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THE PRINCIPLES OF SOIL MANAGEMENT 









Fig. 87. The so-called natural or irregular system of arranging drains to remove 

 water from local wet spots. Shading indicates degrees of wetness. 



volume of water to be handled and on the fall. Where 

 several laterals empty into a main drain, the main must 

 have a capacity equal to their combined flow; but it is 

 not possible to calculate the total or relative sizes with 

 the exactness which is possible in a pressure system of 

 pipes. This is due to the effect of the soil. It acts as a 

 sponge to hold the water, and gives it up gradually. The 



