Big Birch Lake

On the LakeGrade scale Big Birch Lake grades a B, with clarity at 13.0 ft and 25 µg/L of phosphorus placing it above the Minnesota median. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Mesotrophic conditions dominate at Big Birch Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. At 81 ft of maximum depth, Big Birch Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. Big Birch Lake covers 2,107 acres alongside 15.3 miles of shoreline, large enough that conditions can vary meaningfully between bays. Among the 17 graded lakes in Todd County, Big Birch Lake ranks 3 — in the top quartile locally.

Big Birch 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 Birch Lake, one of 18 fish species on record for the lake. A documented public access point at Big Birch Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been logged at Big Birch Lake more than two dozen times, putting the median around Apr 13 — a useful baseline for tracking climate trends. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.