During the summer season 1½ to 1 million cubic metres per day (713 to 409 cubic feet per second).
The ordinary and maximum and minimum levels of the Bahr Yûsuf are given in the list below:—
| Below Derût. | Above New Bridge, Lahûn. | Below Old Bridge on Fayûm Side. | |||
|---|---|---|---|---|---|
| Flood season | 46·75 | 26·50 | 23·90 | ||
| Winter | 43·00 | 24·14 | 23·15 | ||
| Summer | 42·15 | 22·90 | 22·50 | ||
| Maximum | 46·95 | 27·80 | 23·90 | ||
| Minimum | 41·67 | 22·50 | 22·27 |
The Bahr Yûsuf inside the Fayûm.—At the end of the Bahr Yûsuf at Medineh the water-level is now kept constantly at R.L. 21·70 to 21·80. In Nile time any increase on this tail level is forbidden by the effect of the heading-up caused by the obstructions met with by the large flood discharge in its passage through the town between the houses which line its edges. The Bahr Yûsuf is bridged in this length twice, first by a three-arched bridge, [Plate II.,] which carries the main street and bazaar of Medineh; and again by a two-tubed tunnel, over which the mosque of Kait Bey is built, [Plate III.]
In passing through the bazaar with shops on either side the Bahr Yûsuf is crossed without its being noticed, and a stranger to the town is presently surprised to find himself on the other side of the canal to which he imagined himself to be.
Plate III.
TUNNEL ON BAHR YÛSUF,
OVER WHICH THE KAIT BEY MOSQUE IN MEDINET EL FAYÛM IS BUILT.
The waterways of these two constructions are sufficient to pass the winter discharge with but slight heading-up, but when the flood supply is flowing, they (assisted perhaps by old blocks of masonry and débris of fallen houses in the channel) cause a backing-up of the water of from 50 to 60 centimetres and thereby (with the level at the tail below the town fixed at R.L. 21·80) produce the maximum level above the town, which it is safe to allow.