Board keeps focus on algae, even in winter
WORTHINGTON — While a thick layer of ice may blanket Lake Okabena this winter, the health of the local lake is never far from the minds of Okabena-Ocheda Watershed District board members.
During the district’s meeting Tuesday, board member Jay Milbrandt said he was concerned about the algae situation that continues to plague the lake during the spring, summer and fall, adding that the green-tinted ice in late 2013 was a frequent topic of conservation.
Throughout the past year, the OOWD worked with Bioverse, a local company that manufactures products to equalize nutrients and reduce the severity of algal blooms. The products generally are marketed for use in small ponds, not large water bodies like Lake Okabena.
While OOWD Administrator Dan Livdahl said he has yet to receive a report from Bioverse about its findings, the products used in the Glenwood Heights stormwater pond and in Whiskey Ditch may have had some impact.
Bioverse used 32 of its Aqua-Spheres in the Glenwood Heights pond last season, and water clarity was excellent from early spring until August, when filamentous algae “got pretty bad,” Livdahl said.
“We knew the spheres weren’t going to work for that,” he said, adding that the pond has a history of filamentous algae growth.
Meanwhile, the AquaSpheres used in Whiskey Ditch may have made a better impact.
“I don’t remember a big bloom of algae being pushed up to 10th Street and stinking,” Livdahl said. “Normally we have that, and I didn’t notice it this year.”
He said he didn’t know if it was a result of the AquaSpheres, or if there were other factors involved, but suggested the district try using the AquaSpheres again in 2014.
“If we went several years without a stinky algae bloom in Whiskey Ditch, it might be worth several thousand dollars,” Livdahl said.
In 2013, the watershed district also established four floating islands in the E.O. Olson Regional Stormwater Pond on the Minnesota West campus in Worthington. The islands, which were seeded in a variety of perennial forbs and grasses, are an attempt to soak up excess nutrients coming into the pond from surface waters that flow off the campus and points north and west. During periods of high water, the pond overflows into a channel that outlets in Lake Okabena.
Livdahl said the big question now is how the islands hold up in the ice this winter and whether the plants will grow again in the spring. The four islands were installed last May at a cost of $6,000 for materials and plants.
While the islands work to remove nutrients, Livdahl said to make a measurable difference in nutrient reduction, the company that manufactures them suggests the islands cover 5 percent to 10 percent of the water body. The four islands in the stormwater pond cover slightly more than 1 percent of the area.
“We have some money left over from this past year, and the college gave us some money back,” Livdahl said, adding that there is enough money available to purchase two more floating islands for the stormwater pond. He also suggested that water quality monitoring be done at the point where water comes into the pond and where it flows out to measure the success of the floating islands.
If they do prove successful at reducing nutrients in the water, board members discussed the feasibility of anchoring some floating islands in Sunset Bay.
Livdahl said the bay, which is 39 acres in size, would require many more floating islands than the 1.5-acre stormwater pond.
“We haven’t even been in this a year. We don’t know what’s going to happen with what we’ve got,” cautioned board member Casey Ingenthron.
“There are lots of questions we don’t have the answers to yet,” added Livdahl.
Additional monitoring is planned on Lake Okabena this year. The OOWD is working with Wenck Associates to collect data on the lake this year. As a result of the monitoring, the watershed district will spend approximately $8,000 on equipment to measure water flow coming into Lake Okabena at Whiskey Ditch and Sunset Bay, as well as a sensor that will be installed on Sailboard Beach to measure the lake’s water level.
“With those two pieces of equipment, we can measure the amount of water flowing into the lake and the amount of water leaving in a year’s time,” Livdahl explained. “At the same time, we can measure water quality and get a good idea of where pollution is coming from, whether it’s building up in the lake or being imported.”
Tuesday’s discussions about projects precede a March deadline in which the watershed district has to complete its annual plan. Ongoing projects, as well as potential new ideas, will be discussed at future meetings.
In other action, the board:
- Authorized the administrator to hire Dennis Rick to complete the watershed district’s audit.
- Approved contracting with the Heron Lake Watershed District for up to five hours of work from the HLWD’s summer intern. Livdahl said the intern will assist in water quality monitoring for the OOWD.
- Approved a request from the Department of Natural Resources to construct a ditch plug on Herlein-Boote Slough to block water flow into the Okabena-Ocheda Watershed. The DNR will use soil from the OOWD property to construct the plug and has agreed to reseed the area once weather permits. The DNR wants to complete the project this month.
Livdahl said once the work is done, Herlein-Boote Slough will likely become a part of the Kanaranzi-Little Rock Watershed District.