IRRIGATION AND DRAINAGE 



39 



Fig. 6i. Section of wooden head flume, showing opening 

 and gate 



In making use of tubes of various kinds to distribute water to 

 furrows, it is necessary to maintain a constant head in the supply 

 ditch. This is done by inserting checks at regular intervals, which 

 vary with the grade of the ditch, but the average spacing is about 



1 50 feet. In tem- 

 porary ditches the 

 canvas dam is 

 perhaps the best 

 check, but in per- 

 manent ditches it 

 pays to use wood 

 or concrete. An 

 effective wooden 

 check is shown 

 in Fig. 60. In 

 this the opening 



is controlled by a flashboard, which may be adjusted to hold the 

 water at any desired height and at the same time permit the surplus 

 to flow over the top to feed the next lower set of furrows. 



Head flumes. Formerly head flumes for orchards were built 

 of wood, but the steady increase in the price of lumber and the 

 decrease in the price of Portland cement have induced many fruit- 

 growers to use the latter. When built of wood, the length of the 

 sections varies from 

 12 to 20 feet, 16 

 feet being the aver- 

 age. The bottom 

 width runs from 6 

 to 12 inches, while 

 the depth is usually 

 between 1 inch and 

 2 inches less. Red- 

 wood lumber I \ Fig. 62. The use of a low check in a head flume 

 inches thick is per- 

 haps the best for the bottom and sides, and joists of 2 x 4 inch 

 pine or fir are commonly used for yokes, which are spaced with 

 4-foot centers. Midway between the yokes, auger holes are bored, 

 and the flow through these openings is controlled in the manner 



