that section of the Nile River between Nimule near the Uganda border and Malakāl in south-central Sudan. Below Nimule the river flows northward over the Fula Rapids, past Juba (the head of navigation), and through as-Sudd, an enormous, papyrus-choked swamp where half its water is lost. It receives the Baḥr al-Ghazāl at Lake No and then turns east to join with the Sobat River of western Ethiopia above Malakāl, thereafter forming the White Nile. Much of the river's 594-mile (956-kilometre) course winds between walls of high papyrus, reeds, and elephant grass, which, during the dry season, provide grazing for cattle.