566 IOWA DEPARTMENT OF AGRICULTURE 



3. Avoid short laterals where a system can be adopted in which long 

 parallel laterals can be used. This is a matter that has to do with the 

 economy of the work rather than with its eflBciency. 



Every main or submain will itself drain the land for a certain dis- 

 tance on either side of it. All laterals, in order to reach these mains, 

 must be laid through the belt of land thus drained, and hence a part of 

 each lateial will be useless except to conduct the water to its receiving 

 drains. 



The fewer junctions there are in a given tract the less waste of length 

 of lateral drains there will be. 



There are localities where, on account of the contour of land, the 

 short laterals are necessary. 



4. Make the lines as straight as practicable, and change direction by 

 easy curves. Drains can not always be made straight from one end to 

 the other, yet short crooks should always be avoided. Straight lines may 

 be run and connected by good curves which will admit of the drain 

 being put in proper place and acomplish the work far better than can be 

 done by irregular crooked lines which usually mark the small Avater 

 courses. The disadvantages of a crooked line are that the tiles are laid 

 with greater difficulty and more imperfectly, there is a loss of grade where 

 it is needed, the friction of the running stream against the walls of 

 the drain is greater than in straight lines, and a greater length of drain 

 is required to accomplish the same purpose. 



5. Bring all land which is deficient in natural drainage under the 

 influence of drains. 



This requires the investigation of the entire watershed for the purpose 

 of determining how complete the natural drainage is. The engineer 

 should adopt in his own mind some standard of degree of thoroughness 

 with which he purposes to drain a given tract, and locate his drains 

 with reference to the natural wetness of the land. He should find out 

 whether the water comes from the surface of some adjoining higher 

 ground, or from distant springs, or is deep water from slopes. If parts of 

 the field are naturally dry, or as dry as it is proposed to make the other 

 parts, he should pass it "by and put drains in the wetter portions, so as 

 to bring them up to the standard. 



DATA REQUIRED FOR LOCATIJS-G DRAINS. 



The knowledge of a piece of land which is necessary for the proper 

 laying out of drainage system may be obtained in one of two ways, or 

 partly by both. 



1 The engineer may by carefully inspecting the land with the aid 

 of some one familiar with both surface and soil peculiarities, determine 

 upon the proper system and mark out the lines readily. There is a 

 feature connected with the location that is gratifying to the engineer, 

 which is that, when the correct and natural plan of locating has been 

 hit upon, the whole system may be developed with ease. 



