THE IRRIGATION AGE. 



251 



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YUMA PRO JCT C 



ARIZONA V 



The work of closing the Colorado River, twelve 

 miles above Yuma, Arizona, had a most spectacular fin- 

 ish. The government engineers have been engaged here 

 for months in building a dam the like of which this 

 country has never seen before. On December 21st the 

 channel of the river was closed and the entire flow of 

 the river passed through the giant sluiceways at either 

 end of the dam. The supervising engineer wired to 

 Washington : "The river is closed and we sat on the 

 lid while a five foot rise, carrying 40,000 second feet of 

 water, passed by." 



The engineers encountered many difficult prob- 

 lems in planning the big irrigation systems which the 

 government is constructing in the arid West, but no 

 more complicated conditions confronted them anywhere 

 than in attempting to control the Colorado River in or- 

 der that 130,000 acres of exceedingly fertile soil in 

 California and Arizona might be made fruitful. 



The size and uncertainty of the river, the shifting 

 channel and unstable banks, the yearly recurring inunda- 

 tions, variations in volume from low water to flood 

 heights and the immense volume of silt carried by its 

 yellow waters, made the problem of the control of the 



stream unique in the history of American irrigation. 

 With these difficulties fully understood and no bedrock 

 for a base, the problem presented to the engineers was 

 to build a structure on the sand and silt that would 

 fully control the river, holding it within certain pre- 

 scribed limits, and at the same time make some disposi- 

 tion of the silt, one of the most difficult features of the 

 undertaking. 



Constructing Engineer E. D. Vincent gives the fol- 

 lowing description of the structure : 



"The most advantageous weir site was found to be 

 at Laguna, twelve miles above Yuma, where granitic 

 mountains encroach on the river valley, leaving an open- 

 ing about a mile wide. The type of weir selected was 

 one that has been in successful operation for many years 

 in India and Egypt under practically identical condi- 

 tions with those presented in Yuma Valley. ,' ' 



"Three concrete core vails 4,800 feet in length and 

 57 and 93 feet apart extend from bluff to bluff. The 

 crest wall with a maximum height of 19 feet above the 

 bed of the stream, rests upon a row of 6-inch sheet 

 piling from 12 to 20 feet in length, incorporated in its 

 base to cut off seepage. The space between the walls is 



