USE OF ENVIRONMENTAL ISOTOPES AND HYDROCHEMISTRY AS INDICATORS FOR THE ORIGIN OF GROUNDWATER RESOURCES IN EL-DABAA AREA, NORTHWESTERN COASTAL ZONE OF EGYPT

The El-Dabaa area is located on the northwestern coastal zone of Egypt and is considered to be one of the most important regions for land re clamation and agriculture. In addition, it has been selected as a pote ntial site for constructing Egypt's first nuclear power plant. In Apri l 1989, 14 groundwater samples were collected from the area as well as collecting samples from the Mediterranean sea and from local rainwate r. These samples were subjected to chemical and environmental isotope analyses. The results of the analyses for stable isotopes (oxygen-18 a nd deuterium) indicate that the main recharge source of the groundwate r in El-Dabaa is the local precipitation during the rainy season, Vari ation of the environmental tritium content as well as in the chemical composition of both major cations (Na,K,Ca,Mg) and major anions (Cl,SO 4,HCO3) between different groundwaters in the studied area reflect the high degree of inhomogeneity of the aquifer and different recharging conditions due to permeability of the water bearing formation. The che mical water type of the El-Dabaa groundwater is sodium sulphate (Na2SO 4) and the SAR values illustrate the suitability of these groundwaters for agricultural purposes.