Engineering Wonders of the World
Volume I

THE NILE DAMS AND THE ASSOUAN RESERVOIR. 407 the common, benefit of the country, Philæ, the pearl of Egypt, will be drowned each year. But she will not be lost altogether ; for, with the coming of July, the waters will fall from her like a robe, and from that month, to Octo- ber Philæ will again bare her beauty to the sun. The problem of raising and at the same time strengthening the existing dam to enable it to hold up water to a depth one-third greater than before, was one of the most difficult ever solved by the late Sir Benjamin. Baker—almost the last on which his genius was engaged. The report of the Irrigation Department for 1907 informs us that the level of the water in the reservoir is to be raised 7 metres, whereas the dam itself is only being raised 5 metres. At present the top of the dam stands 3 metres above the maximum water level; when raised it will stand only one metre above that water level. The manner in which the raising and strengthening is being carried out is shown in Fig 29. To overcome the difficulty caused by variations of expansion and contraction, be- tween the new portion and the existing ma- sonry of the dam, Sir Benjamin Baker devised a scheme by which, the new wall is to have a space of 6 inches width left between it and the present structure, and is to be supported by steel rods sunk into both buildings. These rods, while transmitting the weight of th© new wall, will allow for the difference in expansion and contraction. When it is considered that the two parts have reached the same temper- ature, this space will be grouted with cement mortar. Of course it was arranged that the present usefulness of the dam should not be interfered with while constructing the new work. Operations for the raising of the dam were begun in May 1907, and are now actively pro- ceeding, under the supervision of Mr. M. In Conclusion. MacDonald, Director-General of Reservoirs. It is not ex- pected that the dam in its finished state will Fig. 27.—ASSIOUT BARRAGE, DOWN-STREAM FACE, be ready for use until 1912. With its com- pletion will end one of the most important epochs in the history of Egyptian irrigation. The new century has already seen the crown- ing of five great schemes—the improvement of the Delta Barrage (1901); the formation of the Assouan Reservoir (1902) ; and the construc- tion of the barrages at Assiout (1902), Zifta (1903), and Esneh (1909). Their cost has been great: on the structures named no less than £6,000,000 has already been spent, without taking into calculation works subsidiary to them. Who benefits, and how ? Of course, to answer this question completely is diffi- cult, but we may at least take some facts and figures. In Upper Egypt the Esneh Bar- rage has given permanently to cultivation a large area of land which formerly was liable to be left unirrigated. In Lower Egypt the improvements in the old barrage, coupled with the Zifta Barrage, have fed a new canal, and greatly increased the security of the precious cotton crop.* These simple statements will convey only a vague impression to the general reader may- be, but it is not easy to translate into figures the great services rendered to dwellers in the Nile Valley by those engineering accomplish- * For ten years (1897-1907) the average value of the cotton crop was £17.000,000.