652 SOILS: PROPERTIES AND MANAGEMENT 



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(2) Q = oF 



-f-544 



yl = acres to be drained 



C = coefficient of drainages selected for the area in 

 cubic feet per second. It is determined by 

 the depth of water to be removed in twenty- 

 four hours 



Q = quantity of water the tile will discharge, in 

 cubic feet per second 



a = area of tile in square feet 



V = velocity in feet per second 



d = diameter of tile in feet 



/ = length of tile in feet 



h = head, or difference in elevation between outlet 

 and upper end, in feet 



b = sum of amounts of head in laterals, in feet 



n = number of laterals 



K = depth of tile below soil surface at upper end, in 

 feet 



48 and 54 are factors that take account of gravity, 

 the size of the tile, and the roughness of the 

 walls. The former figure is larger for tile 

 more than twelve inches in diameter. 



The first formula determines the number of acres that 

 a given size of tile will drain, by dividing the quantity 

 of water to be removed by the coefficient of drainage 

 selected for the region. 



