construction and refurbishment of earthen irrigation channel banks

United States references give a wide range of seepage rates for unlined channels, butcommon values vary from 0.02 to 0.3 m 3 /m 2 /day. Seepage rates from United Stateschannels before they were lined have been as high as 0.4 to 0.9 m 3 /m 2 /day. The USBureau of Reclamation refers to channel seepage losses of 0.06 m 3 /m 2 /day as beingrelatively low. By comparison, some Irrigation Authorities in Australia consider channelseepage rates of over 0.03 m 3 /m 2 /day to be high. Figures for unlined irrigation channelsin India show seepage rates generally vary from 0.025 to 0.60 m 3 /m 2 /day.22.3 Types of LiningsTo be successful, a channel lining must reduce seepage to an acceptable level atreasonable cost and maintain effectiveness for the length of time required. An idealchannel lining material should satisfy the following requirements:• cost-effective• low permeability• reasonably long service life• capable of selective application• resistance to mechanical damage, weathering and biological deterioration• flexibility over a range of temperatures• low roughness co-efficient• reasonably low capital and maintenance costs• easy to repairA wide range of channel linings have been tried in Australia and overseas with varyingdegrees of success, at widely varying costs, and each has its own specific features andpromoters. There is however, relatively little information available on the long-term costsand effectiveness of many of the channel linings under Australian conditions. Whilemany lining treatments perform well under laboratory conditions, climatic and operationalconditions can effect their performance in the field.The different types of linings are commonly classified into three groups according to thematerials and methods used in their construction. These are:1. Earth Linings• Compacted earth lining• Compaction of insitu channel material• Bentonite type lining• Compacted soil-cement lining• Modified soil lining• Soil sealants2. Flexible Membrane Linings• Exposed Lining• Covered Lining3. Hard-Surface Linings• Concrete lining• Asphalt Lining• Brick Lining• Stone LiningConstruction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 22-4