Engineering Wonders of the World
Volume I

THE NILE DAMS AND THE ASSOUAN RESERVOIR. 405 its design, has embodied in it all the latest improvements in such a structure. Though, the conversion to perennial irriga- tion of all cultivable land is the ultimate aim of the irrigation engineer in Egypt, the works so far described have been designed chiefly to facilitate irrigation during the summer or low Nile season. Now, whereas the Delta, Assiout, and Zifta Barrages are intended to regulate the river level at lowest Nile, and also sometimes at high Nile, the Esneh Barrage is designed primarily to control the river level when the river Nile is in flood. For such is the confor- mation of the country below the Esneh Bar- rage that during low Nile immense tracts of land remain unwatered ; and were it not for the influence of the new barrage, they would be liable to remain out of cultivation even during certain flood seasons. The structure * was begun in 1906, and completed this year— eighteen months within contract time. It was founded in the usual way by the aid of sudds, etc., under conditions more favourable than those which ruled at Assiout. The river bed here is composed of fine and compacted sand, and there were few springs to stanch. Sandstone from the ancient quarries of Gebel Silsileh. is used in the superstructure, which is 2,868 feet long, and carries a roadway 20 feet wide across the Nile. At the west abut- ment is a navigation lock of the same size as that at Assiout. Altogether there are 120 sluice openings along its length. The action of the sluice gates to these open- ings calls for a few words of explanation. The gates are in two leaves, and measure together —one above the other—19 feet 9 inches in Inasmuch as the gates use during the flood be capable of easy ad- leaf has to be moved height. Sluice Gates. , are tor season, they require to justment. The upper more often than the lower leaf, so it is pro- * Messrs. John Aird and Co. were the contractors, and Messrs. Ransomes and Rapier supplied all the iron and steel work. vided along each of its vertical edges with a roller path round which—back and front—cir- culates a continuous chain of friction rollers moving up and down against the sides of the cast-iron grooves in the piers. Regulation of the river height is effected by lowering both leaves on to the masonry floor of the barrage, thus damming the water in the lower part of the sluice passage, but allowing it to flow over the upper edges of the leaves, as in the case of a weir. In order to raise the river height fur- ther, one of the leaves is drawn up. The top edge of this then becomes the crest of the weir, and as it is raised the water level up-stream is raised also. The sluices thus form a series of movable weirs between the piers. The Assouan Reservoir was finished in 1902. Before the end of 1903 all the water made available by it for irrigation had been assigned to special districts, and the Government of Egypt had been constrained to refuse further application for more water. Up to 1907 it had provided water for the con- version of 335,000 acres of land from basin to perennial irrigation. In the Government report, published in that year, Sir William Garst in, then Adviser to the Ministry of Public Works, declared emphatically in favour of raising the Assouan Dam. “ I trust,” he wrote, “ I have made it clear that no alter- native is left to the Egyptian Government but that for raising the Assouan Dam to a height consistent with security, and at the same time sufficient to ensure a large increase in the storage capacity of the reservoir up-stream of this work.” This decision raised again the whole question of the submersion of Philæ. This famous little island—it is only 500 yards in length by 160 yards in breadth—was inhab- ited and built upon, there can The Island , , of Philæ. be little doubt, at a remote period ; but the fabrics that now adorn it be- long to a late epoch of Egyptian history. The Scheme for raising the Assouan Dam.