386 THE YUMA RECLAMATION PROJECT. 



Avater into the canals b}^ a skinnning process over a long row of gates, 1 

 so that the entire capacity of the canal can be furnished by drawing 

 but 1 foot in depth of water from the surface of the river. Every por- 

 tion of this weir and headworks, as designed, Avould be of rock, con- 

 crete, or steel, with the exception of the sheet piling, which will be 

 driven entirely below the water level, and so will not decay. . Every 

 portion of the Aveir Avill be what is known as permanent construction. 

 Such character of work Avill, of course, be expensive, but it has been 

 proved to be sound economy to build in this way. 



The capacity of these canals at their intakes Avill be 1,G00 cubic 

 feet per second on the Arizona side, and 200 cubic feet per second 

 on the California side. The amount of silt that would be daily 

 deliA'ered into the Arizona Canal, if diversion were made directly 

 from the stream, would approximate 17,000 cubic yards of wet mud 

 l)y volume. It is not believed to be possible for a canal to continu- 

 ously operate successfully for the iri'igation of lands along the val- 

 leys of the Colorado River unless some very substantial arrangements 

 are made at the headworks for tlic handling of silt, and this is 

 believed to be a justification for the expenditure proposed for these 

 headworks; also the water must be held to a fixed level at the canal 

 heading for all stages of the river. This structure Avill cost approxi- 

 mately $1,000,000. It is not considered possible to remoA^e all of the 

 silt from the Avater, but the canals have been designed so that the 

 A'elocities Avill be sufficient to couA^ey through to the fields the light 

 material entering the canals from the intake. 



Careful study has been made of the existing canals in the A'icinit}^ 

 of Yuma and Imperial to determine the shape that they naturally 

 assume, and the roughness of the bottom and sides, Avhich tends to 

 retard the A^elocity. Based upon these data, the canals have been so 

 designed as to carrA^ Avater at a higlier A^elocity throughout than Avill 

 be found in the settling basins above their head, and of such velocity 

 as Avill permit of a minimum loss by seej^age and eA'aporation. The 

 gates and drops of these canals and the Yuma bridges are designed 

 as steel concrete structures. A distribution system has been esti- 

 mated upon to furnish Avater to each IGO-acre tract. There will be 

 small areas of land in the upper (jila Valley, and beloAv Yuma, that 

 Avill have to be serA^ed by pumj^ing ])lants, lifting the Avater from 

 T) to 7 feet. The poAver for doing this will be furnished from a 

 Avater-power plant to be erected above ^'uma at a di'op in the main 

 canal. This power plant Avill also be used in connection Avith the 

 drainage system. 



One of the most difficult problems in connection Avith this project 

 is the crossing of the Gila Kiver. It has been considered necessary 

 (o make (his pei-fcclly safe, and foi- this puri)Ose a structure has been 

 designed that will cross beneath the bed of the river, the top to be 



