Abstract
This study was conducted to determine the effectiveness of lining tertiary canals with respect to their lining age. Twenty partially lined canals (1–25 years of lining age) were randomly selected and these were classified into five age groups with a class interval of 5 years. The flow rate of each selected channel was measured at the head and tail of the lined sections, and in the unlined sections at a distance equal to the length of the lined sections. The conveyance losses varied from 0.76 to 1.31 l s ‐1 per 100 m length. The lowest losses were observed in the newly lined canals (1– 5 years old) while the highest losses were observed in the case of group IV, having a lining age of between 16 and 20 years. The conveyance losses were reduced by 47 and 30% respectively in groups I and V. Thus, these results clearly demonstrate that the effectiveness of lining decreases with its age. A significant amount of water is saved by the newly lined canals; however, this benefit decreases as the lining become older. Copyright © 2013 John Wiley & Sons, Ltd.