DRAINAGE 



81 



This may be computed by dividing the total quantity of 

 water on an acre, for a certain standard or depth, by the 

 number of seconds in 24 hours. For convenience, however, 

 the following table is included. 



Discharge per second per acre for different depths of run-off. 



In applying the formula it is customary to assume a cer- 

 tain size of tile and then make the computation to determine 

 whether or not the tile will be sufficient. If too small, 

 another trial may be made with a larger tile. As an illus- 

 tration, suppose that the size of tile necessary to drain 80 

 acres is required, when the line is 1000 feet long and is laid 

 to a grade of 4-10 foot per 100 feet, assuming the drainage 

 standard or coefficient of % inch. 



Referring to the formula, 



V = 



