The 27-acre, 120-million-gallon lake is not a health hazard, but its surface becomes an ugly green when the weather heats up. The reason, a high concentration of nutrients at the bottom of the man-made lake.
The nutrients are causing a bloom of the algae population. The algae cause the lake to turn green, and when baked in the sun, release a foul smelling odor. After a number of complaints had been sent to the Reston Association (RA), a study on the water quality of Lake Anne was conducted. The study compared the water quality of Lake Anne to that of Lake Thoreau.
The reason for the comparison is the appearance of the two lakes is different, yet they are both situated in the same environment. The study also included historical notes about the two lakes, made possible because the RA started keeping track of water quality in all of Reston's lakes in 1982. Since then, the RA conducts six tests each year, testing for water clarity and levels of chlorophyll a, among other things.
"We want to get it [the water appearance] back into a situation like we saw in the '80s," said Larry Butler, the RA's director of Parks and Recreation. Butler added nothing could make the lake look the way it did when it was first made, more than 40 years ago, short of draining it and scraping the sediment off the floor. That option is a costly one. Instead, Butler and his fellow presenters suggested other ways to treat the problems.
Bill Kirpatrick, an aquatic environment consultant presented short-term solutions to the problem. Kirpatrick said what seems the most viable solution is the introduction of copper sulfate to the lake. The ion is toxic to the algae, but not to the water. There would be no health hazard in swimming in the lake water or even drinking it. "Although I don't recommend drinking the water from Lake Anne," said Kirpatrick, "it is safe if the pets drink it." The copper sulfate solution is relatively inexpensive as well, $2,500 per year for the treatment. However, the treatment would require multiple applications, which would be visible. The staff applying the chemicals would use a boat to spray the chemicals into the water. Also the application would treat the symptoms and not the cause. The pros of the treatment are that it is effective, provides for a healthier lake, better water quality, improved recreation and an improved habitat.
ANOTHER SHORT-TERM SOLUTION discussed by Kirpatrick is the introduction of more predatory fish to the lake. He explained the smaller fish in the lake eat the zoo plankton, the grazers who eat the algae and therefore keep its concentration in check. Larger fish, such as bass, eat the smaller fish and therefore inadvertently protect the zoo plankton. By manipulating the fish population, said Kirpatrick, the algae can be controlled more.
The RA's watershed manager, Diane Saccone, proposed some long-term solutions to the problem. Working upstream and fixing the eroded banks of the many streams in the watershed would improve the water quality. Introduction of buffers, such as trees and shrubs, would stabilize the shoreline, she said, which would help reduce the storm water runoff into the watershed. Saccone added that the overpopulation of geese is also causing a problem. Egg addling is conducted to control the geese population. Saccone added geese have changed their behavior, they are no longer seasonal migrants, but have become residents of Reston. If Reston residents did not feed the geese, less of them would want to stay.
Saccone said Lake Anne is an important community asset. "This is where Reston began," she said.
RA Board director and Lake Anne resident, Vicky Wingert, encouraged the RA to move forward with the short-term and long-term solutions regarding the problems. "It is our responsibility to take care of our open spaces."