Even after careful selection and installation, a canal liner made from any material can eventually become damaged and begin to leak. Concrete, geomembranes, and mortar-based systems are tougher than other materials, but they can still become damaged by specific hazards. Understanding what’s potentially threatening the integrity of your liner will help you address risk factors during installation for a longer lasting liner that requires fewer repairs over its lifespan.
Cracking
Stiffer and less flexible geomembranes can crack after becoming brittle due to freezing, while concrete cracks if the soil below shifts or rises up. The smallest hairline cracks can be impossible to see while still leaking out a surprising amount of water. Flexible and resilient geomembranes are less likely to crack, even when frozen solid or after dozens of freeze and thaw cycles. Pairing a geomembrane with a concrete liner also reduces its chances of cracking. Any material that can flex and bend under pressure rather than just splitting is a better choice for a canal full of water where swelling and soil expansion is inevitable.
UV Damage
Leaving geomembranes exposed to the sun that are designed for covered or buried installation will lead to rapid breakdown of the material. Some PVC and other materials can break down within just a few years if left completely uncovered. Water doesn’t count as a cover, even if it’s so turbid that it’s impossible to see through. In fact, water can amplify the effects of sunlight by acting like a lens in certain situations. Ballast or covering geomembrane with a layer of concrete are two of the most common ways to protect the material from UV-induced breakdown. More simply, choose a high-quality liner that boasts high UV resistance. Liners that degrade from UV exposure can develop thousands of tiny holes or cracks at stress points, making it frustrating to track down leaks and seal them. Protecting them from UV damage, or using a UV-resistant material, prevents this problem from day one.
Installation Mistakes
Handling materials too roughly, applying concrete or mortar in too thin of a layer, forgetting to cut control seams, missing seams while sealing geomembranes, and letting water flow too soon through a new canal can all lead to serious damage. RPE membranes won’t tear easily when dragged over rough ground or uneven concrete surfaces, but other geomembranes often snag and rip. Storing materials in too hot or cold of an environment before installation can also affect how smoothly installation goes and whether damage occurs. Knowing how to properly install the liner you choose is essential to prevent damage.
Freeze and Thaw Cycles
Freezing and thawing repeatedly each winter does more than just weaken the more brittle liner materials and lead to cracking. When any water in the soil around the canal freezes, it expands. Melting causes it to shrink again rapidly and possibly leave behind a void. This swelling and shrinking action is particularly strong in expansive clay soils, and it’s also known as frost heave. Flexible liners are obviously much less likely to become cracked or ripped by these kinds of deformations. However, large frost pockets can cause a wall section to sag or crumple in on itself if it’s bad enough. This is another reason that lined canals are better than unlined features. Because of high seepage rates, unlined canal banks in cold climates erode and collapse faster due to ice movement.
Rats and Insects
Rats and even some enterprising insects, like termites, can potentially damage liner materials. However, both geomembranes and concrete materials are too tough for them to chew and gnaw. Rats are always seeking warm and protected places to build nests for the winter, and the steady flow of pumped water in a canal often keeps it warmer than the surrounding area. This leads rats to burrow in from the soil behind a liner. Extensive infestations of rats or larger rodents like beavers can result in collapsed walls, but mostly they damage weaker liners like clay and rammed earth. Choosing a durable and rat-proof liner is a must if you live in an area with heavy field pest pressure.
Lifting from Wind or Water
When wind slips under the uncovered end of a canal liner, it can lift geomembranes up and detach them from the earth or concrete below. This often leads to water slipping into the space as well, further lifting the membrane and causing it to float. Securing the edges of the material where it reaches the top of the canal walls or banks is essential. A heavy layer of ballast like gravel or rock may be enough for many installations, but some geomembrane liners will need concrete curbs poured over the edges to secure them even if concrete is not used for the rest of the canal. Don’t underestimate the amount of force that can build up to move and tear your geomembrane liner when wind and water manage to get between it and the base.
Blockages
Blocked canals are dangerous because water builds up rapidly, crests over the banks in an overtopping event, and can flood nearby fields, homes, and businesses. Large canals carry more than enough water to cause millions of dollars-worth of damages after a blockage. Silt, trash, dead animals, and collapsed canal walls can all create blockages that dam up the entire flow. Silt tends to accumulate over time, but a mudslide or extreme rain event can cause it to build up in hours or days rather than over a period of months. Debris and collapsed walls often only take seconds to roll into place and start forcing water up and out of the containment area. Canal blockages require the disconnection and drainage of the affected branch for repairs, leaving the acreage or power plant relying on the flow without water until repairs are completed. When this occurs during a peak growth period, crops can become stunted or even dry up and die entirely. Proper design, a strong liner material, and regular inspections all help prevent these blockages from occurring.
Weed Growth
Finally, canals need occasional weeding even if they’re sealed with a material like mortar, geomembrane, or concrete. Some seeds and plant debris will root even in this thinnest layer of silt at the bottom. If these roots are left in place to grow for months, they can eventually damage even the toughest liners. Remove weeds on a regular basis or use an aquatic herbicide that is safe for your crops to keep algae, water weeds, and other plants out of your canals.
With all this information about designing and lining canals of all kinds, you should be prepared to build a better water conveyance system. Whether your canals will be powered by gravity alone or feature an intricate system of pumps and channel locks, you can rest assured that geomembrane liners will help them last. Explore the full range of BTL Liner’s geomembrane products to find the right flexible and durable liner for your canal.
