WORTHINGTON — The Okabena-Ocheda Watershed District will once again test algae samples from blooms on Lake Okabena this summer, following a significant bloom earlier this week.
On Tuesday, board manager Jay Milbrandt captured a photo of the algae bloom while flying over the lake. The bright green hue spanned most of the lake and, upon closer inspection by watershed administrator Dan Livdahl, a significant amount of filamentous algae could be seen floating in the water. It's not known if the algae is toxic to people or pets, hence the testing.
Milbrandt, who had also flown over Lake Ocheda, Indian Lake (near the town of Round Lake) and Silver Lake (near Lake Park, Iowa), said Silver Lake also had a significant bloom, while Indian and Ocheda lakes appeared clear.
During its meeting Tuesday afternoon, the board voted to spend up to $1,000 on testing kits to collect samples of the algae and have them analyzed for toxicity levels. This is the second time the district has authorized funds for this purpose. Livdahl said the last time it was done, in 2019, there were few algae blooms in Lake Okabena and 18 of the 20 kits expired without being used.
While inspecting the bloom from Sailboard Beach earlier this week, Livdahl collected samples and also gathered data on water temperature.
“Last week, (the water temperature was) in the 60-degree range,” he said. “(Tuesday), samples were at least 10 degrees warmer.”
Close to shore, in a 6-inch water depth, the temperature was about 80 degrees. The rising water temperatures, combined with a lack of wind, is ideal for growing algae, Livdahl told the board.
“Is it just aesthetic, is there a smell, a visual, or is there an actual known toxin there?” Livdahl questioned.
Toxic blooms are of special concern because they can be fatal to dogs. Board chairman Rolf Mahlberg said that with both dogs and people in and around the lake, it is important to have the information to be able to inform the public if there is a toxic bloom.
“I would like to see the board proactive on something like that,” Mahlberg said.
Livdahl suggested purchasing five testing kits to start with, but didn’t have a cost estimate for them.
District eyes ISD 518 property for nutrient-reduction project
Also on Tuesday, the board reviewed a draft report from Houston Engineering regarding potential water quality projects that could be incorporated onto the ISD 518 school district property along Crailsheim Road. The property that will soon be home to a new intermediate school is a floodplain for the upper reaches of the watershed, with water eventually making its way into Lake Okabena.
The district hopes to work with the school district to create a sediment basin and potential other projects that will work to settle nutrients out of the water before it flows into the lake.
Houston Engineering developed four alternatives, two of which are considered to be the best options. Both include construction of a single pond that would remove an estimated 80% of suspended solids (236,853 pounds) per year. In addition, either alternative would remove about 300 pounds of phosphorus per year. This is about a third of what Prairie View accomplishes in a year, Livdahl said.
“It’s a big watershed and a small pond (proposed), so they’re essentially saying we need to do more work upstream,” he said. “This does not get us to our goal — we’ll get about one-third of the way. Do you spend $1 million to get a third of the way?”
Manager Steve Bousema said it sounded like a lot of money, and Livdahl agreed, but said it was one of the things that could be done. Livdahl said that in order to remove more phosphorus, upstream farmers would need to implement conservation tillage and cover crops, which would reduce runoff and increase nutrient capture in the soil.
“That’s the only way to make that significant progress, but we couldn’t come up with enough money to bribe a significant number of people to do those things,” Livdahl said.
He also said the district could apply for a Clean Water, Land and Legacy grant to help fund a project on the school district’s property.
“Before we do anything, we’d have to have an agreement with the school district,” Livdahl said, adding that more discussions are needed.
In other business, the managers:
Reported on the Lake Ocheda drawdown. Mahlberg said carp were spawning along his shoreline in the west basin, while Advisory Board member Paul Langseth said a family on the east basin reported carp spawning as well.
“There’s significant numbers of fish that are still alive,” said Mahlberg, adding that he's disheartened by what he’s seen. With the spawning, the carp were stirring up the sediment along the shoreline, and water clarity was poor.
“I think the only way we’ll know if we’ve succeeded is if we get higher water levels,” Livdahl noted. “Until we get some normal weather conditions, I don’t know if we’ll be able to tell what happened out there.”
“It would be nice to get a flush of the system, but I don’t want an 8-inch rain either,” Mahlberg said.
Were informed that a trail camera system has not been installed in Bella Park, as Livdahl was previously asked to do. Livdahl surveyed the area and could not find a place to install cameras with a good view of the shelters, while also being hidden to prevent the cameras from being stolen or vandalized.
Discussed plans to schedule a public meeting with residents along Sunset Bay regarding carp control options in the bay. A meeting time and date has yet to be set.
Approved permits for the city of Worthington to remove concrete from its former structure along First Avenue Southwest, across from Ehlers Park, and restore landscaping on the property; and for Highland Manufacturing to install a hard surface driveway on the north and west sides of its property. The road currently consists of packed gravel.