Impact of Cooling Water on Lake Temperatures

The impact of cooling water discharge from A.S. King plant on water temperatures in Lake St. Croix during the summer of 1969 is evaluated in terms of overall effects. The information supplements previous studies of local temperature increments in the thermal plume. The method used is generally applicable and puts into focus the alteration of the elements of a natural heat budget by power plant effluents as well as illustrating some of the trade-offs between natural and artificial heat inputs and resultant temperature changes. Caution must be exerted when ambient temperatures are used to represent natural ones. The main objective was to demonstrate the applicability of the heat budget method to predict alterations of natural water temperatures caused by cooling water discharges. The particular numerical results obtained show no significant impact of cooling water discharges on water temperatures at the chosen demonstration site for the period of investigation.