THE NILE RESERVOIR DAM AT ASSUAN". 5J^5 



Central Africa. Bolo\t A.s.suaii a weir has already l)eon l)iiilt at Assiut 

 and one its under constinictjon at Zit'ta. Tbe.se weirs are desi^'iied to 

 raise the level of the Nile at low water to till the irriuating- canals 

 already in operation or to he consti'ucted. As a safety valve, to let 

 the hig-hestand destructive Hoods escape, a plan is under consideration 

 to construct a canal to Wady Rayaii, a depression in the Sahara to the 

 Avest of the Nile Valley, and drain into it the excess of water which 

 w<mld otherwise damage Middh^ and Lower Egypt. . 

 To again (juote from Mr. \Villcocks: 



"The Assuan dam is a work of a type designed for the conservation 

 of the Hood waters and wdiich is new in the world. If successful it 

 will mark an epoch in dam building. There must be sites on the tor- 

 rential rivers of the arid and semiarid regions of South Africa, Aus- 

 tralia, and North America, where dams of the type of the one at 

 Assuan will supply a want which has long l)een recognized. 



"A reservoir dam, which will allow the earlier floods laden with 

 deposits a free and unimpeded passage and which will afterwards 

 captivate the comparatively clear waters of the terminal inundations 

 and early percolations and store them for subseiiuent use, ought to put 

 new life into many abandonetl projects for perennial irrigation. But 

 the provision of perennial irrigation is not the only ()l)ject for which 

 this type of dam may be employed. Provided with its numerous Hood 

 openings, it may be looked upon as a weir capable of controlling the 

 mightiest rivers in Hood just as ordinary weirs control them in times 

 of low supply; it may thus \)o utilized for the regulation of Hood sup- 

 plies of rivers and for their employment in basin or inundation irriga- 

 tion. As designed for Assuan, its use is restricted to sites where 

 broad platforms of sound rock can be coimted upon, but designed in 

 'l)cton armee' or "ribbed concrete.*' I hope to see it utilized in 

 narrow gorges and throttled valleys, where £20 will go as far as €50 

 in a broad platform." 



Unfortunately, in America the characteristics of our rivers, their 

 Hoods and the amount of sediment carried, are not as well known as 

 they should be; but each yt^ar adds volumes to our knowledge of these 

 streams, and by the time any extensive system is to be put in opiM-ation 

 our knowledge will be much more complete. 



