Big Carnelian Lake

Big Carnelian Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Trophically, Big Carnelian Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. The lake's 66 ft maximum depth is in the upper tier for Minnesota — deep enough for cold-water fish to find refuge in summer. Big Carnelian Lake covers 457 acres alongside 5.1 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Among the 31 graded lakes in Washington County, Big Carnelian Lake ranks 7 — in the top quartile locally.

Big Carnelian Lake is on the Minnesota infested-waters list for zebra mussels — boaters should follow clean-drain-dry protocols when moving gear to or from the lake. Walleye are documented at Big Carnelian Lake, one of 12 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been recorded 23 times at Big Carnelian Lake, with a median around Apr 9. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.