Ponds - introduction

“All of a sudden I had the revelation of how enchanting my pond was.” – Claude Monet

What are ponds?

Ponds are shallow, water-filled depressions colonised by aquatic plants and animals. They are an important natural resource and provide habitat for native British species like frogs, toads and newts. Natural ponds, created by receding flood waters or forming in the depression left by the roots of fallen trees, may occasionally still be seen in the countryside. These days though, these are incredibly rare, as the natural processes that form them are much more managed. For many centuries, ponds on farm or common land served as an important water source for livestock. However, intensification of agriculture and modernised farming methods (like using pipes to transport water to animal troughs), as well as changes in land use, increased urbanisation and construction have led to a large number of ponds being lost since Victorian times, with serious consequences for the species that depend on them.

Ornamental or garden ponds are a more recent development (although evidence has been found of their existence in Roman ruins). Monasteries traditionally had fish ponds, and most large country estates had a water feature, but smaller garden ponds only really became popular in the second half of the 20th century when gardens got larger and ordinary people had more expendable income and free time. The development of modern materials like concrete or rubber pond liners also made them much easier and cheaper to install and maintain.

Today, thanks to campaigns like the Million Ponds Project or Just Add Water, the number of ponds is on the increase again. However, it’s estimated that some 90% are polluted to some degree, mainly by nutrients and sediment run-off in urban areas or near roads. This is a bad news for aquatic plants and wildlife that evolved to live with lower levels of nutrients, since the high levels of nitrates and phosphates found in gardening products can alter the delicate balance of the water.

What are the benefits of ponds?

For their relatively small size, garden ponds provide a large benefit to local wildlife. They are great for biodiversity, and creating more of them increases the available habitat for a number of species that have declined in recent years due to habitat loss or imported diseases such as Ranavirus (which affects amphibians).

Animals like frogs, toads and newts all use ponds for breeding, and when several ponds exist close to each other they form an important network that helps link fragmented wildlife communities.

Frogs, toads and newts eat pests in your garden – newts particularly like baby slugs. They are a form of natural pest control.

Ponds are also good for people, as is any contact with nature. People are naturally drawn to water and a pond is a pleasant place to spend time, relax and watch the wildlife. They’re also great for teaching children about nature through pond dipping and learning to identity plants and animals.

What can I do?

Assuming you plan to do the digging yourself, creating a garden pond is relatively cheap. The main expense is the liner: synthetic ones run from as little as £1 per m² and upwards depending on the material and thickness. Puddling clay can cost anywhere between £40 a tonne plus transport, to £5 a tonne if buying in bulk and can be purchased online from a number of suppliers. After that, there’s the cost of stocking with plants, if you choose to buy them. How much you spend will obviously vary depending on the size of your pond and where you source plants and other materials.

You don’t need a lot of equipment either. You can get a spirit level (for levelling the pond) from a hardware store, and a spade, underlay, pond liner, plants or plant identification guide, and a pond grille or netting if necessary from a garden centre or online.

Time-wise, digging and lining your pond will take a day or so, depending on how hard the soil is, what type of liner you use and the size of the pond. After that, it’s up to you how much time you invest in it, and whether you leave it to be colonised naturally or plant it up yourself. Then you need to factor in a few hours every few months for maintenance (more if problems arise).

See the Freshwater Habitats Trust’s Guide to Creating Garden Ponds for Wildlife or Just Add Water for more detailed information on digging, lining and stocking your pond, as well as trouble-shooting and seasonal maintenance.

Safety

Being quite shallow, ponds are relatively safe. However, drownings can and do happen and small children should never be left unsupervised around water. Educate them about the dangers of water or put up a small fence around the pond or a grille or netting over the top; both will still allow the wildlife to get in and out, and a grille / net will protect frogs and fish from herons too.

If dipping for creatures, or when doing any maintenance, always wash your hands both before and after to prevent the introduction and/or spread of species or bacteria.

Digging your pond

You don’t need a lot of space to make a pond (you can even make one in a sunken bucket or old sink). The most natural way is simply to dig a hole on land where water doesn’t easily drain away (in a large wet field or in very clay-heavy or rocky soil) and wait for aquatic plants and animals to colonise it. However, the success of this approach will depend both on the quality of the soil and the groundwater. Unless both are optimum, you’ll need to line and fill the pond yourself.

Don’t go overboard with the depth of your pond; they should be shallow with gently sloping sides so animals like frogs can get in and out. The greatest variety of wildlife lives in as little as a few centimetres of water at the pond’s edge, where overhanging grasses provide protection from predators. Unless you’re keeping fish, the deepest areas should be no more than 25-30 cm (1ft) to keep water oxygenated and well lit. Deeper ponds should have a surface area of approximately 5-10 times the maximum depth. Make sure you dig a level hole using a spirit level or water will run out, something which can be very difficult to correct once the pond is filled.

Lining your pond

There are a number of ways to line a pond which vary in terms of environmental impact, cost, labour-intensiveness, equipment and amount of land required. This is a brief summary of the most common and environmentally-friendly liners but other options exist. [Note that concrete used to be a popular material for ponds but cement production (the main component in concrete) emits large amounts of pollution and CO² and so is not recommended.]

Puddling clay

Puddled clay is the traditional way of lining ponds and even larger waterways such as canals. Puddling involves working the clay repeatedly by trampling it until all the pockets of air have been squeezed out and it forms a dense, watertight layer. Clay is only suitable for very stable land as any movement in the subsoil will cause it to crack and lose water. For the same reason, clay-lined ponds must be dug well away from tree roots. Clay ponds also need to be kept constantly topped up to the brim so the edges don’t dry out and crack.

Clay is a very environmentally-friendly and cheap material as long as you have a source nearby and don’t have to transport it too far since you may need several hundred kilos, depending on the size and shape of the pond and the kind of base soil (clay-rich soil will require less, while sandy soil needs more). If transporting tonnes of clay over large distances by lorry you obviously need to factor in the pollution this will cause, as well as the cost. Puddling by hand (or rather foot) is also incredibly hard work and will take significantly longer than installing a synthetic liner. If you have to hire machinery to puddle the clay then the environmental impact is obviously greater.

Building a pond with a synthetic liner.

Synthetic liners

Synthetic liners are made from a range of modern materials like synthetic rubber or plastic. While these do create pollution in the manufacturing process, a good quality liner can last up to 25 years so the impact is spread out over the life of the pond. It’s important to remove all stones from the hole first to prevent the liner from ripping. You can provide some extra protection by putting a layer of old carpet or underlay down first. The ‘naturalness’ of a synthetically-lined pond can be increased by covering the bottom with a natural substrate such as clay, washed gravel or chemically-inert children’s play sand. This can be used for planting into and also provides a safe haven for creatures like dragonfly larvae.

Filling your pond

Ponds must be filled with clean water such as rainwater. Water from the tap or hose may contain too many nutrients which discourage aquatic plants and animals while encouraging algal bloom. Rainwater will probably fill your pond naturally, and you can set up a rainwater butt a couple of months in advance to collect enough water to fill your pond and keep it topped up.

Stocking your pond

Plants

Once your pond is dug and filled, you’ll need plants to make it look nice and provide an appealing habitat for wildlife. If you have the time and patience to let nature take its course then you can just wait for plants to naturally establish themselves. While it might not look like a ‘proper’ pond for quite a while, there are advantages to this approach: new ponds have very different ecosystems to mature ones, and the early, unplanted stages favour certain species that prefer to live on a bare substrate, or don’t compete well with others. Even in these seemingly empty ponds you can find a large variety of wildlife if you look below the surface. One major advantage of leaving your new pond to its own devices is that the plant and animal species that colonise it under their own steam will be more appropriate than any we choose. You also avoid one of the major problems of planting-up: accidental transfer of invasive alien plant species. The only potential disadvantage may be more mosquitoes in the early stages, but this will level out in time as predators arrive. As the pond matures, it becomes colonised by plants and gradually silts up, at which point early-stage species move on or their natural predators increase, changing the balance.

If you don’t want to wait, planting speeds up the process and makes things look nicer sooner. It’s important to choose plants that provide the best habitats for wildlife – that create a diverse and complex underwater structure at the water’s edge and provide protection from predators. Low grasses and marginal wetland plants are perfect. In other parts of the pond you can include different types of plant with a range of submerged and floating stems and leaves to give the widest range of habitat types.

You can either buy plants or go out and pick them. If picking, make sure you are either on common land or have permission from the landowner. Never, ever pick from a nature reserve as the risk of damaging a protected species is too high. Plants must be native to the local area, i.e. within a half mile radius (think the distance that a frog can hop) and you need to be very sure about what you are bringing home, as it’s vital to avoid introducing an invasive non-native species such as New Zealand Pigmyweed (Crassula helmsii) or Himalayan Balsam (Impatiens glandulifera). Use a good plant identification guide or seek advice from your local Wildlife Trust first. Don’t be tempted to transfer plants from someone else’s garden pond as this carries a greater risk of introducing non-native species.

If you don’t want to risk picking, the other option is to buy a small amount of native plants from a reputable source. Obviously you can also buy native plants from garden centres but be aware it is not unknown for the seeds of some invasive alien plants to be present in the pots of others.

Wildlife

There’s no need to stock your pond with animals – just plant it and wait. Local wildlife will quickly detect the new water body and some species will appear in just a few days. There’s no need to add sludge from another pond to ‘get it started’ as again this carries the risk of introducing something undesirable.

NB: frogs and toads hibernate in winter, so you need to make sure that your garden has some crevices, rocks, holes or a log pile for them to hide in and under, or that your pond has enough mud at the bottom for them to bury themselves in.

More pond life: dragonfly larva; water stick insect; great diving beetle; 3-spined stickleback; frog tadpole; smooth newt.

Fish

Fish are a natural part of pond life in the wild but prey on other species and so have a disproportionately large impact in a small garden pond. If you want to have fish and other wildlife, then two ponds may be the best option if you have the space. Failing that, make sure your pond has some very shallow, densely covered areas with lots of bordering grasses that fish can’t get to and which provide a safe haven for other species.

Caring for your pond

Ponds can generally be left to do their thing but do require a certain amount of seasonal maintenance. Thinning out plants in the spring and summer and removing unwanted species helps to keep anything from dominating. In winter and autumn, it’s a good idea to remove fallen leaves. While a certain amount of twigs and leaves etc. falling into the water provides a source of food, too much will increase the nutrient level and form a layer on the bottom which can de-oxygenate the water. It’s good to have some overhanging, shady trees to prevent the water from drying up entirely in hot months (although if this happens, creatures will recolonize when the water returns). However, completely overshadowing the pond will block too much light.

It’s a really good idea to ban pesticides, herbicides and synthetic fertilisers from your garden – ponds won’t like the runoff, as it will increase nutrients and toxins to the detriment of pond life; see wildlife gardening.

For country ponds, the most natural kind of management is very gentle disturbance at the water’s edge, such as that caused by animals coming to drink. This simulates the natural processes which have been going on around watering holes for millennia and helps to keep any one plant species from becoming too dominant.

Thanks to Silviu Petrovan of Froglife and Dr Jeremy Biggs of the Freshwater Habitats Trust for information.

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