USE OF SOLUTE CHEMISTRY AND ISOTOPES TO IDENTIFY SOURCES OF GROUNDWATER RECHARGE IN THE NILE AQUIFER SYSTEM, UPPER EGYPT

Twelve ground-water samples were collected in the Nag Hammadi area, fr om Quaternary and Plio-Pleistocene age aquifers, The isotopic data ind icate that the main recharge source of the Quaternary aquifer is the r ecent River Nile water, which is isotopically enriched from evaporatio n in Lake Nasser, Sources of recharge to the Plio-Pleistocene aquifer are: (1) Old Nile water depleted in isotope composition, which was tra pped in the geological formation, characterized by low permeability an d clay lenses prior to the construction of the Aswan High Dam; and (2) The leakage of palaeo water from the deep aquifer system through main faults which bisect the study area, The variation in the chemistry of ground water is thought to be related to mixing between the different water sources and leaching of fertilizers in the newly reclaimed area s in the desert fringes.