BY F A. HURLEY, F.C.H., A.M.I.C.E.

So much has been written of late years about Egypt and the Nile, that it is safe to assume that it is now a matter of common knowledge that the Nile has been the creative agency by which the land of the Pharoahs has been evolved, and is almost the sole means by which life is sustained in a country that, without it, would be as barren and uninhabitable as the surrounding desert.

Since the overthrow of the Khalifa at the battle of Omdurman in 1899, much has been learnt about the basin of the Upper Nile that was previously unknown, and any thorough description of the irrigation question in Egypt at the present day, involves a consideration of the whole river from its sources at the Great Lakes in

Central Africa and Abyssinia to the sea. Even the most meagre description of the river would, however, require much more space than is usually considered ample for a single paper. The historical development of irrigation in Egypt, moreover, took place in Egypt proper; that which depends on the Upper Nile is only in the course of development at the present day.

It is proposed to describe the irrigation system of the country and its development more from the aspect of the political economist than from that of the Engineer, and therefore no attempt is made here to deal with the general questions of the Nile. The present paper deals only with irrigation in Egypt proper, that is, that part of the Nile basin between the first cataract at Assouan and the Mediterranean Sea. In writing it, the author has drawn liberally and sometimes verbatim on most of the literature that has appeared on the subject, notably :

The Delta Barrage, by Sir H. Brown.
England in Egypt, by Lord Milner.

Egyptian Irrigation, by Sir W. Willcocks.

Administration Reports of the Egyptian Public Works

Department.

From Assouan to Cairo the Nile flows in a narrow valley, flanked, north of Luxor (the ancient Thebes), by high cliffs of white limestone, from the tops of which the true desert extends east and west. Between the foot of the cliffs and the actual channel of the river lie, first, a narrow strip of desert, and then a belt of cultivated soil which has been deposited by the overflowing of the Nile during many thousands of years.

At Cairo the cliffs recede from the river, and the valley opens out into the broad deltaic formation of Lower Egypt; the country between Cairo and Assouan being known as Upper Egypt. A few miles north of Cairo the Nile bifurcates into two main branches, called, from the names of the towns at their mouths, the Damietta and Rosetta branches.

It is almost needless to say that, as the cultivable land of Egypt has been formed by a continuous deposit from the Nile as it slopes away from the river to the foot of the desert hills.

Situated in one of the largest rainless areas in the world, the climate of Egypt, except the northern margin of the Delta, is that of the great desert area of North-East Africa, the rainfall being extremely small, and occurring mostly as occasional thunderstorms. Along the Mediterranean coast there is a considerable rainfall in the winter months, but this only extends for a short distance southwards, and at Cairo ten or twelve rainy days in a year is probably the average. South of this the amount decreases rapidly, and from Cairo to Luxor, and in the neighbouring deserts, showers on one or two days, and a very occasional thunderstorm, represent probably all that falls in an average year.

South of Cairo no regular rainfall observations have been made, but the following table gives the average rainfall for six places north of Cairo:

It will be evident that the rainfall in Egypt is, for agricultural purposes, practically valueless, and that everything depends on the water of the Nile, derived from rainfall on the upper part of its catchment area. The total area drained by the river is about 1,200,000 square miles, on which the total mean annual rainfall is about 29 inches. The heaviest rainfall occurs about Lake Victoria and Albert and about Lado and the upper halves of the Saubat, Blue Nile and Atbara, and may be taken as about 59 inches per annum. In the Eastern half of the Gazelle river, the lower half of the Saubat and middle third of the Atbara it is about 39 inches. The Western half of the Gazelle river has probably about 19 inches per annum, while the Arab river and the tail portion of the White and Blue Niles, and the Atbara cannot have more than about 10 inches. From Berber northwards the country is practically rainless.

In the great lake region the rainy season lasts from February to November, with one maximum in April and another in October. At Lado the rain continues from April to November, with a maximum in August. August is the centre of heavy rainfall everywhere, except at the great lakes. It takes 90 days for the water in low supply to reach the sea from these lakes, while in flood it takes 50 days.

Owing to the variable periodicity of the rainfall over its catchment, the floods in the Nile are neither so sudden nor so intense as might be expected from the extent of the catchment area. The Great Lake and the expanse of swampy "Sudd" south of Fashoda act as regulators in reducing the severity of the flood in Egypt.

The Nile, nevertheless, behaves in much the same manner as any other storm-fed river. At Cairo the average minimum discharge is about 12,000 cubic feet per second, and is attained about the

middle of June ; the river rises slowly through July and fairly quickly in August, and reaches the average maximum discharge of about 268,000 cubic feet per second about the beginning of October. Through October the Nile at Cairo is practically stationary, and falls rapidly in November, and continues to decrease until the arrival of the next year's floods.

In order that the Nile may exercise its powers of sustaining life and assisting plant growth, there are certain physical conditions that must exist; and these conditions are that the relative levels of land and water should be such that the water may flow over the surface of the land. Such conditions exist naturally at certain places in time of flood. When they do not naturally exist there is no active life, unless the necessary conditions are produced artifically by engineering works. Such works, of a primitive nature, resulting in the practice of irrigation, have existed from pre-historic times. Prior to 1805 the whole of Egypt was irrigated by what is known as the basin system; that is, by inundation, and depended on the height of the flood for its water supply. The country was traversed by dykes running more or less at right angles to the river, starting from its bank, and reaching the desert. A dyke running parallel with the river along its bank enclosed the basin on its river side, while the desert usually formed the fourth side. Almost all the basins had special canals leading directly into them the floods charged with alluvium, and they also possessed escapes which allowed the water, after it had deposited its alluvium, and stood some forty days on the land, to flow back to the river. On the mud thus produced the crops were sown, and received no further watering.

Certain basins that are at too high an elevation to be flooded naturally directly from the river, receive their water from basins upstream of them. By passing water from basin to basin it is possible to lead water parallel to the river at a flatter slope than that of the Nile, and thus to reach land that could not otherwise be flooded.

Under the basin system of irrigation, winter crops only, such as barley, wheat, beans and clover are grown on the lands from which the Nile flood had retired after watering them. During the reign of Mehemet Ali, however, who became Viceroy of Egypt in 1805, the development of cotton cultivation in Lower Egypt necessitated a radical change in the whole irrigation system. This crop could not be grown under the basin system, as it requires to be protected from inundation, and must be planted and irrigated before the Nile begins to rise. It became necessary to embank the branches of the river, which had previously found its way to the sea through the basins and minor channels, and to dig deep canals to bring the low-level water of the summer Nile to the crops, which were then irrigated by means of pumps. To keep the Nile bank in such repair that they could resist high floods, and to dig and clear the canals so that they should be deep enough to flow at Low Nile, was a very heavy tax on the country, and it was necessary to have recourse to some more scientific method for obtaining and distributing water.