Spring Lake

The LakeGrade rubric puts Spring Lake at a C: clarity at 9.5 ft, phosphorus readings still being added, and a TSI of 45 signal an intermediate trophic state. 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.

Mesotrophic conditions dominate at Spring Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. A maximum depth of 25 ft puts Spring Lake in the middle of Minnesota's depth distribution. The lake is compact at 98 acres, with 2.9 miles of shoreline and little volume to buffer nutrient inputs. Within St. Louis County's 187 graded lakes, Spring Lake ranks 108 — below the local median, though not at the bottom.

No invasive species are currently listed at Spring Lake — the lake remains off the Minnesota infested-waters roster. The fishery includes walleye alongside the lake's other 8 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.