necessity of laying under-water foundations. The length of the
dam is about 6400 ft.—nearly 114 m. The greatest head of water
The
Assuan
Dam.
in it is 65 ft. It is pierced by 140 under-sluices of
150 sq. ft. each, and by 40 upper-sluices, each of 75 sq.
ft. These, when fully open, are capable of discharging
the ordinary maximum Nile flood of 350,000 cub. ft.
per second, with a velocity of 15.6 ft. per second and a head
of 6.6 ft. The top width of the dam is 23 ft., the bottom width
at the deepest part about 82 ft. On the left flank of the dam
there is a canal, provided with four locks, each 262 by 31 ft.
in area, so that navigation is possible at all seasons. The
storage capacity of the reservoir is about 3,750,000 millions
of cub. ft., which creates a lake extending up the Nile Valley
for about 200 m. The reservoir is filled yearly by March; after
that the volume reaching the reservoir from the south is passed
on through the sluices. In May, or earlier when the river is
late in rising, when the demand for water increases, first the upper
and then the under sluices are gradually opened, so as to increase
the river supply, until July, when all the gates are open, to allow
of the free passage of the flood. On the 10th of December
1902 this magnificent work was completed. The engineer
who designed it was Sir W. Willcocks. The contractors were
Messrs John Aird & Co., the contract price being £2,000,000.
The financial treaties in which the Egyptian government were
bound up prevented their ever paying so large a sum as this
within five years; but a company was formed in London to
advance periodically the sum due to the contractors, on receipt
from the government of Egypt of promissory notes to pay sixty
half-yearly instalments of £78,613, beginning on the 1st of July
1903. Protective works downstream of the dam were completed
in 1906 at a cost of about £E304,000. It had been at
first intended to raise the dam to a height which would have
involved the submergence, for some months of every year,
of the Philae temples, situated on an island just upstream
of the dam. Had the natives of Egypt been asked to choose
between the preservation of Ptolemy’s famed temple and the
benefit to be derived from a considerable additional depth of
water storage, there can be no question that they would have
preferred the latter; but they were not consulted, and the
classical sentiment and artistic beauty of the place, skilfully
pleaded by archaeologists and artists, prevailed. In 1907,
however, it was decided to carry out the plan as originally
proposed and raise the dam 26 ft. higher. This would increase
the storage capacity 212 times, or to about 9,375,000 millions
of cubic feet.
There is no middle course of farming in Egypt between irrigation and desert. No assessment can be levied on lands which have not been watered, and the law of Egypt requires that in order to render land liable to taxation the water during the Nile flood must have flowed naturally over it. It is not enough that it should be pumped on to the land at the expense of the landowner. The tax usually levied is from £1 to £2 per acre.
See Sir W. Willcocks, Egyptian Irrigation (2nd ed., 1899); Sir C. C. Scott-Moncrieff, Lectures on Irrigation in Egypt. Professional Papers on the Corps of Royal Engineers, vol. xix. (London, 1893); Sir W. Garstin, Report upon the Basin of the Upper Nile. Egypt No. 2 (1904).
V. India.—Allusion has already been made to the irrigation
of India. The year 1878, which saw the end of a most disastrous
famine, may be considered as the commencement of a new era
as regards irrigation. It had at last been recognized that such
famines must be expected to occur at no very long intervals
of time, and that the cost of relief operations must not be met
by increasing the permanent debt on the country, but by the
creation of a famine relief and a famine insurance fund. For
this purpose it was fixed that there should be an annual provision
of Rx. 1,500,000, to be spent on: (1) relief, (2) protective works,
(3) reduction of debt. Among protective works the first place
was given to works of irrigation. These works were divided
into three classes: (i.) productive works; (ii.) protective
works; (iii.) minor works.
Productive works, as their name implies, are such as may
reasonably be expected to be remunerative, and they include
all the larger irrigation systems. Their capital cost is provided
from loan funds, and not from the relief funds mentioned above.
In the seventeen years ending 1896–1897 the capital expenditure
on such works was Rx. 10,954,948, including a sum of Rx. 1,742,246
paid to the Madras Irrigation Company as the price of the
Kurnool-Cuddapah canal, a work which can never be financially
productive, but which nevertheless did good service in the
famine of 1896–1897 by irrigating 87,226 acres. In the famine
year 1877–1878 the area irrigated by productive canals was
5,171,497 acres. In the famine year 1896–1897 the area was
9,571,779 acres, including an area of 123,087 acres irrigated on
the Swat river canal in the Punjab. The revenue of the year
1879–1880 was nearly 6% on the capital outlay. In 1897–1898
it was 712%. In the same seventeen years Rx. 2,099,253 were
spent on the construction of protective irrigation works, not
expected to be directly remunerative, but of great value during
famine years. On four works of this class were spent Rx. 1,649,823,
which in 1896–1897 irrigated 200,733 acres, a valuable return
then, although in an ordinary year their gross revenue does
not cover their working expenses. Minor works may be divided
into those for which capital accounts have been kept and those
where they have not. In the seventeen years ending 1896–1897,
Rx. 827,214 were spent on the former, and during that year
they yielded a return of 9.13%. In the same year the irrigation
effected by minor works of all sorts showed the large area
of 7,442,990 acres. Such are the general statistics of outlay,
revenue and irrigated area up to the end of 1896–1897. The
government might well be congratulated on having through
artificial means ensured in that year of widespread drought
and famine the cultivation of 27,326 sq. m., a large tract even
in so large a country as India. And progress has been steadily
made in subsequent years.
Some description will now be given of the chief of these
irrigation works. Beginning with the Punjab, the province
in which most progress has been made, the great Sutlej canal,
which irrigates the country to the left of that river, was opened
in 1882, and the Western Jumna canal (perhaps the oldest in
India) was extended into the dry Hissar and Sirsa districts,
and generally improved so as to increase by nearly 50% its
area of irrigation between 1878 and 1897. Perhaps this is as
much as can well be done with the water at command for the
country between the Sutlej and the Jumna, and it is enough
to secure it for ever from famine. The Bari Doab canal, which
irrigates the Gurdaspur, Amritsar and Lahore districts, has been
enlarged and extended so as to double its irrigation since it was
projected in 1877–1878. The Chenab canal, the largest in India
and the most profitable, was only begun in 1889. It was designed
to command an area of about 212 million acres, and to irrigate
annually rather less than half that area. This canal flows
through land that in 1889 was practically desert. From the
first arrangements were made for bringing colonists in from
the more congested parts of India. The colonization began in
1892. Nine years later this canal watered 1,830,525 acres.
The population of the immigrant colony was 792,666, consisting
mainly of thriving and prosperous peasants with occupancy
rights in holdings of about 28 acres each. The direct revenue
of this canal in 1906 was 26% on the capital outlay. The
Jhelum canal was opened on the 30th of October, 1901. It is
a smaller work than the Chenab, but it is calculated to command
1,130,000 acres, of which at least half will be watered annually.
A much smaller work, but one of great interest, is the Swat
river canal in the Peshawar valley. It was never expected that
this would be a remunerative work, but it was thought for
political reasons expedient to construct it in order to induce
turbulent frontier tribes to settle down into peaceful agriculture.
This has had a great measure of success, and the canal itself
has proved remunerative, irrigating 123,000 acres in 1896–1897.
A much greater scheme than any of the above is that of the
Sind Sagar canal, projected from the left bank of the Indus
opposite Kalabagh, to irrigate 1,750,000 acres at a cost of
Rx. 6,000,000. Another great canal scheme for the Punjab
