57 — 
and the Sobat river confined within its channel during its highest 
floods. The White ISTile has a very gentle slope, little carrying capacity 
and is quite incapable of taking on both floods. The water rises at the 
junction and the Sudd region becomes a reservoir flooded to a depth 
of 3 metres. As the Sobat river increases its discharge gradually 
from 75 cubic metres per second in April to 1000 cubic metres per 
second in October and November (for it is confined to its channel), the 
Albert Nile decreases the actual discharge it sends down the White Nile 
and increases what it spreads over the Sudd region. The Albert Nile, 
having increased its quota for the White Nile from 375 in April to 
450 cubic metres per second in September, gives less in October and 
November and gradually passes on its waters in December, January 
and February when the Sobat has fallen. 
The White Nile at its head near Tewfikieh has its mean minimum 
of 500 cubic metres per second in April, and increases slowly to its 
mean maximum of 1 500 cubic metres per second in December. During 
this interval its water surface is raised by 3*50 metres. This water 
travels very slowly on to Khartoum, where the mean minimum is 450 
cubic metres per second in May, the slope is very insignificant, and the 
trough of the river is 1500 metres wide. 
At Khartoum the White Nile meets the Blue Nile. No greater 
contrast exists in the world. If maximum discharges are alone 
considered, the little finger of the Blue Nile is thicker that the loins 
of the White Nile. 
The Blue Nile is at its lowest on the 1st May with a mean minimum 
supply of 200 cubic metres per second rising to a mean maximum flood 
of 10,000 cubic metres per second on the 1st September. The flood has 
fallen to 2000 cubic metres per second by the middle of November. 
Up to the middle of July the Blue and White Niles keep increasing 
their discharges steadily at Khartoum, but after that date the Blue Nile 
gauge and discharge rise rapidly together, and the Blue Nile not only 
feeds the Main Nile, but flows up the White Nile and arrests its discharge, 
so that at Duem, 200 kilometres above Khartoum, the White Nile 
discharge decreases in July and August while the Blue Nile is steadily 
flowing up the White Nile valley and converting it into a reservoir for 
the Nile in winter. It is only after the 15th September, when the Blue 
Nile has begun to fall steadily and continuously that the White Nile 
discharge really commences and reaches its mean maximum of some 
2000 cubic metres per second in October. 
