Spruce Lake
Carlton County, MinnesotaEutrophic
Spruce Lake sits at a C on the grading scale — not impaired, not pristine, with summer measurements that vary year to year. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Spruce Lake ranks 14 of 33 in Carlton County — solidly in the upper half of the local distribution.
No invasive species are currently listed at Spruce Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Spruce Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Spruce Lake — most use is by shoreline residents and their guests. Multiple sampling years from Minnesota PCA volunteers and partner agencies back the grade, so the letter should hold steady absent a major watershed shift.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-07-08. Grade methodology: LakeGrade methodology.
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Very murky, less than 2.3 ft of visibility. Phosphorus level: 19 µg/L. Chlorophyll-a: 9.1 µg/L. Trophic State Index: 55.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.3 ft | F |
| Phosphorus | 19 µg/L | A |
| Chlorophyll-a (Algae) | 9.1 µg/L | B |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.453 m/yr | 5 |
| Phosphorus | ↓ Declining | +2 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.46 µg/L/yr | 5 |
Location
County Ranking
Ranked #14 of 33 lakes in Carlton County
Cleaner Lakes Within 30 Miles
Spruce Lake holds Grade C. 2 nearby lakes hold higher grades.
- BLac LakeCarlton County · mi · Higher grade (C → B)
- BSofie LakeCarlton County · mi · Higher grade (C → B)
Nearby Lakes in Carlton County
More Minnesota Lake Rankings
State Parks Near Spruce Lake
Other Grade C Lakes in Minnesota
Eutrophic Lakes in Minnesota
EPA Impairment Status
Spruce Lake is officially listed as impaired under Clean Water Act §303(d) in the 2019 EPA reporting cycle.
Causes of impairment
Source: EPA ATTAINS assessment unit FDL_121 · Official waterbody report · Matched by proximity (0 km)
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-07-08
Monitoring stations: 1