144 



FORESTRY AND IRRIGATION 



March 



as the Laguna is being constructed 

 about twelve miles above Yuma by a 

 New York contractor, and is notable 

 as being the first of its type built in 

 America. The diamond drillers sought 

 in vain for bed rock .formation in the 

 channel and finally the government de- 

 cided upon a structure of the East In- 

 dia weir type patterned after the dams 

 built under similar conditions in India 

 and Egypt by the English engineers. 



The Laguna dam will be 4,780 feet 

 long, 19 feet high, with a maximum 



Unprecedented floods during the 

 past year have emphasized the impor- 

 tance of safe-guarding the construc- 

 tion of the levees which are required 

 to prevent inundation of valuable low- 

 land areas. The problem is complicat- 

 ed because of the fact that the area to 

 be irrigated is in the drainage basin of 

 two important streams, the Gila and 

 Colorado Rivers, both subject to sud- 

 den and tremendous floods. 



The main canal of the project will 

 cross the valley of the Gila in a pres- 



Scene in the Valley of the Lower Colorado River Below Yuma Dam Site 



width of 267 feet and will contain 

 356,000 cubic yards of loose rock. It 

 will rest on a foundation of sand and 

 will weigh approximately 600,000 tons. 

 The settling basin formed by this 

 structure will be one mile wide and ten 

 miles long. To avoid the enormous 

 quantities of silt carried by the Colo- 

 rado and which would quickly fill up 

 the canals, the headgates are so ar- 

 ranged as to draw off only the top foot 

 of water into the canals. 



sure pipe passing under the stream. 

 The Gila is normally dry or nearly so, 

 but when in violent flood, frequently 

 changes its course so that the levees 

 must be placed so as to confine the 

 stream to a definite channel before 

 building the crossing as it might other- 

 wise change its course and leave the 

 crossing to one side. The crossing 

 must be made during the coming win- 

 ter and the dykes must be built in the 

 spring and summer. 



