Storm Lake may be ready for water clarity shot, says a man who has studied the issue



Storm Lake and Worthington, Minn., share similarities: Each is a town of around 12,000 to 15,000 largely populated by immigrants employed in meatpacking. They also each have considered adding aluminum sulfate to clear up their muddy, turbid lakes.

We mentioned about a year ago that Lake Okabena was a candidate for aluminum sulfate. A friend with relatives in Worthington said they tried using the chemical — which binds to silt particles and sinks them to embed them in the lake bottom, where they are not resuspended in the water — said they tried it and it didn’t work.

Fact is, aluminum sulfate never was tried in Okabena.

It’s not ready yet. But the watershed manager for the Okabena-Ocheda Watershed District, Dan Livdahl, tells me it is an effective treatment for turbid lakes. He notes that it has been used in lakes around the Twin Cities for years and has cleared up lakes of 25-30 feet deep.

Livdahl, who has worked on the watershed for 27 years, said the watershed does not have enough conservation practices to make a water-clarity program last.

“Our watershed is not under control,” Livdahl said. “We’ve gone as far as we can get with this generation of farmers.”

About 80% of the Storm Lake Watershed is in some form of conservation practice. Neighbors to Little Storm Lake have done yeoman’s work installing wetlands and other protections for the lake from erosion. The fact that Outlet Creek has among the lowest nutrient loads in the Raccoon River Watershed is testimony that watershed efforts here have been successful. Even after a heavy rain during dredging the nutrient load is relatively low. The lake is not capturing all that sediment. The lesson is that far less sediment is being delivered to the lake than it was before watershed improvements. It is showing up after 20 years of hard work, evangelizing and investment.

Storm Lake is bigger than Okabena (3,000 acres v. 775) and deeper (22 feet v. 7 feet). Storm Lake is in the midst of dredging. Okabena was dredged from after World War II to the mid-1980s.

Okabena has a bay that acts as a catch-basin for storm water discharge. Improvements need to be made there. There needs to be more cover crops, buffer strips and other conservation practices to stop the mud flow into the lake. Most of Southwest Minnesota’s rivers have been declared unfit for aquatic life because of nutrient loads.

In short, Southwest Minnesota has a bigger landscape problem than Northwest Iowa does to hear Livdahl tell it.

“It sounds to me like this is the right time for you to try it,” he said of the chemical application.

Worthington residents have been skeptical of aluminum sulfate for the same reasons their Iowa cousins in Storm Lake are: Clear water promotes vegetative growth, and it is part of our state culture to fight weeds even when they are under water; and, they think that aluminum sulfate because of its name is dangerous.

“People just don’t want vegetation in their lake,” Livdahl said.

Okabena feeds shallow aquifers from which the city draws drinking water. They are afraid aluminum sulfate will pollute their cup of coffee. Little do they know that the chemical is commonly used to clarify drinking water. In fact, Worthington uses it.

Livdahl said those aren’t the main reasons Okabena has not been treated. He said it doesn’t make sense to clarify the lake when so much sediment continues to run in. A chemical treatment might cost $1 million in Okabena but last only five years. In Storm Lake, because of its small watershed, large lake size and depth, and the relatively small amount of sediment coming from the landscape, the treatment is expected to last 20 years and cost around $3 million to treat the entire lake.

Fyra Engineering of Omaha studied Storm Lake and proposed a phased-in treatment system. A wave-break wall will be built 1,000 feet east from the Chautauqua Park jetty. Three contained cells would be built using fabric walls in Chautauqua Bay. Varying amounts of aluminum sulfate would be added to see how the lake responds and what sort of vegetation takes hold. Based on those tests, the treatment could be expanded in the lake.

In-lake vegetation promotes species diversity — we could have a healthy perch population, finally. Maybe walleyes could reproduce naturally in Storm Lake, which they cannot now. Vegetation helps hold sediment in place. It can be managed so boat propellers are not bound in seaweed. In Lake View, they are “mowing” weeds near docklines so boat traffic is not impeded.

Vegetation can grow in water up to about seven feet deep. Storm Lake’s center would be largely free of vegetation, as Black Hawk Lake is.

But it is important to note that aluminum sulfate was not a failure in Lake Okabena. It simply has not been tried. It works on some lakes but not on others still taking on sediment. Livdahl said it will take at least 10 years to get the watershed under control. After that, “We have to do something.”

Aluminum sulfate will be considered, he said.