Non-renewable groundwater resources: a ... - unesdoc - Unesco

CHAPTER 5 ■ REGIONAL CASESNubian Sandstone Aquifer SystemMohamed BakhbakhiIntroductionThe Nubian Sandstone Aquifer System (NSAS) covers approximately 2.2 million km 2 of NorthEast Africa (Figure 1). It is shared by Egypt, Libya, Sudan and Chad. No recent significant groundwaterrecharge is detectable (Thorweih, 1986), thus planning the use or mining of theseresources should be based on the expectation that sometime in the future the water in theaquifers will be fully depleted. A policy for progressive aquifer depletion, i.e. mining of thegroundwater in storage, is needed.The demands for using this groundwater are considerable and are growing. As a result ofpopulation growth, food demand and economic growth the pressure on groundwater in theregion has increased rapidly during the past three decades. Consequently exploitation of thesenon-renewable resources is currently occurring. To more effectively manage the withdrawal anduse of this groundwater over time it is important to assess the aquifer storage capacity and totentatively calculate the effective recoverable groundwater volume that can be used for developmentin the four sharing countries.Assessment of the groundwater resourcesThe Nubian Sandstone Aquifer System is considered to be one of the most important groundwaterbasins in the world. The Nubian Sandstone Aquifer System can be divided into two majorreservoirs as shown in Figure 1. The oldest and the most extended reservoir, the Nubian AquiferSystem (NAS), is largely unconfined. It includes a number of aquifers that are hydraulicallyconnected. The other reservoir includes parts of Libya and Egypt. It is referred to as the PostNubian Aquifer System (PNAS). Low permeability layers separate the two reservoir systems.The Nubian Aquifer SystemThe Nubian Aquifer System (Figure 1) extends over a vast area in Egypt, Libya, Sudan and Chad.It is bounded in the east by the impervious mountain ranges of the Red Sea and northwardsby the Suez Canal. The system’s eastern western and southern boundaries are assumed tobe no-flow boundaries. The southeastern boundary of the Nile at Nasser Lake and Dongolais a fixed head boundary, as is the northern Mediterranean coastline boundary. The westernboundary is a groundwater divide extending from Tibesti Mountains in the south and northwardsalong the 19° Meridian.75