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Water, Volume 9, Issue 5 (May 2017)

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Cover Story (view full-size image) Global warming causes rapid shrinking of mountain glaciers and the formation of numerous new lakes. [...] Read more.
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Open AccessArticle Understanding the Role of Groundwater in a Remote Transboundary Lake (Hulun Lake, China)
Water 2017, 9(5), 363; https://doi.org/10.3390/w9050363
Received: 14 January 2017 / Revised: 8 April 2017 / Accepted: 4 May 2017 / Published: 22 May 2017
Cited by 3 | PDF Full-text (1293 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hulun Lake, located in a remote, semi-arid area in the northeast part of Inner Mongolia, China, shares a transboundary basin with Mongolia and supports a unique wetland ecosystem that includes many endangered species. Decadal scale decreases in the lake stage and increased salinity
[...] Read more.
Hulun Lake, located in a remote, semi-arid area in the northeast part of Inner Mongolia, China, shares a transboundary basin with Mongolia and supports a unique wetland ecosystem that includes many endangered species. Decadal scale decreases in the lake stage and increased salinity make an understanding of the lake’s water and salt sources critical for appropriate design of strategies to protect and manage the lake. Multiple tracers (chloride, and δ18O and δ2H in water) in samples collected from lake water, rivers, and nearby water wells were used in conjunction with an annual water balance based on historic data to better understand the lake’s major water and salt sources. The average annual water balance was conducted for two time periods: 1981–2000 and 2001–2013. The contribution of river discharge to the annual lake input decreased by half (from 64% to 31%) between the two time periods, while the volumetric contribution of groundwater discharge increased four-fold (from about 11% to about 50% of the total lake input). Significant evaporation was apparent in the stable isotope composition of the present-day lake water, however, evaporation alone could not account for the high lake water chloride concentrations. Limited domestic well water sampling, a regional salinity survey, and saline soils suggest that high chloride groundwater concentrations exist in the region south of the lake. The chloride mass balance suggested that groundwater currently contributes more than 90% of the annual chloride loading to the lake, which is likely four times greater than the earlier period (1981–2000) with lower groundwater input. The use of water and chloride mass balances combined with water isotope analyses could be applied to other watersheds where hydrologic information is scarce. Full article
(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)
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Open AccessFeature PaperArticle Thermal and Physical Investigations into Lake Deepening Processes on Spillway Lake, Ngozumpa Glacier, Nepal
Water 2017, 9(5), 362; https://doi.org/10.3390/w9050362
Received: 15 March 2017 / Revised: 1 May 2017 / Accepted: 15 May 2017 / Published: 22 May 2017
Cited by 1 | PDF Full-text (5949 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper investigates physical processes in the four sub-basins of Ngozumpa glacier’s terminal Spillway Lake for the period 2012–2014 in order to characterize lake deepening and mass transfer processes. Quantifying the growth and deepening of this terminal lake is important given its close
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This paper investigates physical processes in the four sub-basins of Ngozumpa glacier’s terminal Spillway Lake for the period 2012–2014 in order to characterize lake deepening and mass transfer processes. Quantifying the growth and deepening of this terminal lake is important given its close vicinity to Sherpa villages down-valley. To this end, the following are examined: annual, daily and hourly temperature variations in the water column, vertical turbidity variations and water level changes and map lake floor sediment properties and lake floor structure using open water side-scan sonar transects. Roughness and hardness maps from sonar returns reveal lake floor substrates ranging from mud, to rocky debris and, in places, bare ice. Heat conduction equations using annual lake bottom temperatures and sediment properties are used to calculate bottom ice melt rates (lake floor deepening) for 0.01 to 1-m debris thicknesses. In areas of rapid deepening, where low mean bottom temperatures prevail, thin debris cover or bare ice is present. This finding is consistent with previously reported localized regions of lake deepening and is useful in predicting future deepening. Full article
(This article belongs to the Special Issue Global Warming Impacts on Mountain Glaciers and Communities)
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Open AccessArticle Upscaling Stem to Community-Level Transpiration for Two Sand-Fixing Plants: Salix gordejevii and Caragana microphylla
Water 2017, 9(5), 361; https://doi.org/10.3390/w9050361
Received: 20 November 2016 / Revised: 7 May 2017 / Accepted: 19 May 2017 / Published: 22 May 2017
Cited by 2 | PDF Full-text (1929 KB) | HTML Full-text | XML Full-text
Abstract
The information on transpiration is vital for sustaining fragile ecosystem in arid/semiarid environment, including the Horqin Sandy Land (HSL) located in northeast China. However, such information is scarce in existing literature. The objectives of this study were to: (1) measure sap flow of
[...] Read more.
The information on transpiration is vital for sustaining fragile ecosystem in arid/semiarid environment, including the Horqin Sandy Land (HSL) located in northeast China. However, such information is scarce in existing literature. The objectives of this study were to: (1) measure sap flow of selected individual stems of two sand-fixing plants, namely Salix gordejevii and Caragana microphylla, in HSL; and (2) upscale the measured stem-level sap flow for estimating the community-level transpiration. The measurements were done from 1 May to 30 September 2015 (i.e., during the growing season). The upscaling function was developed to have one dependent variable, namely sap flow rate, and two independent variables, namely stem cross-sectional area of Salix gordejevii and leaf area of Caragana microphylla. The results indicated that during the growing season, the total actual transpiration of the Salix gordejevii and Caragana microphylla communities was found to be 287 ± 31 and 197 ± 24 mm, respectively, implying that the Salix gordejevii community might consume 1.5 times more water than the Caragana microphylla community. For this same growing season, based on the Penman–Monteith equation, the total actual evapotranspiration for these two communities was estimated to be 323 and 229 mm, respectively. The daily transpiration from the upscaling function was well correlated with the daily evapotranspiration by the Penman–Monteith equation (coefficient of determination R2 ≥ 0.67), indicating the applicability of this upscaling function, a useful tool for managing and restoring sand-fixing vegetations. Full article
(This article belongs to the Special Issue Water-Soil-Vegetation Dynamic Interactions in Changing Climate)
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Open AccessArticle Rooftop Rainwater Harvesting for Mombasa: Scenario Development with Image Classification and Water Resources Simulation
Water 2017, 9(5), 359; https://doi.org/10.3390/w9050359
Received: 28 February 2017 / Revised: 5 May 2017 / Accepted: 15 May 2017 / Published: 20 May 2017
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Abstract
Mombasa faces severe water scarcity problems. The existing supply is unable to satisfy the demand. This article demonstrates the combination of satellite image analysis and modelling as tools for the development of an urban rainwater harvesting policy. For developing a sustainable remedy policy,
[...] Read more.
Mombasa faces severe water scarcity problems. The existing supply is unable to satisfy the demand. This article demonstrates the combination of satellite image analysis and modelling as tools for the development of an urban rainwater harvesting policy. For developing a sustainable remedy policy, rooftop rainwater harvesting (RRWH) strategies were implemented into the water supply and demand model WEAP (Water Evaluation and Planning System). Roof areas were detected using supervised image classification. Future population growth, improved living standards, and climate change predictions until 2035 were combined with four management strategies. Image classification techniques were able to detect roof areas with acceptable accuracy. The simulated annual yield of RRWH ranged from 2.3 to 23 million cubic meters (MCM) depending on the extent of the roof area. Apart from potential RRWH, additional sources of water are required for full demand coverage. Full article
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Open AccessFeature PaperArticle Exploring Streamwater Mixing Dynamics via Handheld Thermal Infrared Imagery
Water 2017, 9(5), 358; https://doi.org/10.3390/w9050358
Received: 7 March 2017 / Revised: 12 May 2017 / Accepted: 15 May 2017 / Published: 19 May 2017
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Abstract
Stream confluences are important hotspots of aquatic ecological processes. Water mixing dynamics at stream confluences influence physio-chemical characteristics of the stream as well as sediment mobilisation and pollutant dispersal. In this study, we investigated the potential for handheld thermal infrared (TIR) imagery to
[...] Read more.
Stream confluences are important hotspots of aquatic ecological processes. Water mixing dynamics at stream confluences influence physio-chemical characteristics of the stream as well as sediment mobilisation and pollutant dispersal. In this study, we investigated the potential for handheld thermal infrared (TIR) imagery to provide rapid information on stream water mixing dynamics at small scales. In-situ visualisation of water mixing patterns can help reduce analytical errors related to stream water sampling locations and improve our understanding of how confluences and tributaries influence aquatic ecological communities. We compared TIR-inferred stream temperature distributions with water electrical conductivity and temperature (measured with a submerged probe) data from cross-channel transects. We show that the use of a portable TIR camera can enhance the visualisation of mixing dynamics taking place at stream confluences, identify the location of the mixing front between two different water sources and the degree of mixing. Interpretation of handheld TIR observations also provided information on how stream morphology and discharge can influence mixing dynamics in small streams. Overall, this study shows that TIR imagery is a valuable support technique for eco-hydrological investigation at small stream confluences. Full article
(This article belongs to the Special Issue New Developments in Methods for Hydrological Process Understanding)
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Open AccessFeature PaperArticle Shoreline Changes on the Wave-Influenced Senegal River Delta, West Africa: The Roles of Natural Processes and Human Interventions
Water 2017, 9(5), 357; https://doi.org/10.3390/w9050357
Received: 24 December 2016 / Revised: 10 April 2017 / Accepted: 12 May 2017 / Published: 19 May 2017
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Abstract
The Senegal River delta in West Africa, one of the finest examples of “wave-influenced” deltas, is bounded by a spit periodically breached by waves, each breach then acting as a shifting mouth of the Senegal River. Using European Re-Analysis (ERA) hindcast wave data
[...] Read more.
The Senegal River delta in West Africa, one of the finest examples of “wave-influenced” deltas, is bounded by a spit periodically breached by waves, each breach then acting as a shifting mouth of the Senegal River. Using European Re-Analysis (ERA) hindcast wave data from 1984 to 2015 generated by the Wave Atmospheric Model (WAM) of the European Centre for Medium-Range Weather Forecasts (ECMWF), we calculated longshore sediment transport rates along the spit. We also analysed spit width, spit migration rates, and changes in the position and width of the river mouth from aerial photographs and satellite images between 1954 and 2015. In 2003, an artificial breach was cut through the spit to prevent river flooding of the historic city of St. Louis. Analysis of past spit growth rates and of the breaching length scale associated with maximum spit elongation, and a reported increase in the frequency of high flood water levels between 1994 and 2003, suggest, together, that an impending natural breach was likely to have occurred close to the time frame of the artificial 2003 breach. Following this breach, the new river mouth was widened rapidly by flood discharge evacuation, but stabilised to its usual hydraulic width of <2 km. In 2012, severe erosion of the residual spit downdrift of the mouth may have been due to a significant drop (~15%) in the longshore sand transport volume and to a lower sediment bypassing fraction across the river mouth. This wave erosion of the residual spit led to rapid exceptional widening of the mouth to ~5 km that has not been compensated by updrift spit elongation. This wider mouth may now be acting as a large depocentre for sand transported alongshore from updrift, and has contributed to an increase in the tidal influence affecting the lower delta. Wave erosion of the residual spit has led to the destruction of villages, tourist facilities and infrastructure. This erosion of the spit has also exposed part of the delta plain directly to waves, and reinforced the saline intrusion within the Senegal delta. Understanding the mechanisms and processes behind these changes is important in planning of future shoreline management and decision-making regarding the articulations between coastal protection offered by the wave-built spit and flooding of the lower delta plain of the Senegal River. Full article
(This article belongs to the Special Issue Sediment Transport in Coastal Waters)
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Open AccessArticle The Use of Molluscan Fauna as Model Taxon for the Ecological Classification of River Estuaries
Water 2017, 9(5), 356; https://doi.org/10.3390/w9050356
Received: 21 March 2017 / Revised: 5 May 2017 / Accepted: 9 May 2017 / Published: 18 May 2017
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Abstract
River estuaries are important aquatic environments characterized by large environmental gradients in their water quality, riverbed material, and microtopography in the longitudinal and transverse directions. The geography or habitats in river estuaries differ depending on the energy from the tide, waves, and river;
[...] Read more.
River estuaries are important aquatic environments characterized by large environmental gradients in their water quality, riverbed material, and microtopography in the longitudinal and transverse directions. The geography or habitats in river estuaries differ depending on the energy from the tide, waves, and river; therefore, the biota inhabiting river estuaries vary depending on the river estuary type. In view of this, for effective conservation in river estuaries, there is a need for information about potential habitats and biota based on objective data about the river estuary type. The objective of this study thus was to classify river estuaries by their molluscan fauna and physical indicators to reveal the relationship between molluscan fauna and the physical environment. The classification results using physical indicators indicated three types of river estuaries (wave energy-dominated group, tide energy-dominated group, and low tide and wave energy group). This classification result was similar to the classification of molluscan fauna. Therefore, it was suggested that molluscan fauna is extremely useful as a variable representing the river estuary environment. From the comparison between molluscan fauna and the physical environment, some rivers were not classified into the same group in the classification of molluscan fauna, despite them having similar physical environments. Some of these rivers with a molluscan fauna that diverged from expectations had undergone channel modification, which is expected to have caused a shift in this fauna group. These results suggest that this approach could be used to identify rivers that have been degraded by human activities. Full article
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Open AccessArticle Contamination of Detained Sediment in Sustainable Urban Drainage Systems
Water 2017, 9(5), 355; https://doi.org/10.3390/w9050355
Received: 24 March 2017 / Revised: 13 May 2017 / Accepted: 16 May 2017 / Published: 18 May 2017
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Abstract
Adsorption is a key water pollution remediation measure used to achieve stormwater quality improvement in Sustainable urban Drainage Systems (SuDS). The level of contamination of detained sediment within SuDS assets is not well documented, with published investigations limited to specific contaminant occurrence in
[...] Read more.
Adsorption is a key water pollution remediation measure used to achieve stormwater quality improvement in Sustainable urban Drainage Systems (SuDS). The level of contamination of detained sediment within SuDS assets is not well documented, with published investigations limited to specific contaminant occurrence in ponds, wetlands or infiltration devices (bioretention cells) and generally focused on solute or suspended sediment. Guidance on contamination threshold levels and potential deposited sediment contamination information is not included in current UK SuDS design or maintenance guidance, primarily due to a lack of evidence and understanding. There is a need to understand possible deposited sediment contamination levels in SuDS, specifically in relation to sediment removal maintenance activities and potential impact on receiving waterways of conveyed sediment. Thus, the objective of the research presented herein was to identify what major elements and trace metals were observable in (the investigated) SuDS assets detained sediment, the concentration of these major elements and trace metals and whether they met/surpassed ecotoxicity or contaminated land thresholds. The research presented here provides evidence of investigated SuDS sediment major element and trace metal levels to help inform guidance and maintenance needs, and presents a new methodology to identify the general cause (anthropocentric land use) and extent of detained SuDS fine urban sediment contamination through use of a contamination matrix. Full article
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Open AccessArticle Soil Moisture Stochastic Model in Pinus tabuliformis Forestland on the Loess Plateau, China
Water 2017, 9(5), 354; https://doi.org/10.3390/w9050354
Received: 25 March 2017 / Revised: 6 May 2017 / Accepted: 15 May 2017 / Published: 18 May 2017
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Abstract
As an important restrictive factor of ecological construction on the Loess Plateau, the study of soil moisture dynamics is essential, especially under the impact of climate change on hydrological processes. In this study, the applicability of the Laio soil moisture stochastic model on
[...] Read more.
As an important restrictive factor of ecological construction on the Loess Plateau, the study of soil moisture dynamics is essential, especially under the impact of climate change on hydrological processes. In this study, the applicability of the Laio soil moisture stochastic model on a typical plantation Pinus tabuliformis forestland on the Loess Plateau was studied. On the basis of data concerning soil properties, climate, and plants of the typical forestland during the period 2005–2015 in the Chinese National Ecosystem Research Network (Ji County Station) in Ji County, Shanxi, model results were acquired and compared with observed soil moisture from 2005 to 2015 in the study area. The genetic algorithm method was used to optimize model parameters in the calibration process. In the calibration and validation periods, the relative error between numerical characteristics of simulated and observed soil moisture values was mostly within 10%, and model evaluation index J was close to 1, indicating that the Laio model had good applicability in the study area. When calibrating the model, it was recommended to use soil moisture data with a sampling interval of no more than 10 days so as to reduce the loss of soil moisture fluctuation information. In the study area, the Laio model was strongly sensitive to variations of input parameters, including maximum evapotranspiration rate Emax, average rainfall depth α, and average rainfall frequency λ, which should be paid more attention for stable and reliable simulation results. This study offers a method to obtain soil moisture data at ungauged sites. Results from this study provide guidance for Laio model application on the Loess Plateau. Full article
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Open AccessArticle Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu
Water 2017, 9(5), 352; https://doi.org/10.3390/w9050352
Received: 14 March 2017 / Revised: 5 May 2017 / Accepted: 12 May 2017 / Published: 18 May 2017
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Abstract
Light absorption by phytoplankton, non-algal particles (NAP) and chromophoric dissolved organic matter (CDOM) was investigated at 90 sites of a clear, deep artificial lake (Lake Qiandaohu) to study natural variability of absorption coefficients. Our study shows that CDOM absorption is a
[...] Read more.
Light absorption by phytoplankton, non-algal particles (NAP) and chromophoric dissolved organic matter (CDOM) was investigated at 90 sites of a clear, deep artificial lake (Lake Qiandaohu) to study natural variability of absorption coefficients. Our study shows that CDOM absorption is a major contributor to the total absorption signal in Lake Qiandaohu during all seasons, except autumn when it has an equivalent contribution as total particle absorption. The exponential slope of CDOM absorption varies within a narrow range around a mean value of 0.0164 nm−1 ( s d = 0.00176 nm−1). Our study finds some evidence for thIS autochthonous production of CDOM in winter and spring. Absorption by phytoplankton, and therefore its contribution to total absorption, is generally greatest in spring, suggesting that phytoplankton growth in Lake Qiandaohu occurs predominantly in the spring. Phytoplankton absorption in freshwater lakes generally has a direct relationship with chlorophyll-a concentration, similar to the one established for open ocean waters. The NAP absorption, whose relative contribution to total absorption is highest in summer, has a spectral shape that can be well fitted by an exponential function with an average slope of 0.0065 nm−1 ( s d = 0.00076 nm−1). There is significant spatial variability present in the summer of Lake Qiandaohu, especially in the northwestern and southwestern extremes where the optical properties of the water column are strongly affected by the presence of allochthonous matter. Variations in the properties of the particle absorption spectra with depths provides evidence that the water column was vertically inhomogeneous and can be monitored with an optical measurement program. Moreover, the optical inhomogeneity in winter is less obvious. Our study will support the parameterization of the Bio-optical model for Lake Qiandaohu from in situ or remotely sensing aquatic color signals. Full article
(This article belongs to the Special Issue Water Quality Monitoring and Modeling in Lakes)
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Open AccessFeature PaperArticle A Semi-Infinite Interval-Stochastic Risk Management Model for River Water Pollution Control under Uncertainty
Water 2017, 9(5), 351; https://doi.org/10.3390/w9050351
Received: 14 March 2017 / Revised: 20 April 2017 / Accepted: 12 May 2017 / Published: 18 May 2017
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Abstract
In this study, a semi-infinite interval-stochastic risk management (SIRM) model is developed for river water pollution control, where various policy scenarios are explored in response to economic penalties due to randomness and functional intervals. SIRM can also control the variability of the recourse
[...] Read more.
In this study, a semi-infinite interval-stochastic risk management (SIRM) model is developed for river water pollution control, where various policy scenarios are explored in response to economic penalties due to randomness and functional intervals. SIRM can also control the variability of the recourse cost as well as capture the notion of risk in stochastic programming. Then, the SIRM model is applied to water pollution control of the Xiangxihe watershed. Tradeoffs between risks and benefits are evaluated, indicating any change in the targeted benefit and risk level would yield varied expected benefits. Results disclose that the uncertainty of system components and risk preference of decision makers have significant effects on the watershed's production generation pattern and pollutant control schemes as well as system benefit. Decision makers with risk-aversive attitude would accept a lower system benefit (with lower production level and pollutant discharge); a policy based on risk-neutral attitude would lead to a higher system benefit (with higher production level and pollutant discharge). The findings can facilitate the decision makers in identifying desired product generation plans in association with financial risk minimization and pollution mitigation. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessFeature PaperLetter Reversed Currents in Charged Liquid Bridges
Water 2017, 9(5), 353; https://doi.org/10.3390/w9050353
Received: 24 March 2017 / Revised: 10 May 2017 / Accepted: 15 May 2017 / Published: 17 May 2017
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Abstract
The velocity profile in a water bridge is reanalyzed. Assuming hypothetically that the bulk charge has a radial distribution, a surface potential is formed that is analogous to the Zeta potential. The Navier–Stokes equation is solved, neglecting the convective term; then, analytically and
[...] Read more.
The velocity profile in a water bridge is reanalyzed. Assuming hypothetically that the bulk charge has a radial distribution, a surface potential is formed that is analogous to the Zeta potential. The Navier–Stokes equation is solved, neglecting the convective term; then, analytically and for special field and potential ranges, a sign change of the total mass flow is reported caused by the radial charge distribution. Full article
(This article belongs to the Special Issue Electrohydrodynamic Liquid Bridges and Electrified Water)
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Open AccessArticle Mapping Dynamic Water Fraction under the Tropical Rain Forests of the Amazonian Basin from SMOS Brightness Temperatures
Water 2017, 9(5), 350; https://doi.org/10.3390/w9050350
Received: 23 February 2017 / Revised: 9 May 2017 / Accepted: 11 May 2017 / Published: 17 May 2017
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Abstract
Inland surface waters in tropical environments play a major role in the water and carbon cycle. Remote sensing techniques based on passive, active microwave or optical wavelengths are commonly used to provide quantitative estimates of surface water extent from regional to global scales.
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Inland surface waters in tropical environments play a major role in the water and carbon cycle. Remote sensing techniques based on passive, active microwave or optical wavelengths are commonly used to provide quantitative estimates of surface water extent from regional to global scales. However, some of these estimates are unable to detect water under dense vegetation and/or in the presence of cloud coverage. To overcome these limitations, the brightness temperature data at L-band frequency from the Soil Moisture and Ocean Salinity (SMOS) mission are used here to estimate flood extent in a contextual radiative transfer model over the Amazon Basin. At this frequency, the signal is highly sensitive to the standing water above the ground, and the signal provides information from deeper vegetation density than higher-frequencies. Three-day and (25 km × 25 km) resolution maps of water fraction extent are produced from 2010 to 2015. The dynamic water surface extent estimates are compared to altimeter data (Jason-2), land cover classification maps (IGBP, GlobeCover and ESA CCI) and the dynamic water surface product (GIEMS). The relationships between the water surfaces, precipitation and in situ discharge data are examined. The results show a high correlation between water fraction estimated by SMOS and water levels from Jason-2 (R > 0.98). Good spatial agreements for the land cover classifications and the water cycle are obtained. Full article
(This article belongs to the Special Issue The Use of Remote Sensing in Hydrology) Printed Edition available
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Open AccessArticle Using δ15N and δ18O Signatures to Evaluate Nitrate Sources and Transformations in Four Inflowing Rivers, North of Taihu Lake
Water 2017, 9(5), 345; https://doi.org/10.3390/w9050345
Received: 28 February 2017 / Revised: 8 May 2017 / Accepted: 8 May 2017 / Published: 17 May 2017
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Abstract
Taihu Lake is the third largest freshwater lake in China. Due to rapid economic development and excessive nutrient discharges, there is serious eutrophication in the northern part of the lake. Nitrogen (N) is one of the key factors for eutrophication in Taihu Lake,
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Taihu Lake is the third largest freshwater lake in China. Due to rapid economic development and excessive nutrient discharges, there is serious eutrophication in the northern part of the lake. Nitrogen (N) is one of the key factors for eutrophication in Taihu Lake, which mainly comes from the rivers around the lake. Samples from four inflowing rivers were analysed for δ15N and δ18O isotopes in December 2013 to identify the different sources of nitrogen in the northern part of Taihu Lake. The results indicated that the water quality in Taihu Lake was clearly influenced by the water quality of the inflowing rivers and nitrate (NO3-N) was the main component of the soluble inorganic nitrogen in water. The soil organic N represented more than 70% of the total NO3-N loads in the Zhihugang. Domestic sewage was the major NO3-N source in the Liangxi river, with a contribution of greater than 50%. Soil organic N and domestic sewage, with contributions of more than 30% and 35% respectively, were the major NO3-N sources in the Lihe river and Daxigang river. Denitrification might be responsible for the shifting δ15N-NO3 and δ18O-NO3 values in the Daxigang river, and a mixing process may play a major role in N transformations in the Lihe river in winter. The results of this study will be useful as reference values for reducing NO3 pollution in the inflowing rivers in the north of Taihu Lake. Full article
(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)
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Open AccessFeature PaperArticle Impacts of Accumulated Particulate Organic Matter on Oxygen Consumption and Organic Micro-Pollutant Elimination in Bank Filtration and Soil Aquifer Treatment
Water 2017, 9(5), 349; https://doi.org/10.3390/w9050349
Received: 29 March 2017 / Revised: 2 May 2017 / Accepted: 9 May 2017 / Published: 16 May 2017
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Abstract
Bank filtration (BF) and soil aquifer treatment (SAT) are efficient natural technologies in potable water reuse systems. The removal of many organic micro-pollutants (OMPs) depends on redox-conditions in the subsoil, especially on the availability of molecular oxygen. Due to microbial transformation of particulate
[...] Read more.
Bank filtration (BF) and soil aquifer treatment (SAT) are efficient natural technologies in potable water reuse systems. The removal of many organic micro-pollutants (OMPs) depends on redox-conditions in the subsoil, especially on the availability of molecular oxygen. Due to microbial transformation of particulate and dissolved organic constituents, oxygen can be consumed within short flow distances and induce anoxic and anaerobic conditions. The effect of accumulated particulate organic carbon (POC) on the fate of OMPs in BF and SAT systems is not fully understood. Long-term column experiments with natural sediment cores from the bank of Lake Tegel and from a SAT basin were conducted to investigate the impact of accumulated POC on dissolved organic carbon (DOC) release, on oxygen consumption, on mobilization of iron and manganese, and on the elimination of the organic indicator OMPs. The cores were fed with aerated tap water spiked with OMPs to exclude external POC inputs. Complete oxygen consumption within the first infiltration decimeter in lake sediments caused mobilization of iron, manganese, and DOC. Redox-sensitive OMPs like diclofenac, sulfamethoxazole, formylaminoantipyrine, and gabapentin were eliminated by more than 50% in all sediment cores, but slightly higher residual concentrations were measured in effluents from lake sediments, indicating a negative impact of a high oxygen consumption on OMP removal. Full article
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