476 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1915. 



amount eventually to be repaid by the irrigators for the construction 

 and operation of the project works. 



Except for a few minor details the project is regarded as complete, 

 and in 1915 about 190,000 acres were actually irrigated. Crops 

 worth from four to five million dollars are annually harvested from 

 the irrigated lands, the cultivation of which is practically continu- 

 ous, permitting the sowing and harvesting of two different crops in 

 the same field within the year. A wide variety of products are 

 grown. Alfalfa occupies about one-half the producing acreage, yield- 

 ing as many as five or six cuttings annually. For this the farmer 

 may secure an average price of $6 per ton, but it is better practice 

 for him to feed the hay and market his output in the more concen- 

 trated and profitable form of live-stock products. In 1914 cotton 

 growing had reached extensive proportions on the project, the crop 

 from 11,500 acres bringing a return of $715,000, but the drop in price 

 attributed to the European war has led to the substitution of other 

 crops. Of the grains, barley, wheat, and the sorghum corns are the 

 largest producers. The warm climate lends itself to the growth of 

 citrus as well as deciduous fruits and producing trees have been es- 

 tablished on a considerable acreage, which is expected to increase 

 materially in future years with a gradual development toward in- 

 tensive agriculture. 



YUMA PROJECT, ARIZONA AND CALIFORNIA. 



Above Yuma, Arizona, has been constructed the Laguna Dam, a low 

 ovei^ow structure of the Indian weir type, 4,780 feet between abut- 

 ments and 260 feet up and down stream, with a maximum height of 

 40 feet. This turns the water into canals on both sides of the river 

 for irrigation in Arizona and California. The main canal heads on 

 the California side, and after covering lands on that side crosses the 

 river by means of an inverted siphon. This structure, completed in 

 1912, consists of two circular concrete shafts connected by a circular 

 concrete-lined tunnel 14 feet inside diameter and 930 feet long. The 

 siphon delivers water to the canal system covering the largest portion 

 of the project in the Yuma Valley, Arizona. On account of the low 

 elevation of the irrigable lands and their consequent liability to 

 overflow from the Colorado River it is necessary to provide an ex- 

 tensive system of river-front protection. The principal work during 

 recent years has been on this feature and the extension of the canal 

 system, which is now competent to water 70,000 acres. This will be 

 extended to cover about 90,000 acres, and an additional 40,000 acres 

 on the Yuma Mesa may be reached by pumping. 



About 30,000 acres have been irrigated and the annual crop yield 

 is approaching a million dollars. As at Salt River alfalfa is the 



