AN EMPIRICAL-METHOD FOR THE PREDICTION OF DAILY WATER TEMPERATURES INTHE LITTORAL-ZONE OF TEMPERATE LAKES

We used daily air and water temperatures from 14 lakes in Ontario to d evelop and test a simple method for constructing lake-specific empiric al models for predicting daily littoral water temperatures. Data requi rements for prediction are modest (average air temperature, day of the year) and the method is robust and practical, requiring only a few (1 5-20) well-spaced water temperature observations to construct a single -year model that can generate reasonably accurate predictions for an e ntire ice-free season. The ability of a singe-lake model to predict se veral years of temperature data is significantly improved by explicitl y including information on ice-out date in the model. Our multiyear mo del for Lake Opeongo described most (18 of 22) years well. Years that were not well described were usually coincident with El Nino Southern Oscillation events. Used with caution, the method can be an effective tool for supplementing direct monitoring of littoral water temperature s and for generating historical water temperature estimates when direc t estimates are lacking. These capabilities should be of particular us e to fisheries biologists studying or managing populations of fish spe cies with critical life stages that are affected by littoral water tem peratures.