164 



Nature-Study Agriculture 



The Roose- 

 velt dam 



FIG. 129. The Roosevelt Dam. While such a dam is being constructed, the 

 river is generally carried out of its course by means of a tunnel that pierces the 

 mountain side. 



ment projects." (" Carey Act projects " are works of 

 reclamation undertaken by private companies under 

 state supervision by an arrangement with the Federal 

 government.) Already thirty irrigation projects furnish 

 water for three million acres, upon which in one year 

 crops worth eighty million dollars are raised. 



One of our largest dams is in Arizona, across the Salt 

 River. It was built by the government and was 

 named in honor of Theodore Roosevelt, who in 1911 

 formally opened its floodgates (Fig. 129). The water 

 held back by the dam makes a lake from one to two 

 miles wide and twenty-five miles long. This irrigation 

 system furnishes water for two hundred and twenty 



