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The mean minimum discharge of the Nile of 650 cubic metres per 
second at Khartoum is obtained on the 1st May and the mean maximum 
of 9000 cubic metres per second on the 1st September. Fed by the White 
Nile reservoir the river falls comparatively slowly. Whether this pecu- 
liar relation of the two rivers to each other could not be taken advantage 
of to increase the supply in December, January and February, and 
decrease it in October and November by means of a regulating dam 
built across the White Nile at Khartoum is worthy of study. 
I greatly prefer the idea of storing the flood waters of the White Nile 
at Khartoum to any storage of the Albert Nile water above the junction 
of the Sobat river. A regulator above the Sobat junction would store 
up a very considerable quantity of water, but the quality would be 
very doubtful and possibly dangerous to health. 
At El Darner, south of Berber, the Atbara flows into the Nile. Dry 
from January to May, the flood begins in June and is at its maximum 
as a rule in the last week of August ; with a mean high flood discharge 
of 3500 cubic metres per second. This water cannot come on to 
Assuan without filling up the 200 kilometres downstream of the 6th 
cataract where the slope of the Nile is gentle and the river lends itself 
to being used as a reservoir. It is owing to the fact that none of the main 
feeders of the Nile flow in immediately below cataracts that the. rise 
and fall of the Nile in Egypt, is so regular and constant. If the Sobat, 
Blue Nile and Atbara all flowed into the White or Main Niles below 
cataracts we should have floods in Egypt whose sudden changes of level 
and fluctuations would be an unending source of danger to the country. 
It is owing to the earliness of the Atbara high flood and the compa- 
rative lateness of the Nile high flood, that the ordinary maximum 
discharge of the Nile at Assuan is only 10,000 cubic metres per second. 
This is generally on the 5th September. When the monsoon is early 
the maximum at Assuan is reached before or on the 5th September ; 
when the monsoon is late the maximum is reached about the 20th 
September. An early maximum at Assuan is generally followed by a 
low summer, while a late maximum is generally followed by a high 
summer supply. Only once has this rule been broken and that was in 
1891 when there were two maxima, one on the 4th September and 
another on the 27th. In this year there must have been an extra- 
ordinary fall of rain in Abyssinia in September, for the flood of the 
27th September was very muddy, while as a rule the river at Assuan 
is very muddy in August, less so in September, still less so in 
