Big Maggie Lake; Mastodon Township is a mesotrophic lake in Iron County, Michigan. Water quality is graded A based on 2 sampling years through 2023. Water clarity is improving over recent sampling years. Compared to the 38 other monitored lakes in Iron County, Big Maggie Lake; Mastodon Township ranks #22 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2023-08-27. Grade methodology: LakeGrade methodology.
Watch Big Maggie Lake; Mastodon Township water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 11 ft. Chlorophyll-a: 3.1 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 3.1 µg/L | A |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Big Maggie Lake; Mastodon Township
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Top-rated places to stay near Big Maggie Lake; Mastodon Township
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Fishing Big Maggie Lake; Mastodon Township
Water Quality Trend: → Stable
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +8.17 m/yr | 2 |
| Chlorophyll-a | ↓ Declining | +2.3 µg/L/yr | 3 |
Water Temperature
Big Maggie Lake; Mastodon Township averages about 64°F at the surface in summer, usually warmest in Aug (about 67°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 36 field readings (2016–2016) via the EPA Water Quality Portal. See the full Big Maggie Lake; Mastodon Township water temperature breakdown →
Location
County Ranking
Ranked #22 of 39 lakes in Iron County
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Moderate nutrients, good water quality
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Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-08-27
Monitoring stations: 1