Hydrogeological situation

The study area was explored up to maximum depth of 500 m by 32 test holes, of which 16 tapping fresh groundwater were converted into tube wells. The unconsolidated sediments are mainly of fluvial origin and consist of slightly calcareous and micaceous, fine-grained sand covered and interbedded by sandy-silty clays (Fig. 3). With increasing depth the sands become fine- to medium-grained, locally even coarse-grained. Those sediments form a typical semi-confined aquifer system down to a depth of about 100 m. It has a storativity ranging from 3 x 10"4to7 x 10"3. The horizontal hydraulic conductivity K increases from 5 m/day in the east to 35 m/day in the west. The total porosity of 40% was determined by grain size analysis, while the effective porosity was estimated to be 15%. The groundwater table is about 20 m below surface. The hydraulic gradient between east and SW is about 0.3%c (Ashraf & Ismail 1994).

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