Conveyance losses in irrigation canals commonly range from 20 to 40 per cent: however, the high costs of construction of conventional canal linings, such as those of concrete, asphalt, and plastic, often prevent large-scale efforts to control seepage. Thus, the idea of lowering costs by utilizing flowing canal water for placement of sealing clays in the leaky zones of canals is an attractive one. This paper traces the development of water-borne clay sealants for canals, from natural silting to the recently developed methods of sediment-sealing with bentonite.

In general, the water-borne clays are best for sealing coarsely rocky to gravelly canal bed materials. Less favorable results are obtained when clays are used for sealing fine-grained silty to sandy canal materials. Lack of penetration and short life are the main problems with clays used for sealing fine-grained soils.

The cost of clay-sealing ranges from less than $.01/square yard of canal area to an extreme value of about $2.00/square yard. Concrete linings, which are usually considered the best answer to most seepage loss problems, seldom cost less than $2.00 per square yard.