ABSTRACT
ABSTRACT: To simulate the response of the Nubian Sandstone Aquifer in the eastern Sahara to climate changes during the last 25,000 years, and modern pumping, a regional 3D groundwater flow model was developed and calibrated under steady state and transient conditions. Telescoping meshes were developed in this regional model to include the local details of development areas. The data for this model are held in a GIS database to allow for its implementation in different modeling systems. The simulations using finite element numerical modeling confirm that groundwater in this aquifer is likely to have originated from infiltration during the wet periods of approximately 20-25 ka BP and 5-10 ka BP. Modern recharge of groundwater due to regional groundwater flow from more humid areas to the south is highly unlikely. The model also indicates that the Nubian Aquifer System is a fossil aquifer system, which has been in an unsteady state condition since the end of the last wet period, approximately 5000 years ago. The telescoping modeling approach offers a good solution for the insufficient boundary conditions in the development areas. The simulation results of the large scale model, with telescoping meshes to account for current abstraction, demonstrates that the groundwater reserves of the Nubian Sandstone Aquifer in Egypt and Libya are being mined. By expanding the presently established well fields to their full capacity by year 2020, the water-levels will continuously decline and may fall below economic levels of abstraction.
