12 



inches. However, as a method of measurement, it has some advantages as 

 explained farther. 



To convert measurement from one unit into another the 

 equivalents are useful: 



I cubic foot per second is equal to 35.7 miners' inches. 



1 cubic foot per second is equal to 6.25 Imp. gallons per second, or 7.5 

 U. S. gallons per second. 



1 cubic foot per second will give in one minute, 375 Imp. gallons, or 

 450 U. S. gallons. 



1 cubic foot per second will give in 24 hours, 2 acre feet (approximate- 

 ly), or 1 acre inch in one hour. 



1 British Columbia miners' inch will give in one minute, 10.5 Imp. gal- 

 lons, or 12. U. S. gallons. 



1 British Columbia miners' inch running for 36 hours will give 1 

 acre inch. 



METHODS OF MEASUREMENTS. 



Measurements of water may be obtained by means of: 



1. Volumetric measurements. 



2. Weirs. 



3. Miners' inch boards or boxes. 



4. Special devices such as Grant-Michell meter. 



5. Measurements of velocity of water and cross section of canal or 

 flume. 



For a measuring device to be entirely satisfactory it should meet the 

 following requirements: 



1st. It should not only measure the water at any one time, but it 

 should keep a continuous record of all water delivered. 



2nd. In many cases it is desirable that it should maintain a constant 

 flow when once it is set for full capacity or fraction of full capacity. 



3rd. It should be able to handle any fraction of its full capacity. 



4th. It should not require difficult computations to obtain the results 

 of the measurements. 



5th. It should not be easily interfered or tampered with. 



6th. Where the available grade is small it should require the least pos- 

 sible loss of head. 



7th. The cost of the device should not be excessive. 



There is no device which will fulfill all these requirements. 



On the irrigated systems of British Columbia the heads of water de- 

 livered to the irrigators are usually small, in many cases only a few 

 miners' inches, and there is generally sufficient fall or grade to permit the 

 installation of any type of measuring device. The devices which are most 

 feasible at a moderate cost for delivery of water to the irrigator are the 

 weir box and the miners' inch box. 



To measure the flow of streams or canals the weir board may be used 

 when there is sufficient fall to allow its installation; otherwise measure- 

 ments of the cross section and of the velocity by means of floats or current 

 meters must be made. 



1. Volumetric Measurements. 



This method of measurement can only be used for very small volumes 

 of water. It consists of a tank of a given volume in which the irrigating 



