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Water, Volume 10, Issue 5 (May 2018)

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Cover Story (view full-size image) This detailed study of 35-year snowpack trends in the vicinity of Rocky Mountain National Park [...] Read more.
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Open AccessArticle Assessing the Influence of the Three Gorges Dam on Hydrological Drought Using GRACE Data
Water 2018, 10(5), 669; https://doi.org/10.3390/w10050669
Received: 17 April 2018 / Revised: 19 May 2018 / Accepted: 19 May 2018 / Published: 22 May 2018
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Abstract
With worldwide economic and social development, more dams are being constructed to meet the increasing demand for hydropower, which may considerably influence hydrological drought. Here, an index named the “Dam Influence Index” (DII) is proposed to assess the influence of the Three Gorges
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With worldwide economic and social development, more dams are being constructed to meet the increasing demand for hydropower, which may considerably influence hydrological drought. Here, an index named the “Dam Influence Index” (DII) is proposed to assess the influence of the Three Gorges Dam (TGD) on hydrological drought in the Yangtze River Basin (YRB) in China. First, the total terrestrial water storage (TTWS) is derived from Gravity Recovery and Climate Experiment data. Then, the natural-driven terrestrial water storage (NTWS) is predicted from the soil moisture, precipitation, and temperature data based on an artificial neural network model. Finally, the DII is derived using the empirical (Kaplan-Meier) cumulative distribution function of the differences between the TTWS and the NTWS. The DIIs of the three sub-basins in the YRB were 1.38, −4.66, and −7.32 between 2003 and 2008, which indicated an increase in TTWS in the upper sub-basin and a reduction in the middle and lower sub-basins. According to the results, we concluded that impoundments of the TGD between 2003 and 2008 slightly alleviated the hydrological drought in the upper sub-basin and significantly aggravated the hydrological drought in the middle and lower sub-basins, which is consistent with the Palmer Drought Severity Index. This study provides a new perspective for estimating the effects of large-scale human activities on hydrological drought and a scientific decision-making basis for the managing water resources over the operation of the TGD. Full article
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Open AccessFeature PaperArticle Alaska Snowpack Response to Climate Change: Statewide Snowfall Equivalent and Snowpack Water Scenarios
Water 2018, 10(5), 668; https://doi.org/10.3390/w10050668
Received: 30 March 2018 / Revised: 19 May 2018 / Accepted: 21 May 2018 / Published: 22 May 2018
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Abstract
Climatically driven changes in snow characteristics (snowfall, snowpack, and snowmelt) will affect hydrologic and ecological systems in Alaska over the coming century, yet there exist no projections of downscaled future snow pack metrics for the state of Alaska. We updated historical and projected
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Climatically driven changes in snow characteristics (snowfall, snowpack, and snowmelt) will affect hydrologic and ecological systems in Alaska over the coming century, yet there exist no projections of downscaled future snow pack metrics for the state of Alaska. We updated historical and projected snow day fraction (PSF, the fraction of days with precipitation falling as snow) from McAfee et al. We developed modeled snowfall equivalent (SFE) derived from the product of snow-day fraction (PSF) and existing gridded precipitation for Alaska from Scenarios Network for Alaska and Arctic Planning (SNAP). We validated the assumption that modeled SFE approximates historical decadally averaged snow water equivalent (SWE) observations from snowcourse and Snow Telemetry (SNOTEL) sites. We present analyses of future downscaled PSF and two new products, October–March SFE and ratio of snow fall equivalent to precipitation (SFE:P) based on bias-corrected statistically downscaled projections of Coupled Model Intercomparison Project 5 (CMIP5) Global Climate Model (GCM) temperature and precipitation for the state of Alaska. We analyzed mid-century (2040–2069) and late-century (2070–2099) changes in PSF, SFE, and SFE:P relative to historical (1970–1999) mean temperature and present results for Alaska climate divisions and 12-digit Hydrologic Unit Code (HUC12) watersheds. Overall, estimated historical the SFE is reasonably well related to the observed SWE, with correlations over 0.75 in all decades, and correlations exceeding 0.9 in the 1960s and 1970s. In absolute terms, SFE is generally biased low compared to the observed SWE. PSF and SFE:P decrease universally across Alaska under both Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 emissions scenarios, with the smallest changes for RCP 4.5 in 2040–2069 and the largest for RCP 8.5 in 2070–2099. The timing and magnitude of maximum decreases in PSF vary considerably with regional average temperature, with the largest changes in months at the beginning and end of the snow season. Mean SFE changes vary widely among climate divisions, ranging from decreases between −17 and −58% for late twenty-first century in southeast, southcentral, west coast and southwest Alaska to increases up to 21% on the North Slope. SFE increases most at highest elevations and latitudes and decreases most in coastal southern Alaska. SFE:P ratios indicate a broad switch from snow-dominated to transitional annual hydrology across most of southern Alaska by mid-century, and from transitional to rain-dominated watersheds in low elevation parts of southeast Alaska by the late twenty-first century. Full article
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Open AccessArticle Performance of Two Advanced Rainwater Harvesting Systems in Washington DC
Water 2018, 10(5), 667; https://doi.org/10.3390/w10050667
Received: 29 March 2018 / Revised: 18 May 2018 / Accepted: 20 May 2018 / Published: 22 May 2018
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Abstract
Combined sewer overflows (CSOs) are a concern for many cities managing stormwater through combined sewer systems, including the District of Columbia (DC). Advanced rainwater harvesting (ARH) is an innovative approach to managing stormwater and has the potential to minimize CSOs and maximize water
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Combined sewer overflows (CSOs) are a concern for many cities managing stormwater through combined sewer systems, including the District of Columbia (DC). Advanced rainwater harvesting (ARH) is an innovative approach to managing stormwater and has the potential to minimize CSOs and maximize water conservation. ARH systems use continuous monitoring and adaptive control (CMAC) technology to store or release water from a rainwater harvesting cistern. This study assessed the efficacy of ARH systems to mitigate wet weather discharges at two firehouses in DC. Continuous monitoring data was collected over a period of three years for the systems that were installed in 2012. The collected data indicates that the systems were effective at mitigating wet weather discharges, with average event harvesting rates greater than 95%. These results suggest that if implemented on a larger scale, ARH systems would be a valuable tool in effectively managing stormwater. Full article
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Open AccessArticle Simulation of Crop Growth and Water-Saving Irrigation Scenarios for Lettuce: A Monsoon-Climate Case Study in Kampong Chhnang, Cambodia
Water 2018, 10(5), 666; https://doi.org/10.3390/w10050666
Received: 19 March 2018 / Revised: 12 May 2018 / Accepted: 16 May 2018 / Published: 21 May 2018
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Abstract
Setting up water-saving irrigation strategies is a major challenge farmers face, in order to adapt to climate change and to improve water-use efficiency in crop productions. Currently, the production of vegetables, such as lettuce, poses a greater challenge in managing effective water irrigation,
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Setting up water-saving irrigation strategies is a major challenge farmers face, in order to adapt to climate change and to improve water-use efficiency in crop productions. Currently, the production of vegetables, such as lettuce, poses a greater challenge in managing effective water irrigation, due to their sensitivity to water shortage. Crop growth models, such as AquaCrop, play an important role in exploring and providing effective irrigation strategies under various environmental conditions. The objectives of this study were (i) to parameterise the AquaCrop model for lettuce (Lactuca sativa var. crispa L.) using data from farmers’ fields in Cambodia, and (ii) to assess the impact of two distinct full and deficit irrigation scenarios in silico, using AquaCrop, under two contrasting soil types in the Cambodian climate. Field observations of biomass and canopy cover during the growing season of 2017 were used to adjust the crop growth parameters of the model. The results confirmed the ability of AquaCrop to correctly simulate lettuce growth. The irrigation scenario analysis suggested that deficit irrigation is a “silver bullet” water saving strategy that can save 20–60% of water compared to full irrigation scenarios in the conditions of this study. Full article
(This article belongs to the Special Issue Water Management for Sustainable Food Production)
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Open AccessArticle Simulation of Soil Water Content in Mediterranean Ecosystems by Biogeochemical and Remote Sensing Models
Water 2018, 10(5), 665; https://doi.org/10.3390/w10050665
Received: 14 March 2018 / Revised: 10 May 2018 / Accepted: 16 May 2018 / Published: 19 May 2018
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Abstract
The current study assesses the potential of two modeling approaches to simulate the daily site water budget in Mediterranean ecosystems. Both models utilize a simplified one-bucket approach but are fed with different drivers. The first model, BIOME-BGC, simulates all main biogeochemical fluxes based
[...] Read more.
The current study assesses the potential of two modeling approaches to simulate the daily site water budget in Mediterranean ecosystems. Both models utilize a simplified one-bucket approach but are fed with different drivers. The first model, BIOME-BGC, simulates all main biogeochemical fluxes based on conventional meteorological and ancillary data, while the second uses evapotranspiration estimates derived from the combination of meteorological data and satellite normalized difference vegetation index (NDVI) images. The two models were tested for three Italian sites which are characterized by different vegetation types and ecoclimatic conditions: (i) low mountain coniferous forest; (ii) hilly deciduous forest; (iii) urban grassland. The soil water balance simulated by the two models was evaluated through comparison with daily measurements of soil water content (SWC) taken during a growing season. Satisfactory results were obtained in all cases by both approaches; the SWC estimates are significantly correlated with the measurements (correlation coefficient, r, higher than 0.74), and the mean errors are lower than 0.079 cm3 cm−3. The second model, however, generally shows a higher accuracy, which is dependent on the quality of the NDVI data utilized (r higher than 0.79 and errors lower than 0.059 cm3 cm−3). The study therefore provides useful indications for the application of these and similar simulation methods in different environmental situations. Full article
(This article belongs to the Special Issue Monitoring and Predicting Soil Moisture and Drought Conditions)
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Open AccessArticle The Water–Energy–Food Nexus: A Fuzzy-Cognitive Mapping Approach to Support Nexus-Compliant Policies in Andalusia (Spain)
Water 2018, 10(5), 664; https://doi.org/10.3390/w10050664
Received: 6 April 2018 / Revised: 1 May 2018 / Accepted: 15 May 2018 / Published: 19 May 2018
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Abstract
Water, energy and food are essential resources for economic development and social well-being. Framing integrated policies that improve their efficient use requires understanding the interdependencies in the water–energy–food (WEF) nexus. Stakeholder involvement in this process is crucial to represent multiple perspectives, ensure political
[...] Read more.
Water, energy and food are essential resources for economic development and social well-being. Framing integrated policies that improve their efficient use requires understanding the interdependencies in the water–energy–food (WEF) nexus. Stakeholder involvement in this process is crucial to represent multiple perspectives, ensure political legitimacy and promote dialogue. In this research, we develop and apply a participatory modelling approach to identify the main interlinkages within the WEF nexus in Andalusia, as a starting point to developing a system dynamic model at a later stage. The application of fuzzy cognitive mapping enabled us to gain knowledge on the WEF nexus according to opinions from 14 decision-makers, as well as contributing to raising awareness and building consensus among stakeholders. Results show that climate change and water availability are key drivers in the WEF nexus in Andalusia. Other variables with significant interlinkages within the WEF nexus are food production, irrigated agriculture, energy cost, socio-economic factors, irrigation water use, environmental conservation, and farm performance indicators. The scenario analysis reveals the interdependencies among nexus sectors and the existence of unanticipated effects when changing variables in the system, which need to be considered to design integrated policies. Full article
(This article belongs to the Special Issue Innovation Issues in Water, Agriculture and Food)
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Open AccessArticle TWI Computations and Topographic Analysis of Depression-Dominated Surfaces
Water 2018, 10(5), 663; https://doi.org/10.3390/w10050663
Received: 25 March 2018 / Revised: 21 April 2018 / Accepted: 17 May 2018 / Published: 19 May 2018
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Abstract
The topographic wetness index (TWI) has been widely used for determining the potential of each digital elevation model (DEM) grid to develop a saturated condition, which allows for the investigation of topographic control on the hydrologic response of a watershed. Many studies have
[...] Read more.
The topographic wetness index (TWI) has been widely used for determining the potential of each digital elevation model (DEM) grid to develop a saturated condition, which allows for the investigation of topographic control on the hydrologic response of a watershed. Many studies have evaluated TWI, its components, and the impacts of DEM resolution on its computation. However, the majority of the studies are concerned with typical dendritic watersheds, and the effectiveness of TWI computations for depression-dominated areas has been rarely evaluated. The objectives of this study are (1) to develop a modified TWI computation procedure for depression-dominated areas, (2) to examine the differences between the new and existing TWI computation procedures using different DEMs, and (3) to assess the impact of DEM resolution on the new TWI procedure. In particular, a bathymetry survey was conducted for a study area in the Prairie Pothole Region (PPR), and the DEM representing the actual surface topography was created. The statistical analyses of TWI highlighted a two-hump pattern for the depression-dominated surface, whereas a one-hump pattern was observed for the dendritic surface. It was observed that depressional DEM grids accounted for higher values of TWI than other grids. It was demonstrated that a filled DEM led to misleading quantity and distribution of TWI for depression-dominated landscapes. The modified TWI computation procedure proposed in this study can also be applied to other depression-dominated areas. Full article
(This article belongs to the Section Hydrology)
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Open AccessArticle Research on Fuzzy Cooperative Game Model of Allocation of Pollution Discharge Rights
Water 2018, 10(5), 662; https://doi.org/10.3390/w10050662
Received: 29 March 2018 / Revised: 13 May 2018 / Accepted: 16 May 2018 / Published: 19 May 2018
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Abstract
The allocation of pollution rights is significant to the economic development of a region, which determines the industrial structure of the region in another way. This study established an allocation model based on fuzzy coalition game theory. Formation of fuzzy coalitions between many
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The allocation of pollution rights is significant to the economic development of a region, which determines the industrial structure of the region in another way. This study established an allocation model based on fuzzy coalition game theory. Formation of fuzzy coalitions between many producers in a region and reallocation of pollution discharge rights in the region through these coalitions was used to increase the total production value of the region while total pollution discharge amount is constant. At the same time, the fuzzy Shapley value method was used to allocate benefits obtained from the cooperation to the participants in various coalitions. This model was validated by its application in the case of three production bases near the Shizi channel in Dongguan city for reallocation of pollution discharge rights. Results showed that this model could increase the coalition benefits of the three production bases in this region, which observed increases of 4.28%, 7.74%, and 13.98%, respectively. Full article
(This article belongs to the Special Issue Water Quality: A Component of the Water-Energy-Food Nexus)
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Open AccessArticle Stream Health Evaluation Using a Combined Approach of Multi-Metric Chemical Pollution and Biological Integrity Models
Water 2018, 10(5), 661; https://doi.org/10.3390/w10050661
Received: 13 April 2018 / Revised: 27 April 2018 / Accepted: 15 May 2018 / Published: 18 May 2018
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Abstract
Bouchung Stream is a large tributary of the Geum River watershed that is simultaneously affected by wastewater treatment plant effluents and agricultural activities in the watershed area. The focal subject was to diagnose the chemical and biological health of the temperate stream by
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Bouchung Stream is a large tributary of the Geum River watershed that is simultaneously affected by wastewater treatment plant effluents and agricultural activities in the watershed area. The focal subject was to diagnose the chemical and biological health of the temperate stream by using a combined approach of the multi-metric water pollution index (WPI) and the index of biological integrity (IBIKR), using datasets from 2008–2014. Water chemistry analyses indicated seasonal and inter-annual variations mainly linked to the intensity of monsoon rainfall in the watershed, potentially causing the availability of agricultural runoff water. The main events of phosphorus inflow and nitrogen dilutions occurred during July–August. Temporal and spatial heterogeneities were observed and were largely recognizable due to nutrient enrichment and organic matter intensification. Chlorophyll showed weak linear relation to total phosphorus (R2 = 0.17) but no relation to total nitrogen (p > 0.05). Fish compositions analyzed as trophic/tolerance guilds in relation to water chemistry showed visible decline and modifications. Average WPI site scores ranged from 33–23, indicating an excellent upstream to fair downstream water quality status. Correspondingly, IBIKR scores ranged between 38–28 approximating with WPI site classification, as well as both indices showed higher regression relation (R2 = 0.90). Fish guild analyses revealed tolerant and omnivore species dominating the downstream, while sensitive and insectivores depleting in approximation with changing water chemistry and was confirmed by the principal component analysis. In addition, the fish guilds meticulously responded to phosphorus inflows. In conclusion, overall stream health and water chemistry analyses indicated continuous chemical and biological degradation influencing the trophic and tolerance fish guilds. Moreover, the combined application approach of WPI and IBIKR could help in better understanding the chemical and biological mechanisms in rivers and streams. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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Open AccessArticle Assessment of Key Environmental Factors Influencing the Sedimentation and Aggregation Behavior of Zinc Oxide Nanoparticles in Aquatic Environment
Water 2018, 10(5), 660; https://doi.org/10.3390/w10050660
Received: 1 May 2018 / Revised: 14 May 2018 / Accepted: 15 May 2018 / Published: 18 May 2018
Cited by 1 | PDF Full-text (4381 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Zinc oxide nanoparticles (ZnO NPs) are among the most widely used engineered nanoparticles (ENPs) in various commercial sectors to achieve both social and economic benefits. The post-use release of these NPs to the environment is inevitable, and may pose threat to the human
[...] Read more.
Zinc oxide nanoparticles (ZnO NPs) are among the most widely used engineered nanoparticles (ENPs) in various commercial sectors to achieve both social and economic benefits. The post-use release of these NPs to the environment is inevitable, and may pose threat to the human and eco-system. In the present study, we investigated the influence of single and multiple environmental factors on sedimentation behavior of ZnO NPs. The fractional-factorial method based on Taguchi orthogonal array (OA) L27(313) design matrix was used for systematic investigation on the contribution and significance of multiple factors and their interactions. The result of single-factor showed that the ZnO NPs were unstable at or near pHzpc, with high electrolyte concentration; however, the adsorption of natural organic matter (NOM) i.e., humic acid, salicylic acid, and citric acid reverses the surface charge and enhanced NP stability. The Fourier transform infrared (FT-IR) analysis confirms the organic capping ligands on the NP surface. Moreover, the matrix result of analysis of variance (ANOVA) showed that electrolyte concentration and type, and NOM concentration were the most significant factors (p < 0.001) in promoting and influencing aggregation, while the interaction between the factors was also found insignificant. In addition, the result of aggregation kinetics and environmental water samples indicated that the mobility of ENPs may vary substantially in an environment with complex and heterogeneous matrices. This study may contribute to better understanding and prediction of the sedimentation behavior and fate of ZnO NPs in aqueous environments, to facilitate their sustainable use in products and process. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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Open AccessArticle Satellite-Based, Multi-Indices for Evaluation of Agricultural Droughts in a Highly Dynamic Tropical Catchment, Central Vietnam
Water 2018, 10(5), 659; https://doi.org/10.3390/w10050659
Received: 23 January 2018 / Revised: 13 May 2018 / Accepted: 15 May 2018 / Published: 18 May 2018
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Abstract
Characterization of droughts using satellite-based data and indices in a steep, highly dynamic tropical catchment, like Vu Gia Thu Bon, which is the most important basin in central Vietnam, has remained a challenge for many years. This study examined the six widely used
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Characterization of droughts using satellite-based data and indices in a steep, highly dynamic tropical catchment, like Vu Gia Thu Bon, which is the most important basin in central Vietnam, has remained a challenge for many years. This study examined the six widely used vegetation indices (VIs) to effectively monitor droughts that are based on their sensitivity with precipitation, soil moisture, and their linkage with the impacts on agricultural crop production and forest fires. Six VIs representing the four main groups, including greenness-based VIs (Vegetation Condition Index), water-based VIs (Normalized Difference Water Index, Land Surface Water Index), temperature-based VIs (Temperature Condition Index), and combined VIs (Vegetation Health Index, Normalized Difference Drought Index) were tested using MODIS data from January 2001 to December 2016 with the support of cloud-based Google Earth Engine computational platform. Results showed that droughts happened almost every year, but with different intensity. Vegetation stress was found to be mainly attributed to precipitation in the rice paddy fields and to temperature in the forest areas. Findings revealed that combined vegetation indices were more sensitive drought indicators in the basin, whereas their performance was different by vegetation type. In the rice paddy fields, NDDI was more sensitive to precipitation than other indices; it better captured droughts and their impacts on crop yield. In the forest areas, VHI was more sensitive to temperature, and thus had better performance than other VIs. Accordingly, NDDI and VHI were recommended for monitoring droughts in the agricultural and forest lands, respectively. The findings from this study are crucial to map drought risks and prepare an effective mitigation plan for the basin. Full article
(This article belongs to the Special Issue Applications of Remote Sensing and GIS in Hydrology)
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Open AccessArticle Measuring the Value of Farmland-Elevating Engineering in the Reservoir Area of a Key Water Conservancy Project in China
Water 2018, 10(5), 658; https://doi.org/10.3390/w10050658
Received: 25 March 2018 / Revised: 5 May 2018 / Accepted: 14 May 2018 / Published: 18 May 2018
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Abstract
With the development and construction of key water conservancy projects, many problems such as population migration in reservoir areas have become increasingly grave in China. The implementation of farmland-elevating engineering has become an effective way to reduce the loss of cultivated land, prevent
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With the development and construction of key water conservancy projects, many problems such as population migration in reservoir areas have become increasingly grave in China. The implementation of farmland-elevating engineering has become an effective way to reduce the loss of cultivated land, prevent soil erosion, and ensure food security and social stability. On the basis of the key technical analysis of farmland-elevating engineering, this paper constructed a value system of farmland-elevating engineering from aspects of social value, ecological value, and economic value and established corresponding measurement models, respectively. Taking a key water conservancy project in Jiangxi province as an example, this paper measures the value of farmland-elevating engineering implemented in this project. The results show that the implementation of farmland-elevating engineering can produce great value. This study aims to provide reliable references for the decision-making regarding farmland-elevating engineering. Full article
(This article belongs to the Section Water–Food–Energy Nexus)
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Open AccessArticle Evaluation and Bias Correction of Satellite-Based Rainfall Estimates for Modelling Flash Floods over the Mediterranean region: Application to Karpuz River Basin, Turkey
Water 2018, 10(5), 657; https://doi.org/10.3390/w10050657
Received: 16 March 2018 / Revised: 30 April 2018 / Accepted: 14 May 2018 / Published: 18 May 2018
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Abstract
This study investigates the utility of satellite-based rainfall estimates in simulating flash floods in Karpuz River Basin, Turkey, characterized by limited rain gauge network. Global Satellite Mapping of Precipitation (GSMaP) product was evaluated with the rain gauge network at daily and monthly time-scales
[...] Read more.
This study investigates the utility of satellite-based rainfall estimates in simulating flash floods in Karpuz River Basin, Turkey, characterized by limited rain gauge network. Global Satellite Mapping of Precipitation (GSMaP) product was evaluated with the rain gauge network at daily and monthly time-scales considering seasonality, elevation zones, extreme events and rainfall intensity thresholds. Statistical analysis indicated that GSMaP shows acceptable linear correlation coefficient with rain gauges, however, suffers from significant underestimation bias. Statistical measures exhibited a remarkable deterioration with increasing elevation-following a linear relationship; for example, percent bias was found to increase by a rate of 11.7% with every 400 m interval. A multiplicative bias correction scheme was devised, and Hydrological River Basin Environmental Assessment Model (Hydro-BEAM) was implemented to simulate flash floods driven by the uncorrected/corrected GSMaP data. Analysis of intensity thresholds revealed that appropriate threshold selection is critically important for the bias correction procedure. The hydrological model was calibrated for flash flood events during October–December 2007 and 2012 and validated during October–December, 2009 and 2010. Flash floods simulations were improved by the local bias correction procedure applied to the GSMaP data, but the degree of improvement varied from one period to another. The results of the study indicate that bias factors incorporating multiple variables such as extreme events and elevation variability have the potential to further improve flood simulations. Full article
(This article belongs to the Section Hydrology)
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Open AccessArticle Temperature Rise of Seawater Simulation under the Influence of Sediment-Water Heat Exchange
Water 2018, 10(5), 656; https://doi.org/10.3390/w10050656
Received: 12 March 2018 / Revised: 5 May 2018 / Accepted: 16 May 2018 / Published: 18 May 2018
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Abstract
Alternating inundation and exposure of large tidal flats regions suggest that differences in thermodynamic properties of sediment and water cause an obvious heat exchange between the tidal sediment and seawater. Due to the influence of these sediment-water heat exchanges, the temperature of seawater
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Alternating inundation and exposure of large tidal flats regions suggest that differences in thermodynamic properties of sediment and water cause an obvious heat exchange between the tidal sediment and seawater. Due to the influence of these sediment-water heat exchanges, the temperature of seawater changes dramatically in coastal areas. To understand and assess the effect of these heat exchanges on seawater temperature, a temperature rise numerical model is adopted to describe the influence of sediment-water heat exchange. The heat exchange is determined mainly by the temperature difference between the sediment and seawater. Thus, a sediment temperature model is developed to predict the temperature of tidal sediment and sediment-water heat flux under the alternating inundated or exposed condition. The surface sediment temperature, as the surface boundary condition of the model, is calculated by the heat balance at the surface, including solar radiation, atmospheric radiation, flat back radiation, latent, and sensible heat fluxes, soil heat flux, and sediment-water heat flux. The collected measured data of sediment temperature are used to verify the accuracy of the sediment temperature model. Based on this, the predicted sediment-water heat flux is provide to the temperature rise model. In the study site, the tidal flat of about 15.8 km2 is adopted in the sediment temperature model, and the simulated time is from 11 to 31 May 2017 to meet the collected climate data. The results show that a clear temperature rise water area comes out near the shore considering the heat flux. In warmer season, the maximum water temperature rise is about 2 °C in the local area, and in the envelope area of a 1 °C temperature rise can reach 2.8 km2. Certainly, the influence will be stronger after the simulated time moves into the middle of summer with stronger solar radiation. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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Open AccessArticle Evaluation of a UAV-Assisted Autonomous Water Sampling
Water 2018, 10(5), 655; https://doi.org/10.3390/w10050655
Received: 10 April 2018 / Revised: 8 May 2018 / Accepted: 15 May 2018 / Published: 18 May 2018
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Abstract
Water quality assessment programs for the management of water resources require the collection of water samples for physical, chemical, and biological analyses. Lack of personnel, accessibility of water bodies, and time constraints, especially after natural disasters and emergencies, are some of the challenges
[...] Read more.
Water quality assessment programs for the management of water resources require the collection of water samples for physical, chemical, and biological analyses. Lack of personnel, accessibility of water bodies, and time constraints, especially after natural disasters and emergencies, are some of the challenges of water sampling. To overcome these challenges, a custom-made thief-style water sampling mechanism was developed and mounted on a multirotor unmanned aerial vehicle (UAV) for autonomous water sampling. The payload capacity and endurance of the UAV were determined using an indoor test station. The UAV was equipped with floatation, and electronic components were coated to prevent water damage in the event of a forced landing or for sample collection. Water samples from a 1.1 ha pond were collected with the developed UAV-assisted water sampling system and traditional manual methods. Dissolved oxygen (DO), electrical conductivity (EC), pH, temperature and chloride measurements were made on samples collected with both UAV-assisted and manual methods and compared. Percent differences between the two sampling methods for DO, EC, pH, and temperature were minimal except for chloride level. Percent differences between the two sampling methods for DO, EC, pH, and temperature measurements were 3.6%, 2.3%, 0.76%, and 0.03%, respectively. Measured chloride levels for the manual and UAV-assisted sampling methods were 3.97 and 5.46 mg/L. UAV-assisted water sampling may prove faster and safer than manual water sampling from large surface waters and from difficult to access water bodies. Full article
(This article belongs to the Section Water Quality and Ecosystems)
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