Swan Lake

Swan Lake is a shallow prairie lake in southern Nicollet County, Minnesota, near the town of Nicollet. The Minnesota Department of Natural Resources (DNR) calls it the largest prairie pothole wetland in the United States and gives its average depth as less than 4 feet. Local press reports put its size at about 10,000 acres, though one 2016 article gave 8,800 acres. The basin was left by retreating glaciers about 11,000 years ago. Before it was partly drained for farming in the late 19th and early 20th centuries, the lake was roughly twice its present size. Outlet control structures were installed in the 1950s. The DNR controls the water level with a board dam on a drainage ditch at the south end of the lake and has used it for planned drawdowns, including one that began in 2020. The lake and nearby marshes make up the Swan Lake State Wildlife Management Area.

The DNR describes two developed watercraft accesses, one at Poor Farm Bay on the north end and one at Nicollet Bay on the south side. A third, undeveloped carry-in access near Courtland Bay in the northwest is hard to use when the water is low. Motorboats are allowed, but most boaters use small motors or mud motors because the water is shallow and full of submerged plants. Swan Lake is a designated wildlife management lake, so airboats are banned at all times. Johnson Island and Anderson Island, in the Loon Bay waterfowl refuge, are closed to the public, and most of the shoreline is private. In the low water of 2021, the DNR warned that launching at its three landings could be difficult or impossible.

The Dakota name for the lake is Marrah Tanka, meaning swan, and trumpeter swans nest there. After restoration work, the lake went from producing 24 ducks a year to an estimated 8,000 by 2001.