GROUNDWATER RECHARGE AND SEAWATER INTRUSION OF THE QUATERNARY COASTAL PLAIN AQUIFER IN WADI WATIR DELTA, SINAI, EGYPT

It is essential to know the average annual groundwater recharge of the aquifers in Wadi Watir Delta of Egypt in order to better manage the groundwater resources in a sustainable way in the delta. The delta is a tourist area in the arid southeastern part of the Sinai Peninsula, where development is constrained by the amount of groundwater that can be developed in a sustainable manner. The study area consists of alluvial and sandstone aquifers, which are underlain by impermeable Precambrian basement. The scarcity of rainfall during the last decade, combined with high pumping rates, has resulted in the degradation of water quality in the main supply wells along the mountain front and along the coast requiring a reduction in groundwater production. A three-dimensional groundwater flow model (MODFLOW) coupled with a variable-density flow and transport model (SEAWAT) were developed and calibrated using groundwater level changes and chloride concentration to simulate groundwater recharge, upwelling of saline water beneath the well field, and seawater intrusion along the coast for different pumping scenarios. Water chemistry and stable isotope data including ^87/86Sr, δ³⁷Cl and δ⁸¹Br isotopes were utilized to calculate the percent of seawater mixing in groundwater along the coast.