The Nile, before it flows into Lake No, appears to be a channel varying from 100 yards to a mile in width, but, from the masthead of a steamer, it would be seen that there is a sea of papyrus grass, bulrushes, and reeds on either side of this water channel, and that the real banks of the river are 4, 8, or even 12 miles distant on either side. Under all this vegetation is water, which is slowly making its way down to fill up the void caused by the absorption of the water by plants and sun. The matted vegetation which floats on the top of the water is so thick that it is possible to walk on it; and, were it not for this covering, the evaporation over such a vast area would greatly diminish the supply of water to Lower Egypt.
A considerable part of the Nuer tribe actually live on the floating mass of vegetation, fish and the stalks of a water-lily forming their only food. The surface of the water is covered by a dense tangled mass of papyrus, ambach, and other water plants, which in places grow to a height of from 15 to 30 feet.
At the rise and fall of the Nile, quantities of the grass get torn away and float down stream. If the season is unusually wet, the stream increases in bulk and rapidity, and innumerable large masses of the grass, hurried and packed by the wind, are sent floating down; these jamb in the channels and form the sudd blocks.
The channel of the river is very tortuous; at Lake No, for instance, where the Bahr El Ghazal flows into the Nile, there is a sharp turn to the east. If the water contributed simultaneously by the Bahr El Ghazal happens to be insignificant and incapable of sweeping away the floating masses, a block is the result at this point.
4. Sandbanks.—They are not as a rule any considerable obstacle, but are, of course, more troublesome at low than at high Nile, and shift about every year.
Steamers with no encumbrances, and with fuel ready cut for them to pick up, take about 12 days up stream from Khartoum to Gondokoro, and about 8 days down stream. (Record journey in 1903: 11 days up and 7 down).
The navigation up to the mouth of the Sobat is at all times easy, the Abu Zeid Ford and occasional rocks and sandbanks forming the only difficulties. The deepest channels lie usually towards the east bank. From the Sobat to Gondokoro a perfect and recent knowledge of the route is required, in order not to deviate into any of the lateral branches which are frequently met with, and which, varying from year to year, are chiefly in evidence during and after the rainy season.
There are also many sandbanks on this stretch. Between Gondokoro and Rejaf the river is rather difficult when low on account of shifting sandbanks and islands. There are a few rocks, but not dangerous, except at one point.
Between Rejaf and Bedden there is the same difficulty of shifting sandbanks and sunken rocks, which are, however, isolated and few in number, and might be blasted away. The current here is about 1½ miles an hour. At Bedden there is a bad rapid necessitating a transhipment; but from there boats can go to Kiri.
From Kiri to Labore there are awkward rapids, but the river might be utilised to a great extent. The river continues of much the same character till the junction of the Asua, when the rapids become more serious, terminating in the Fola Rapids.