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961.
Giorgio Boni Luca Ferraris Francesca Giannoni Giorgio Roth Roberto Rudari 《Advances in water resources》2007
A methodology is proposed for the inference, at the regional and local scales, of flood magnitude and associated probability. Once properly set-up, this methodology is able to provide flood frequencies distributions at gauged and un-gauged river sections pertaining to the same homogeneous region, using information extracted from rainfall observations. A proper flood frequency distribution can be therefore predicted even in un-gauged watersheds, for which no discharge time series is available. 相似文献
962.
The most conspicuous waterbodies in the Pampa region of Argentina are the so-called “lagunas”. A typical Pampean laguna may be described as a relatively large (100+ha), permanent, shallow lake. Here, we report the dynamics of laguna Chascomús, sampled weekly, from April 2001 to June 2003. During the period, the lakes experienced three consecutive floods waves that affected the concentration of major ions and the optical signature of the dissolved organic matter. Despite these hydrological alterations, laguna Chascomús was permanently limited by light. Transparency was to a great extent controlled by the incident photosynthetic available radiation irradiance. We hypothesize that wind contributes to the permanent mixing of the lake, as well as to lessen the sedimentation losses of photoautotrophs. 相似文献
963.
The interaction between surface and subsurface water has a crucial influence on the biochemistry of stream environments. Even though the river discharge and the flow conditions can seldom be considered to be steady, the influence of this unsteadiness on the hyporheic exchange has often been neglected. In this work, a model for the study of hyporheic exchange during unsteady conditions has been developed. The model provides a sound analytical framework for the analysis of the effects of a varying stream discharge on the exchange between a stream and the hyporheic zone. The effects of the unsteadiness on the water exchange flux, the residence time of the solutes in the bed, and the stored mass are quantified. A synthetic example shows the substantial influence of a flood on the hyporheic exchange, and that the application of a steady model can lead to an underestimation of the exchanged mass, even after the flood has ended. 相似文献
964.
Roberto Viotti Cesare D. La Padula Domenico Nanni Agostino Vignato 《Astrophysics and Space Science》2001,276(1):81-88
We present the basic concepts of the two-mirror, three-reflection optical system (2MTRT), and discuss the important benefits of such a system for space projects: wide ( 2°) correctedand unvignetted FOV, without the use of refractive optics for thefield correction, planarity of the focal surface for an optimizedinstallation of wide area detectors, easy telescope adjustement, small volume and little mass.We also report the results of optical tests made with a 30 cm prototype,equipped with a 2k × 2k CCD camera, and give examples of scientific programmes which can be performed from space and in hostile terrestrial sites such as the Antarctic Plateau. 相似文献
965.
An assessment of marine pollution due to metals was made in the Caspian Sea based on coastal sediment collected in Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan. Despite the high carbonate content, the distribution of most metals was largely controlled by terrigenous inputs. Several metals (As, Cr, Ni) exhibited concentrations that exceed sediment quality guidelines. Such metals have a high natural background but anthropogenic activities, notably mining, may further enhance concentrations. This would explain hot spots for Cu and Zn in Azerbaijan and Iran, and Cr at the mouth of the Ural River in Kazakhstan. Contamination by Hg was observed to the south of Baku Bay, Azerbaijan. Some anomalously high concentrations of Ba in the central Caspian are probably from offshore drilling operations, but the elevated U concentrations (up to 11.1 microg g(-1)) may be natural in origin. Several metals (Ag, Cd, Pb) have relatively low levels that pose no environmental concerns. 相似文献
966.
Federico Manzini Raoul Behrend Lorenzo Comolli Virginio Oldani Cristiano B. Cosmovici Roberto Crippa Cesare Guaita Gottfried Schwarz Josep Coloma 《Astrophysics and Space Science》2012,337(2):531-542
Extensive observations of comet C/2004 Q2 (Machholz) were carried out between August 2004 and May 2005. The images obtained
were used to investigate the comet’s inner coma features at resolutions between 350 and 1500 km/pixel. 相似文献
967.
Reyes-Carmona Cristina Galve Jorge Pedro Moreno-Sánchez Marcos Riquelme Adrián Ruano Patricia Millares Agustín Teixidó Teresa Sarro Roberto Pérez-Peña José Vicente Barra Anna Ezquerro Pablo López-Vinielles Juan Béjar-Pizarro Marta Azañón José Miguel Monserrat Oriol Mateos Rosa María 《Landslides》2021,18(12):3781-3798
Landslides - When an active landslide is first identified in an artificial reservoir, a comprehensive study has to be quickly conducted to analyse the possible hazard that it may represent to such... 相似文献
968.
Acta Geotechnica - A soil water characteristic curve (SWCC) model named as discrete-continuous multimodal van Genuchten model with a convenient parameter calibration method is developed to describe... 相似文献
969.
Van de Vyver Evelien Pinseel Eveline Verleyen Elie Vanormelingen Pieter Van Wichelen Jeroen de Jong Rixt Urrutia Roberto Vyverman Wim 《Journal of Paleolimnology》2022,68(3):279-296
Journal of Paleolimnology - Paleolimnological records from temperate South-Central Chilean lakes revealed a recent and marked increase in the relative abundances of the key-planktonic diatom... 相似文献
970.
Mauro Valdés-Barrón Roberto Bonifaz-Alfonzo David Riveros-Rosas Victor Velasco-Herreora Hector Estévez-Pérez Juan Carlos Peláez-Chávez 《Geofísica Internacional》2013,52(1):31-42
The measurement of solar B band Ultraviolet radiation (UVB) should be considered a priority in Mexico due to implications on public health throughout the country (total population, 108 million), but this is not carried out at present. Installed sensors cover only 0.12% of the country. However, there are alternative methods for estimating UVB radiation to overcome the lack of surface data. The most successful of these are based on the use of satellites for environmental monitoring. In the present work, UVB maps are constructed for the entire country using a single, daily satellite measurement of UVB at solar noon from 1978-2003. Satellite-derived values are compared with the ground measurements by a surface station located in Mexico City in order to validate the former. Wavelet spectrum analysis is employed to this end. A close correlation is observed between the two sets of data. Moreover, there is qualitative correspondence between the spatial distribution of the satellite-derived data and the surface topography. The difference resulting throughout the period mentioned is <2% of the average annual cumulative energy. 相似文献