If you have ever spent time gazing into a lake, exploring tidepools along the coast or watching a stream tumble over pebbles and stones, you know how calming and relaxing water can be. To enjoy that experience every day, add a water garden to your backyard. It's easier than you might think.

Planning a water garden

A wonderful addition to any landscape, a water garden can be designed as a reflecting pool - a glassy surface that mirrors the sky and the surroundings - or it can be planted and nurtured as a miniature ecosystem, brimming with life and activity.

A modest water garden can be contained in a barrel or trough, an elaborate version can wind through an expansive space with waterfalls and fountains, and there are an infinite number of options in between.

Below are basic instructions for creating a water garden, which can be made in virtually any shape. In general, a square, rectangular, oval or circular pool has a somewhat formal feeling, while a free-form, asymmetrical shape is more "natural" and informal.

Surprisingly, the larger the water garden, the easier it is to establish and care for, since the temperature in a large volume of water fluctuates less than in smaller pools, and algae won't be so likely to take over. A depth of 18 to 24 inches is essential for plants like water lilies, and a surface area of at least 50 feet is ideal.

When choosing a location for your water garden, here are some factors to consider:

- Look for a spot that will allow you to best appreciate the garden: Will you be able to see it from the patio, from the kitchen window?

- Make sure it gets enough direct sunlight. Water lilies and many other aquatic plants need a minimum of five hours a day, and more is better.

- A level surface (or one that can be leveled easily) is best, and you should avoid low-lying areas, since runoff from lawn chemicals can harm the aquatic life.

Construction and installation

Every water garden needs a liner. Preshaped fiberglass liners are available, but I like the versatility of a flexible liner, made of rubber or PVC, which conforms to the shape and size the gardener chooses. A good liner can last 30 years or more. Lilypons Water Gardens is an excellent source for liners and all the supplies you need, including plants (call 800-723-7667 for a catalog or more information).

1. Mark the outline of your water garden with rope, and strip the sod inside with a shovel. Now dig the hole 2 inches deeper than you want the pool to be, angling the sides out slightly. You can make a shelf around the edge of the pool for shallow-water plants (10 to 12 inches wide and deep), or a shallower one for decorative stone edging, called coping (the exact measurements depend on the stones you are using).

Make the bottom of the hole as flat and even as you possibly can, and remove all rocks and roots that could puncture your liner.

2. Make sure the edges of the hole are level: Lay a 2-by-4-foot board diagonally over the hole, and place a carpenter's level on top. Remove or add soil as necessary to make the edges even. This is important, since discrepancies can cause water spillage.

3. To protect the liner, add builder's sand to the bottom of the hole to a depth of 2 inches. Rake the sand so it's smooth and even. Cover the sides with a soft un-der-liner. (Old carpeting can be used for this, or underlining can be ordered from a water-gardening catalog.)

4. Unroll your liner on the grass, and reroll or fold it from opposite ends, so the rolls meet in the middle. Center it in the hole, then open it up, making sure an equal amount overhangs each side.

5. Use a garden hose to fill the pool with water, which will press the liner into the corners and contours of the pool. Let it settle for a day before trimming the edges of the liner, leaving an overhang of at least 6 inches all around.

Hide the overhang with flagstone, rocks or other decorative stones; you can mortar these in place for a more secure border.

Wait about a week before stocking your pond with plants and fish. Many gardeners add a pump and filter, which generate movement in the water and help keep it clean.

Plants and other living things

A well-chosen combination of plants makes a water garden not just beautiful, but balanced and healthy.

Plants that grow underwater, called submerged or oxygenating plants, can help reduce algae and contribute oxygen; many have pretty, feathery foliage that can be admired through the water.

Water lilies, Nymphaea, with their lovely, often fragrant blossoms and leaves that float on the water's surface, are deep-water aquatic plants; the pots containing their roots generally need to be 11/2 to 2 feet under water. Lotuses, Nelumbo, rise above the pond with exquisite flowers and foliage.

Free-floating plants have small roots suspended from their leaves, and don't need containers at all. Marginal plants prefer shallow water, making them good choices for the perimeter of a water garden.

Don't forget about fish, which will help you control pests that could damage your plants; freshwater snails, which aid in keeping the water clean and clear; and tadpoles, which are fascinating to watch as they grow into insect-loving frogs.