J31 CHAPTER VI.

SOUTH-EASTERN SUDAN.

(The So bat and tributaries, and country south of the Sobat and north of N. Lat. 5° between the Bahr El Jebel and Abyssinian frontier.)

Section 1. — Description of the Sobat and its Tributaries.

The Sobat rises on the Abyssinian plateau somewhere about east long. 36° and north lat. 7° 15', though its source River Sobat. has probably never been accurately determined, and flows generally from oast to west.

For the first 260 miles (approximately), as far west as the junction of the Pibor*, it is known by the Abyssinians as the Baro, by the Nuers as the Kir, and by the Anuaks as the Upeno ; from this point to its junction with the White Nile, at a point some 55 miles by river south of Kodok and 460 miles (approximately) from its source, it is called the Sobat.

In its descent from the plateau to Gambela, for the first 150 miles, it flows in a series of rapids through wooded, mountainous, and hilly country, in a rocky bed often not more than 40 yards wide. From Gambela to Finkio (15 miles) it increases in width to about 200 yards, but in the dry season is full of rocks, especially at the bends. Throughout the remainder of its journey to the Nile it meanders across an immense dead-flat alluvial grassy plain, varied here and there by extensive woods reaching down to the water's edge, but often nothing is visible for miles save swamp and grass with numerous termite hills, and but an occasional tree. During this part of its course its width varies as a rule from 150 to 300 yards, though occasionally it narrows to 30 or 40 yards in the marshy region between Balamkun and the Pibor.

Working up stream.J the banks are, as a rule, firm and dry for the first 150 miles from Sobat mouth, and numerous Banks.t villages are seen built actually on them. The left bank is usually higher than the right, and both banks are higher than the country in their immediate vicinity, and thus narrow swamps running parallel to the river exist well on into the dry season. These marshes are often drained by the natives through cuts in the banks in order to capture the fish in them. Above the village of Shwai the banks are alternately marshy and firm.

Both the Sobat and Baro, probably as far up-stream as Finkio, are navigable for steamers drawing 4 feet of Navigawater, from the middle of May till the end of December. About the middle of the latter month the appearance of "''ysandbanks makes navigation difficult, though it is probable a channel for small boats exists throughout the year.

Both the Sobat and Baro are fordable at fairly frequent intervals in the dry season eastwards of the Dinka Fords, country.

The current is generally estimated at from 2J to 3 miles per hour in flood ; in the dry season (February to May) Current, 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.

The water of the Sobat in flood is of a reddish-yellow colour, whilst that of the Baro is similar to the colour of Water. [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 f till the middle or end of January.

The Sobat reaches its lowest level about the end of January and commences to rise about the end of April or begin- Rise. [ ning of May.

Petherick in April (low water), 1862, estimated the discharge of the Sobat at 120 cubic metres per second. The Discharge, [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.

* Abyssinian boundary. t During the driest season of the year there is no difficulty in marching along either bank. Between Jtang and Nasser the best iToad is along tlie right bank.

t For distances along the Sobat, vide p. 152.