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  • Articles  (1,547)
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  • Articles  (1,547)
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  • 1
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    Reconstructing Monthly ECV Global Soil Moisture with an Improved Spatial Resolution (2018)
    Springer
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    Publication Date: 2018-03-14
    Description: Remote sensing techniques have provided global covered soil moisture at high temporal resolution, however, the coarse spatial resolution and the data gaps have greatly reduced their potential values in large numbers of practical and regional applications. This study proposed a two-steps reconstruction approach for reconstructing satellite-based soil moisture products (ECV) at an improved spatial resolution. The reconstruction model implemented the Random Forests (RF) regression algorithm to simulate the relationships between soil moisture and environmental variables, and takes advantages of the high spatial resolution of optical remote sensing products: the data gaps of ECV soil moisture products were firstly filled by the estimation model trained using available pixels of the ECV products and corresponding environmental variables; then a spatial downscaling was carried out to the gap-filled ECV products to obtain the reconstructed soil moisture with fine spatial resolution (0.05°). As a result, the reconstructed soil moisture well fill the data gaps of the original ECV products and nicely reproduced the original soil moisture values (R 2  〉 0.98). The spatial resolution and variation details of the soil moisture products were also improved significantly. Validation results indicated that the reconstructed soil moisture showed comparable good performance (average R 2  = 0.66) as the original ECV products (average R 2  = 0.65) and nicely reflect the temporal behavior of ground-based measurements. As a result, the reconstructed soil moisture well filled the data gaps and greatly improved the spatial resolution of ECV products.
    Print ISSN: 0920-4741
    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 2
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    Trade in Virtual Water: Do Property Rights Matter? (2018)
    Springer
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    Publication Date: 2018-03-14
    Description: This paper examines the determinants of virtual water trade – embodied in agricultural products – and tests the relationship between property rights and the export of water-intensive products. Using two different measures of property rights protection, I show that countries with weaker property rights have an apparent comparative advantage in the export of water-intensive products. After controlling for economic size, natural resource endowments and bilateral trade determinants, the trade flow of virtual water is negatively and significantly correlated with the property rights index of the exporting country. The results are robust across different estimation methods.
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    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 3
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    Effects of Global Warming on Precipitation Extremes: Dependence on Storm Characteristics (2018)
    Springer
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    Publication Date: 2018-03-14
    Description: This study investigates the relationship between historically observed changes in extreme precipitation magnitudes and temperature (P ex -T relationship) at multiple locations in Canada. The focus is on understanding the behavior of these relationships with regards to key storm characteristics such as its duration, season of occurrence, and location. To do so, three locations are chosen such that they have large amounts of moisture available near them whereas four locations are chosen such that they are located in the land-locked regions of Canada and subsequently have no nearby moisture source available on them. To investigate the effect of different storm durations on P ex -T relationship, storms of durations: 5, 10, 15, 30 min, 1, 2, 6, 12, 24 h are considered. Finally, P ex -T relationship is analyzed separately for summer and winter seasons to quantify the influence of seasons. Results indicate strong influences of storm duration, season of occurrence, and location on observed precipitation scaling rates. Drastic intensification of precipitation extremes with temperature is obtained for shorter duration precipitation events than for longer duration precipitation events, in summers than in the winters. Furthermore, in summertime, increases in the intensity of convection driven precipitation extremes is found highest at locations away from large waterbodies. On the other hand, in wintertime most drastic increases in extreme precipitation are obtained at locations near large waterbodies. These findings contribute towards increasing the current understanding of precipitation extremes in the context of rapidly increasing global temperatures.
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    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 4
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    Regionalizing Flood Magnitudes using Landscape Structural Patterns of Catchments (2018)
    Springer
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    Publication Date: 2018-03-14
    Description: Emerging as an important issue in the disciplines of landscape ecology and landscape hydrology which inspired it, defining the concept of landscape metrics in a hydrological context has become a challenge to both landscape planners and engineers. Accordingly, the present study addresses the relationships existing between flooding phenomena and landscape metrics (shape index, fractal dimension index, perimeter-area ratio, related circumscribing circle, and contiguity index) of land use/land cover, hydrological soil groups and geological permeability classes. A regionalization approach was adopted employing 39 select catchments (33—4800 km 2 in area, 0.47—21 m 3  s −1 in mean discharge), located within the southern basin of the Caspian Sea. These catchments were predominantly covered by forest (57.4%), while rangeland, farmland and urban areas accounted for 25.9%, 11.7%, and 1.6%, respectively. Class-level landscape structural metrics of land use/land cover, hydrological soil groups and geological permeability classes have then been served as inputs to stepwise multiple linear regression analysis in an attempt to explain the flood magnitudes. The regression models (0.69 ≤ r 2  ≤ 0.84) suggested that the catchments’ flood magnitude could explicitly be predicted using average measure of the shape and related circumscribing circle indices for the land use/land cover classes and those of hydrologic soil groups and geological permeability classes of the catchments. This indicated that regularity (vs. irregularity) of the landscape, pedoscape, and lithoscape, as represented by the shape index as well as the circumscribing circle index (for elongation and convolution), explained 69–84% of the variation in the flood magnitudes in the catchment.
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    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 5
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    The Influence of the Construction Technology in Time-Cost Relationships of Sewerage Projects (2018)
    Springer
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    Publication Date: 2018-03-14
    Description: Time-cost models have been developed in various contexts to assist in forecasting the duration of different types of projects. The present research explores the influence of the construction technology on the time-cost relationship. For that purpose, the data from 21 sewerage projects using trenchless technology and from 49 sewerage projects using the traditional open-cut method was analyzed. The 70 sewerage projects analyzed were completed in Chicago, U.S., between 1994 and 2002. The influence of the construction technology in the time-cost relationship was found to be statistically significant and time-relationships were determined for sewerage projects using trenchless technology and the traditional open-cut method. Furthermore, along with the Bromilow type models an alternative approach was tested using the time normalized by the project cost as dependent variable, allowing additional insight into the time performance of the open-cut and lining technology used (cured in place).
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    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 6
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    Reservoir Optimization for Energy Production Using a New Evolutionary Algorithm Based on Multi-Criteria Decision-Making Models (2018)
    Springer
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    Publication Date: 2018-03-14
    Description: The study applies kidney algorithm for the optimization of reservoir operation for hydropower generation. The objective function defined for optimization is to minimize the hydroelectric power deficiency. Results of kidney algorithm are compared with those of bat algorithm (BA), water cycle algorithm (WCA), biogeography-based optimization algorithm (BBO), genetic algorithm (GA), particle swarm optimization algorithm (PSOA), and scatter matters search algorithm (SMSA). All algorithms are evaluated by Complex proportional assessment (COPRAS), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), modified TOPSIS, and Weighted Aggregated Sum Product Assessment (WASPAS), as well as Borda count social choice theory. Then, vulnerability, time and volumetric reliability, as well as resiliency indices are used for comparison and multi-criteria decision-making indicators for selecting the best algorithm. It is found that no algorithm is ranked uniformly the best. Results indicate that kidney and particle swarm algorithms are ranked higher than other algorithms by most indices. Results of 10 random implementations of the objective function indicate that KA has a lower coefficient of variation and is computationally moe efficient. Further, most of the multi-criteria decision making models allocate the first rank to KA.
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    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 7
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    Balancing Water Demand Needs with Protection of River Water Quality by Minimising Stream Residence Time: an Example from the Thames, UK (2018)
    Springer
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    Publication Date: 2018-03-12
    Description: Freshwater resources in the River Thames basin in southern UK are faced with combined pressures of future population growth and climate change. River basin managers are seeking increasingly innovative methods to meet water demand whilst at the same time maintaining ecological status. Using a river network hydrochemical model modified to account for possible future climate and population, the paper assesses the impact on downstream water quality of changing the location of a major point of abstraction serving the city of Oxford. The rationale behind the hypothetical change, although entailing an increase in energy costs and capital expenditure, was that flows would be maintained along a sensitive stretch of river. Model results at a location a further 23 km downstream suggested that better water quality would arise from this change. The predicted improvements included a decrease in the annual frequency of low DO concentrations (〈6 mg L −1 ) from 8–9 days to 2–3 days and a decrease in 90th percentile (summer) temperatures of 0.6 °C. It is believed these improvements would primarily be attributable to shortening of river residence time which curtails accelerated phytoplankton growth. The overall conclusion, of relevance both for the Thames basin and elsewhere, is that water quality in a river network can be surprisingly sensitive to the location of abstractions. Changing the location of abstractions should be considered as part of a suite of measures available to river basin managers when making plans to meet future water demand.
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    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 8
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    Alternative Trend Analysis: Half Time Series Methodology (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: This paper attempts to determine and visualize the trends by considering the value via Şen’s innovative trend analysis methodology, which has been suggested instead of the well-known approaches called Mann-Kendall (MK), Spearman’s rho (SR), Sen’s slope, and linear regression methodologies. Another attempt is to show that an additional trend approach by using half time series methodology (HTSM) including MK’s Z value, and to compare it with the innovative method. Although, Şen’s method is practical, easy and clear representation of data variation, but some information is not evident on time series. This study comprises 66-year rain gage records in Adana, İzmir, and Rize stations located in different regions of Turkey. The comparison results indicated different trend conditions for these stations. Based on this information, representative figures are obtained according to Şen’s and HTSM for the precipitation records. According to Şen’s method, Adana and Rize stations’ measurements have no trend component but İzmir data have monotonically increasing trend. HTSM results reveal some additional information on Şen’s half time series approach. Adana station time series halves include opposite trends (increasing-decreasing) detected by HTSM in spite of no trend. Different extreme cases are encountered in İzmir and Rize stations through HTSM. As a result, if the proposed method is combined with Şen’s method, better trend analysis results can be obtained for detailed interpretations.
    Print ISSN: 0920-4741
    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 9
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    Data Analysis in Nonstationary State (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: Climate change impact must be taken into account in any water resources planning management studies, because it does not allow future occurrences to be repeated as a replicate of the past. The stationarity is no longer valid, because the climate change plays significant role on ascending or descending trend components in any hydro-meteorological events such as temperature, precipitation, evaporation, runoff and discharge. The identification of trends can be represented by well-known methodologies, such as the Mann-Kendall and sequential Mann-Kendall. These methodologies require restrictive assumptions such as data length, serial independence and Gaussian (normal) probability distribution function (PDF). On the other hand, Innovative trend analysis (ITA) method proposed by Şen is helpful to identify even visually with direct interpretations without restrictive assumptions. The PDF or cumulative distribution function (CDF) is effective tool for risk level determination but it cannot tell anything about the trend in a given hydro-meteorological data. The PDF (CDF) does not yield any clue about the trend possibility, and hence, it’s alone use in any water resources structure design may lead to erroneous planning studies. In this study, nonstationary nature of a given monthly hydro-meteorological data is examined by trend determination procedures. For the application, monthly averages of maximum daily temperatures are used on Oxford station, UK. It is observed that the temperature values of each month have a positive trend and the nonstationary empirical cumulative frequency curves on first half group match better all data group than the stationary state.
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    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 10
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    Swiss Rainfall Mass Curves and their Influence on Extreme Flood Simulation (2018)
    Springer
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    Publication Date: 2018-03-07
    Description: Extreme flood estimates for dam safety are routinely obtained from hydrologic simulations driven by selected design storms. The temporal structure of such design storms can be obtained from Rainfall Mass Curves (RMCs), which are adimensionalized curves of the cumulative precipitation depth as a function of event duration. This paper assesses for the first time the spatialand temporal variability of observed RMCs for Switzerland, an Alpine region with complex topography. The relevance of the detected RMC variability for extreme flood estimation is illustrated based on an application to a high elevation catchment, the Mattmark dam catchment in the Swiss Alps. The obtained results underline that quantile RCMs represent a simple yet powerful tool to construct design storms for dam safety verification and that regional, seasonal and event-duration effects on RMCs are small enough to justify the use of a unique set of Swiss-wide quantile RMCs. The presented analysis could be refined in the future by explicitly accounting for orographic, convective or frontal precipitation events.
    Print ISSN: 0920-4741
    Electronic ISSN: 1573-1650
    Topics: Architecture, Civil Engineering, Surveying , Geography
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