Seepage and drainage

Abstract

Canals continue to be major conveyance system for delivering water for irrigation in the alluvial plains of India. But loss of water due to seepage from unlined irrigation canals constitutes a substantial percentage of the usable water. By the time the water reaches the field, it has been estimated that the seepage losses are of the order of 45 percent of the water supplied at the head of the canal (CBIP, Technical Report No.14, 1975). According to the India Standard (IS:9452,1980) the loss of water by seepage from unlined canals in India generally varies from 0.3 to 7.0m' per second per 106 m2. The transit losses are more accentuated in alluvial canals. It has been estimated (CBIP,Report No.14, 1975) that if the seepage loss is prevented, about six million hectares of additional area could be irrigated easily. The seepage losses from a canal may lead to water logging and soil salanisation. Canals in alluvium are lined for water conservation and prevention of water logging. Depending on the lining material seepage from a lined canal occurs at a reduced rate. Various research organisations and many investigators have carried out experimental and analytical studies on seepage and drainage since independence for solving the problems due to seepage. In this chapter the contributions made by various investigator and research organisations in India in the study of seepage from canals have been focused.