Groundwater Potentialities of the Atbara Valley Khashm Elgirba - Elsasareeb Strip Kassala state, Eastern Sudan.

Abstract

ABSTRACT I-Iydrogeological and. geophysical investigations were applied to study the Groundwater Potentialities of the Karab Formation in the study area, and to investigate the geology of the study area which is located from Khashm El Girba dam up to Elsasareeb area downstream at the both sides of the River Atbara. The Study area lies in Eastern Sudan in the Kassala State bounded by latitudes l5.0° and l5.5° N and longitudes of 35.40” and 36° E. The study area is rectangular in shape with a total surface area of approximately 500 kmz. The geology of the study area can be concluded in the following units; the basement complex consists mainly of slates, schist, granitic gneiss, quartzite and pegmatite dylces. Cenozoic Basalts, which is found only at the southern part of the study area. River Atbara sediments consists of conglomerate, silicified sandstones, sands, silt and intercalated layers of clay. These sediments represent the saturation zone in the study area. Unconsolidated Karab formation consists dominantly of clay, sand, gravel and organic material, based on the soil investigations have been carried out. The Superficial deposits consist of clays and sandy clays form the top most confining layer. The major structural phenomena in the study area is the E-W fault near Butana Bridge and some minor faults distributed in the study area controlling the courses of the scattered khors and wadies. The electrical resistivity method was applied, in which 36 VES were carried out. The Vertical electrical soundings were distributed to cover the study area. The geophysical investigations indicated that the depth to the basements rocks varies between 45-80 in, being 4_5m near the river banks and more deep away from the river. The thickness of the aquifer varies between '15-20 m and is controlled by the thickness of the clay cover which lies directly over the aquifer zone. - I-Iydrogeological investigations indicated that the depth to water level varies between ll — 40 m, at about ll m near the river and increasing outside direction from the river. The transmissivity of the aquifer is estimated at l000 to 1500 m2\d. The hydraulic conductivity in the study area ranges between 50 to 75 m/day. The groundwater flow is toward the NW direction with the hydraulic gradient (I) of 0.005 in average. The River Atbara and direct rainfall are the main sources of recharge to the aquifers. The annual average discharge of River Atbara downstream of dam estimated as 12 X 109 m3\ year and the quantity of recharge to the groundwater estimated as 77.7>< 106 m3\ year. The groundwater storage is estimated as 1.45 >< 109 m3 .The annual reserve of groundwater in the study area calculated as 48.7 >< 106 cubic meters.