Observations of Cooling Water Discharge Effects on Ice Covers and Dissolved Oxygen Levels in Selected Minnesota Streams and Lakes

The impact of cooling water discharges from power generating plants on aquatic environments is usually evaluated and documented for summer conditions. Only a very few studies have dealt with the modification of winter conditions in rivers and lakes by thermal additions. This reflects the defensive approach toward the evaluation of heat addition to streams, rivers, lakes, and estuaries. Preoccupation with the negative effects of heat addition has been so pervasive that the possible benefits from heat addition to streams and lakes in cold regions have been vastly ignored.Electric Utilities Group (Northern States Power Company, Minnesota Power and Light Company, Ottertail Power Company, and Interstate Power Company