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CHAPTER 11.

THE WHITE NILE.

[Tlifl reader ivlio vmhcs to sttidy in detail the whole question of the Nile Basin, its floods, discharges of rimrs, schemes of

irngation, etc., etc., is referred to Sir William Garstin's invahmhle " Report on the Basin of the Upper Nile," I.O. Bluchooh, Egypt No. 2 (1904). Price 17s.]

Flood.

(i.)— INTRODUCTORY.

The White Nile and its tributaries form the life blood of the Sudan. The great river traverses it for 2,029 miles General, from south to north, receiving on its course through the country the Bahr El Ghazal, the Sobat, the Blue Nile, and the Atbara.

Of these four tributaries the Bahr El Ghazal joins the Nile out of the swamps from the west, whilst the other three join it from the east, bringing down the fertiUzing matter from the Abyssinian liills.

The rise of the Nile takes place during the summer, but the dates naturally vary largely at different points. The causes of the flood are, briefly, as follows : — The rains in southern Abyssinia cause the Sobat to rise about the middle or end of April. The yellowish-white water caused by this flood reaches Kodok the last week in April. The equatorial rains cause the Bahr El Zeraf and White Nile, above the Sobat, to rise about the end of May. The effect of the first rise is felt at Haifa about the 20th May. The Blue Nile begins to rise about this time, and brings the red fertihzing flood down to Khartoum about the 20th Jime, and to Haifa about the middle of July. The muddy Atbara flood (June to August) rises very rapidly after the Blue Nile, and causes the flood to attain its maximum about the end of August ; at this period the river is muddiest. The White Nile continues to rise slowly, and its effects (clear white water) are felt at Haifa till October, when it falls very slowly. The Blue Nile falls rapidly after the middle of September, and the Atbara has generally disappeared by October. The Sobat begins to fall at Nasser early in December.

The Bahr El Ghazal rivers rise shghtly in May. These soon subside, and the main floods take place in July and August.

The above is a description of an average year. An early maximum {i.e., about the middle of August) generally

means a low summer flood, and vice versa. The flood at its height moves at about 100 miles a day (below the Atbara).*

The above dates vary largely in accordance with the time and amount of rainfall in the upper valleys of the rivers. Of the flood water annually brought down by the rivers, about half now runs to waste into the Mediterranean Sea. The Aswan dam regulates and utilizes this to a certain extent, but a large proportion remains over. This it is proposed to utilize in the future for irrigating the Sudan by means of flood and catchment basins ; but the time is still distant when this surplus will be entirely devoted to this purpose.

Up to comparatively recent times the sources of the Nile were involved in mystery .f In ancient days many guesses were hazarded at their origin, some geographers maintaining that the Nile rose in the Atlas Mountains of Marocco ; others were positive that the Niger formed the upper portion of the great river. During the 17th and 18th centuries

it was held that the sources were to be found in the " Moimtains of the Moon." These have since been speculatively identified with the Ruwenzori Mountains between Lakes Albert and Albert Edward, and, if this theory is correct, the ancient geographers were not so far out.

It was left for Speke and Grant, in 1862, on a journey from the east coast, to discover that the great lake, now known as the Victoria Nyanza, was the main source of the White Nile. Sir Samuel Baker, in March, 1863, working up stream, discovered the Albert Nyanza ; but it was not till some time afterwards that the actual course of that portion of the river, now known as the Bahr El Jebel, was mapped and traversed. Lieutenants Watson and Chippendall, R.E., being the first, under Gordon in 1874, to lay down the actual course. During the ensuing years, this, the upper portion of the river, was several times blocked with sudd, and at the re-conquest of the Sudan from the Dervishes in 1898,

it was permanently blocked. An expedition under Major Peake, however, succeeded in clearing a chaimel in 1899- 1900, and there is no likehhood of the clear channel now existing being, except quite temporarily, blocked again.

* The flood discharge at Berber is 14,000 metres cube per second. _ t For full record of the history of the e-xploration of the Nile vide " The Nile Quest " by Sir H. Johnston.

Historical