11 



a carrying capacity of 1 cubic foot per second. In any case the cross sec- 

 tional area in square feet multiplied by the velocity in feet per second will 

 give the discharge in cubic feet per second. 

 2. The British Columbia Miners' Inch. 



The legal value of the miners'/inch in the Province of British Columbia 

 is the quantity of water that will pass through an orifice two inches high 

 by half an inch wide made in a two inch plank, the water to have a con- 

 stant head of seven inches above the upper side of the orifice, and every 

 additional inch of water shall mean so much as will pass through the said 

 orifice extended horizontally half an inch. 



In cubic measurement one inch of water shall mean a flow of water 

 equal to 1.68 cubic feet per minute. This is equivalent to 35.7 miners' 

 inches for one cubic foot per second. 

 3. Acre Foot. 



This unit of measurement is the best unit for measurement of larga 

 volumes of water at rest and is the legal unit in British Columbia (Water 

 Act 1909). It may be defined as the quantity of water which will covei' 

 one acre to the depth of one foot; it is equal to 43,560 cubic feet. 



An acre inch is equivalent to 1-12 of an acre foot. It is equal to the 

 quantity of water which will cover one acre one inch deep. 



4. Relation Between Cubic Foot Per Second, Miners* Inch and Acre Foot. 



The cubic foot per second and the miners' inch indicate only a rate of 

 flow and to specify any fixed quantity it is necessary to state the time or 

 duration of flow. For instance a flow of 1 cubic foot per second will give 

 in one 24 hour day as many cubic feet as there are seconds in that time or 

 86,400 cubic feet which is equal to nearly 2 acre feet or 24 acre inches. 

 In other words a flow of 1 cubic foot per second in one hour will give a 

 quantity of water sufficient to cover one acre to a depth of one inch. 



The miners' inch as defined by the Water Clauses Consolidation Act, 

 1897, is equal to about 1-36 of a cubic foot per second, or one miners' inch 

 in thirty-six hours will give as much as one cubic foot per second in a period 

 of one hour, which quantity is about 1 acre inch. As a unit of measure- 

 ment the miners' inch is condemned by many engineers. While there are 

 some objections there are also many advantages in its use. The objec- 

 tions usually raised are: 



First. That its value in British Columbia and in the different western 

 states of the United States is not uniform. 



Second. That the unit is associated with a measuring device and un- 

 less the factors controlling the method of measurement are correctly pre- 

 scribed by law and followed in making the measurement, it is liable to 

 give inaccurate results. The Consolidation Act of 1897 requires that it be 

 measured through a board 2 inches thick. This, as explained farther, is 

 objectionable and greater accuracy would be obtained by using a thin board 

 not over 1 inch thick. 



Third. The term has often been confused with the cross sectional area 

 in square inches of a flume or pipe. For instance if a flume is 10 inches 

 wide and 6 inches deep: it is sometimes wrongly stated by some irrigators 

 that there are 60 miners' inches, the irrigator not thinking that the flow is 

 also dependent on the velocity of the water which varies with the grade of 

 the flume. 



The main advantage of this unit of flow is that for small flows the irri- 

 gator has a better understanding of its volume when stated in miners'" 



