Centre-pivot irrigation in Sahara, satellite image. Each circular shape in the desert is a centre-pivot irrigation field that is just under a kilometre across. This area is in the Sahara Desert in southern Egypt. With no surface water in this region, wells pump underground water to rotating sprinklers from the huge Nubian Sandstone aquifer under the desert. Image data obtained by the Landsat 8 satellite on 22 May 2013.