Isotope techniques in the study of groundwater in the eastern Nile Delta and the transport of pollution from drainage water into Lake Manzala, Egypt

Seventy-two water samples were collected from eastern Nile Delta groundwater, Lake Manzala, surface water and main drainage stations during 1993-1995. The water samples were analysed for major, minor and tracer elements and for oxygen-18 and deuterium. The hydrochemical studies indicate that the groundwater of the eastern Delta can be classified into three groups of low, medium and high salinity. The fresh water is mostly encountered near the Nile and near irrigation canals in the south. The brackish and saline water occurs near the Bitter Lakes, the Gulf of Suez and the Mediterranean Sea. The salinity is attributed to the leaching of terrestrial salts and to seawater intrusion. Nitrate concentration was found to be relatively high because of extensive fertilizer use. In general, the stable isotope contents of groundwater differ widely depending upon the contribution of each recharging source (present Nile, old Nile, precipitation, seawater intrusion and possibly palaeowater contribution in some localized areas). Investigation of Lake Manzala revealed that the water salinity is rather inhomogeneous, and high concentrations of trace elements were detected, which could be attributed to drainage water discharging into the lake. A stable isotope balance was developed to estimate seepage and evaporation from the lake. (author)