Improved Water Delivery through Modern Canal Materials
* Can canal linings significantly reduce seepage as well as concentrations of salt and selenium in irrigation return flows (drain water)?
Conventional lining techniques are relatively expensive and cost prohibitive for small irrigation districts. Reclamation needs lower cost canal lining alternatives that can reduce seepage in a cost-effective manner.
Need and Benefit
Reclamation has over 1,600 miles of main canals, and 37,500 miles of water delivery laterals. Most of these canals and laterals are unlined and lose up to half of their irrigation water to seepage. Much of this seepage is lost to beneficial use. These water losses are especially critical during periods of drought when water is scarcest. Canal lining can reduce seepage by up to 95 percent. Canal lining can also significantly reduce salinity and selenium concentrations in irrigation return water (drain water).
Construction costs for traditional canal linings (concrete with sealed joints, buried geomembranes, compacted clay) range from $5 to $10 per square foot. Previous Science and Technology (S&T) research has developed canal lining alternatives that cost only $1 to $3 per square foot, with benefit-cost ratios of 3 to 5 (Reclamation 2002). New technologies promise to reduce costs significantly further.
Polyacrylamide (PAM) is a new canal-lining technology that promises to seal canals for as little at $0.004 per square foot. PAM is a polymeric powder that acts as a soil floculent to form a soil-polymer seal on the canal perimeter. PAM is typically reapplied annually as a slurry in the spring just before the canal is filled with water. Preliminary results indicate that PAM can reduce short-term seepage by 25 to 75 percent. This S&T research project will investigate improved application techniques and equipment, re-application requirements, short-term and long-term effectiveness, and total costs to determine benefit-cost ratios for comparison with other canal-lining techniques.
A minimum of three test sections will be constructed at different locations in the Western United States. Reclamation and private sector partners will help construct and evaluate these test sections in Denver, Colorado (Denver Water Board); Montrose, Colorado (Uncompaghre Valley Water Users Association [UVWUA]); Grand Junction, Colorado (Reclamation Western Colorado Area Office); and North Dakota (Reclamation's Dakota Area Office). A typical test section will consist of three adjacent 1-mile (approximate) sections of canal with flow measurement structures between each section. The first section will be the control and will receive no treatment. The second section will receive a single application of PAM. The third section will receive annual PAM re-applications for three years. Inflow-outflow measurements will be used to determine the seepage rates through each section of canal. Required PAM application rates will be determined by a simple soil test that has already been developed.
Additonal test sections (such as bottom-only geomembrane and bottom-only concrete) are also planned for the Highline Canal at the Denver Water location. The Highline Canal is located in a park-like setting, and any canal-lining must reduce seepage, while maintaining the canal's natural appearance.
Reclamation, 2002. Research Report R-02-03 "Canal-Lining Demonstration Project, Year 10 Final Report" < http://www.usbr.gov/pn/programs/wat/pdf/finalcanal/front.pdf>.