46 — 
The principal tributaries of the Atbara are the Salaam and Settit 
already mentioned. On its right bank between Gosrejeb and Adarma 
it is joined by the Gaash river, which flows past Kassalaand loses itself 
in the deserts. In years of extraordinary rainfall the Gaash reaches the 
Atbara. The Gaash at Kassala has a width of 150 metres, depth of 
1 metre and approximate discharge of 300 cubic metres per second 
in an ordinary flood. It has a course of about 160 kilometres before 
it disappears in the desert. 
21. The Nile from Khartoum to Assuan. — The Nile begins 
its course without any gauge to record its varying height. A gauge 
north of Omdurman, another upstream of the 6th cataract and a third 
downstream of the cataract are badly needed. Until these three gauges 
are erected and recorded, and another erected and recorded on the Blue 
Nile at Kamlin, about 100 kilometres above Khartoum, the behaviour 
of the Nile and its tributaries at their junction will never be exactly 
understood. Making use of the information which is obtainable, we 
may say that the Blue Nile is generally at its lowest between the 15th 
April and 15th May with a mean low-water discharge of about 200 
cubic metres per second, falling to nearly zero in certain years ; it is 
at its highest between the 15th August and 15th September with a 
mean maximum discharge of some 10,000 cubic metres per second, 
rising to 13,000 and falling to 6,500 in maximum and minimum 
years. If the larger figure is correct, the Blue Nile bank at Khartoum 
is over a metre too low, and the town is liable to be flooded out. 
If reference is made to Plate VIII it will be seen that the flood 
of the Blue Nile in July, August and September travels up the White 
Nile, holds back its waters and converts the valley of the White Nile 
into a flood reservoir. When the Blue Nile falls rapidly in October 
and November, the discharge of the Nile is maintained by the stored- 
up waters in the White Nile and b}^ the White Nile flood which has 
slowly travelled down its almost level bed. Table 24 shows this more 
clearly than any description could. I do not think that the maximum 
discharge of the Main Nile on any given day is ever equal to the 
maximum discharge of the Blue Nile. 
The Nile between Khartoum and Berber has a channel wider and 
deeper than that between Wady Haifa and Assuan and a gentler 
current. I have not taken, or seen any discharges which have been 
taken in this reach, but judging from what I saw I should say the 
channel was 800 metres wide on the average. At a distance of 86 kilo- 
