Use of groundwater in nile alluvial soils and their fringes

Abstract

Groundwater reportedly provides drinking water to at least 50% of the global population and accounts for 43% of all water used for irrigation. Food production requires the largest quantities of water, with groundwater resources providing more than 40% of all water used globally for irrigated agriculture. According to the Egyptian Ministry of Irrigation and Public Works the annual water resources in Egypt depend mainly on the Nile water (55.5 BCM), 5.5 BCM groundwater, and 1.3 BCM of rain water that falls on the agricultural land in the Delta. Most of the groundwater in Egypt is non-renewable except for the shallow groundwater in the Nile valley and Delta lands and its fringes in addition to some depression sources and oasis like Wadi El-Natrun in the west Delta (the Valley of Sodium salts) and Siwa oasis south of the northwest coast of Mediterranean. The main aquifers are generally formed of granular rocks (sand and gravel) or fissured limestone and rocks. The deep-lying aquifers systems is comprised of the regional Nubian Sandstone aquifer System, occupying much of the area of Egypt. The thickness of the sediments varies from a few hundred meters in the south, to 4,000 m west of Abu Mongar. Carbonate Aquifers occupy at least 50% of Egypt. The Moghra aquifer system has a broad geographical distribution in the region west of the Nile Delta and south of the Qattara depression. The Nile valley and Delta aquifer are the most productive, containing around 200 × 103 million m3 of water that is renewable by seepage from the Nile river irrigation systems. The thickness of this aquifer decreases from 300 m at Sohag Governorate in Upper Egypt to few meters near Great Cairo (Cairo, Giza, and Qalyubia governorates) and also in the south near Aswan. The coastal aquifer lies 35 km from the seashore, 45 km north of Cairo and is recharged mainly from rainwater and from high-pressure water in the Nubian Sandstone aquifer. Rose basement rock has the same characteristics as the Carbonate aquifer but is difficult to explore since it is very deep (1,200–2,000 m depth). The main problem of the Siwa oasis depression is the poor drainage and lack of a drainage outlet, thus causing water logging. The second problem is the shallow and under pressure groundwater that pops up to the ground creating wetlands. In Wadi-El-Natrun depression, the water table depth is almost of 3–5 m but has a high concentration in sodium carbonates and bi-carbonates. This type of composition is completely different in other delta fringes such as in Nubaria (west delta) or in Salhia (east delta) in which it ranges between 30 and 60 m with a medium quality of maximum salinity of 2,000 ppm. Most of these areas in Nubaria or Salhia are irrigated with Nile water through El-Nasr canal in Nubaria and Salhia canal in the east Delta, but the wells of groundwater are stationed as stand-by or alternative resources when Nile irrigation water is not sufficient or in case of a delay in its delivery.