Use of Environmental Isotopes and Hydrochemistry for Determination of Recharge Sources and Fossil Water Contribution in the Groundwater Aquifers of West Maghagha Area,Upper Egypt

Abstract

The present work has been devoted to investigate the sources of recharge, renewability, fossil water contribution and salinity evolution of the groundwater resources in the western zones of Maghagha , El Minia Governate , Upper Egypt. A complementary approach integrating, the hydrochemical and isotopic techniques with the hydrogeological investigation has been applied to achieve the objectives of this work. The results of isotopic analysis (Oxygen-18, Deuterium and Tritium and Carbon-14) of the collected samples have been used to infer the rechargability and renewability. The Quaternary groundwater aquifer is renewably recharged from Nile water system, it is hydraulically connected to Eocene aquifer which gets its recharge from two sources: - the present day Nile water from irrigation canals and the paleowater of fossil origin that upward leaks through joints and fractures from the deep seated Nubian sandstone. The relative contribution of the paleowater increases westward, it ranges from 26% to 100% and becomes dominant and solely exists at about 40 km westward. The groundwater is renewable to the east and renewability decreases westward. The radiocarbon dating indicates that the paleowater in the study area has a C14 age equal about 10120 ybp , the samples that get a mixed recharge from Nubian sandstone paleowater with present day Nile water has C14 ages (less than 10120 ybp) proportional to the mixing ratio. The results of analysis of major ions and trace elements of 43 groundwater samples have been treated, processed and analyzed using Statistical Techniques, GIS methodology, Standards Graphs , Cross Plots, Softwares (eg SPSS, Solminique, …). The data of the chemical analysis have been used to determine the chemical characteristics and salinization processes of the groundwater under study and to evaluate the hazards of its use for drinking and irrigation. The distribution of ionic species, the hydrochemical facies and the salts combinations reflected a high stage of salinity evolution for the groundwater under study. This is developed under effects of major salinization processes including: halite and carbonates dissolution, cation exchange as well as mixing the less saline recent recharge with saline paleowater of deep origin. The suitability of using the groundwater under study for irrigation and drinking purposes has been evaluated by comparing the concentration of ionic species in the samples with that recommended by reference standard limits; also by calculating a number of indexes using ionic concentrations either separate or integrative collective. About 50% and 35% of the samples are of good suitability for irrigation and drinking uses, respectively.