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781.
The effects of geological heterogeneities and piezometric fluctuations on groundwater flow and chemistry in a hard-rock aquifer, southern India 总被引:1,自引:0,他引:1
Crystalline aquifers of semi-arid southern India represent a vital water resource for farming communities. A field study is described that characterizes the hydrodynamic functioning of intensively exploited crystalline aquifers at local scale based on detailed well monitoring during one hydrological year. The main results show large water-table fluctuations caused by monsoon recharge and pumping, high spatial variability in well discharges, and a decrease of well yields as the water table decreases. Groundwater chemistry is also spatially variable with the existence of aquifer compartments within which mixing occurs. The observed variability and compartmentalization is explained by geological heterogeneities which play a major role in controlling groundwater flow and connectivity in the aquifer. The position of the water table within the fracture network will determine the degree of connectivity between aquifer compartments and well discharge. The presented aquifer conceptual model suggests several consequences: (1) over-exploitation leads to a drop in well discharge, (2) intensive pumping may contribute to the hydraulic containment of contaminants, (3) groundwater quality is highly variable even at local scale, (4) geological discontinuities may be used to assist in the location of drinking-supply wells, (5) modeling should integrate threshold effects due to water-table fluctuations. 相似文献
782.
Randy L. Stotler Shaun K. Frape Humam Taha El Mugammar Craig Johnston Ian Judd-Henrey F. Edwin Harvey Robert Drimmie Jon Paul Jones 《Hydrogeology Journal》2011,19(1):101-115
The Waterloo Moraine is a stratigraphically complex system and is the major water supply to the cities of Kitchener and Waterloo in Ontario, Canada. Despite over 30?years of investigation, no attempt has been made to unify existing geochemical data into a single database. A composite view of the moraine geochemistry has been created using the available geochemical information, and a framework created for geochemical data synthesis of other similar flow systems. Regionally, fluid chemistry is highly heterogeneous, with large variations in both water type and total dissolved solids content. Locally, upper aquifer units are affected by nitrate and chloride from fertilizer and road salt. Typical upper-aquifer fluid chemistry is dominated by calcium, magnesium, and bicarbonate, a result of calcite and dolomite dissolution. Evidence also suggests that ion exchange and diffusion from tills and bedrock units accounts for some elevated sodium concentrations. Locally, hydraulic “windows??cross connect upper and lower aquifer units, which are typically separated by a clay till. Lower aquifer units are also affected by dedolomitization, mixing with bedrock water, and locally, upward diffusion of solutes from the bedrock aquifers. A map of areas where aquifer units are geochemically similar was constructed to highlight areas with potential hydraulic windows. 相似文献
783.
This study concerns Tarbela dam reservoir which is a major resource of Pakistan in terms of electricity generation and irrigation
supplies. Rapid filling of reservoir due to sediment transported and deposited by Indus River is described and analysed in
this article. Causes of sediment deposition and their impact on dam’s function and life are studied. The main characteristic
parameters of the site are presented. The morphological evolution of the reservoir bed induced by dam construction, between
the year 1974 when the River bed was in its original state before dam construction, and the situation of the river bed after
the deposition of the sediment in the year 2006, is examined. A numerical model developed in this study (Khawaja and Sanchez
in Tarbela dam: a numerical model for sediment management in the reservoir; coastal and maritime mediterranean conference,
1st edn, Hammamet, pp 111–114, 2009) allows obtaining the above-stated provisional evolution of the reservoir over the coming years. Finally, five potential
remedial solutions are thoroughly discussed. 相似文献
784.
Ahmed I. Rushdi 《Arabian Journal of Geosciences》2011,5(5):1093-1102
Surface seawater samples from Kamaran Strait of Yemen were collected for physical and chemical parameter determinations. This work reports the results of air and surface seawater temperature, salinity, pH, and total alkalinity measurements. The air temperature ranged from 29.9°C to 36.5°C with an average value of 31.5?±?1.5°C, whereas the seawater surface temperature ranged from 34.0°C to 36.0°C with a mean value of 34.5?±?0.5°C. The salinity was observed to be high, ranging from 38.03 to 38.81 with an average value of 38.45?±?0.22. The pH ranged from 7.74 to 8.27 with a mean value of 8.11?±?0.10. The total alkalinity was found to range from 2.3860 to 2.5000 meq L?1 with an average value of 2.4288?±?0.0351 meq L?1. The result of the study showed that there was a negative correlation between the pH and surface seawater temperature and salinity. The surface seawater of the Kamaran Strait was found to be several fold supersaturated with respect to calcium carbonate. The measured percent degree of saturation ranged from 454% to 668% with respect to calcite and from 246% to 361% with respect to aragonite. The lowest value of supersaturation with respect to both calcite and aragonite were found in front of as-Salif port, where human and developmental activities are intensively increased. The visual inspection of coral reefs distribution and their intensity were obviously observed in areas of high value of supersaturation with respect to both minerals, high transparency of seawater column, and low human activities. Further studies are needed to investigate the occurrence, distribution, and mineralogy of corals and the effects of physical and chemical parameters upon their growth in the region. 相似文献
785.
Lawal Billa Hamid Assilzadeh Shattri Mansor Ahmed R. Mahmud Abdul H. Ghazali 《Central European Journal of Geosciences》2011,3(3):309-317
Observed rainfall is used for runoff modeling in flood forecasting where possible, however in cases where the response time of the watershed is too short for flood warning activities, a deterministic quantitative precipitation forecast (QPF) can be used. This is based on a limited-area meteorological model and can provide a forecasting horizon in the order of six hours or less. This study applies the results of a previously developed QPF based on a 1D cloud model using hourly NOAA-AVHRR (Advanced Very High Resolution Radiometer) and GMS (Geostationary Meteorological Satellite) datasets. Rainfall intensity values in the range of 3–12 mm/hr were extracted from these datasets based on the relation between cloud top temperature (CTT), cloud reflectance (CTR) and cloud height (CTH) using defined thresholds. The QPF, prepared for the rainstorm event of 27 September to 8 October 2000 was tested for rainfall runoff on the Langat River Basin, Malaysia, using a suitable NAM rainfall-runoff model. The response of the basin both to the rainfall-runoff simulation using the QPF estimate and the recorded observed rainfall is compared here, based on their corresponding discharge hydrographs. The comparison of the QPF and recorded rainfall showed R2 = 0.9028 for the entire basin. The runoff hydrograph for the recorded rainfall in the Kajang sub-catchment showed R2 = 0.9263 between the observed and the simulated, while that of the QPF rainfall was R2 = 0.819. This similarity in runoff suggests there is a high level of accuracy shown in the improved QPF, and that significant improvement of flood forecasting can be achieved through ‘Nowcasting’, thus increasing the response time for flood early warnings. 相似文献
786.
787.
Hugo Delile Abdelhakim Abichou Ahmed Gadhoum Jean‐Philippe Goiran Elisa Pleuger Jean‐Yves Monchambert Andrew Wilson Elizabeth Fentress Josephine Quinn Imed Ben Jerbania Faouzi Ghozzi 《Geoarchaeology》2015,30(4):291-306
Although the ancient site of Utica has been studied since the 19th century, the location of its harbors remains unresolved as they were buried under sediments as the Mejerda delta prograded and left Utica 10 km inland. Using relief data and a coring survey with sedimentological analysis, we identify the dynamics of the delta's progradation, which produced a double system of alluvial fans. These show that the ancient bay of Utica silted up faster and earlier than was thought, probably before the end of the Punic period. Combined with the radiocarbon dates from coring, this suggests that the harbor lay on the north‐western side of the Utica promontory, communicating with the sea by a marine corridor west of the northern compartment of the delta. As the infilling of the ancient bay progressed, this corridor narrowed until it disappeared completely in the early 5th/mid‐6th century A.D., when a peat bog developed on the northern side of the promontory, sealing the fate of Utica as a port. This relative environmental stability ended in the 9th–10th century A.D. when about 4 m of sediment, probably of fluvial origin, covered the peat bog, leaving the site more than 4.5 m above the local sea level. 相似文献
788.
Research on experiment and calculation of foam bursting device 总被引:1,自引:0,他引:1
Hazaea Mohammed Youhong SUN Ould El HousseinYarbana Longxiang XU Al-Aswar Fahmi 《世界地质(英文版)》2007,10(1)
This research presents experimental data on mechanical foam bursting device, based on the high speed of air fluid impinging insidethe foam bursting device, foam bubbles disrupted as a consequence of pressures changed very quickly as shear force and their impact forces. Experimental data on foam-bursting capacity have been presented. Designed device can provide effective foam bursting on collapse foam. 相似文献
789.
E. S. Farahat M. M. El Mahalawi G. Hoinkes A. Y. Abdel Aal 《Mineralogy and Petrology》2004,82(1-2):81-104
Summary Geochemical and petrographical data of three ophiolitic pillow metavolcanic occurrences from the central Eastern Desert of Egypt are presented. The investigated rocks show a subalkaline, tholeiitic affinity. Chemical data indicate that the metavolcanics have transitional within-plate basalt to island-arc basalt features, which are characteristics of basalts formed in ensialic back-arc basins. The association of the investigated ophiolites with volcanoclastic metasedimentary rocks of marine to continental facies is a further confirmation of their ensialic evolution. This suggestion, along with the geochronologic, isotopic and crustal growth rate evidences, revives interest in models that involve contribution from a pre-Pan-African continental crust at least in the southern part of the Egyptian Shield. Mixing between a depleted mantle-derived magma and an enriched crustal melt, a process similar to AFC (assimilation and fractional crystallization), is suggested for the evolution of the investigated rocks. This study provides evidence for formation of some ophiolites in the Eastern Desert of Egypt in continental (ensialic) back arc basins. 相似文献
790.
Unsteady free-convection flows near an infinite vertical plate in a rotating medium in the presence of a constant transverse magnetic field are investigated under an arbitrary time-dependent heating of the plate. By using the Laplace transform technique, the Green's function of the problem is determined and exact solutions are obtained for special cases of the time-dependent heating effect. The thermal influence on skin friction at the plate and the displacement thickness of the boundary layer are determined, and the structure of the thermal wave trains is discussed.Formerly Kulshrestha. 相似文献