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CHAPTER III. 
The utilisation of thp Nile. 
24. The Nile in flood. — We are now in a position to apply our 
knowledge of the Nile and its tributaries to an examination of the be- 
haviour of the rivers in flood and in time of low supply. Lake Victoria, 
the Victoria Nile, and Lake Albert may all be considered as the great 
equatorial regulators of the Nile. The river, as a river, begins at the 
outlet of Lake Albert, i.e., at the head of the Albert Nile. Generally at 
its lowest in April, it rises gradually and reaches its maximum in 
November. The mean minimum of 600 cubic metres per second is 
gradually increased to its mean maximum of 900 cubic metres. The 
regulating effect of the lakes is very evident. 
Between Lake Albert and Gondokoro the heavier rains begin late in 
April and with a break in June and July continue to November. The 
mean minimum discharge of 600 cubic metres per second in April is 
increased by alternating rises and falls to the mean maximum of 1600 
cubic metres per second in September, which has disappeared by the end 
of November, when the water of Lake Albert alone remains in the river. 
The Gazelle river in no way affects the flood or the low supply. Its 
great function is to maintain the levels of the great swamps between 
latitudes 7° and 9°, saturate the soil, and prevent the complete disap- 
pearance of the waters of the Albert Nile between January and May. 
The functions this river performs are humble ones, but deprived of its aid, 
the Nile north of Khartoum would frequently be dry in April and May. 
The Albert Nile at its tail just upstream of the mouth of the Sobat 
is at its lowest in April and May with a mean low discharge of 375 
cubic metres per second, when it is joined by the Sobat river with an 
approximate mean low discharge of 125 cubic metres per second; 
making a joint discharge for the head of the White Nile of 500 cubic 
metres per second as a mean minimum. Now begins one of the most 
interesting operations of any in the whole valley of the Nile, exceeded 
only in interest by what happens at Khartoum lower down. The 
Albert Nile and the Sobat river both rise together, the Albert Nile on 
a very gentle slope freely overflowing its banks in the Sudd region, 
