Groundwater Modeling of Multi-Aquifer Systems Using GMS

Abstract

The Nubian Sandstone complex in the western desert is a part of the major regional Nubian aquifer system comprising West Africa. The different rock strata deposited in localities forming the units of the aquifer system. Farafra Oasis lies in the northern part of the Dakhla basin. In its southern region, the Nubian Sandstone (deep aquifer) is overlained by Dakhla shale but in the central and northern regions by fissured chalky limestone (shallow aquifer). The two overlaying aquifers in Farafra Oasis represent a typical hydrogeological model of a huge multi-layered artesian basin extending over the territory of Egypt. The Post Nubian aquifer played an essential role in the development of Farafra Oasis for a long time through the many springs issued from this aquifer. The rapid drilling process of deep wells started in 1960s led to stop flowing of many springs and wells plus the depletion in discharges and pressure of many others. Therefore, there is a real danger of either dewatering or increasing the water depths to uneconomic lifting depths for both the shallow and deep aquifers. A two-dimension flow model GMS (Groundwater Modeling System) was used to investigate this problem. Application of the present conditions indicated that drawdowns in the Post Nubian aquifer range from 5 m to about 9 m. The second scenario tries to sustain the groundwater utilities in the Post Nubian aquifer through a group of procedures. Accordingly, drawdowns are expected to range from 5 m to 8.6 m in the Post Nubian aquifer. According to this scenario, 3 m decline in the Nubian Sandstone aquifer followed by declining in the Post Nubian by about 1 m.