— 59 — 
October and much less in November when the White Nile is the ruling 
factor in the supply of the river. 
If the September rains in Abyssinia are very heavy, an ordinary 
flood passes Assuan at the end of September and is disastrous for 
Egypt. This happened in 1878. Table 26 contains details of this 
flood, of the minimum flood year 1877 and the mean of the 20 years 
from 1873 to 1892. 
At Assuan the Nile enters Egypt, and it now remains to consider it 
in its last 1,200 kilometres. The mean minimum discharge at Assuan 
is 590 cubic metres per second and is reached about the end of May. 
The river rises slowly till about the 20th July and then rapidly through 
August, reaching its maximum about the 5th September, and then 
falling very slowly through October and November. The deep pere- 
nial irrigation canals take water all the year round, but the flood 
irrigation canals are closed with earthen banks till the 15th August, 
and are then all opened. These flood canals, of which there are some 
45, are capable of discharging 2,000 cubic metres per second at the 
beginning of an ordinary year, 3,600 cubic metres per second in a maxi- 
mum year, and have an immediate effe'ct on the discharge of the Nile. 
The channel of the Nile itself and its numerous branches and arms 
consume a considerable quantity of water (the cubic contents of the 
trough of the Nile between Assuan and Cairo are 7,000,000,000 cubic 
metres), the direct irrigation from the Nile between Assuan and Cairo 
takes 50 cubic metres per second, 1 30 cubic metres per second are lost 
by evaporation off the Nile, and 400 cubic metres per second by absorp- 
tion. Owing to all these different causes, there is the net result that, 
from August 15th to October 1st, the Nile is discharging 2,400 cubic 
metres per second less at Cairo than Assuan. During October and 
November the flood canals are closed, and the basins which have been 
filled in August and September discharge back into the Nile, and in 
October the Nile at Cairo is discharging 900 cubic metres per second in 
excess of the discharge at Assuan and 500 cubic metres per second in 
excess in November. 
The mean minimum discharge at Cairo is 500 cubic metres per 
second and is attained on the 15th of June ; the river rises slowly 
through July and fairly quickly in August, and reaches its ordinary 
maximum on the 1st October when the basins are full and the 
discharge from the basins is just beginning. The ordinary maxi- 
mum discharge at Cairo is about 7,600 cubic metres per second. 
