THE DRAINAGE OF FARM SOILS 209 



much inconvenience and useless digging when the 

 drains need attention later. 



THE OUTLET 



The first point to look after is the outlet; the 

 water must DC carried off after it is collected by 

 the tiles. More than one drainage system has 

 given poor service solely because a suitable outlet 

 was not provided. The channel into which the 

 drainage system discharges may be a natural water 

 course, as a river, creek, brook, or rill, or it may be 

 an open ditch constructed for the purpose. If a 

 natural water course, it is very essential that the 

 outlet of the drain be at least several feet above 

 the highest point at which the water in the stream 

 has been known to stand. This precaution is 

 necessary to prevent the stream water from backing 

 up and filling the lower end of the drainage system, 

 wnich not only prevents the drainage water from 

 escaping, but also allows the stagnant water to 

 deposit sediment on the bottom of the tiles and 

 choke them. All the water in a tile drainage 

 system should be in motion all the time. 



The outlet is the most vulnerable part of a 

 drainage system; it is the only part that comes to 

 the surface. Hence it will pay to deepen and 

 straighten the course of the stream at that point, 

 if necessary, in order to make it doubly sure that 

 the drainage water will meet no obstruction in 

 passing from the outlet. For the same reason it 

 is usually best to have as few outlets as possible; 

 to collect the water from many or several lines 

 or systems of drains into one main with a single 

 outlet. Sometimes, however, it is cheaper to have 

 several outlets, one for each system, instead of 



