FIELD TESTING OF AN ICE-PRESERVING WINTER LAKE AERATION SYSTEM1

ABSTRACT: Artificial aeration is used to prevent winter fish kills due to oxygen depletion in ice-covered lakes. Conventional aeration by air bubble plumes and other techniques usually mixes the water column and produces hazardous open water in the ice cover. A non-mixing winter lake aeration system which creates a fish refuge was designed and field tested to oxygenate the water and maintain water temperature stratification in a lake such that no open water is created. The system uses a cascade aerator and has a design discharge and dissolved oxygen input rate of 85 1/s and 70 kg/d, respectively. Aerated water is discharged near mid-depth with minimum disturbance of the ambient water through a specially designed diffuser. The system was tested in a shallow 3 m deep lake of 17 ha surface area during two winters and was found to perform as expected. Significant photosynthetic production of dissolved oxygen under the ice-cover was also observed during snow-free periods.