Hydrochemical and isotopic study of groundwater in Wadi El-Natrun, Western Desert, Egypt: Implication for salinization processes

Ground-water samples were collected from 10 wells in Wadi El-Natrun, Western Desert, Egypt, over four consecutive years. The combination of isotopic composition and hydrochemical analyses was used to identify the origin of the groundwater and determine recharging sources as well as to discuss the mechanism controlling hydrochemical variation among wells. Two water sources, a relatively recent/shallow aquifer recharged from Nile River water and a deep/old aquifer (i.e. the Nubian sandstone aquifer system [NSAS]), are identified from isotopic and geographical relationships and the correlation between isotopic data and bicarbonate concentration. It was found that Nile Delta aquifer water was likely supplied as groundwater flows from the southeast and that old water (paleowater) was supplied upward from deeper layers. Some wells show relatively greater variation in concentration as well as in hydrogen isotope composition during the four-year study. Based on the relationship between concentration and isotope composition the variation was not caused by seawater intrusion or salt dissolution but by intensive water loss. The water loss is not directly due to evaporation or suction but is considered to proceed indirectly within the soil.