Pat Martin Lake
Carlton County, MinnesotaMesotrophic
Pat Martin Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.
A TSI near 45 places Pat Martin Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. 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. Among the 33 graded lakes in Carlton County, Pat Martin Lake ranks 3 — in the top quartile locally.
Pat Martin Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Pat Martin Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Pat Martin 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 2024-10-03. Grade methodology: LakeGrade methodology.
Track Pat Martin Lake
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Murky, only visible to about 6.6 ft. Phosphorus level: 15 µg/L. Chlorophyll-a: 3.5 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.6 ft | C |
| Phosphorus | 15 µg/L | A |
| Chlorophyll-a (Algae) | 3.5 µg/L | A |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1.123 m/yr | 5 |
| Phosphorus | ↓ Declining | +2 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.47 µg/L/yr | 5 |
Location
County Ranking
Ranked #3 of 33 lakes in Carlton County
Nearby Lakes in Carlton County
More Minnesota Lake Rankings
State Parks Near Pat Martin Lake
Other Grade B Lakes in Minnesota
Mesotrophic Lakes in Minnesota
EPA Impairment Status
Pat Martin 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_113 · Official waterbody report
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: 2024-10-03
Monitoring stations: 1