There are 34 primary river systems in Michigan that have watersheds of 250 square miles or more, and 9 secondary river systems that have watersheds of 500 square miles or more. The mean annual discharge rates of the trunk rivers of these systems range from a minimum of about 0.60 to a maximum of about 1.35 cubic feet per second per square mile of watershed. The regimen of Michigan streams is remarkably uniform in comparison with that of streams in many other parts of the country. This characteristic is favorable to the utilization of stream flow for practically all purposes. The qualities of...