Au Sable River (Michigan)

Au Sable River (Michigan). The Au Sable River is a major river system in the northern Lower Peninsula of Michigan, flowing approximately 138 miles from its headwaters near Gaylord to its mouth at Lake Huron in Oscoda. Renowned for its pristine water quality and exceptional fly fishing, the river drains a large watershed encompassing parts of Otsego, Crawford, Roscommon, Iosco, and Alcona counties. Its name, derived from French for "with sand," reflects the river's sandy substrate, and it is a central feature of the Huron-Manistee National Forests and a designated National Wild and Scenic River.

Course and tributaries

The main branch originates from numerous small lakes and wetlands southwest of Gaylord in Otsego County. It flows generally eastward, passing through the communities of Grayling and Mio, where it is impounded to form Mio Pond behind Mio Dam. Major tributaries joining the main stem include the East Branch and South Branch near McKinley, the Manistee River (via the Canoe Marathon State Waterway), and the Rifle River. Downstream of Alcona Dam, the river enters the Au Sable State Forest and broadens significantly before emptying into Lake Huron at Van Etten Lake and then Oscoda.

Hydrology and watershed

The river's hydrology is characterized by stable, cold flows fed by groundwater from the extensive Michigan Basin aquifer and numerous springs, maintaining water temperatures ideal for brook trout. The watershed covers nearly 2,000 square miles of largely forested land within the Huron-Manistee National Forests. Key flow regulation comes from a series of hydroelectric dams operated by Consumers Energy, including the Mio Dam, Alcona Dam, and Five Channels Dam. The river's average discharge of over 1,000 cubic feet per second makes it one of Michigan's largest rivers by volume, with significant contributions from the Holy Waters stretch below Grayling.

Natural history and ecology

The river corridor supports a diverse ecosystem, most famously a world-class fishery for naturally reproducing brook trout, brown trout, and rainbow trout. The surrounding forests, part of the Northern Michigan transition zone, contain stands of red pine, eastern white pine, and northern hardwoods. The watershed provides critical habitat for bald eagle, osprey, common loon, and piping plover, as well as mammals like white-tailed deer and North American river otter. Conservation efforts by the Michigan Department of Natural Resources and groups like Trout Unlimited focus on protecting insect hatches, controlling sea lamprey, and preserving riparian zones.

Recreation and conservation

The Au Sable is a premier destination for fly fishing, canoeing, and kayaking, hosting the renowned Au Sable River Canoe Marathon each July. Extensive public access is provided through state forest campgrounds, Michigan Department of Natural Resources sites, and the Au Sable River Queen tour boat. Large portions are protected within the Au Sable State Forest and the federal National Wild and Scenic River system, managed by the United States Forest Service. Major conservation initiatives are led by the Au Sable River Watershed Restoration Committee, The Nature Conservancy, and the Anglers of the Au Sable, focusing on dam relicensing, habitat restoration, and opposing projects like the Kalkaska groundwater extraction proposal.

History and human use

The river valley was historically inhabited by the Ojibwe and Ottawa peoples before European exploration by French voyageurs in the 18th century. The 19th-century Michigan logging era saw the river used extensively to transport white pine logs to sawmills in Oscoda and Au Sable, facilitated by the Au Sable River Boom Company. The arrival of the Jackson, Lansing and Saginaw Railroad spurred tourism, leading to the establishment of the Grayling Fish Hatchery and popular clubs like the Au Sable River Club. The river's hydroelectric potential was harnessed in the early 20th century by predecessors of Consumers Energy, and its environmental significance was nationally recognized with its 1984 designation as a National Wild and Scenic River. Category:Rivers of Michigan Category:National Wild and Scenic Rivers