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AGRICULTURAL ENGINEERING 



surface of the ground is such as to give good surface drainage, 

 as where the land has a good slope. However, where natural 

 underdrainage is not provided, or where the surface is such 

 as not to provide surface drainage, artificial drainage should 

 be installed by means of tile drains or open ditches. 



Underdrains. Artificial underdrainage is generally 

 accomplished by providing conduits, as open pipes, which 

 will provide a free , and as far as possible, an unobstructed 



Fig. 43. An open drain. 



passage for the flow of the water through the soil. To 

 secure the best results, these tile lines should have as much 

 fall or slope as is practical in order to give a high velocity of 

 flow to the water within them, and they should be as straight 

 as possible and free from sags and obstructions. 



Open Drains. Open drains or ditches are simply free, 

 open channels for the flow of water, where large quantities 

 are to be cared for. They are used where a system of under- 

 drainage made of tile would not be practical. The advan- 



