Pond Linings: How to choose a pond liner?

Ponds are an important feature for maintaining and increasing the biodiversity of an area, as they allow a habitat for the local wildlife. Threats to natural ponds such as pollution and a changing climate are meaning garden ponds are becoming even more important. Its estimated that the nations gardeners have added an additional 2-3 million ponds (1) which act as fantastic garden features whilst supporting biodiversity. However, there are multiple ways to create a garden pond, each using a different material, some of these are better for the environment than others.

Puddled Clay

This is clay which has had the air pushed out of it by repeated trampling until there are no more air pockets creating a dense watertight layer. Ponds lined with clay need to be on stable land as subsidence or slipping can cause cracks, so this method isn’t recommended on sloped land or an area that has recently been disturbed (2).

Pros:

  • Is a natural substrate so provides a habitat for bacteria, microorganisms etc, to flourish, generating benefits for fish and wildlife from the minerals in the clay (3).
  • Materials can be low cost if sourced locally (2).
  • Is a traditional way of lining ponds and larger waterways.

Cons:

  • Liable to cracking in dry conditions and if the pond isn’t filled to capacity (1).
  • Clay is a thicker liner than sheeting so would need a larger pond constructed.
  • Technical and expensive method as transportation costs of puddling clay can be high as several hundreds of kilos may be needed (2).

Flexible Liners

Rubber a widely used material for pond lining with butyl and EPDM being the most commonly used. They have a lifespan of around 25-50 years  and are non-toxic to nature, so are a good long-term option (4). However, these types of pond liners are petrochemicals meaning they have been manufactured from crude oil or natural gas (9). The awful effects on the environment from the extraction and manufacturing of crude oil is already well known, meaning rubber pond liners can never be truly sustainable due to their production.

 Flexible plastics can also be used for the construction of a pond, PVC and reinforced polyethylene being examples. Stronger, more rigid pre-formed linings can also be made from plastics, which tend to be easy to maintain and some can even encourage healthy bacteria growth (3). However, the production of rubber both synthetic and natural can cause severe environmental hazards like air, noise and water pollution and raises health concerns (5).

Pros:

  • Low-cost accessible option that is easy to install.
  • Flexible so can be used on any size, shape and depth of pond
  • Rubber linings can be very durable and can withstand freezing temperatures so have a long-life span (3).
  • Can be easily repaired through patches if ripped or pierced, the area should be cleared of any debris or rocks to limited the chance of damage to the liner (2,4).

Cons:

  • Not manufactured sustainably on a large scale synthetic or natural, creating environmental and health hazards (5).
  • Advisable to use an underlay to act as protection, such as pond underfelt and or sand which can raise the costs of construction (1,4).
  • Plastics can take 20- 500 years to decompose(6) and are mostly made from crude oil (7). which perpetuates the need for oil and its un-sustainability. 

 

Concrete

This material is the most durable when it comes to ponds and is suited for formal ponds. The construction process is technically and often needing the help of professionals which can cause it to be expensive and time consuming (4).

Pros:

  • Very robust and can withstand trampling.

Cons:

  • Concrete production itself is very polluting and contributes massively to CO2 emissions and climate change. Along with using sand in its creation, which is a rapidly depleting resource.
  • Has to be treated or allowed to season before any fish or plants are introduced into the pond, making it harder to establish a habitat (4).
  • Prone to cracks and leaks which are difficult and expensive to fix (1).

Fibreglass (pre-formed lining)

This material is usually added over the top of preformed bases that are made from plastic for example. This increases the durability and its pre-made structure eliminates the possibility of folding and creases (3) and is hard to penetrate.

Pros:

  • Liners are light weight and resistant to puncturing or ripping

Cons:

  • Fiberglass can’t be Widley recycled and only starts to deteriorate after 50 years resulting in it staying in landfills for potentially hundreds of years (8).
  • Makes a more artificial pond, which has a lower chance of attracting wildlife, by covering the base in natural materials like gravel and sand can encourage plants and wildlife (2).
  • Expensive material along with it often needing to be professionally fitted (3).

Pond Lining Recommendations

Each material for a pond has different benefits and costs, however, Puddled Clay is one of the best recommended options due to its environmentally friendliness and potential low cost if sourced locally. Also, Rubber is a good alternative option if clay can’t be used as it has a long-life span and is highly durable, although production process is highly unsustainable. Therefore, the best pond lining largely depends on the needs and budget of the project.

Sources:

  1. https://content.freshwaterhabitats.org.uk/2013/09/Creating-Garden-Ponds-for-Wildlife.pdf
  2. https://www.lowimpact.org/categories/ponds
  3. https://plantcaretoday.com/pond-liner.html
  4. https://www.rhs.org.uk/ponds/construction-and-repair
  5. https://neptjournal.com/upload-images/NL-57-29-(27)D-429.pdf
  6. https://www.un.org/en/exhibits/exhibit/in-images-plastic-forever
  7. https://www.bpf.co.uk/plastipedia/how-is-plastic-made.aspx
  8. https://theroundup.org/is-fiberglass-biodegradable-or-can-it-be-recycled/
  9. https://www.britannica.com/science/petrochemical