WORTHINGTON — Efforts to improve water quality in Worthington’s Lake Okabena appear to be working, say members of the Okabena-Ocheda Watershed District.
During its meeting Tuesday, the group talked about water clarity and the presence of beneficial submergent vegetation in the lake at a level that hasn’t been seen for years.
“I’ve never seen it this nice — especially by the Fourth of July,” Manager Jay Milbrandt said. “The water was perfect. It was warm, it was clear and there were subaquatic plants all over.”
Watershed Administrator Dan Livdahl said there hasn’t been a single algae bloom on the lake yet this year — the kind of bloom that turns the shoreline a blue-green hue and carries a nasty smell equivalent to rotten eggs.
Typically, Lake Okabena experiences its first big algae bloom in June, and from August through September there’s usually a bloom somewhere on the lake. The last algae bloom on Lake Okabena was in June 2019.
That, Livdahl said, is remarkable.
“Last year and this year we had fairly clear water early in the season,” he shared. “As the season goes on, we get some algae growing … and we also get more suspended sediment in the water. It loses its clarity as time goes on.”
While Livdahl said it would be nice if Lake Okabena remains clear all the time, it isn’t likely because of its status as a prairie lake.
“If we can have fewer algae blooms, we’re doing something right,” he added.
That “something right” is a combination of things, starting with the water retention and sand filters the watershed district had constructed on the former Prairie View Golf Links north of Interstate 90. While the project had its challenges — two consecutive years with significant damage to the water filtration system due to flooding — Livdahl said it's settling solids and nutrients from water runoff before it flows toward Lake Okabena.
It’s not working at 100% yet, however. The district has been challenged to get vegetation established around the storage ponds because every time it rains, the water level rises. When the water rises, it erodes the land.
The June 18 storm that dropped 3 to 4 inches of rain on parts of Worthington resulted in “absolutely terrible” water runoff flowing into the Prairie View system, Livdahl said, noting the deep brown color of the water that carried lots of floating debris with it.
Because the runoff overwhelmed the capacity of the Prairie View storage ponds, the nutrient-laden water flowed downstream and into the lake. That particular storm also sent runoff through Olson Park, with a lot of dirty water rushing into Sunset Bay.
Vegetation taking root
Livdahl has found Sago pondweed and Chara algae growing in areas of Lake Okabena this summer — signs water clarity in the lake is improving. Both take root on the lake bottom and are beneficial to fish and waterfowl.
Chara can grow up to several feet long, with stem-like branches and forked leaves. According to the Minnesota Department of Natural Resources, the advanced form of algae stabilizes bottom sediments, provides food for waterfowl and cover for fish. It also supports insects and other small aquatic animals, which are important foods for bluegills and bass.
Livdahl also found coontail and duckweed growing in Sunset Bay.
“I’ve never seen so many subaquatic plants,” Milbrandt shared. “I like what I see, and I hope we can continue to build on that.”
“All the efforts that have taken place in the last 20 years has to be doing some good,” Watershed Board Chairman Rolf Mahlberg added.
“I think we need to appreciate it when we don’t have algae blooms,” said Livdahl, noting that water clarity is making it more enjoyable for people to recreate on the lake.
While the watershed board is pleased by the water clarity in Lake Okabena, the work to improve it further is ongoing. The board continues to discuss the potential to partner with Independent School District 518 on some sort of water retention or water quality improvement project on its property once the plans are more fully developed for the new intermediate school along Crailsheim Drive.