Now 60 days is given as the critical period in Lower Egypt, when the Nile supply is generally insufficient. Subtracting 160 million cubic metres for the Fayûm, the 2000 million cubic metres remaining would therefore give an average discharge of 33 million cubic metres a day to supplement the Low Nile, and, if distributed in increasing quantities in proportion as the Nile fell, it might be so arranged as to prevent the Nile minimum discharge ever falling below 50 million cubic metres a day in the very lowest years of summer Nile. But calculating with a period of 100 days, which is the length of the critical period for Upper Egypt, we obtain a mean discharge of 20 million cubic metres a day, which might be so distributed as to prevent the minimum Nile falling at any rate below 45 million cubic metres a day, as for instance below:— --+---------------+-----------------------+------------+----------+-- | |Minimum Nile Discharge |Supplied by | Total | | Month. | without Reservoir. | Reservoir. |Increased | | | Monthly Average. | |Discharge.| +---------------+-----------------------+------------+----------+ |March | 40,000,000 | 5,000,000 |45,000,000| | | | | | |April | 35,000,000 | 10,000,000 |45,000,000| | | | | | |May | 25,000,000 | 20,000,000 |45,000,000| | | | | | |June | 20,000,000 | 25,000,000 |45,000,000| | | | | | |10 days of July| 30,000,000 | 15,000,000 |45,000,000| --+---------------+-----------------------+------------+----------+-- This disposes of 1975 millions, whereas 2000 millions was the quantity calculated as being available after loss by evaporation in the lake, and by absorption and evaporation in the distributing canals outside the lake. I think, therefore, I have not overstated the capabilities of the reservoir as a feeder to supplement the Low Nile. I have said nothing about the first filling of the lake, which is a question of no small difficulty. To fill it to R.L. 21·00, its low summer level when once in working order, would require a volume of 15,000 million cubic metres plus the quantity required to meet loss by evaporation during the time of filling. (3) The idea that the depression might be converted into a cultivated basin is, I think, not likely to get beyond the stage of suggestion, as, with the object only of extending cultivation, the expense of connecting the Wadi Raiân with the Nile will not be incurred, since there are so many other projects of reclamation, which would need less expenditure and give a better return.