96 — 
Nile from Assuan to Cairo has been levelled, and cross sections taken 
at every 3 kilometres. The kilometrage on Plate XII counts from the 
Assuan gauge and is measured down the centre of discharge of the 
flood, since it is with flood discharges that we are principally dealing. 
As the Nile winds about considerably and is often broken into nume- 
rous channels, the areas of the cross sections vary very appreciably 
according as they are taken at right angles to the centre line of 
discharge or of the deep channel of the river. The former gives the 
more reliable results. I have taken 8 millimetres per day as the eva- 
poration during flood in Upper Egypt. The absorption has been 
calculated from the water consumption during the floods of 1892 and 
1893, and found to be about 300 cubic metres per second between As- 
suan and Assiout, where there is practically no perennial irrigation. 
Between Assiout and Cairo, where there is a considerable length of 
perennial irrigation on one bank and limestone rock on the other, the 
absorption is about 100 cubic metres per second. 
When perennial irrigation has once established itself in Upper 
Egypt, we may assume that the absorption during flood will be halved 
in quantity for the reasons given above, and become 150 cubic metres 
per second between Assuan and Assiout, and 50 cubic metres per 
second between Assiout and Cairo. The amount of water expended 
in irrigation will be about 700 cubic metres per second. The evapo- 
ration during flood will be approximately 120 cubic metres per second. 
The quantity of water needed to fill the trough of the Nile will depend 
on the gauges and may be calculated from table 43 of Appendix K. 
The last item will be the only variable one and the others may be ap- 
proximately tabulated as follows 
Expenditure of water in flood in cubic metres per second * 
Between 
Assuan and Assiout. 
Between Assiout and Cairo. 
TOTAL 
Perennial irrigation 
. 350 
350 
700 
Evaporation 
65 
55 
120 
Absorption 
. 150 
50 
200 
Total of above 
. 565 
455 
1020 
Taking these quantities and calculating directly for the filling of the 
trough from the gauges themselves, I have collected in Tables 50 
to 52, the Cairo gauges corresponding to the Assuan gauges for 
