Ch. 21] RESEARCH NEEDED 377 



ing the silt burden from one irrigation system to another, as the sluic- 

 ing of the silt back into the river merely permits the river to carry the 

 same load to the areas farther downstream. A method is needed for 

 deposition or treatment of silt so that it will no longer be available 

 for water transportation. Refinement in design of mechanical desilting 

 basins to reduce both the initial cost and the cost of operation and 

 maintenance to the lowest possible extent is important. As with the 

 gravity basins, the problem of disposal of the accumulated silt is one 

 for further study. Merely sluicing it back into the river from whence 

 it came is no solution, even though there may be no additional irriga- 

 tion downstream. Silt bars in the river greatly affect its regimen and 

 can cause unexpected and expensive difficulties with water tables and 

 drainage of adjacent agricultural lands, even though the irrigation 

 water has been clarified to a reasonable degree. Too often the engineer 

 of today passes this problem on to the engineer of tomorrow, and to- 

 morrow always comes. 



Development of low-cost canal linings is an active possibility. The 

 Bureau of Reclamation presently has a program for that purpose and 

 has made some progress in exploring its potentialities. There still re- 

 mains, however, opportunity for considerable original research with as 

 yet unknown materials that may be adapted to canal linings. Such 

 materials might include those of plastic origin; sheet metals, such as 

 aluminum; and chemicals, such as asphalt and bentonite, which, when 

 mixed with earth, develop an impervious seal. 



Improvement of canal-cleaning machines is a fertile field. Whereas 

 improved designs have been made in nearly all forms of agricultural 

 machinery and in construction of irrigation systems, there has been 

 little improvement in machines used for cleaning canals. The inven- 

 tion and manufacture of a rapid, efficient, and cheap cleaning machine 

 would bring considerable fame and fortune to its developers, inasmuch 

 as there are in the West approximately 128,000 miles of irrigation 

 canals and laterals on both federal and private projects which are 

 still growing and which must be periodically restored in order to main- 

 tain irrigation service to the 21,000,000 acres now being cultivated. 



Aside from the actual work of making surveys, conducting engineer- 

 ing research, and improving maintenance procedures, there is another 

 task that should be performed in the interest of increasing the avail- 

 able knowledge of sedimentation of canals. The engineering literature 

 is replete with reports, articles, and books on sedimentation and erosion, 

 some of which are listed in the attached bibliography. The files of gov- 

 ernment agencies such as the Bureau of Reclamation and the Soil 

 Conservation Service contain much unpublished material on the sub- 



