Creating a pond - pt.2

Our new pond has no natural water supply - no source or stream to feed it. We always knew we were going to have to fill it (and occasionally top it up) from the tap. It's important, then, that it holds water as well as possible.

Having dug into clay, we did momentarily entertain dreams of simply puddling the clay and allowing the pond to fill naturally.

Fat chance.

We puddled the deepest bit and turned on the hose to see how long the water would remain. Not long, was the answer. So it was off to the Interwebs to check out liners.

The standard solution these days is EPDM butyl. To fill a hole 6.5m long and 4m wide, with the required overlap at the edges, we calculated the cost from French vendors at about €550-600. But then Trish discovered the Flexiliner product from Pondkeeper.co.uk. This is thinner than standard butyl liners (read, easier to manage) but has similar UV resistance. And, even with geotextile underlay, it was about half the price. They offered very reasonable delivery rates to France, too. In three days from ordering, our new pond arrived in the post.

Before we could play with the liner, though, we had some more preparatory work to do.

The biggest danger with liners is making holes in them. And the most common culprit is a stone underneath the liner.

Water is heavy. The deepest part of our pond covers an area of, say, 4 square metres. With a depth of about a metre, that's 4 tonnes of water pressing down on the liner.

So, first you scour the floor and sides of the pond, pulling out any stones you find. We were pretty lucky in having largely stone-free soil. Then you add a layer of protection.

A common solution is to put down a layer of sand. We didn't like that idea much because of the difficulty of getting sand to the location. An alternative is to put down old carpet, or thick layers of newspaper or card. Or you can buy underlay.

We opted for a belt & braces approach. Friends gave us old sections of carpet and where that didn't cover we laid corrugated cardboard. The result was, somehow, very poor white trash. It also had the effect of making the pond look surprisingly small.

Then we laid the geotextlie. This comes in 2m wide strips and is very similar to the stuff gardeners use to supress weeds in flower beds or around new shrubs. It's soft but very tough and should help to discourage roots and moles as well as protecting from stones.

Once all the underlay was in, the pond started looking large again. The photo below shows it before we began working on the wrinkles.

Next came the liner itself. We were lucky in having enough space to fully unfold it and lay it flat before moving it into position. We then eased it down into the hole, gently prodding it into the curves of the pond with a broom. Once it was in place and the worst of the wrinkles removed, we added back about 5cm of topsoil (checking carefully for stones). Then we started to fill the deep section with water so that the weight of it would pull the liner into position.

Once the water neared the top of the deep section, we turned our attention to the shallower areas. One end of the pond has a relatively large shallow area and we thought that this is where Zola, our spaniel, is most likely to jump in. So we covered the liner with more geotextile and a couple of old doormats. Then we covered most of the shallow sections with soil.

As the water level rose, we made a sudden, last-minute decision to extend the pond, but more of that in the next part...