MNR and Storm Lake Stakeholders Consider Weed Control

Blue-green algae cover the water in a cove in Storm Lake near the Kiwanis Sail Wharf on Monday, July 19, 2021. (Photo by Jake Kurtz)

The Iowa Department of Natural Resources, the town of Storm Lake and various lake stakeholders are expected to negotiate an aquatic vegetation management plan in response to the explosive growth of plants around Storm Lake.

MNR fisheries biologist Ben Wallace suggested that the Lakes Improvement Commission begin discussions on a plan that would outline vegetation management options and possible sources of funding.

The city, LIC, DNR, and the Lake Preservation Association would help fund the plan if “public money pays for management in the public interest,” Wallace said.

“We’re looking at a plan that is being developed this winter,” Wallace told the board. “I want to warn people that we have to be realistic about what the plan would look like. “

The confluence of dry, sunny weather this summer and an emerging water column in recent years has resulted in an explosion of weed growth around Storm Lake. Wallace and lake-watching veterans viewed the growth of recent years as a sign of a healthy lake ecosystem, but this year’s growth has resulted in the most severe algal blooms since the dredging of the lake began. in 2002.

The weeds died in late summer and decomposed in the warmer, shallower lake. Nutrients from rotting weeds were more concentrated due to evaporation – Wallace noted that losing two feet from a glacial lake like Storm Lake could result in a 40% loss in water volume – and weak winds failed to break the budding bloom.

Vegetation management is expected to make progress in preventing the severity of algal growth, which is more of a threat than ever due to lake dredging and zebra mussel infestation. It will also be a boon for water recreation which has become more difficult in recent years as weeds cling to the propellers of boats.

Wallace tempered expectations about the scope of the plan, emphasizing the logic of “public money serving the public.”

Applying a herbicide to 300 acres at Storm Lake would cost $ 96,000, covering just 10% of the lake’s footprint on a temporary basis, Wallace warned. Chemical treatments are considered cheaper and more effective than other options, but they are unpopular among environmentalists and could give way to rapid decomposing algae blooms.

“We have to be realistic, that’s what I always tell people every time we start to write these plans,” he said.

The alternative is to use a mechanical harvester, which is more expensive and inefficient than the herbicide.

“It’s like mowing your lawn,” Wallace said of mechanical harvesting. “You have to keep doing it because it grows back. Like I said, there are no easy options with this.

Wallace said lake watchers should keep this year’s algae blooms in perspective: Water quality has improved dramatically thanks to the city’s dredging and urban water quality initiatives. since 2013.

The resulting vegetation has made the fishery more diverse. Baitfish populations are increasing; populations of largemouth bass have exploded.

“We should never have to champion the concept of clean water,” Wallace said in his closing remarks. “We must be proud of what has been accomplished and benefit from it. “

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