Numerical modeling of seawater intrusion in karstic aquifer, Northwestern Coast of Egypt

Abstract

The growing population and increasing of the urbanization activities at the Egyptian coastal areas create a great demand on groundwater. El Negila which is located on the Northwestern coast of Egypt is of great environmental, economic, and social importance, so the sustainable management and preservation of the groundwater quantity and quality is imperative. Such task can be addressed through modeling tools that take into account both the human impacts and the effects of climate changes on the hydrogeological system. A variable-density flow model (SEAWAT) had been used to investigate the extent of the seawater intrusion the study area, and to introduce an effective management policy for sustainable development of the groundwater system. An attempt had been made for model calibration; based on adjusting the hydraulic head of the hydrogeological system with respect to the lineaments frequency in the study area. The calibrated numerical model showed the limited extent of the seawater intrusion in the study area under current recharge and abstraction conditions, in addition to that, the model was validated using hydrochemical and stable isotopic data. The aquifer response to different stressing pumping scenario has been tested and predicted up to the year 2022. Furthermore, the impact of rising the seawater level as a result of rapid climatic change was assessed, with pumping stress of the second scenario. It was concluded that the tableland area acts as recharge source and providing an opportunity of recharging the karstic aquifer in the study area especially through the lineaments. The extent of seawater intrusion in the study area for the karstic aquifer is limited, and would increase under the induced activities of pumping as well as seawater rise conditions. A range of withdrawal rate from the study area was recommended to avoid more invasions from seawater.