WATER TRANSPORT STUDIES IN THE STRAITS OF MACKINAC REGION OF LAKE HURON1

The Straits of Mackinac comprise five simple straits in the region embracing Mackinac Island, Round Island, Bois Blanc Island, and the adjacent portions of the Upper and Lower Peninsulas of Michigan. Here the inflows from Lakes Michigan and Superior enter Lake Huron. Direct assessments of the inflow from Lake Michigan and of the run‐off from the Lake Huron watershed, hitherto obtainable only by indirect means, have been made. The study indicates that large volumes of water move horizontally in oscillatory motion, due to the action of the Lake Michigan—Lake Huron uninodal seiche, but that this motion has no net effect upon the flow‐through of waters from the upper lakes through Lake Huron. The excess of oscillatory transport over net flow‐through indicates the seiche has an amplitude of about 0.1 m, a value which is independently confirmed by data from the literature.