Water garden construction is, in principle anyway, easy. It is simply a matter of digging a hole, dropping in an underliner, a liner and a re circulating pump and filling with water. Put in a few plants, fish, snails and such and its done. You have a functional water garden. How attractive it is, though, is another story – and that is where a lot of the work comes in.
The hole should be of a pleasing shape, geometric for a formal garden, natural for an informal. Depth is not terribly critical for over wintering fish because of the effective pond heaters which can be purchased. (As long as the water doesn’t freeze all the way down, and poisonous gasses can escape, the fish will be fine all winter.) But a pond that is three feet or more in any direction looks best with a depth of at least 18 inches. For larger ponds, some portion, especially in cold areas, should be 3 or 4′ deep. (My water garden is about 6 ft. on the long side and over two feet in depth at the deepest part. Vary the depth. A shallow section where the fish are easily visible and where you can feed them and watch them romping around is a pleasant feature.
Also, when digging the hole, build shelves into the sides. These are useful for placing margin plants and for hiding the liner and pump elements with river stones. Two shelves is ideal but one will work, especially on a small pool.
It is critical that the top edge of the hole be level all around. To check this, take a long, straight board and lay it across the pool with a level on it, or use a string with a line-level. Where it is low, build up with soil or lower where it is high. Getting this right will make it possible to fill the pool to the top with no portion of liner showing.
When the hole is dug, clean it of any protruding roots and large rocks, then place in the underliner. This can be an old carpet, a carpet liner or liner protection fabric, purchased from the suppliers. Make it as smooth and neat inside as possible, folding the material into pleats. Work from the inside to the outside, starting at one place and working around the sides in one direction. Leave a little extra over the edges and cut away the rest.
Next comes the liner. There are several material choices for the liner, my preference generally being 45 mil EPDM Pond Liner material. This is flexible, relatively easy to work with and is strong. 30 mil Butyl rubber Pond Liner is also good and is a little easier to work with. Lay the liner in as you did the underliner, working out the wrinkles, and folding over the excess. Leave about a ft. extra over the edge and trim away the rest. (A linoleum knife, if you can find one, works well. A utility knife is also fine.)
Once the liner is in place, mark the water level, fill it and let it sit several hours. There should be no drop in water level. If there is, go all along the sides and look for a low spot. Most likely that is where it is losing water. Holes are not common and should not occur if you have been reasonably careful.
Being possessed of abundant wisdom you no doubt acquired all the materials you would need for this project before beginning. Thus, you now find yourself surrounded by a ton of river rock and perhaps field stone of all sizes and shapes. River stone is rounded by the effect of water and looks right in water. Field stone is also a natural stone, weathered and smoothed and looks good around the outside of the pond.
You also have your pump near by. (The size of the pump you will need is a factor of the gallon capacity of the pond. Your supplier will tell you how to determine that and help you to select the right size.) (Or go to landscape-design-garden-plans.com).
Recirculating pumps draw water in through a filter and pump it back out, usually through plastic tubing which runs from the pump to outside the pond, usually to some sort of waterfall. From there it runs back into the pond, aerating the water and providing visual and audio pleasure. (Fish love this. You’ll often find them sporting in the water as it pours into the pond.) The filter can either be connected to the pump or you can use an external filter for easy cleaning.
Place the pump in the deepest portion of the pond, on the opposite end from where the water returns to the pond. Hopefully that will also be somewhere you can easily get at it. Run both the electric cord and the plastic return hose up the sides of the pond. Before you cut the hose, which carries the water from the pump to the waterfall, make sure it is in place with enough extra hose with the pump for easy lifting for cleaning. Since you don’t want to see the pump, place rocks on both sides of it, both just a little taller than the pump, and lay a rock over the top. Use the rest of your river stone and the field stone to lay into the sides and along the top for a natural look. Sand and or small rounded gravel can be poured over the bottom.
You next need to create the means by which the water is returned to the pool – a waterfall of some sort. This needn’t be elaborate and shouldn’t be out of proportion to the pond. Above all, make sure that where the water comes out of the tubing, no portion of it fails to make it back to the pond. If it does, the pond will slowly, but surely empty. This is why you left extra liner. Put extra liner behind and around the waterfall, all sloping to the pond. Water may escape and run under the bottom of the rocks but will still end up back in the pond. More than ninety percent of ‘leaks’ occur at the waterfall.
Build your flow-way or water fall over the liner and try to have the water drop from the lip of a smooth, flat stone into the pool, or to run over rounded rocks into the pool. Put attractive stones over the tubing, making sure not to crush it so much such that you get a spray of water instead of a flow.
It is a good idea to look at natural water features, streams and such, or at pictures of them to get stone placement right. Nature has a wonderful way of distributing stones along and within a stream or pond and an imitation of that, as much as possible, will give you the best look.