Modelling of groundwater flow in heterogeneous porous media by finite element method     

Hassan Smaoui  Lahcen Zouhri  Abdellatif Ouahsine  Erick Carlier 《水文研究》2012,26(4):558-569

The HySuf‐FEM code (Hydrodynamic of Subsurface Flow by Finite Element Method) is proposed in this article in order to estimate the spatial variability of the transmissivity values of the Berrechid aquifer (Morocco). The calibration of the model is based on the hydraulic head, hydraulic conductivity and recharge. Three numerical tests are used to validate the model and verify its convergence. The first test case consists in using the steady analytical solution of the Poisson equation. In the second, the model has been compared with the hydrogeological system which is characterized by an unconfined monolayer (isotropic layer) and computed by using PMWIN‐MODFLOW software. The third test case is based on the comparison between the results of HySuf‐FEM and the multiple cell balance method in the aquifer system with natural boundaries case. Good agreement between the Hydrodynamic of Subsurface Flow, the numerical tests and the spatial distribution of the thickening of the hydrogeological system is deduced from the analysis and the interpretations of hydrogeological wells. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

SWAT‐simulated hydrological impact of land‐use change in the Zanjanrood basin,Northwest Iran     

Golaleh Ghaffari  Saskia Keesstra  Jamal Ghodousi  Hassan Ahmadi 《水文研究》2010,24(7):892-903

Understanding the impacts of land‐use changes on hydrology at the watershed scale can facilitate development of sustainable water resource strategies. This paper investigates the hydrological effects of land‐use change in Zanjanrood basin, Iran. The water balance was simulated using the Soil and Water Assessment Tool (AVSWAT2000). Model calibration and uncertainty analysis were performed with sequential uncertainty fitting (SUFI‐2). Simulation results from January 1998 to December 2002 were used for parameter calibration, and then the model was validated for the period of January 2003 to December 2004. The predicted monthly streamflow matched the observed values: during calibration the correlation coefficient was 0·86 and the Nash–Sutcliffe coefficient 0·79, compared with 0·80 and 0·79, respectively, during validation. The model was used to simulate the main components of the hydrological cycle, in order to study the effects of land‐use changes in 1967, 1994 and 2007. The study reveals that during 1967 a 34·5% decrease of grassland with concurrent increases of shrubland (13·9%), rain‐fed agriculture (12·1%), bare ground (5·5%) irrigated agriculture (2·2%), and urban area (0·7%) led to a 33% increase in the amount of surface runoff and a 22% decrease in the groundwater recharge. Furthermore, the area of sub‐basins that was influenced by high runoff (14–28 mm) increased. The results indicate that the hydrological response to overgrazing and the replacing of rangelands (grassland and shrubland) with rain‐fed agriculture and bare ground (badlands) is nonlinear and exhibits a threshold effect. The runoff rises dramatically when more than 60% of the rangeland is removed. For groundwater this threshold lies at an 80% decrease in rangeland. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Observations of desert flood bores     

Marwan A. Hassan 《地球表面变化过程与地形》1990,15(5):481-485

Flood bores have been measured in desert stream floods. The bores were steep and small pebbles were observed to be pushed ahead. Bore velocity changed downstream and was controlled by local channel geometry. In narrow reaches, the bore advanced at rates twice those of wide reaches. Mean bore velocity was about 50 per cent of that of mean flow at peak flood discharge. The surfaces of shallow bores were covered by air foams. This was not the case in deeper, faster examples.  相似文献   

Gravity map of Kalabsha area, northwest of Aswan Lake, and its structural significance     

E.M. Abdelrahman  A. Tealeb  H.A. Ahmed 《Journal of Geodynamics》1991,14(1-4)

A detailed gravity survey was carried out in one of the seismo-active areas at the northwestern region of the High Dam Lake (Kalabsha area) to study its subsurface structure. In order to understand the seismicity of the area, the establishment of a geodynamic model from geological and geodetic data is of great importance. After a series of adjustments and corrections of the measured gravity data, free-air and Bouguer anomaly maps were constructed for the Kalabsha area, and several interpretation techniques were applied to analyse these anomalies. The results of the analysis indicate that the Kalabsha area is affected by several faults trending mainly E-W and N-S. The active area located west of Gebel Marawa is bounded by a set of faults striking NE-SW, N-S and E-W. The throws of these faults range from 160 to 370 m.The minimum depth to the basement complex is about 200 m and its maximum depth is around 600 m. The thickness of the sedimentary column (Nubia sandstone) in the Kalabsha area decreases due west and increases toward the southern and eastern parts of the area. The results explain the tectonic framework of the area well.  相似文献   

Drought and human adjustment in Saudi Arabia   总被引：1，自引：0，他引：1  

Abdulla Ahmed Al-Taher 《GeoJournal》1994,33(4):411-422

Drought is one of the natural hazards which causes death and damage for property particularly in drylands of the world. Drought as a natural hazard tends to limit and disrupt human activities. On the other hand, man has tried to adjust his living conditions to this hazard. The adjustment to drought is different from one country to another. Adjustment to drought is affected by culture, income, and by the political system in the country. In the case of Saudi Arabia adjustment to drought hazard is usually the work of both individuals, and government. The Saudi Arabian government has spent large sums of money to reduce impact of drought hazard.  相似文献   

On the distribution of rainfall over the Sultanate of Oman     

Ahmed Abdalla Ahmed Babikir Dr. 《GeoJournal》1985,11(2):165-172

Rainfall distribution over the Sultanate of Oman is analysed. Data from seven recently installed weather stations as well as supporting data from scattered sources were used. Distribution maps were drawn. NW and NE winter wind meet resulting in troughs and rainfall on the Mountains and Coastal Strips. Summer monsoon wind dominates the S. Central areas of overlap receive light showers from both summer monsoons and winter local troughs. Heavier amounts of rainfall are generally associated with high altitude.  相似文献   

Wind gradients at meteor heights over mid-latitude stations     

P. C. S. Devara  G. Chandrasekhar  M. I. Ahmed 《Journal of Earth System Science》1986,95(3):427-434

The gradients of amplitude and phase of diurnal and semidiurnal components of zonal and meridional winds in the height intervals of 80–90 km and 90–100 km are studied using the meteor wind radar data collected at Atlanta (34°N, 84°W) during the period August 1974–March 1978. The results are compared with those at Adelaide (35°S, 139°E). It is found that the gradients vary in an opposite manner between the two height intervals.  相似文献   

A petrographic and fluid inclusion comparison of silver-poor and silver-rich zinc-lead ores,N.E. Washington State     

Philip E. Brown  Gaafar A. Ahmed 《Mineralium Deposita》1986,21(2):156-163

Many of the zinc-lead deposits of NE Washington State are poorly known examples of Mississippi Valley Type (MVT) mineralization. This study compares inclusion fluids from the Josephine Breccia ores with the later cross-cutting sulfide-bearing quartz veins. The breccia ores are cemented mainly by open space fillings of dolomite, sphalerite, quartz, galena, jasperoid and calcite. Replacement is of minor importance. Ore and gangue deposition occurred over the range 150–250 °C with most of the temperatures less than 200 °C. The aqueous brines typically contain 17–23 equivalent weight percent NaCl with often substantial amounts of Ca and/or Mg chlorides. Homogenization temperatures do not delineate any cooling or paragenetic sequence. The cross-cutting vein quartz contains CO₂-rich inclusions with overall densities usually less than 0.7 g/cc and homogenization temperatures from 250–325 °C. Sulfur isotope analyses yield two populations with the quartz vein ores being lighter (<13 permil CDT) than the average for the conformable ores. The later veins are not remobilized MVT sulfides but represent a separate, high-silver period of mineralization.  相似文献   

The non-linear seismic response of AGR core graphite brick slices—correlation of experimental and analytical results     

Khalid Ahmed  Stefan Stojko 《地震工程与结构动力学》1987,15(2):159-188

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Ulvöspinel in native iron-bearing assemblages and the origin of these assemblages in basalts from Ovifak,Greenland, and Bühl,Federal Republic of Germany     

Olaf Medenbach  Ahmed ElGoresy 《Contributions to Mineralogy and Petrology》1982,80(4):358-366

Euhedral crystals of ulvöspinel are found in many of the native-iron-bearing xenoliths from the basalt of Bühl near Kassel (West Germany) and Ovifak on Disko Island (West Greenland). The typical assemblage of these xenoliths at both localities is: native Fe, troilite, cohenite, ulvöspinel, ilmenite, olivine, and plagioclase, as well as silicate glass containing droplets of former Fe and troilite melt. The ulvöspinel subsolidus textures and intergrowths also indicate identical cooling histories for the xenoliths in both cases. Ulvöspinel crystallized after the formation of iron, but still above the Fe-FeS eutectic at 988° C. A subsequent strong drop in oxygen fugacity revealed partial breakdown of ulvöspinel according to the reaction .Microprobe analyses of a Bühl xenolith indicate that ulvöspinel contains up to 4.7 w.t.% MnO, while olivine compositions correspond to Fa_64–74Fo_12–24Te_12–15. The entire xenolith contains 1.9 w.t.% MnO. This fact, together with the geological evidence and the occurrence of corroded quartz relicts within some of the xenoliths provides clear evidence for reduction under near-surface conditions in a blast-furnace-like process. The reducing agent was coal from the Tertiary seams cut by the erupting basalt, while the xenolith source material most probably was spherosiderite, which is very common in the coals and would explain the high MnO content. Consequently, the presence of cohenite is not necessarily an indicator of high pressure.The analogies between the Bühl and Ovifak localities and their xenoliths strongly suggest a similar formation through near surface reduction and not derivation from the mantle.  相似文献