It’s easy to assume that excavation is the most challenging part of building a small to medium sized pond. However, a properly shaped and compacted pond will still lose water and cost too much money to keep filled unless it’s lined. This is true whether you’re using the pond to raise fish, swim, store irrigation water, or process wastewater. Unless you only plan to use the pond seasonally and for short periods of storage, you’ll need some kind of liner. There are many options, but flexible geomembrane liners remain the best choice among them.
All ponds lose some water through seepage and evaporation over time. However, unlined ponds and naturally lined water features lose far more water than those with impermeable liners at the bottom. Studies of seepage rates from unlined ponds show an average of 7.87 inches of water lost each day, depending on soil conditions. In very sandy and loose soils, ponds lost up to 70 inches of water per day. Even at an average range of 7 to 16 inches per day, that represents the loss of thousands of gallons of water per day for most ponds. Impermeable liners can stop water loss from seepage. There’s no need to sacrifice all of that valuable water to the soil when it can be controlled by a proper liner.
Seepage can also add water to a pond rather than causing a loss. Incoming seepage is particularly a problem for evaporation ponds attempting to lose water on a specific schedule. It can also cause issues in fishponds where water quality needs to stay within tight parameters. Again, impermeable flexible liner materials stop this transfer of water from the outside inward just as well as seepage out of the pond.
Mineral and Chemical Leeching
Seepage out of a particular pond can also cause far more problems than just water loss. If you’re storing wastewater or chemical mixtures in the middle of processing, you’ll need to prevent seepage to control contamination. Water that leaks out of your holding or processing ponds can damage local waterways or accumulate in underground aquifers used for private wells or public drinking supplies. Allowing contaminants to escape an irrigation runoff pond or a coal ash storage area could lead to expensive fines from the EPA and state authorities. Chemical resistant liners are essential for preventing contamination through water loss and seepage.
Ponds designed for evaporating wastewater, as a processing step, require a steady rate of water loss. Most pond liners made from geomembrane material are black, heating up the water thanks to the absorption of light. Installing the dark colored pond liner, so it’s exposed under the water, is best for encouraging rapid evaporation. Ballast materials and soil cover prevent the pond liner from contributing to the evaporation process. However, even covered liners contribute to proper evaporation processes by preventing water loss in other ways.
Unlined and naturally lined ponds require routine maintenance each year to prevent the loss of the clay liner sealing the soil surface. Properly lined ponds don’t need as much attention each year, reducing maintenance costs and the chance of expensive leaks. You’ll still need to occasionally remove sludge, but this often only happens every few years with a lined pond. It’s also much easier to run filters and skimmers in lined ponds since there’s far less sediment settling in the equipment.
If you allow seepage to continue for years, even at very low daily and annual rates, you’ll eventually hollow out areas of soil under and around the pond. These areas will lead to leaks and collapses that could suddenly drain the pond within days or even overnight. Liners protect the soil around the pond from both gradual and sudden loss of stability. If soil testing shows that there’s a high chance of collapse or shifting due to a loose texture, installing a liner is usually necessary for reinforcement. A geomembrane like BTL Liners AquaArmor is the best choice for keeping soil from moving during construction or during the years of active pond use.
The banks of a pond are most susceptible to damage and collapse due to the combination of instability from water seepage and erosion over the surface. A flexible liner material protects against both issues to keep banks intact and fully vegetated. Without a liner, soil is often lost from the banks before native grasses and plants become established. Solid liners, like geomembranes and concrete, also protect ponds as they age from holes created by tree roots or animal burrows. These penetrations can’t reach the water thanks to the impermeable barrier, preventing water loss and bank collapse. If a bank collapses while there’s equipment or people on it, injuries and property damage will occur. Even without trees around the edge, or animals like muskrats that want to burrow near water, banks will slowly erode from the constant movement of water.
It’s easiest to add a liner when first building a pond. If you’re already dealing with an existing pond that keeps leaking, AquaArmor from BTL Liners is easily installed as soon as the pond is drained and dredged. Don’t give up on an existing pond when a few improvements could restore its function within a few short weeks.