Starting a garden is not as simple as throwing a few seeds in the ground. By the same token, installing a garden pond is not as uncomplicated as digging a hole, tossing in a liner and filling it with water. Water features, as we call them today, have always been a part of great gardens and yours can be great, too, if you remember a few tips when you install a primary element of a water feature---the pond.
Start with clear objectives and professional advice. A simple garden pond with a few water lilies is one type of project. The one with fish like koi requires running water and a biological filter, often necessitating construction of a second pond. Ponds in cold climates have special insulation needs and ponds in warm climates need bacterial safeguards. Before laying out your pond, be sure it is large enough and produces the right habitat for the type of life that it will support. Even if you have a kit that contains "everything you need," consult a specialist at a local pond supplier or in an organization like a local affiliate of the Associated Koi Clubs of America.
Lay out the design with a garden hose or garden gypsum and dig the hole several inches beyond the basic measurement of the outside of your pond liner. Remove rocks and any sharp roots or other hazards that could damage the liner or shift when the ground freezes. If your pond will be home to fish, dig it deep enough to support them---3 to 4 feet at the center---to afford shelter from winter freezing and neighborhood predators.
Install the plumbing. Most ponds will need a water supply to fill and a sump pump to "backwash"---remove waste through a drain at the lowest point in the basin. The amount of fill and frequency of backwash depends on what's going to live in your pond. Fish will need 15 to 20 percent clean fill each day. Fish ponds will also require "biological" filters---second ponds with mechanical filtration tanks that drain from the bottom of the basin, filter and return clean water to the main pond, usually through a waterfall. The filtration pond should be excavated and lined at the same time as the main pond. Other plumbing, including skimmers that pull water from the surface into the filtration system, should also be installed before the liner is installed and the excavation closed. Be sure to check all connections and correct leaky connections before installing the liner.
Level and set in the liner. Drive stakes in around and tie strings across the hole to keep the liner's edges level. Or use two-by-fours and a carpenter's level to show you where the liner's edge should sit. Backfill underneath the pond base with sand and reinforce deep sides with rocks and sand before setting the liner in. Once the liner is installed, check plumbing again for leaks.
Add surface features like waterfalls, stone surrounds and plantings. If you have fish, build up the edges so that fish cannot "fly" out using sloping sides and predators can't wade in to wait for them to try. A 2-foot drop should be about right. Fill the pond and run the filter for a day or two to oxygenate water and evaporate any chlorine in your local water supply before adding plants or fish.