Updraft: October 1, 2012 Archive

Land of 9,999 "shrinking" lakes? Is White Bear Lake MN's "climate change canary in coal mine?"

Posted at 7:04 PM on October 1, 2012 by Paul Huttner (2 Comments)
Filed under: Climate change

Falling water levels mean closed beaches at White Bear Lake.
Source: Freshwater Society

2003 the last time White Bear Lake was at "ordinary high water level" of 923.42 feet above sea level

5+ foot drop in lake level from "normal" level since 2003

2" White Bear Lake is within about 2" of all time record low reached in November 2010

86F water temperature in White Bear lake on July 17th of this year

Has 25% of the water volume of White Bear Lake "disappeared" since 2003?

Docks stretching more than two hundred feet search in vain to find water in shrinking White Bear Lake these days.
(Click to enlarge image for detailed view)
Source: Google Earth

White Bear: Incredible shrinking lake:

These are difficult days for people who swim in White Bear Lake's usually cool waters and call it's receding shoreline home. Plummeting water levels on White Bear may be part local geography, and part of a bigger trend on Minnesota's 10,000+ lakes.

White Bear Lake has always had big fluctuations in lake levels.

But the sustained drop in the water levels in excess of 5 feet on White Bear since 2003 may be a harbinger of things to come for Minnesota's Land of 10,000 lakes.

The plunge in water levels of White Bear and other Minnesota lakes, marshes and ponds mimic a shift to a warmer climate regime in Minnesota in the past decade.

White Bear's unique geography and hydrology make it extra sensitive to changes in precipitation and increased evaporation rates associated with a warmer climate.

-White Bear's relatively small watershed makes it especially vulnerable to reduced winter snowfall and the spring runoff that feeds the lake. With less area for runoff into the lake, it takes more rain and snow to boost water levels in White Bear.

-Longer "ice free" seasons (by 2 to 4 weeks or more) open the lake surface to increased evaporation in spring and fall.

-Hotter summers, and warmer, longer spring and fall ice free periods each year mean more water is sucked form the surface of Minnesota's lakes than in decades past.

Increased evaporation makes our lakes increasingly vulnerable to any reduction in annual rain or snowfall.

Increased Groundwater Pumping: Draining White Bear from below?

A very timely and in depth piece from The Freshwater Society highlights the threat to White Bear's water level from increased groundwater pumping below the lake.

Source: Freshwater Society

Here are some excerptsfrom the Freshwater report.

From mid-2003 to the present, White Bear's water level dropped more than 5 feet. In late 2010, concern about the drop among citizens and officials in communities around the lake led to a $200,000 research project conducted by the U.S. Geological Survey with assistance from the state Department of Natural Resources, the Pollution Control Agency, the Board of Water and Soil Resources and the Metropolitan Council.

The research, funded by the USGS, the state and a number of local governmental units, reinforced some old theories and produced some new evidence about the causes of the lake's decline.

The findings so far:

-White Bear drains a very small watershed and has always had big decreases in area and volume during extended dry periods when rainfall and melting snow do not keep up with evaporation.

-Chemical testing of water from wells around the lakes confirms that lake water is flowing out the bottom of the lake into groundwater aquifers that feed those wells.

-Pumping from high-capacity wells in suburban communities that mostly draw their water from those aquifers more than doubled over the last 30 years.

There are varying scientific opinions, but some believe as much as 25% of White Bear's water volume may have been lost from below due to increased groundwater pumping in the aquifer below the lake.

A regression model simulated the impact on water levels of the precipitation decline and the increased pumping. The pumping accounted for nearly four and a half feet of the water level decline between 2003 and 2011, according to the simulation. That four-and-a-half-foot difference across the lake equals a staggering 4.8 billion gallons - a loss of more than a quarter of the lake's previous volume.

Not everyone buys the notion that groundwater pumping around the lake has had that big an impact. "I accept that the added pressure from that municipal pumping on that aquifer had an effect," said Luke Michaud, the vice chair of the White Bear Lake Conservation District. "I'm skeptical of that four feet."

Source: Freshwater Society

White Bear Lake: Canary in a Minnesota climate change coal mine?

As drought deepens and climate shifts in Minnesota a bigger question looms.

-Is a smaller White Bear Lake unique, or part of a larger trend of "shrinking" Minnesota lakes?

White Bear is not the only Minnesota lake that's receding these days. Take a close look at ponds and marshes in your neighborhood that are drying up. Other lakes are showing the stress of deepening drought through lower water levels.

Low water means high docks at Deephaven Beach on Lake Minnetonka Sunday.
Image: Paul Huttner-MPR News

The water level in Lake Minnetonka has dropped nearly 17" (16.8") since June 22nd.

Even mighty Lake Superior is down well below the mean lake level for early October, and trending downward toward record low observed water level.

Source: NOAA Great Lakes Environmental Research laboratory

Water levels in some lakes like Gull and Minnetonka are managed by dams. Managed lakes are less vulnerable, but not totally immune to falling water levels from a shifting climate and increased groundwater pumping.

There is little doubt that the documented shift to a warmer and longer "ice free" climate with warmer spring and fall periods in Minnesota will expose our 10.000+ lakes to increased surface water loss through evaporation.

Combine that with hotter summers like 2012, increased drought, less winter snowfall and subsequent spring snow melt runoff to boost lake levels in spring and you create a scenario that puts a high degree of stress on Minnesota lake levels.

White Bear Lake may be unique. It may also be trying to tell us something about the future of our Land of 10,000 Lakes.

PH

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