Evaluation of the impact of Lake Nasser on the groundwater system in Toshka under future development scenarios, Western Desert, Egypt

Abstract

A MODFLOW model was applied to predict the current and future groundwater levels under different proposed development scenarios to identify the fluctuation of groundwater levels in the Nubian Sandstone Aquifer in Toshka Area (NSATA), based on changes of Lake Nasser water levels. The model was calibrated and verified then invoked to measure the responses of the Nubian aquifer characterized in water level decline for the next 100 years under six different management scenarios. The results revealed that the maximum predicted groundwater level decline after simulation period of 100 years reaches 25, 45, and 60 m when applying third, fifth, and sixth scenarios respectively, while in the fourth scenario, the groundwater level decline of 25 m has occurred after 7 years, which approves the importance of Lake Nasser in the aquifer recharge and consequently the development of Toshka region. On the other hand, applying the second scenario shows that when the water levels in Lake Nasser are less than 170 m, there will be reverse recharge from the aquifer to Lake Nasser. To conserve groundwater storage in NSATA for longer time, it is recommended to use water-saving agriculture techniques, to minimize the water used by applying new irrigation methods and to select plants and crops of low water consumption that have economic return.