimetry (PIV). The performances of the proposed apparatus are investigated through the instantaneous and root-mean-square (RMS) velocity, Reynolds stress, length and time scale, frequency spectra and dissipation rate. Results indicate that the turbulence at the core region of the water tank, probably 8 cm in length, is identified to be shear-free. The main advantage of the turbulence driven by horizontal oscillating mode is that the ratios of the longitudinal turbulent intensities to the vertical values are between 1.5 and 2.0, consistent with those ratios in open-channel flows. Additionally, the range of the length scale can span the typical sizes of suspended particles in natural environments, and the dissipation rate also agrees with those found in natural environments. For convenience of experimental use, a formula is suggested to calculate the RMS flow velocity, which is linearly proportional to the product of oscillating stroke and frequency. The proposed experimental method in this study appears to be more appropriate than the traditional vertical oscillating mode for studying the fundamental mechanisms of vertical migratory behavior of suspended particles and contaminants in turbulent flows. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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15 pages, 2800 KiB  
Article
Visualization Framework for High-Dimensional Spatio-Temporal Hydrological Gridded Datasets using Machine-Learning Techniques
by Abeer Mazher
Water 2020, 12(2), 590; https://doi.org/10.3390/w12020590 - 21 Feb 2020
Cited by 18 | Viewed by 4218
Abstract
Numerical modelling increasingly generates massive, high-dimensional spatio-temporal datasets. Exploring such datasets relies on effective visualization. This study presents a generic workflow to (i) project high-dimensional spatio-temporal data on a two-dimensional (2D) plane accurately (ii) compare dimensionality reduction techniques (DRTs) in terms of resolution [...] Read more.
Numerical modelling increasingly generates massive, high-dimensional spatio-temporal datasets. Exploring such datasets relies on effective visualization. This study presents a generic workflow to (i) project high-dimensional spatio-temporal data on a two-dimensional (2D) plane accurately (ii) compare dimensionality reduction techniques (DRTs) in terms of resolution and computational efficiency (iii) represent 2D projection spatially using a 2D perceptually uniform background color map. Machine learning (ML) based DRTs for data visualization i.e., principal component analysis (PCA), generative topographic mapping (GTM), t-distributed stochastic neighbor embedding (t-SNE) and uniform manifold approximation and projection (UMAP) are compared in terms of accuracy, resolution and computational efficiency to handle massive datasets. The accuracy of visualization is evaluated using a quality metric based on a co-ranking framework. The workflow is applied to an output of an Australian Water Resource Assessment (AWRA) model for Tasmania, Australia. The dataset consists of daily time series of nine components of the water balance at a 5 km grid cell resolution for the year 2017. The case study shows that PCA allows rapid visualization of global data structures, while t-SNE and UMAP allows more accurate representation of local trends. Furthermore, UMAP is computationally more efficient than t-SNE and least affected by the outliers compared to GTM. Full article
(This article belongs to the Section Hydrology)
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13 pages, 2696 KiB  
Article
Effect of Heavy Metal Ions on Steroid Estrogen Removal and Transport in SAT Using DLLME as a Detection Method of Steroid Estrogen
by Ge Zhang, Yuesuo Yang, Ying Lu, Yu Chen, Wenbo Li and Siyuan Wang
Water 2020, 12(2), 589; https://doi.org/10.3390/w12020589 - 21 Feb 2020
Cited by 6 | Viewed by 2934
Abstract
Environmental endocrine-disrupting chemicals have become a global environmental problem, and the distribution, transport, and fate of estrogens in soil and water environments closely relate to human and ecological health as well as to the remediation scheme design. A new micro-extraction technique termed dispersive [...] Read more.
Environmental endocrine-disrupting chemicals have become a global environmental problem, and the distribution, transport, and fate of estrogens in soil and water environments closely relate to human and ecological health as well as to the remediation scheme design. A new micro-extraction technique termed dispersive liquid–liquid micro-extraction (DLLME) combined with high-performance liquid chromatography with fluorescence detector (HPLC-FLD) was developed for the determination of the concentration of steroid estrogens in water samples. The detection limits of HPLC-FLD and DLLME-HPLC/FLD were 0.68–1.73 μg L−1 and 7.16–69.22 ng L−1, respectively. Based on this method, the isothermal adsorption of 17β-E2 on sand and a breakthrough experiment of 17β-E2 and Cu2+ in a soil aquifer treatment (SAT) system were studied. The 17β-E2 adsorption capacity of sand in 17β-E2 solution was detected to be larger than that in a mixed solution of 17β-E2 and Cu(NO3)2 solution, and the breakthrough curves of 17β-E2 and Cu2+ in the mixed solution shifted forward in sand column experiments. Both suggested that the competitive adsorption of 17β-E2 and Cu2+ in the mixed solution might occur on the surface of the sand. In the process of the removal of 17β-E2 in wastewater by SAT, the existence of Cu2+ slightly inhibited the adsorption of 17β-E2 and accelerated the breakthrough of 17β-E2. These results ought to be a warning for SAT application for 17β-E2 removal in water where heavy metals coexist. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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12 pages, 2698 KiB  
Article
Wastewater Treatment by Novel Polyamide/Polyethylenimine Nanofibers with Immobilized Laccase
by Milena Maryšková, Markéta Schaabová, Hana Tománková, Vít Novotný and Miroslava Rysová
Water 2020, 12(2), 588; https://doi.org/10.3390/w12020588 - 21 Feb 2020
Cited by 17 | Viewed by 3389
Abstract
Endocrine-disrupting chemicals are highly resistant organic compounds, commonly occurring in the aquatic environment, that can interfere with the endocrine system of animals and humans, causing serious chronic diseases. In recent decades, enzymes from oxidoreductases have been studied for their potential to degrade these [...] Read more.
Endocrine-disrupting chemicals are highly resistant organic compounds, commonly occurring in the aquatic environment, that can interfere with the endocrine system of animals and humans, causing serious chronic diseases. In recent decades, enzymes from oxidoreductases have been studied for their potential to degrade these compounds effectively. In order to use such enzymes repeatedly, it is necessary to ensure their insolubility in water, a method termed enzyme immobilization. We developed novel polyamide/polyethylenimine (PA/PEI) nanofibers as a promising support material for the immobilization of various biomolecules. Our nanofibers are highly suitable due to a unique combination of mechanical endurance provided by polyamide 6 and their affinity toward biomolecules, ensured by numerous PEI amino groups. Enzyme laccase was successfully immobilized onto PA/PEI nanofibers using a simple and fast method, providing exceptional activity and stability of the attached enzyme. We then tested the degradation ability of the PA/PEI-laccase samples on a highly concentrated mixture of endocrine-disrupting chemicals in real wastewater with adjusted pH. The results indicate that the samples were a suitable material for wastewater treatment by degrading a highly concentrated mixture of bisphenol A, 17α-ethinylestradiol, triclosan, and diclofenac, in real wastewater effluent. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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19 pages, 3701 KiB  
Article
Adsorption of Methylene Blue in Water onto Activated Carbon by Surfactant Modification
by Yu Kuang, Xiaoping Zhang and Shaoqi Zhou
Water 2020, 12(2), 587; https://doi.org/10.3390/w12020587 - 21 Feb 2020
Cited by 332 | Viewed by 17923
Abstract
In this paper, the enhanced adsorption of methylene blue (MB) dye ion on the activated carbon (AC) modified by three surfactants in aqueous solution was researched. Anionic surfactants—sodium lauryl sulfate (SLS) and sodium dodecyl sulfonate (SDS)—and cationic surfactant—hexadecyl trimethyl ammonium bromide (CTAB)—were used [...] Read more.
In this paper, the enhanced adsorption of methylene blue (MB) dye ion on the activated carbon (AC) modified by three surfactants in aqueous solution was researched. Anionic surfactants—sodium lauryl sulfate (SLS) and sodium dodecyl sulfonate (SDS)—and cationic surfactant—hexadecyl trimethyl ammonium bromide (CTAB)—were used for the modification of AC. This work showed that the adsorption performance of cationic dye by activated carbon modified by anionic surfactants (SLS) was significantly improved, whereas the adsorption performance of cationic dye by activated carbon modified by cationic surfactant (CTAB) was reduced. In addition, the effects of initial MB concentration, AC dosage, pH, reaction time, temperature, real water samples, and additive salts on the adsorption were studied. When Na+, K+, Ca2+, NH4+, and Mg2+ were present in the MB dye solution, the effect of these cations was negligible on the adsorption (<5%). The presence of NO2- improved the adsorption performance significantly, whereas the removal rate of MB was reduced in the presence of competitive cation (Fe2+). It was found that the isotherm data had a good correlation with the Langmuir isotherm through analyzing the experimental data by various models. The dynamics of adsorption were better described by the pseudo-second-order model and the adsorption process was endothermic and spontaneous. The results showed that AC modified by anionic surfactant was effective for the adsorption of MB dye in both modeling water and real water. Full article
(This article belongs to the Special Issue Adsorbents for Water and Wastewater Treatment and Resource Recovery)
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15 pages, 8454 KiB  
Article
The Susceptibility of Juvenile American Shad to Rapid Decompression and Fluid Shear Exposure Associated with Simulated Hydroturbine Passage
by Brett D. Pflugrath, Ryan A. Harnish, Briana Rhode, Kristin Engbrecht, Bernardo Beirão, Robert P. Mueller, Erin L. McCann, John R. Stephenson and Alison H. Colotelo
Water 2020, 12(2), 586; https://doi.org/10.3390/w12020586 - 20 Feb 2020
Cited by 6 | Viewed by 3106
Abstract
Throughout many areas of their native range, American shad (Alosa sapidissima) and other Alosine populations are in decline. Though several conditions have influenced these declines, hydropower facilities have had significant negative effects on American shad populations. Hydropower facilities expose ocean-migrating American [...] Read more.
Throughout many areas of their native range, American shad (Alosa sapidissima) and other Alosine populations are in decline. Though several conditions have influenced these declines, hydropower facilities have had significant negative effects on American shad populations. Hydropower facilities expose ocean-migrating American shad to physical stressors during passage through hydropower facilities, including strike, rapid decompression, and fluid shear. In this laboratory-based study, juvenile American shad were exposed separately to rapid decompression and fluid shear to determine their susceptibility to these stressors and develop dose–response models. These dose–response relationships can help guide the development and/or operation of hydropower turbines and facilities to reduce the negative effects to American shad. Relative to other species, juvenile American shad have a high susceptibility to both rapid decompression and fluid shear. Reducing or preventing exposure to these stressors at hydropower facilities may be a potential method to assist in the effort to restore American shad populations. Full article
(This article belongs to the Special Issue Addressing the Environmental Impacts of Hydropower)
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