Planning and Building a Water Garden

Skill Level: Intermediate

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Tools & Materials

Planning for Safety

Make sure your plans comply with local building codes. Depending on where you live, regulations may consider a pond beyond a certain depth a safety hazard, requiring it to be fenced in. There may also be rules concerning its placement and size. Always check with your local authorities.

Selecting a Site

A proper balance of sun and shade is essential to a successful pond. The pond site will require plenty of sunlight if you plan to grow flowering water plants. The more direct sunlight the pond receives each day, the more choices of water plants you have. If you plan to add fish to the pond, balance the sun with some shade during the hottest part of the day. Shade can be provided from water lilies or lotus pads, plants or shrubs, or a portable shade screen. Small ponds benefit from partial shade since high water temperatures promote excessive algae growth and increase water evaporation.

Avoid placing your pond near large trees. Falling leaves or needles contaminate the water and accumulate on the bottom of the pond, clogging the pump/filtration system. If there is no alternative, place netting or screen mounted on a wood frame over the pond to catch leaves during the fall season. Also, avoid locating your pond in an area subject to strong winds to prevent debris from entering the pond and to ensure your fountain works properly.

Pond Styles

The style of your pond is a matter of personal taste and should complement the style of your house, garden and other landscape features like decks or patios. Ponds are usually formal or informal. Whether a pond is formal or informal depends on the shape and edging materials. Formal ponds are usually strict geometric shapes and are intended to look man-made. If your garden style is formal, the pond should follow suit. Informal ponds are similar to pools and streams found in nature. They usually have an abstract shape and often include a short stream or small waterfall trickling over natural rocks. Overhanging rocks and border plantings are used to hide the pond edges above the waterline.

Lighting

Choose from several options to illuminate a pond for night viewing. Underwater lights are a popular choice. In order for these lights to be effective, the pond water must be fairly clear and the lights positioned to avoid excessive glare. Some fountain systems come equipped with underwater lights. You can also use spotlights to illuminate surrounding trees or tall shrubs and reflect light on the pond surface. Similarly, placing lights at the pond edge to illuminate waterfalls or fountains creates a nice effect.

Pond Capacity

The most successful garden ponds are 18-24" deep. This depth is considered optimum for growing water lilies and other aquatic plants and is also adequate for raising most types of fish. However, for Japanese koi, provide an area at least 3' deep where fish can escape heat in the summer and frozen water in the winter.

Pond capacity is important when you size the pump and filter and when you determine correct dosages of plant fertilizers, algaecides, and other chemical treatments. The most accurate way to determine pond capacity is to attach a flow meter to the faucet or water supply line and record the number of gallons needed to fill the pond. A less accurate, but easier and less expensive, method is to follow the basic formulas listed below:

                     Rectangular Ponds - Length x Width x Depth x 7.5 = gallons     Example: 10' x 20' x 1.5' x 7.5 = 2250 gallons.

                     Circular Ponds — Diameter x Diameter x depth x 5.9 = gallons.

                     Oval Ponds — Depth x Width x Length x 6.7 = gallons.

                     Irregular Ponds - It is difficult to calculate accurately the volume of an irregularly shaped pond. The best way is to determine the average width and length, and then use the equation for oval ponds above.

Choosing a Liner

Rubber liners are more durable than PVC because they are stretchable and more resistant to ultraviolet light. Thicker liners of any type generally last longer, too. EPDM rubber liners are available in thicknesses from 30 to 45 mil and will typically last about 20 years. PVC liners are available in thicknesses from 20 to 32 mil. The disadvantage to flexible liners is that they are less durable than preformed shells. They tend to degrade more quickly and are easier to puncture.

Preformed shells can last from 5 to 50 years depending on composition, thickness, quality and installation conditions. The best material is rigid fiberglass, which is easy to repair and extremely durable. It may fade when exposed to sunlight, but should last 10 to 30 years. Shells are available in a number of shapes and sizes. Your design choices are limited in comparison to flexible liners, and these shells are usually more expensive for their size.

Sizing the Liner

Flexible pond liners come in a variety of standard sizes. Some garden suppliers carry large rolls of liner material in standard widths. To estimate the amount of liner you need, determine the actual size of your garden pond. The liner must fit the pond and overlap the edges for proper fit. Follow these easy steps:

                     Outline the Shape — After clearing the site of plantings and other obstacles, outline the pond shape on the ground. For irregularly shaped ponds, use flour, paint, or a garden hose to mark the perimeter.

                     Measure Pond Dimensions — Measure the maximum width and length of the pond; then determine the smallest rectangle that would enclose the pond area.

                     Calculate the Liner — To allow for pond depth, decide on the maximum depth of the pond (usually 24"), double it, and add this figure to the width and length of the rectangle. To provide a 12" overlap, add an additional 24" to the width and length of the liner.

                               Formula for Width = Width of pool (Depth x 2) 2'

                               Formula for Length = Length of pool (Depth x 2) 2'

                               Example: Pond is 24" deep and fits inside a 10x12' rectangle.
To figure liner: 10' (the width) 4' (the depth doubled) 2' (for overlap) = 16'.
12' (the length) 4' (the depth doubled) 2' = 18'

So you’ll need a 16x18' liner for a 10x12' pond. For irregularly shaped ponds, you may need to trim excess liner material to provide an even overlap around the entire pond.

Installing a Flexible Liner

Installing a liner requires four basic steps: digging the hole, laying down the liner, filling the pond with water and adding stones or other edging around the pond perimeter.

                     Removing Turf — Use a flat shovel to remove patches or strips of sod within the pond area and remember to remove the grass six to twelve inches beyond the perimeter so you will have a flat surface.

                     Digging the Hole — Starting along the edge, dig out the edging to a depth of nine to twelve inches. Then remove all dirt within the pond area by layers, digging from the center outwards. Dig two inches deeper than the pool depth to allow for sand underlayment (less for other materials). Create a spot to overwinter plants and fish. In cold areas, you need a zone that won’t freeze. It should be three feet deep and three feet wide. Do not place a fountain or pump in this deep zone. Dig an eight to twelve inch shelf for marginal plants (plants that like shallow water). Position the marginal plant shelf so that the plants frame your view of the water garden. Then dig a ledge for the edging as deep as the edging material less one inch, and slightly less wide. The top of the finished edging should be at least one inch above the surrounding terrain to prevent runoff from entering the pond. As you dig,angle the sides slightly, about 20 degrees, and make sure the edges of the pond are level with the other side. If they aren’t level, the liner will show. Check by placing a carpenter’s level on a long, straight board placed over the hole.

                     Preparing the Hole — Carefully inspect the hole for sharp stones or roots and remove them. Flexible liners are susceptible to punctures from rocks, gravel, broken tree roots, and other sharp objects. Cushion the liner with an underlayment of some kind. Options include two to three inches of sand, fiberglass insulation material, or newspaper. Most water garden suppliers offer a tough, flexible underlayment material specifically designed for use with pond liners. Place your chosen material in the bottom of the hole and on any shelves cut into the sides of the pond. Also, pack damp sand into any holes in the sidewalls where large rocks were removed.

                     Positioning the Liner — Pick a warm, sunny day to install the liner. Make it more flexible and easier to handle by spreading it out on sun-warmed pavement for fifteen to twenty minutes. To avoid punctures, do not drag the liner across the ground. With a helper, drape the liner loosely into the hole with an even overlap on all sides. Then weight down the edges with a few smooth, flat stones or bricks. Once the liner is in place, begin filling the pond with water. As the pond fills with water, adjust the liner to conform to the sides of the pond and smooth out as many creases and wrinkles as possible. As the pond fills, ease off the stone weights to avoid overstretching the liner. When the pond is full, trim off excess lining with a utility knife or sharp scissors. Leave enough liner around the pond rim to extend underneath and a few inches behind the first course of edging stones.

                     Adding Edging Materials — To keep the liner in place while adding edging, push 20d nails through the liner into the ground every foot or so around the pond rim. If you’re using natural stones, experiment with several arrangements until you find one that looks natural. Although large flat stones or masonry units can be placed directly over the liner, position them carefully so they will not slip into the pond. To prevent stones from moving, mortar them in place. Mortar comes premixed and is inexpensive.

Installing a Preformed Shell

                     Mark the Shell Outline — Place the preformed shell upright in the desired location. If the shell is completely symmetrical, it can simply be turned upside down and its outline marked directly on the ground. For irregular shapes, use plumbed stakes or a plumb bob to transfer the shape of the pond rim to the ground. Mark the outline with flour, paint, or a garden hose. Use stakes, spaced about 12 inches apart, to keep the hose or rope in place.

                     Dig the Hole — Dig the hole to conform to the shape of the pond shell, allowing an extra two inches around the pond perimeter and two to three inches in the bottom of the hole. If the shell has shallow-water shelves, cut ledges at the appropriate locations to support them. Shells must be fully supported at all points. Remove any rocks or other sharp objects, then line the bottom of the hole with two to three inches of damp sand. Flatten the bottom of the hole with a short board and firmly pack the soil to provide a secure base for the shell. To ensure the bottom of the hole is perfectly level in all directions, place a level on a 2x4 laid on the sand base.

                     Set the Shell — With a helper, set the pond shell into the hole and check the height of the rim. It should be about 1 inch above the surrounding ground to prevent runoff from entering the pond. Add or remove soil from the bottom of the hole to achieve the desired height. Place a long, straight 2x4 across the shell rim in several places and check with a level. If the shell isn’t level, pull it out of the hole and re-level as necessary.

                     Backfilling Around the Pond — Make sure the pond is perfectly level before you fill it with water. As the water level rises, backfill the hole around the shell with sifted dirt or damp sand, packing it gently with a shovel handle or the end of a 2x4. Make sure you fill all empty spaces, especially around shallow water shelves. Make sure it’s level as you go. Do not allow the water inside the pond to rise above the backfilled earth outside the rim or else the shell will tend to bulge outward. Try to equalize the pressure exerted on opposing sides of the shell as you backfill around it.

                     Adding Edging — When the shell is filled with water, you can conceal the exposed rim with rocks, masonry materials, or overhanging plants. If you are using flagstones or pavers, allow them to overhang the pond edges by one to two inches. The weight of the edging may deform or damage the pond walls, so don’t allow the full weight of these materials to rest on the pond rim.

Types of Fountains

There are two basic kinds of fountains: sprays (or fountain jets) and ornamental statuary. If you choose a spray type fountain, place it in a sheltered area so that wind gusts don’t disrupt the spray pattern or blow the water outside the fountain receptacle. Fountain jets come in a wide variety of ornamental spray patterns. Statuary fountains range in design from classical Greek figures to modern art forms. Make sure that you choose a fountain that fits the size and style of your pond.

Choosing a Pump

Still water in a garden pool is beautiful, but moving water adds excitement. Pumps make fountains spray, ponds drain, and water recirculate. Choose from a variety of pumps made specifically for water gardens because they sustain continuous, round-the-clock use.

The first step when choosing a pump is to select a size. To determine the size pump you need, first calculate the volume of water in the pond Choose a pump that can move half the total volume in one hour. For example, if your pond holds 1000 gallons of water, buy a pump that delivers at least 500 gallons an hour. If your water garden includes a waterfall or stream, it needs a more powerful pump. When in doubt, buy a more powerful pump.

Filtration

There are two basic types of filters:

                     Mechanical filters: A wide variety of mechanical filters are available for ponds. Most small ponds use an in-pond cartridge-type filter. The effectiveness of a filter depends on the overall size of the filter and a high water flow rate. Purchase a pump that can circulate the entire volume of water through the filter once every two hours.

                     Biological filters: These filters rely on beneficial bacteria that feed on impurities in the water. The filter contains two or more layers of gravel that harbor large concentrations of nitrifying bacteria naturally found in ponds. As water slowly flows through the gravel, the bacteria break down fish wastes and other organic matter. In the process, toxic ammonia is changed into harmless nitrates, which return to the pond to nourish plants. Unlike mechanical filters, biological filters do not require a high flow rate to operate efficiently.

Adding Plants

Plants and fish keep the pond water balanced and add life and color. Before you stock your pond, check the water. Your water likely contains chlorine. Allow chlorine to dissipate by allowing the water to stand for a few days. Wait several days to a week before adding plants. Then allow two to three weeks before adding fish, snails, and other aquatic creatures. During this time, your plants establish themselves as cover and food for the fish.

                     Floating plants are used to cover the pond surface. A covered surface keeps the water cooler and limits algae growth. Small ponds should usually have a 50 to 70 percent coverage. Floating plants have buoyant leaves to keep them afloat, with roots dangling in the water beneath. They require no soil. Water lilies are the most popular variety. There are two basic types of water lilies: hardy and tropical. Hardy water lilies are frost-tolerant perennial plants. Tropical lilies are frost-intolerant. To save them over the winter, move the entire plant into a greenhouse. Lotus plants are also very popular, producing large fragrant flowers that can perfume an entire corner of the garden.

                     Submerged plants play an extremely important role in pond ecology. These plants grow entirely underwater, providing food and hiding places for fish. Also referred to as oxygenating grasses, they include some of the same species grown in aquariums. Include them in your pond to promote a healthy environment.

Adding Fish and Snails

No water garden is complete without a few fish and water snails. Snails make a big contribution to the pond’s ecosystem because they love algae. Fish control mosquitoes by eating the larvae and help control the algae too. Popular types include goldfish (Red Comet, Calico Fantail and Shubunkins, as well as the common variety), Japanese koi, catfish, and mosquito fish. Before adding fish, acclimate the fish to the pool by adding about 10 percent pool water to the bag four times every fifteen minutes. After placing fish in the pond, don’t feed them for the first three or four days. Then, as they settle in, feed them daily. Never feed them more than they can eat in ten to fifteen minutes. Excess food pollutes the water. Stock your pond with a number of small fish rather than a few large ones to achieve a healthy balance of submerged pond life.

Stocking Your Pond

                     Submerged plants — You need two groups of plants per square yard of surface area.

                     Floating plants — Place water plants, such as water lilies and lotuses, in the pond to cover the surface during summer months. Cover at least 50 percent of the surface. Avoid overcrowding the surface by placing one medium-sized water lily per square yard.

                     Fish — Each fish should have six square inches to one square foot of water. An area of 1'x1' supports a fish two inches long. An area three times as big accommodates three such small fish or one six-inch fish. Koi need much more space, about 25 square feet for every fish. Always err on the side of too much space. Use the table below to stock your pond:

                               2" fish: 1 square foot

                               4" fish: 2 square feet

                               6" fish: 3 square feet

                               8" fish: 4 square feet

                               12" fish: 6 square feet

                     Snails — Place eight small snails in the pond per square yard.

Routine Maintenance

Shop for ponds and fountains.

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