NATIONAL EECLAMATTON OF ARID LANDS. 481 



Scottsbluff. Minatcire, Bayard, and Bridgeport, Nebr. The distance 

 by the raih-oad between old Fort Laramie and Bridgeport is about 

 90 miles. Each of the towns named are from 10 to 15 miles apart. 

 They are similar at present, and no one town appears to have the 

 advantage over the other. The largest have a population of about 

 1,000 persons. The railroad, which extends the entire length of the 

 project, was built in 1899, at which time the above-named towns were 

 established. No material growth occurred in the valley, however, 

 until 1904, when the Government began work, since which time all of 

 the towns have more than doubled in population. 



CALIFORNIA-ARIZONA. 



Yuma jyroject. — A very general interest is being shown in the work 

 of the Eeclamation Service, on what is called the Yuma project in 

 Arizona and California, in the valley of the Colorado River. The 

 engineering works are unusual and unique, occasioned by the difficult 

 physical conditions and the immense flood discharge of the Colorado 

 River. 



The work of the engineers was greatly complicated by the unfavor- 

 able character of the bed of the river, the diamond drillers having 

 sought in vain for solid rock upon which to rest a dam, and, further, 

 by the fact that a large area of the bottom lands are annually inun- 

 dated in times of flood. These conditions necessitated the construc- 

 tion of a dam of a type never before attempted in this country, and 

 also the building of many miles of levees to protect the lower lands 

 from flooding. 



The Laguna dam is of the India weir type, which has been tried 

 successfully during the jDast fifty years at numerous jDlaces in India 

 and Egypt under similar conditions. It consists of a loose rock 

 structure with a paving of stone 1^ feet in thickness on the down- 

 stream slope, tied together with three parallel walls of steel and 

 concrete running longitudinally betwen granite abutments on the 

 two sides of the river. The dam will have a length of 4,780 feet, a 

 height of 19 feet, and a maximum width up and down stream of 257 

 feet. It will contain 356,000 cubic yards of loose rock resting upon 

 a foundation of sand. The estimated weight of the structure is 

 600,000 tons. 



This dam is not designed for storage, but will create a settling 

 basin of relativeh^ quiet water 10 miles in length above it. The 

 Colorado River carries enormous quantities of silt, and to prevent 

 this sediment from filling the canals sluiceways have been designed 

 especially for this purpose. At each end of the dam, and constructed 

 in solid rock, wall be a sluiceway 3,000 feet long, 200 feet wide, and 

 over 12 feet deep, excavated to the depth of low water in the river. 

 SM 1906 31 



