The surface area of Lake Michigan is 22394 square miles according to Google, which converts to 8.99e13 square inches. If you're only looking for one inch of dep

The surface area of Lake Michigan is 22394 square miles according to Google, which converts to 8.99e13 square inches. If you're only looking for one inch of depth, that is 8.99e13 cubic inches. Each cubic inch is 0.00433 gallons, so the first inch of Lake Michigan is 389,267,000,000 gallons. Divide by the loss per day, in this case assuming they're consuming the entire 7 million gallons, and it will take 55609.6 days, or 152 years and change for Lake Michigan to lose 1 inch excluding other sources of loss or addition and so on.