Geochemical and isotopic evolution of groundwater in the Wadi Watir watershed, Sinai Peninsula, Egypt

Abstract

The Wadi Watir delta in the Wadi Watir watershed is a tourist area in the arid southeastern part of the Sinai Peninsula, Egypt, where development and growth of the community on the delta are constrained by the amount of groundwater that can be withdrawn sustainably. To effectively manage groundwater resources in the Wadi Watir delta, the origin of groundwater recharge, groundwater age, and changes in groundwater chemistry in the watershed needs to be understood. Mineral identification, rock chemistry, water chemistry, and the isotopes of hydrogen, oxygen, and carbon in groundwater were used to identify the sources, mixing, and ages of groundwater in the watershed and the chemical evolution of groundwater as it flows from the upland areas in the watershed to the developed areas at the Wadi Watir delta. Groundwater in the Wadi Watir watershed is primarily from recent recharge while groundwater salinity is controlled by mixing of chemically different waters and dissolution of minerals and salts in the aquifers. The El Shiekh Attia and Wadi El Ain areas in the upper Wadi Watir watershed have different recharge sources, either from recharge from other areas or from different storm events. The downgradient Main Channel area receives groundwater flow primarily from the El Shiekh Attia area. Groundwater in the Main Channel area is the primary source of groundwater supplying the aquifers of the Wadi Watir delta.

Groundwater recharge and salinization in the arid coastal plain aquifer of the Wadi Watir delta, Sinai, Egypt

“…2b), and this highly saline groundwater mainly originated from three sequential sea transgressions and regressions during the Pleistocene epoch (Abbas et al, 2004;Mabrouk and Nasr, 1997). The fresh groundwater in the Wadi Watir delta aquifers has been affected by mixing with this older deep saline groundwater that is approximately 2400e3600 years old (Eissa et al, 2013a). The Cl concentration and Cl/Br ratio data confirm that groundwater salinization in the Wadi Watir delta aquifers primarily originates from upwelling of a deep saline groundwater, which is caused by overpumping.…”

“…Model results were compared to and calibrated using observed seawater intrusion along the coast (identified using water chemistry and isotopic data), salinity increases in the main well field water, estimated groundwater recharge from an earlier study (Eissa et al, 2013a), and observed pumping data.…”

“…Model layers 1 to 12 correspond to layer A1 ( Fig. 7a; b), which contains the top three hydrostratigraphic units that are comprised of surficial alluvial deposits and sandy clay and have a hydraulic conductivity of 4 m/day (Eissa et al, 2013a). Layers 13 through 18 correspond to layer A2, which contains the fourth hydrostratigraphic unit beneath the land surface, which is comprised of sands and gravels and has a hydraulic conductivity of 11 m/day (El-Refaei, 1992).…”

Using hydrochemical and isotopic data to determine sources of recharge and groundwater evolution in an arid region: a case study in the upper–middle reaches of the Shule River basin, northwestern China

“…Understanding the origin and quality of groundwater is important for sustainable development and effective management of groundwater resources in arid regions (Eissa et al 2014) However, it is difficult to determine the amounts and sources of groundwater recharge using conventional water balance and/or hydraulics methods. Combined hydrogeochemical and isotopic studies may help elucidate both the sources of groundwater recharge and groundwater hydrogeochemical evolution processes (Bouchaou et al 2008;Gárfias et al 2010;Parisi et al 2011;Diaw et al 2012).…”

“…Common methods in this respect include the chloride mass balance method, use of hydrogeochemical tracers (minor or trace metals), and determination of isotopic composition. These techniques can be used to identify sources of groundwater and estimate the contribution of each member (Vanderzalm et al 2011;Al-Charideh and Hasan 2013;Schulz et al 2013;Eissa et al 2014). In arid regions, where there is little precipitation but strong evaporation, hydrogeochemical indicators and stable isotopic groundwater compositions can be effectively employed to trace recharge sources and quantify relative evaporation (Nativ et al 1997;Vanderzalm et al 2011;Yangui et al 2011;Singh et al 2012;Ahmed et al 2013;Lapworth et al 2013).…”