482 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1915. 



arch 218 feet high and 432 feet along the crest. Near AVhalen, 

 Wyo., a diversion dam supplies the Interstate Canal, a notable irri- 

 gation conduit with a capacity of 1,400 cubic feet per second at 

 its head. The canal is over 100 miles long and serves 130,000 acres 

 in the two States. It takes several days for water entering the 

 headgates to reach the end of the ditch, and several small reservoirs 

 have been constructed along the canal to provide temporary storage 

 and better regulation of the flow. These reservoirs, the lower part 

 of the canal, and related distributaries have been built since the 

 former reports in this series. Other construction has included drain- 

 age works, and work is now starting on a large unit on the opposite 

 side of the river. Here the Fort Laramie Canal will take out from 

 the river at the Whalen Dam. It will exceed the Interstate Canal 

 in length and furnish water to an area of 100,000 acres. 



In addition to supplying the Government project of 230,000 acres, 

 the Pathfinder Reservoir provides sufficient stored water to supple- 

 ment the supply of a number of private canals along the river to 

 which rights have been sold under the provision of the Warren 

 Act of February 21, 1911, the receipts entering the reclamation fund. 



The area actually irrigated by the North Platte project is now 

 increasing about 5,000 acres each j^ear, and the annual crop value 

 reached $1,000,000 in 1915, when 70,000 acres were harvested. Alfalfa 

 and grain are extensively grown and used to fatten stock for mar- 

 ket. Flog raising has become an important and profitable industrj^ ; 

 during the last six months of 1914 shipments to market averaged 

 over 20 carloads, representing monthly receipts of $30,000 from this 

 industry alone. 



TRUCKEE-CARSON PROJECT, NEVADA. 



On this project the Lahontan Dam has been recently built, being 

 completed in 1915 (pi. 10, fig. 1). The structure is a large earth 

 embankment, with rock and gravel paving, 124 feet in maximum 

 height and 1,400 feet long. The most interesting feature of the 

 structure is the provision for passing excess flood water without 

 injury to the dam directly or by erosion of the relatively soft mate- 

 rial composing the river channel and canyon walls. For this pur- 

 pose concrete spillway channels leading from each end of the dam 

 are built in steps, dropping the water to a concreted stilling pool 

 below the structure (pi. 10, fig. 2). The reservoir impounds the 

 flow of Carson River and also receives the water brought from the 

 Truckee through the Truckee Canal, built some years before. Prior 

 to building the reservoir a hydroelectric plant was erected to utilize 

 the drop from Truckee Canal to Carson River and the power thus 

 developed was used in the construction of the dam. 



I 



