Topaz Lake

On the LakeGrade rubric, Topaz Lake pulls an A: clarity at 17.5 ft and phosphorus readings still being added put it in the top bracket for Minnesota. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. Topaz Lake is unusually deep for Minnesota at 110 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Topaz Lake covers 410 acres alongside 10.1 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Among the 142 graded lakes in Lake County, Topaz Lake ranks 19 — in the top quartile locally.

No invasive species are currently listed at Topaz Lake — the lake remains off the Minnesota infested-waters roster. Bass fishing is part of the appeal: the species list runs to 4, anchored by largemouth and/or smallmouth bass. The lake lacks a documented public access point, so visitor use is limited. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.