132 



DRAINAGE AND IRRIGATION 



have also been irrigated by grants of land made by the national 

 government to individual states. The states or companies char- 

 tered by them have installed irrigation systems and thus reclaimed 

 several million acres of arid land which was otherwise useless for 

 the growing of crops. Individual owners have irrigated small 

 areas in all parts of the country. 



Irrigation Systems. In large irrigation projects water is 

 stored in large reservoirs formed by the building of dams across 

 either deep gorges or shallow cuts made by streams. Some of the 



FIG. 88. Elephant Butte dam, Messila Valley, New Mexico, completed May 13, 1916. 

 It is one of the largest re-enforced concrete dams of the United States Reclamation Service. 

 In these projects the land is sold in small tracts to actual settlers only. (Courtesy Country 

 Gentleman.) 



largest and highest dams in the world are found in these projects. 

 The Arrowroc.k dam in Idaho is the highest dam in the world, 

 being 349 feet high. The Roosevelt dam in Arizona has a total 

 height of 290 feet. Another government dam at Elephant Butte. 

 New Mexico, has a total height of 300 feet (Fig. 88). This dam 

 forms the largest artificial reservoir in the world, excepting the 

 Gatun Lake on the Isthmus of Panama. The Elephant Butte 

 dam is capable of storing 2,627,700 acre-feet of water and will 

 create an artificial lake of over 40,000 acres which is, however, 

 mostly worthless land. 



