35 



of the smoothness of the channel, or by increasing the cross section by ex- 

 cavation. The cost of extra excavation, especially on side hills through hard 

 material, may be greater than the cost of lining. 



Concrete lining will usually prove to be the most economical type of 

 lining to use in British Columbia. ' However, where good clay is available 

 ;and where it is not financially feasible to use concrete, clay puddle may be 

 msed to advantage in improving leaky earth canals when the velocity of flow 

 is under 3 feet per second. 



1. Concrete linings. 



The earliest use of concrete linings was in southern California about 

 1880 when the increasing value of water made it necessary to do away with 

 losses. Since that time practically all of their canals, which are compara- 

 tively small, carrying less than 100 cubic feet per second, have been lined 

 with concrete and in some cases replaced with concrete pipes. Until re- 

 cently very little concrete lining had been done outside of that region, but 

 during the last few years concrete lined canals have been constructed on 

 many of the projects of the United States Reclamation Service and on 

 numerous private projects. There are now several examples in California, 

 Oregon, Nevada, Washington, Idaho and other states and during the past 

 two years some excellent work has been done in British Columbia. The 

 Fruitlands Irrigation and Power Company near Kamloops has lined about 

 6 miles of its main canal which averages 3y 2 feet in depth, 4 feet wide at 

 the bottom and 7 % feet wide at the top, with an average thickness of con- 

 crete of 3 inches and when the system is completed there will be about 15 

 miles of concrete lined canal. (Pigs. 24, 25). The Kelowna Irrigation 

 Company, near Kelowna, has lined the upper 5 miles of its main canal, 2*/ 2 

 feet deep, 3 feet wide at the bottom, and 5 y 2 feet wide at the top, with 3 

 inches of concrete (Pig. 26). The remaining 7 miles of the canal, which is 

 1.5 feet deep, 2 feet wide at the bottom and 4% feet wide at the top, is 

 lined with 2 inches of concrete. 



Form of cross section, and thickness of lining. 



Unlined canals in earth are usually constructed broad and shallow with 

 the side slopes varying according to the character of the soil. This may be 

 as steep as y 2 horizontal to 1 vertical for hardpan or very firm soil, or as 

 flat as 2 to 3 horizontal to 1 vertical for loose sandy soil. For a lined canal 

 it is more economical to use a comparatively narrow deep section and fairly 

 steep side slopes. This reduces the excavation and the amount of concrete. 

 The side slopes must not be much steeper than the slope on which the 

 ground will stand or the earth pressure may be sufficient to push the sides 

 in and break the lining. The side slope and the thickness of the lining are 

 dependent upon each other and they vary with the depth of the canal, the 

 character of the soil and the method of construction. Generally the flatter 

 the side slopes, the thinner can the lining be made. In southern California 

 fairly satisfactory results have been obtained on many systems with linings 

 1 inch or less in thickness. But because of extremes in temperature and 

 the low winter temperature, it is probable that such thin linings would not 

 be very satisfactory in British Columbia. There are no good examples of 

 very thin linings built where the winter temperature is low. The writer 

 has seen four miles of canal in eastern Washington lined with y 2 to 1% 

 inches of concrete. The lining was rather badly cracked, but this was 

 largely due to poor workmanship. It made it possible, however, to carry 

 water over this length of canal which was impossible before its construction. 



