Strong field evidence of directional permeability scale effect in fractured rock

2006 ◽  
Vol 319 (1-4) ◽  
pp. 227-236 ◽  
Author(s):  
Walter A. Illman
Keyword(s):  
Scale Effect ◽  
Strong Field ◽  
Fractured Rock ◽  
Field Evidence ◽  
Directional Permeability

scholarly journals Irrigation enhances precipitation at the mountains downwind

2010 ◽  
Vol 7 (3) ◽  
pp. 3109-3127 ◽  
Author(s):  
J. Jódar ◽  
J. Carrera ◽  
A. Cruz
Keyword(s):  
Transition Period ◽  
Strong Field ◽  
Water Volume ◽  
Monthly Precipitation ◽  
Field Evidence ◽  
Before And After ◽  
Actual Field ◽  
Annual Water ◽  
Rainfall Statistics ◽  
Broad Region

Abstract. Atmospheric circulation models predict an irrigation-rainfall feedback. However, actual field evidences are very weak. We present strong field evidence about an increase in rainfall at the mountains located downwind of irrigated zones. We chose two regions, located in semiarid southern Spain, where irrigation started at a well defined date, and we analyzed rainfall statistics before and after the beginning of irrigation. Analyzed statistics include the variation of (1) mean rainfall Δ P, (2) ratio of monthly precipitation to annual precipitation Δ r, and (3) number of months with minimum rainfall episodes Δ Pmin after a transition period from unirrigated to irrigated conditions. All of them show statistically significant increases. Δ P and Δ r show larger and more statistically significant variations in June and July. Their variation is proportional to the mean annual water volume applied in the neighboring upwind irrigation lands. Variations in Δ Pmin are statistically significant in the whole summer. That is, the number of months with some rain displays a relevant increase after irrigation. However, increase in rainfall while statistically significant is distributed over a broad region, so that it is of little relevance from a water resources perspective. The joint increment in Δ P and Δ Pmin after the irrigation transition period denotes a net increase in the number of months having a minimum cumulated precipitation in summer.

scholarly journals Irrigation enhances precipitation at the mountains downwind

2010 ◽  
Vol 14 (10) ◽  
pp. 2003-2010 ◽  
Author(s):  
J. Jódar ◽  
J. Carrera ◽  
A. Cruz
Keyword(s):  
Water Resources ◽  
Strong Field ◽  
Monthly Precipitation ◽  
Rainfall Events ◽  
Field Evidence ◽  
Before And After ◽  
Actual Field ◽  
Annual Volume ◽  
Rainfall Statistics ◽  
Broad Region

Abstract. Atmospheric circulation models predict an irrigation-rainfall feedback. However, actual field evidences for local evaporation recycling (moisture feedback) are weak. We present strong field evidence for an increase in rainfall at the mountains located downwind of irrigated zones. We chose two regions, located in semiarid southern Spain, where irrigation started at a well defined date, and we analyzed rainfall statistics before and after the beginning of irrigation. Analyzed statistics include the variation of (1) mean rainfall Δ P, (2) ratio of monthly precipitation to annual precipitation Δ r, and (3) number of months with noticeable rainfall episodes Δ Pmin after a shifting from unirrigated to irrigated conditions. All of them show statistically significant increases. Δ P and Δ r show larger and more statistically significant variations in June and July than in August. They also tend to increase with the annual volume of water applied in the neighbouring upwind irrigation lands. Increases in Δ Pmin are statistically significant during the whole summer. That is, the number of noticeable rainfall events displays a relevant increase after irrigation. In fact, it is this number, rather than sporadic large rainfall episodes what makes the summers wetter. The increase in rainfall, while statistically significant, is distributed over a broad region, so that it is of little relevance from a water resources perspective, although it may enhance vegetation yield.

Sub-pingo water lenses, Tuktoyaktuk Peninsula, Northwest Territories

1978 ◽  
Vol 15 (8) ◽  
pp. 1219-1227 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Pore Water ◽  
High Pressures ◽  
Strong Field ◽  
Source Area ◽  
Ground Level ◽  
Drill Hole ◽  
Maximum Height ◽  
Pressure Transducers ◽  
Field Evidence ◽  
Pore Water Pressures

In 1976 and 1977 three growing pingos were drilled for the purpose of measuring sub-pingo water pressures beneath aggrading permafrost. All holes drilled through permafrost in the pingos and adjacent lake flats produced artesian flow. The flow from the pingos was clear and as the gushers rose to a maximum height of 3 m above ground level, large sub-pingo water lenses under pressure seemed evident. The existence of the lenses was confirmed by sounding their depths once permafrost was penetrated.One pingo had a 2.2 m deep water lens beneath the top. Pressure transducers, installed in the sub-pingo water lenses or in the unfrozen sands beneath, all indicated pressure heads above the tops of the pingos. Precise levelling of bench marks showed that the top of one pingo subsided 60 cm from drill hole water loss. Calculations for one pingo show that the water lens has likely been present since the birth of the pingo. Recharge from a distant source cannot account for the high pressures because the hydrostatic heads are above the pingo tops and as the pingo tops are usually the highest features in Tuktoyaktuk Peninsula, there can be no available higher source area; even if there were distant sources, the countless intervening lakes would quickly release any artesian pressures; and numerous pingos have grown up in drained lakes which are either too small or too young to have through-going taliks beneath them. Therefore, the observed water lenses and high sub-pingo pore water pressures cannot be attributed to recharge but provide strong field evidence for pressure generated by pore water expulsion.

Leakage of dense, nonaqueous phase liquids from waste impoundments constructed in fractured rock and clay: theory and case history

1992 ◽  
Vol 29 (2) ◽  
pp. 234-244 ◽  
Author(s):  
Bernard H. Kueper ◽  
C. Stephan Haase ◽  
Helen L. King
Keyword(s):  
Water Table ◽  
Case History ◽  
Fractured Rock ◽  
Nonaqueous Phase Liquids ◽  
Fracture Aperture ◽  
Dense Nonaqueous Phase Liquids ◽  
Two Phase ◽  
Field Evidence ◽  
Wide Range ◽  
Migration Pathways

This paper examines the behaviour of dense, nonaqueous phase liquids (DNAPLs) in fractured media, with an emphasis on waste-disposal ponds constructed in fractured clay and rock. Calculations are presented to estimate the height of DNAPL that may accumulate at the base of a disposal pond prior to initial entry into a water-saturated fracture. This height is found to be a function of the fluid densities, the DNAPL–water interfacial tension, the fracture aperture, and the position of the water table. A numerical model is applied to estimate the steady-state rate of DNAPL leakage from a disposal pond underlain by vertical fractures. This rate of leakage is found to be a function of the spacing of fractures, the fracture aperture, the DNAPL density, and the height of the water table in the formation outside of the impoundment. It is demonstrated that a wide range of leakage rates can occur over a relatively narrow range of parameters. A conceptual analysis of two-phase flow examines the conditions that lead to both uniform and sparse DNAPL migration pathways beneath a disposal pond in fracture networks. A case history is presented as field evidence of the concepts discussed. In particular, the case history demonstrates that sparse DNAPL migration pathways can occur in fractured rock, and that relatively low dissolved phase concentrations can exist in the immediate vicinity of DNAPL source zones. Key words : nonaqueous phase liquids, ground water, fractures, disposal ponds.

High resolution STEM imaging study on high Tc superconductor YBa2CuaO7-x

1988 ◽  
Vol 46 ◽  
pp. 882-883
Author(s):  
H.-J. Ou ◽  
J. M. Cowley
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Grain Boundary ◽  
Strong Field ◽  
Imaging Study ◽  
Structure Defects ◽  
High Tc ◽  
High Tc Superconductor ◽  
Diffraction Patterns ◽  
Lattice Planes

Using the dedicate VG-HB5 STEM microscope, the crystal structure of high Tc superconductor of YBa2Cu3O7-x has been studied via high resolution STEM (HRSTEM) imaging and nanobeam (∽3A) diffraction patterns. Figure 1(a) and 2(a) illustrate the HRSTEM image taken at 10' times magnification along [001] direction and [100] direction, respectively. In figure 1(a), a grain boundary with strong field contrast is seen between two crystal regions A and B. The grain boundary appears to be parallel to a (110) plane, although it is not possible to determine [100] and [001] axes as it is in other regions which contain twin planes [3]. Following the horizontal lattice lines, from left to right across the grain boundary, a lattice bending of ∽4° is noticed. Three extra lattice planes, indicated by arrows, were found to terminate at the grain boundary and form dislocations. It is believed that due to different chemical composition, such structure defects occur during crystal growth. No bending is observed along the vertical lattice lines.

RADIATIVE COLLISIONS IN A STRONG FIELD REGIME

1985 ◽  
Vol 46 (C1) ◽  
pp. C1-85-C1-95
Author(s):  
P. Pillet ◽  
R. Kachru ◽  
N. H. Tran ◽  
W. W. Smith ◽  
T. F. Gallagher
Keyword(s):  
Strong Field
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