Natural Pond: Loam and Clay as the Pond Bottom

Natural waters exist for years without a man-made pond bottom protecting the water from seeping into the earth. Why shouldn’t that work in your garden too? Here we explain to you how you can implement a pond without a basin and liner.

A Pond Without Liner and Basin

Most pond construction projects often involve laying a foundation of sheeting or buying a pond basin without thinking of other options. A more natural variant is also possible. However, there are some conditions here: The most successful methods are the use of earth or clay compaction. Although this procedure is more complex and expensive than conventional ponds, it offers other advantages. The variant is ideally suited for creating natural ponds, as there is no need to “hide” the film or unattractive pool edges. The most important thing, however – and this applies to the use of loam and clay – is that the final pond bottom is 100% waterproof. If there are leaks, too much water is lost and the maintenance costs keep increasing: a bottomless pit.

The Construction

Of course, as with any pond, the first thing to do is to plan: shape, depth, and material have to be determined. There are some decision-making aids when it comes to materials: Concrete or clay are very expensive, but they seal well. Clay granulate, on the other hand, is much cheaper.

The pond construction begins with the excavation of the pond. Then you have to remove sharp stones, roots, and other annoying objects. Then you can “layout” the material for the design. How this works with loam and clay will be explained in more detail later. After the material has been processed, you can then create bays on the bank. The use of pond soil or gravel, especially near the shore, can be brought in at will. Then you can plant the pond.

Create a Clay Pond

With this approach, you have to examine the soil in your own garden to determine the clay content. If the soil is only slightly clayey, you will need to use additional clay for waterproofing. A protective grille should be used at the bottom of the pond so that mice and other animals cannot undermine the soil under the pond. When digging, you have to make sure to dig an additional depth of 50 cm, because the required layer of clay should be around 50 cm thick. If you don’t pay attention to this, you suddenly don’t have an 80 cm deep pond, but only a puddle of 30 cm.

The application of the clay should be done in several layers, in between it has to be wet and tamped down again and again: During the entire process, the clay must not dry out, otherwise, it will crack easily and the end result will not be leak-proof. Depending on the pond zone, you have to apply the clay in different thicknesses. In the middle of the pond, 50 cm is ideal, but since the risk of drying out is greatest in the bank area, the layer of clay here should be 60 cm thick. You should then reduce the thickness to 30 cm up to the edge of the river. Once the clay has dried, you can add any substrate (gravel, pond soil) and plants to the pond as described above.

Clay Granules as the Pond Floor

Clay granulate is a good alternative to lining with clay: The material enables a very simple and reliable sealing, is also much cheaper, and consists of 100% natural clay. In fact, clay has a long tradition in pond construction and was used in ancient times to seal leaky cisterns. Even nowadays, bulk clay granules are often used: As soon as the swelling clay becomes wet, it combines to form a waterproof layer of clay.

The shape of the excavation of the pond must be tailored to the building material clay: Steep walls are not possible with this material. Instead, we recommend classic garden pond shapes, flat slopes with gentle curves. For fish and ornamental ponds, a clay layer of 10 cm to 15 cm is sufficient, but because of the later expansion, you should dig the pond approx. 30 cm deeper than the finished target depth. Before you start with the clay granules, you need to compact the soil so that there is a solid base; only then can the appropriate layer thickness be applied.

Then you should cover the clay layer with 10 cm of sand, fine gravel, or another substrate: This protects the soil layer and clay. Now finally it’s time to say “Water march!”, But this should be done slowly so that no flushing occurs: First, just moisten the clay granulate so that the swelling clay can expand. As soon as the water hits the clay, the clay granules become saturated with water, dissolve and form a “barrier layer”. It takes about 5 hours for all of the clay to bond into one layer. Only then can the pond be finally filled.

Advantages and Disadvantages

Finally, we want to discuss the advantages and disadvantages of such a natural pond. One advantage is definitely that such a pond forms an excellent livelihood for many animal species. Due to the natural material, the ecosystem is not harmed by chemicals, not even in the long term. In addition, there is no need to hide the foil or the pool edge.

However, the disadvantages cannot be ignored either. The construction is much more expensive and time-consuming than the use of a prefabricated pool. In the case of the clay variant, the implementation also depends on the location. The most important thing, however, is that you must not allow yourself to make any mistakes, otherwise, the pond will leak. Emptying a filled pond again and then laboriously looking for the leak is not an issue for a cozy Saturday afternoon.

Mary Allen

Written by Mary Allen

Hello, I'm Mary! I've cared for many pet species including dogs, cats, guinea pigs, fish, and bearded dragons. I also have ten pets of my own currently. I've written many topics in this space including how-tos, informational articles, care guides, breed guides, and more.

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