What can happen to the lakes during a dry summer in South Dakota

KELOLAND.com Original
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SIOUX FALLS, S.D. (KELO) — It’s been hot and dry and some lake levels have dropped in the region but so far, folks are still catching fish and swimming in most lakes.

Yet, the dry drought conditions have created some unusual late June and early July conditions in lakes, said Dave Lucchesi, an area fisheries supervisor for the South Dakota Game Fish and Parks. Lucchesi is based in Sioux Falls.

The stinky, potentially dangerous to pets, blue-green algae likes to grow in the hot, sunny, dry conditions happening in the state and region now, Lucchesi said.

“It appears we are farther along in the summer than we are. It’s felt a lot like late July and August,” Lucchesi said.

If the hot, dry weather keeps up, then look for the cyanobacteria or blue-green algae to grow, Lucchesi said. And that means advisories about swimming and danger to pets could be posted on some South Dakota lakes.

And, if dry conditions continue, lake levels could continue to drop in some areas.

Until then, the public is using the lakes, sometimes with some adjustments.

Adjust to changing lake conditions

“You are starting to see people make adjustments on docks,” said Paul Johnson of Lynn Lake Lodge in Day County, near Webster in northeast South Dakota.

Docks that reached the water in 2020 may not reach it in 2021 so they may need to be extended or moved to other areas.

Property owners along Lake Cochrane in eastern South Dakota in Duel County near the border with Minnesota are also adjusting their docks and lifts.

“People are putting their docks and lifts out further, especially this weekend when kids and grandkids will be around to help,” said Susan Norgaard, the co-president of the Lake Cochrane Improvement Association.  

Fishing on a South Dakota lake in 2020.

Norgaard said in her email to KELOLAND News that the lake level has probably dropped a “good foot” from last year.

“While some people do not like to see the water drop other parts of the lake are enjoying the fact that the wave action is not beating up their shoreline,” Norgaard said. “The bay area has the biggest concerns about the level of the lake because at one time there was cattails that grew there.”

Some area lake levels have dropped about two feet, Johnson said. “You can see it go down one to two inches a week in some lakes,” he said.

Some lakes, such as Lake Thompson in Kingsbury County, reached record water levels in 2020. A drop of two or three feet may return them to more normal lake levels, Lucchesi said.

Lake Cochrane had high water levels in 2019 but no flooding because of an outlet, Norgaard said. The water level returned to normal in 2020.

Overall, changes in lake levels can require boaters to be more attentive, Lucchesi said.

“They need to be careful. Rock bards or points that may have been submerged four, five or six feet…may not as covered,” Lucchesi said. “If a lake level drops three or four feet that can create some hazards for boaters.”

Many boats have depth finders which can help boater navigate the changed water levels, he said. Still, “They have to be careful and realize that (conditions) have changed and they need to adjust accordingly,” Lucchesi said.

Go fish

Water temperatures have reached the mid-80s in some lakes in his area, Johnson said. “That’s almost starting cooking the fish,” he said.

“When you have warm days and calm water fish don’t always have the energy to survive,” Lucchesi said.

Especially if algae are not producing oxygen at night. There can be a summer fish kill similar to a winter fish kill.

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Blue-green algae on Lake Mitchell in 2019.

“We’ve not witnessed that yet this year,” he said.

Blue gills and bass can do better at lower water levels and higher water temperatures than a northern perch or walleye, Lucchesi said.

In general the fish are still biting on South Dakota lakes as of June 30, Lucchesi and Johnson said.

“So far, the fish are biting surprisingly good, considering the hot weather we’ve had,” Johnson said.

But fishing has been “very slow” at Lake Cochrane, Norgaard said. “…Not a lot of fish have been caught.”

The next wave of change?

So far, the cooler nights have been advantageous in terms of slowing the growth of blue-green algae and fish health, Lucchesi said.

But those conditions along with calm waters can foster increased growth in blue-green algae, he said.

Algae, even blue-green algae, produce oxygen. But on calm water nights, the plants can use more oxygen than they produce, Lucchesi said. That can lead to a fish kill.

Also, sunny and hot conditions can spur growth in blue-green algae which can choke out healthier plants, Lucchesi said.

The Lake Cochrane association just got water samples back and there was no blue-green algae in the swimming area at the lake, Norgaard said. “There was a minute amount at the boat landing,” she said.

Johnson said while the drop in water levels have cleared water from some gravel roads that were closed because of high water, the downside is that habitat for waterfowl could be losing water.

Lucchesi said he frequently walks by duck ponds near where he lives in Brookings. He hasn’t seen water levels so low in some of those ponds for 10 years.

Johnson is also worried that if farmers cut conservation acres for needed hay yet this year, that could negatively impact hunting habitat.

Blue-green algae on Lake Poinsett in 2019.

The next 30 days will be critical in terms of that hunting habitat, Johnson said.

Lucchesi said if water levels continue to decline any potential problems would be impacted by the winter.

If the winter has a lot of snow and ice and lake levels are low, the oxygen supply in lakes could be tapped out which could cause a fish kill, Lucchesi said.

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