Solute transport and geochemical modeling of the coastal quaternary aquifer, Delta Dahab Basin, South Sinai, Egypt

The wadi dahab delta is in a dry, arid coastal zone within Egypt's south Sinai Peninsula's eastern portion. The primary water source is the Quaternary coastal alluvial aquifer. The groundwater salinity varies from 890 to 8213 mg/L, with a mean value of 3417 mg/L. The dissolved major ions have been used to calculate the seawater mixing index (SWMI) using a linear equation that discriminates the groundwater mostly affected by water–rock interaction (SWMI 1 >) and other samples mixed with Seawater (SWMI < 1). The isotopic composition of groundwater for specifically chosen groundwater samples ranges from −0.645‰ to +5.212‰ for δ¹⁸O and from − 9.582‰ to + 22.778‰ for δ²H, where the seawater represented by a Red Sea water sample (δ¹⁸O + 1.64‰ − δ²H + 9.80‰) and reject brine water are considerably enriched the isotopic groundwater values. The geochemical NETPATH model constrained by the dissolved significant ions, isotopes, and the rock aquifer forming minerals as phases indicate the mixing percent with the seawater ranges from 9% to 97% of seawater from 91% to 3% of original recharge water. According to the SEAWAT 3-D flow models, seawater has penetrated the Northeastern Dahab delta aquifer, with the intrusion zone extending 1500 m inland. The salt dissolution, upwelling of saline water, recharge from the upstream mountain block, and seawater encroachment are the primary aspects contributing to the deterioration of groundwater quality. These findings may have significance for effective groundwater withdrawal management in arid locations worldwide with similar hydrogeological systems.