Estimated rates of direct ground-water discharge to Lake Michigan range from 800 to 6,700 cubic feet per second. Highest rates are calculated for the northeastern shore of the lake. Using generalized values, total direct ground-water discharge to Lake Michigan was estimated to be about 2,700 cubic feet per second. Insufficient data are available to make similar estimates for the remaining Great Lakes (Huron, Superior, Erie, and Ontario), but estimated rates from six studies are much smaller than those from studies for Lake Michigan.