Gharandal watershed (882 Km(2)) is part of South Sinai, which represent a remote arid area. Groundwater of the Quaternary aquifer, represents the only water resources for drinking, irrigation and domestic use in this watershed. An integrated approach was used to identifying the geochemical processes controlling the groundwater quality and characterize their evolution along the flow path, depending on the hydrogeochemical and isotopic data. The stable isotopes (delta O-18 and delta H-2) data elucidate that the studied aquifer is ensured by recent recharge from the local rains. The hydrogeochemical results outline that evaporation, rock-water interaction (particularly dissolution of carbonates and evaporates minerals in aquifer matrix) and the cation exchange, are the main geochemical processes accountable for increasing salinity and the evolution of the groundwater along the flow path. The hydroeochemical fades evolves from Mg-Na-SO4-HCO3 at recharge area into Ca-Na-SO4-Cl at the middle parts of the main channel and finally Na-Ca-Cl-SO4 in the downstream of the studied watershed. Geochemical modeling (NETPATH) indicating upgrading in the Quaternary aquifer water from the upstream to produce groundwater at downstream portion. The current study recommended that the Quaternary aquifer should be managed in a sustainable way by not pumping more than the recharged on an average annual basis.