ANALYSIS OF WATER LEVEL FLUCTUATIONS IN THE GREAT NORTH AMERICAN LAKES
The analysis of long-term water level change data in the North American Great lakes (Upper, Michigan, Huron, St. Clair, Erie and Ontario) was performed by the Fourier transform method for the observation over hundred years time interval. It was found that there are intra-annual cycles with periods of 3, 4, 6 and 12 months in the dynamics of relative changes of the lake water volumes for the month ∆V/V. The smaller water volume or average depth of the lakes are, the greater amplitude of the annual water levels harmonic of the Great lakes is.