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Abstract
According to the drilling information collected from the new wells in the area between Abu Simbel and Toshka the hydrogeological and hydrochemical settings were studied. Also a simulating of the Nubian Sandstone aquifer in suitable model (MODFLOW) provides good management and conservation of its groundwater.
The area in concern lies on the western side of Lake Nasser between Abu Simbel and Toshka where it occupies a surface area of about 11000 km2 between latitudes 220 15. and 230 15. N and longitudes 310 00- and 320 00- E. It lies within the arid zone of Egypt, being warm in winter and rather hot in summer with wide diurnal variations and almost no precipitation.
Geomorphologically, the surface of the area between Abu Simbel and Toshka is discriminated into the following five geomorphic units; Aswan High Dam reservoir, the Nile Valley, Wadi Kurkur pediplain, Toshka depression and West Dungle plain.
Stratigraphically, the Precambrian basement rocks are the oldest rocks in the southern part of Egypt. The sedimentary section overlying the, basement complex in the study area is dominated by a succession belonging to Jurassic, Cretaceous, Paleocene, Eocene, Oligocene and Quaternary. The Nubian Sandstone succession in the area is built up of Abu Simbel Formation, Lake Nasser Formation, Sabaya Formation’ and Kiseiba Formation. The main component of the Nubian Sandstone aquifer is a ferruginous sandstone with shale and clay intercalations ranging in thickness from 170 m to 320 m.
Structurally, the study area is controlled by tensional forces leading to great number of east-west faults and vertical or diagonal uplift of the basement rocks. There are four sets of faults which can’ be grouped into the following: East African system (Trending N-S), Tythean system, (Trending E¬W), Erthrean or African system (Trending NW-SE) and Aualitic system (Trending NE-SW). The obtained results indicate that the lithological characteristics and the structure are strongly affecting the groundwater flow pattern as well as the potentiality of the aquifer.
Hydrogeologically, the Nubian Sandstone aquifer overlies the basement rocks and capped by Quaternary deposits. The basement uplifting is very clear and is responsible for the occurrence of inclind beds around the basement outcrops. Several basement outcrops are noticed in the area which vary from few hundred square meters to tens of square kilometers. The groundwater exists under unconfmed to semiconfmed condition. The semiconfined behaviour is more detected towards the middle parts of the area