Interbasin ground water movement of 200 to 240 L/sec occurs as underflow beneath a mountainous surface water divide separating the topographically higher Salar de Michincha from the topographically lower Salar de Coposa internally drained basins in the Altiplano of northern Chile. Salt-encrusted flats (salars) and saline lakes occur on the lowest parts of the basin floors and comprise the principal evaporative discharge areas for the basins. Because a surface water divide separates the basins, surface water drainage boundaries do not coincide with ground water drainage boundaries. In the region, interbasin ground water movement is usually not recognized, but occurs for selected basins, and at places is an important component of ground water budgets. With increasing development of water for mining industry and potential exportation of ground water from the Altiplano for use at coastal cities, demonstration and quantification of interbasin movement is important for assessment of sustainable ground water development in a region of extreme aridity. Recognition and quantification of interbasin ground water underflow will assist in management of ground water resources in the arid Chilean Altiplano environment. 相似文献
This paper presents two examples of application of Synthetic Aperture Radar (SAR) interferometry (InSAR) to typical geomorphological problems. The principles of InSAR are introduced, taking care to clarify the limits and the potential of this technique for geomorphological studies. The application of InSAR to the quantification of landform attributes such as the slope and to the estimation of landform variations is investigated. Two case studies are presented. A first case study focuses on the problem of measuring landform attributes by interferometric SAR data. The interferometric result is compared with the corresponding one obtained by a Digital Elevation Model (DEM). In the second case study, the use of InSAR for the estimation of landform variations caused by a landslide is detailed. 相似文献
The morphometry of 432 glacial cirques in the Maritime Alps (Western French‐Italian Alps), studied over several years of fieldwork, was analysed with the use of a geographical information system. Some of the parameters automatically evaluated from digital elevation models required an objective and relatively new definition. In particular, cirque length was measured along a line that, from the threshold midpoint, splits the cirque into two equivalent surfaces; cirque width was automatically drawn as the longest line inscribed in the cirque and perpendicular to the length line. Significant correlations were found among the different factors and parameters analysed. In particular, cirque shape analysis showed that cirques develop allometrically in the three dimensions, i.e. more in length and width than in altitudinal range. Nevertheless cirques of the Maritime Alps have a regular, almost circular shape (mean L/W value = 1.07). The correlations among length, width and area are all very high (r2= 0.8–0.9). In terms of size, cirques show a wide range in area from 0.06 to 5.2 km2 with a mean value of 0.4 km2. The largest cirques are found on SSW‐facing slopes and at high elevations. Small cirques can be found at all altitudes but all those at high elevation are part of compound cirques at the main head valleys. Most cirques (37%) are characterized by a northern aspect; NE and SW are also frequent directions. 相似文献
The study zone is located in the city of Padova (the Veneto region, NE Italy). The industrial activities present in this area
since 1950 have produced very high concentrations of Pb, Zn, Cu, Pcb and oils until a depth of 7 m. The unsaturated and the
saturated zones are both polluted. Because of the abundance of Pb values it was decided to analyze the lead distribution in
the studied zone. In many studies of the polluted sites, the geometry of the investigated volume is highly anisotropic. Generally
we have an extension of some hectares in the horizontal plane and of a few meters in depth. It is likely that different horizontal
spatial continuity structures in pollution distribution are found at different depths both for the layered nature of the medium
and for the transition between unsaturated and saturated conditions. In such conditions the decision to divide a 3D problem
into 1D and 2D problems can be useful. Initially the studied volume was divided into seven layers up to 5 m in depth; the
study was then approached in two phases. First, the Pb values in the vertical direction were analyzed, considering a derive
along z, and estimating the values using the Kriging with Trend (KT) method. Thus it was possible to increase the data in the z direction, especially in the deeper layers. Second, 500 realizations of the Pb distribution for each of the seven layers
were simulated using the simulated annealing procedure. Finally, results were presented and discussed for each layer in terms
of median and probability maps. 相似文献
Application of recent advances in numerical weather prediction (NWP) has the potential of allowing delivery of flood warning to extend well beyond the typical lead times of operational flood warning at the river basin scale. A prototype system, a European Flood Forecasting System (EFFS) developed to deliver such pre-warnings, aiming at providing a pre-warning at lead times of between 5 and 10 days is described. Considerable uncertainty in the weather forecast at these lead times, however, means that resulting forecasts must be treated probabilistically, and although probabilistic forecasts may be easy to disseminate, these are difficult to understand. This paper explores the structure of operational flood warning, and shows that integration in the flood warning process is required if the pre-warning is to fulfil its potential. A simple method of summarising the information in the pre-warning is presented, and the system in hindcast mode is shown to give clear indication of an upcoming major event in the Rhine basin up to 10 days before the actual event. Finally recommendations on the use of data assimilation to embed the EFFS system within an operational environment are given. 相似文献
Meteoric smoke particles (MSPs) form through the vaporization of meteoroids and the subsequent re-condensation of metallic species in the mesosphere. Recently, iridium and platinum enrichments have been identified in Greenland ice layers and attributed to the fallout of MSPs supplying polar latitudes with cosmic matter during the Holocene. However, the MSP fallout to Antarctica during the Earth's climatic history remains essentially unknown.
We have determined iridium and platinum in deep Antarctic ice from Dome C and Vostok dated back to 240 kyrs BP. We find high super-chondritic fluxes during warm periods and low meteoric accretion during glacial times, a pattern that is opposite to any known climatic variation in dust fallout to polar regions. The proposed explanation of this accretion regime is a weaker polar vortex during warm periods, allowing peripheral air masses enriched in volcanic iridium and platinum to penetrate inland to Antarctica. The MSP signal emerges only during cold phases and is four times lower than in the Greenland ice cap where more snow accumulates. This suggests that wet deposition is an important route of cosmic material to the Earth's surface. 相似文献
In past years, seismic response of asymmetric structures has been frequently analysed by means of single-storey models, because
of their simplicity and low computational cost. However, it is widely believed that use of more realistic multi-storey models
is needed in order to investigate effects of some system characteristics (such as overstrength, higher modes of vibration,
etc.) that make behaviour of multi-storey schemes different from that of single-storey systems. This paper examines effects
of the overstrength in element cross-sections on the seismic behaviour of multi-storey asymmetric buildings. It is shown that
in actual buildings this characteristic, which is sometimes very variable both in plan and along the height of the building,
may lead to distributions of ductility demands different from those expected according to the results from single-storey models.
Consequently, torsional provisions, which aim at reducing ductility demands of single-storey asymmetric systems to those of
the corresponding torsionally balanced systems, should be re-checked in light of the behaviour of realistic multi-storey buildings. 相似文献
An archaeometric study of the stone materials employed in the Late Baroque historical monuments of the ancient city centre of Catania was carried out. Lithological maps of a selection of monuments, transferred to a digital format, revealed that the stone materials are both magmatic and sedimentary rocks, the colours of which are matched in a peculiar type of bichromy. Particular attention focused on sedimentary rocks, which consist of various types of limestone quarried near the city of Syracuse (Hyblean Plateau, south-eastern Sicily). Carbonate rocks were characterised in terms of mineralogy, petrography and geochemistry, by studying rock samples from both monuments and historical extraction sites. Results showed that, although only one name was historically attributed to the above lithotypes (i.e. “Pietra di Siracusa‘’), they were quarried from many locations and, as they belong to various geological formations, they therefore exhibit great variety. In order to examine the durability of Hyblean limestones employed in works of cultural heritage interest, salt crystallisation tests were carried out according to standard procedure norms (UNI EN 12370 (1999) Determination of resistance to crystallisation of salts, 6p). Results are consistent with the forms of deterioration observed in the monuments, and highlight the close relationship between textural characteristics and damage. Our purpose is to provide a basic tool, which may be useful both for conserving monuments of cultural heritage and for their restoration. 相似文献