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81.
Manuela?I.?BrunnerEmail author Reinhard?Furrer Anna?E.?Sikorska Daniel?Viviroli Jan?Seibert Anne-Catherine?Favre 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(7):1993-2023
Design flood estimates for a given return period are required in both gauged and ungauged catchments for hydraulic design and risk assessments. Contrary to classical design estimates, synthetic design hydrographs provide not only information on the peak magnitude of events but also on the corresponding hydrograph volumes together with the hydrograph shapes. In this study, we tested different regionalization approaches to transfer parameters of synthetic design hydrographs from gauged to ungauged catchments. These approaches include classical regionalization methods such as linear regression techniques, spatial methods, and methods based on the formation of homogeneous regions. In addition to these classical approaches, we tested nonlinear regression models not commonly used in hydrological regionalization studies, such as random forest, bagging, and boosting. We found that parameters related to the magnitude of the design event can be regionalized well using both linear and nonlinear regression techniques using catchment area, length of the main channel, maximum precipitation intensity, and relief energy as explanatory variables. The hydrograph shape, however, was found to be more difficult to regionalize due to its high variability within a catchment. Such variability might be better represented by looking at flood-type specific synthetic design hydrographs. 相似文献
82.
Manuela Mendes 《Geophysical Prospecting》2000,48(1):49-62
A new interpolation method is presented to estimate the Green's function values, taking into account the migration/inversion accuracy requirements and the trade-off between resolution and computing costs. The fundamental tool used for this technique is the Dix hyperbolic equation (DHE). The procedure, when applied to evaluate the Green's function for a real source position, uses the DHE to derive the root-mean-square velocity, v RMS , from the precomputed traveltimes for the nearest virtual sources, and by linear interpolation generates v RMS for the real source. Then, by applying the DHE again, the required traveltimes and geometrical spreading can be estimated.
The inversion of synthetic data demonstrates that the new interpolation yields excellent results which give a better qualitative and quantitative resolution of the imaging sections, compared with those carried out by conventional linear interpolation. Furthermore, the application to synthetic and real data demonstrates the ability of the technique to interpolate Green's functions from widely spaced virtual sources. Thus the proposed interpolation, besides improving the imaging results, also reduces the overall CPU time and the hard disk space required, hence decreasing the computational effort of the imaging algorithms. 相似文献
The inversion of synthetic data demonstrates that the new interpolation yields excellent results which give a better qualitative and quantitative resolution of the imaging sections, compared with those carried out by conventional linear interpolation. Furthermore, the application to synthetic and real data demonstrates the ability of the technique to interpolate Green's functions from widely spaced virtual sources. Thus the proposed interpolation, besides improving the imaging results, also reduces the overall CPU time and the hard disk space required, hence decreasing the computational effort of the imaging algorithms. 相似文献
83.
84.
Remediation of contaminated aquifers demands a reliable characterization of hydraulic connectivity patterns. Hydraulic diffusivity is possibly the best indicator of connectivity. It can be derived using the tidal response method (TRM), which is based on fitting observations to a closed-form solution. Unfortunately, the conventional TRM assumes homogeneity. The objective of this study was to overcome this limitation and use tidal response to identify preferential flowpaths. Additionally, the procedure requires joint inversion with hydraulic test data. These provide further information on connectivity and are needed to resolve diffusivity into transmissivity and storage coefficient. Spatial variability is characterized using the regularized pilot points method. Actual application may be complicated by the need to filter tidal effects from the response to pumping and by the need to deal with different types of data, which we have addressed using maximum likelihood methods. Application to a contaminated artificial coastal fill leads to flowpaths that are consistent with the materials used during construction and to solute transport predictions that compare well with observations. We conclude that tidal response can be used to identify connectivity patterns. As such, it should be useful when designing measures to control sea water intrusion. 相似文献
85.
The cenozoic aquifer system of the Lower Tagus Basin: a description of the hydrogeological situation in the Almada region (Portugal) 总被引:1,自引:0,他引:1
Maria Manuela Malhado Simões Ribeiro 《Hydrogeology Journal》2009,17(4):999-1009
A conceptual hydrogeological model of the Mio-Pleistocene deposits in the Almada region, located in the Cenozoic aquifer system of the Lower Tagus Basin (Portugal), has been developed. Though numerous studies have been conducted on its geological features, there have not been enough hydrogeological investigations to define the origin, flow path and the groundwater quality and to understand the coexistence of overlapped interacting aquifers. Therefore, a study is presented here on the occurrences and features of groundwater resources in the Almada region based on an inventory in the field (wells, springs and boreholes), physical and chemical analyses, geologic setting, and tectonic and geomorphologic observations. This aquifer system has long been a source of concern because of the high level of extraction over the last few decades, as well as the progressive degradation of the water quality. Available groundwater resources have been affected by intensive agricultural and industrial activity, as a consequence of incorrect or non-existent hydrogeological knowledge. 相似文献
86.
Rubidium and strontium partitioning experiments between haplogranitic melts and aqueous fluids (water or 1.16-3.56 m (NaCl + KCl) ± HCl) were conducted at 750-950 °C and 0.2-1.4 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. In addition, we studied if the applied technique (rapid and slow quench, and in-situ determination of trace element concentration in the fluid) has a bearing on the obtained data. There is good agreement of the data from different techniques for chloridic solutions, whereas back reactions between fluid and melt upon cooling have a significant effect on results from the experiments with water.The Rb fluid-melt partition coefficient shows no recognizable dependence on melt composition and temperature.For chloridic solutions, it is ∼0.4, independent of pressure. In experiments with water, it is one to two orders of magnitude lower and increases with pressure. The strontium fluid-melt partition coefficient does not depend on temperature. It increases slightly with pressure in Cl free experiments. In chloridic fluids, there is a sharp increase in the Sr partition coefficient with the alumina saturation index (ASI) from 0.003 at an ASI of 0.8 to a maximum of 0.3 at an ASI of 1.05. At higher ASI, it decreases slightly to 0.2 at an ASI of 1.6. It is one to two orders of magnitude higher in chloridic fluids compared to those found in H2O experiments. The Rb/Sr ratio in non-chloridic solutions in equilibrium with metaluminous melts increases with pressure, whereas the Rb/Sr ratio in chloridic fluids is independent of pressure and decreases with fluid salinity.The obtained fluid-melt partition coefficients are in good agreement with data from natural cogenetic fluid and melt inclusions. Numerical modeling shows that although the Rb/Sr ratio in the residual melt is particularly sensitive to the degree of fractional crystallization, exsolution of a fluid phase, and associated fluid-melt partitioning is not a significant factor controlling Rb and Sr concentrations in the residual melt during crystallization of most granitoids. 相似文献
87.
88.
89.
Daniela Thaller Rolf Dach Manuela Seitz Gerhard Beutler Maria Mareyen Bernd Richter 《Journal of Geodesy》2011,85(5):257-272
Satellite Laser Ranging (SLR) observations to Global Navigation Satellite System (GNSS) satellites may be used for several
purposes. On one hand, the range measurement may be used as an independent validation for satellite orbits derived solely
from GNSS microwave observations. On the other hand, both observation types may be analyzed together to generate a combined
orbit. The latter procedure implies that one common set of orbit parameters is estimated from GNSS and SLR data. We performed
such a combined processing of GNSS and SLR using the data of the year 2008. During this period, two GPS and four GLONASS satellites
could be used as satellite co-locations. We focus on the general procedure for this type of combined processing and the impact
on the terrestrial reference frame (including scale and geocenter), the GNSS satellite antenna offsets (SAO) and the SLR range
biases. We show that the combination using only satellite co-locations as connection between GNSS and SLR is possible and
allows the estimation of SLR station coordinates at the level of 1–2 cm. The SLR observations to GNSS satellites provide the
scale allowing the estimation of GNSS SAO without relying on the scale of any a priori terrestrial reference frame. We show
that the necessity to estimate SLR range biases does not prohibit the estimation of GNSS SAO. A good distribution of SLR observations
allows a common estimation of the two parameter types. The estimated corrections for the GNSS SAO are 119 mm and −13 mm on
average for the GPS and GLONASS satellites, respectively. The resulting SLR range biases suggest that it might be sufficient
to estimate one parameter per station representing a range bias common to all GNSS satellites. The estimated biases are in
the range of a few centimeters up to 5 cm. Scale differences of 0.9 ppb are seen between GNSS and SLR. 相似文献
90.
The aim of this paper is to test the ability of neural network approaches to hindcast the spring standardized precipitation index on a 6‐month time scale (SPI6) in Portugal, based on winter large‐scale climatic indices. For this purpose, the linkage of the spring SPI time series with the winter North Atlantic Oscillation (NAO) and the sea surface temperature (SST) was investigated by means of maps of the correlation coefficient for the period from October 1910 to September 2004. The results indicate that the winter NAO is a good predictor for the SPI6 of the spring (SPI6 finishing in April, May and June, SPI6April, SPI6May and SPI6June, respectively) for the northern, central and southern regions of Portugal. The winter SST1 (area of the Mediterranean Sea) must only be considered for the northern region, and the winter SST3 (area of the North Atlantic between Iberia and North America) only for the southern region. Spatial maps of predictive SPI6 for April, May and June were created and validated. The neural models explained more than 81% of the total variance for the SPI6April and SPI6May and more than 64% of the total variance for the SPI6June. Probability maps were also developed considering the values predicted by the neural methods for the spring months and all drought categories (moderate, severe and extreme). These maps indicating the probability of droughts can provide valuable support for the integrated planning and management of water resources throughout Portugal. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献