Geosynthetics for Canal Lining

Geosynthetics are synthetic materials used across many sectors, including agriculture, where their main uses are irrigation and drainage. Ocean Geosynthetics manufactures a full line of geosynthetic products. This post covers how geosynthetics are used for canal lining.

What are canals?

Canals are artificial channels built for navigation, irrigation and transport. In agriculture they carry water from a source to the fields. Growing cities, industry and farm output all increase the pressure to store and move water with less loss, and where rivers and rainfall cannot supply enough water for irrigation, canals are the standard way to bring it in. In India, canals are the largest source of irrigation after wells and tube wells.

Canal Lining

An unlined canal loses much of its water through the bed and banks before it reaches the fields. Lining the canal with a low-permeability layer cuts that seepage. Traditional linings are compacted earth or soil-cement; hard-surface linings are brick, boulder masonry or concrete; and buried membrane linings use a plastic film under a protective cover. Earth linings are cheap, but they still seep and suffer erosion and weed growth. Concrete is expensive and cracks, and water escapes through the cracks and joints.

Geosynthetics for Canal Lining

Geosynthetics are now a standard alternative to these materials in many civil engineering fields, irrigation included. Used alone or with other layers, they cut seepage and make canals deliver more of the water they carry, at a cost that compares well with conventional linings.

The geosynthetics used in canal lining include geotextiles, geomembranes, geogrids and geonets. Depending on where they sit in the lining, they provide filtration, drainage or an impermeable barrier.

Geomembranes are the impermeable sheets. Geonets are HDPE drainage nets that relieve water pressure behind the lining. Geotextiles go under (and sometimes over) the geomembrane as a cushion that protects it from puncture. Geogrids support the lining system where the subgrade is weak.

Geomembranes have been used to line canals since the 1950s and do most of the work in a geosynthetic lining. HDPE geomembranes are the most widely used, because they resist chemicals and abrasion and are cheap per square metre. In canals the geomembrane is usually covered with concrete, soil or stone to protect it from UV, mechanical damage and theft; in India, IS 9698 covers the lining of canals and reservoirs with low-density polyethylene film.

LLDPE geomembranes are more flexible than HDPE and suit canals where the ground may settle unevenly. EPDM is very flexible and stable, follows the canal profile easily, and so suits relining of old canals. PVC geomembranes are also flexible and quick to install.

Ocean Geosynthetics’ high-density polyethylene geomembranes combine mechanical strength, chemical stability, very low permeability, and resistance to ageing and puncture, at a low cost. For an example of Ocean geotextile used on a canal project, see the canal lining case study.

Ocean Geosynthetics has supplied geomembranes for engineering projects for more than two decades. Contact us to plan your next project.