Forecasting the levels of the Great Lakes

A description is given of the U.S. Lake Survey method of forecasting Great Lakes water levels. The method, in general, consists of determining a level for each month of a 6‐month forecast period on each of the Great Lakes by routing a predicted volume of water (Net Basin Supply) to each of the Great Lakes basins. The technique employed in prediction of the volume of the water consists of using multiple linear regressions based upon U.S. Weather Bureau precipitation and temperature data as predictors for the first month and trend predictors for the second through the sixth month. This technique results in forecasting of lake levels on the average from 15 to 40% closer to the recorded lake levels, in comparison with the technique that utilizes the long‐term average volume of water as the basis of projection. (Key words: Forecasting; water supply; Great Lakes)