Maintaining Clean Water in Ponds, Lakes and Fountains

Date Published: 
June, 2004
Original Author: 
Tom Smith & Tom Pfeifer
Spring Grove Cemetery & Arboretum, Cincinnati, Ohio
Original Publication: 
ICFM Magazine, June 2004

Water features can add beauty and value to any property. Through proper planning and maintenance, you can ensure that your cemetery's water feature remains an asset.

WHAT: Water features are closely associated with cemeteries. Chinese cemeteries designed according to the ancient principles of feng shui require proper placement of water features. Ponds and lakes are part of what makes the great rural cemeteries beautiful parks. Water features are found even in areas of the country famous for their desert climate. There's something primal and soothing about the sight, sound and smell of a body of water.

WHY: Like all landscaping, ponds and lakes require attention. Over time, they silt in. An overheated pond can metamorphize into a smelly algae soup with alarming speed.

HOW: A good way to approach the subject of water feature maintenance is to talk about how to design a new pond or lake in a way that will keep future maintenance costs down.

The day a new pond or lake is built, it starts trying to silt in or fill in. There's a fancy term for it in aquatic management: eutrophication. That means filling in with dead or decaying organic matter or siltation.

The smaller the pond, the sooner the need for maintenance. Of course, that's assuming you want to try to keep it free of plant life. If you don't care, if you want the whole thing to be covered with water lilies, that's a different approach to water management.

We've gone that route—one of our lakes is named after water lilies. That results in very inexpensive maintenance.

What every pond or lake is trying to do is get shallower, so that finally after a long period of time, be it 100 years or 200 years, it's hardly there anymore. It may be more of a bog.

If a lake is covered with a scummy mass, the reaction you're going to get from visitors is, "Ewww!" Even though the process at work is a natural one, most people will find it ugly and smelly, and you're better off with no pond than with one people find disgusting. So unless bog is what you're aiming for, you need to fight the eutrophication process through proper planning of new lakes and ponds and maintenance of existing ones.

• Dig deep. Generally speaking, the deeper the pond (we'll use "pond" and "lake" interchangeably in this article) the better. If you've got a nice, deep lake, the water on the bottom will stay colder. That will keep the overall temperature in the lake lower, reducing the amount of plant life stealing oxygen from it.

A shallow pond will heat up more quickly under the sun, which encourages plant growth. You can go home Friday leaving behind a clean lake and come back on Monday to a lake that looks like someone came in over the weekend and dumped algae into it. It's what we call an algal bloom, and it's courtesy of that nice warm water.

• Make the banks steep. This reduces the growth of weeds (more unwanted plant life) around the water's edge. In a pond smaller than an acre, it's harder to get steep sides.

• Consider keeping most trees at a distance. A tree-lined pond can create a beautiful ambiance, but if the trees are deciduous their leaves are going to collect in the pond. That's more organic matter that is going to end up on the bottom of the pond, bringing on the need for dredging sooner.

• Try to reduce wind and lapping erosion. On the windward side of the pond, the erosion is going to be more noticeable. Even in small ponds, you can tell the prevailing wind direction just by going out and examining the erosion. We want to minimize erosion, since that means more siltation. You can do this either through a natural plant barrier or an artificial barrier.

If you want to use an artificial barrier, we recommend a stone edging, commonly called rip-rap.

If you want to have a more natural erosion barrier, consider bald cypress, a neat plant that can be used in about three-quarters of the country. When it's growing near water, the bald cypress will extend what are called "knees" from the root system to obtain more oxygen. These extensions stick up about 24 to 30 inches and are called knees because they look like a person lying down on the ground with his knees bent and sticking up. These knees are attractive and they reduce the wind erosion by protecting the shoreline.

If you plant a bald cypress away from water on upland soil you won't see a single knee. The tree does well in either dry or wet conditions.

• Make sure the watershed provides a good filtration system. Again, you want to try to keep nature from filling up your lake. It makes sense to locate a pond at a low point in a watershed so that water will tend to drain into it from surrounding fields, meadows and woodlots, recharging it. But you want that water to be as clear as possible when it flows into the pond.

The best filtration system is an outstanding turf. Good strong turf is going to be the best sieve you can have to keep silt out of the pond.

• Stock it with fish. You can put some bass and bluegill in there, but be sure to include some triploid amur carp. The great thing about them is if you offer them a worm they'll look the other way, but offer them a ball of grass and you'll catch one every time. They are also called grass carp, because they are vegetarians and will eat weeds. Algae isn't their favorite food, so they won't solve your algae problems, but they can be part of the solution.

They can also have some public relations value. These fish can get to be very large, 40 or 50 pounds. When you're doing a garden talk at the cemetery or you have a class of children visiting, take a bucket of grass clipping and throw them out on the surface of the water. It's a hoot to see these things come flying out to eat the grass—it looks like porpoises bobbing. From a distance, a large carp can look like a shark slicing through the water.

You must use only government-certified triploid amur carp. The triploid ones have been genetically engineered so they cannot reproduce, like mules. It used to be possible to buy amur carp that were not triploid and sometimes they would reproduce and get out of control, crowding out other species. The fish and wildlife people did not like that, and now only the triploid ones are allowed.

We've never seen it, but they say if the triploids run out of grass to eat they'll jump out of the water so they can get to the grass on the banks. In any case, you don't want to put too many in a pond. There's a formula to follow (X number of triploids per thousand acre feet of water), and if you exceed it the fish won't have enough to eat. Don't think, "Well, if three would be good, 20 would be better!" We have five or six per pond, and a lot of our ponds are 2 to 4 acres.

Next, Part 2: Fountains, chemistry and dredging.