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Lessons Learned from Viewing Seasonal Mixing Pattern

Ice Grindstone Independence West Upper Bay - Minnetonka Halstead's Bay - Minnetonka
northern, urban mid-state, forested Minneapolis metro area Minneapolis metro area Minneapolis metro area
small, deep, good water quality mid-sized lake, deep, very good water quality small lake, deep, moderate water quality large lake basin, deep, moderate water quality small embayment, shallower, poor water quality

1. The WOW lakes all thermally stratified in the ice-free season; that is, they separated into layers of warmer water overlying colder water.

2. In spring, summer, and fall, the upper warmer layer was relatively uniform in temperature,oxygen and also other RUSS parameters, indicating that the wind was mixing this layer thoroughly.

3. Deeper water below the sharp temperature dropoff at about 4 to 6 meter depth (the thermocline) shows a steady decline in oxygen throughout the ice-free season. This hypolimnetic water is cut-off from atmospheric oxygen until the water column cools off enough in the fall for the wind to completely mix the lake.

4. Because of a lack of oxygen below the thermocline, cool and cold water fish habitat is greatly reduced or absent for most of the ice-free season in Halseds and West Upper Bays, Lake Independence, and Ice Lake. Grindstone however, maintains adequate dissolved oxygen thoughout most of its hypolimnion in summer.

 

 

 

 

 

 

 

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date last updated: Wednesday March 03 2004