BASIN IRRIGATION
There are two kinds of irrigation in Egypt—basin and perennial
irrigation. Basin irrigation is the ancient and historical method
of the country. Tradition ascribes its invention to the first King
of Egypt, and it is obviously designed to take full advantage of
the annual flood. Practically the same as it was 7,000 years ago,
it may be seen in Upper Egypt to-day.
The cultivable land from Assouan to the Delta is, with the exception
of the Fayoum, that altogether remarkable province, a narrow strip
of country, varying in breadth from a few miles to nothing at all,
sometimes on both sides of the river, sometimes only on one. Being
of deltaic formation, the land is highest near the river, and slopes
away towards the desert. As the river flows from south to north,
there is, of course, also a general slope of the country in the
same direction. Earthen dykes are run at right angles to the river
as far as the desert, a dyke parallel to the river and close to
its bank connects them, and so a basin is formed, enclosed on the
fourth side by the desert. Thus the land is arranged in a series of
terraces. Usually these basins are arranged in a series, one basin
draining into its neighbour, the last of the series discharging back
again into the Nile. Sometimes a second dyke, parallel to the river,
divides the lower land near the desert from the higher; sometimes
the arrangement is still further complicated by other dykes, making
enclosures within the area of the original basin.
The object of the basins is to regulate the supply of the
flood-water. Each series of basins has special feeder canals to
lead into them. These are shallow, and have their bed about halfway
between the high and low level of the Nile. They are therefore dry
in the winter and summer, and only run during the flood. The heads
of these canals, where they take off from the Nile, remain closed by
dams or by masonry regulators till the silt-bearing flood is coming
down in sufficient strength. Then about August 10 or 12 the canals
are opened and the basins filled. The lowest basins in each series
are filled first, then the next lowest, and so on. In a low flood,
as in 1877, there is not enough muddy water to go round, and the upper
basins get no water at all; such lands are called ‘sharaki,’ and
are exempt from taxation. For forty days the flood-water stands on
the land, thoroughly soaking it and washing it, and at the same time
depositing its fertilizing silt. At the end of that time, through the
escape at the lower end of the series, the water is discharged back
again into the Nile. But if the flood is a very high one or very slow
in abating, the date at which the water can be discharged and the
basins dried has to be postponed. Fortunately, this seldom happens;
but when it does it has a doubly bad effect. The oversoaking is said
to engender worms, and also the ripening of the crops is postponed
to an unfavourable season of the year.
Against this particular evil there is no remedy, but since the British
occupation a great deal has been done to improve the system of basin
irrigation, and prevent a large amount of sharaki even in years of
low Nile. These measures consist in arrangements for distributing the
‘red’ water more evenly over the whole system, and not allowing
the lower basins only to receive the full benefit, while the higher
merely receive ‘white’ water—_i.e._, water which has already
deposited its silt. Further, since any water is better than none,
the systems of basins have been so managed, where possible, that
the water from an upper system can be drained into a lower one,
and thus make up deficiencies, though with water of an inferior
quality. More attention has also been paid to the angle at which
the feeder canals take off from the Nile, and the slope on which
they are laid, so as to provide as much ‘red’ water as possible,
while diminishing the amount of silting up. The result of this work
is seen in the diminution of the sharaki lands year by year. In 1877
these amounted to nearly 1,000,000 acres, a loss of £1,000,000 in
land-tax. During the next ten years the average was 45,000 acres,
an annual loss of some £40,000. In 1888 the loss was £300,000,
and the Egyptian Government expended £800,000 in remedial works,
which have had an extraordinary effect. In 1899, when the Nile was
exceptionally low, the sharaki lands amounted to 264,000 acres only,
as against nearly 1,000,000 in 1877.
As for the high lands lying immediately between the river and the
basin dyke, only eight or nine times in a century does the Nile
rise high enough to flood them. They are called ‘berms,’ and
are ingeniously irrigated by means of special high-level canals,
which, starting from a point above the head of the basin system, or
perhaps leading down from an upper system, pass by means of a siphon
under the feeder canal. The berms are, of course, also irrigated by
lifting water directly from the Nile itself.
There are forty-five systems of basins in Upper Egypt, most of which,
and those the largest, are on the left bank. Some of the feeder
canals are insignificant, and feed only two or three basins. Others,
like the Sohagia Canal, south of Assiout, feed an extensive system,
and are real rivers when full. The basins themselves are 5,000 to
15,000 acres in extent, and it can easily be understood that when
they are taking in they have an enormous effect in diminishing
the pressure of the flood, and, on the other hand, their discharge
lengthens it out in the lower reaches of the river, when the level
has already fallen very much at Assouan. While the basins are filling
in August and September, they absorb about 2,000 cubic metres per
second. Besides this, a considerable amount is employed in filling the
channel of the Nile itself and its branches. Evaporation, absorption,
and direct irrigation, also play their part, and the result is that
the discharge of the Nile at Cairo is some 2,500 cubic metres less
than it is at Assouan. But during October and November the basins
are discharging. The southernmost ones are empty by October 15,
those in the neighbourhood of Cairo not till about November 30, or
even later. The consequence is that the Nile at Cairo in October
is discharging 900 cubic metres per second more than at Assouan,
and in November 500 more.
In November, therefore, the visitor to Cairo can still get some idea
of what Upper Egypt is like in flood-time. From desert to desert
it stretches, one vast lake, divided by a network of dykes, and
studded here and there with villages raised on artificial mounds,
which year by year rise higher on their own ruins. A greater flood
than usual makes terrible havoc in these villages; for the rising
water soon crumbles their mud walls, and the whole collapses like a
pack of cards. Every mortal thing is living on the dykes, which play
the part of roads; only the water-fowl, emerging in thousands from
their secluded marshes, spread themselves in security over the wide
waters, and here and there an isolated villager may be seen in an
ancient palm-wood tub, paddling and baling by turns. The dykes run
on the same lines as they have run for centuries, and on them the
traveller, on his way to visit the Pyramids of Gizeh or the Tombs
of the Kings at Sakkarah, the burial-ground of ancient Memphis, may
watch the whole life of Egypt pass and repass in long procession, set
as in a frieze. Work in the fields, of course, is at a standstill,
but the villages are humming with preparation for the sowing,
and alive with flocks of goats and sheep, camels, buffaloes, and
asses; even the rats have been forced to the same refuge, and may
be seen popping in and out among the roots of the palm-trees.[4]
Where one basin drains into another the fisherman spreads his net,
and reaps a rich harvest in the rush of the current. At intervals are
stationed pickets of grave watchers, squatting patiently alongside
large bundles of millet or maize stalks. This is all that remains
of the corvée service, and gladly is it borne.
For every villager is interested in the preservation of the dykes,
and apart from ordinary accidents this great lake, owing to the
swift changes of temperature in the neighbouring desert, is liable
to violent storms, which drive great waves against the crumbling
dykes, and would soon break them if left alone. The millet stalks
are put down to break the force of the waves. Each village omdeh, or
headman, is responsible for these arrangements, and he, too, may be
met upon the dykes, a picturesque figure in flowing black and white,
mounted on an ambling Arab pony, going round to see that all his
sentinels are on duty. How near the past is brought, when you enter
the tombs and find painted on the walls, or figured out in stone,
the same people engaged in the same pursuits, as though Egypt had
not been since then for thousands of centuries coveted and seized
in turn by so many invading nations! The cultivator of the soil,
moulded by the unchanging and imperious demands of the great river,
to which he owes his whole subsistence, has retained the customs,
and even the features, of those remote forerunners, who are his
ancestors in everything, except, perhaps, by descent of blood.
Under the Pharaohs and under the Romans the whole of Lower as well
as Upper Egypt was under basin irrigation, and the whole country was
cultivated. In those days Egypt was the granary of the Mediterranean,
and at the time of the Arab conquest, A.D. 700, her population was
estimated to number 12,000,000. Under Arab rule began that period
of deterioration which lasted for 1,100 years, and which, had the
system of irrigation been less natural to the physical conditions
of the country and less simple, would have resulted in an absolute
abandonment of cultivation, and reduced Egypt to the state in which
Mesopotamia, once the garden of the world, finds itself to-day. Even
as it was, by A.D. 1800 the population was brought down to about
2,000,000, and all the northernmost and greater half of the Delta
had become a neglected and uncultivated swamp. War, famine, and
pestilence, in turn, had played their part; but the fundamental cause
of all was the misgovernment, which had neglected the irrigation. For
in basin irrigation, as, indeed, with all irrigation, two things are
of the utmost importance: the first, to get the water on to the land;
and the second, to drain it off again. Salt is the great enemy to be
fought. Not only do the Nile waters contain a large quantity of salts,
in solution, but the strata underlying the alluvial deposits, being
of marine origin, are also rich in salts. If the water is allowed
to stand on the land, evaporation takes place, until nothing but
a salt efflorescence is left. While if the land be so water-logged
that the level at which water can be obtained by digging is brought
near to the surface, the water containing salts from below is drawn
upwards by means of capillary attraction, and once more evaporation
takes place, leaving the salts in the soil. It is clear that as
the natural level of the land approaches sea-level it becomes more
and more troublesome to provide proper means of carrying off the
water. Accordingly, the northernmost parts of the Delta were the
first to suffer, and gradually the line of cultivation receded.
Nor was this all. No one looking at a map of the Delta can fail
to have been struck by that extraordinary feature of the northern
coast-line, the great lakes. At the present time there are in the
Delta about 3,430,000 acres of land cultivated or under reclamation,
and another 500,000 acres of waste land. North of these lie 1,180,000
acres, either permanently covered by the lakes or else flooded
by them from September to December. Between the lakes and the sea
is a belt of sand-dunes or sandy plains, pierced occasionally by
openings. The sand-dunes are constantly being augmented by the
prevailing north-west winds. These lakes or lagoons are for the
most part extremely salt, and are distributed as follows, beginning
from the west: Lake Mareotis, 70,000 acres; Edku, 60,000 acres;
Borillos, 180,000 acres, and as much more during flood and early
winter; and Lake Menzalah on the east, largest of all, 490,000 acres,
and flooding 200,000 acres more at the same time of year. All these
waste lands, now known as the Berea, were cultivated in Roman times,
some being occupied by vineyards, others by wheat, and it would seem
that the lakes were kept from extending landwards by dykes. But
when the land was allowed to go out of cultivation no one had any
interest in looking after the regulation of the lakes. First, the
passage through the sand-dunes became silted up, because, as the
basins decreased in number, less water was drained from them into the
lakes at the time of the inundation. Then, after the closing of the
openings, the water gradually rose, breached the neglected dykes,
and completed the ruin of the land. Once the openings in the dunes
are closed, the lake has to rise to a considerable height before it
can force its way through again, owing to the continuous action of the
sand driven by the wind. In this way it came to pass that neither of
the lakes had more than one opening into the sea, and consequently,
rising in flood-time above sea-level, invaded the lands to the south.
Another cause may have possibly contributed to the same
effect—namely, a sinking of the coast lands. Nowhere is this a more
probable explanation of the facts than in the neighbourhood of Lake
Manzalah. Before the Arab conquest much of what is now a shallow lake
was famous for its gardens, palm-groves, vineyards, and wheat-fields;
besides its agricultural villages, it contained towns famous for
their cloth and cutlery manufactures, like Tunah, Damirah, Dabik,
and, above all, Tinnis. But at the time of the conquest these towns
were already islands in the lake, a position which enabled them to
be the last stronghold of Coptic resistance to the Moslems.
Whatever the cause or the combination of causes—and the history
of these tracts remains very obscure—the results were the retreat
southwards of the cultivated area, with the consequence that, after
over 1,000 years of Mohammedan rule, Egypt found herself in the
weakened and impoverished condition already described; saved only
from annihilation by the system of basin irrigation, of which the
traditions survived, though in a diminished area, stubbornly preserved
from age to age by her industrious and conservative peasantry.