Water

1293 KiB

Open AccessArticle

Understanding the Role of Groundwater in a Remote Transboundary Lake (Hulun Lake, China)

by Hongbin Gao, M. Cathryn Ryan, Changyou Li and Biao Sun

Water 2017, 9(5), 363; https://doi.org/10.3390/w9050363 - 22 May 2017

Cited by 22 | Viewed by 6437

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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(a) Study area in country-scale map, with a green star indicating the location of the International Atomic Energy Agency’s Global Network of Isotopes in Precipitation (Qiqihar station); (b) Hulun Lake basin showing two major rivers (Kelulun River and Wuerxun River) that flow into Hulun Lake, and the Xinkai River, which intermittently provides an outlet for Hulun Lake to the Hailaer River; (c) River, domestic water well, and lake sampling site locations. The arrow near Hailaer River shows the flow direction of Hailaer River. The Xinkai River is an intermittent connection between Hulun Lake and the Hailaer River. Full article ">Figure 2
Dual isotope diagram of δ18O and δ2H in lake, river, and domestic water well samples. The local meteoric water line (LMWL) is shown for the International Atomic Energy Agency’s Global Network of Isotopes in Precipitation, Qiqihar station [<a href="#B42-water-09-00363" class="html-bibr">42</a>]. Full article ">Figure 3
A cross plot of δ18O values and chloride concentrations in lakes, rivers and wells. Zone I and Zone II are divided based on the significant difference in chloride concentrations in western and southern wells, respectively. Full article ">Figure 4
δ18O vs. chloride concentrations including the minimum, average, and maximum values for total input into Hulun Lake (filled black symbols; <a href="#water-09-00363-t003" class="html-table">Table 3</a>), measured Hulun Lake values, and average values for each of the main three inputs (precipitation, river flow, and groundwater) that are thought to contribute to the combined input (with solid arrows indicating likely inputs, and the dashed arrow represents potential sources). The dashed lines represent δ18O and chloride concentration evolution with increasing evaporation modeled by E/I ratios as described in <a href="#sec2dot4-water-09-00363" class="html-sec">Section 2.4</a> (with T = 0.3 °C, and humidity = 60%). Full article ">Figure 5
The spatial distribution of salinity (g/L) in domestic water well samples around Hulun Lake. Unpublished data (collected in 2008), College of Water Resources and Civil Engineering, Inner Mongolia Agricultural University. Full article ">

5949 KiB

Open AccessFeature PaperArticle

Thermal and Physical Investigations into Lake Deepening Processes on Spillway Lake, Ngozumpa Glacier, Nepal

by Ulyana Nadia Horodyskyj

Water 2017, 9(5), 362; https://doi.org/10.3390/w9050362 - 22 May 2017

Cited by 2 | Viewed by 6426

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 [...] Read more.

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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1929 KiB

Open AccessArticle

Upscaling Stem to Community-Level Transpiration for Two Sand-Fixing Plants: Salix gordejevii and Caragana microphylla

by Limin Duan, Yang Lv, Xue Yan, Tingxi Liu and Xixi Wang

Water 2017, 9(5), 361; https://doi.org/10.3390/w9050361 - 22 May 2017

Cited by 7 | Viewed by 4810

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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6267 KiB

Open AccessArticle

Rooftop Rainwater Harvesting for Mombasa: Scenario Development with Image Classification and Water Resources Simulation

by Robert O. Ojwang, Jörg Dietrich, Prajna Kasargodu Anebagilu, Matthias Beyer and Franz Rottensteiner

Water 2017, 9(5), 359; https://doi.org/10.3390/w9050359 - 20 May 2017

Cited by 16 | Viewed by 13171

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

(This article belongs to the Special Issue Rainwater Harvesting: Quantity, Quality, Economics and State Regulations)

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3490 KiB

Open AccessFeature PaperArticle

Exploring Streamwater Mixing Dynamics via Handheld Thermal Infrared Imagery

by Marta Antonelli, Julian Klaus, Keith Smettem, Adriaan J. Teuling and Laurent Pfister

Water 2017, 9(5), 358; https://doi.org/10.3390/w9050358 - 19 May 2017

Cited by 4 | Viewed by 6162

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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Location (map) and overview (pictures) of the study sites. Top: location within Luxemburg and the Attert basin. Middle: overview of the natural stream confluence (NAT site). Bottom: overview of the urban stream confluence (URB site). Location of crossing transect A is displayed on both pictures (NAT site: folding meter ruler; URB site: bold white line). The pictures were collected on the 28 September 2016 at the NAT site and the 2 February 2017 at the URB site (pictures: M. Antonelli). Full article ">Figure 2
Cross-sectional characteristics. (A) Examples of TIR images collected at two cross-sectional transects. Note that the TIR images cover a smaller domain for illustrative purposes; when possible, we covered the widest transect width with a single TIR image (pictures: M. Antonelli); (B) Stream depth profiles at the two cross-sectional transects. In the NAT site, the width of the stream at the transects increased with increasing discharge, expanding exclusively on the left side of the stream. The presence of coarse sediment in the stream makes the depth profiles at the same location highly variable. In the URB site, the stream width increased with increasing discharge expanding uniformly on the left and right bank. Full article ">Figure 3
Illustration of the analysis procedure. TIR images (top panel) and cross-sectional temperature distribution as collected in the individual transects. The shown temperature distribution was extracted from the image collected on the 28 September at the NAT site (transect A) (pictures: M. Antonelli). Full article ">Figure 4
Example of stream conductivity and temperature. Upper and middle panels: stream EC and temperature (measured at the stream bottom—“bottom”—and near the surface—“top”). Lower panel: TIR-inferred temperature distributions. At the NAT site (21 September) we found a good correlation between the TIR distribution and stream EC (R2 = −0.96) and temperature data (R2 = 0.96) (on this date, collected only on the bottom because of low water depth). At the URB site (2 February) we found a poor correlation between the TIR distribution and stream EC (bottom: R2 = 0.49; top: R2 = 0.70) and temperature data (bottom: R2 = 0.47; top: R2 = 0.59). For the temperature data measured near the stream surface (URB site) it was not possible to determine a univocal inflection point. Full article ">Figure 5
Illustration of circular “aura” effect. The “aura” is visible at the edges of the TIR image (NAT—Transect A—17 November) and directly affects the extraction of TIR temperature cross-sectional distributions (as can be seen in the software output). Full article ">Figure 6
Mixing widths for different stream cross-channel transects. The mixing widths were calculated from the curves obtained via data smoothing of TIR-inferred stream temperature and water EC and temperature measured at the bottom and near the surface, and are expressed as percentage of the total transect width. No value fields in the NAT graphs indicate that water depth was too low for obtaining measurements near the water surface. Full article ">

6100 KiB

Open AccessFeature PaperArticle

Shoreline Changes on the Wave-Influenced Senegal River Delta, West Africa: The Roles of Natural Processes and Human Interventions

by Mamadou Sadio, Edward J. Anthony, Amadou Tahirou Diaw, Philippe Dussouillez, Jules T. Fleury, Alioune Kane, Rafael Almar and Elodie Kestenare

Water 2017, 9(5), 357; https://doi.org/10.3390/w9050357 - 19 May 2017

Cited by 42 | Viewed by 10811

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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The coast of West Africa, showing the Senegal (box) and other major river deltas. Much of this coast is wave-dominated, and is characterised by beach-ridge sand barriers and spits. Full article ">Figure 2
The Senegal River delta, a fine example of a wave-dominated delta characterised by the Langue de Barbarie spit and a river-mouth system subject to strong north-south longshore drift. Full article ">Figure 3
Mean wave characteristics (significant wave height (Hs), peak wave period (T), and incident direction (°)) along the Senegal River delta coast from 1984 to 2015 ERA hindcast data. Orange: swell waves, blue: wind waves. Full article ">Figure 4
Gross annual longshore sediment transport (LST) along the Senegal River delta coast from 1984 to 2015. Orange: swell waves, blue: wind waves. Note the significant drop in swell-induced LST between 2009 and 2012, corresponding to a decrease of >35%, and the sharp rise the following year. Full article ">Figure 5
Successive dated locations of the mouth of the Senegal River delta materialised by the distal tip of the Langue de Barbarie spit (left); and spit migration rates in m/year from 1968 to 2004 (right). Full article ">Figure 6
Width of the mouth of the Senegal River delta between 1954 and 2015. Except for the years 1968–1973 and 1987–1988, the width did not exceed 1 km, prior to the 2003 artificial breach. Following this breach, the width of the mouth fluctuated to attain ~1 km in 2008, which corresponds to the average width of the “fluvial” river mouth. A further rapid increase, not related to river-mouth hydraulics (see Discussion), occurred thereafter, peaking in 2013. Full article ">Figure 7
Maximum water levels in the Senegal River channel at St. Louis from 1999 to 2006. Adapted from [<a href="#B34-water-09-00357" class="html-bibr">34</a>]. Full article ">Figure 8
Ground photographs showing the initial trench (4 October 2003), dug on the night of 3 October 2003, across the Langue de Barbarie to alleviate flooding of parts of St. Louis. The 5 October 2003 photograph shows the trench considerably widened by river and tidal flow (Photo credit: Service régional de l’Hydraulique, St. Louis du Sénégal). Full article ">Figure 9
Assemblage from Google Earth images showing changes in the Langue de Barbarie spit and Senegal River mouth between March 2003, prior to the October 2003 artificial breach, and 2015. Black: Langue de Barbarie spit and beach sand; dark grey: subaerial lower delta plain potentially subject to river flooding (including St. Louis); light grey: delta plain seasonally flooded by the Senegal River. From 2012 to 2013, rapid wave-induced erosion of the residual spit downdrift of the mouth led to considerable mouth widening, an increase in tidal influence within the lower Senegal delta, and direct wave attack of parts of the delta plain hitherto protected by the residual spit. Full article ">Figure 9 Cont.
Assemblage from Google Earth images showing changes in the Langue de Barbarie spit and Senegal River mouth between March 2003, prior to the October 2003 artificial breach, and 2015. Black: Langue de Barbarie spit and beach sand; dark grey: subaerial lower delta plain potentially subject to river flooding (including St. Louis); light grey: delta plain seasonally flooded by the Senegal River. From 2012 to 2013, rapid wave-induced erosion of the residual spit downdrift of the mouth led to considerable mouth widening, an increase in tidal influence within the lower Senegal delta, and direct wave attack of parts of the delta plain hitherto protected by the residual spit. Full article ">Figure 10
Significant heights (Hs) of high-energy waves (±1.6 standard deviations around mean Hs) from 1999 to 2015 (top); and number of days per year with high-energy waves along the Senegal River delta coast, derived from ERA hindcast data (bottom). Orange: swell waves (Hs ≥ 2.37 m), blue: wind waves (Hs ≥ 1.36 m). Note the significant drop in high-energy swell waves in 2012 (see also <a href="#water-09-00357-f004" class="html-fig">Figure 4</a>). Full article ">

2030 KiB

Open AccessArticle

The Use of Molluscan Fauna as Model Taxon for the Ecological Classification of River Estuaries

by Rei Itsukushima, Kai Morita and Yukihiro Shimatani

Water 2017, 9(5), 356; https://doi.org/10.3390/w9050356 - 18 May 2017

Cited by 8 | Viewed by 4814

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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2480 KiB

Open AccessArticle

Contamination of Detained Sediment in Sustainable Urban Drainage Systems

by Deonie Allen, Heather Haynes and Scott Arthur

Water 2017, 9(5), 355; https://doi.org/10.3390/w9050355 - 18 May 2017

Cited by 8 | Viewed by 6347

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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A comparison of deposited sediment contaminant concentrations for the wetland (a), linear wetland (b), short swale (c), long swale (d) and pond (e). Red bars indicated the exceedance of contaminated land thresholds and have no upper limit, blue bars indicate exceedance of ecotoxicity levels and green bars indicate sediment contaminant levels below ecotoxicity thresholds. Where no contaminated land thresholds are presented in guidance documents, the blue and red bars are vacant from the graphs. Field data falling within the red bars indicate exceedance of contaminated land threshold trigger and therefore may be of concern. Full article ">Figure 2
Sediment contaminant concentrations from monitoring points across the SuDS assets. The error bars illustrate sample range for each sample location and contaminant. Sediment contaminants have been presented relative to one of their primary urban sources (e.g., tyre wear) for ease graphical clarity. Full article ">Figure 3
Deposited sediment within the investigated SuDS assets. Full article ">Figure 4
Modal particle size for deposited sediment within the investigated SuDS assets. Full article ">Figure 5
Sediment contamination matrix. The matrix is comprised of three layers of colour indicators, illustrating the alphabetic contamination matrix code (e.g., HHHH, as illustrated to the top right of the matrix). Full article ">

3720 KiB

Open AccessArticle

Soil Moisture Stochastic Model in Pinus tabuliformis Forestland on the Loess Plateau, China

by Yi-Fang Chang, Hua-Xing Bi, Qing-Fu Ren, Hua-Sen Xu, Zhi-Cai Cai, Dan Wang and Wen-Chao Liao

Water 2017, 9(5), 354; https://doi.org/10.3390/w9050354 - 18 May 2017

Cited by 10 | Viewed by 4418

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 E_max, 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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5924 KiB

Open AccessArticle

Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu

by Liangliang Shi, Zhihua Mao, Jiaping Wu, Mingliang Liu, Yiwei Zhang and Zheng Wang

Water 2017, 9(5), 352; https://doi.org/10.3390/w9050352 - 18 May 2017

Cited by 13 | Viewed by 7023

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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2087 KiB

Open AccessFeature PaperArticle

A Semi-Infinite Interval-Stochastic Risk Management Model for River Water Pollution Control under Uncertainty

by Jing Liu, Yongping Li, Guohe Huang and Yurui Fan

Water 2017, 9(5), 351; https://doi.org/10.3390/w9050351 - 18 May 2017

Cited by 2 | Viewed by 5734

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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Figure 1
Overall flow chat of the methodology. Full article ">Figure 2
Study area. Note: GF, Gufu chemical plant; XL, Xinglong phosphorus mining company; XH, Xinghe phosphorus mining company; XC, Xingchang phosphorus mining company; BSH, Baishahe chemical plant; PYK, Pingyikou chemical plant; LCP, Liucaopo chemical plant; GP, Geping phosphorus mining company; JJW, Jiangjiawan phosphorus mining company; SJS, Shenjiashan phosphorus mining company; XJLY, Xiangjinlianying chemical plant. Full article ">Figure 3
Benefits and costs under different risk levels. Note: (a) lower-bound targeted benefit and system benefit, (b) upper-bound targeted benefit and system benefit, (c) lower-bound regular benefit and penalty, (d) upper-bound regular benefit and penalty; unit: 106 RMB¥. Full article ">Figure 4
Benefit corresponding to each scenario and risk level. (a) Lower bound and (b) Upper bound. Full article ">Figure 5
Cumulative risk curve ((a) Lower bound and (b) Upper bound). Full article ">Figure 6
Proportion of benefit under different scenarios. (a) Lower bound under low scenario; (b) Upper bound under low scenario; (c) Lower bound under low-medium scenario; (d) Upper bound under low-medium scenario; (e) Lower bound under medium scenario; (f) Upper bound under medium scenario; (g) Lower bound under medium-high scenario; (h) Upper bound under medium-high scenario; (i) Lower bound under high scenario and (j) Upper bound under high scenario. Full article ">Figure 7
Actual production levels of industrial activities. Note: (a) lower-bound production level of chemical plant; (b) upper-bound production level of chemical plant; (c) lower-bound production level of phosphorus mining company; (d) upper-bound production level of phosphorus mining company; (e) lower-bound water supply and (f) upper-bound water supply. Full article ">Figure 8
Excess Pollutant Discharge. (a) BOD discharge; (b) TP discharge and (c) TN discharge. Full article ">

4650 KiB

Open AccessFeature PaperLetter

Reversed Currents in Charged Liquid Bridges

by Klaus Morawetz

Water 2017, 9(5), 353; https://doi.org/10.3390/w9050353 - 17 May 2017

Cited by 2 | Viewed by 4386

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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The total mass flow (<a href="#FD20-water-09-00353" class="html-disp-formula">20</a>) vs. the dimensionless radius of the bridge. The parameter <math display="inline"> <semantics> <mrow> <mn>8</mn> <mi>ζ</mi> <mo>/</mo> <msub> <mi>ζ</mi> <mn>0</mn> </msub> </mrow> </semantics> </math> = <math display="inline"> <semantics> <mrow> <mn>1</mn> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>10</mn> <mo>,</mo> <mn>12</mn> </mrow> </semantics> </math> from left to right. The numbered points represent the regions for which the velocity profile is given in <a href="#water-09-00353-f003" class="html-fig">Figure 3</a>. Full article ">Figure 2
The critical parameter <math display="inline"> <semantics> <msub> <mrow> <mo>(</mo> <mi>κ</mi> <mi>R</mi> <mo>)</mo> </mrow> <mn>0</mn> </msub> </semantics> </math> where the mass flow changes the sign vs. the <math display="inline"> <semantics> <mi>ζ</mi> </semantics> </math> potential. The shaded area is the region where the flow reverses the sign. Full article ">Figure 3
The radial velocity profile for the three numbered points of <a href="#water-09-00353-f001" class="html-fig">Figure 1</a>. Full article ">

1446 KiB

Open AccessArticle

Mapping Dynamic Water Fraction under the Tropical Rain Forests of the Amazonian Basin from SMOS Brightness Temperatures

by Marie Parrens, Ahmad Al Bitar, Frédéric Frappart, Fabrice Papa, Stephane Calmant, Jean-François Crétaux, Jean-Pierre Wigneron and Yann Kerr

Water 2017, 9(5), 350; https://doi.org/10.3390/w9050350 - 17 May 2017

Cited by 34 | Viewed by 8123

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. [...] Read more.

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)

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1739 KiB

Open AccessArticle

Using δ¹⁵N and δ¹⁸O Signatures to Evaluate Nitrate Sources and Transformations in Four Inflowing Rivers, North of Taihu Lake

by Da Li, Xia Jiang and Binghui Zheng

Water 2017, 9(5), 345; https://doi.org/10.3390/w9050345 - 17 May 2017

Cited by 13 | Viewed by 5546

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, [...] Read more.

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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Total Nitrogen (TN) input and output throughout the years in Taihu Lake [<a href="#B2-water-09-00345" class="html-bibr">2</a>,<a href="#B4-water-09-00345" class="html-bibr">4</a>]. Full article ">Figure 2
Location of the rivers studied (Zhihugang, Liangxi, Lihe, and Daxigang rivers) and their sampling sites. Full article ">Figure 3
Relationships between NO3−-N and δ15N-NO3− in the Zhihugang, Liangxi, Lihe, and Daxigang rivers. Full article ">Figure 4
Relationships between Cl− and NO3−-N concentrations in the Zhihugang, Liangxi, Lihe, and Daxigang rivers. Full article ">Figure 5
Relationships between δ15N and δ18O of NO3−-N in the Zhihugang, Liangxi, Lihe, and Daxigang rivers. The isotopic compositions of various sources in the diagram were modified after [<a href="#B15-water-09-00345" class="html-bibr">15</a>,<a href="#B16-water-09-00345" class="html-bibr">16</a>,<a href="#B53-water-09-00345" class="html-bibr">53</a>,<a href="#B67-water-09-00345" class="html-bibr">67</a>]. Full article ">Figure 6
Spatial variations of (a) NH4+-N; (b) NO3—N; and (c) TN in the Zhihugang, Liangxi, Lihe and Daxigang rivers. Full article ">

1280 KiB

Open AccessFeature PaperArticle

Impacts of Accumulated Particulate Organic Matter on Oxygen Consumption and Organic Micro-Pollutant Elimination in Bank Filtration and Soil Aquifer Treatment

by Josefine Filter, Martin Jekel and Aki Sebastian Ruhl

Water 2017, 9(5), 349; https://doi.org/10.3390/w9050349 - 16 May 2017

Cited by 24 | Viewed by 6106

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

(This article belongs to the Special Issue Assessment of Water Quality and Treatment Technologies in Potable Water Use)

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(a) Photograph of the profile in the soil aquifer treatment (SAT) basin with a replaced top layer, residuals of the colmation layer, and the underlying filter sand with schematic positions where cores C1, C2, S1, and S2 were withdrawn; (b) schematic illustration and approximate dimensions of the experimental setup. Full article ">Figure 2
Dissolved oxygen concentrations of the influent tap water and of the effluents of the cores. Full article ">Figure 3
Iron and manganese concentrations in the influent tap water and in the effluents of the SAT and BF cores. Full article ">Figure 4
Dissolved organic carbon (DOC) concentrations and ultraviolet light absorption at 254 nm wavelength (UV254) in influent and column effluents. Full article ">Figure 5
Liquid chromatography and continuous organic carbon (LC-OCD) (a) and liquid chromatography with UV detection (LC-UVD) (b) chromatograms of the influent tap water and the core effluents after 76 days of operation. Full article ">Figure 6
Concentrations of sulfamethoxazole, formylaminoantipyrine, diclofenac, gabapentin, benzotriazole, and carbamazepine adjusted in the influent tap water and in the respective effluents. The boxes represent the 25th and the 75th percentiles as well as the median value, with whiskers indicating the lower (10th percentile) and the upper (90th percentile) adjacent values. The empty dots represent the outside values and the red dots the mean values (n ≥ 11). Full article ">

1685 KiB

Open AccessArticle

Estimation of Active Stream Network Length in a Hilly Headwater Catchment Using Recession Flow Analysis

by Wei Li, Ke Zhang, Yuqiao Long and Li Feng

Water 2017, 9(5), 348; https://doi.org/10.3390/w9050348 - 16 May 2017

Cited by 7 | Viewed by 4686

Abstract

Varying active stream network lengths (ASNL) is a common phenomenon, especially in hilly headwater catchment. However, direct observations of ASNL are difficult to perform in mountainous catchments. Regarding the correlation between active stream networks and stream recession flow characteristics, we developed a new [...] Read more.

Varying active stream network lengths (ASNL) is a common phenomenon, especially in hilly headwater catchment. However, direct observations of ASNL are difficult to perform in mountainous catchments. Regarding the correlation between active stream networks and stream recession flow characteristics, we developed a new method to estimate the ASNL, under different wetness conditions, of a catchment by using streamflow recession analysis as defined by Brutsaert and Nieber in 1977. In our study basin, the Sagehen Creek catchment, we found that aquifer depth is related to a dimensionless parameter defined by Brutsaert in 1994 to represent the characteristic slope magnitude for a catchment. The results show that the estimated ASNL ranges between 9.8 and 43.9 km which is consistent with direct observations of dynamic stream length, ranging from 12.4 to 32.5 km in this catchment. We also found that the variation of catchment parameters between different recession events determines the upper boundary characteristic of recession flow plot on a log–log scale. Full article

(This article belongs to the Special Issue Hillslope and Watershed Hydrology)

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Figure 1
Map of the Sagehen Creek catchment. The stream network is extracted using the flow accumulation threshold of 300 with GIS. The dash lines illustrate the order-one streams. Each order-one stream is associated with a hillslope contribution area (gray zone). The continuous black lines illustrate the order-two and order-three streams. Full article ">Figure 2
The calculated breadth (L) based on Equation (8) with different ASNL (B). Full article ">Figure 3
Plot of log(−dQ/dt) vs. log(Q) derived from the observed streamflow for 51 individual recession events selected over a period of 16 years. The straight line with a slope of 1 illustrates the upper boundary of the plot. This upper boundary is discussed in <a href="#sec5dot5-water-09-00348" class="html-sec">Section 5.5</a>. Full article ">Figure 4
Separated plots of dQ/dt vs. Q, based on the range of Qmin on a log scale: (a) log(Qmin) < 3.9, (b) 3.9 ≤ log(Qmin) < 4.1, (c) 4.1 ≤ log(Qmin) < 4.3, (d) 4.3 ≤ log(Qmin) < 4.5, and (e) log(Qmin) ≥ 4.5. Gray dots illustrate the recession curves in each range. Two straight dash lines illustrate the upper and lower envelopes. Two black curves are obtained from the solution Equation (2) with the condition of D equal to 4 m (right curve), and 27 m (left curve). Full article ">Figure 5
B vs. D curves calculated using Equation (6). The five black curves are related to five ranges, respectively. The gray zone illustrates the possible range of active stream network. The dash line in the gray zone illustrates the estimated ASNL according to the assumptions stated in <a href="#sec4-water-09-00348" class="html-sec">Section 4</a>. Full article ">Figure 6
Sensitivity analysis of estimated ASNL as influenced by variations in k and f: (a) the error bars illustrate the influence of k with a range of 0.026–0.39 m/d; (b) the error bars illustrate the influence of f with a range of 0.08–0.15. Full article ">

1014 KiB

Open AccessArticle

Estimation of Instantaneous Peak Flow Using Machine-Learning Models and Empirical Formula in Peninsular Spain

by Patricia Jimeno-Sáez, Javier Senent-Aparicio, Julio Pérez-Sánchez, David Pulido-Velazquez and José María Cecilia

Water 2017, 9(5), 347; https://doi.org/10.3390/w9050347 - 15 May 2017

Cited by 36 | Viewed by 8399

Abstract

The design of hydraulic structures and flood risk management is often based on instantaneous peak flow (IPF). However, available flow time series with high temporal resolution are scarce and of limited length. A correct estimation of the IPF is crucial to reducing the [...] Read more.

The design of hydraulic structures and flood risk management is often based on instantaneous peak flow (IPF). However, available flow time series with high temporal resolution are scarce and of limited length. A correct estimation of the IPF is crucial to reducing the consequences derived from flash floods, especially in Mediterranean countries. In this study, empirical methods to estimate the IPF based on maximum mean daily flow (MMDF), artificial neural networks (ANN), and adaptive neuro-fuzzy inference system (ANFIS) have been compared. These methods have been applied in 14 different streamflow gauge stations covering the diversity of flashiness conditions found in Peninsular Spain. Root-mean-square error (RMSE), and coefficient of determination (R²) have been used as evaluation criteria. The results show that: (1) the Fuller equation and its regionalization is more accurate and has lower error compared with other empirical methods; and (2) ANFIS has demonstrated a superior ability to estimate IPF compared to any empirical formula. Full article

(This article belongs to the Special Issue Forecast of Extreme Events in the Water Cycle—Data, Models and Uncertainties)

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4489 KiB

Open AccessArticle

Summer Season Water Temperature Modeling under the Climate Change: Case Study for Fourchue River, Quebec, Canada

by Jaewon Kwak, André St-Hilaire, Fateh Chebana and Gilho Kim

Water 2017, 9(5), 346; https://doi.org/10.3390/w9050346 - 14 May 2017

Cited by 22 | Viewed by 7598

Abstract

It is accepted that human-induced climate change is unavoidable and it will have effects on physical, chemical, and biological properties of aquatic habitats. This will be especially important for cold water fishes such as trout. The objective of this study is to simulate [...] Read more.

It is accepted that human-induced climate change is unavoidable and it will have effects on physical, chemical, and biological properties of aquatic habitats. This will be especially important for cold water fishes such as trout. The objective of this study is to simulate water temperature for future periods under the climate change situations. Future water temperature in the Fourchue River (St-Alexandre-de-Kamouraska, QC, Canada) were simulated by the CEQUEAU hydrological and water temperature model, using meteorological inputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5) Global Circulation Models (GCMs) with Representative Concentration Pathway (RCP) 2.6, 4.5 and 8.5 climate change scenarios. The result of the study indicated that water temperature in June will increase 0.2–0.7 °C and that in September, median water temperature could decrease by 0.2–1.1 °C. The rise in summer water temperature may be favorable to brook trout (Salvelinus fontinalis) growth, but several days over the Upper Incipient Lethal Temperature (UILT) are also likely to occur. Therefore, flow regulation procedures, including cold water releases from the Morin dam may have to be considered for the Fourchue River. Full article

(This article belongs to the Special Issue Ecological Responses of Lakes to Climate Change)

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5126 KiB

Open AccessArticle

Local Climate Change and the Impacts on Hydrological Processes in an Arid Alpine Catchment in Karakoram

by Jiao Liu, Min Luo, Tie Liu, Anming Bao, Philippe De Maeyer, Xianwei Feng and Xi Chen

Water 2017, 9(5), 344; https://doi.org/10.3390/w9050344 - 12 May 2017

Cited by 17 | Viewed by 5667

Abstract

Climate change and the impacts on hydrological processes in Karakoram region are highly important to the available water resources in downstream oases. In this study, a modified quantile perturbation method (QPM), which was improved by considering the frequency changes in different precipitation intensity [...] Read more.

Climate change and the impacts on hydrological processes in Karakoram region are highly important to the available water resources in downstream oases. In this study, a modified quantile perturbation method (QPM), which was improved by considering the frequency changes in different precipitation intensity ranges, and the Delta method were used to extract signals of change in precipitation and temperature, respectively. Using a historical period (1986–2005) for reference, an average ensemble of 18 available Global Circulation Models (GCMs) indicated that the annual precipitation will increase by 2.9–4.4% under Representative Concentration Pathway 4.5 (RCP4.5) and by 2.8–7.9% in RCP8.5 in different future periods (2020–2039, 2040–2059, 2060–2079 and 2080–2099) due to an increased intensity of extreme precipitation events in winter. Compared with the historical period, the average ensemble also indicated that temperature in future periods will increase by 0.31–0.38 °C/10a under RCP4.5 and by 0.34–0.58 °C/10a under RCP8.5. Through coupling with a well-calibrated MIKE SHE model, the simulations suggested that, under the climate change scenarios, increasing evaporation dissipation will lead to decreased snow storage in the higher altitude mountain region and likewise with regard to available water in the downstream region. Snow storage will vary among elevation bands, e.g., the permanent snowpack area below 5600 m will completely vanish over the period 2060–2079, and snow storage in 5600–6400 m will be reduced dramatically; however, little or no change will occur in the region above 6400 m. Warming could cause stronger spring and early summer stream runoff and reduced late summer flow due to a change in the temporal distribution of snowmelt. Furthermore, both the frequency and intensity of flooding will be enhanced. All the changes in hydrological processes are stronger under RCP8.5 than those under RCP4.5. In Karakoram region, the transformations among different forms of water resources alter the distributions of hydrologic components under future climate scenarios, and more studies are needed on the transient water resources system and the worsening of flood threats in the study area. Full article

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1154 KiB

Open AccessArticle

Cost-Benefit Analysis of the Managed Aquifer Recharge System for Irrigation under Climate Change Conditions in Southern Spain

by Carmen Rupérez-Moreno, Julio Pérez-Sánchez, Javier Senent-Aparicio, Pilar Flores-Asenjo and Carmen Paz-Aparicio

Water 2017, 9(5), 343; https://doi.org/10.3390/w9050343 - 12 May 2017

Cited by 22 | Viewed by 8236

Abstract

Droughts and climate change in regions with profitable irrigated agriculture will impact groundwater resources with associated direct and indirect impacts. In the integrated water resource management (IWRM), managed aquifer recharge (MAR) offers efficient solutions to protect, conserve, and ensure survival of aquifers and [...] Read more.

Droughts and climate change in regions with profitable irrigated agriculture will impact groundwater resources with associated direct and indirect impacts. In the integrated water resource management (IWRM), managed aquifer recharge (MAR) offers efficient solutions to protect, conserve, and ensure survival of aquifers and associated ecosystems, as the Water Framework Directive requires. The purpose of this paper is to analyse the socio-economic feasibility of the MAR system in the overexploited Boquerón aquifer in Hellín (Albacete, Spain) under climate change and varying irrigation demand conditions. To assess, in monetary terms, the profitability of the MAR system, a cost-benefit analysis (CBA) has been carried out. The results for the period 2020–2050 showed that the most favourable situations would be scenarios involving artificial recharge, in which future irrigation demand remains at the present level or falls below 10% of the current irrigation surface, as these scenarios generated an internal rate of return of between 53% and 57%. Additionally, the regeneration of the habitat will take between 5 and 9 years. Thus, the IWRM with artificial recharge will guarantee the sustainability of irrigation of the agricultural lands of Hellín and will achieve water balance even in severe climate change conditions. Full article

(This article belongs to the Special Issue Water Economics and Policy)

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2266 KiB

Open AccessArticle

The Water Footprint of Heavy Oil Extraction in Colombia: A Case Study

by Luis Gabriel Carmona, Kai Whiting and Angeles Carrasco

Water 2017, 9(5), 340; https://doi.org/10.3390/w9050340 - 12 May 2017

Cited by 7 | Viewed by 9166

Abstract

This paper is a Colombian case study that calculates the total water footprint (blue, green, and grey) for heavy crude production (11.5 average API gravity) occurring in three fields, located in the Magdalena watershed. In this case study, the highest direct blue footprint [...] Read more.

This paper is a Colombian case study that calculates the total water footprint (blue, green, and grey) for heavy crude production (11.5 average API gravity) occurring in three fields, located in the Magdalena watershed. In this case study, the highest direct blue footprint registers 0.19 m³/barrel and is heavily influenced by cyclic steam stimulation practices. This value could be reduced if the water coming out of the production well was to be cleaned with highly advanced wastewater treatment technologies. The highest grey water footprint, at 0.06 m³/barrel, is minimal and could be reduced with conventional wastewater treatment technologies and rigorous maintenance procedures. The green water footprint is negligible and cannot be reduced for legal reasons. The indirect blue water footprint is also considerable at 0.19–0.22 m³/barrel and could be reduced if electricity was produced onsite instead of purchased. In addition, the paper identifies methodological flaws in the Colombian National Water Study (2014), which wrongly calculated the direct blue water footprint, leading to a 5 to 32-fold sub-estimation. It also ignored the grey, with important implications for water resource policy and management. To rectify the situation, future National Surveys should follow the procedure published here. Full article

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Figure 1
Watersheds distribution in Colombia. Note: Basins with the letter M belong to the Magdalena catchment. Basins with “MM” indicate that they come under the Middle Magdalena sub-area. Full article ">Figure 2
Product water footprint assessment stages. Full article ">Figure 3
System scope, core processes and direct water footprint flows. CSS: cyclic steam stimulation; SIAR: Produced wastewater treatment plant. Full article ">Figure 4
Water footprint of a produced barrel in m3. SR: secondary recovery; CSS: cyclic steam simulation). Full article ">Figure 5
Blue water footprint evolution 2012–2015. Full article ">Figure 6
Water footprint and water consumption comparisons for onshore conventional crude oil production. Note: TS: this study. SR: secondary recovery. EOR: enhanced oil recovery. Full article ">Figure 7
The contribution of energy and materials to the indirect blue water footprint in CSS 1 vs. the disaggregated carbon emissions of the same field. Full article ">

2528 KiB

Open AccessArticle

Comparison of Spatial Interpolation Schemes for Rainfall Data and Application in Hydrological Modeling

by Tao Chen, Liliang Ren, Fei Yuan, Xiaoli Yang, Shanhu Jiang, Tiantian Tang, Yi Liu, Chongxu Zhao and Liming Zhang

Water 2017, 9(5), 342; https://doi.org/10.3390/w9050342 - 11 May 2017

Cited by 91 | Viewed by 10100

Abstract

The spatial distribution of precipitation is an important aspect of water-related research. The use of different interpolation schemes in the same catchment may cause large differences and deviations from the actual spatial distribution of rainfall. Our study analyzes different methods of spatial rainfall [...] Read more.

The spatial distribution of precipitation is an important aspect of water-related research. The use of different interpolation schemes in the same catchment may cause large differences and deviations from the actual spatial distribution of rainfall. Our study analyzes different methods of spatial rainfall interpolation at annual, daily, and hourly time scales to provide a comprehensive evaluation. An improved regression-based scheme is proposed using principal component regression with residual correction (PCRR) and is compared with inverse distance weighting (IDW) and multiple linear regression (MLR) interpolation methods. In this study, the meso-scale catchment of the Fuhe River in southeastern China was selected as a typical region. Furthermore, a hydrological model HEC-HMS was used to calculate streamflow and to evaluate the impact of rainfall interpolation methods on the results of the hydrological model. Results show that the PCRR method performed better than the other methods tested in the study and can effectively eliminate the interpolation anomalies caused by terrain differences between observation points and surrounding areas. Simulated streamflow showed different characteristics based on the mean, maximum, minimum, and peak flows. The results simulated by PCRR exhibited the lowest streamflow error and highest correlation with measured values at the daily time scale. The application of the PCRR method is found to be promising because it considers multicollinearity among variables. Full article

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Figure 1
Location of the study area and the geographic distribution of hydrometeorological stations. Full article ">Figure 2
Scatterplots of observed versus predicted values for all interpolation methods of annual precipitation. Full article ">Figure 3
Statistical error of rainfall between interpolation methods and meteorological station rainfall measurements in the basin. Full article ">Figure 4
Spatial distribution of all interpolation methods for annual precipitation. Full article ">Figure 5
Differences in monthly rainfall for the Xinxie catchment using different interpolations: (a) PCRR-IDW and (b) PCRR-MLR. Full article ">Figure 6
Modeled and measured runoff during May to June 2010 in Xinxie catchment for principal component regression with residual correction (PCRR), inverse distance weighting (IDW), and MLR rainfall interpolation. Full article ">Figure 7
Modeled and measured runoff of two flood events in Xinxie catchment for PCRR, IDW, and MLR rainfall interpolation. Full article ">

2142 KiB

Open AccessArticle

Mechanism of Nitrogen Removal from Aqueous Solutions Using Natural Scoria

by Tianzi Dong, Yuling Zhang, Xiaosi Su, Zhiyu Chen and Chaoqun Si

Water 2017, 9(5), 341; https://doi.org/10.3390/w9050341 - 11 May 2017

Cited by 5 | Viewed by 4868

Abstract

The efficiencies and mechanisms of nitrogen removal from groundwater by scoria were studied. When NH₄⁺-N concentration was 0.5–10 mg/L, the removal was 96–89%. When NO₂⁻-N concentration was 0.1–5 mg/L, the removal was 93–85%. When NO₃⁻ [...] Read more.

The efficiencies and mechanisms of nitrogen removal from groundwater by scoria were studied. When NH₄⁺-N concentration was 0.5–10 mg/L, the removal was 96–89%. When NO₂⁻-N concentration was 0.1–5 mg/L, the removal was 93–85%. When NO₃⁻-N concentration was 30–150 mg/L, the removal was 85–70%. Additionally, van der Waals forces had a positive impact on the adsorption, which promoted NH₄⁺-N adsorption. Ion exchange and dissolution did not exist. Functional groups of N-H, C-H, and C-N changed after adsorption. Overall, this study indicates that scoria is an ecologically friendly and safe material that can be utilized for groundwater purification to treat nitrogen-contaminated water. Full article

(This article belongs to the Special Issue Groundwater Monitoring and Remediation)

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1641 KiB

Open AccessFeature PaperArticle

Water Bridging Dynamics of Polymerase Chain Reaction in the Gauge Theory Paradigm of Quantum Fields

by L. Montagnier, J. Aïssa, A. Capolupo, T. J. A. Craddock, P. Kurian, C. Lavallee, A. Polcari, P. Romano, A. Tedeschi and G. Vitiello

Water 2017, 9(5), 339; https://doi.org/10.3390/w9050339 - 11 May 2017

Cited by 15 | Viewed by 13401

Abstract

We discuss the role of water bridging the DNA-enzyme interaction by resorting to recent results showing that London dispersion forces between delocalized electrons of base pairs of DNA are responsible for the formation of dipole modes that can be recognized by Taq polymerase. [...] Read more.

We discuss the role of water bridging the DNA-enzyme interaction by resorting to recent results showing that London dispersion forces between delocalized electrons of base pairs of DNA are responsible for the formation of dipole modes that can be recognized by Taq polymerase. We describe the dynamic origin of the high efficiency and precise targeting of Taq activity in PCR. The spatiotemporal distribution of interaction couplings, frequencies, amplitudes, and phase modulations comprise a pattern of fields which constitutes the electromagnetic image of DNA in the surrounding water, which is what the polymerase enzyme actually recognizes in the DNA water environment. The experimental realization of PCR amplification, achieved through replacement of the DNA template by the treatment of pure water with electromagnetic signals recorded from viral and bacterial DNA solutions, is found consistent with the gauge theory paradigm of quantum fields. Full article

(This article belongs to the Special Issue Electrohydrodynamic Liquid Bridges and Electrified Water)

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Mediating wave fields in subatomic and biological physics. (A) In quantum field theory electron-electron interactions are mediated by photons propagating between vertex 1 and vertex 2; (B) Analogously, long-range correlations between DNA and enzymes are mediated by dipole waves in the water matrix. These renderings are schematic, neither drawn to scale nor representative of the actual orientations of water molecules. Adapted from Ref. [<a href="#B1-water-09-00339" class="html-bibr">1</a>]. Full article ">Figure 2
Logarithmic plot of power vs frequency of EMS emitted from water solution of DNA HIV-1 long terminal repeat (LTR 194 base pairs). The decimal dilutions of original concentration of 2 ng/mL HIV-1 emitting EMS are between <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>6</mn> </mrow> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>10</mn> </mrow> </msup> </semantics> </math> [<a href="#B3-water-09-00339" class="html-bibr">3</a>,<a href="#B4-water-09-00339" class="html-bibr">4</a>,<a href="#B5-water-09-00339" class="html-bibr">5</a>,<a href="#B6-water-09-00339" class="html-bibr">6</a>]. The signal analysis is limited to the frequency range between about 100 and 2000 Hz. The signal in the frequencies below ≈40 Hz and above ≈2000 Hz (dotted lines) does not show self-similar behavior. Full article ">Figure 3
Collective dipole oscillations in aromatic amino acid networks of Taq DNA polymerase. Collective normal-mode solutions to networks of aromatic induced dipoles in Taq are within the energy range of the collective dipole modes of DNA bounded by its relevant protein clamps. In the diagonalized form of the coupled harmonic oscillator Hamiltonian, the number operator <math display="inline"> <semantics> <mrow> <msub> <mi>n</mi> <mi>s</mi> </msub> <mo>=</mo> <msubsup> <mi>a</mi> <mrow> <mi>s</mi> </mrow> <mo>†</mo> </msubsup> <msub> <mi>a</mi> <mi>s</mi> </msub> </mrow> </semantics> </math> acts on these states to produce a zero eigenvalue, analogously to Equation (<a href="#FD2-water-09-00339" class="html-disp-formula">2</a>) for DNA. They are identified with zero-point modes of the ground state of the enzyme aromatic network. Data for the collective modes (arranged along the abscissa axis according to increasing energy) are presented in units of eV on the ordinate axis. Adapted from Ref. [<a href="#B1-water-09-00339" class="html-bibr">1</a>]. Full article ">

9969 KiB

Open AccessFeature PaperArticle

Dynamics of Suspended Sediments during a Dry Season and Their Consequences on Metal Transportation in a Coral Reef Lagoon Impacted by Mining Activities, New Caledonia

by Jean-Michel Fernandez, Jean-Dominique Meunier, Sylvain Ouillon, Benjamin Moreton, Pascal Douillet and Olivier Grauby

Water 2017, 9(5), 338; https://doi.org/10.3390/w9050338 - 10 May 2017

Cited by 12 | Viewed by 5880

Abstract

Coral reef lagoons of New Caledonia form the second longest barrier reef in the world. The island of New Caledonia is also one of the main producers of nickel (Ni) worldwide. Therefore, understanding the fate of metals in its lagoon waters generated from [...] Read more.

Coral reef lagoons of New Caledonia form the second longest barrier reef in the world. The island of New Caledonia is also one of the main producers of nickel (Ni) worldwide. Therefore, understanding the fate of metals in its lagoon waters generated from mining production is essential to improving the management of the mining activities and to preserve the ecosystems. In this paper, the vertical fluxes of suspended particulate matter (SPM) and metals were quantified in three bays during a dry season. The vertical particulate flux (on average 37.70 ± 14.60 g·m²·d⁻¹) showed fractions rich in fine particles. In Boulari Bay (moderately impacted by the mining activities), fluxes were mostly influenced by winds and SPM loads. In the highly impacted bay of St Vincent and in the weakly impacted bay of Dumbéa, tide cycles clearly constrained the SPM and metal dynamics. Metals were associated with clay and iron minerals transported by rivers and lagoonal minerals, such as carbonates, and possibly neoformed clay as suggested by an unusually Ni-rich serpentine. Particle aggregation phenomena led to a reduction in the metal concentrations in the SPM, as identified by the decline in the metal distribution constants (K_d). Full article

(This article belongs to the Special Issue Sediment Transport in Coastal Waters)

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Map location of the study area in the west coast of New-Caledonia: Boulari Bay, influenced by a medium-scale mine activities until 1981; Dumbéa Bay, halted mining activity in order to maintain the water supply of Nouméa (the peninsula between Dumbéa Bay and Boulari Bay); St Vincent Bay, affected by intense opencast mining activities. Full article ">Figure 2
Wind and current speeds and directions for Boulari, Dumbéa and St Vincent bays during the study period (21 November to 14 December 2005). Full article ">Figure 3
Median diameter (D50), Junge parameter (s), flux and turbidity for Boulari, Dumbéa and St Vincent bays over the study period (21 November to 14 December 2005), 3 m above the seabed. Full article ">Figure 4
Time variation of the Ca and the 8 metals analysed in SPM trapped during study period from 21 November to 14 December, 2005 in each sampling site: (a) Boulari Bay; (b) Dumbéa Bay and (c) St Vincent Bay. Full article ">Figure 4 Cont.
Time variation of the Ca and the 8 metals analysed in SPM trapped during study period from 21 November to 14 December, 2005 in each sampling site: (a) Boulari Bay; (b) Dumbéa Bay and (c) St Vincent Bay. Full article ">Figure 5
X-ray diffractograms of suspended particulate matter showing the main minerals found in the three study sites (Sm = smectite; T = talc; Se = serpentine; Go = goethite; Ar = aragonite; Q = quartz; Ca = Calcite). Full article ">Figure 6
Images and composition determined by transmitted electron microscopy of some particles collected during the study. The chemical formulae are given in <a href="#water-09-00338-t011" class="html-table">Table 11</a>. Full article ">Figure 7
Particulate Ni flux, distribution constant (Kd) of Ni and dissolved concentration of Ni for Boulari, Dumbéa and St Vincent bays over the study period (21 November to 14 December 2005), 3 m above the seabed. Full article ">

8006 KiB

Open AccessArticle

The Winter Environmental Continuum of Two Watersheds

by Benoit Turcotte and Brian Morse

Water 2017, 9(5), 337; https://doi.org/10.3390/w9050337 - 9 May 2017

Cited by 10 | Viewed by 4970

Abstract

This paper examines the winter ecosystemic behavior of two distinct watersheds. In cold-temperate regions, the hydrological signal and environmental parameters can fluctuate dramatically over short periods of time, causing major impacts to aquatic habitats. This paper presents the results of the 2011–2012 winter [...] Read more.

This paper examines the winter ecosystemic behavior of two distinct watersheds. In cold-temperate regions, the hydrological signal and environmental parameters can fluctuate dramatically over short periods of time, causing major impacts to aquatic habitats. This paper presents the results of the 2011–2012 winter field campaign in streams and rivers near Quebec City, QC, Canada. The objective was to quantify water quantity and quality parameters and their environmental connectivity from headwater creeks above to the larger rivers below over the entire freeze-up, mid-winter and breakup periods with a view toward exploring the watershed continuum. The paper presents how aquatic pulses (water level, discharge, temperature, conductivity, dissolved oxygen and turbidity, measured at seven sites on an hourly basis along channels of different sizes and orders) evolve through the aquatic environment. Ice conditions and the areal ice coverage were also evaluated (on a daily time step along each instrumented channel). Some findings of the investigation revealed that water temperatures remained well above 0 °C during winter in headwater channels, that dissolved oxygen levels during winter were relatively high, but with severe depletions prior to and during breakup in specific settings, that high conductivity spikes occurred during runoff events, that annual turbidity extremes were measured in the presence of ice and that dynamic ice cover breakup events have the potential to generate direct or indirect mortality among aquatic species and to dislodge the largest rocks in the channel. The authors believe that the environmental impact of a number of winter fluvial processes needs to be further investigated, and the relative significance of the winter period in the annual environmental cycle should be given additional attention. Full article

(This article belongs to the Special Issue River and Lake Ice Processes—Impacts of Freshwater Ice on Aquatic Ecosystems in a Changing Globe)

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14925 KiB

Open AccessArticle

Compiling an Inventory of Glacier-Bed Overdeepenings and Potential New Lakes in De-Glaciating Areas of the Peruvian Andes: Approach, First Results, and Perspectives for Adaptation to Climate Change

by Daniel Colonia, Judith Torres, Wilfried Haeberli, Simone Schauwecker, Eliane Braendle, Claudia Giraldez and Alejo Cochachin

Water 2017, 9(5), 336; https://doi.org/10.3390/w9050336 - 9 May 2017

Cited by 50 | Viewed by 9678

Abstract

Global warming causes rapid shrinking of mountain glaciers. New lakes can, thus, form in the future where overdeepenings in the beds of still-existing glaciers are becoming exposed. Such new lakes can be amplifiers of natural hazards to downstream populations, but also constitute tourist [...] Read more.

Global warming causes rapid shrinking of mountain glaciers. New lakes can, thus, form in the future where overdeepenings in the beds of still-existing glaciers are becoming exposed. Such new lakes can be amplifiers of natural hazards to downstream populations, but also constitute tourist attractions, offer new potential for hydropower, and may be of interest for water management. Identification of sites where future lakes will possibly form is, therefore, an essential step to initiate early planning of measures for risk reduction and sustainable use as part of adaptation strategies with respect to impacts from climate change. In order to establish a corresponding knowledge base, a systematic inventory of glacier-bed overdeepenings and possible future lakes was compiled for the still glacierized parts of the Peruvian Andes using the 2003–2010 glacier outlines from the national glacier inventory and the SRTM DEM from the year 2000. The resulting inventory contains 201 sites with overdeepened glacier beds >1 ha (10⁴ m²) where notable future lakes could form, representing a total volume of about 260 million m³. A rough classification was assigned for the most likely formation time of the possible new lakes. Such inventory information sets the stage for analyzing sustainable use and hazard/risk for specific basins or regions. Full article

(This article belongs to the Special Issue Global Warming Impacts on Mountain Glaciers and Communities)

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7080 KiB

Open AccessArticle

Seasonal Variation in Flocculation Potential of River Water: Roles of the Organic Matter Pool

by Byung Joon Lee, Jin Hur and Erik A. Toorman

Water 2017, 9(5), 335; https://doi.org/10.3390/w9050335 - 8 May 2017

Cited by 31 | Viewed by 7914

Abstract

Organic matter in the water environment can enhance either flocculation or stabilization and, thus, controls the fate and transportation of cohesive sediments and causes seasonal variation in the turbidity of river water, determining floc morphology and settling velocity. The aim of this study [...] Read more.

Organic matter in the water environment can enhance either flocculation or stabilization and, thus, controls the fate and transportation of cohesive sediments and causes seasonal variation in the turbidity of river water, determining floc morphology and settling velocity. The aim of this study was to elucidate the way that biological factors change the organic matter composition and enhances either flocculation or stabilization in different seasons. Jar test experiments were performed using a mixture of standard kaolinite and the filtered river water samples collected (bi-)weekly or monthly from April to December 2015 upstream a constructed weir in Nakdong River, to estimate the flocculation potential of the seasonal river water samples. Chlorophyll-a concentration, algae number concentration, and the fluorescence characteristics of organic matter were used to represent the biological factors. Our results revealed that flocculation potential depended not only on the algal population dynamics, but also the origins (or chemical composition) of organic matter in the river water. Extracellular polymeric substances (EPS), as algal organic matter, enhanced flocculation, while humic substances (HS), as terrestrial organic matter, enhanced stabilization, rather than flocculation. Since flocculation potential reached its maximum around the peaks of algal population, algae-produced EPS likely enhanced flocculation by binding sediment particles in the flocs. This observation supports previous findings of seasonal variation in EPS production and EPS-mediated flocculation. However, when HS was transported from the surrounding basin by a heavy rainfall event, cohesive sediments tended to be rather stabilized. Supplementary flocculation potential tests, which were performed with artificial water containing refined EPS and HS, also showed the opposing effects of EPS and HS. Full article

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2284 KiB

Open AccessArticle

Uncertainty of Hydrological Drought Characteristics with Copula Functions and Probability Distributions: A Case Study of Weihe River, China

by Panpan Zhao, Haishen Lü, Guobin Fu, Yonghua Zhu, Jianbin Su and Jianqun Wang

Water 2017, 9(5), 334; https://doi.org/10.3390/w9050334 - 8 May 2017

Cited by 36 | Viewed by 5466

Abstract

This study investigates the sensitivity and uncertainty of hydrological droughts frequencies and severity in the Weihe Basin, China during 1960–2012, by using six commonly used univariate probability distributions and three Archimedean copulas to fit the marginal and joint distributions of drought characteristics. The [...] Read more.

This study investigates the sensitivity and uncertainty of hydrological droughts frequencies and severity in the Weihe Basin, China during 1960–2012, by using six commonly used univariate probability distributions and three Archimedean copulas to fit the marginal and joint distributions of drought characteristics. The Anderson-Darling method is used for testing the goodness-of-fit of the univariate model, and the Akaike information criterion (AIC) is applied to select the best distribution and copula functions. The results demonstrate that there is a very strong correlation between drought duration and drought severity in three stations. The drought return period varies depending on the selected marginal distributions and copula functions and, with an increase of the return period, the differences become larger. In addition, the estimated return periods (both co-occurrence and joint) from the best-fitted copulas are the closet to those from empirical distribution. Therefore, it is critical to select the appropriate marginal distribution and copula function to model the hydrological drought frequency and severity. The results of this study can not only help drought investigation to select a suitable probability distribution and copulas function, but are also useful for regional water resource management. However, a few limitations remain in this study, such as the assumption of stationary of runoff series. Full article

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The study basin map. Full article ">Figure 2
Threshold level method with a variable threshold to define the drought duration and drought severity. Full article ">Figure 3
Drought events in three stations during 1960–2012. Full article ">Figure 4
The number events of different drought (a) durations and (b) severities at three stations. Full article ">Figure 5
Marginal distribution modeling of drought duration and drought severity. (a): LJC drought duration; (b): XY drought duration; (c): HX drought duration; (d): LJC drought severity; (e): XY drought severity; (f): HX drought severity. Full article ">Figure 6
Probability-probability (PP) plot of the joint distributions of duration-severity at three stations. (a): LJC; (b): XY; (c): HX. Full article ">Figure 7
Co-occurrence return period and joint return period of the best-selected copula. (a): LJC drought duration; (b): XY drought duration; (c): HX drought duration; (d): LJC drought severity; (e): XY drought severity; (f): HX drought severity. Full article ">Figure 8
The return period of drought duration and severity based on different marginal distributions at three stations. (a): LJC drought duration; (b): XY drought duration; (c): HX drought duration; (d): LJC drought severity; (e): XY drought severity; (f): HX drought severity. Full article ">Figure 9
Sensitivity of the co-occurrence return period and joint return period of three drought events at Huaxian station and the selection of the univariate distribution and the copulas. (a): co-occurrence return period of drought event 1; (b): co-occurrence return period of drought event 2; (c): co-occurrence return period of drought event 3; (d): joint return period of drought event 1; (e): joint return period of drought event 2; (f): joint return period of drought event 3. Full article ">

7010 KiB

Open AccessArticle

Evaluation of Spatio-Temporal Patterns of Remotely Sensed Evapotranspiration to Infer Information about Hydrological Behaviour in a Data-Scarce Region

by Frank Joseph Wambura, Ottfried Dietrich and Gunnar Lischeid

Water 2017, 9(5), 333; https://doi.org/10.3390/w9050333 - 8 May 2017

Cited by 18 | Viewed by 6917

Abstract

Information about the hydrological behaviour of a river basin prior to setting up, calibrating and validating a distributed hydrological model requires extensive datasets that are hardly available for many parts of the world due to insufficient monitoring networks. In this study, the focus [...] Read more.

Information about the hydrological behaviour of a river basin prior to setting up, calibrating and validating a distributed hydrological model requires extensive datasets that are hardly available for many parts of the world due to insufficient monitoring networks. In this study, the focus was on prevailing spatio-temporal patterns of remotely sensed evapotranspiration (ET) that enabled conclusions to be drawn about the hydrological behaviour and spatial peculiarities of a river basin at rather high spatial resolution. The prevailing spatio-temporal patterns of ET were identified using a principal component analysis of a time series of 644 images of MODIS ET covering the Wami River basin (Tanzania) between the years 2000 and 2013. The time series of the loadings on the principal components were analysed for seasonality and significant long-term trends. The spatial patterns of principal component scores were tested for significant correlation with elevations and slopes, and for differences between different soil texture and land use classes. The results inferred that the temporal and spatial patterns of ET were related to those of preceding rainfalls. At the end of the dry season, high ET was maintained only in areas of shallow groundwater and in cloud forest nature reserves. A region of clear reduction of ET in the long-term was related to massive land use change. The results also confirmed that most soil texture and land use classes differed significantly. Moreover, ET was exceptionally high in natural forests and loam soil, and very low in bushland and sandy-loam soil. Clearly, this approach has shown great potential of publicly available remote sensing data in providing a sound basis for water resources management as well as for distributed hydrological models in data-scarce river basins at lower latitudes. Full article

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