Proceedings.1 FITZMAUBICE ON THE NILE RESERVOIB. 71 27 January, 1903. JOHN CLAREE HAWESHAW, M.A., President, in the Chair. (Paper No. 3361.) “ The Nile Reservoir, Assuan.” By MAURICEFITZMAURICE, C.M.G., B.A.I., M. Inst. C.E. WITH the exception of the northern margin of the Delta along the coast of the Mediterranean, Egypt (Fig. 1) is a country practically withoutrain, and is absolutelydependent on theNile for its water-supply.The volume of water in theriver during the wintermonths is much larger thanis requiredfor the needs of the country, and during the summer months the supply is not nearly sufficient. It istherefore not surprising thatthe con- struction of reservoirs which should enable part of the surplus winter water to be stored for use during the summer months has been a burning questionin Egypt for many years. The White Nile, coming from the great lakes of Central Africa and fed on theway by the Gazelleand Sobat rivers, joins at Khartumthe Blue Nile, which comes from the Abyssinian mountains.From the junction northward the river is known as the Nile ; and it receives its only tributary, the Atbara, at a distance of 320 kilometres (ZOO miles)north of Ehartum. The Nile enters Egypt atAssuan, 1,800 kilometres (1,125 milesj north of Khartumand 1,200 kilometres (750 miles)from the Medi- terranean; and the ancient Nilometer built here is the standard gauge as regards the state of the river. The first rise of the level of the water in theriver at Assuan appears about the endof May; and thereis then a continuousslow riseuntil theend of June, after which date it becomes more rapid (Fig. 5, Plate 1). The first part of the rise is due to flood-water coming down the White Nile ; but by the end of June the 0oods coming down the Blue Nile and 1 In the original most of the dimensions are inmetric meamres: for convenience, approximate English equivalents have been added in brackets. Downloaded by [ University College London] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. 72 FITZXAURICE ON THE NILE RESERVOIR. [Minutes of the Atbara are felt atAssuan. During July the two latter rivers are rising rapidly, and during August and September the Nile is in full flood at Assuan, and the water is heavily charged with therich fertilizing mud which the Atbara and the Blue Nile bring down from theAbyssinian hills. From the beginningof the flood at Assuan, at theend of May, until the maximum is attained, Fig. 1. r-- 1 iWISDITl?RRAXJ?A~V SL’A about the 10th September, the discharge of the river rises in an average year from about 400 cubic metres to 10,000 cubic metres (14,000 cubic feet to 353,000 cubic feet) per second. The maxi- mum flood-discharge of the White Nile is about4,500 cubic metres (159,000 cubic feet), of the Blue Nile 5,500 cubic metres (194,000 cubic feet), and of the Atbara 3,500 cubic metres (124,000 cubic feet),per second; but, as the White Nile does not attain its Downloaded by [ University College London] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. PrOoeedingS.] FITZMAURICE ON THE NILE BEBERVOIR. 73 maximum until abouta month later than the other tworivers, the maximum discharge at Assuan is less than the aggregate maxima of the three rivers. There are two systems of irrigation in Egypt-basin irrigation and perennial irrigation. In the basin system the waters of the Nilewhen in flood areturned on tothe land, which for this purpose is divided into large areas called basins, and there the valuable fertilizing mud is deposited. The water remains on the land to an average depth of about 1-50 metre (5 feet) for about 40 days,and is thenturned into the river again. Under this system one crop is obtained inthe year. Withthe perennial system the land is irrigated all the year round; two crops are obtained every year from a large portion of the land ; and the crops are more valuable than the “basin ” crops. With a low- Nile discharge during the summer months, however, there is not sufficient water for even the present area under perennial irri- gation; and consequently some of the land gets no water, and some an insufficient supply. The object of the reservoir at Assuan isto supplement the discharge of the Nile during the summer months of May, June and July, by dischargingthe water whichbeen has stored during the winter months: thus ensuringa sufficient supply of water to the land at present under perennial irrigation, and enabling anincrease to be made in the areaof land irrigatedon this system. This willallow a large increase in the land under the valuablecrops of sugar-cane and cotton. HISTORICAL. The first systematicstudy of thequestion where reservoirs could be made, of the best method of making them, and of the amount of water obtainable,was commenced in 1890. Before that date, several suggestionsfor reservoirs had been brought forward at different times; but it was not until 1890 that the Egyptian Government, at therequest of Sir Colin Scott-Moncrieff, K.C.S.I.,Assoc. Inst. C.E., decided to study the whole question anew; and Mr. Willcocks (now Sir William Willcocks, E.C.M.G.), M. Inst. C.E., was appointed director-generalof the study. In his report,lmade atthe end of 1893, after more than 3 years’3 careful study of thevalley of theNile and the depressions inthe desert north of WadiHalfa, Mr. Willcocks “ Report on Perennial Irrigation and Flood Protection for Egypt.” Cairo, 1891. Downloaded by [ University College London] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. 74 PIT~AUBICEON THE NILE RESERVOIR. Wiutes of dealt with four sites for reservoirs, three in the Nile valley and one in the Wadi Rayan depression in the desert, about 30 kilo- metres (19 miles) west of theNile valley, a siteoriginally proposed by Mr. Cope Whitehouse. The reporb was accompanied by plansand estimates for the works necessary at each place. Mr. Willcocks considered the reservoir which could be formed by a masonry dam at the head of the first cataract on the Nile, at Assuan, to be the best of the different schemes submitted. This viewwas endorsed by Sir WilliamGarstin, G.C.M.G., Under Secretary of State for the Public Works Department ; but owing to themagnitude of the work he proposed thatthe Egyptian Government should appoint a Commission of three of the most eminent engineers in Europe, for the purpose of considering the several schemes andadvising the Egyptian Government as to which of them should be adopted. The Commission was accordingly appointed, and consisted of Sir Benjamin Baker, K.C.B., E.C.N.G., Past-President Inst. C.E., Mr. Giacomo Torricelli and Mr. Auguste BoulB. These gentlemen spent 3 months in Egypt, examining all the proposed sites, and going through the plans and projects placed before them by the Egyptian Government. They reported :- l. Thatthe valley of theNile was more suitablethan the Wadi Rayan depression for the formation of a reservoir. 2. That the reservoir-dam should, as proposed by Mr. Willcocks, be pierced by numerous undersluices regulated by gates, capable of passing thewhole volume of the Nilein flood. This wasnecessary to prevent any deposit of silt in the reservoir during flood. 3. That there was no insurmountable difficulty in constructing such a dam and ensuringits permanent stability. Two members of the Commission, Sir BenjaminBaker and Mr. Torricelli, selected, from amongthe sites fora dam sub- mitted to them by the Egyptian Government, the head of the Assuan cataractas the only place on the river north of Wadi Halfawhere the followingconditions, whichthey considered necessary, could be obtained, namely :- (U) A solid rock foundation. (a) A wide section of river, so that the openings might not be close together. This condition would cause the dam to approach as nearly as possible to a solid one, and would permit the water issuing from the sluices to be well scattered and evenly distributed. (c) A shallow depth of water, so that the total height of dam above the foundations mightbe as small as possible. Mr. Bode made no selection of a site for a dam. Downloaded by [ University College London] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] FIT!ZNAUFLICE ON THE NILE BESEBVOLR. 75 The sametwo Commissioners also recommended alterations inthe Governmentdesign for a dam atthis place. All the modificationswere inthe direction of makingthe design approach more closely to that of a solid dam, and of increasing its stability. As a result of the decision of the Commission, it was decided to construct a dam to hold up water to Reduced Level 114.0000) (374’ at the siterecommended by Mr. Willcocks, namely, acrossthe head of the Assuan cataract, to the north of the island of Philae. The maximum head on the dam would be 26 metres (85 feet), and the volume of water stored would be about 2,500 million cubic metres (88,300 million cubic feet). The construction of a dam raising the water-level to the height stated involved the submersion of the temples on the island of Philae; and strong protests against the scheme were lodged by the principal archaological societies of Europe. The project was consequentlyreconsidered, and Mr. Willcocksprepared revised designsfor a dam to hold upwater to R.L. 106.00(348*00), adoptingthe different modifications proposed bySir Benjamin Bakerand Mr. Torricelli.These designs were ready early in 1895, butowing to financial reasons it was not possible to commence the work at that time. The probable effect on the health of the inhabitants of Egypt from the storage of such a large quantity of water ; the question whether the water thus stored would deteriorate ; and the effect of the subtraction of a large quantity of water from the usual discharge of the Nile at certain periods of theyear; were all subjects of anxious consideration by the Egyptian Government.