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Water, Volume 10, Issue 4 (April 2018)

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Cover Story (view full-size image) In order to identify regularities in the development of the 2 proglacial troughs located on the [...] Read more.
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Open AccessArticle Analysis of Anthropogenic, Climatological, and Morphological Influences on Dissolved Organic Matter in Rocky Mountain Streams
Water 2018, 10(4), 534; https://doi.org/10.3390/w10040534
Received: 27 February 2018 / Revised: 10 April 2018 / Accepted: 13 April 2018 / Published: 23 April 2018
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Abstract
In recent decades, the Rocky Mountains (RM) have undergone significant changes associated with anthropogenic activities and natural disturbances. These changes have the potential to alter primary productivity and biomass carbon storage. In particular, dissolved organic carbon (DOC) in RM streams can affect heterotrophic
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In recent decades, the Rocky Mountains (RM) have undergone significant changes associated with anthropogenic activities and natural disturbances. These changes have the potential to alter primary productivity and biomass carbon storage. In particular, dissolved organic carbon (DOC) in RM streams can affect heterotrophic processes, act as a source for the nutrient cycle, absorb sunlight radiation, alter metal transport, and can promote the production of carcinogenic byproducts during water treatment. Recent studies have focused on the relationship between bark beetle infestations and stream organic matter but have reached conflicting conclusions. Consequently, here we compile and process multiple datasets representing features of the RM for the period 1983–2012 with the purpose of assessing their relative influence on stream DOC concentrations using spatial statistical modeling. Features representing climate, land cover, forest disturbances, topography, soil types, and anthropogenic activities are included. We focus on DOC during base-flow conditions in RM streams because base-flow concentrations are more representative of the longer-term (annual to decadal) impacts and are less dependent on episodic, short-term storm and runoff/erosion events. To predict DOC throughout the network, we use a stream network model in a 56,550 km2 area to address the intrinsic connectivity and hydrologic directionality of the stream network. Natural forest disturbances are positively correlated with increased DOC concentrations; however, the effect of urbanization is far greater. Similarly, higher maximum temperatures, which can be exacerbated by climate change, are also associated with elevated DOC concentrations. Overall, DOC concentrations present an increasing trend over time in the RM region. Full article
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Open AccessArticle An Efficient Method for Mapping High-Resolution Global River Discharge Based on the Algorithms of Drainage Network Extraction
Water 2018, 10(4), 533; https://doi.org/10.3390/w10040533
Received: 25 March 2018 / Revised: 17 April 2018 / Accepted: 20 April 2018 / Published: 23 April 2018
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Abstract
River discharge, which represents the accumulation of surface water flowing into rivers and ultimately into the ocean or other water bodies, may have great impacts on water quality and the living organisms in rivers. However, the global knowledge of river discharge is still
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River discharge, which represents the accumulation of surface water flowing into rivers and ultimately into the ocean or other water bodies, may have great impacts on water quality and the living organisms in rivers. However, the global knowledge of river discharge is still poor and worth exploring. This study proposes an efficient method for mapping high-resolution global river discharge based on the algorithms of drainage network extraction. Using the existing global runoff map and digital elevation model (DEM) data as inputs, this method consists of three steps. First, the pixels of the runoff map and the DEM data are resampled into the same resolution (i.e., 0.01-degree). Second, the flow direction of each pixel of the DEM data (identified by the optimal flow path method used in drainage network extraction) is determined and then applied to the corresponding pixel of the runoff map. Third, the river discharge of each pixel of the runoff map is calculated by summing the runoffs of all the pixels in the upstream of this pixel, similar to the upslope area accumulation step in drainage network extraction. Finally, a 0.01-degree global map of the mean annual river discharge is obtained. Moreover, a 0.5-degree global map of the mean annual river discharge is produced to display the results with a more intuitive perception. Compared against the existing global river discharge databases, the 0.01-degree map is of a generally high accuracy for the selected river basins, especially for the Amazon River basin with the lowest relative error (RE) of 0.3% and the Yangtze River basin within the RE range of ±6.0%. However, it is noted that the results of the Congo and Zambezi River basins are not satisfactory, with RE values over 90%, and it is inferred that there may be some accuracy problems with the runoff map in these river basins. Full article
(This article belongs to the Special Issue Applications of Remote Sensing and GIS in Hydrology)
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Open AccessArticle Adsorption of Isothiazolone Biocides in Textile Reverse Osmosis Concentrate by Powdered Activated Carbon
Water 2018, 10(4), 532; https://doi.org/10.3390/w10040532
Received: 18 March 2018 / Revised: 13 April 2018 / Accepted: 20 April 2018 / Published: 23 April 2018
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Abstract
Isothiazolones have been widely applied as non-oxidizing biocides to prevent biofouling of reverse osmosis (RO) membranes. However, few studies have investigated suitable RO concentrate treatments to remove these biocides. This study evaluated the adsorption behavior of four isothiazolone biocides, 2-methyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT),
[...] Read more.
Isothiazolones have been widely applied as non-oxidizing biocides to prevent biofouling of reverse osmosis (RO) membranes. However, few studies have investigated suitable RO concentrate treatments to remove these biocides. This study evaluated the adsorption behavior of four isothiazolone biocides, 2-methyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), 1,2-benzisothiazol-3(2H)-one (BIT), and 2-n-octyl-4-isothiazolin-3-one (OIT), by powdered activated carbon (PAC). Isothiazolones adsorption was found to obey pseudo second-order kinetics. Langmuir adsorption isotherms were more suitable to simulation of the adsorption effects than Freundlich isotherms. The adsorption amount followed the order OIT > BIT > CMIT > MIT, in accordance with the isothiazolones octanol/water partition coefficients (Kow), indicating that hydrophobicity is the main factor for influencing adsorption amounts. Following normalization with Kow, the amounts of isothiazolones adsorbed at equilibrium and normalized aqueous concentrations showed a linear relationship in a log-linear form. 1,2-benzisothiazol-3(2H)-one is anionic at high pH, and difficult to adsorb, while neutral BIT is more likely to be adsorbed. Textile reverse osmosis concentrate had an adverse effect on MIT, CMIT and BIT adsorption, but little effect on adsorption of OIT, which has a high log Kow value. There was competition between organics and isothiazolones for PAC adsorption sites, which influenced the adsorption efficiency. Full article
(This article belongs to the Section Water and Wastewater Treatment)
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Open AccessFeature PaperReview Freshwater Ecosystem Services in Mining Regions: Modelling Options for Policy Development Support
Water 2018, 10(4), 531; https://doi.org/10.3390/w10040531
Received: 14 March 2018 / Revised: 18 April 2018 / Accepted: 20 April 2018 / Published: 23 April 2018
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Abstract
The ecosystem services (ES) approach offers an integrated perspective of social-ecological systems, suitable for holistic assessments of mining impacts. Yet for ES models to be policy-relevant, methodological consensus in mining contexts is needed. We review articles assessing ES in mining areas focusing on
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The ecosystem services (ES) approach offers an integrated perspective of social-ecological systems, suitable for holistic assessments of mining impacts. Yet for ES models to be policy-relevant, methodological consensus in mining contexts is needed. We review articles assessing ES in mining areas focusing on freshwater components and policy support potential. Twenty-six articles were analysed concerning (i) methodological complexity (data types, number of parameters, processes and ecosystem–human integration level) and (ii) potential applicability for policy development (communication of uncertainties, scenario simulation, stakeholder participation and management recommendations). Articles illustrate mining impacts on ES through valuation exercises mostly. However, the lack of ground- and surface-water measurements, as well as insufficient representation of the connectivity among soil, water and humans, leave room for improvements. Inclusion of mining-specific environmental stressors models, increasing resolution of topographies, determination of baseline ES patterns and inclusion of multi-stakeholder perspectives are advantageous for policy support. We argue that achieving more holistic assessments exhorts practitioners to aim for high social-ecological connectivity using mechanistic models where possible and using inductive methods only where necessary. Due to data constraints, cause–effect networks might be the most feasible and best solution. Thus, a policy-oriented framework is proposed, in which data science is directed to environmental modelling for analysis of mining impacts on water ES. Full article
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Open AccessArticle Inundation Analysis of Reservoir Flood Based on Computer Aided Design (CAD) and Digital Elevation Model (DEM)
Water 2018, 10(4), 530; https://doi.org/10.3390/w10040530
Received: 23 February 2018 / Revised: 2 April 2018 / Accepted: 16 April 2018 / Published: 23 April 2018
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Abstract
GIS (Geographic Information System) can be used to combine multiple hydrologic data and geographic data for FIA (Flood Impact Assessment). For a developing country like China, a lot of geographic data is in the CAD (Computer Aided Design) format. The commonly used method
[...] Read more.
GIS (Geographic Information System) can be used to combine multiple hydrologic data and geographic data for FIA (Flood Impact Assessment). For a developing country like China, a lot of geographic data is in the CAD (Computer Aided Design) format. The commonly used method for converting CAD into DEM may result in data loss. This paper introduces a solution for the conversion between CAD data and DEM data. The method has been applied to the FIA based on the topographic map of CAD in Hanjiang River. When compared with the other method, the new method solves the data loss problem. Besides, the paper use GIS to simulate the inundation range, area, and the depth distribution of flood backwater. Based on the analysis, the author concludes: (1) the differences of the inundation areas between the flood of HQ100 and the flood of HQ50 are small. (2) The inundation depth shows a decreasing trend along the upstream of the river. (3) The inundation area less than 4 m in flood of HQ50 is larger than that in flood of HQ100, the result is opposite when the inundation depth is greater than 4 m. (4) The flood loss is 392.32 million RMB for flood of HQ50 and 610.02 million RMB for flood of HQ100. The method can be applied to FIA. Full article
(This article belongs to the Special Issue Applications of Remote Sensing and GIS in Hydrology)
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Open AccessArticle PATs Operating in Water Networks under Unsteady Flow Conditions: Control Valve Manoeuvre and Overspeed Effect
Water 2018, 10(4), 529; https://doi.org/10.3390/w10040529
Received: 8 March 2018 / Revised: 6 April 2018 / Accepted: 9 April 2018 / Published: 23 April 2018
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Abstract
The knowledge of transient conditions in water pressurized networks equipped with pump as turbines (PATs) is of the utmost importance and necessary for the design and correct implementation of these new renewable solutions. This research characterizes the water hammer phenomenon in the design
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The knowledge of transient conditions in water pressurized networks equipped with pump as turbines (PATs) is of the utmost importance and necessary for the design and correct implementation of these new renewable solutions. This research characterizes the water hammer phenomenon in the design of PAT systems, emphasizing the transient events that can occur during a normal operation. This is based on project concerns towards a stable and efficient operation associated with the normal dynamic behaviour of flow control valve closure or by the induced overspeed effect. Basic concepts of mathematical modelling, characterization of control valve behaviour, damping effects in the wave propagation and runaway conditions of PATs are currently related to an inadequate design. The precise evaluation of basic operating rules depends upon the system and component type, as well as the required safety level during each operation. Full article
(This article belongs to the Special Issue Advances in Water Distribution Networks)
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Open AccessArticle Using SWAT-LUD Model to Estimate the Influence of Water Exchange and Shallow Aquifer Denitrification on Water and Nitrate Flux
Water 2018, 10(4), 528; https://doi.org/10.3390/w10040528
Received: 26 February 2018 / Revised: 2 April 2018 / Accepted: 6 April 2018 / Published: 23 April 2018
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Abstract
Numerous studies have pointed out the importance of groundwater and surface water interaction (SW–GW) in a river system. However; those functions have rarely been considered in large scale hydrological models. The SWAT-LUD model has been developed based on the Soil and Water Assessment
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Numerous studies have pointed out the importance of groundwater and surface water interaction (SW–GW) in a river system. However; those functions have rarely been considered in large scale hydrological models. The SWAT-LUD model has been developed based on the Soil and Water Assessment Tool (SWAT) model; and it integrates a new type of subbasin; which is called subbasin-LU (SL); to represent the floodplain area. New modules representing SW–GW exchanges and shallow aquifer denitrification are developed in the SWAT-LUD model. In this study; the SWAT-LUD model was applied to the middle floodplain area of the Garonne catchment in France. The results showed that the SWAT-LUD model could represent the SW–GW exchange and shallow aquifer denitrification appropriately. An annual 44.1 × 107 m3 of water flowed into the river from the study area; but the annual exchanged water volume was 6.4 × 107 m3; which represented just 1% of the river discharge. A total of 384 tons of N-NO3 (0.023 t·ha−1) was consumed by denitrification in the floodplain shallow aquifer annually. The nitrate concentration (N-NO3) decrease in the channel was 0.12 mg·L−1; but in the shallow aquifer it reached 11.40 mg·L−1; 8.05 mg·L−1; and 5.41 mg·L−1 in LU1; LU2; and LU3; respectively. Our study reveals that; in the Garonne floodplain; denitrification plays a significant role in the attenuation of nitrate associated with groundwater; but the impacts of denitrification on nitrate associated with river water is much less significant. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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Open AccessArticle Nitrogen Removal in Greywater Living Walls: Insights into the Governing Mechanisms
Water 2018, 10(4), 527; https://doi.org/10.3390/w10040527
Received: 12 March 2018 / Revised: 5 April 2018 / Accepted: 12 April 2018 / Published: 23 April 2018
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Abstract
Nitrogen is a pollutant of great concern when present in excess in surface waters. Living wall biofiltration systems that employ ornamentals and climbing plants are an emerging green technology that has recently demonstrated significant potential to reduce nitrogen concentrations from greywater before outdoor
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Nitrogen is a pollutant of great concern when present in excess in surface waters. Living wall biofiltration systems that employ ornamentals and climbing plants are an emerging green technology that has recently demonstrated significant potential to reduce nitrogen concentrations from greywater before outdoor domestic re-use. However, there still exists a paucity of knowledge around the mechanisms governing this removal, particularly in regards to the fate of dissolved organic nitrogen (DON) within these systems. Understanding the fate of nitrogen in living wall treatment systems is imperative both to optimise designs and to predict the long-term viability of these systems, more so given the growing interest in adopting green infrastructure within urban cities. A laboratory study was undertaken to investigate the transformation and fate of nitrogen in biofilters planted with different climbing plants and ornamental species. An isotropic tracer (15N-urea) was applied to quantify the amount removed through coupled nitrification-denitrification. The results found that nitrification-denitrification formed a minor removal pathway in planted systems, comprising only 0–15% of added 15N. DON and ammonium were effectively reduced by all biofilter designs, indicating effective mineralisation and nitrification rates. However, in designs with poor nitrogen removal, the effluent was enriched with nitrate, suggesting limited denitrification rates. Given the likely dominance of plant assimilation in removal, this indicates that plant selection is a critical design parameter, as is maintaining healthy plant growth for optimal nitrogen removal in greywater living wall biofilters in their early years of operation. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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Open AccessArticle Effects of Partial Root-Zone Irrigation on the Water Use Efficiency and Root Water and Nitrate Uptake of Corn
Water 2018, 10(4), 526; https://doi.org/10.3390/w10040526
Received: 24 November 2017 / Revised: 9 March 2018 / Accepted: 15 March 2018 / Published: 23 April 2018
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Abstract
Due to water shortages and the increasing need for food in recent years, the optimization of water consumption parameters, fertilizers, and food production are essential and a priority. The aim of this study is to investigate the effect of partial root-zone irrigation (PRI)
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Due to water shortages and the increasing need for food in recent years, the optimization of water consumption parameters, fertilizers, and food production are essential and a priority. The aim of this study is to investigate the effect of partial root-zone irrigation (PRI) methods on corn plant characteristics. The study also tried to measure the water use efficiency (WUE) of corn in pot cultivation and provide the best method of management in the fields of irrigation and fertigation. For this purpose, three irrigation methods, including alternate partial root-zone irrigation (APRI), fixed partial root-zone irrigation (FPRI), and conventional irrigation (CI) were studied in pots, and completely randomized blocks with eight replications were carried out. Each pot was evenly separated with plastic sheets into two sub-parts of equal volume, between which no water exchange occurred. The water content of the field capacity was calculated by the weighting method. The water requirement was provided daily, equal to 95% of the field capacity water content. Parameters including shoot and root dry weight, nitrate (N) uptake, the remaining nitrate in the soil, leaf area index, and WUE during the growing season were measured and compared. According to the results, the amount of saved water using the FPRI and APRI methods compared to the CI method were 28% and 32%, respectively. The highest and lowest WUE were observed as equal to 4.88 and 3.82 g/L using the APRI and CI methods, respectively, among which the CI method had the highest yield according to the amount of utilized water. Given the statistical examinations, there was no significant difference in the nitrate level of plants between CI and APRI, and the lowest uptake was observed in FPRI. Finally, considering indicators of yield production and WUE simultaneously, the APRI method was selected as the best method of management. Full article
(This article belongs to the Special Issue Advances in Agriculture Water Efficiency)
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Open AccessCommunication Individual Local Farmers’ Perceptions of Environmental Change in Tanzania
Water 2018, 10(4), 525; https://doi.org/10.3390/w10040525
Received: 7 February 2018 / Revised: 18 April 2018 / Accepted: 20 April 2018 / Published: 22 April 2018
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Abstract
Climatic and environmental changes are expected to affect in particular those regions where the economy is primarily based on the agricultural sector and where the dependency on water availability is high. This study examines how smallholder farmers in rural Tanzania perceived climatic and
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Climatic and environmental changes are expected to affect in particular those regions where the economy is primarily based on the agricultural sector and where the dependency on water availability is high. This study examines how smallholder farmers in rural Tanzania perceived climatic and environmental changes over the past 20 years and the resulting effects on water availability and food security. The study is based on a household survey of 899 farmers in a semi-arid and a sub-humid region in Tanzania. It was found that (a) significant differences in perceptions of the environment by farmers can be attributed to agro-climatic location, while the distance to a water source has less impact on individual perception; (b) differently perceived changes affect individual water availability and food security; and (c) the farm level adaptation methods applied are linked to vulnerability to changes and the household dependence on the immediate environment. The authors conclude that the specific environmental surroundings paired with socio-economic factors can severely compound the negative effects of water scarcity on rural farmers. Full article
(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)
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Open AccessArticle A Novel Multislope MUSCL Scheme for Solving 2D Shallow Water Equations on Unstructured Grids
Water 2018, 10(4), 524; https://doi.org/10.3390/w10040524
Received: 8 March 2018 / Revised: 15 April 2018 / Accepted: 19 April 2018 / Published: 21 April 2018
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Abstract
Within the framework of the two-dimensional cell-centered Godunov-type finite volume (CCFV) method, this paper presents a novel multislope scheme on the basis of the monotone upstream scheme for conservation law (MUSCL) for numerically solving nonlinear shallow water equations on two-dimensional triangular grids. The
[...] Read more.
Within the framework of the two-dimensional cell-centered Godunov-type finite volume (CCFV) method, this paper presents a novel multislope scheme on the basis of the monotone upstream scheme for conservation law (MUSCL) for numerically solving nonlinear shallow water equations on two-dimensional triangular grids. The Riemann states of the considered edge are calculated by an edge-based reconstructing procedure, where a limited scalar slope is employed to prevent potential numerical oscillations. The novel aspect of the new scheme is that it takes advantage of the geometrical characteristics of triangular grids in the reconstructing and limiting procedures, which effectively reduces the cost of computation and provides higher resolution and accuracy compared with classical MUSCL schemes. Seven tests are adopted to verify the scheme, and the results indicate that this scheme is efficient, accurate, robust, and high-resolution, and can be an ideal alternative for solving shallow water problems over uneven and frictional topography. Full article
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Open AccessFeature PaperArticle Comparison of Pressure-Driven Formulations for WDN Simulation
Water 2018, 10(4), 523; https://doi.org/10.3390/w10040523
Received: 24 March 2018 / Revised: 17 April 2018 / Accepted: 19 April 2018 / Published: 21 April 2018
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Abstract
This paper presents the comparison of five pressure-driven formulations in the context of water distribution network (WDN) modelling. These formulations, which relate nodal outflow q to users to demands d and nodal pressure heads h, were implemented inside the global gradient algorithm
[...] Read more.
This paper presents the comparison of five pressure-driven formulations in the context of water distribution network (WDN) modelling. These formulations, which relate nodal outflow q to users to demands d and nodal pressure heads h, were implemented inside the global gradient algorithm for the snapshot solution of the equations concerning mass and energy conservation at WDN nodes and pipes, respectively. The modelling of leakage nodal outflows as a function of pressure was also considered. The applications concerned two case studies, in which nodal demands were suitably amplified to lower service pressure below the desired values. This was done to stress the effects of the pressure-driven dependence q(h) in the WDN. The results showed that the formulations tend to behave similarly in terms of nodal outflows. Compared to a widely used formulation, which features a q(h) relationship with derivative discontinuities, the other four formulations analyzed tend to guarantee faster algorithm convergence, above all for simple and poorly interconnected WDNs, due to their smooth q(h) relationship. The results in terms of nodal pressure heads can be very different, above all for low values of h. Full article
(This article belongs to the Special Issue Advances in Water Distribution Networks)
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Open AccessFeature PaperArticle Some Aspects of Turbulent Mixing of Jets in the Marine Environment
Water 2018, 10(4), 522; https://doi.org/10.3390/w10040522
Received: 6 March 2018 / Revised: 8 April 2018 / Accepted: 13 April 2018 / Published: 21 April 2018
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Abstract
Prominent among environmental problems is the pollution of the coastal marine zone as a result of anthropogenic activities. On this point, while studies of jets in still water and in crossflows have been developed in many research centres, studies on jets interacting with
[...] Read more.
Prominent among environmental problems is the pollution of the coastal marine zone as a result of anthropogenic activities. On this point, while studies of jets in still water and in crossflows have been developed in many research centres, studies on jets interacting with waves are still rare. The present study analyses turbulent, non-buoyant water jets issued into a wave environment. A comparison of the time-averaged and phase-averaged velocity components has been carried out, in order to highlight the flow patterns in the two configurations. The experimental data have also been compared with others in the literature, such as the relationship between the dimensionless, longitudinal, time-averaged velocities of the jet mean axis and the distance from the source. Such comparisons reveal a good agreement. Furthermore, using the analogy between the equation of the turbulent transport of a solute concentration and the equation of the turbulent kinetic energy, the paper presents also estimates of the turbulence diffusion coefficients and advection terms of jets in a wave environment. The experimental results are compared with jets in still water. With the presence of waves, the turbulence length-scales in the streamwise direction vary, contributing to an increase in streamwise turbulent diffusion, relative to the condition of the same jet in still water. The analysis of the jet streamwise advection term reveals that it increases in the case of jets in a wave environment, as compared to no-wave conditions. Full article
(This article belongs to the Special Issue Turbulence in River and Maritime Hydraulics)
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Open AccessArticle Cover Crops for Managing Stream Water Quantity and Improving Stream Water Quality of Non-Tile Drained Paired Watersheds
Water 2018, 10(4), 521; https://doi.org/10.3390/w10040521
Received: 22 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 21 April 2018
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Abstract
In the Midwestern United States, cover crops are being promoted as a best management practice for managing nutrient and sediment losses from agricultural fields through surface and subsurface water movement. To date, the water quality benefits of cover crops have been inferred primarily
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In the Midwestern United States, cover crops are being promoted as a best management practice for managing nutrient and sediment losses from agricultural fields through surface and subsurface water movement. To date, the water quality benefits of cover crops have been inferred primarily from plot scale studies. This project is one of the first to analyze the impacts of cover crops on stream water quality at the watershed scale. The objective of this research was to evaluate nitrogen, phosphorus, and sediment loss in stream water from a no-till corn-soybean rotation planted with winter cover crops cereal rye (Secale cereale) and hairy vetch (Vicia villosa) in non-tile drained paired watersheds in Illinois, USA. The paired watersheds are under mixed land use (agriculture, forest, and pasture). The control watershed had 27 ha of row-crop agriculture, and the treatment watershed had 42 ha of row crop agriculture with cover crop treatment (CC-treatment). During a 4-year calibration period, 42 storm events were collected and Event Mean Concentrations (EMCs) for each storm event were calculated for total suspended solids (TSS), nitrate-N (NO3-N), ammonia-N (NH4-N), dissolved reactive phosphorus (DRP), and total discharge. Predictive regression equations developed from the calibration period were used for calculating TSS, NO3-N, NH4-N, and DRP losses of surface runoff for the CC-treatment watershed. The treatment period consisted of total 18 storm events, seven of which were collected during the cereal rye, eight in the hairy vetch cover crop season and three during cash crop season. Cover crops reduced TSS and discharge by 33% and 34%, respectively in the CC-treatment watershed during the treatment period. However, surprisingly, EMCs for NO3-N, NH4-N, and DRP did not decrease. Stream discharge from the paired-watersheds will continue to be monitored to determine if the current water quality results hold or new patterns emerge. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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Open AccessArticle Seasonal and Interannual Variability in Coastal Circulations in the Northern South China Sea
Water 2018, 10(4), 520; https://doi.org/10.3390/w10040520
Received: 13 March 2018 / Revised: 15 April 2018 / Accepted: 19 April 2018 / Published: 21 April 2018
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Abstract
Seasonal cycle and interannual variability in coastal circulations in the northern South China Sea (NSCS) are investigated using satellite altimeter data from March 1993 to September 2016. Altimeter-derived velocity anomalies are in good agreement with acoustic Doppler current profilers (ADCP) observations at an
[...] Read more.
Seasonal cycle and interannual variability in coastal circulations in the northern South China Sea (NSCS) are investigated using satellite altimeter data from March 1993 to September 2016. Altimeter-derived velocity anomalies are in good agreement with acoustic Doppler current profilers (ADCP) observations at an adjacent location. Along-shelf volume transport anomalies in the NSCS indicate northeastward transports from mid-spring to summer and southwestward transports from mid-autumn to winter, which are consistent with previous studies in this region. According to convergence and divergence in the target control volumes, cross-shelf volume transports are estimated as the differences between two neighboring along-shelf volume transport anomalies, with the assumption that long-term mean along-shelf volume transports at each cross-sections are identical. The results show onshore transports in mid-autumn and offshore transports in early summer. The comparison between altimeter-derived and ADCP-estimated cross-shelf volume transports is encouraging, especially when the region has relatively low mesoscale activities and a low freshwater input. Reconstructed cross-shelf volume transports through multiple linear regression reveal that seasonal harmonics is the primary force in driving cross-shelf volume transports in the NSCS, while wind and El Niño have secondary effects on controlling cross-shelf volume transports in different regions. The present study helps to quantify the long-term coastal circulations, especially cross-shelf volume transports, based on altimeter data, which has important implications on the dynamics in coastal regions where observational data is limited. Full article
(This article belongs to the Section Hydrology)
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