Such in brief outline are the gigantic schemes which are now engaging the attention of the irrigation authorities of Egypt. Great as are the achievements of the past, they look almost petty before these visions of the future.
CHAPTER XII
THE SUDD
If the White Nile carried its waters in a channel in any way resembling that of the Blue Nile, there would be small cause for anxiety over the summer supply of Egypt. As far as Lado, indeed, the Bahr el Gebel, or Mountain River, as it is called, does flow with as good a slope and as sound a rocky bed as any Egyptian could desire. Then it enters upon the great plain which extends practically as far as Khartoum, but until Bor is reached it has not to encounter more than the ordinary troubles of a flat country. The swamps are still well above the summer level of the river, and the loss of volume is not great. At Bor, however, the real difficulties begin, and the ‘shorn and parcelled river strains’ miserably along for some 350 miles through the real sudd country. The river that leaves Lado in April or March with a volume of 600 cubic metres per second is reduced to less than half this amount by the time it emerges from the maze on the further side, and that, too, although it has nominally received at Lake No through the Bahr el Ghazal the drainage of a vast province.
Lake No is the remains of an inland sea which once covered all this desolate region. Gradually this lake became silted up with peaty deposits, and formed a series of swamps and lagoons through which the Bahr el Gebel from the south and the Bahr el Ghazal from the west wander in a series of loops and curves without any certain banks. The smallest rise in the level of the river floods an immense tract of country, and at all times of the year the sudd region is one gigantic evaporating pan. The Bahr el Ghazal, so far as any active contribution to the volume of the Nile is concerned, is practically lost altogether, though by spreading out over the marshes it fills a space which the Bahr el Gebel would otherwise occupy, and so helps to form a sort of reservoir, which prevents any rapid fall in the level of the White Nile.
All these swamps are covered with a dense growth of reeds and water-weeds. Of these, the most important is the papyrus, which grows in great abundance, and often reaches a height of 10 to 16 feet. Once the papyrus was common in Egypt, but now it is not found north of Abu Zeid, 190 miles south of Khartoum. In Europe it is not found, except on the river Anapo in Sicily, where, however, it does not attain anything like the same luxuriant growth. There are also great stretches of the reed called in Arabic ‘um soof,’ or the mother of wool. It is no wonder that the party sent by Nero to explore the river was intimidated by these interminable forests of papyrus and reeds, and turned back. No travellers have a good word to say for this country, unless they only pass through it extremely quickly. It is monotonous and desolate in the extreme, the air is always hot and steamy, and after dark mosquitoes rage in countless myriads.
As far as Shambe the banks of the river are fairly well defined, but there are numbers of breaches in them, through which the water spills into the marshes. In a distance of seventy-five miles Sir W. Garstin counted 129 of these breaches, usually about 4 yards wide; nearly all of these were on the eastern side. These channels are deeply cut with vertical sides, as if dug by hand, and the loss of water through them is very great. The marshes on the eastern side drain off into the Bahr el Zeraf, which takes off near Shambe, and, cutting off the corner, rejoins the Nile below Lake No. Greatly diminished by this loss, the Bahr el Gebel continues on its way, its bank being often nothing more than a line of papyrus separating it from large lagoons or dense thickets of reeds. As long as the channel is clear, tortuous and winding though it is, a great deal of water is able to pass; but under certain circumstances the channel becomes blocked by bars of solid vegetable matter, called sudd. Upstream of the obstruction the level rises, and, spreading out over the marshes, more and more water is lost in evaporation.
Sudd occurs both in the Bahr el Ghazal and the Bahr el Gebel, but it is of different kinds. The Ghazal sudd is very much less substantial than that of the Gebel. It is chiefly composed of masses of the smaller swimming plants, which grow in Lake Ambadi and other shallow lagoons on that river and its affluents. But on the Gebel the principal constituents of the sudd are the papyrus and the ‘um soof’ reed. Both these plants grow with their roots bedded in the soil below the shallow water of the lagoons. Strong gales are prevalent in these latitudes, and these loosen the roots, so that, if the storms are accompanied by flood, large masses of the plants are set free, and begin drifting over the lagoons. Quantities of earth remain clinging to their drifting roots, and thus they are driven backwards and forwards by the wind. The storms come generally just before the flood, and thus there is plenty of water for the reeds to float in. Eventually they are driven, whole acres at a time, into the channel of the river, and are carried down the stream. But the channel being very narrow and winding, they soon get caught up, and a block occurs. New masses come down, and these are sucked by the stream under the original block, till a dense mass is formed, sometimes as much as over 20 feet thick, and so solid that a man can walk over it. If left to themselves, these blocks may last a very long time, and cause the river to change its course; or else by increased pressure the block is burst, and a great wave passes down the river, which sweeps all other blocks away. Years of high flood are generally followed by a great deal of sudd.
It appears that the conditions on the river between Lake No and Shambe are much more favourable to blocking by sudd than they used to be. In 1840 Mehemet Ali sent a scientific expedition under D’Arnaud to explore the White Nile. At that time the main stream through the sudd country was much bigger and stronger. No mention is made of the Bahr el Zeraf at all, which looks as though it was of much less importance, at any rate. They noticed, however, a number of openings in the banks between the river and the swamps, some natural, but some artificial, made by the natives for fishing purposes. It is plausibly argued by Sir W. Willcocks that these openings were later widened by the natives to enable them to escape in their canoes from the slave-dealers, and then by the slave-dealers themselves, escaping in their turn from Government patrol boats. All these spills would drain into the Bahr el Zeraf, which gradually became a navigable stream in its lower part. In 1863 Sir Samuel Baker ascended the Bahr el Gebel without any difficulty; but in that year there was a very high flood and a great deal of sudd. Returning in 1865, Baker found the river north of Lake No considerably blocked. In 1870 Baker was unable to ascend the Bahr el Gebel with his expedition to Equatoria, and went by the Bahr el Zeraf. He cut through the sudd in that stream with prodigious labour, and had finally to cut a ditch through 2,000 feet of solid clay. Even then the Bahr Zeraf level was so much below that of the Bahr el Gebel that he could not get his boats through until he had dammed the Zeraf behind them so as to lift them up. In 1873 he says he found the canals much improved by the force of the stream. All this naturally contributed to weaken the power of the main stream and render it very liable to sudding.
In 1874, when the river was low, the sudd was cleared away by Ismail Pasha Ayoub, then Governor-General of the Soudan, and all through Gordon’s time in Equatoria there was free passage, but the channel had dwindled very much. The heavy flood of 1878 brought the sudd down again worse than ever, where it remained until cleared by Marno in 1880. It was in that year that Gessi, on his way back from his province, was caught and suffered such hardships in the sudd on the Bahr el Ghazal. He was only rescued by the appearance of Marno. Unfortunately, no record has been left of the methods which Marno employed in the work, but he spoke of it as quite an easy matter.