IRRIGATION AND DRAINAGE 145 



in America. Because of the problems encountered, it is also 

 of intense interest. 



Two river valleys in Colorado, the Gunnison and Uncom- 

 pahgre, lie parallel. The Gunnison River carries a large 

 amount of water and it flows through a narrow precipitous 

 canyon, offering no opportunities for agriculture. The 

 Uncompahgre River carries a very small amount of water, 

 but flows through a broad and fertile valley, promising large 

 opportunities for agricultural development. The project 

 which the United States Government undertook was to bore 

 a tunnel through a range of hills separating the two 

 valleys; and through this tunnel to divert the water from 

 the Gunnison River, using it to irrigate the Uncompahgre 

 Valley. 



In the prosecution of this work, problem after problem 

 was encountered that could not have been foreseen. To 

 begin with, the task was one of great magnitude. Not only 

 was the tunnel a stupendous problem in itself, because of its 

 size, it being six and one-half miles long; but in addition, 

 intake, canal, and distributing systems had to be constructed. 

 As the boring of the tunnel progressed, unexpected problems 

 arose. Large quantities of water and of carbon dioxide gas 

 were encountered. At one point extensive layers of gravel 

 and sand were found where solid rock had been expected; 

 and the tunnel had to be lined with a thick wall of concrete. 

 Work was begun in February, 1905, but the tunnel was not 

 completed until January, 1910. 



239. Imperial Valley. The bringing of water to the 

 Imperial Valley in California is one of the best known 

 irrigation projects ever undertaken in the United States. 

 The irrigation of this valley was first attempted by private 

 capital in the year 1900. In the view of the men who under- 

 took the project, their problem was comparatively simple. 

 They diverted the water from the Colorado River by means 

 of a canal which tapped the stream, as the Colorado is a 



