WEALTH IN WATER

Evening Post, Volume CXVI, Issue 146, 18 December 1933, Page 7

WEALTH IN WATER

EGYPT'S PROBLEM

HARNESSING THE NILE

From time immemorial, Egypt has been entirely dependent for its cultivation on the Nile Eiver, for there is in Egypt no other source of water. The valley of the Nile is bounded by an »rid. desert. Outside of a narrow belt near the Mediterranean there is almost no rainfall. Relying upon the periodical seasonal flood of the Nile, the ancient Egyptians, however, attained remarkably efficient results in Irrigation by comparatively simple methods, remarks Hamilton M. Wright in tha '' Scientific American It is only in modern times, however, that Egypt has begun to store her surplus flood waters for use in irrigation when most needed, and so to do away, with the "lean years" which are a part of Biblical traditions. In ancient times and until comparatively recent years any pronounced change in the normal supply of water, as in the casa of either excessive floods or drought, was usually expressed in the ruin and misoTy of many. Today, the water in the Assouan Eeservoir safeguards Egypt from years of even the lowest water, supply. The Egyptian Government- is not only going ahead with vast engineering works to regulate tlie water supply; scientifically but has completely envisaged a' gigantic seheine for harnessing the entire Nile system. This includes the second heightening of tha Assouan Dam, soon to be completed, as well as other reservoirs planned or constructed in Abyssinia, the AngloEgyptian' Sudan, and central Africa: At present the Government of Egypt is seeking to adjust its irrigation developments to take care of the normal increase in population. The Government is also seeking to stimulata industry so that the country will not be almost totally dependent upon agriculture. Basin irrigation. in Egypt has been to a large extent replaced by perennial, or year-round, irrigation made possible by the construction of dams, barrages, and canals. .Supplementary to the Assouan Dam as sources of water supply for apportionment through Egypt, several other gigantic reservoirs are planned. One of these will be located at Lake Albert; another at Gebel .Aulia, 30 miles south of Khartoum; while the groat Serinar Dam constructed in the Blue Nile in 1926 and the proposed reservoir- at Lake Tana, Abyssinia, will have important benefits in regulating the flow to Egypt. The principal water supply of Egypt during the flood season—that is in August and September—comes from tha Blue Nile, at Khartoum, which discharges 5700 cubic meters of water per second, or 70 per cent, of the total amount of water coming down to the Assouan Dam at that time. The White Nile discharges 800 cubic meters of : water per second or 10 per cent, of the total, and tho Atbara Biver which, like the Blue Nile, starts in Abyssinia, supplies 1700 cubio meters of water per second or 20' per cent, -of the. water going down to Assouan during the summer. By the following April, the flow of the Blue Nile falls down to an average of 120 cubic meters per second, at Khartoum, while no flow at all is recorded for the Atbara during the months of January, February, March, April, and May. The White Nile at Khartoum has its maximum discharge in October, the average -being 1400 cubic meters per second, falling to 540 cubic meters per second in April, at which time the White Nile contributes an average of 82 per cent, of the water supply going to Egypt. . The discharge of. the White Nile is derived from two sources: the Sobat,rising in Abyssinia and flowing into the Nile almost 500 miles south of Khartoum, and the Bahr el Zeraf and Bahr el Gebel. BUILDING A NEW DAM. The Sobat is tho main, tributary of the White Nile and supplies about onehalf of the total annual discharge of that river. It is at its maximum during the flood, or untimely season, henes to use the water to the best advantage it must be stored in a reservoir till the timely season. This is to be accomplished in the White Nile Valley, by constructing a dam at'Gebel Aulia. The Gebel Aulia Eeservoir will be filled during July, August, and September, by water that would otherwise flow to the sea. It will stand full until early in January, the beginning of the timely season, and would then be emptied for irrigation in Egypt. Preliminary surveys for a reservoir have been made at Lake Albert which may be regarded as the effective source of the Nile for present'irrigation purposes. Lake Albert has an area of 5300 square kilometers and lies partly; in Uganda and partly in the Belgian Congo. The function of the reservoir to be created by the Lake Albert dam will be to store the rainfall of wet years for use in dry years, equalising as far as possible the flow from Lake Albert. As the maximum range of levels that would have to be controlled by the Lake Albert Dam is 10 meters, the amount of controllable stored water in the reservoir would be over 50,000,000 cubic meters, more than ten times that behind the twice heightened Assouan Dam. The average outflow of Lake Albert along the Albert Nile is reckoned on a conservative estimate to be about 19,000,000,000 cubic meters a year, and this is the amount that will in tha future be discharged year by year but not evenly throughout the year. As much water as possible will be allowed to flow out during th« "timely" period, that, period of tl*ei year when Egypt is short of water. The reservoir will be so controlled that , in any year, the total flow will be equal to the mean annual flow. The outstanding engineering problem of the whole Lake Albert project is tho determination of the canal and river improvement -work necessary to conduct the surplus rainfall to bo storedin Lake Albert either through or, around the obstructing masses of vege« tation that fill the 400 miles of tropical swamps through which the Upper Nile flows after entering the plains of the Sudan and while on its way north to Egypt. When the' contemplated works havo been completed, the conditions of flow pertaining in the Nile will bo very; nearly ideal front the point of vievr of the irrigation engineer.