PRELIMINARY INTERPRETATIONS OF ISOTOPE AND CHEMICAL DATA OF SAMPLES FROM THE NUBIAN SANDSTONE AND ADJACENT AQUIFERS IN EGYPT

The importance of studying groundwater in arid regions has increased in recent decades due to larger human populations in desert areas. The Nubian Sandstone Aquifer System of northeastern Africa is a case in point as one of the largest confined aquifer systems in the world with several nations relying on this water resource (Egypt, Libya, Sudan and Chad). Groundwater has been identified as the biggest and in some cases the only future source of water to meet growing demands and the development goals of each Nubian Sandstone Aquifer country, and evidence shows that massive volumes of groundwater are still potentially available. This study focuses on select Nubian aquifer derived groundwater samples and other shallow and surface water bodies from Egypt using chemical and isotopic characteristics.

The isotopic composition of groundwater samples from wells tapping the Nubian Sandstone Aquifer in the Eastern Desert (-49.5‰ to -58.2 ‰ for δD and -5.6‰ to -7.9‰ for δ¹⁸O respectively) is enriched compared to the samples from wells in the Western Desert (-72.3‰ to -82.7‰ for δD and -9.4‰ to -11.1‰ for δ¹⁸O respectively). This might be due to the influence of recharge from modern precipitation and anthropogenic activities. Groundwater samples from the Quaternary aquifer in the Eastern Desert can be separated into those influenced by irrigation canals in hydraulic communication with the Nile River and those that are not in contact with surface water. The former has a range of isotope values of -4.1‰ to -29.6 ‰ for δD and 1.1‰ to -3.4‰ for δ¹⁸O respectively, and the latter has the range of 24.7‰ to 21.8 ‰ for δD and 4.0‰ to 3.3‰ for δ¹⁸O respectively. The implications of chemical and isotopic data will be discussed in a regional context.