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.
Little is known of the state of the sudd during the years of the Mahdi
and the Khalifa; but in 1898 Lord Kitchener found the Bahr el Gebel
blocked by sudd immediately above Lake No; and about the same time
Colonel Martyr, coming from Uganda, was unable to penetrate more
than 20 miles north of Shambe for the same reason. As soon as the
Khalifa had been finally crushed, operations to clear the channel
were immediately undertaken. In the first three months a length
of 80 miles of river had been cleared, including 5 miles of actual
sudd in eleven blocks, besides three more blocks which broke away
of themselves. The blocks that came away of themselves represented a
very large amount of sudd. After one of them had burst, the floating
weed took thirty-six hours to pass a given point. The effect produced
by the sudd in damming up the river is illustrated by the fact that
when the third block, which was nearly 20 feet thick, was removed,
the upstream level fell 5 feet in four days, and all the swamps and
lagoons began to drain into the river.
The amount of labour was prodigious. At one place, owing to the
enormous masses of um soof and papyrus that kept pressing into the
river, no less than eleven clearances had to be made in one year. Five
gunboats and 800 dervish prisoners, besides officers and guards,
were employed. Sir W. Garstin gives an interesting description of
the methods by which the sudd was removed:
‘In the first place, the papyrus and reeds on its surface were
burnt (curious to relate, these green reeds burn readily when
the marsh is dry), and in a few hours’ time the surface of the
sudd was an expanse of blackened stalks and ashes. As soon as
the fire had died down, gangs of men were landed from the steamer
and employed in cutting trenches on the surface of the sudd. These
trenches averaged from 0·60 to 0·80 metre in width, and from 1 to
1·25 metres in depth—_i.e._, as deep as the men could work. The
surface was thus divided into a number of rectangular blocks some
3 metres by 4 metres. To these blocks were attached, one by one,
steel hawsers and chains. This done, the steamer downstream went full
speed astern. It invariably took several pulls to detach a block,
and in some instances as many as nine were necessary. Both hawsers and
chains kept constantly breaking, although the former were calculated
to stand a strain of 35 tons per square inch, and the latter as much
as 60 tons. As soon as a block was detached from the mass, it was
allowed to float downstream. It was curious to see the green reeds and
papyrus which had been confined beneath it reappear on the surface of
the water. A horrible stench prevailed from the rotting vegetation.’
In 1900-1901 four more blocks were removed. An experiment was
made to break up one of the blocks by means of explosives, but
it was found that the sudd, though very solid, was too elastic,
and the only effect was to make large holes in it and no more. The
old method had to be once more resorted to. By the end of 1901
only 23 miles of the channel remained uncleared, but this proved
to be the most difficult of all. One block was actually 7 miles in
length. Portions of the sudd had rotted, and, sinking to the bottom,
completely filled up the channel, so that there was no stream at all,
and it was impossible to tow pieces away and float them downstream
by the usual process. To get up the river it is still necessary to
go round by a series of lagoons, in which navigation is difficult,
and operations have been suspended for the present.
The sudd in the Bahr el Ghazal was much easier to remove, and great
progress has been made, so that now the whole of that river is free,
and boats can even ascend the Jur River to Wau.
It is very difficult to ascertain the precise effect of the removal
of the sudd on the water-level in Egypt. But it is certain that as
each block was removed a quantity of water drained off the marshes
and helped to diminish the fall of the river in summers of very
small supply. Most of this water, spread out over a large surface,
must otherwise have been evaporated and lost altogether. There can
be no doubt that the improvement of the channel has been a permanent
gain to Egypt of a very substantial kind, to say nothing of the
advantage to the Soudan from the opening up of such an important
line of communication. Those who laboured at the task deserve the
highest praise. The river was so low that all communication with
Khartoum was cut off for several months, and transport of supplies
was always difficult. Besides this, the climate is always unhealthy,
and the mosquitoes at night are almost beyond endurance.
Under present conditions it will require constant care and
watchfulness, especially in years of high flood, to prevent the sudd
from frequently obstructing the river. But if the danger is to be
permanently removed, the main channel must be so much improved by
widening and deepening it that it will carry a greater volume. This
will at the same time prevent the water from being dissipated in the
marshes, and diminish the chances of any obstruction. The necessity
for some work of this kind, if there is to be a reservoir at Lake
Albert or Lake Victoria, has already been referred to. The clearing
of the sudd is only the essential preliminary to the greater scheme.
One point remains to be noticed. Under the old basin system in Egypt
there could hardly be too high a flood, nor did a low summer Nile
create any extraordinary difficulties when there was so little summer
cultivation. But with perennial irrigation a high flood becomes a
matter of supreme anxiety, and the preservation of its dykes is the
anxious care of every village. On the other hand, all the schemes
for reservoirs aim at increasing the summer supply. If the Bahr el
Gebel was trained so as to bring down more water in summer, it would
also bring down more in flood, though the swamps would still act as
an escape for the waters beyond a certain rise. It might therefore
become a matter of great importance to Egypt to actually diminish
the supply during the flood, especially as year by year more of the
basin land is converted to perennial irrigation. Regulators at Lakes
Victoria and Albert would serve in some degree for flood protection
as well as for storage against summer use. It is calculated that the
complete closing of the outlet of Lake Victoria at the Ripon Falls
would only raise the surface of the lake 20 inches in a year. But
it would be far more effective if some of the flood-waters of the
rivers—_e.g._, the Blue Nile and the Atbara—which are fed by
the rains of Abyssinia could be intercepted before they reached
Egypt. A large irrigation during the flood and early winter along
the Blue Nile might indeed actually lengthen out the flood in Egypt,
whilst depriving it of danger through excess at any one period.