Ponds can be a boon and a bane. For retaining or detaining water from a stormwater system, or within a site, they serve their purpose well; in addition, ponds can greatly enhance a site’s aesthetic appeal. On the flip side, however, that standing water can become an eyesore at best, a health hazard at worst. But keeping algae and breeding mosquitoes at bay can be a simpler matter if one takes a tip from nature–by keeping the water moving. Towering falls or raging rapids aren’t required; simple fountains, aerators, or bubblers can often do the trick.
Putting the Sun to Work to Clean Water
“We went around the whole horn to kill algae and weeds in our manmade lake,” says David Mayes, stormwater services manager for Greenfield Municipal Utilities in Wilmington, NC. “Chemical treatments, dredging. We get nutrient pollution from stormwater drainage, from the surrounding 2,600-acre, very urban watershed. Since we get 55 inches of rain a year, we see a lot of drainage.”
The “very old” manmade lake, nestled in a city-owned park, includes a spillway, the flow of which can be adjusted with valves, but that still wasn’t enough control. “We actually hired a pond and lake management company to help us decide what our strategy would be,” continues Mayes. “We looked at aerators and bubblers, but those meant adding infrastructure and power bills. The consultants came up with the SolarBee recommendation.”
Based in Norwalk, CT, SolarBee Inc. manufactures solar-powered circulators in Dickinson, ND. Products are dispatched nationwide in company-owned trucks equipped with trailers and small boats. Final assembly occurs at the customer’s site by SolarBee factory-trained employees, taking into consideration customers’ water-quality objectives, which may result in configuration or deployment differences from “standard.” Once assembled, circulators are suspended from the back of a truck and lowered into the water by a SolarBee crew. Once afloat, a circulator is towed into position by the SolarBee boat crew, anchored into place, adjusted, and powered on.
“We had our SolarBees installed in 2005,” says Mayes. “Our staff goes out every other week and checks on all four units. From time to time, something might get stuck in an impeller shaft, or the unit might clog; maybe a fuse will blow. But since installation, they’ve run quite well.”
“Once in a while we get some vandalism,” adds stormwater supervisor Carl Scott. “Someone once broke some panels. We called SolarBee, and they sent out new ones, no problem. Before the SolarBees, blue-green algae was a big issue for us. We sprayed pesticide on it yearly, which didn’t control it, but helped a little. With the SolarBees, we’ve been able to reduce by about two-thirds what we used to put in for algae.” The solar-powered circulators don’t do everything, he notes. “We still get lake-edge vegetation–mostly water primrose, water hyacinth, duck weed, cattails–which we must remove mechanically. Some of it we spray. We also flush the lake out once a year.”
“We also added sterile grass carp, a fish that will consume weeds,” adds Mayes. “In the spring, we add Sonar herbicide to regain control of lake vegetation. Where other herbicides can drop to the bottom of the lake, rot plants, and rob oxygen from the lake, Sonar works slower, and we don’t see such problems. Also, SolarBee actually added oxygen to the lake, about 20%, in the main body of the lake and kept it up.”
To further keep the lake clean, Greenfield Municipal Utilities conducts public outreach and education about putting trash in its place and prohibitions on dumping wastes down storm drains. “We’ve stenciled storm drains, and we have some grates with actual castings of “˜Don’t dump,'” says Mayes.
Another bonus: If you clean it, they will come. “For years, a local advocacy group, Cape Fear River Watch, has operated the concession stand where canoes and paddle boats are rented, for use on the lake. Prior to us doing all this work, few people wanted to rent boats, and those who did demanded their money back because the lake was so thick with stuff. After the SolarBees went in, receipts from boat rentals went way up–people wanted to be in the lake.”
Humans aren’t the only beings who like the “new” lake. “It’s always heavily populated with birds,” he concludes. “Ducks, geese, herons–it’s like you’re not in an urban area. And they pulled a 12-foot alligator out of there last year.”
Beauty Is As Duty Does
Although ponds many times serve a practical purpose, they’re also considered a “feature”–something of beauty to behold from one’s deck, or a source of recreation. In upscale housing developments with a water feature, cleanliness is a must. If a homeowners association doesn’t take care of its water feature, the local city or county might condemn and drain it.
“It’s a small lake, seven to 10 acres, inside a gated community of 94 homes, all which face the lake,” explains Red Le Cain, lake manager for Pinewood Lakes Homeowners Association in Bakersfield, CA. “There’s a dock every other house. The lake’s average depth is six to eight feet, and its temperature probably never drops below 55 degrees. Homeowners can enjoy fishing and boating–sailboats and small electric motor boats, but no gasoline-powered boats. The lake’s about 38 years old; I’ve been taking care of it for about a dozen years.” Le Cain, who’s retired from mechanical work, volunteers his time to maintain the lake. “I live here, so I have 1/94th interest in it,” he chuckles. “Working on it keeps me young. As the lake’s a mile around, just walking it gives me exercise.”
The lake serves function as well as fun. “It’s also used as a reservoir for the irrigation system. We have to refill it from a deep well, sometimes daily, during the summer. There’s a Gunite wall around the lake, and four inches of bentonite clay on the bottom.” Early on, there were basic rules for the lake. “There was a series of recommendations that disappeared; people who designed the lake had some sort of manual. But homeowners can’t plant things in the lake, nor throw things in it for the fish, which breed beneath each dock. We have mosquito fish and varieties of lake trout and bass, a sunfish of some sort. Any fishing is all catch and release; we don’t restock. It appears the fish population hasn’t grown nor depleted much, although birds of prey do come in for the fish. The only problem we’ve had with mosquitoes is that owners need to maintain their boats; water gets in there. I’ve been paying kids to pump boats out.”
But, as with any still waters, there was a problem. “We had an extreme algae problem. We put all sorts of chemicals in it, but that never worked for a long time. Within a week or two, algae would come back. It was so thick in one portion, it looked like you could walk on it. This went on most of the summer, and it would smell bad. Sometimes we hired folks to scoop it out. For a while, we’d allowed people to put indoor-outdoor carpet on their docks where they tied up their boats. However, that wicked the fertilizer from lawns, and algae just loved that and grew. Now we don’t allow that.”
Le Cain needed to find an algae solution. “I looked at other lakes in 110-degree weather areas, to find out what they did to fight algae. The name EP Aeration kept coming up, so I checked them out.” EP Aeration, located in San Luis Obispo, CA, manufactures and installs aeration and ozone systems. Its units are simple and inexpensive to maintain, generally requiring less than two hours per year to service.
“The EP Aeration system went in about six years ago,” says Le Cain. “Twelve hundred feet of perforated tubing went into the deepest center portions of the lake, attached to 1/3-horsepower compressors on shore. This compression system creates a current, causes motion on the lake. Yes, there is some noise from these compressors, but I added four decorative fountains, one in the lake’s center, and the rest at the tip of its estuaries, as white noise to cover
compressor noise.”
The system worked. “We’ve significantly lowered our chemical use, and we never get accumulated algae any longer, and we now attract a good number of winter residents–birds, coots or mud hens, which mow the “˜underground lawn’; they eat any vegetation in the lake. The thing we like most is the water quality. The lake now looks like a swimming pool, no mater what the temperature. The water’s so clear you can see the fish.
“We also have savings in power consumption,” he continues. “We once used 20-horsepower water circulation pumps, trying to clear the lake. Now we do it all, aeration and fountains, with only 7 horsepower. Plus the old, big pumps didn’t work, and the fountains were a pain to maintain. We have a lot of pine needles that get in the lake, which would plug up the pumps; every time one failed it was about $2,500 for electricians and rewinding the motors, and this happened every season. That doesn’t happen with the EP Aeration system.”
Le Cain has few complaints. “During the installation, we divided the chores up, decided what to do, and modified the system to work with our culture here. EP Aeration is always accessible and extremely easy to work with. Sure, the system needs maintenance, but I save up little chores. I have five extra compressors as backup, and when I need something, I’ll ride over there, hang out with the guys, and get new bulbs for the ozone generators. Having a system that actually works is unheard of! And EP Aeration’s service is remarkable, too.”
Algae Won’t Grow Where Waters FlowRon Joseph, owner of Berea, OH’s Aquatic Weed Control, maintains and manages water sites for a variety of clients. “What a landscaper does on land, I do on water. We put in chemicals, stock fish, maintain and install water features for residential and commercial sites–and also trap muskrats. It all depends on what the basins are being used for. Algae growth and mosquitoes are common problems. We can use algaecides, but movement of water defeats algae, while it also stops mosquitoes from laying eggs.” What about using fish to eat mosquitoes? “Then birds come to eat the fish,” he says. “Fish are usually only used when that’s part of the pond’s purpose–for people to fish. Large-mouth bass or bluegills are the major species; people fish for bass, and the bluegills are there to feed the bass.”
Many of the lakes Joseph maintains are rain-fed; however, summer 2010 brought a drought to Ohio. “A handful of lakes were having trouble keeping filled, not only because there was little rainfall, but also due to the high temperatures. Many times, we had to compensate by using chemicals to eliminate algae. Then, when lakebed is exposed, you can get weed growth. Any grass that shows up is chemically treated, not mowed.”
All these factors can cause problems. “Golf courses, homeowners associations, commercial sites–they’re paying for the water’s aesthetics,” he says. No matter what the water level, the site has to be maintained. “If no one comes in to do the work, the county or city will come in and do it, then bill the site owner. That’s where I come in.”
For lakes and ponds that retain their water, Joseph depends on aerators and fountains from Air-O-Later in Kansas City, MO. The company sells aerators and fountains that increase oxygen levels in water, which reduces surface algae formation and maintains a balanced ecosystem throughout the pond. In some applications, the equipment promotes evaporation, which helps lower the water level before the next rain while also decreasing the water temperature.
“I chose Air-O-Later because of the amount of water they move–about 1,000 gallons per minute,” says Joseph. “The power unit, which is located on the shorelines, operates on 220 volts. How many fountains you use depends upon the surface acres and shape of the pond. For a pond of a half to a full acre, you could probably use just one fountain, but some situations are different. A surface aerator can shoot up to five feet high, with the water spray covering an area 15 feet in diameter. If the fountain’s being installed in a housing development, the residents have to approve how many, and what kind, of aerators or fountains are used.”
Once the aerators are installed, is the job finished? “Sometimes,” says Joseph. “Unfortunately, developers don’t tell the homeowners anything about how to help keep their water features healthy. It would be good for residents not to fertilize their lawns near the pond–but mostly I just have to put in more chemicals to compensate.”
Keeping It Clean, Making a Screen
Hinds Community College’s Rankin Campus, in Pearl, MS, recently added a 75,000-square-foot building that not only expanded learning space but also will bring more visibility to the campus, which is situated along Interstate 20, a major east-west route through the state. Because a stormwater retention pond for the 60-acre campus was an integral part of the landscape, Weatherford-McDade Ltd., the project’s designers, sited it so the pond became an attractive
focal point.
Adding to the pond’s beauty were the installation of two 15-horsepower Polaris Giant Fountains manufactured by Otterbine Barebo Inc. of Emmaus, PA. The fountains, which have a 750-gallon-per-minute flow rate and produce thick, 30-foot plumes of water, not only create agitation (helping to keep the water from stagnating), but also provide a tranquil, splashing white noise, masking the traffic noise of the nearby interstate. In addition, an Otterbine 3-horsepower Triton Mixer was added to help keep the water circulating and the rich oxygenated surface waters mixed throughout the pond. Wind controls were also installed to help keep overspray to a minimum because of the pond’s proximity to pedestrian traffic.
But What If You Want Fish?
“Ponds aren’t really a natural system; humans create them,” says William A. Wurts, Ph.D., state specialist for aquaculture in the Cooperative Extension Program at Kentucky State University. “My job is teaching people how to make ponds for fish. Perfectly clear water is not the best for fish, because clear water allows so much sunlight to come through, and that encourages plant growth. It’s nature’s tendency to turn ponds into a bog, and plants would do that. One management tool–adding fertilizer at a rate of 30 pounds per acre–helps stimulate growth of a phytoplankton bloom, which blocks light to inhibit big plants that would clog the pond. But fertilizer should be used only in a pond without rooted plants or other aquatic weeds, because fertilizing cattails and water lilies will make them grow like crazy.”
What about “natural” weed controls, such as waterfowl? “Ducks might make the problem worse, as they make manure, which is a plant fertilizer,” he says. “Many of my clients are in rural areas, farmers. Unfortunately, fish and livestock don’t mix. Again, manure–a nutrient load problem.” Neutral to slightly basic is the best pH range for a pond: 7.4 to 8.4. “7.4 would be perfect. Total alkalinity should be above 20 milligrams per liter.”
Merely digging a hole and waiting for rain does not a pond make. “I suggest pond construction to be no less than three feet deep,” he says. “Of course, once you figure evaporation rates, maybe you’d need to make the pond no less than five feet deep–but no more than eight feet, the depth for a life-sustaining ecosystem. Water absorbs all the red wavelengths of light in the first meter; that’s why the top of a pond is warmer. Blue light gets deeper and does not get absorbed as quickly, making the water appear blue. This level is cooler, and creates layering, which can cause low oxygen levels at lower depths. Forty to 60 inches of rain a year is a rate that is good for keeping ponds full.”
