Irrigation in Egypt and S.A. 441 



Situated in one of the largest rainless areas in the world, the 

 climate of Egypt, except the northern margin of the Delta, is that 

 of the great desert area of North-East Africa, the rainfall being 

 extremely small, and occurring mostly as occasional thunderstorms. 

 Along the Mediterranean coast there is a considerable rainfall in the 

 winter months, but this only extends for a short distance southwards, 

 and at Cairo ten or twelve rainy days in a year is probably the 

 average. South of this the amount decreases rapidly, and from 

 Cairo to Luxor, and in the neighbouring deserts, showers on one or 

 two days, and a very occasional thunderstorm, represent probably 

 all that falls in an average year. 



South of Cairo no regular rainfall observations have been made, 

 but the following table gives the average rainfall for six places north 

 of Cairo : — 



p. Rainfall in inches 



per annum. 



Alexandria 8"26 



Port Said 35 



Ismailia 212 



Suez I TO 



Cairo I 06 



It will be evident that the rainfall in Egypt is, for agricultural 

 purposes, practically valueless, and that everything depends on the 

 water of the Nile, derived from rainfall on the upper part of its 

 c^atchment :uea. The total area drained by the river is about 

 1,200,000 square miles, on which the total mean annual rainfall 

 is about 2g inches. The heaviest rainfall occurs about Lake 

 Victoria and Albert and about Lado and the upper halves 

 of the Saubat, Blue Nile and Atbara, and may be taken as 

 about 59 inches per annum. In the Eastern half of the Gazelle 

 river, the lower half of the Saubat and middle third of the Atbara 

 it is about 39 inches. The Western half of the Gazelle river has 

 probably about 19 inches per annum, while the Arab river and the 

 tail portion of the White and Blue Niles, and the Atbara cannot 

 have more than about 10 inches. From Berber northwards the 

 country is practically rainless. 



In the great lake region the rainy .season lasts from February 

 to November, with one maximum in April and another in October. 

 At Lado the rain continues from April to November, with a maximum 

 in August. August is the centre of heavy rainfall everywhere, except 

 at the great lakes. It takes 90 days for the water in low supply to 

 reach the sea from these lakes, while in flood it takes 50 days. 



Owing to the variable periodicity of the rainfall over its catch- 

 ment, the floods in the Nile are neither so sudden nor so intense as 

 might be expected from the extent of the catchment area. The Great 

 Lake and the expanse of swampy " Sudd " south of Fashoda act as 

 regulators in reducing the severity of the flood in Egypt. 



The Nile, nevertheless, behaves in much the same manner as 

 any other storm-fed river. At Cairo the average minimum discharge 

 is about 12,000 cubic feet per second, and is attained about the 



