- Cracks can form due to freezing and thaw cycles during winter months, or sun exposure, if the lining method isn't UV-durable. Even hairline cracks can release large amounts of water. No matter how slight, movement within the earth can also present opportunities for cracks to form in stiffer material like concrete.
- UV radiation, that can reach a liner that isn't resistant to sun damage, will quickly enable the material to degrade. Water isn't a proper cover, as the prism effect of water can amplify the rays of the sun reaching the bottom of the canal. If your liner isn't UV-resistant, a covering such as an earth-based ballast or concrete can help.
- Any mistakes during installation can lead to long-term damage and complex obstacles. This can appear in the form of concrete or mortar applied too thinly or any liner that isn't sealed correctly. RPE is less likely to rip and tear than other geomembranes, which can be vulnerable during the installation process. Storage of your liner in unacceptable conditions (like too hot, too wet, or too cold) can damage or weaken the material, making complications more likely during installation.
- Freezing and thawing cycles can lead to more than just cracks and brittleness. As the water in the soil freezes and melts, it takes up more space and then quickly shrinks back to its original form, leaving voids in the surrounding earth. A flexible liner will be more likely to handle sudden changes in its foundation and less likely to collapse as a clay-based canal would.
- Animal interference can come in the way of curious, chew-happy rodents or particularly ambitious insects. While concrete and geomembrane liners are more resistant to animal damage than other forms of liners, rats and mammals attracted by the warmth emitted by moving water will be tempted to build nests in the ground near an irrigation system. The disturbance of nearby dirt can lead to walls collapsing or sinking ground levels.
- Any space between the ground and liner can allow air or water to become trapped beneath the material, causing the liner to float. This is avoided by securing liner edges or protecting the material with a ballast. Other geomembranes will require concrete curbs to secure the liner panels.
- Blockages within the canal can cause water to build up and even overflow within the system. This can result in significant flood damage. Silt, pollution, animal waste, or collapsed walls can all create a virtual dam within a canal. A severe blockage will require drainage and repairs before the problem is allowed to build in severity. Regular inspections, especially after weather patterns that could pick up excess silt, significantly prevent these blockages.
- Weeds can grow within a canal even if the surface is sealed with a liner due to thin layers of built-up silt. The roots growing from these plants can cause serious damage to a canal liner. Consistent weed removal or aquatic herbicide may help alleviate this risk.
Most of the time, there's water left at the end of flood irrigation; this runoff is referred to as 'tailwater.' Because tailwater from fields often contains toxins found within pesticides and fertilizers, it's essential it’s not allowed to seep back into the groundwater, or flow into nearby waterways. In places where the salt content of the water is very high, flood irrigation may also be destructive to the soil if salt is allowed to build up. Innovative farmers over time have tried multiple ways to make this kind of furrow or flood irrigation more efficient.
Improving on Flood Irrigation:
- Flood irrigation's primary source of power is gravity, and any slight incline on which crops are planted can allow water to drain past before the roots are fully saturated. Farmers often flatten their fields before planting, allowing flowing water more time to absorb into the earth evenly.
- Collaboration between agricultural experts and soil scientists has provided an incredibly detailed analysis of soil types and their rate/method of infiltration. Sandy soil that pulls water downwards should be irrigated more often and for shorter periods, preventing water from seeping beneath the roots. For loamy or clay soils, longer periods of watering with more time in between will allow the water to thoroughly saturate the soil, decreasing the chance of water waste through runoff.
- Other farmers use a technique called "surge" or "pulse" irrigation. Rather than just releasing water into the field, surge flooding releases water at regular intervals or pulses. This allows standing water a chance to seep into the soil, reducing the chances of runoff and thirsty plants.
If the runoff is unavoidable, some farmers collect the tailwater to reuse it again. Runoff ponds or containers can catch tailwater and pump it back into the irrigation system to be used in the fields again. If this water contains too much salt to be reused, blending with lower-salinity water may solve this problem. Although this adds some cost, this may still be an economical solution for farmers facing severe water depletion. Soil salinity is a persistent issue for farmers worldwide, and breakthroughs in technology are still emerging today.
