By Rich Sacher, New Orleans, Louisiana
At this point you may start to think about the expense and labor of installing a concrete pond, and our 95 degree days are just about enough to stop this pond daydream in its tracks. However, with the advent of newer pond liners and pre-formed pools, the misery associated with concrete mixing and finishing is a thing of the past. Heavy duty pool liners with 10 year guarantees are now common, and can sell for as little as $1.00 a square foot.
Preformed ponds in many different shapes and sizes are also an alternative method to create a quick pond at less cost than using concrete. Using these materials, the average gardener can install a decent size pond in less than one day, and have it stocked with plants, fish and fountain by the following morning.
The simplest kind of pond to build is an above-the-ground pond. Since no digging is required, it usually takes much longer to fill this pond with water than it does to build it! There are many variations on this theme, but as an example, one can use treated lumber planks which are at least 2 inches thick by 12 inches wide, nail them together to form a rectangular shape of the desired dimensions, and place the form where the pond is desired. This bottomless "box" can be placed directly on the grass, concrete, a deck, etc., and then the bottom is covered with some kind of padding or cushioning material. Most books say to use sand, but I think the perfect material is roofing felt. It is cheap, convenient, lies flat, makes a barrier to weeds, and provides a good cushion for the pool liner.
Once the roofing felt is in place, the pool liner can be dropped into the form and you begin filling the pond with water. A few staples on the outside of the pond form may be needed to keep the liner from blowing into the pond, but be sure to use just a few, and place them at the edge of the liner. As the pond fills, the weight of the water will do a good job in smoothing out wrinkles, but if you are a perfectionist, you can help smooth them out by hand before there is more than one inch of water in the bottom of the pond. While the pond is beginning to fill, you can check the level of the form, and if it needs to be raised a little on one or two sides, this can be done by carefully inserting some shims to raise the forms where needed.
If you prefer the pond to overflow on a certain side (like, into the flower bed, rather than onto the deck!) then you may want to leave the overflow side a quarter inch lower than the rest of the pond. You should wait until the pond is completely filled before cutting any excess liner or doing any permanent stapling. This will give the water pressure enough time to pull the liner into every nook and cranny where it needs to go; some of those few holding staples which you used to hold the liner in place may actually tear loose as the pond fills, but if you stapled the liner on the outside of the form, near the edges, then no harm is done... you will be trimming some of that excess liner off, anyway.
It really does take longer to fill this kind of pond than it does to build it. I once built a twenty-by-thirty foot pond in two hours but it took all night for it to fill with water. I think an ideal depth for an above ground pond is about 14 inches, but it can be deeper or more shallow than that, depending on what materials you are using for the form. Railroad ties, landscape timbers, concrete blocks, etc. are all possible materials for pond building. Remember that any kind of wood must be pressure treated if you want it to last more than a year! Although I mentioned rectangular shape, if you have some carpentry skills, you can also do triangles, pentagons, ponds within ponds, etc. Ponds built with treated lumber planks do not need any side support if they are less than 8 feet or 10 feet long; if you are building larger than that, you will want to drive a stake into the ground where the planks are to be nailed together, so the water pressure won't make the planks bow outward. So, if you know how to use twelve nails to nail four planks together, then you can build a pond. If you are feeling lazy, have the lumber yard cut the planks to size you need. Borrow your neighbor's staple gun, find those scissors buried in the kitchen drawer, and you are in business!
Pond liners can also be used to make an in the ground pond. The advantage is that you can make any shape pond you want, and the ground itself supports the sides of the liner. It is a good idea to use a flexible garden hose to lay out the pool shape you want. Once everyone agrees that it is a pleasant shape, and it is large enough, you can dig a trench along side the hose, and start digging. Remember, the pool does not have to be more than 12 to 16 inches deep, so don't get carried away. If you want a waterfall, some of the excavated soil can be mounded up near the pond for later waterfall construction. In some cases, it may be useful to use some of the soil for a berm around the pond, so that is another way to dispose of excavated soil.
Once the pond is excavated, check the level, decide which side you want excess rainfall to flow from, and then you are ready to line the hole with roofing felt, running it across the pond, up the sides onto the edges of the pond. Drop the liner in, weigh it down lightly with some rocks around the edges, and start filling. Again, do not trim any excess liner until the pond is completely filled. Some pond books say you should create a shallow shelf in the pond before putting in the liner, but they don't have our river sand and rainfall to deal with. I think it is better to build the pond to a depth of 14-16 inches, and just use bricks to prop up those bog plants that don't want to sit too deep in water. This gives greater flexibility in rearranging the pond plants as you wish, and avoids the calamity of a shelf suddenly slumping into the pool.
When using pool liners, whether in the ground or above the ground, it is important to conceal the edges from sunlight, since that is what eventually breaks down most liners. Using stones or lumber planks to finish off the edge of your pond will make it more appealing, and enable the liner to live up to its ten year guarantee. Even the heavier, preformed plastic ponds should have their edges covered by sod or some paving material, so the sun can't reach it.
Some final pointers: if possible, locate your pond away from trees, in a place that gets at least five hours of direct sun daily. This will allow you to grow a wide variety of pond plants. Be sure to use a dechlor product when you first fill the ponds... the new chemicals in our drinking water do not dissipate quickly and they will kill your fish and damage your plants, even ten days after you have filled the pond! Be sure you are pleased with the size and shape of your pond before you start - so you won't say "I should have made it bigger, or longer, or rounder, etc.", within two hours of filling it! And last, but not least, if you decide to do an in-the-ground pond, why not serve refreshments and get some friends to help . . . friends will have all kinds of useful ideas on how you should do it ... which is fine, as long as they keep digging.