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IOWA DEPARTMENT OF AGRICULTURE. 



TABLES AND EXAMPLES FOR TILE DRAINS AND OPEN 



DITCHES. 



TABLE l-NCJMBER OF ACtiES DRAINED BY TILES REMOVING ONE- FOURTH 

 INCH DEPTH OF WATER IN TWENTY-FOUR HOURS. 



The above table is computed from the form of Poncelet's formula recommended f o r 

 use with tile drains by C. G. Elliott, drainage expert to the U. S. Agricultural Depart- 

 ment, Washington D. C, who recommends the above sizes to drain ground water only. 

 If surface water is also to be removed, as in the case of ponds without other outlets, the 

 tiles will drain safely only one-half to one-third the number of acres given in the table. 



When part of the land in the water shed is rolling, not requiring tiling, count only 

 one-third of such rolling land, in addition to all of the low, flat land, in getting the size of 

 tiles to remove ground water only. 



Example 1. What size of tile laid to a 0. 1 % grade will carry the underdrainage of 160 

 acres of flat land? Answer 15 inches. 



Example 2. What size of tile to a 0. 2 % grade will carry the underdrainage of 240 

 acres, two-thirds rolling? Answer 80 acres flat land plus one-third of 160 acres rolling 

 gives 133J^ acres requiring a 12-inch tile. 



Example 3. What size of tile laid to 0.3 % grade will be required to remove both 

 ground and surface water from a pond whose water shed includes 40 acres? Answer 10- 

 inch. (Note.— Double or triple the area for both ground and surface water). 



Note. —If it is not practicable to use such a large tile as is required to carry a large 

 amount of surface drainage, a broad shallow depression, cultivated or kept in grass, may 

 be maintained alongside of the drain to carry the surface overflow from heavy rains. A 

 12-inch tile may thus often be used in place of the expensive 15-inch or 18-inch tile. 



