South or upstream side of the dam at Assouan, from west bank.1

The monumental dam at Assouan, which is by far the greatest achievement of its kind in ancient or modern times, forms a reservoir in the Nile valley capable of storing 1,000,000,000 tons of water, practically creating a lake more than 140 miles long. The foundation stone was laid by the Duke of Connaught on February 12, 1899. At times fifteen thousand men have been employed, and work has gone on day and night. At other times, when the Nile was in flood, labor had to be suspended for several weeks.

One gains a clearer idea of the magnitude of the task by recalling the first step taken; that was, to divert the channel and excavate in the rocky river-bed a trench one hundred feet wide and as many feet deep, in which to lay a concrete foundation for the massive piers.

At its best, and controlled, the Nile is very generous, as befits the majesty of its three thousand miles. Joseph the Israelite drew some of his prosperity from it. One of the irrigation canals he planned for Pharaoh's people is still in use. But in most moods the Nile is a sullen and inconstant stream, and even in the days when Egypt was the granary of imperial Rome there seems to have been no comprehensive attempt to govern it.

The great dam at Assouan. Entrance to locks of navigation channel from the south.

Napoleon had a faint perception of the thing that needed to be done when he suggested a dam near Cairo. That, he realized, would double the cultivable area around the river's mouth. In the earlier portion of the 19th century two barrages were actually built at that spot by a French engineer—badly built, however, and useless until, of recent years, the British reconstructed them. This work consists, in effect, of two brick arched viaducts crossing the Rossetta and Damietta branches of the Nile, having, together, 132 arches of 16-feet-four-inches-span, which were entirely closed by iron sluices during the summer months, thus heading up the water about 15 feet and throwing it at a high level into the six main-irrigation canals below Cairo. In the summer months the whole flow of the Nile is arrested and thrown into the aforesaid canals.

The most important of the worksconstructed to enable the water stored up in the great reservoir to be utilized to the greatest advantage is the barrage across the Nile at Assiout, about 250 miles above Cairo, which was commenced by Sir John Aird & Company in the winter of 1898, and completed in 1902. In general principle this work resembles the old barrage at the apex of the delta; but in details of construction there is no similarity, nor in material, as the old work is of brick and the new one is of stone. The total length of the structure is 2,750 feet, or rather more than half a mile, and it includes 111 arched openings of 16 four-inch spans, capable of being closed by steel sluice-gates 16 feet in hight.

The object of the work is to improve the perennial irrigation of lands in Middle Egypt and the Fayoum, and to bring an additional area of about 300,000 acres under such irrigation by throwing more water at a higher level into the great Ibrahimick Canal, the intake of which is immediately above the barrage.

The navigation channel entrance locks from the north.

The total length of the dam is about a mile and a quarter; the maximum height from the foundation is about 130 feet; the difference, of level water above and below, 67 feet; and the total weight of masonry over 1,000,000 tons. Navigation is provided for by a "ladder," of four locks, each 260 feet long by 32 feet wide. As with the case of Assiout, the difficulties in dam construction are not in design, but in the carrying out of the works. When "rotten rock" in the bed was discovered, Sir Benjamin Baker frankly reported to Lord Cromer that he could not say what the extra cost and time involved by this and other unforeseen conditions would be, but that, however bad the conditions, the job could be done. He was told to go ahead with the work.

The first channel was successfully closed on May 17, 1899, the depth being about 30 feet and the velocity of the current about 1.5 miles an hour. In the case of another channel, the closing had to be helped by tipping in railway wagons themselves, loaded with heavy stones and bound together with wire ropes, making a weight of about 50 tons—this great mass being necessary to resist displacement by the torrent. These rubble dams were well tested when the high Nile ran over them; and on work being resumed in November, after the fall of the river, water-tight sand-bag dams, or "sudds," were made around the site of the dam foundation in the still waters above the rubble dams, and pumps were fixed to lay dry the bed of the river.

Looking to the east along the top of the dam. Regulating gear for sluices to the right.

This was the most exciting time in the early stage of the operations, for no one could predict whether it would be possible to dry the bed, or whether the water would come pouring through the fissured rocks in altogether overwhelming volumes. Twenty-four 12-inch centrifugal pumps were provided to deal if necessary with one small channel; but, happily, the sand bags and gravel and sand embankments staunched the fissures in the rock and the interstices between the great bowlders covering the bottom of this channel, and a couple of twelve-inch pumps sufficed.

The masonry of the dam is of local granite, set in British, Portland-cement mortar. The interior is of rubble set by hand with about 40 per cent of the bulk in cement mortar, four parts of sand to one of cement. All the face work is, of course, rock-faced ashlar, except the sluice linings, which are finely dressed. The maximum number of men employed on this dam was 11,000.

Early irrigation in Egypt. Most primitve methods of farming prevail.

The old system of irrigation was little more than a high Nile flooding of different areas of land or basins surrounded by embankments. Less than a hundred years ago, perennial irrigation was first attempted to be introduced by cutting deep canals to convey the water to the lands when the Nile was at its low summer level. When the Nile rose, these canals had to be blocked by temporary earthen dams, or the current would have wrought destruction. As a result, they silted up, and had to be cleared of many millions of tons of mud each year by enforced labor, much misery and extortion resulting therefrom.

Moreover, the old canals and the dams at the delta barely touched the surface of Egypt's irrigation problem, the problem of avoiding drouth and making waste lands fertile. The great dams at Assouan and Siut, "inaugurated" in the summer of 1903, go to the bottom of things in more than one sense of the word.

At Assouan, near the First Cataract, nearly six hundred miles from Cairo, the Nile is a mile wide. The dam is a quarter-mile wider, a great granite wall that rises ninety feet above the level of low Nile, and is sixty feet wide at the top.

When the river is in flood, its waters gush through one hundred and eighty massive sluice-gates. In autumn the sluice-gates are closed until the reservoir thus formed is full, ready to be distributed through canals and ditches over the agricultural land on either side. In April and August, when the water is most wanted for the crops, the supply in the lower river is increased from the reservoir.

At Siut, about half-way between Assouan and Cairo, is a subsidiary dam a half-mile wide, with more than one hundred sluice-gates. Broadly speaking, the two reservoirs add $400,000,000 in land values to the region covered by their operation.

OLIVE CULTURE ON AN EXTENSIVE SCALE
HOW GLASS IS MADE TO-DAY
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© 1998, 2002 by Lynn Waterman