KINDS OF DRAINS 129 



measured. The outlet of the main drain must first be determined. 

 The length and number of lateral drains running to the main 

 drain should also be determined. If tile drains are to be used the 

 cost of material, as well as an estimated cost of digging and closing 

 ditches, and the cost of placing the tile, is easily determined. 



After thus estimating the elements of cost for any drainage 

 project it is wise to estimate the increased price of land result- 

 ing therefrom. This should be measured by its probable crop- 

 producing ability, and should not be based upon speculative land 

 values. Usually when such calculations are made in advance the 

 profits from any drainage project are great enough to fully warrant 

 the cost. The increased price of land is so great, and the cost 

 of drainage so small, that results are usually very favorable. 





FIG. 85. Students placing tile in ditch for land drainage. 



Kinds of Drains. There are two main types of artificial 

 drainage in use: (1) Underdrainage; (2) open ditches. These 

 two methods may be combined in the same project. The main 

 drain may be an open ditch with lateral underdrains leading to 

 it. This is most desirable where the quantity of water to be 

 carried by the main may be very great during the rainy season. 



In small drainage projects it is usually best to use underdrains 

 (Fig. 85) . This type has several advantages over the open system : 

 (1) No area of land is wasted if the drains are covered. (2) There 

 is no waste time and labor of man and teams in farm work because 

 of open ditches. (3) There are no strips left for the growth of 

 weeds. (4) The cost of repair is reduced. (5) The results in 

 actual removal of soil water are better. 

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