Field evaluation of a polymer sealant for canal seepage reduction

Abstract

A large amount of the water diverted for irrigated agriculture seeps from earthen canals during its conveyance to fields. Besides a shortfall in water availability, a variety of environmental and economic damages are caused by canal seepage. Polymer sealants provide an economical alternative to permanent liners for reducing seepage from earthen canals temporarily. Field studies of the polymer sealant linear anionic polyacrylamide (LAPAM) conducted on two canals in Colorado, USA, and on a canal in Sindh, Pakistan, reveal the potential usefulness of LAPAM to substantially lower seepage losses. LAPAM application rates for the three experiments on the canals in Colorado were 14.2, 18.3, and 12.1 kg per ha of canal wetted perimeter area, and was 12.4 kg/ha for the canal in Pakistan. Flowing water balance tests show a decline of 69–100% in seepage rates for a period of up to three months after LAPAM application. Uncertainty analysis of the pre- and post-application tests on the Colorado canals indicates an 85% likelihood that seepage reduction of some magnitude occurred. Guidelines are presented for conducting further studies of LAPAM and other polymer sealants to systematically determine the impact of several factors that influence seepage control effectiveness.