An expert runs through how to choose wisely and the pitfalls to avoid. By Hannah Stephenson.

If your garden's not big enough for a pond, but you'd love a water feature to add some cool and calm to your outside space, there are plenty of options.

Pools in pots, sculptures trickling water and wall attachments spouting a stream can all be easily sorted - but there are some basics you need to consider, says award-winning landscape and garden designer Helen Elks-Smith (elks-smith.co.uk), a member of the Society of Garden Designers (sgd.org.uk).

"You want good surfaces and you want good plants - and if you are time-poor, I'd be cautious about water," she says for starters.

Pots can be high maintenance

"The issue is, if you have a small body of water, it heats up. When water heats up it goes green," Elks-Smith warns. "But if you have a small element of water, you can probably drain it when it goes green, clean the container and fill it back up again."

If you have, for instance, a half barrel lined with pond liner for a water feature, the frequency with which you'd have to change the water depends on where you position it.

"Oxygenating plants can help to keep the water a bit cleaner," she notes. "Water lilies can added to still water but they don't like moving water. Flag irises can be added, but the depth of the water will have a bearing on what you can plant.

"Often it's a good idea to have a little shallow area, like a little shelf you can pop plants onto, which are planted in little baskets. Not a lot of plants which grow above the water like the water really deep."

Consider filters

Elks-Smith says: "If you have a still bit of water - and they are very popular - you may have to have a large amount of filters moving the water.

"There are loads of kits available, which often come with filters or you can buy them from specialists who will advise you on the type of pump and filter you need."

Balance it out

"You don't want plants to be too invasive in a small container, but some irises are really beautiful. We planted an equisetum in a water feature scheme in Winchester, which has these horizontal bars on it, which is very striking and contemporary looking," she adds.

For modern gardens

"Even if you plant for nature, it doesn't have to look homespun. You can have something that's up-to-the-minute. Nature doesn't mind.

"Think about why you want water in the garden," suggests Elks-Smith. "For some people, looking at the reflective surface is what matters. They don't want the water to be moving, they want it still. Creating a reflective surface is a great way of bringing the sky down and bounce the light around. Others wouldn't want water to be that still."

Check your sound

"There are many different types of sounds associated with moving water. If you have water falling from a height, you will get a lot of splash and it's quite busy to look at and will make a big sound.

"You could have water falling from the same height at the same rate onto different things, and it will sound different," she notes. "If you want a gentle trickle, the water would be going over a surface as it drops. The classic is water falling through a rockery, where you'd see it more than you'd hear it."

Wall-mounted water features

"There are kits where you prop it up or build it against a wall, and the water will fall out of a chute into a body of water," says Elks-Smith. "The traditional thing would have been a lion's head, while a more contemporary version is a steel chute.

"These wall-mounted features tend to be slightly noisier, depending on the height and speed of the water and how wide the chute is. If you want to change the sound underneath, you can bring something up from the ground for the water to fall on, such as stones or pebbles."

Plant in shade

"If you have moving water, shade helps stop the water from going green, but then whatever you are pushing that water over (such as rocks or pebbles), if it's trickling, they will go green.

"That can be lovely - put your water in a cool, shady space, where you can plant around it with ferns and woodland plants. So you can choose to go with green water."

They're not always good for wildlife

"Not all forms of water feature will be great for wildlife, although some can be," she observes. "For example, if you had a stone or a sculpture with water running over the top, which went into a hidden reservoir, that's not going to be of any benefit to wildlife.

"You have to have an open body of water, and on balconies that would be a bit more of a struggle. But if you have a bird bath with a bit of water in, that's absolutely fantastic for birds."

Sculpture-led streams

You can buy water feature sculptures, typically where a hole has been drilled in it and the water is pushed up through the hole. Many have hidden reservoirs, where a pump and filter sits. The reservoir will need topping up and cleaning from time to time, and Elks-Smith advises you'll need an outside electrical supply to run it, installed by a qualified electrician.

Patio position

"It makes sense to be able to see and hear your water feature at the same time," says Elks-Smith. "And consider that you might still want to see your water feature in the winter, when you won't be in the garden but you can see it from your kitchen sink, or if you are sitting in your lounge. Think which window would make a good viewing point."