98 



It is not to bo inferred that this increase was derived wholly from 

 return waters which were for a time absorbed in the subsoil of 480 

 square miles of porous lands. A large part was undoubtedly due to 

 seepage losses from the irrigated farms in the same valle3% 



That the conditions which obtained on Bitter Root River in 1903 are 

 not unusual is evidenced by similar conditions which have been shown 

 to exist on other western streams." 



Fig. is.— Loss by absorption and gain by seepage in 48 miles of Bitter Root River, from June 12 to 



August 12, 1903. 



CONCLUSIONS AND RECOMMENDATIONS. 

 WASTE OF WATER. 



According to the authoi-'s estimate, the total area that is ever likely 

 to be irrigated in Montana from streams, reservoirs, and wells will 

 not exceed 6,000.000 acres, while the fertile and arable land that might 

 be irrigated may comprise three times this area. The reason for this 

 low estimate is the smallness of the water supph^, the short period of 

 plant growth, and the fact that the large tracts of irrigable land are 

 not always accessible to the large streams. This estimate was ba.sed 

 on an average supply of 2 acre-feet of water for each acre of land, 

 which may be regarded as the mininumi quantity required under the 

 most economical use which is to ])e expected. 



The average quantity diverted per acre irrigated, as shown by the 

 measurements reported in the preceding pages, is 4.1 acre-feet, or 

 more than twice the quantity used in the estimate (see p. 12). In so 



a See U. S. Dept. A^r., Office of Experiment Stations Bui. 158. 



