74 



Table Giving the Mean Velocity and Discharge of Ditches With Different Grade*. 



Farm Ditch No. 1. 



Ditches of the above forms can be made by first plowing four furrows 

 and then removing the loose earth either with shovels or a narrow scraper, 

 or the loose soil may be thrown up on the sides by using a V scraper or 

 crowder as illustrated below (Fig. 57, 58). 



To turn the water into the furrows the water is checked and the water 

 surface raised by placing in the ditch dams of canvas or metal tappoons, 

 or by making dams of earth or manure. When the ditch is permanent a 

 wooden or concrete check gate can be placed in the canal. The greatest 

 difficulty in Irrigating from an earthen head ditch is the care necessary 

 to give a satisfactory division of the water in the furrows. A skilled irri- 

 gator may adjust the size and depth of openings made in the ditch bank so 

 as to secure a fairly uniform flow in the furrows, but it requires attention 

 to prevent the washing of the soil at some of the openings which will 

 cause greater discharges through these openings and lower the water level 

 in the ditch so that other furrows receive little or no water. To prevent 



