372 golze. PROBLEMS OF IRRIGATION CANALS [Ch. 21 



The machine is costly to operate, and its speed of operation for this 

 purpose is not great. Its chief advantage is in cleaning the larger 

 canals, which the more mobile blades and dredges cannot handle. 

 Tractors are sometimes used on small canals, a bulldozer blade or a 

 special blade attachment adapted to the particular type of canal 

 being used. Another type of machine in use for many years in irriga- 

 tion ditches is the so-called Ruth dredger, a system of small buckets 

 fastened to an endless belt operating at right angles to the canal; it 

 removes dirt from the canal and deposits it on the outside of the canal 

 bank, the machine moving on wheels or tracks along the canal bank. 

 Although some improvements have been made in cleaning machines 

 in past years, there still remains a challenge for the development of 

 a canal-cleaning machine that will be cheap in operation and rapid 

 in accomplishment. 



COST OF CLEANING CANALS 



The cost of removing silt from irrigation-distribution systems varies 

 with every project and with every canal and lateral within a project. 

 Seemingly identical operations vary from project to project because 

 of different machines, the skill and resourcefulness of operators, and 

 the silt conditions encountered. Each section of canal or lateral to be 

 cleaned presents its individual problem of access: right-of-way in 

 which to work; right-of-way to dispose of the excavated material; 

 type, quantity, and moisture content of the silt deposit; type and 

 density of weeds ; height of banks ; and strength and condition of lin- 

 ing — all of which affect the rate at which personnel can work and, 

 consequently, the overall cost. 



Some examples of the cost of cleaning silt are found in Table 1, 

 which shows recent costs for representative federal reclamation proj- 

 ects. Average costs of silt removal on a system basis varied from 

 $19 per mile of canal on the Yuma project, which received desilted 

 water, to $187 per mile on the North Platte project. As the total 

 mileage is used as an index and the actual mileage cleaned in any 

 one year would be somewhat less, actual costs per mile are higher. 

 The ratio of silt removal to total operation and maintenance costs 

 is shown in Table 2. These ratios varied .from 3.8 percent on the Tule 

 Lake Division of the Klamath project to 29.1 percent on the Main 

 Division of the Klamath project. 



These data again illustrate the economics of siltation of canals. 

 By careful study of cost data the prevention of silt at its source can 



