In Egypt, the strata of major hydrogeological interest are composed of a sandstone complex ranging from Cambrian to Upper Cretaceous in age. This sandstone complex, commonly known as the Nubian Sandstone, has a thickness varying from less than 500 m to more than 3000 m and rests directly on Precambrian basement.
This simple picture is complicated by a number of major structural fault and fold axes which traverse the region in a north-easterly direction. The sandstones reach their max-imum development in the Ain Dalla basin, a downthrown structural block SW of Bahariya oasis. Basement features exercise a dominant control on the structural and sedimentological form of the sandstone complex.
In spite of the structural complications, the Nubian sand-stone, underlying an extensive area of Egypt, probably con-stitutes a single hydrogeological system to the W of the Gulf of Suez. To the E, on the Sinai peninsula, a second system may exist with some connection to the main western system in the N.
The main western system, which extends into Libya and Sudan, comprises a multi-layered artesian basin where huge groundwater storage reserves were accumulated, principally during the pluvials of the Quaternary.
The carbonate rocks overlying the Nubian Sandstone complex display karst features locally and are recharged by upwards leakage from the underlying major aquifer.
Large-scale development of the Nubian Sandstone aquifer in Egypt has been under consideration since 1960. Latest proposals for the New Valley development project involve exploitation at the annual rate of 156.2 × l06m3 at El-Kharga, 509.2 at