Thumb Lake, also known as Lake Louise by the “Lake Louise Camp” community, is a kettle lake located in Hudson Township, Charlevoix County, Michigan. The epithet Thumb Lake derives from the lake’s bathymetry. An islet protrudes from the lake’s west basin. The total surface area of the lake is 485 acres, with maximum depths of 152 feet.
Thumb Lake is one of the most popular fishing lakes in Michigan. The lake is nestled in the highlands east of the village of Boyne Falls, centered at 45°11′N 84°45′W, and is surrounded by wooded hills. Because of its depth and the dearth of run-off into the lake, its waters are exceptionally clear. The lake is inhabited by splake, a stocked hybrid species lake trout and brook trout, rainbow trout, yellow perch, bluegill, rock bass, black crappie, smallmouth bass, northern pike, largemouth bass, smelt. Public access is available on the eastern shore of the lake in the form of a park with swimming beach, and on the southwestern shore in the form of a boat launch.
Thumb Lake is a glacially formed kettle lake that sits in the headwaters of the Sturgeon River. There are a few minor inlets and no outlet streams. Due to the lack of an outlet, Thumb Lake is considered a seepage lake. Seepage lakes lose water only through evaporation and groundwater channels, which means that lake water has a long residence time in relation to drainage lakes (lakes with outlets). If Thumb Lake were to become seriously polluted, natural recovery would be slow because there are no outlet streams to flush out the pollutants.
The Thumb Lake watershed is a sub-watershed of the Sturgeon River watershed, which is, in turn, part of the larger Cheboygan River Watershed. Thumb Lake has a small watershed in relation to the lake’s surface area, measuring approximately 3,840 acres (does not include lake area). According to land cover statistics from a 2006 land cover dataset, the majority of the watershed is forested. Of land cover types that typically contribute to water quality degradation, there is little agriculture and even less urban/residential in the watershed.