=Kwat Hewah= drains the eastern flanks of Gebel Dreb and the north flanks of G. Medarai. Its heads unite to form a series of channels in a small plain south-west of Eir Arib, and here it receives a contribution from Wadi Sherefa el Sharqi as mentioned above. As it passes Eir Arib, Kwat Hewah divides, part of its drainage curving round to the north to join that of Wadi Diqdib and Wadi Sherefa el Sharqi on its way to Wadi Shab, and the remainder going south-west to join the Wadi Medarai. From the head of Kwat Hewah there is said to be an easy pass into the Wadi el Krim, a tributary of Wadi Feqoh. =Wadi Ibib=, which drains the eastern slopes of Gebels Medarai, Abu Hireiq, and Abu Hodeid, and the eastern and northern faces of Gebels Soaorib, Adar Qaqa, Leqaq, Um Seleim, Qidmib, Orgem, and Um Bishtit, as well as Gebel Hamra Dom and the smaller hills south of it, is formed by the union of the Wadis Hasium and Medarai, a little east of Gebel Um Rasein, and enters the sea at Mersa Shab. It has a drainage basin of about 1,800 square kilometres. Including Wadi Hasium, which is simply the upper portion of Ibib, its total length along its main channel is slightly over one hundred kilometres. Its principal tributaries are the Wadis Shinai, Abu Hodeid, Abu Hireiq, Medarai, Soaorib, and Um Bishtit. =Wadi Hasium=, which forms the upper portion of Wadi Ibib, originates on the main watershed in about latitude 22° 10′ and longitude 35° 15′; a pass leads from its head on to a stony plain, whence a track leads to Miti Kwan, a tributary of Wadi Alaqi. Near its head, Wadi Hasium contains a small well called =Bir Kagog=. A few kilometres further down, the short =Wadi Mantil Hasium=, draining the western face of Gebel Adar Qaqa, enters from the east, while the =Wadi Hilwit Hasium=, draining the mountain of the same name and containing a galt near its head, joins Wadi Hasium from the west. Continuing its course northward past the mountains of Adar Qaqa and Leqaq, Wadi Hasium enters an extensive sandy plain, open to the north, bounded on the west by the mountains of Abu Hodeid and Um Rasein, on the south by those of Leqaq and Um Seleim, and on the east by those of Qidmib and Orgem. This plain, which averages fifteen kilometres in width, is broken by low hills, the principal of which, Gebel Hamra Tit, Kulet Meiqrum, and Kulet Tinasal, rise to considerable heights. Hasium courses slightly east of north near the western edge of this plain to near Gebel Um Rasein, then curves to the east across it, receiving the Wadi Medarai and becoming Wadi Ibib. In its northward course through the plain, Wadi Hasium receives a number of important tributaries from the western mountains, besides a few smaller feeders from the mountains to the south and from the hills on the plain. These may be briefly described in order.