Building Ponds & Talking Liners
We all know that harvesting and storing rainwater is a huge part of designing a garden, and while swales are super functional and a fantastic way to hydrate a landscape, I—like many others—dream of an area replete with ponds. I want those permanent water features to attract wildlife, to swim in, and to use for irrigation if and when that’s necessary. Consequently, in daydreaming of some day soon owning a property, ponds have been on my mind for some time.
The dream to which I’ve held tight is that my ponds would be all natural, lined with clay rather than the more often used plastic liners. More than any concern over cost, though pond liners are notoriously expensive, I simply want to keep plastics out of my system. And, I certainly don’t want to buy into the industry if it isn’t necessary. Unfortunately, clay-lined ponds, I’ve learned, are not always to best option. Luckily, I’ve come up with some other interesting choices to ease the pain.
Pond Specifics in Theory
Firstly, we should probably establish that I’m envisioning relatively small ponds, the kind found on a less-than-a-hectare of designed property. This is an important distinction because it’s not exactly the same as creating a pond that is a hectare itself. The ponds I’m talking about are something found in Zone 1 and Zone 2 gardens and would serve to both be functional (wildlife, swimming, irrigation) but also for certain aesthetic measures.
I hope to be able to attach some to swale systems, using the overflow water to hydrate the landscape, and I envision the ponds being feed via roof runoff scenarios. I picture water catchment tanks filling and overflowing into the pond, which then overflows and fills into swales, which then overflow into more ponds and swales, perhaps some solar-powered pumps keeping the ponds oxygenated with nice waterfalls. This, of course, is all without seeing the piece of land just yet.
But, in essence, I’m hoping for one pond that, at the most, is a couple meters deep and, say four, meters across, something good for taking a dip. The rest would be significantly smaller. Obviously, I would be willing to create dams if the landscape allowed for it, but in general, my earthworks have been of the shovel and hoe variety rather than machinery, and I’d like to stay along those lines if possible.
The Clay Lined Pond
I’ve hoped my ponds could be clay-lined, but I know for smaller ponds this can create some challenges. What I’ve learned is that a clay bottom needs to be a slow slope, no steeper than a two to one ratio, which means to get down to two meters deep would take at least eight meters across (four for each sloped side). But, even if this spacing issue is acceptable (and I could live with the above dimensions), there then comes the issue of clay.
Not all soils are particularly well suited for making a pond. Something sandy or loamy will just be too permeable to work for steady water retention. So, the soil will either have to have an adequate clay content or clay shipped in, something that isn’t ideal. Without an actual site just yet from which to test the soil, I’m trying consider the fact that high quality clay might not be the variety with which I find myself.
Clay soil or no, a clay liner still has to be formed. This generally requires about thirty centimeters’ worth of compacted clay. That, of course, means digging out an extra foot’s worth of hole, everywhere. The compacting process, especially if done by hand, would require putting the liner together in layers of about 10 centimeters at a time. Suffice it to say, the clay way adds a lot of work, but that hasn’t dissuaded me. And, I’m not alone in that.
Enhanced soil liners, using bentonite clay, are another option, and for large ponds, this is known as a pretty cost effective method. However, this requires someone who really knows what they are doing and/or a chemical product known ESS13 (Environmental Soil Sealant). The beauty, though, of both enhanced soil and natural clay liners is that they last many lifetimes, and they aren’t a worry with regards to being damaged by hooves or claws or sticks or machinery.
The Plastic Liner Option
On the other hand, there are lots of plastic and rubber pond liner options on the market. RPE (reinforced polyethylene) is commonly used these days. EPDM rubber is another popular option, the upside being that it folds and fits well, the downside that it is a little more susceptible to puncturing and more expensive. Either way it goes, these liners tend to have a lifespan of about ten to twenty years, in the best of cases.
Obviously, for a very large pond, the lifespan would be a huge issue. It’s a lot of money to invest, which would push me much more in the direction of a natural clay bottom, even if the clay needed to be brought in. For the small ponds that I’m talking about, however, it’s a little more digestible to replace the liners every so often. Still, the thought of using new plastic and creating all that waste irks me, as does the idea of it breaking down slowly into the water.
Another method I’ve seen has been to use reclaimed billboard signs, which are much thinner than the aforementioned pond liners, but they are built to be durable and withstand lots of sun and weather. Plus, it’s taking something that’s trash and reusing it rather than adding it to the petroleum demand and taking precious space in the landfill. Also, ponds using plastic liners usually require a protective, soft liner beneath them, and I’ve seen reclaimed carpet used for this task. It’s an option that perhaps feels a little greener.
I realize that the billboard ponds would still add an unwanted and long-term trash element to a piece of property, much like when tires are used to build Earthships However, in the instance that a plastic liner was going to be the choice anyway, perhaps this is a more thoughtful and economic way of doing it.
Like many projects I undertake—an earthen oven, gardening without chemicals, repairing soil with yard wastes—people seem to constantly be telling me that this one won’t work. Clay-lined ponds, the nay-saying consensus seems to think, just won’t hold water. That thought feels counterintuitive to me: Ponds were around long before plastic and there is lots of evidence showing they still can happen that way. Having read and researched quite a bit now, I wonder if perhaps the plastic method is simply what is more common commercially, perhaps a bit faster and easier and, thus, more comfortable.
For my purposes, with the ponds being on the smaller side, the stakes aren’t so great as someone making one huge water feature. I’ve got time to experiment and try to make it work. I am happy to have stumbled upon the reclaimed materials method for pond building, but the ultimate plan is to give the natural clay lining a go if I can, perhaps even if importing quality clay is the only possibility. There are even shallow ponds, under two-feet deep, that in the right soil don’t require any liner at all.
Anybody out there have some good pond advice?
Feature Image: The pond looking over the veg plot (Courtesy of Irene Kightley)