Hydrogeochemical and Environmental Isotopic Evaluation

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"Water resources in Ain El Sukhna area play an important role in providing a source of potable water for land use and construction of new settlements. Hydrogeology, geochemistry and environmental isotopes were integrated in this study to assess groundwater resources recharging. The structural setting of the study area affected to a great extent the hydrogeological regime of the aquifer systems of the study area and resulted in the initiation of fracture or flowing springs. This same setting, especially the deep-seated faults, was responsible for the hydrochemical and isotopic composition of the groundwater of the study area. The water level at the area of the Miocene aquifer in the northern parts of the study area is higher than that of the Quaternary aquifer areas. This means that, the Miocene aquifer is the main source of recharge to the Quaternary aquifer. The main flow of water in the study area is directed from west, northwest and south to east and southeast. This gave evidence that the main recharge is coming from the upland areas, which lead to rainfall water storage in the sediments of these areas. Chemical measurements on groundwater indicate significant variations in solute content. Its lowest values were detected at delta W. Ghaweibba and gradually increase toward the Gulf shore. The general trend of increasing salinity is directed eastward. All samples coincide with the prevalence of Cl-Na as dominant ions and one salt assemblage (NaCl, MgCl2, MgSO4, CaSO4, and Ca (HCO3)2). The increase in Ca2+ ions concentration is mainly attributed to the saturation conditions in most water samples with respect to calcite and dolomite minerals. The isotopic results of O-18, D, C-13 and C-14 dating reveal three distinct recharge sources replenishing the Quaternary aquifer with different mixing ratios: 1. Paleowater from older formation (the Nubian Sandstone aquifer) seeping eastward via geological structures in Gebel El Galala El Bahariya represented by the issuing water samples (this water is denoted by isotopic depletion, old age (11,240 yr. B.P), and relatively high salt content), 2. Groundwater of Ain El Sukhna thermal flowing water with less isotopic depletion and age determination of 7000 yr. B.P and, 3. Recent recharge by infiltration of flash floods water after rainstorms over the hydrographic basins replenishes the aquifers directly on a short travel time. This water is isotopically enriched and has the signature of the Mediterranean Sea precipitation. C-13 measurements provided another confirmation of the diversity of recharge sources, where the issued water samples flow through aquifers less in carbonate minerals content (depleted in C-13). Whereas the groundwater samples are in contact with carbonate minerals cause a relative enrichment in C-13 isotopes. Marine residual deposits from the sequential regression and transgression of sea water are the main source of mineralization which is evidently observed from the low difference in isotopes with respect to salt content."



case study, water resources