Middle East Journal of Applied Sciences ISSN 2077-4613 Volume : 08 | Issue :03 |July-Sept.| 2018 Pages: 939-956 Corresponding Author: Ehab Zaghlool, Hydrogeochemistry Dept., Division of Water Resources and Arid Land, Desert Research Center, 1 Mathaf Al Mataria St., Mataria, P.O.B. 11753, Cairo, Egypt. E. mail: ezaghlooldrc@yahoo.com 939 Integrated Geochemical Indicators and Geostatistics to Asses Processes Governing Groundwater Quality in Principal Aquifers, South Sinai, Egypt Ehab Zaghlool and Mustafa Eissa Hydrogeochemistry Dept., Division of Water Resources and Arid Land, Desert Research Center, 1 Mathaf Al Mataria St., Mataria, P.O.B. 11753, Cairo, Egypt Received: 26 June 2018 / Accepted: 29 August 2018 / Publication date: 15 Sept. 2018 ABSTRACT The groundwater system in the principal aquifers situated in the Southern Sinai was regionally investigated, using hydrochemical tools and geostatistical technique to evaluate the recharge sources and salinization origins which consider the main constraint for sustainable development in such an arid region. The environmental stable isotopes (δ 18 O and δ 2 H), groundwater salinity, conservative ions (Cl and Br), ion ratios and the sea water mixing index (SWMI) were utilized to identify the salinization mechanism and to delineate the recharge for different aquifers (Quaternary, Miocene, U. Cretaceous, L. Cretaceous and Precambrian) situated in the upstream watersheds and along the coastal regions. The regional study depends on four hundred and sixty-eight groundwater samples tapping the main aquifers. The geochemical data have been analyzed statistically to estimate the seawater mixing index (SWMI) in order to delineate the deteriorated aquifer zones. The environmental stable isotopes confirm the upstream of Gharandal, Watir, Dahab basins and Saint Catharine areas receives considerable amount of the annual precipitation that could be managed for sustainable development. The hydrochemical ion ratios and the SWMI values give good insights for aquifer salinization, where; mixing with seawater intrusion in the downstream coastal aquifers, leaching processes of minerals in the aquifer matrix, evaporation processes are considered the main sources for aquifer deterioration. The hydrogeochemistry shows the injection of high saline water comes from the desalination plant deteriorates the coastal Miocene aquifer located in Sharm El Shiekh and Nabaq areas. Keywords: Groundwater chemistry, Statistics, rCl/rBr, Sable isotopes, South Sinai Peninsula Introduction The South Sinai Peninsula is located in the coastal arid region, where the groundwater recharge is limited and seawater intrusion threatens the groundwater quality due to the over withdrawal. The groundwater is the main source of drinking and potable uses for about 177,900 inhabitants (South Sinai, 2012). Groundwater salinization is an environmental global phenomenon that affects many different aspects of our life (Williams, 2001). The groundwater quality deterioration is considered one of the most important challenges facing the sustainable development strategies in arid and semiarid areas. In the coastal arid aquifers, groundwater salinization processes mainly arisen from seawater mixing, geogenic sources, evaporation, and dissolution as well as the anthropogenic activity such as over-exploitation and rejecting brine deeper into aquifer saturated zone (S´anchez-Martos et al., 2002; Indu et al., 2013). Recently, the environmental stable isotope in conjunction with conservative ions rCl/rBr as well as other geostatistical and geochemical tools have been used to explain the factors deteriorate the groundwater quality (Alcala and Custodio, 2008; DeMontety et al., 2008; Carol et al., 2009; Ben Hamouda et al., 2010; Han et al., 2011). The Cl/Br ratio gives good insights related to the groundwater contamination and mixing due to its constant value from different end members. The value of rCl/rBr can not significantly modified by the anthropogenic or the physical processes taking place in soil including dilution, evaporation, transpiration (Samantara et al., 2015). Stable isotopes (δ 18 O and δ 2 H) are used to identify recharge source of groundwater (Clark and Fritz, 1997; Mook, 2001) and the mixing with seawater in coastal aquifers (Leduc et al., 2007). The previous studies (Mazor et al.,1973; Gat and Issar, 1974; Tantawi et al. 1998; Abd El Samie and Sadek, 2001;