Sustainable Agricultural Groundwater Management for New Reclaimed Areas in Farafra Oasis, Western Desert of Egypt

Abstract

Sustainable groundwater management is an important practice of water resources engineering, especially, in case of deserts and oases where there is no source of surface water and precipitation rarely occurs. The importance increases when the only source of groundwater is a nonrenewable aquifer. This is the case of new reclaimed areas in Farafra Oasis, Western Desert of Egypt. The only source of irrigation water is groundwater extracted from the nonrenewable Nubian Sandstone Aquifer (NSA). There is a great agricultural development in Farafra Oasis as a part of the 1.5 million feddan mega project. Agricultural development, for new areas, is a must for Egypt to fulfil the increasing food demand accompanied with the increasing population growth rate. However, this development has to consider the sustainability of groundwater usage along with the social, economic, and national security aspects. Groundwater extraction rate from NSA has increased. As it is a nonrenewable aquifer, there is no groundwater recharge. Consequently, the groundwater potentiometric level (GPL) decreases with time. The traditional sustainability concept of safe yield or discharge equals recharge is not applicable on such cases. The Ministry of Water Resources and Irrigation (MWRI) of Egypt set the groundwater sustainability criteria for groundwater-dependent new reclaimed areas in Farafra Oasis, Western Desert of Egypt. Both duration and economic lifting depth, have been considered. This paper presents groundwater sustainability assessment for extraction rates, Qwell = -1000, -2000, -3000, -4000, and -5000 m3 /d, to obtain the most beneficial sustainable extraction rate according to the MWRI sustainability criteria. A new groundwater-dependent reclaimed area of 10,000 feddan in Sahl Baraka, Farafra oasis, was taken as a case study area. GIS functions were used to obtain the values of unknown data and develop the initial groundwater potentiometric map. MODFLOW was used to construct a numerical model for groundwater extraction rate simulation for the case study area. This model was calibrated and used to obtain the depression cone drawdown (DCD) associated with different extraction rates. All NSA regional drawdown rates at Farafra oasis were considered. Benefit –Deficit analysis for duration and economic lifting depth criteria are presented and show that the extraction rate of Qwell = -3000 m3 /d is the most beneficial sustainable extraction rate according to the MWRI adopted sustainability criteria.