Measurement of Water 241 



United States is the miner's inch, which is the amount 

 of water which may flow through an opening 1 

 square inch in section in one second under a certain 

 pressure or head. But the legal pressure varies in 

 different states ; hence, the miner's inch has not a 

 fixed and definite value. In California 50 miner's 

 inches are usually counted equivalent to 1 second -foot, 

 while in Colorado only 38.4 statute inches are required 

 for a second -foot. 



Where a larger unit of measure is desired than 

 either of those named, ' the acre-foot is sometimes 

 used. This is an amount of water required to cover 

 an acre 1 foot deep, and is, therefore, equal to 12 

 acre -inches. 



METHODS OF MEASUREMENT OF WATER 



Much and long as irrigation has been practiced, and impor- 

 tant as the subject is, especially in communities where water 

 is scarce and where each user has need of every drop of water 

 he can get, there appears even yet to have been devised few 

 methods of measuring or of apportioning water among the users 

 which possess the degree of precision which could be desired. 



In the case of individual irrigators, where the water is 

 pumped and stored in reservoirs, to be used as desired, the area 

 of the reservoir and the amount the water is lowered in it fur- 

 nish the needed data for determining the amount which has 

 been applied to a given area of land. Or, in the case of direct 

 application of the water pumped to the land, the rate of the 

 pump may be known, and thus, through a knowledge of the time 

 of pumping, furnish an approximate measure of the water used. 

 In the great majority of cases, however, a knowledge of the 

 amount of water used in irrigation must be gained in some other 

 way. 



