DAMMING THE NILE.
Further particulars as to damming the Nile for irrigation purposes (notices of which have already appeared in FIRE ANd WATER) have been made public. The work will be undertaken by the Khedive’s government (really the British government) under the personal supervision of Sir Benjamin Baker, who is also responsible for the plans, and it is expected to be finished very early in the twentieth century. The dam will be built just above Assouan, at the first cataract, where the channel of the river is filled with large masses of rock, which will be utilized as a foundation for the structure. The material used in budding the dam will be the same Assouan granite as that of which many of the old Egyptian temples were constructed. By a modification of the plans the ancient ruins of Philae, just above,which would have been covered by the water, are now to be pared. The dam will be seventy feet, instead of 106 feet in height, forty feet wide—the roadway from shore to shore (about one mile and one-qurter long) being sufficient for tiaffic of all sorts A chain of locks,each 150 feet in length, and averaging fifty feet in height, will be on the western side. The crest f the dam will be 320 feet above the lowest level below the cataract, and at flood time the water will be dammed back for 144 miles. The cost of building the main dam at Assouan is set down at §9,000,000, with $6,000,coo more for supplementary dams further down the Nile—the $15,000,000 to be repaid by the Khedival government in thirty years bv yearly instalments; these payments to begin as soon as the receipts yield a profit. The dam will increase the present cultivated area of Egypt by over 600,000 acres, and will besides bring under constant cultivation the whole of that proportion of 500,000 acres which is now under annual irrigation only. For this purpose about 3,610,000 000 cubic centimetres of water will be required, flowing at a maximum rate of 630 metres a second over the whole line of the area affected.
From an engineering standpoint the work is a gigantic undertaking. As Sir Benjamin Baker puts it:
The colossal character of the great dam will be apparent whtn it is stated that the flood discharge of a river a mile wide and thirty feet deep,flowing at high velocity must pass through the dam’s sluices at the rate of 15,000 tons of water per second—goo.ooo tons a minute—more than 50,000 000 tons of water an hour! At times the w’ater will be dammed back sixty-six feet above its psesent level, and for a distaace of 144 miles above the d*m.
Nearly 3,000 years ago the ancient Egyptians derived more benefit from the Nile’s annual floods in this neighborhood than at present. In a northeasterly direction from this first catatract runs the bed of an old branch of the Nile, which even to historic times had been filled up. About 2,000 years before Christ the Nile at this point used to rise twenty-six feet, eight inches higher than the highest level it now reaches during the greatest floods. It must, therefore, have been some time after that period when this bed became dry. The new flow of the water over the lands capable of irrigation will be increased in value to the amount of $230,000,000 and more. The State will receive annually $4,000,000; the annual increase in production will exceed $80,000,000; the annual rental, $15,000,000: the value of the crops, $30 an acre. To these must be added many other contingent material advantages.