Big Eau Pleine Water Quality

The primary reason for the winter fish kill is low levels of dissolved oxygen under the ice.  WVIC monitors the oxygen levels at one mile increments throughout the reservoir.  WVIC uses this data to determine when the aerator is needed to provide a large area of open water with improved oxygen levels to act as a refuge for the fish.  The isopleths shown below identify the areas of acceptable and dangerous oxygen levels. 

Oxygen levels below 3.0 ppm (parts per million) are very concerning for fish survival. Levels below 1.0 ppm are deadly (black on the graphs). Normally an oxygen deficient area develops mid-winter in the deepest areas of the reservoir toward the dam and expand as winter progresses. This is due to decomposition of the large amount of sediment that collects in the deepest water.

During a mid-winter thaw, the corresponding run-off will often form an area of very low oxygen levels, a sag that will flow through the reservoir. These movements are monitored and are also used to determine the start-up of the aerator.

Most Current Isopleth

How with the new aerator help?

Below is a 1980 era aerial photo of the old aerator in operation. You can see where the open holes are in the ice, which is directly above each pair of orifices at the end of each line. WVIC drew over the old photo the locations of the aerator orifices for the new aerator. Moving some of the 14 aerator lines and orifices with the new system will form a larger continuous open hole in the ice. Each of the orifices and its line are assigned a number.  The lines are set between 23 and 30 feet deep (at full capacity).

Big Eau Pleine Citizens Organization
PO BOX 335
Mosinee, WI 54455
Feedback@BigEauPleine.org