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1.
Shallow groundwater in the northern Negev desert of Israel flows preferentially through a complex system of discontinuities. These discontinuities intersect what would otherwise be a massive, low-conductivity, high-porosity Eocene chalk. Vertical fractures and horizontal bedding planes were observed and mapped along approximately 1,200 m of scanline, 600 m of core and 30 two-dimensional trace planes. A bimodal distribution of size exists for the vertical fractures which occur as both single-layer fractures and multi-layer fractures. A bimodal distribution of log transmissivity was observed from slug tests conducted in packed-off, vertical intervals within the saturated zone. The different flow characteristics between the horizontal bedding planes and vertical-type fractures appear to be the cause of the bimodality. Two distinct conceptual models (discrete fracture network) were developed based on the fracture orientation, size, intensity and transmissivity statistics derived from field data. A correlation between fracture size and hydraulic aperture was established as the basis for calibrating the simulated model transmissivity to the field observations. This method of defining transmissivity statistically based on prior information is shown to be a reasonable and workable alternative to the usual conjecture approach towards defining transmissivity in a fractured-rock environment. 相似文献
2.
Judy Shamoun-Baranes Olivier Liechti Yoram Yom-Tov Yossi Leshem 《Boundary-Layer Meteorology》2003,107(3):673-681
Soaring migrants such as storks, pelicans and large birds of prey rely on thermal convection during migration. The convection model ALPTHERM was designed to predict the onset, strength, duration and depth of thermal convection for varying topographies for glider pilots, based on atmospheric conditions at midnight. We tested ALPTHERM predictions as configured for two topographies of central Israel, the Coastal Plains and the Judean and Samarian Mountains in order to predict altitudes of migrating white storks (Ciconia ciconia). Migrating flocks of white storks were tracked with a motorized glider, to measure maximum altitudes of migration during spring 2000. A significant positive correlation was found between the maximum daily altitudes of migration measured and the predicted upper boundary of thermal convection for the Coastal Plains and Samarian Mountains. Thirty-minute predictions for the Coastal Plains and Samarian Mountains correlated positively with measured maximum migration altitudes per thermal. ALPTHERM forecasts can be used to alter flight altitudes in both civil and especially military aviation and reduce the hazard of serious aircraft collisions with soaring migrants. 相似文献
3.
4.
Numerical investigations of 2D and 3D modes of large-scale convection in faulted aquifers are presented with the aim to infer possible transport mechanisms supporting the formation of thermal springs through fractured aquicludes. The transient finite elements models are based on idealized structural features that can characterize many hydrothermal systems. The sensitivity analysis of the fault permeability showed that faults cross-cutting the main regional flow direction allow groundwater to be driven laterally by convective forces within the fault planes. Therein thermal waters can either discharge along the fault traces or exit the fault through adjacent permeable aquifers. In the latter case, the resulting flow is helicoidally and transient. The location and the spacing between discharge areas can migrate with time, is not strictly constrained to the damage zones and reflects the wavelength of the multicellular regime in the fault zone.An illustrative example based on simplified structural data of the Lower Yarmouk Gorge (LYG) is presented. The numerical calculations indicate that crossing flow paths result from the coexistence of fault convection, developing for example along NE-SW oriented faults within the Gorge, and additional flow fields. The latter are induced either by topography NS gradients, e.g. perpendicular to the major axe of the Gorge, or by local thermal convection in permeable aquifers below the Eocene aquiclude. Sensitivity analysis of fault hydraulic conductivity (K) and the analytical solutions based on viscous-dependent Rayleigh theory show that K values between 2.3e−7 m/s and 9.3e– 7 m/s (i.e. 7 m/yr and 30 m/yr, respectively) favor coexisting transport processes. The uprising thermal plumes spread over several hundred meters forming clusters of springs, in agreement with observation, and which temperature fall within the measured ranges, i.e. 20 °C−60 °C. To some extent the models also reproduced the transient behavior of the spring temperature. Owing to the idealized nature of the presented models, the numerical results and the associated analytical solution can be applied to study the onset of thermal convection and resulting flow patterns of any fractured hydrothermal basin. 相似文献
5.
Karen Culcasi 《Geographical review》2016,106(2):258-263
The goal of this forum is to garner attention to the issues surrounding the Boycott, Divestment, and Sanctions (BDS) campaign against Israel, to help a broad audience better understand the complexity of BDS, and to engage geographers in the BDS debate. Including the editorial introduction, seven different experts on the issues of Palestine/ Israel have written six essays on BDS for this forum. The six essays represent a wide range of opinions while also echoing some similar themes. 相似文献
6.
Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall ≈ 50 mm), the diapir contains extensive karst systems of Holocene age. In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or clastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0–2 mm s?1 during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long-term mean downcutting rates are lower: an average rate of 8·8 mm a?1 was measured for the period 1986–1991 in the same sample passage. Quite independently, long-term mean rates of 6·2mm a?1 are deduced from 14C ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves. Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast-developing salt stream channels may serve as full-scale models for slower developing systems such as limestone canyons. 相似文献
7.
New finds of siliceous microfossils, mainly diatoms, are reported from hard limestone levels in the Campanian cherty Mishash Formation, Negev, Israel. Twenty taxa were recognized, of which Melosira campaniensis and Trinacria negeviensis are new species. Representatives of Ebridians are reported for the first time from Cretaceous sediments. Calcareous nannofossils are usually few and poorly preserved. The diversity of the micro- and nannofossil assemblages vary through the succession and points to fluctuations in the palaeoenvironmental conditions from restricted to more normal marine. The moderate preservation of the opaline microfossils within the limestones is probably the result of early diagenetic lithification. 相似文献
8.
Multi-borehole pumping and tracer tests on the 10 to 100-m scale were conducted in a fractured chalk aquitard in the Negev
Desert, Israel. Outcrop and core fracture surveys, as well as slug tests in packed-off intervals, were carried out at this
site to obtain the parameters needed for construction of a stochastic discrete fracture network (DFN). Calibration of stochastic
DFNs directly to the multiple borehole test data was inadequate. Instead, two equivalent deterministic DFN flow models were
used: the vertical-fractures (VF) model, consisting of only vertical fractures, and the fractures’ intersections (INT) model,
consisting of vertical and horizontal fractures with enhanced transmissivity at their intersections. Both models were calibrated
against the multi-borehole response of one pumping test and their predictions were tested against three other independent
pumping tests. The average accuracies of all transient drawdown predictions of the VF and INT models were 65 and 66%, respectively.
In contrast to this equality in average drawdown predictions of both models, the INT model predicted better important breakthrough
curve features (e.g., first and peak arrival times), than the VF model. This result is in line with previously assumed channeled
flow, derived from analytical analysis of these pumping and tracer tests.
Ronit Nativ, deceased, may her memory be blessed. 相似文献
9.
The subject of the security fence between Israel and the Palestinians in the West Bank has become a major issue in Israel
and in the world in the last several years. The main aim of this research is to reveal the attitudes and thoughts about the
fence held by local residents living in settlements (borderlanders) in the proximity of a part of the security fence that
has already been completed. The research concentrates on the western-Israeli side of the fence, as it aspires to delve into
and understand the meaning and implications of the security fence on matters such as personal security, safety of property
and freedom of movement, the possibility of maintaining social and economic ties between the two sides and feelings about
living in the area in the future. Underlying this research is the transformation occurring in the border area as a result
of its closure by construction of the security fence, after many years in which it was open partially. This process has many
diverse consequences, some of them contradictory, on the two populations residing near the border in Israel: the majority
Jewish population (the national borderlanders), and the minority Arab population (the transnational borderlanders). 相似文献
10.