GROUNDWATER POTENTIALS AND CHARACTERISTICS OF EL-MOGHRA AQUIFER IN THE VICINITY OF QATTARA DEPRESSION

The study area lies between Wadi El Natrun (-23 m)  in the east and Qattara Depression (-134 m) in the west of the  Northern Western Desert of Egypt. It attains an area of about 150000 km² and is dominated by a major aquifer unit of clastic facies, namely El-Moghra Aquifer. Such aquifer, has a variable saturated thickness between 100 to 300 m, and is defined to be of Lower Miocene age and of continental to marine depositional environments. Many trials have been made to extract groundwater for irrigation purpose, especially in the eastern portion near Wadi El-Natrun where water salinity is less than 1000 ppm. While in the western portion near Qattara Depression, the water salinity is more than 10,000 ppm, and the groundwater of El-Moghra Aquifer is used widely for oil industry. Actually, the groundwater of more than 70% of the study area is still unexplored.
                     The main objectives of the present work are to focus on the configuration of El-Moghra Aquifer in the study area including its physical, chemical and hydraulic properties through the investigation of about 200 wells. The assessment of aquifer potentials as well as its lateral and vertical changes is one of the main targets of the present study. The aquifer in the area to the east of Longitude 29^o 00' 00'' is proved to be under unconfined condition and is evidently connected with the Nile Delta Aquifer, while that to the west of Longitude 29^o 00' 00'' is confined and subjected to upward leakage from younger and deeper aquifers. The pumping tests (9 experiments) carried out in the area indicate highly productive aquifer in Wadi El-Farigh (unconfined aquifer) with transmissivity ranging between 720 and 6500 m²/day, and low productive aquifer west of El-Moghra Depression (confined aquifer) with transmissivity ranging between 61 and 600 m²/day. Changes of water chemistry due to variation in the depositional environment and source of recharge have also been assessed and genetically classified.  The water salinity–water level relationship has revealed a very coherent picture about the fresh water–saline water interface, as well as delineation of promising areas within the study area for different purposes of development.  The area to the east of water level 27 m below sea level has water salinity less than 2000 ppm covering an area of about 375000 hectare, within a distance of about 75 km, which is suitable for agriculture and domestic water uses. Additional area to the west of water level -27 m is about 488000 hectare having salinity between 2000 and 5000 ppm can be used for cultivation of salt tolerant crops. The water quality data have been also used for the differentiation between the continental and marine facies of the aquifer, as well as for the detection of the recharge sources and flow direction.