Hydrogeological Evaluation of Massive Salty Lagoons, (Case Study: Qattara Depression)
Abstract
At the beginning of the 20th century, several studies were performed to deliver the Mediterranean Sea water to the Qattara Depression through a canal for hydropower generation by utilizing the difference in the water levels. Main objectives of the current study are to: a) study the hydrogeological conditions of Qattara as a drainage lagoon for the Delta, And b) study the effect of saltwater lagoon on the Nile Delta, and the groundwater reservoir. The study methodology has been performed utilizing the recent tools, of analysis, that had not been available for the previous studies of the project such as; efficient numerical models, geographic information system (GIS), and Digital Elevation Models (DEM). The effect of salinity on evaporation, from the lagoon, was calculated. A number of twenty one boreholes, with average depth of 3900 m, were employed to construct the geological stratification. Hydraulic conductivity values and groundwater levels have been collected from the available boreholes and deep exploratory wells drilled by the oil companies. Mass balance of the lagoon saltwater was performed, every separate year during a period of 50 years.
Density dependent model (SEAWAT) via MODFLOW has been employed for duration of fifty years. The simulation was done every separate year. The simulation was repeated for different water filling levels, and when having several well fields between the lagoon and the Nile Delta. The wells screen was assumed in the Moghra, the limestone, and the deep sandstone aquifers. The results revealed that the lagoon does not affect the Nile Delta drainage efficiency. The lagoon accumulated salinity does not reach the Nile Delta. The study, also, revealed that the effect of the lagoon salinity, on the lower sandstone reservoir, is minor because of the confining shale layer and the salinity diffusion does not reach the Nile Delta. The study, also, revealed that the effect of the lagoon salinity, on the lower sandstone reservoir, is minor because of the confining shale layer and the salinity does not diffusion horizontally towards the Nile Delta.