Planning a pond or lake, a useful guide

Here are some important points to consider when planning your pond or lake.

Why not build your pond away from the hanging trees? The falling leaves will break down and produce nitrates that will stimulate algae growth. Build your pond or lake in a place that is exposed to sunlight for about half the day.

Even a small pond should be at least 60cm deep at one point to prevent oxygen levels from dropping too low when the surface freezes (to protect invertebrates / amphibians). If you intend to keep fish in your pond, the deeper areas are vital to protect the fish from herons and cats.

Have at least one shallow side, some of which must be well planted, for amphibians to get out of the water. The shallow sides allow for more marginal plants, which in turn are home to more wildlife. The gently sloping sides allow the hedgehogs to escape and are less dangerous should a young child fall. Small or small children should always be supervised around water.

Before digging your pond or lake, make sure there is no sewage, water, or power cables running through your garden, check with your local utility companies or city hall. A planning permit may be required, depending on the size of the lake or pond and the area.

Be aware that tree roots near your pond or lake bed can break through the liner and cause future leaks.

Before introducing fish, be aware that fish eat invertebrates and tadpoles, and discourage damselflies and dragonflies, in general, the widest variety of natural life can be found in ponds that do not contain fish.

Do not place your pond on a swampy ground, otherwise the water will tend to rise behind the liner causing problems in the future. If you have no choice but to dig a small pond in an area with a high water table, one or more sumps can be dug around the pond with pumps inside to artificially lower the water table (although a complicated and expensive solution).

Once the lake has been excavated, it is common practice to use a layer of soft sand to smooth the surface. For the base, a geotextile membrane is best (you can cut costs with a polypropylene mat, but remove the nails / tacks first). There are many different liners that are now available, butyl is a popular choice because it is durable and long-lasting, but polyethylene is sometimes used. The liner is usually covered by softer sand and fine gravel washed away before the pond or lake is filled. Some pond and lake beds are constructed of concrete, often incorporating liners. The traditional method is to use flooded clay, however this is difficult and expensive, so it is rarely seen in new ponds and lakes. Lake construction techniques are constantly changing as technology advances, be sure to seek the advice of several different contractors in deciding the best system for your project.

Please note that this article is for advice only, always consult a trained landscape designer before attempting groundwork.