376 POPULAR SCIENCE MONTHLY 



estimate of stone masonry is fifty-three thousand cubic yards and of 

 concrete one thousand cubic yards, together calling for forty thousand 

 barrels of cement. The contract for the dam, exclusive of a cut-off 

 and dike, was awarded September 1, 1905, for $482,000, the govern- 

 ment to furnish the cement at the nearest railroad point. During the 

 summer a tunnel was constructed through the canyon walls, the upper 

 portal located above and the lower portal below the dam site, for the 

 purpose of diverting the waters of the river during the construction 

 of the dam and to be used later for the passage of stored water. 



The annual run-off from the Pathfinder watershed is about 1,500,- 

 000 acre-feet, and the capacity of the proposed reservoir is 1,025,000 

 acre-feet, being sufficient to retain about two thirds of the entire dis- 

 charge of the North Platte at this point for one year. A conservative 

 estimate of the area it is possible to irrigate under favorable circum- 

 stances, with the amount of water to be stored in the Pathfinder Reser- 

 voir, lies between 300,000 and 400,000 acres. During the irrigating 

 season it is proposed to allow the surplus water stored in the reservoir 

 to escape into the river bed as needed, augmenting the normal flow, to 

 be intercepted by diversion dams and turned into the headworks of the 

 canals that are to conduct it to the lands it is intended to irrigate. 



The irrigable lands lying below the reservoir have been surveyed, 

 and wherever it seemed that any considerable area could be reclaimed 

 for a reasonable expenditure, a preliminary location of canals and 

 study of the necessary structures involved were made and the probable 

 cost estimated. Some of the schemes were rejected because of excessive 

 cost and others are in abeyance, but the Interstate Canal has been pro- 

 nounced practicable by a consulting board of engineers and is now in 

 process of construction. This canal heads at a point about eight miles 

 above old Fort Laramie in Wyoming and follows the northerly side of 

 the valley for one hundred and fifty miles to a point near Bridgeport, 

 Nebraska. The land underlying this canal in the extreme eastern part 

 of Wyoming and in Nebraska is of excellent quality, requiring but the 

 application of sufficient water to yield bountiful returns. No alkali 

 demands the construction of expensive underdrains on these lands, and, 

 with the lands south of the river and those lying higher up the valley 

 in Wyoming, there is an area sufficient to exhaust even the resources of 

 the huge Pathfinder Eeservoir. A conservative estimate of the prob- 

 able area underlying the Interstate Canal, and to receive its service, is 

 something more than 100,000 acres. The canal is designed to carry 

 about 1,400 second-feet of water at the headworks. The first forty- 

 five miles was divided into ten contracts, which were awarded during 

 the months of June and July, 1905, and construction has been in 

 progress throughout the summer, with the outlook bright for water in 

 time for the irrigating season of 1906. In November the second fifty 

 miles was awarded. There are no tunnels on the Interstate Canal and 



