Surdo Egyptian ] IRRIGATION SCHEMES Anglo -121 materials and the increased cost of labour, further con sideration will be necessary to estimate the actual cost under existing circumstances. The cost of the main canal, to supply sufficient water for the irrigation of 300,000 acres or more, would be considerably above £E . 580,000 .

The White Nile scheme is intended to control the waters of that river for the benefit of Egypt. It com prises a reservoir dam and a spill-water channel, the former being of the more immediate importance.

The dam, which would be built at Jebel el-Auli , would be capable of holding up an adequate summer supply for Egypt, and , if raised to a sufficient height, could impound, when necessary, excessive flood waters, for subsequent release into the main channel of the Nile . The reservoir thus formed would coincide with the White Nile valley behind the dam for at least as far up the river as Řenk . Under normal conditions this section of the river already acts in each flood season as a reservoir for a distance of about 250 miles above Khartum . The flood in the Blue Nile comes down from the Abyssinian mountains early in the summer and, owing to the steep gradient of the river bed, has such a force that, when it meets the more sluggish White Nile, it actually dams back the latter, andmonopolises the channel below Khartum for some distance. Then , as the Blue Nile begins to fall, the pent-up flood of the White Nile breaks in and often produces a kind of second flood in Egypt . This impounding of the waters of the White Nilewhen the Blue Nile is in flood is shown by the discharges of the former river at El Dueim . During May andJune the discharges atEl Dueim and at Taufikia are about equal. As the Blue Nile rises the discharge at El Dueim first remains stationary, whilst the river con tinues to rise, and then in August diminishes as the Blue Nile floodstrengthens. In October the discharge increases rapidly as the flood effect of the Blue Nile passes.