So 



NA TURE 



[May 24, 1894 



PERES NIAL IRRIGATION IN EGYPT. 



THE "Report on perennial irrigation and flood pro- 

 tection for Egypt," by Mr. Willcocks, brings us 

 face to face with one of the most stupendous applications 

 of science of modern times, and it is to be regretted that 

 in consequence of the tardy arrival of the report and 

 plans in this country, and of the general interest having 

 been directed to a side issue, both the vastness of the 

 scheme and the completeness and admirable method of 

 the preliminary studies have received scant recognition. 

 Everybody is familiar with the saying of Herodotus 

 that Egypt is the gift of the Nile, but only few are 

 familiar with the conditions of the river, which are thus 

 tersely stated in one of the appendices to the report. 

 "The Nile drains nearly the whole of North-Eastern 

 Africa, an area comprising 3,110,000 square kilometres. 

 Its main tributary, the While Nile, has its sources to the 

 south of Lake Victoria, and has traversed over 3500 kilo- 

 metres before it is joined by the Blue Nile at Khartoum. 



Taking the years since 1S73 the mean of the mini- 

 mums (which vary between May 14 and June 24) was 

 - o oS of the gauge ; the mean of the ma.vimums (which 

 vary between .August 20 and October i) is S17. The 

 Nile flood level at Assuan is then roughly 27 feet above 

 average low water. The water therefore passing over the 

 cataract varies enormously in quantity at low and high 

 Nile ; we have in an average of 20 years 440 cubic 

 metres per second in May, 9170 in September. 



Finally, of all this water which passes Assu.in in such 

 varying quantities at difi"erent times of the year, the total 

 yearly average quantity being equal to 2990 cubic metres 

 per second, 370 disappear before Cairo is reached, where 

 the discharge is 2610 cubic metres per second ; of this 

 again 550 cubic metres are absorbed for the irrigation of 

 Lower Egypt, so that 2060 cubic metres reach the sea 

 each second, or 65,000,000,000 each year. 



The rainfall as stated, treated as it is in Egypt at the 

 present day, gives us the land area under cultivation, the 

 number of crops per annum, and the quantity of produce 



I 







<,^ III r*x'f ' 



■"-- \ c:?> 



fs-s^-' 







^ '-V, 



n;>n^,- *ytt.^i,rall ■ 



The Front Cataract at .^ssnan, shi-wing the Dams proposed. P P, Philic ; A A A, Assuan. 



From the junction onwards the river is known as the 

 Nile, and after a further course of 3000 kilometres flows 

 into the .Mediterranean Sea by the Rosetta and Damietta 

 mouths. The modulus of the Nile at Assuan is 21)90 

 cubic metres per second, and at Cairo 2610 cubic metres 

 per second." 



The total mean annual rainfall in the Nile valley, in- 

 cluding the desert north of Khartoum, amounts to 

 2,633,000,000,000 cubic metres. This water is brought to 

 the main stream by the White Nile in a pretty constant 

 quantity all the year round, but the river is liable to an 

 annual flood which is due to the .Saubai, the IJlue Nile 

 and the Atbara. Leaving out of consideration the acci- 

 dents of the river above Assuan, we may stale that at that 

 place IS the last of a series of cataracts, and also is a 

 gauge by which the various heights of the river at dif- 

 ferent tiinci of the year and in different years are re- 

 corded. The gauges are in metres, and are referred to 

 mean low water level as zero. The zero at Assuan is 85 

 metres above the level of the Mediterranean. 



on which the revenues of the country, and the food of the 

 inhabitants, depend. 



The question which has occupied the Egyptian en- 

 gineers of lale years has not been whether waste lands 

 can be brought into cultivation and the agricultural yield 

 increased if tliere were more water that has long been 

 obvious— but //ere iiiih/i water was wanted in the worst 

 years. Other questions were, whether the amount was 

 available in the river, and at what period. First as to 

 the amount wanted : — 



NO. I 282, VOL 50] 



Upper 



Egypt 



Middle 



Egypt 



Lower 



Egypt 



Assu.in I 



.\ ssj u t ( 



Assy lit I 



Cairo I 



Cairo | 



Sta J 



> A feddan 



Affa in 

 fcddanv' 



I , 200,000 

 1,200,000 

 2,810,000 



: <'°° of an acre. 

 4047 



Wa'er wanted 

 in cubic metres. 



I,l60,<XXI,00O 



950,000,000 



1,551,500.000 



