Sedimentological Society of Egypt

THE WATER CHEMISTRY OF THE QUATERNARY AQUIFER IN THE SOUTH El-QAA PLAIN AREA, SINAI, EGY PT
SALAH, A. M. ZEID , ¹MEDHAT A. EL BIHERY AND ¹ABD ELAAL. Z. AMR
Geology Department ,Faculty of Sciences,Al Azhar University, Assuit Branch;
¹Water Resource Research Institute, El Kanater El Khairiya

The Quaternary aquifer of El-Qaa plain is situated in a secondary rift basin that accompanies the main rift system in the Gulf of Suez. It is bounded on the east by high mountains of Precambrian crystalline basement rocks. The eastern margin of the aquifer consists of sandy gravel and gravelly sand typical for alluvial fan facies of high hydraulic conductivity (about 50m/day). The seaside margin is occupied by parallic facies, mainly of limestone, coral reefs and clay alternating with continental sabkha and alluvial deposits of lower hydraulic conductivity (about 5m/day). The direction of groundwater flow is mainly from northeast to the Gulf of Suez.
The hydrochemical aspects for the groundwater of the area south of El-Qaa plain are discussed based on the chemical analyses of 6 groundwater samples (4 wells and 2 springs), The major ions and some trace elements are detected.
The geographical distribution of the groundwater salinities indicates that the eastern part of’ the Quaternary aquifer shows low salinity value (632.43 ppm) due to the high recharge rate from the eastern basement rocks and the continuous dilution process with fresh recharged water. While the western part shows high salinity value, (34552.94 ppm) which is attributed to the leaching of the Miocene saline evaporites and seawater intrusion inland.
The main water types are sodium chloride and magnesium chloride for the obtained groundwater by wells, and magnesium sulphate and calcium bicarbonate for that obtained by springs.
Genetically, the groundwater is of meteoric water genesis of Na₂SO₄ water type (wells 4 and 6) and of NaHCO₃ water type (well 5), and others are of marine genesis of CaCl₂ water type (wells 1,2 and 3). The water of well 4 and the two springs (5 and 6) is fresh water, while that of wells 2 and 3 is moderately saline water. The groundwater well 1 reflects seawater salinity, due to seawater invasion.
The groundwater of the two springs (5 and 6) are good for irrigation, while that of wells 2,3&4 are doubtful and that of well 1 is unsuitable for irrigation purposes.
The concentrations of trace elements (Fe²⁺, Mn²⁺, Zn⁴⁺, Cu²⁺,Cd²⁺, Pb²⁺,Ni³⁺,Cr³⁺, As²⁺,Ba²⁺ and Se²⁺) revealed that the groundwater wells and the two springs are suitable for drinking and irrigation purposes. However the concentration of Fe²⁺ in wells 3 and 4 exceeds the recommended limit for drinking and require treatment.