THE I R R I G A T I X AGE. 



211 



branch lines, as 

 shown in the figure 

 on preceding page. 



The amount 

 of rainfall in Ohio 

 is sufficient to cover 

 the entire state to a 

 depth of over three 

 feet, if none of it 

 were allowed to run 

 off or sink into the 

 soil. On level lands 

 a large amount of 

 this water soaks 

 into the soil and 

 raises the level of 

 standing water 

 found at some 

 deoth in all soils. 



For Low Basins That Are Flooded from TT T j 



Higher Lands the Remedy Is Simple. Unless drainage IS 



provided, it is only 



a question of time until the standing water will rise 

 to the surface after a heavy rain and injure the roots 

 of growing crops. This rise of water may ~be pre- 

 vented by placing lines of tile some distance below 

 the surface, sloping them gradually to a common outlet. 



There is a mistaken idea that when rain falls upon 

 land that is tiled, the water will percolate through 

 the soil until it reaches the tile and then enter the 

 drain from the top and run away. After a heavy rain, 

 the water settles almost straight down into the soil 

 until it reaches the standing water, which may be many 

 feet below the surface. As the rain continues to fall, 

 the water level in the soil rises as it would in a basin 

 into which water is being poured: finally 

 level will approach the surface, and, if 

 nothing prevents, will continue to rise until 

 the surface is reached. But if the ground 

 is provided with tile at a depth of about 

 three feet, the water level will not be able 

 to rise above this point; the water will 

 enter the joints from below and run away, 

 if the tile are of adequate size ana provided 

 with a free outlet. 



This action of tile drains is well shown 

 by means of an apparatus consisting of 

 a tank filled with soil, in which the tile 

 is represented by two small slitted tubes 

 placed at different levels. When water is 

 poured on the surface of the soil, it passes 

 down to the bottom of the tank without 

 starting the tiles, but, if we continue, the 

 water level will rise until it reaches the 

 level of the lower tile through which the 

 surplus water will escape. In the mean- 

 time the water has been percolating down 

 though the soil surrounding the upper tile 

 without causing it to flow. 



The first step in the construction of a drainage sys- 

 tem is the location of the outlet, which must of neces- 

 sity be lower than the land to be drained. Where the 

 land is slightly rolling this is a comparatively easy 

 matter, since the general direction of the slope of the 

 field is apparent and streams or open ditches are not 

 difficult to reach. 



the water 



field and follow the general slope as far as possible, so 

 that the laterals or side drains may slope toward the 

 main tile. The location of the laterals will be determined 

 by the contour of the field. As a general thing, they 

 will be spaced at irregular intervals and with the main 

 will form an unsymmetrical branched system, as shown 

 in the figure on Page 9. 



If the surface is comparatively level, the drainage sys- 

 tem should be laid out on symmetrical plans. These plans 

 require an open ditch or a main line of tile across the 

 lowest side of the field at right angles to the general slope 

 of the surface. The laterals are placed at regular intervals 

 parallel to each other, and at right angles to the main 

 ditch, if the long side of the field borders on the ditch. 

 If the field is long and narrow, with the short side border- 

 ing the ditch, it will be best to provide one long main at 

 right angles to the ditch, with short laterals branching off 

 at regular intervals. 



After the most desirable system has been determined, 

 the laterals and mains should be located by guide stakes 

 placed at intervals of 100 feet along the proposed line of 

 tile. If the surface of the land has a decided slope, the 

 ditch may be dug and graded without the use of a level. 

 The digging should begin at the outlet and proceed up the 

 line. If water is available, a uniform fall may be secured 

 by carefully cleaning out the bottom of the ditch until the 

 flow of water toward the outlet is uniform at all points. 

 Where a fall of two inches per hundred feet is desired, it 

 may be obtained by placing a dam two inches high across 

 the bottom of the ditch at a point where the desired grade 

 has been reached and cutting out the bottom of the ditch 

 above until the water backs up to a point just one hun- 

 dred feet above the dam. 



Drains which have a fall of two to four inches per 

 hundred feet will prove entirely satisfactory, if the work 



A Shows Improper Grading and Laying of Tile. 

 Grading and Laying of Tile. 



The drainage of many large areas of flat land, how- 

 ever, involves the construction of large county ditches to 

 furnish outlets for the tile and open-surface ditches. 



After the outlet is located, the next step is the loca- 

 tion of the main line of tile. If the land is slightly roll- 

 ing the main drain should occupy the lowest part of the 



Drainage Apparatus Used to Show the Action of Tile in a Drained Soil. The Drawing 

 at the Right Shows the Apparatus in Use. The Height of the Water Table Is Indi- 

 cated by the Level of the Liquid in the Glass Tube. The Figure to the Left Is 

 a Cross-Section Showing the Slitted Tubes in Place. 



is carefully done. Where it is possible, the grade should 

 not be less than two inches per hundred feet. 



Great care should be exercised to have the bottom 

 of the tile on a smooth, uniform grade. If the tile are 

 out of line, silt will collect at the low points and clog 

 the drain. The grade of the main drain should increase 

 toward the outlet, since this will increase its carrying 

 capacity and stimulate a more liberal flow from the 

 laterals. 



Wherever a lateral joins the main drain or where 

 two drains unite, the junction should be made at an acute 

 angle, in order to better direct the water toward the 

 outlet. If possible, the lateral should have an increased 

 grade for a few feet back, to give additional velocity to 

 the discharge. The correct method is shown in the 

 figure above.. 



A long drain will carry less water than a shorter 

 drain of the same diameter, because of the additional 

 friction encountered. The carrying capacity of the drain 

 is also dependent upon the grade or fall, hence the 

 steeper the grade the smaller the tile that may be used. 

 If we increase the grade from two inches to four inches 

 per hundred feet, we increase the capacity of the drain 

 one-third. 



With a reasonable grade, a three-inch tile will drain 



B Shows Proper 



