78 



The flumes are constructed on the ground by using a set of forms or 

 moulds into which the concrete is placed (Fig. 64). The moulds consist of 

 an inside bottomless trough similar to the form used for lining ditches, but 

 made with the same dimensions as the inside of the flume, and outside 

 walls or sheathing held the proper distance apart from the inside form by 

 means of spacing blocks and heavy U shaped iron, straddling over the out- 

 side wall and inside wall. Instead of the U shaped iron, the outside walls 

 could be held in place by stakes driven in the ground. To build the floor 

 and sides at the same time the inside walls are held above the ground by 

 the spacing frames a height equal to the thickness of the floor. The flume 

 is built in sections 12 feet long, which is the length of the forms. No pro- 

 vision is made for contraction and small shrinkage cracks occur. These 

 could be eliminated by inserting at the edges a metal tongue 2 or 3 inches 

 wide imbedded about halfway into each section. This tongue should be 

 well painted with oil or soap to prevent the adhesion of the concrete and it 

 will then act as a tongue and groove joint. 



To permit the quick removal of the forms, which is necessary unless 

 sufficient forms are used to build a considerable length at one setting, the 

 concrete is mixed comparatively dry and requires careful tamping. A mix- 

 ture of 1 part of cement to 5 of well graded pit gravel is generally used. 

 It is important that the concrete be kept moist by sprinkling or otherwise 

 for a period of at least one week. When completed the side walls are 

 partly backfilled with earth up to about one-half of their height. It is 

 better to have the spouts at least 4 inches long and preferably six to pre- 

 vent the washing away, by the action of the water coming out of the spout, 

 of the soil from under the flume, which will cause it to settle and crack. 

 These galvanized iron spouts are made by local metal workers at a cost of 

 4 % to 5 }i cents each. 



4. Cement Pipes and Distributing Stand Pipes. (Figs. 65. 66). 



In southern California many hundreds of miles of cement pipes have 

 been used for the distribution of water to orchards and in recent years its 

 use has been extended to some of the orchards in Washington and Idaho. 

 While many orchardists in southern California still prefer the open flume, 

 there are the following objection to open flume: 



1st. Teams and farm implements can not cross the flume and there is 

 always a strip of land on each side that can only be partially cultivated 

 because it can not be crossed in the opposite direction. 



2nd. The flume is liable to be damaged by the teams and farm im- 

 plements. 



3rd. The flume may settle and crack if the earth underneath is washed 

 away by the water passing through the spouts into the furrows. 



4th. The furrows can only be made with teams and cultivators up to 

 15 feet from the flume and they must be completed by hand. 



5th. Leaves may fall in the flume and stop up either partially or com- 

 pletely the openings of the distributing spouts, which requires extra time 

 on the part of the irrigator. 



These disadvantages have led many of the orchardists to the use of 

 underground pipes which do not interfere with cultivation. 



A complete underground pipe distributing system consists of: 



1st. A main pipe line which carries the water from the measuring box 

 or point of delivery to the lines of distributing stands which take the place 

 of head ditches. 



