DNR Lake ID Number: 70-005000 Surface Area: 162.26 acres Littoral Area: 157.93 acres Lake Watershed Area: 393 acres Maximum Depth: 14 feet Mean Depth: 8.5 feet Ordinary High Water Level: 965.2 feet above sea level Public Boat Access: One DNR public access is available off Mushtown Rd/C.R. 87 Water Quality Impairment Status: Impaired for nutrients and mercury. The completed nutrient TMDL can be reviewed here.
High water no wake restrictions: When the lake level exceeds 965.2 feet NVGD 29
McMahon Lake was removed from the Federal Impaired Waters List (303d List) in 2018 due to improvements in water quality. State standards for shallow lakes in the North Central Hardwood Forest (NCHF) region for the three lake parameters we track are provided in the following table. If a parameter meets for falls below that standard unit, that parameter is meeting water quality standards.
State Standards for Shallow Lakes in the North Central Hardwood Forest Ecoregion
Secchi Disk Transparency
Greater than 1m
Additional water quality reports and information can be found in Annual Reports.
Water Quality 2005-2021
McMahon lake currently as two aquatic invasive species, Curlyleaf pondweed and Eurasian watermilfoil. The Scott WMO treats the public access bay for curlyleaf pondweed each year as a preventive measure of spreading it to other lakes.