Projects.
31. =Projects.=--No account of the Nile in 1904 would be complete
without an enumeration and slight examination of the projects before the
public for the provision of sufficient water to the Nile in times of low
supply to insure the perennial irrigation of the whole of Egypt; to
utilise these perennial waters by converting basin tracts into
perennially irrigated ones; to protect the country from the dangers
accompanying high floods; and to permit of the reclamation of the low
salted lands of Lower Egypt which border the Mediterranean sea.
Egypt has a total irrigable area of 6¹⁄₄ millions acres. Of this area,
¹⁄₄ of a million acres, which are to-day inundated in flood and lie
along the edge of the deserts, must continue to be inundated in flood
for all time, to prevent the sands of the desert from spreading over the
Nile Valley. Their value is £5,000,000. Four million acres are
perennially irrigated. They have a mean value of £55 per acre, and have
a total value of £220,000,000. Of the remaining two million acres,
two-thirds are irrigated only in flood and one-third is not irrigated at
all. These 2 million acres have a mean value of £25 per acre, and are
worth £50,000,000. The land of Egypt may be considered as worth
£275,000,000 to-day. If it were possible to perennially irrigate the 2
million acres which are without such irrigation, their value would be
increased by £30 per acre, or by £60,000,000.
The problem before us is how to provide perennial irrigation to these 2
million acres and so add £60,000,000 to the wealth of the country.
It has been calculated that each milliard of cubic metres of water
stored in reservoirs situated in Egypt itself is sufficient to insure
the conversion of half a million acres from flood to perennial
irrigation. Egypt therefore requires reservoirs capable of storing 4
milliards of cubic metres of water.
In Mehemet Ali’s time, the great preoccupation of the Government was the
pressing on of the cultivation of cotton, and as this crop needed
perennial irrigation, the securing of an abundant supply of water all
the year round was the problem of the day.
The fame of the ancient Lake Mœris had made a profound impression on the
mind of Mehemet Ali, and he urged on his chief engineer the necessity of
undertaking similar works. Linant Pasha first set himself to discover
the site of the ancient lake, and then estimated roughly the cost of
reconstructing it, but considered the cost prohibitive. He recommended
Silsila as a suitable site for a weir and a canal head. The failure of
the Barrage discouraged the Government from undertaking new works and
the question dropped. In 1880 Count de la Motte proposed a dam at
Silsila and a reservoir to the south of it. He also proposed putting a
capacious depression to the east of Kalabsha in communication with the
Nile by the aid of a dam at Kalabsha.
About two years later Mr. Cope Whitehouse suggested utilising the Wadi
Rayan depression as a reservoir. This depression had been already
mentioned by Linant Pasha in his book and located by him on his
hydrological map. Financial difficulties prevented Sir Colin
Scott-Moncrieff from immediately considering the question of reservoirs.
The success of the Barrage repairs in 1887 however gave new life to the
question of reservoirs and Sir Colin Scott-Moncrieff deputed Col.
Western to give scope to the suggestion made by Mr. Cope Whitehouse, to
make plans of the Wady Rayan and the deserts between it and the Nile, to
find out the capacity of the reservoir, and see if it could be utilised.
Col. Western’s report, plans and estimates were printed by the Egyptian
Government in 1888. At the same time I was deputed to examine the other
projects of Count de la Motte. In 1889 and 1891 I reported unfavourably
on them, because I could find no depression near Kalabsha to put in
communication with the Nile, and could find no rock at Silsila on which
to build a dam. The Bergat Takham pan was the only depression near
Kalabsha which could have been used as a reservoir and it was over 100
metres above the level of the Nile flood; while both in the Silsila pass
and the Silsila gate I bored for rock and was everywhere still in sand
10 metres below the level at which the existence of rock was assumed by
the Count’s engineers. On my report reaching Cairo, M. Prompt proposed
using the trough of the Nile itself at Kalabsha as a reservoir in place
of the depression which did not exist. Col. Western left the country in
1890 and I became Director General of Reservoir Studies. M. Prompt had
supposed that rock could be met with at Kalabsha at a depth of 4 metres
below low-water level. I could not find it at a depth of 26 metres.
After sounding and boring at every possible site on the Nile and
surveying, boring, and levelling in the desert between Wadi Halfa and
the Fayoum, I submitted my report in 1894, proposing an open dam at
Assouan of a type which I trusted would meet the requirements of a Nile
reservoir dam. Sir William Garstin approved of the site and the design,
and the dam was built between 1898 and 1902 with Mr. Maurice Fitzmaurice
C.M.G, as resident engineer.
The Assouan Reservoir at its present level contains one milliard of
cubic metres of water which will suffice for the conversion of half a
million acres to perennial irrigation, adding £15,000,000 to the wealth
of the country. But though the dam was only completed at the end of
1902, already the whole of the water has been devoted to special tracts,
and the Government is reluctantly compelled to refuse all applications
for water.
32. =The raising of the Assuân dam.=--Egypt already possesses the germ
of all the storage works she needs. Six years ago a few far-seeing men
saw clearly what all of us understand to-day; but among the few, no man
had greater faith in the future of the country than Sir Ernest Cassel.
The Assouân Reservoir project had been lying buried for four years in
official pigeon holes, when in 1898 Sir Ernest came forward with the
funds, and with Sir John Aird & Co., as contractors, and Sir Benjamin
Baker as Consulting Engineer, undertook to complete the Assouân dam and
the Assiout weir by December 1903. The Egyptian Government, advised by
Sir William Garstin, accepted his offer, and received the completed
works by December 1902.
The Assouân dam is a granite structure 2,000 metres long which crosses
the head of the Assouân cataract of the Nile in one continuous straight
line. The dam is pierced by 140 under sluices of 7 metres by 2 metres
for passing floods, and by 40 upper sluices of 3¹⁄₂ metres by 2 metres
for passing the high level water of the reservoir. The sluices are
regulated by “Stoney” gates worked by winches at the roadway level.
While the red, muddy waters of the Nile flood are pouring down the
river, the whole of the sluices are open and the river discharges itself
through them without parting with its silt. This is the real object of
the sluices, for if the dam were solid and the river forced to flow over
the top, the reservoir would soon be filled with deposit and
obliterated, while Egypt, deprived of this rich mud, would be
considerably the poorer. This is the great feature of the dam. While the
dam holds together, the reservoir will be free of silt.
When the turbid flood has passed and the comparatively clear winter
supply of the river has begun to arrive, the sluices are gradually
closed and the reservoir filled. Beginning about the 1st December, the
reservoir is filled in 100 days. It will ordinarily be full on the 1st
March. No additional water is needed for irrigation between March 1st
and May 1st as the river naturally has enough for the requirements of
the area at present under crop at this season. As the area under
perennial irrigation will be gradually increased, the demand for water
for the new lands will begin about the 1st of April. The demand
increases through May and June, and the reservoir will then be aiding
the river with its supplement. If the flood is very late, water may be
required from the reservoir till the 10th July; if the flood is early no
water will be needed after the 20th of June, as in 1903, the first year
of the reservoir. The earlier the flood the more effective the
reservoir. By the time the flood has begun to get turbid, the under and
upper sluices will all be open and the muddy waters of the Nile will
sweep through the dam without impediment.
The dam has worked for two years and given satisfaction. When the Nile
was at its lowest in May 1903, the natural discharge of the river,
supplemented by all the subsoil infiltration water which enters the
river between Assouân and the sea, was 400 cubic metres per second. The
reservoir was adding 200 cubic metres per second to the supply, raising
the total supply available for irrigation to 600 cubic metres per
second. The reservoir was supplying one-third of the water which was
being utilized in Egypt. This water will suffice for an increase to the
perennially irrigated area of ¹⁄₂ million acres.
At the time of designing the dam it was intended that it should be of
such a section that it could be raised 6 metres in height and hold up
another milliard of cubic metres of water. Such an operation, if
performed to-day, would mean: the whole length of dam being raised 6
metres, the winches working the sluice gates being raised 6 metres and
provided with new wire ropes; and new copings being given to the
parapets. It would necessitate two more locks and three more lock gates,
and nothing else. The expenditure incurred would be about £500,000.
33. =The Wady Rayan Reservoir Project.=--When the Assouân dam will have
been raised, we shall be standing on the threshold of what it will be
able to do. The projected Wady Rayan reservoir, or the modern Lake
Mœris, will be well able to supply the two remaining milliards of cubic
metres of water when working in conjunction with the Assuân Reservoir.
The great weakness of this projected lake has lain in the fact that _by
itself_ it could give a plentiful discharge in April and May, less in
June, and very little in July, and it was for this reason that in my
report of 1894 to the Egyptian Government I had reluctantly to recommend
that it be not carried out. But when the Assouân reservoir is capable of
supplying two milliards of cubic metres of water it will be possible to
utilise the Mœris Lake to its utmost capacity. The Assouan Reservoir,
being high above the level of the Nile can give its supply at the
beginning or end of the summer; it can give it slowly or with a rush;
while the projected Lake Mœris, being directly in communication with the
Nile, and only slightly above low Nile level, its discharge would depend
entirely on the difference of level between it and the Nile, and
consequently as the summer advanced its level would gradually fall and
the lake would not be able to give at the end of the summer a quarter of
the discharge it could give at the beginning.
[Illustration: PLATE XV
PROPOSED WADI RAYAN RESERVOIR
SHOWING THE FAYOUM
_All R. L.^{s} in metres, above or below mean sea._
+ -
_Desert._
_Scale 1 : 500,000_
Lith. Sur. Dep. Cairo.]
But let us imagine that the reservoir and the lake are both completed
and full of water, and that it is the first of April. Lake Mœris will be
opened on to the Nile and give all the water needed in that month, while
the Assouan Reservoir will be maintained at its full level. In May, Lake
Mœris will give nearly the whole supply and the reservoir will give a
little. In June the lake will give little and the reservoir much; while
in July the lake will give practically nothing and the reservoir the
whole supply. Working together in this harmonious manner, the reservoir
and the lake, which are the true complements of each other, will easily
provide the whole of the water needed for Egypt.
The Wady Rayan is a depression in the deserts to the south of the Fayoum
and separated from the Fayoum by a limestone ridge. In 1888 Col. Western
recommended it very strongly as a reservoir. In this he was supported by
Col. Ross, the first Inspector General of irrigation. On Col. Western’s
leaving Egypt, the study was entrusted to me, and Messrs. Hewat and
Clifton deputed to make a final project. The Wady Rayan project, with
its plans and estimates, was published by the Egyptian Government in
1894. As I said before, I was reluctantly compelled to reject its
adoption owing to the one radical defect already described. That defect
will have been completely removed by the completion of the Assouân
Reservoir, when it will be possible to undertake the construction of the
modern lake Mœris.
The question of Lake Mœris has interested the world for centuries. For
the ancients it was one of the world’s seven wonders. Sir Hanbury Brown,
in his book on the “Fayoum and Lake Mœris,” has collected all the
information available about the lake, and after a thorough examination
of the question has declared in favour of the Wady Rayan being converted
into a modern Lake Mœris.
Herodotus, writing about B.C. 450, was the first to describe the lake:
“Now the Labyrinth being such as I have described, the lake named that
of Mœris, causes still greater astonishment, on the bank of which the
Labyrinth was built.
“The water in the lake is not derived from local sources, for the earth
in that part is excessively dry and waterless, but it is brought in from
the Nile by a canal. It takes six months filling and six months flowing
back. During the six months of the return flow, it yields a talent of
silver every day to the treasury, and during the flow twenty minæ for
the fish.”
Strabo, writing in B. C. 20, remarks: “It has also a remarkable lake
called the Lake of Mœris, large enough to be called a sea, and
resembling the open sea in colour.
“Thus the Lake of Mœris is, from its size and depth, capable of
receiving the overflow of the Nile at its rising, and preventing the
flooding of houses and gardens; when the river falls, the lake again
discharges the water by a canal at both mouths, and it is available for
irrigation. There are regulators at both ends for controlling the inflow
and outflow.”
Diodorus Siculus, writing at the same time, says:--“King Mœris dug a
lake which is amazingly useful and incredibly large. For as the rising
of the Nile is irregular, and the fertility of the country depends on
its uniformity, he dug the lake for the reception of the superfluous
water, and he constructed a canal from the river to the lake 80 furlongs
in length and 300 feet in breadth. Through this he admitted or let out
the water as required.”
At one time there was much discussion as to what was Lake Mœris, but
since the publication of Sir Hanbury’s book there can be but one
opinion. The lake covered the whole of the modern Fayoum below the level
of the contour which is 22¹⁄₂ metres above mean sea level. The common
Nile shells are to be met in myriads at any point on this contour round
the Fayoum that one cares to look for them. The ordinary high flood
level of Kushesha basin to-day is 26¹⁄₂ metres above mean sea. In
Amenemhat’s time, which was 4,000 years ago, the level was 4 metres
lower, or at 22¹⁄₂ metres above mean sea. This was the highest possible
level the lake could have attained in his day. In the course of time the
level of the Nile valley rose by about 10 centimetres per century, but
the frequent occasions on which the canal was kept closed during poor
and low floods gradually silted up the channel and made it less
capacious. As there are no Nile shells above the contour of 22¹⁄₂ metres
above mean sea (except a few on the south side of the lake which have
evidently been blown up by the north west winds in sand drifts) it is
evident that the gradual silting up of the channel more than kept pace
with the rising level of the Nile. Eventually the silting up exceeded
the rise, and that at an accelerated rate, the canal became weaker and
weaker, and the Fayoum Province gradually occupied the site of the lake.
Lake Mœris had lasted over 2,000 years.
The connection between the Nile and the germ of the future Lake Mœris
was in existence in King Menes’s time, as I have been informed by
professor Sayce, but it was King Amenemhat, of the XIIth dynasty, who
widened and deepened the canal, cleared away the rocky barriers, and
converted the trifling lake of King Menes’s time into the mighty inland
sea which controlled the highest floods of the Nile. Those ancient
Pharaohs were giants in hydraulic engineering. They were, moreover, as
wise as they were courageous.
Sir Hanbury Brown has well described the action of the lake. It had a
surface of 2,500 square kilometres, and being drained back into the Nile
and kept at a low level it was able to take from a very high flood 20
milliards of cubic metres of water. It was quite capable of reducing a
very high flood to moderate dimensions; and if injudiciously or
maliciously opened in a low flood, it was capable of depriving Lower
Egypt of any flood irrigation at all; and in those days they had
practically no irrigation except flood irrigation.
The Wady Rayan, as already stated, is a depression in the Lybian hills
immediately south of the Fayoum. It has, at a level of about 29 metres
above the sea, a surface of 700 square kilometres, or about one quarter
the area of the ancient lake. Like the ancient lake, the lowest point of
the Wady is 41 metres below sea level. When filled with water the
greatest depth will be 70 metres. The uppermost four or five metres only
will be utilised annually, or some 3 milliards of cubic metres of water
out of a total volume of 20 milliards. Just as the great size of the
ancient lake was of inestimable value to a work whose principal use lay
in moderating high floods, so the smaller area of the modern lake will
render it far more useful as a work for feeding the low Nile. This lake,
will render no mean aid in time of dangerous floods, but, in its early
years, its main use will be the provision of water in summer. It will
supply the two milliards which are needed to convert the whole of Egypt
from basin to perennial irrigation.
In my book on “The Assuân Reservoir and Lake Mœris” I have worked out
the cost of the project and estimated it at £2,600,000.
The rates I have allowed for the excavation work are considered too low
by some critics. If the earthwork in the Nile Valley had to be excavated
within 30-day rotations as on the running canals, I should be the first
to agree; but the work will last three years and the contractors will be
able to concentrate all the spare labour of the country on the works
when demand for labour is slack, and in this way the rate of P.T. 3 per
cubic metre which I have allowed will be found to be ample. In the hill
of salted marl it will be possible to employ the American system of
excavating by the aid of water issuing from nozzles under pressure. By
this method it will be possible to do much work at P.T. 2 and P.T. 3 per
cubic metre as it is done in America. I have allowed P.T. 5 per cubic
metre. To this hydraulic pressure work the salted marls will be
specially suited, and indeed the recollection of the ease with which
Amenemhat dug his canal though this very material lasted long in the
memory of Egyptians. Some 1,600 years after the canal was excavated,
Herodotus was informed that the excavated material was thrown into the
canal and transported by the running water. A 12-inch pump on the Yusufi
canal lifting water on to the top of the hill, a number of spade men
helping the water as it coursed down the hill and leading the liquid mud
along wooden troughs into side ravines and depressions, and a steep
slope on the western half of the hill where the rock had been blasted
away would soon remove all the material required at a very low cost. I
have allowed P.T. 10 per cubic metre for the soft limestone. Here it
will be easy to work on a vertical face of some 7 metres, blast out the
rock, carry it away on four lines of railway running down hill, deposit
the rubble on the desert; and as each 7 metres depth is completed, to
begin the next 7 metres in depth in the same way.
In my 1894 Report I had anticipated difficulties with the canal running
through the salted marl. Since then I have thoroughly inspected the
ravines in the Fayoum and seen the El-Bats ravine where it cuts through
many kilometres of this very salted marl. The sides are absolutely
vertical and deposits of mud and self-sown tamarisk bushes protect the
vertical sides at places where the running water is nearly touching the
marl. Such natural protection will be far superior to the masonry lining
I proposed and far more effective. It will moreover cost nothing.
[Illustration: PL. XVI.
WADI RAYAN RESERVOIR
LONGITUDINAL SECTION OF PROPOSED CANAL
_Horizontal Scale 1 : 150.000_
_Vertical Scale 1 : 600_
LONGITUDINAL SECTION OF THE FAYOUM]
To those critics who suggest that the waters of the lake might become
salted or leak into the Fayoum I have to reply as follows: When the old
Lake Mœris, or the present Fayoum, was full of water and 63 metres
higher than the bottom of the Wady Rayan, and remained so for thousands
of years, there was no question of the waters having become salted or
having escaped into the Wady. The Wady was as dry as it is to-day and
the great inland sea was always fresh. If there had been any serious
infiltration from the ancient Lake Mœris into the Wady Rayan, there
would have resulted a lake which could not have escaped the notice of
the numerous travellers who visited the lake. No mention was ever made
of such a lake. This body of water moreover would have been inhabited by
fresh-water animals whose remains would have strewn its shores. No such
remains are to be seen to-day. If therefore the ancient Lake Mœris with
a head of 63 metres on to the Wady Rayan could not leak into the Wady,
it is not likely that the Wady Rayan reservoir with a head of from 27 to
29 metres on the Garak side of the Fayoum will leak into that part of
the area covered by the ancient lake. Any leakage into the Lake Kurun
side is never contemplated by anybody, since many kilometres of compact
limestone lie between the Wady Rayan and it, while about one or two
kilometres of the same limestone lie between the Wady Rayan and the
Garak depression.
34. =Lake Albert reservoir project and project for training the Albert
Nile and the Zeraf River.=--If we wish not only to irrigate the whole of
Egypt, but to include the Sudan in the sphere of operations we must
regulate the supply issuing from Lake Albert Nyanza and ensure its
passage through the great swamp regions. To my mind no work in the Sudd
regions will be of any substantial value unless the Albert reservoir dam
is first built. Tabulating the information collected in the gauges and
discharge tables we may state that the discharge of the Albert Nile in
cubic metres per second between the 15th January and 15th May was as
follows in:--
=1901= =1902= =1903= =1904=
Discharge at Gondokoro 600 600 700 1000
Discharge above Sobat mouth 300 300 350 435
In 1861 the discharge at Gondokoro was as low as 500 cubic metres per
second. It will be seen that, in spite of the great waste, there is an
increase at the northern end of the Sudd region even under present
conditions when the discharge at the south end is increased in the
interval between the 15th January and 15th May. The water which enters
the White Nile during these months represents the summer contingent of
the White Nile to the Nile in Egypt.
Now though an increase in April at the south end of the Sudd region is
felt at the north end, no such increase is felt in September and
October, and the reason has been given in Chapters II and III.
In April the Sobat river is discharging practically nothing, and the
whole supply available in the Albert Nile can pass down the White Nile
past the Sobat mouth. In September the Sobat river may be discharging
750 to 1,000 cubic metres per second, and as the White Nile cannot
discharge the combined waters of the two rivers, the water of the Albert
Nile is headed up and accumulated in the lowlands between Lake No and
the Sobat mouth. This is greatly to the advantage of Egypt, for it is
the discharge at the head of the White Nile between January 15 and May
15 which decides the White Nile contingent to the summer supply of the
Nile in Egypt, and the greater the quantity of water above the head of
the White Nile, in the absence of a regulator or barrage at Wadelai or
Dufilé, the better the summer supply of Egypt. After the abnormally high
flood of 1878, when Gordon was up the Nile, so great was the
accumulation that the discharge at Assuân never fell below 1500 cubic
metres per second in the summer of 1879. The Barrage was not regulated
upon and yet all the Lower Egypt canals were full of water, and the
cotton crop of Egypt for that year was quite abnormal for the seventies
of the last century.
Now an expenditure of between £400,000 and £1,000,000, say £800,000,
could secure a regulator for Lake Albert at any point between the outlet
and Dufilé. Such a regulator would insure 1200 cubic metres per second
every year to the Albert Nile at Gondokoro between the 15th January and
the 15th May. With this supply insured, the training works in the Sudd
region would soon begin to affect the discharge at the north end of this
region where the White Nile begins.
The way in which this work of training should be carried out has been
admirably laid down in page 174 of Sir William Garstin’s Report. “Alter
the flood conditions of the Albert Nile (Bahr-el-Gebel) as little as
possible, let the excess flood water escape on both sides, but keep the
summer supply in its channel.” This is, to my view, the soundest
statement from an engineering point of view in the whole report.
Hitherto we have always assumed a vast expenditure for keeping the flood
supply in one channel; but with our attention devoted to the summer
channel, we should have before us all the advantages of summer training
works without any fear of inundations. The very wildness of the regions
would be in our favour. To be able to train a river in summer without
any nervousness about floods, is given to few engineers. I had never
thought that any good thing could come out of the sudd region, but
looked at from this point of view, we can, even in this inhospitable
waste of waters, confirm Shakespeare’s saying that “there is some soul
of goodness in things evil.”
The Lake Albert reservoir could easily insure 1200 cubic metres per
second every year between the 15th January and the 15th May. To pass
through the Sudd regions as much as possible of the 1200 cubic metres
per second received at Gondokoro, the following works would be
necessary:--
The first work to be done would be the removal of sudd block No. 15
which for 37 kilometres south of Hillet-el-Nuer has turned the Albert
Nile out of its course. The importance of this is strongly insisted on
by Sir William Garstin on page 55 of Appendix VI of his Report, which is
the very last thing he wrote. With this block removed, the Albert Nile
would be given a good opportunity of working out its own salvation.
The next point is one to which I attach the greatest importance. Indeed,
I look upon it as the key of the whole region. The Albert Nile enters
the south-east corner of Lake No and almost immediately afterwards
leaves its east corner. Now Lake No is the final evaporating basin of
the Bahr-el-Gazelle, probably the most unsatisfactory river in the whole
world; and it is open to doubt whether in a year of deficient rainfall
on its own catchment basin and a year of good supply down the Albert
Nile, it does not evaporate a considerable quantity of the water of the
Albert Nile. If the discharge of the Albert Nile north of Hillet Nuer
was brought to 450 cubic metres per second in April, this lake might
waste much of it. Such being the case, a cut of a maximum length of some
5 kilometres should be dredged south of the south-east corner of the
lake, and the waters of the Albert Nile separated from those of the
Gazelle. A cheap wooden lock and regulator would allow boats to pass,
and take in any water from the Gazelle river when it had it to give.
The maximum water we have to deal with is zero in summer and 40 cubic
metres per second in flood. If the Albert Nile were separated from the
Gazelle, it might be found that the waters of the Gazelle river found
their way into the Albert Nile through that mysterious and
unsatisfactory river the Lolle. Some use might even be found for it. I
have, since I wrote this, been informed by Capt. Lyons that Marno in
1881 proposed this cut round the south-east corner of Lake No. (Pet.
Mitheil, 1881, page 425 and plate 20).
The Albert Nile to-day at Hillet-el-Nuer is capable of carrying 450
cubic metres per second. North of Hillet-el-Nuer, the Albert Nile has a
mean width of 75 metres, but owing to want of training and papyrus
swamps, the discharge dwindles down to 320 cubic metres per second. The
Albert Nile has in this reach a very good section indeed and by
beginning with the west bank and dredging round corners and closing
spills by dredged earth, an improvement of section and slope, backed up
by a permanent discharge of 450 cubic metres per second at
Hillet-el-Nuer, might speedily result in this very discharge of 450
cubic metres per second being obtained south of Lake No. We are here in
such swamped land that percolation would be practically zero. There are
only 200 kilometres of channel with all its curves, or 160 kilometres of
trained channel to work at, in which 75 per cent of the work is to hand;
and we have to confine our attention to the low supply without worrying
over the flood supplies.
Now the Bahr-el-Zeraf could be made capable of carrying 150 cubic metres
per second by an improvement of the inlet at Baker’s channel and by
dredging north of Ghaba Shambe, as will be seen by examining the
measured discharges of the Bahr. With the Bahr-el-Zeraf carrying 150
cubic metres per second and the Albert Nile carrying 450 cubic metres
per second, we should have ensured 600 cubic metres per second. As time
went on, improvements in the channels would make themselves felt, as
they are even doing to-day, and we might even have 700 and 800 cubic
metres per second at the head of the White Nile below the Sobat mouth.
We must always remember that it is assumed that the lake Albert
reservoir dam has been constructed and a supply of 1,200 cubic metres
per second assured at Gondokoro from January to May. If the Sobat river
were capable of regulation downstream of the Pibor marshes, we might get
an increase from that direction as well. The possibility of a good site
for a reservoir upstream of Nasser is very great. The Nasser gauge rises
and falls so slowly that there must be very great natural accumulations
of water upstream of it, which might be improved. The question of
quality needs study.
The discharge of 435 cubic metres per second, which the rivers in their
present state, aided by the Lake Albert reservoir, could deliver into
the White Nile, would thus see itself gradually increased to 500, 550,
and 600 cubic metres per second and even more, and would enter the White
Nile past the Sobat mouth in February, March, April and May. During
these months the whole of the supply would pass down the White Nile
without throwing backwater on the rivers. Later on, when the Sobat river
came down in flood and filled up the channel of the White Nile, the
Albert Nile would have its waters reduced at the Albert regulator, and
the waters of Lake Albert would again be stored for the day when the
Sobat floods had fallen and the White Nile channel was free and ready to
take in the waters of the Albert Nile.
While I had contemplated the training of the flood waters of the Albert
Nile through the Sudd regions I had estimated the cost at £100,000 per
annum, for 25 years, or at £2,500,000. Now, however, that Sir William
Garstin has shown how we need only attend to the summer supplies, the
sum may be reduced to half the former figure or to £1,200,000, and be
more than ample. With £2,000,000 devoted to the Lake Albert reservoir
and the training works in the Sudd region, the summer supply of Egypt
and the northern Sudan would be put on a firm base.
Dr. Schweinfurth, the eminent African traveller and savant, was the
first to call the attention of the Egyptian Government to the necessity
of closing the spills from the White Nile to the north of Gondokoro, and
so beginning the training of the river. He very rightly said:--“Many
years would elapse before the desired result would be obtained by the
strengthening of the banks, but the works would be increasingly felt
every year in Egypt as the works progressed.”
35. =Flood protection for Egypt.=--In paragraph 30 it was stated that
the floods in the Delta or in Lower Egypt can rise to a height of from 2
to 3¹⁄₂ metres above the level of the country. Such floods are really
dangerous and means should be found for moderating them.
The Wady Rayan reservoir, when converted into the modern Lake Mœris and
acting as a reservoir, will have one great advantage, it will be able to
lower a high flood 30 centimetres for 50 days. This will give relief to
the Nile, a relief which will be much appreciated by the whole country
from Beni Suef to the sea, and especially by Cairo.
I have already stated that the Damietta branch is especially dangerous
and unfit to act as an escape under existing conditions. That branch
could be regulated on at its head and treated like a canal. Thanks to
Sir Hanbury Brown’s initiative the Barrages can be regulated on in flood
as well as in summer, and by lowering the supply in the Damietta branch
and turning the surplus down the Rosetta branch, the latter would become
the flood escape of the Nile. It might be trained as Mr. Eads suggested
that rivers should be treated.
Mr. Eads’ argument is very clear. He insists that rivers eat away their
banks in places, not owing to the direct action of the water but by the
alterations in the velocity of the current. When the river water is
charged with sediment to its full carrying capacity it cannot take up
more unless the rate of current be increased. If the channel be nearly
uniform the river water cannot eat away any of its banks. If, however,
the channel is varying, the silt deposits in the wide sections, and the
water, free of some of its sediment, is ready to eat more. It is this
alternate dropping silt and eating away of earth which does the harm. To
treat the Rosetta branch according to Mr. Eads it would be necessary to
fix the top width to be worked to, at say 550 metres. The river could be
brought to this uniform top width by building light inexpensive
permeable spurs on the sandy shoals. The land between the spurs would
become cultivated and such river training would pay the Government,
which taxes all cultivated land; it would even pay handsomely for any
company to undertake the work once the rule about foreshores was
understood. The Government would, however, always succeed; when it could
not sell, it could always tax. Such training would permanently lower the
flood.
In addition to the above it would be necessary to complete the system of
spurs begun in 1884, and to throw back the banks as already recommended.
It has been estimated that the completion of this work would cost
£900,000 for spurs and banks, while the training works would pay for
themselves in addition to greatly improving the channel and lowering the
level of the flood.
It may be humiliating to make the confession, but from B.C. 2,200 to the
Arab invasion of Egypt in A.D. 640, while Lake Mœris performed its
allotted task and the Nile possessed training works such as those we
can see to-day in Nubia, Egypt was better protected from inundation, and
the Nile better trained, than it is to-day. And yet we have many
advantages which no Pharaoh possessed. By the aid of telegraphy we have
knowledge of a coming flood a full fifteen days before it arrives in the
Delta; the Khartoum gauge allows us to anticipate its very height.
Meteorology is aiding us still further. In a paper I read at the Chicago
International Exhibition I stated that years of heavy rainfall in India
are years of high flood in Egypt, while years of poor rainfall in India
are years of low flood in Egypt. Sir John Eliot, the Director General of
the Meteorological Department of India, corrected this statement. He
said that though this was not true of the Bengal monsoon, it was true of
the Bombay monsoon. Years of heavy rainfall in Gujerat and Bombay are
years of high flood on the Nile, and vice versà. As the rain falls in
Bombay a month earlier than the Nile flood reaches Cairo, we have
information of a high flood a month before it arrives, if we receive
telegraphic information from Bombay.
36. =Complete project for water storage and flood protection for
Egypt.=--The complete project for water storage and flood protection for
Egypt as proposed by me, contemplates the following works:--
Raising the Assuân reservoir (2 years) £ 500,000
Wady Rayan reservoir (4 years) „ 2,600,000
Training the Rosetta branch „ 900,000
-----------
Total £ 4,000,000
===========
To these have to be added the approximate estimates of the proposed
works on the Upper Nile:--
Regulator for Lake Albert (4 years) £ 800,000
Dredging and training works in the Albert Nile and
the Zeraf river (12 years) £ 1,200,000
-----------
Total £ 2,000,000
===========
Grand total of works on the Upper and Lower Nile £ 6,000,000
===========
The total expenditure amounts to £6,000,000 spread over 12 years.
The great advantage of undertaking all those works together may be thus
summarized. The increased supply from the Assuân reservoir will be felt
in Egypt after a period of two years. Five years later the waters of the
Wady Rayan will be added to those of the Assuân reservoir, and it will
be possible to increase the cotton crop of Egypt from 6 million to 10
million cwt. It will be possible to allow the Sudan to thoroughly
develop its agricultural resources, and with the aid of the 25,000 horse
power as a minimum which the 6th cataract near Khartoum can supply, to
utilise for its own consumption the waters which can be stored at that
cataract; and, in addition to those, the available supplies from Lake
Tsana provided that that lake is furnished with an outlet tunnel.
While all this life and activity will be developing themselves in Egypt
and the Sudan, the effects of the regulator of Lake Albert and the
training of the Albert Nile in the Sudd regions will be gradually
asserting themselves; and, if the works are being steadily and
perseveringly carried out, it is well within the range of possibility
that before 10 or 12 years will have passed, the additional supplies
from the upper waters of the White Nile will have become so ample, that
it will be possible to dispense with the Wady Rayan as a reservoir. When
this will have happened, the Wady Rayan with its canal will become the
true flood escape of Egypt, like the ancient Lake Mœris, and will, with
the Rosetta branch, afford complete protection to Egypt against the
dangers of a high flood. Egypt, in the fullest meaning of the term, will
be enjoying perennial irrigation and flood protection.
In my book on the “Assuân Reservoir and Lake Mœris” I had recommended a
more extended programme, but the reading of Sir William Garstin’s Report
has convinced me that useful as the Lake Victoria reservoir dam may be,
its postponement as recommended by Sir William is sound, until all the
other works have been executed. The really essential work is the Lake
Albert reservoir dam, of which the study might indeed be commenced
immediately. Sir William’s proposal to train the summer supply of the
Albert Nile and allow the overflow of the floods to find its way through
the Sudd region is so sound and convincing that the necessary training
works in the Sudd region are greatly reduced. With these reductions the
estimated cost of the project for water storage and flood protection for
Egypt is reduced from £8,200,000 to £6,000,000. I have left the Wady
Rayan estimate as it was in my original programme. Mr. Webb’s criticism
of the project was based on facts which are outside the project. He
supposed that the Wady Rayan was to remain a reservoir for all time and
that it was not to be aided by the works on the Upper Nile. Now the
project I proposed and which I propose now, presupposes that the Wady
Rayan will be a temporary reservoir and final flood escape for the Nile,
and that it will be aided in years of very deficient flood by the
gradual improvement of the Upper Nile owing to the works undertaken
there.
37. =Sir William Garstin’s programme for water storage and flood
control.=--In the first appendix to his Report on the Upper Nile, Sir
William Garstin, G.C.M.G., Adviser to the Ministry of Public Works, has
drawn up a programme of works for water storage and flood control in the
Nile valley. He approves of the raising of the Assuân dam for £500,000,
and the conversion of the Rosetta branch of the Nile into a flood escape
for £900,000. He then conditionally approves of a proposal suggested by
Mr. J. S. Beresford, C.I.E., for making a straight cut from Bor on the
Albert Nile to the mouth of the Sobat river at the tail of the Albert
Nile. The line would be 340 kilometres in length and is estimated to
cost £5,500,000, and carry 600 cubic metres per second in summer. In
case of the line being found impracticable when it was surveyed and
levelled, Sir William proposed abandoning the Albert Nile and thoroughly
widening and deepening the Zeraf river for £3,400,000.
As a criticism of the Bor cut project I cannot write anything more
convincing from my point of view than a letter written by me and
published by “The Engineer” in October of this year.
“In your issue of the 16th September Sir Hanbury Brown has reviewed the
scheme suggested by Mr. J. S. Beresford, C.I.E., and conditionally
approved by Sir William Garstin, for diverting the waters of the Albert
Nile (known as the Bahr-el-Gebel) from Bor to the mouth of the Sobat
river, on a length 340 kilometres, and sending them down a canal capable
of carrying 600 cubic metres per second, at an estimated cost of
£5,500,000. In his review Sir Hanbury puts his finger on the weak point
in the project, viz., the difficulty and loss of water entailed at the
crossing of the Albert Nile just upstream of the Sobat mouth. The
difficulty will be got over, as Sir Hanbury himself suggests, by an
earthen embankment provided with a regulator. The loss of water cannot
be got over.
“I have taken the following figures from Sir William’s report and from
the gauge records of the Public Works Ministry:--
DISCHARGE IN CUBIC METRES PER SECOND DURING FEBRUARY, MARCH, AND APRIL
OF THE ALBERT NILE.
1901. 1902. 1903. 1904.
At Gondokoro above Bor 600 600 700 1,000
Upstream of the mouth of the Sobat river 300 300 350 435
“Now, in a year like 1901 or 1902, with 600 cubic metres per second
passing Gondokoro, the diversion canal might be allowed to take in 500
cubic metres per second, leaving 100 cubic metres per second for the
Albert Nile, Atem river, and all the Nuer, Dinka, and Shillook country
between Gondokoro and the Sobat mouth. An allowance of 100 cubic metres
per second would not be liberal, and would probably result in the water
becoming stagnant and very impure; but we shall leave that alone.
Starting with 500 cubic metres per second of clear water the high level
diversion canal would never lose less than 50 cubic metres per second
through percolation and evaporation before it reached the Sobat mouth.
Many authorities would put the loss at 40 per cent., but we shall say 10
per cent.
“We should then have 450 cubic metres per second entering the White Nile
at its head, just at the end of the Albert Nile and at the mouth of the
Sobat river. At this point, however, under normal conditions the Albert
Nile would have been discharging 300 cubic metres per second. This
supply, after the opening of the diversion canal, would have failed
utterly, as the waters of the Albert Nile would have been diverted down
the diversion canal. Whatever water there was in the Albert Nile would,
moreover, have been at so low a level that it could not have flowed down
the White Nile together with the high level water of the diversion
canal. We should therefore have had in a year like 1901 and 1902 a net
gain of 450 less 300 cubic metres per second, or 150 cubic metres per
second at the head of the White Nile. By the time this extra water
reached Assuân it would have become 100 cubic metres per second.
“If this project, or any other project of any kind, is ever to be
carried out on the upper waters of the White Nile, the very first thing
to be done will be to construct a weir or barrage at the outlet of the
Albert Lake, at Wadelai, or lower down at Dufile. I should say, judging
from the map and the cross section, that Wadelai itself would be an
excellent site for a weir. I have advocated this project in season and
out of season these ten years, and now that actual discharges and
figures are before me I am more than ever convinced that I was no untrue
prophet when I wrote in my book on “The Assuân Reservoir Dam and After”
that “the point where Lake Albert ends and the Albert Nile begins to
have a rapid and contracted stream will be the site of the future great
regulator or barrage of the upper waters of the Nile. This work will be
here or at Dufile.” Such a work would cost anything between £400,000 and
£1,000,000.
“If such a work were carried out it would be possible to insure every
year a discharge of between 1,000 and 1,500 cubic metres per second at
Gondokoro from the 15th of January to the 15th of May, _i.e._, during
the months which determine the summer water supply of the White Nile for
Egypt. Such a quantity of water would insure 435 cubic metres per second
at the head of the White Nile, as it has done this year, even under
existing conditions; while with training and dredger work in the Albert
Nile and Bahr Zeraf between Gondokoro and Lake No, it might be increased
to 600 cubic metres per second, and even more. The way in which this
work of training should be carried out has been admirably laid down on
page 174 of Sir William’s Report”.
There are moreover other reasons I think for condemning the excavation
of a straight cut 340 kilometres in length across the eastern corner of
the Sudd regions. The reasons are to be found in Sir William Garstin’s
Report itself. One of the most interesting features of this report is
the number of actually measured discharges at different sites. Of all
these sites Gondokoro, the southern key of the Sudd region, is the most
interesting.
It is very evident from an examination of Sections Nos. 18, 19, 26 and
27, Plate VIII of Sir William’s Report, that the Albert Nile at
Gondokoro scours out its bed very severely after a high flood like that
of 1903. The width of the section is about 230 metres with vertical
sides, and yet while a gauge of ·50 metres on the 1st April 1903 (after
the low year of 1902) gave a section of 615 square metres; on the 9th
September 1903 (after a good year), the section was 1,347 square metres
for a gauge of 2.33 metres. In other words, a rise of 1.83 metres gave
an increased section of 732 square metres; while, if the bed had not
scoured, it would have been 421 square metres. We have here an increase
of 311 square metres, or more than 1 metre of scour. All this happened
in 5 months, and proves that the clear water of the lakes, when in
volume, has a fine cutting edge.
In footnote (2) of page 116 of his Report, Sir William Garstin says that
in the parts of the river where the sudd has been cleared there are
indications that a scour of the bed has set in. Again, on page 55 of the
appendix, he says that the removal of the sudds has caused the levels of
the shallow lakes to fall. All this proves that if the spills and
escapes from the Albert Nile were closed with ambatch, as proposed by
Sir William Garstin on page 175, and a few dredgers put into the Albert
Nile and the Zeraf river the expenditure of a sum of money very moderate
indeed compared with £5,500,000 would in all probability result in the
two rivers being so widened and deepened that they could carry the full
summer supply of the lakes, and so there would be a resulting economy of
over £4,500,000 in the new channel from Bor which, when it began
working, might introduce on an aggravated scale all the difficulties of
to-day in the Albert Nile.
A good description of certain spills is given on page 112 of the Report,
a good idea of scour in Plate XXIX., opposite page 110, while on page
181 Sir William Garstin makes the remark that the experience of American
engineers has taught us that though in theory it may be possible to
shorten or straighten a great river, in actual practice it is
accompanied with almost insurmountable difficulties. If the new channel
were dug and set working, in a few years it might be as crooked as the
Albert Nile itself, unless it were protected with stone along its entire
length.
In my project for deepening and widening both the Albert Nile and the
Zeraf river to enable them to carry 600 cubic metres per second, I think
I have given very solid reasons against abandoning the Albert Nile and
sending the whole supply down the Zeraf river at a cost of £3,400,000.
I cannot but think that Sir William Garstin’s recent objections to the
Albert Nile are founded on an oversight. He has, apparently, not kept
the flood discharges of the Albert Nile at Gondokoro and above the Sobat
mouth sufficiently apart from those of low supply. It is the Sobat
flood, combined with the poor carrying capacity of the White Nile, which
is the disturbing factor, and not any inherent viciousness in the
Albert Nile itself. The Albert Nile has a good section, and, if it were
trained in conjunction with the Zeraf river, would, I feel confident,
discharge all the water required with a very moderate expenditure of
money. This, I always understood, was Sir William’s own opinion. In such
projects it is wise to remember Horace’s saying, “Naturam furcâ expellas
tamenusque recurrit.”
38. =Project for converting the basin irrigated lands of Upper Egypt
into perennially irrigated lands.=--No consideration of this question
would be complete without first examining into the changes which would
be made in the regimen of the Nile flood by the contemplated conversion
of basin irrigation into perennial irrigation. This question was
examined very thoroughly by me in 1892 and 1893 and I give here my
arguments for not anticipating any serious difficulties.
We have to consider the effect of the introduction of perennial
irrigation on the regime of the Nile. The perfection of the perennial
irrigation of the Delta north of Cairo will in no way affect the Nile in
flood. The canals will continue to run as they do at present, and the
question of conversion in Lower Egypt is therefore quite independent of
the subject of flood protection. In Upper Egypt, however, we have
1,460,000 acres of basin irrigation; and as each acre receives in a low
flood 80 cubic metres of water per day, in an ordinary flood 130 cubic
metres per day, and in an extraordinary flood 170 cubic metres per day,
while the demands of perennial irrigation are only 25 cubic metres per
acre per day, it will readily be understood that we are dealing with a
quantity of water which demands the greatest attention.
To foretell with exactitude the anticipated changes in the regime of the
Nile, it is necessary to know first the daily gauges of the Nile at
Assuân and Cairo for a period of at least twenty years, and the
discharges corresponding to these gauges. The difference between these
discharges represents the consumption of water. We have next to
determine the amount of water which passes into the canals, the amount
utilised in filling up the trough of the Nile and covering the berms,
and the amounts evaporated and absorbed. We know that the last three
items are constant while the canal discharges are variable and depend on
the system of irrigation and, if our data are correct, we can tell with
moderate certainty what changes in the level of the Nile will follow
certain changes in the system of irrigation.
Tables 65 and 67 of Appendix L contain the Assuân and Cairo gauges for
typical years in a period of twenty years from 1873 to 1892, and the
mean gauges of these twenty years. Finding it impossible to understand
the Nile without first referring every gauge to some uniform standard, I
have had to choose the line of reference. The mean high water level and
the mean low water level are both available. In Egypt the mean high
water level varies very considerably whether we take it in August and
the early part of September when the basin canals are running full
supply, or in the latter half of September when the canals are running
only half supply, or in October when the basins are discharging back
into the Nile. Early and quick rising floods have a different series of
levels from slow and late floods; while again the recent works carried
out in Upper Egypt by Col. Ross have so increased the discharging
capacity of the canals that the flood gauges have been appreciably
affected. All this points to the conclusion that the mean high flood is
no satisfactory standard. The mean low flood on the other hand is much
less liable to change and is very fairly constant from year to year.
High floods are certainly followed by scouring out of the bed, and low
floods by a silting up of the channel, but the changes are very moderate
compared to those in high flood. I have chosen the mean low water level
as the line of reference, and referred all gauges to it. From the mean
of twenty years’ observations, this level at Assuân is R. L. 85 metres.
By observations along the Nile generally, and by calculations at Cairo,
I have fixed it at all important places north of Assuân. Table 46 of
Appendix K gives the Reduced Levels at different places, while it is
also drawn on the longitudinal section of the Nile in Plate XII. It was
on this system that the ancient Egyptian engineers worked the Nile. They
however chose the mean high water level during the early part of the
flood as their standard of reference and consequently made the so called
cubits in the flood reaches of the Cairo gauge half cubits. This means a
discharge of 1600 cubic metres per second and fairly represents the
discharges of the basin canals in flood. When it is considered that the
level of the Nile valley is raised by about 10 centimetres per 100 years
it will be seen that the old Cairo gauge, which was a living record 1500
years ago, is to-day a meaningless anachronism. It has also to be
compared with the Assuân gauge which was erected in Ismail Pasha’s time
with an arbitrary zero some 90 centimetres below mean low water level,
and which may be reading 17 cubits while Cairo may be recording 25
cubits. The Cairo gauges in winter and summer are no records of
discharge as the afflux from the Barrage affects them. To find the
discharge at Cairo during these months, I have added those of the
Rosetta and Damietta branches and the Delta canals upstream of the
Barrage. When the Nile falls below mean low water level, the gauges are
recorded as minus quantities.
Discharge sites having been chosen for the Assuân, Assiout and Cairo
gauges on the Nile, a continuous series of surface velocity
observations, cross sections and slope measurements were made during
1892 and 1893 and the resulting discharges recorded. Curves of discharge
have been drawn and referred to the gauges of twenty years and modified
until finally a curve has been found which will suit any year whether it
is a maximum or a minimum. In connection with this subject, it must be
remembered that the Nile bed is raised by silt during low floods and
scoured out during high floods and that consequently August and
September discharges vary considerably at times from October and
November discharges for the same gauge. In addition to this, it must
also be borne in mind that the slope of water surface and that
consequently the discharge of a flood during the rise is far greater
than during the fall for the same gauge reading. Indeed the Nile often
discharges more when it is 30 centimetres below its maximum and rising
fast than when it has reached its maximum and begun to fall. It is owing
to this fact that we often see the discrepancy of the Assuân gauge
reaching its maximum a day before Halfa which is 350 kilometres higher
up the river. The discharge depends on gauge and slope, and the gauge
only records one element. Keeping these facts in my mind, I saw that it
was of no use recording the gauges to two places of decimals and
covering paper with useless figures, and consequently I have chosen the
higher unit for a rising gauge and the lower for a falling gauge when I
have been dealing with discharges.
Flood discharges have been taken of all the canals in Upper Egypt
through 1892 and 1893 and have been recorded in Tables 48 and 49 of
Appendix K. From these tables, Table 47 has been compiled which gives
rough approximate discharges of the canals corresponding to the Assuân
gauges in the first half of the flood.
To obtain information about the trough of the Nile, the area exposed to
evaporation and the area of absorption, a longitudinal section of the
Nile from Assuân to Cairo has been levelled, and cross sections taken at
every 3 kilometres. The kilometrage on Plate XII counts from the Assuân
gauge and is measured down the centre of discharge of the flood, since
it is with flood discharges that we are principally dealing. As the Nile
winds about considerably and is often broken into numerous channels, the
areas of the cross sections vary very appreciably according as they are
taken at right angles to the centre line of discharge or of the deep
channel of the river. The former gives the more reliable results. I have
taken 8 millimetres per day as the evaporation during flood in Upper
Egypt. The absorption has been calculated from the water consumption
during the floods of 1892 and 1893, and found to be about 300 cubic
metres per second between Assuân and Assiout, where there is practically
no perennial irrigation. Between Assiout and Cairo, where there is a
considerable length of perennial irrigation on one bank and limestone
rock on the other, the absorption is about 100 cubic metres per second.
When perennial irrigation has once established itself in Upper Egypt, we
may assume that the absorption during flood will be halved in quantity
for the reasons given above, and become 150 cubic metres per second
between Assuân and Assiout, and 50 cubic metres per second between
Assiout and Cairo. The amount of water expended in irrigation will be
about 700 cubic metres per second. The evaporation during flood will be
approximately 120 cubic metres per second. The quantity of water needed
to fill the trough of the Nile will depend on the gauges and may be
calculated from table 43 of Appendix K. The last item will be the only
variable one and the others may be approximately tabulated as follows:--
_Expenditure of water in flood in cubic metres per second_:
BETWEEN ASSUÂN BETWEEN ASSIOUT TOTAL
AND ASSIOUT. AND CAIRO.
Perennial irrigation 350 350 700
Evaporation 65 55 120
Absorption 150 50 200
--- --- ----
Total of above 565 455 1020
=== === ====
Taking these quantities and calculating directly for the filling of the
trough from the gauges themselves, I have collected in Tables 50 to 52,
the Cairo gauges corresponding to the Assuân gauges for the high years
1874 and 1878 and the minimum year 1877. As far as the more important
results are concerned, I tabulate them here:--
=Gauges at Assuân and Cairo.=
============+=======================+=======================+
Date. | 1874 | 1878 |
+-------+-------+-------+-------+-------+-------+
|Assuan.| Cairo | Cairo |Assuan.| Cairo | Cairo |
| | with | with | | with | with |
| | basin | peren-| | basin | peren-|
| | irri- | nial | | irri- | nial |
| |gation.| irri- | |gation.| irri- |
| | |gation.| | |gation.|
------------+-------+-------+-------+-------+-------+-------+
August 5| 6·9 | .. | .. | 5·6 | .. | .. |
10| 7·4 | 6·5 | 5·8 | 5·3 | 4·9 | 4·4 |
15| 8·5 | 6·9 | 6·4 | 7·2 | 5·4 | 5·2 |
20| 8·6 | 7·3 | 7·8 | 7·5 | 6·0 | 6·3 |
25| 8·7 | 7·5 | 7·9 | 8·1 | 6·3 | 6·5 |
31| 8·7 | 7·6 | 8·1 | 7·6 | 6·6 | 7·2 |
------------+-------+-------+-------+-------+-------+-------+
September 5| 9·0 | 7·7 | 8·2 | 8·1 | 6·5 | 7·5 |
10| 8·8 | 8·0 | 8·3 | 8·5 | 6·8 | 7·5 |
15| 8·7 | 8·2 | 8·4 | 8·9 | 7·2 | 8·0 |
20| 8·4 | 8·3 | 8·5 | 8·9 | 7·6 | 8·5 |
25| 8·4 | 8·4 | 8·2 | 9·0 | 7·9 | 8·5 |
30| 8·2 | 8·4 | 8·2 | 9·1 | 8·2 | 8·5 |
------------+-------+-------+-------+-------+-------+-------+
October 5| 7·9 | 8·7 | 7·9 | 8·9 | 8·4 | 8·6 |
10| 7·6 | 8·5 | 7·6 | 8·5 | 8·7 | 8·6 |
15| 7·2 | 8·3 | 7·4 | 7·9 | 8·4 | 8·4 |
20| 6·6 | 8·0 | 7·0 | 7·6 | 8·1 | 8·0 |
25| 6·2 | 7·7 | 6·3 | 7·4 | 7·9 | 7·4 |
31| 5·6 | 7·0 | 5·9 | 6·8 | 7·7 | 7·2 |
============+=======+=======+=======+=======+=======+=======+
============+=======================+=======================
Date. | 1892 | 1877
+-------+-------+-------+-------+-------+-------
|Assuan.| Cairo | Cairo |Assuan.| Cairo | Cairo
| | with | with | | with | with
| | basin | peren-| | basin | peren-
| | irri- | nial | | irri- | nial
| |gation.| irri- | |gation.| irri-
| | |gation.| | |gation.
------------+-------+-------+-------+-------+-------+-------
August 5| 6·3 | .. | .. | 4·9 | .. | ..
10| 6·8 | 5·3 | 5·1 | 5·4 | 4·0 | 3·9
15| 6·7 | 5·8 | 5·8 | 5·8 | 4·7 | 4·6
20| 7·4 | 5·4 | 6·2 | 6·4 | 4·6 | 5·0
25| 8·3 | 5·8 | 6·5 | 6·1 | 5·3 | 5·5
31| 8·3 | 6·6 | 7·7 | 6·2 | 5·3 | 5·6
------------+-------+-------+-------+-------+-------+-------
September 5| 8·6 | 6·9 | 7·7 | 6·3 | 5·2 | 5·2
10| 8·8 | 7·1 | 8·0 | 6·1 | 5·3 | 5·3
15| 8·8 | 7·5 | 8·3 | 6·0 | 5·2 | 5·5
20| 8·9 | 7·9 | 8·3 | 6·0 | 5·2 | 5·4
25| 8·6 | 8·1 | 8·4 | 6·3 | 5·1 | 5·4
30| 8·4 | 8·3 | 8·4 | 6·1 | 5·3 | 5·6
------------+-------+-------+-------+-------+-------+-------
October 5| 8·2 | 8·4 | 8·3 | 5·6 | 5·2 | 5·4
10| 7·8 | 8·3 | 8·1 | 5·2 | 5·0 | 5·0
15| 7·4 | 8·1 | 7·7 | 4·9 | 4·9 | 4·6
20| 7·2 | 7·9 | 7·2 | 4·6 | 4·6 | 4·4
25| 6·8 | 7·9 | 7·0 | 4·5 | 4·4 | 4·0
31| 6·3 | 7·8 | 6·6 | 4·0 | 4·2 | 3·9
============+=======+=======+=======+=======+=======+=======
To enable one to compare these figures which are in metres and referred
to mean low water level, with the gauges as recorded at present, I add
the following table:--
=========================++=========================
ASSUAN || CAIRO
----------+--------------++----------+--------------
Real | Gauge || Real | Gauge
gauge | as recorded || gauge | as recorded
in metres.| in cubits ||in metres.| in cubits
| and 24ths. || | and 24ths.
----------+--------------++----------+--------------
| || |
|Cubits. 24ths.|| |Cubits. 24ths.
0.0 | 1 13 || 0.0 | 6 9
.5 | 2 12 || .5 | 7 7
1.0 | 3 10 || 1.0 | 8 5
.5 | 4 8 || .5 | 9 4
2.0 | 5 6 || 2.0 | 10 2
.5 | 6 4 || .5 | 11 0
3.0 | 7 3 || 3.0 | 12 0
.5 | 8 1 || .5 | 13 0
4.0 | 8 23 || 4.0 | 13 23
.5 | 9 21 || .5 | 14 21
5.0 | 10 20 || 5.0 | 15 19
.5 | 11 18 || .5 | 17 12
6.0 | 12 16 || 6.0 | 19 8
.5 | 13 14 || .5 | 21 4
7.0 | 14 12 || 7.0 | 22 12
.5 | 15 11 || .5 | 23 10
8.0 | 16 9 || 8.0 | 24 9
.5 | 17 7 || .5 | 5 7
9.0 | 18 5 || 9.0 | 26 5
----------+--------------++----------+-----------
16 cubits at Assuân corresponds to 7.8 metres.
17 „ „ „ „ „ 8.3 „
18 „ „ „ „ „ 8.9 „
A cubit is known in Egypt as a pic.
-------------------------------------------------
16 cubits at Cairo corresponds to 5.1 metres.
22 „ „ „ „ „ 6.7 „
23 „ „ „ „ „ 7.3 „
24 „ „ „ „ „ 7.8 „
25 „ „ „ „ „ 8.3 „
25¹⁄₂ „ „ „ „ „ 8.6 „
=================================================
The flood of 1874 was an early one and the basins were discharged on a
falling Nile, still they raised the Cairo gauge to 8·7 metres on the 5th
October while it would have risen to 8·5 on the 15th September with
perennial irrigation. The flood of 1878 was an exceedingly late one and
the basins had to be discharged while the river was still very high. By
the 10th October, the river had risen to 8·7 metres at Cairo when the
banks were breached and all future rise stopped. With perennial
irrigation, the maximum gauge of 8·6 metres would have been reached on
the 10th October. The flood of 1892 was at Assuân 10 centimetres below
that of 1874 and 20 centimetres below that of 1878, and midway between
them in point of time. It was also under complete control owing to the
new regulating works on the basins. It rose to 8·4 metres at Cairo on
the 5th October and fell exceedingly slowly. With perennial irrigation,
it would have risen to 8·4 at Cairo on the 30th September and then
fallen rapidly.
Speaking generally, we may say that with perennial irrigation the very
high floods at Cairo will be 15 days in advance of what they are at
present, that they will not rise higher, and that they will fall 15 days
earlier than what they do now. With low floods there will be no
appreciable difference as to date, but the floods will be slightly
higher at Cairo. In ordinary floods, there will be an advance of from 20
to 25 days in the date of the maximum flood, and a maximum gauge at
Cairo 50 or 60 centimetres under the maximum gauge at Assuân. We have so
far considered Cairo only, as the Delta proper depends on the Cairo
gauge. We now turn to the Nile in Upper Egypt itself: south of Sohag,
there will be no serious change in levels, but the Sohagia and Ibrahimia
canals between them carry at present 750 cubic metres per second in
excess of what they would carry if there were perennial irrigation in
Egypt, and the greater part of this water is not returned to the Nile
until the Kushesha escape is reached. The reach of the Nile from Sohag
to Kushesha is the one which will experience the greatest changes, and I
calculate that there will be a rise of 40 centimetres as compared with
the maximum gauges under basin irrigation.
It will be noted that at the beginning of this paragraph I stated that
“the perfection of the perennial irrigation of the Delta north of Cairo
will in no way affect the Nile in flood.” This had reference only to the
quantity of water taken from the Nile in high floods. There is however
one very serious aspect of this question. The regulation on the Barrage
in low floods, which has gone on steadily since 1899 when Sir Hanbury
Brown used the Barrages in flood for the first time, has enormously
increased the value of the works, but it has certainly caused the Main
Nile to silt, and probably also the branches, owing to a reduced
discharge and velocity of the silt-bearing water, whose capacity to
carry on that quantity of silt depends on its velocity. It seems to me
that unless steps are taken to insure the scouring out of this silt by
the clear water of November, December and January the consequences will
be very serious. High floods scour out their beds, but if a very high
flood were to come early before the silt had been scoured out, it might
overflow the banks near Cairo or in the middle reaches of the Nile
branches in the Delta.
Sir William Garstin has estimated the cost of converting the existing
basins of Upper Egypt into perennially irrigated land at £7,000,000,
thus made up:--
Conversion of Upper Egypt basins £ 5,000,000
Two barrages between Assyut and Kena „ 2,000,000
-----------
Total £ 7,000,000
===========
The resulting land tax from the improved irrigation in Upper or Lower
Egypt he has estimated as follows:--
Upper Egypt. {Basin land converted 750,000 acres @ £ ·50 = £ 375,000
{Land irrigated by pumps 100,000 „ @ £ ·30 = „ 30,000
Lower Egypt. Reclaimed land 800,000 „ @ £1.00 = „ 800,000
---------
Total £ 1,205,000
=========
39. =Development of the Sudan.=--Lord Cromer’s wise decision to
construct the Suakin-Khartoum railway immediately and the Abu
Hamed-Dongola railway as soon as possible, is the charter of the
development of the Sudan. With these railways and especially the former
in working order, we can arrange for irrigation works for the production
of cotton and wheat for export, knowing that they can be exported at a
cost of transport which will not be absolutely prohibitive. The soil of
the Sudan along the Blue Nile, the Atbara, the Main Nile and a great
part of the White Nile is the same as that of Egypt itself. It has all
come from Abyssinia. When at Khartoum last February, I collected
specimens of typical Gezireh soil from points 10 miles south of Khartoum
and from near Khartoum itself. They were analysed by Mr. Frank Hughes
and reported on by Mr. Foaden.
The specimens were numbered as follows:--
(1) Typical Gezireh soil from a point 10 miles south of Khartoum near
the Blue Nile.
(2) Typical Gezireh soil from a point 2 miles south of Khartoum near the
White Nile.
(3) White Nile side under cultivation in 1904.
(4) White Nile side below flood level.
(5) Blue Nile side, not so common as (1).
(6) The sandy soil generally within 5 miles of Khartoum.
Nos. 1, 2, 5, and 6 are above high flood level of both Niles.
“The nitrogen and salt were determined in the samples, as received,
without drying.
Nos. 1 2 3 4 5 6
Nitrogen 0·078 0·059 0·062 0·057 0·056 0·052
Common salt 0·050 0·020 0·010 0·090 0·170 0·020
“All contain abundance of carbonate of lime; Nos. 1 and 2 might almost
be called calcareous. All gave a strong reaction for phosphoric acid,
and there is therefore every reason to believe that they are rich in
this ingredient. So far as the texture of the soils is concerned, little
can be said except that they differ from those previously examined for
Kena Mudirieh, in containing a large amount of coarse sand 1-3 m.m.,
which is entirely absent in most Egyptian soils; No. 6 would probably be
too light for agricultural purposes in its present condition.
“The nitrogen is as high as one would expect but is lower than is
necessary for fertile soils. It would be necessary therefore to
encourage the growth of leguminous crops to increase the quantity of
nitrogen in the soil and to employ nitrogenous manures. It must be borne
in mind that in soils of this class the nitrogen is usually in a highly
insoluble and un-nitrifiable form.
“The salt is in no case high; 0.25% is usually considered to be the
limit for satisfactory growth; all the samples are well below this
limit.”
I had complete analyses made of numbers (1) and (2). The results were as
follows:
No. 1 No. 2
Silica etc. insol in mineral acid 74.76 73.85
Lime (Ca.O.) 6.07 4.56
Carbonic Acid (C.O.₂) 3.64 2.40
Equal to Chalk (Ca.C.O.³) 8.27 5.46
Potash 0.23 0.34
Phosphoric Acid 0.14 0.12
Organic Matter 2.88 4.07
Nitrogen 0.075 0.062
Calculated on soil dried at 100°.
Though none of these specimens contained salt in excess, Nile deposit in
certain localities has very large proportions of common salt and
sulphate of soda. The dark soil near the Atbara mouth at El-Damer is
largely exploited for common salt, while similar soil south of Khartoum
is free from it.
The extent of this Nile deposit soil is very great indeed and if
irrigation could be assured, there would be a great future before the
Sudan.
In Mr. Dupuis’s Report which is the last appendix to Sir William
Garstin’s Report, he speaks of this soil as being met with on the Blue
Nile, on the Rahad, on the Atbara and on the Gaash. From Khartoum
northwards the main Nile flows between berms of this soil.
The extent and quality of this soil may therefore be considered as an
undisputed asset of the Sudan. We have next to consider the seasons.
A reference to tables 76, 77, and 80 will show how much warmer the Sudan
is than Egypt, and any attempt to introduce Egyptian methods into the
Sudan without modifications will not at once turn the Sudan into Egypt.
I allow that extensive plains of irrigated land greatly moderate the
heat as they have already done in Middle Egypt; but we have to begin
from the beginning in the Sudan, and there are no extensive plains of
irrigated land. Basin irrigation will be a failure in the Sudan unless
it is supplemented by two or three waterings in the winter, for all
crops except the cheapest and coarsest leguminous crops. Wheat must be
irrigated in winter whether sown in a basin or on the Nile berm, except
in a few choice, low and damp localities. Cotton, on the other hand,
which has to be sown in spring in Egypt and reaped in autumn will need
such an extraordinary quantity of water to pull it through the summer
that it will be found preferable to grow it in June with the rising
flood and reap it at the end of the winter. Irrigation therefore from
June to October for Indian corn, from June to February for cotton, and
from November to February for wheat will be essentials of a good harvest
in the Sudan.
We now come to the question of the water supply. Unless permits are
given for pumps to work from the 15th June to the 15 February, the
cultivation of cotton and wheat on any scale in the northern part of the
Gezireh, along the main Nile between Khartoum and Dongola, and on the
lower reaches of the Atbara will be out of the question. Maize and
millets and some of the coarser leguminous plants might be developed by
pumps with permits to work from 15th June to 15th October, but it would
pay no one to put up pumps on these terms.
Fortunately for the joint interests of Egypt and the Sudan, though Egypt
cannot spare water between the 15th March and 30th June, which would
correspond to 1st March and 15th June in the Sudan; she has enough to
spare for pumps at other times, though she has not always enough to
spare for large free flow schemes in the Sudan. Free flow schemes in the
Sudan, except during high and good floods, have however yet to be found.
Speaking generally we may say that the agricultural success of the Sudan
will depend on permits for pumping engines to work between the 1st June
and the end of February. There should be no difficulty in the way of
such permits being given. We have spoken so far of schemes within the
power of individuals and companies. Of schemes which the Government
alone could carry out by itself or in conjunction with powerful
companies, the most promising seem to be those which are connected with
the 6th cataract. This cataract seems well suited for the construction
of a solid dam to create power and develop electricity to work pumps
between it and Khartoum, and some 30 kilometres up the Blue Nile; and if
possible to allow of a canal down the left bank of the Nile as far as
Berber. This project might be studied with advantage and a greater
amount of water storage for summer use be also obtained.
[Illustration: PLATE XX
SKETCH PLAN OF
COUNTRY ABOUT DELGI
N.W. OF L. TSANA
_Scale 1 : 50.000_
Lith. Sur. Dep. Cairo.]
Another scheme is the construction of a double barrage and weir near Wad
Medani on the Blue Nile, with canals irrigating the Gezireh and the
right bank of the Blue Nile and the Nile to Shabluka. Unfortunately no
cross sections have been taken of the Blue Nile showing how high the
Gezireh is above the bed and water surface of the Blue Nile at Wad
Medani. A weir further south would, as Mr. Dupuis states, entail very
expensive canals to irrigate the lands south of Khartoum.
Mr. Dupuis’s report on the Atbara is not very hopeful. Without
reservoirs this torrential river could insure no crop except millets and
Indian corn. The same may be said for the Gaash. Basins without winter
irrigation would, I think, be most unsatisfactory.
Examining Mr. Dupuis’s figures and sections for the outlet of lake
Tsana, I calculate that this reservoir would not supply a fraction of
the water estimated by Mr. Dupuis. If I were wrong, and I should be
pleased indeed to be wrong here, a tunnel along the alignment roughly
surveyed by Mr. Dupuis, Plate XX, leading the waters of Lake Tsana into
the Rahad river, and from there under the Blue Nile by a syphon, and
branch canals irrigating both banks of the Rahad and both banks of the
Blue Nile to Khartoum, would be one of the boldest projects in the
world.
It will be noted that no mention has been made of the tracts between the
foothills of Abyssinia and Wad-el-Medani which can produce good crops of
Indian corn, millets and even cotton in nine years out of ten with the
aid of rain without irrigation. If the land could lend itself to basins
similar to those of Bundelkund or to river fed pans as in Madras, a
development of this country would be possible. Ordinary Egyptian basin
irrigation would be, I think, of no use.
The following quotations from a letter written by Messrs. Choremi,
Benachi and Co., of Alexandria, to Mr. Foaden on the 8th February 1904,
will give an idea of the estimation in which Sudan grown cotton is held
in Alexandria:--
“The cotton generally is good and superior to any Sudan cotton I have
yet seen. Last year the best I saw was sent by the Sudan Government and
grown in Miralai Stanton Bey’s garden, with artificial irrigation and
quality was (first picking) class “good”, equal to Beni-Suef or Minieh
cotton, but more woolly. In any case it is saleable cotton for coarse
Nos. of Yarn, not what we call Bolton Spinners’ cotton.
“I now give you the following classification and values compared to
Standard of Full Good Fair Lower Egypt which is the basis of “Futures”
in our Market and Liverpool.
“On Upper Egypt the outturn in ginning on basis 315 lbs. per cwt. in
seed runs from 100 to 104, and Lower Egypt 105-110 according to province
grown and quality of seed.
No. 1 Outturn 96 Class “good”, value P.T. 5 over Delta fully good
fair--colour rather light--good staple, better
than Beni-Suef Ashmouni or even Afifi.
No. 2 „ 98¹⁄₂ Long staple and finish does not look grown from
afifi seed but from superior quality, value about
P.T. 15 over F.G.F.
No. 3 „ 99 Class “good”, the seed of this is from
Delta because mixed--there is also some
Abassi in and does not look as from afifi
seed because finer than any afifi grown in
Minieh and Beni-Suef, value 5 to 10 over
F.G.F.
No. 4 „ 102¹⁄₂ “Good” in class, from mixed seed--some looks
afifi, other better, probably Yannovich
seed. There are traces of abassi--and is
irregular in strength, value P.T. 15 to 20 over
F.G.F.
No. 5 „ 100 Also from mixed seed--I can trace afifi quality
and Yannovich, also some abassi. Value over
F.G.F. about 7 to 10 P.T.
No. 6 „ 103¹⁄₂ About same as No. 5 and with same mixture.
“From the above report you will see that quality generally is good--but
I regret the seed got mixed--probably through mistakes in transport or
if in single bags some broke and seed became mixed.
“The outturn in ginning I consider good and the seed I notice
deteriorates but very little as you can see--though with that of Stanton
Bey’s I examined with you last year, the deterioration was, if I
remember right, something like 10% in one year. The seed from the non
irrigated Sudan (I suppose near Khartoum) though from good Afifi seed,
almost becomes unfit for sowing and the quality of this cotton had a
very poor outturn of about 73%.
“Rain crops cannot be depended on, because if no rain for some time the
quality will be totally spoilt.
“I fail to find any trace of sand in the samples--though the common
Sudan non-irrigated cotton was very dirty and sandy.”
The following extracts from a letter written to me by Ibrahim Effendi
Fahmy, originally a student of the Cairo Agricultural College and at the
time of writing Government agriculturist at Khartoum and on leave in
Cairo, will be found interesting.
“There are three seasons in the Sudan, which are different from those in
Egypt. The seasons are:--1st the winter which extends from the 1st
November to the end of February, in this season wheat, beans, barley,
onions, Indian corn and millets are planted: 2nd, the summer which
extends from 1st March to the 15th June, in this season, practically
speaking, nothing is planted except a small quantity of millets, and in
the middle of the season from the 1st May to the 15th June all
agricultural work is stopped owing to the great heat and deficiency of
water: and 3rd, the flood season or “Demera” from the 15 June to the end
of October; in this season the rains fall, the Nile rises and the heat
is decreased, two crops of millets can be taken and cotton, sesame and
earthnuts are sown.
“Manures are the same as in Egypt.
“Cotton sown in March, April and May needs so much water through the
summer that its cost is prohibitive. In the really hot weather it must
be irrigated every three days. High winds and rain hurt the first open
pods, and the pickings are on the 20th August, 20th September and 15th
October. After 22 waterings a good field will give 4¹⁄₂ cwt. per acre.
“Cotton sown in June and July has an even, regular growth. The rains and
moisture in the air encourage the growth of the plant. The height of
the flood permits of easy irrigation even when it is lift. The plants
grow to a great size but have many bolls. The following table will show
the growth of the plants.
=================+===============+==============+=============
Date of planting.|No of waterings|First picking.|Last picking.
-----------------+---------------+--------------+-------------
25 June | 16 | 1st January | March 15
3 July | 16 | 15th January | March 31
30 July | 15 | 15th February| April 15
=================+===============+==============+=============
“The yield of a good field is 5¹⁄₂ cwt. per acre. The fibre is better
than that of the cotton sown in March and April.
“I consider that June and July are the best months for sowing, and that
cotton sown from well-selected seed and well cultivated will prove
itself a cotton of superior quality, ranking with Egyptian cottons.
“The following table gives the kinds of crops, other than cotton which
can be profitably grown in the Sudan:--
=================+===========+==========+=========+=================
Crop | Time of | Time of | N^{o} of| Produce
| sowing. |ripening. |waterings|
-----------------+-----------+----------+---------+-----------------
Egyptian wheat |Nov. & Dec.| April | 3 | 5¹⁄₂ ardebs
Indian wheat | December | » | 3 | 5 »
Egyptian barley | » | March 31 | 2 | 11 »
Australian barley| » | » | 2 | 5 »
Beans | » | » | 3 | 5 »
Lentils | » | » | 3 | 3¹⁄₂ »
Earthnuts | July | January | 9 | 9 »
Indian corn | » |September | 4 | 6 »
American maize | » | October | 7 | 4 »
Potatoes | November | March | 3 | 150 kantars
Lucerne | March |March year| 12 | 1800 »
| | | |in 12 cuttings of
| | | |150 kantars each.
=================+===========+==========+=========+=================
“Fodder crops such as birseem and vetches (gilban) when well watered are
satisfactory.
“If the land is not well tilled, manured and looked after, wheat will
require 6 waterings and barley 4 waterings.
“If water can be obtained in the Sudan, the agricultural problem is very
easy.”
I cannot do better than close this chapter with this thoroughly Egyptian
remark of Ibrahim Effendi Fehmy.