We're awash in heat - and that's just the lakes

  • Article by: BILL MCAULIFFE , Star Tribune
  • Updated: July 12, 2012 - 9:44 AM

Shallow lakes in southern Minnesota, including at least two in the metro area, have warmed to a rare 90 degrees -- well beyond the temperatures of water-park pools -- thanks to long, hot days and clear skies.

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Some Minnesotans are learning to redefine what constitutes a refreshing dip in the lake.

Shallow lakes in southern Minnesota, including at least two in the metro area, have warmed to a rare 90 degrees -- well beyond the temperatures of water-park pools -- thanks to long, hot days and clear skies.

Jerry Johnson, east metro fisheries manager at the Department of Natural Resources, said he's rarely encountered 90-degree water in his 30-year career, though he did experience it recently in the swimming pool in his back yard.

"It wasn't even comfortable," he said. In Minnesota, swimming pools commonly are heated to about the mid-80s.

Lakes that have breached 90 degrees include Bass Lake in Plymouth and Rogers Lake in Mendota Heights and a handful of swampy bodies of water across southern Minnesota.

But larger, more renowned recreational lakes are also on simmer. Lake Minnetonka last week checked in at 85 degrees, above more normal mid-July temperatures in the low 80s, said Telly Mamayek, spokeswoman for the Minnehaha Creek Watershed District, which monitors the lake. To the south, Lake Pepin is running about 85 degrees as well.

Those are all warmer than the lap pool at the popular outdoor St. Louis Park Aquatic Center and the indoor pool at the Water Park of America in Bloomington, both kept at 82 degrees.

Fatal for fish

The warm water may be less than bracing to people, but it's proven fatal for some fish.

Some large northern pike have died in lakes across southern Minnesota, done in by temperatures beyond what they can handle and the related depletion of oxygen in the water.

"Particularly the larger pike need cool, oxygenated water to make it through those dog days of summer," said Henry Drewes, a DNR regional fisheries manager. "Large pike are the first to succumb."

But Drewes and other fisheries managers said the die-off, which has affected rough fish as well, doesn't appear to have upset fish populations significantly.

The high temperatures and abundant sunlight have also encouraged plant growth in water bodies, which uses up oxygen, a double whammy for some fish. More than 100 large northern recently died in a reservoir in Rochester.

High and dry

Fish kills have also been reported to the north, including Aitkin County, where extensive flooding from heavy June rains has spread water across wide lawns, ditches and other greenery, sapping the water of its oxygen.

Other flood-related problems in Aitkin County are easing somewhat, partly because of a lack of rain. Electricity was restored this week to some flooded homes along Big Sandy Lake, whose power had been shut off for safety reasons. But nine lakes still carry no-wake restrictions, including Big Sandy, a reservoir of the Mississippi River that rose about 6 1/2 feet in heavy rains between late May and late June to its highest level in 60 years. The lake has dropped about 1.7 feet in the past two weeks.

The Mississippi River at Aitkin, which had been so full that Big Sandy could not drain into it, has dropped about 3.1 feet since cresting in June 28 and is expected to keep dropping steadily.

The absence of rain is less welcome elsewhere, as drought presses back in on the state's southeast and northwest corners.

Rainfall since April 1 across much of northwest Minnesota has been 2 to 6 inches below normal and near historic lows. The southeast corner is also running a deficit, in places less than 50 miles removed from areas that received nearly 9 inches of rain on June 14 alone.

Thirty of Minnesota's 87 counties were considered to be in drought at the end of March. The rains of May and June changed that picture, particularly in northeast Minnesota, which had been drier than normal for much of the last two years. But the weekly update to the U.S. Drought Monitor, expected Thursday, is likely to show an expansion of areas considered "abnormally dry" or in moderate drought, inward from the state's south and west borders.

Many of the dry areas this year are heavily agricultural. Crops are now getting by on existing soil moisture, said University of Minnesota Extension climatologist Mark Seeley. "But that can only carry us so far," he said. "If we get too deep into July [without rain], we'll put ourselves right back into a drought situation."

In northwest Minnesota, some small grain crops have already been hurt, Seeley said. Continued dryness could soon present problems for sugar beets and soybeans, he added.

The northwest may be in for some relief from thunderstorms Thursday night and Friday, though chances of more rain are small through the weekend and into next week. The forecast for southeast Minnesota is for continuing dryness.

Bill McAuliffe • 612-673-7646

DROUGHT BOUNCING BACK?

Heavy rain and flash floods have hammered east-central Minnesota in recent weeks, but much of the rest of the state is looking for more rain.

Source: Minnesota DNR Climatology office

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