CROSS SECTIONS OF LAHÛN BANKS.
It is evident, from the remains of canals along the north and south sides of the Fayûm, that at some time or other these slopes of the province were irrigated to higher levels than the limit of the present cultivation. On the right the old Bahr Wardan is traceable from its old mouth on the Bahr Yûsuf (Kom-el-Iswid) above the present Sêlah Head as far as the north-west corner of the Fayûm depression. It would appear that the water surface level of the Bahr Yûsuf at Hawârah must be lower now than when this canal was under conditions favourable for irrigation. Perhaps it worked when the regulator was, as supposed, at Hawârah, and before the Lahûn bank and old bridge shut out the high-level waters of the Nile flood.
On the south side of the Fayûm there are similarly the remains of an old canal within the limits of what is now desert. This was probably fed by an aqueduct formed along the top of the Minia wall, which held up the waters in Hod-el-Tuyûr. This wall and aqueduct were breached, and though the wall was restored, the aqueduct was not, and the supply was cut off from the high-level canal. The land depending on it consequently returned to desert. Large blocks of old masonry lying prone on the ground at some distance from the present wall show with what force the escaping waters must have rushed through the breaches to have been able to transport such massive blocks to so great a distance from their original position.
CHAPTER V.
THE FAYÛM IN THE FUTURE, AND POSSIBLE UTILISATION OF THE WADI RAIÂN.
The subject of storage reservoirs for husbanding the flood or winter surplus waters of the Nile with the object of supplementing the Low Nile is now under consideration and sub judice. Mr. W. Willcocks, M.I.C.E., has been appointed Director-General of Works for the study of this subject, and his final report has not yet been made.
It has been calculated that the total of the Nile discharges for even a minimum year is more than sufficient for all the needs of Egypt, developed to its fullest extent, and the main question to decide is where the reservoir is to be made and what form it is to take.
Portions of the Nile Valley itself could be made to store the water by forming one or several masonry dams across the Nile, and the Wadi Raiân could also be made to serve the same purpose by putting it into communication with the Nile by means of a channel cut in the range of hills which divides the depression from the Nile Valley.
The discussion of the advantages of the different methods of forming Nile reservoirs does not belong to this paper, but there is a probability that a reservoir in some form will be made, and that the Fayûm will receive its share of the resulting increase of the summer water supply. Its present summer supply would probably be doubled, which would enable the province to increase the area under cotton from about 50,000 to 100,000 feddans, but would otherwise have no great effect on the province. The expansion of the present area under cultivation in the Fayûm to the lands along the north-east and south borders of the province does not depend so much on an increase to the present supply as on the construction of canals designed to carry sufficient water at a high enough level to command the lands above the present limits of cultivation. There is no want of water during Nile flood time outside the intake of the Fayûm, but its present canals will not carry more than a total discharge of 7,000,000 cubic metres a day, and therefore that is the maximum allowed to pass through the Lahûn bridges.