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.
PL. XVI.
WADI RAYAN RESERVOIR
LONGITUDINAL SECTION OF PROPOSED CANAL