NILE DAMS.

Hawera Star, Volume XLV, 9 October 1925, Page 2

NILE DAMS.

ANOTHER, project. The Egyptian Government has decided to proceed at once with the construction of a new impounding cl am on the White Nile ait Gebel Auiia, which is about 15 km, upstream of Khartoum, and a subsidiary, but nearly as costly, a work at Nag Hainadi, which is situated on the main Nile between the Assuan Dam and the Assiout barrage, being about 110 miles upstream from the latter. The importance of the new works may be gauged from the fact that, whilst the great Assuan Dam, as now heightened, retains 1600 million cub. m.. of water, the Gebel Auiia Dam will at its designed storage level impound from 3800 million cub. m. to 5700 million cub. m., according to the state of the river, and in exception floods may hold .bade as much as 12,000 million gallons. O'n the average 4000 million cub., m. will be added to the summer supply which passes Khartoum. It will be for the main part a solid masonry structure, but provision is made in the deepest section for large .sluices similar to those adopted at Assuan, and on one side .it will be continued along some high ground as an earthen dam with a masonry core wall. The total length will be 5 km., and the maximum height above foundation level will be 17 m. Provision is made for a lock 80 m. long by 14 m. wide. The height, it. will be .seen, is moderate, and the vast-ness of the storage effected is due to the character of the river valley upstream. The total length of the reservoir -formed will be over 300 miles.

A very largo addition will be made to the area of irrigated lands' in Egypt, but the construction of the dam will also lead to a reduction in the period during which the high flood lasts in Egypt, where enormous damage may arise if tire peak of the flood is long maintained. This Hood is in the main due to the water brought down by tlie Blue Nile, which has a somewhat steep bed down , which floods pass quickly, carrying their silt with them. The presence of this silt makes it impossible to reduce the period of dangerous high water in Egypt by impounding either the flood on the main Nile or on the BDue Nile, owing to silting troubles. Thus the new Sennar Dam, will only impound the tail of the flood. The White Nile on the other hand, is a slow-moving and relatively shallow, cilear-water stream. As matters now stand its waters are ponded upon when the Blue Nile flood arrives at the junction of the two streams, and this ponded water, when it. ultimately flows off helps to prolong the period of high water in Lower Egypt. By the construction of the Gebel Aulia Dam this will no longer occur. The cost of the work is estimated at about 3,000,0001. The Nag Haim ad i barrlage is estimated to cost '2,250,0001., and will be used to convert .a large area, from the basin to the perennial system of irrigation. It will also make it possible to supply “red” or silty water to areas which now receive only “white” water:— “Engineering.”