64 MISC. PUBLICATION 43 4, U. S. DEPARTMENT OF AGRICULTURE 



The problem of carrying irrigation ditches over depressions or 

 ravines may be solved by making a fill across the depression with a 

 slip scraper and running the ditch across the fill — fill and ditch banks 

 being well compacted to avoid serious breaks. Often, however, a 

 simple flume is more desirable, especially where the ravine to be crossed 

 must be left clear to carry away floodwater (fig. 14). In some situa- 

 tions it may be most 

 economical in the long 

 run to use galvanized 

 iron flumes through- 

 out and have these 

 supported on concrete 

 or pressure-treated, 

 creosoted piers. 



It is usually neces- 

 sary to dam a main 

 ditch or lateral to 

 divert water to rows. 

 Canvas dams, port- 

 able metal checks, or 

 sandbags may be used. 

 It is considered poor 

 practice, however, to 

 cut the main ditch 

 bank every few feet 

 to obtain water for 

 individual rows. Wa- 

 ter can be diverted 

 from the main ditch 

 through a box made 

 of 1- by 6-inch or 

 1- by 8-inch material 

 (see fig. 15). Damp 

 earth must be tamped 

 around the box when it is set in place or a leak will occur, resulting in 

 a break. Water so diverted should be carried in a lister- or plow- 

 furrow parallel and adjacent to the main or lateral ditch (fig. 15). 

 From this furrow, diversion can often be made to 1 5 or 20 rows at one 

 time. It is relatively easy to cut the banks of the Jister ditch or to 

 dam it at intervals with a shovelful or two of soil. 



Canvas dams are easily and cheaply made and are effective in 

 ditches of small size (fig. 16). The 14-ounce canvas is securely 

 fastened to a piece of 2 by 4 laid across the ditch so that the loose end 

 of the canvas is upstream, where it is held in place on each bank by 

 several shovels of earth. After the water is turned in, a few extra 

 shovels of dirt may be necessary to stop leaks. Several dams should 

 be made so that one may always be in place before removing one where 

 irrigation has been completed. 



The portable metal dam (fig. 17), which is set securely across the 

 ditch by means of the 4%-foot angle iron, has some advantages over 

 the canvas dam in that it is more durable and has a greater diversity of 

 uses. The shut-off slide facilitates letting some water pass the 

 dam when desired. The dam with the slide open can also be set in a 

 ditch bank and used in place of the 6- by 6-inch box shown in figure 16. 





Figure 14. — Detail of a flume design commonly 

 used for farm ditches. The posts are spaced 8 

 feet apart along the length of the flume. The 

 prepared roofing is laid lengthwise and whatever 

 joints are necessary are made by sealing the edges 

 with roofing cement. The edges at a and b are 

 securely held with roofing nails. 



