Current.The current is generally estimated at from 2½ to 3 miles per hour in flood; in the dry season (February to May) it is not more than 1 mile per hour.
The current of the Baro in flood combined with the sharp bends and occasional narrowness of the river render navigation difficult in places.
Water.The water of the Sobat in flood is of a reddish-yellow colour, whilst that of the Baro is similar to the colour of the Blue Nile or Atbara, being like them derived from the Abyssinian hills.
The sources of supply of the Sobat are:—
(i) The southern Abyssinian hills and the rains which drain westward from them.
(ii) The vast marshes which lie between the White Nile and the Abyssinian hills, which keep the Pibor bank-full till the middle or end of January.
Rise.The Sobat reaches its lowest level about the end of January and commences to rise about the end of April or beginning of May.
Discharge.Petherick in April (low water), 1862, estimated the discharge of the Sobat at 120 cubic metres per second. The same authority on 5th June (after the rise had begun), 1863, reckoned the discharge at 233 cubic metres per second. For later calculations, vide footnote [p. 111.]
Adura (loop of the Baro).A large loop of the Baro takes off from the main stream near the village of Gadjak[88] on the south bank, and enters the Baro again some 14 miles to the east of the Sobat-Pibor junction. This river is known by the natives as the Adura. Although seemingly a large and important loop, it was found to be quite unnavigable in July, when the river was nearly full, owing to the existence of a large number of sand-banks and islands. Another loop south of the Adura is said to be formed by a stream known as the Mokwai. This has a very insignificant exit from the Baro, only some 5 or 6 miles to the east of the Adura exit, but is reported in its lower reaches to be an important stream in flood time, possibly after it is joined (as it is said to be) by the Bela river. The combined stream enters the Pibor, by native report, and, in that case, the river, followed by Major Capper for some 20 miles of its course, is probably this one.
Tribes — Shilluks.From the junction of the river Sobat with the White Nile, for the first 30 or 40 miles up-stream, both banks of the Sobat are occupied by the Shilluks. For full description of this tribe, see [Chap. VIII.]