Big Lake

Big Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Sherburne County. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

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. A maximum depth of 48 ft puts Big Lake in the middle of Minnesota's depth distribution. The lake's 254 acres and 2.4 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Big Lake ranks 1 of 24 in Sherburne County, putting it in the upper tier of locally monitored lakes.

Zebra mussels have been documented at Big Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The fishery includes walleye alongside the lake's other 14 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been recorded 20 times at Big Lake, with a median around Apr 7. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.