The Nile in 1904

by Sir William Willcocks

Lith. Sur. Dep. Cairo.

[Larger illustration] (180 kB)

ERRATUM.
Erase the two figures under Lake Choga in the “Height” column.

LONGITUDINAL SECTION of the NILE,
THE BLUE NILE, THE WHITE NILE, THE ALBERT NILE, THE VICTORIA NILE & THE SEMLIKI RIVER

The White Nile falls 14 metres in 840 kilometres and has two slopes in flood; ¹⁄₅₀₀₀₀ in its upper reach, and then ¹⁄₁₀₀₀₀₀.

The Blue Nile falls 1370 metres in 1370 kilometres, which may roughly be divided into three reaches. The first from Lake Tsana to Rosaires on a length of 750 kilometres ¹⁄₆₀₀, the second Rosaires to Sennaar ¹⁄₄₅₀₀, and the third ¹⁄₇₀₀₀. These are very approximate indeed.

The Atbara falls 1640 metres in 880 kilometres. In the first 300 kilometres the slope is ¹⁄₂₀₀; in the next 300 kilometres the slope is ¹⁄₂₅₀₀, and in the last reach of 280 kilometres it is ¹⁄₆₀₀₀. These are approximate.

The Main Nile from Khartoum to Assuan falls 295 metres in 1810 kilometres; the so-called six cataracts occupy 565 kilometres with a slope of ¹⁄₃₀₀₀; and the ordinary channel occupies 1245 kilometres and has a slope of ¹⁄₁₂₀₀₀. From Assuân to the Barrage, on a length of 970 kilometres, the Nile falls 76 metres with a mean slope of ¹⁄₁₃₀₀₀. The Rosetta and Damietta branches are each about 240 kilometres long and have a slope in flood of ¹⁄₁₃₀₀₀, and of ¹⁄₁₂₅₀₀ in extraordinarily high floods.

From the sources of the Kagera river to the sea, on a length of 6350 kilometres, the Nile falls 2000 metres, or has a slope of ¹⁄₃₂₀₀. From Lake Victoria to the sea the length is 5535 kilometres and the fall 1129 metres, or the slope is ¹⁄₅₀₀₀.

[Table III] of [Appendix C]. gives the velocities of the river in flood and low supply, in metres per second and kilometres per day, and also the time occupied in traversing the different reaches. There are two breaks. The first is at Lake Choga and the second is at Lake Albert. As the Victoria Nile traverses the eastern arm of the many-armed and peculiar Lake Choga with a perceptible current, and as, moreover, the lake is very shallow, we may give some figure to the velocity and make it half that of the Bahr Gazelle which is ·20 metres per second and is considered perceptible. With a velocity of ·10 metres per second or 8 kilometres per day, the 80 kilometres of the lake would be traversed in 10 days. The time of traverse from Lake Victoria to Lake Albert would be 15 days. With Lake Albert it is very different. A reference to [Plate V] will show that it takes the Victoria Nile 5 months to fill up Lake Albert before the Albert Nile can carry off the waters of the Victoria Nile, gauge for gauge. Under these conditions it will be wise to stop at Lake Albert and begin a new calculation from this lake.