Big Maggie Lake
Iron County, MichiganView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #6 of 21 in the county
Big Maggie Lake in Iron County, Michigan has a water quality grade of A (Excellent). Water clarity: 11.5 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 1.4 µg/L.
- Clarity
- 11.5 ft
- Typical in August
- 67°F
- Type
- Oligotrophic
- Phosphorus
- 10 µg/L
- Chlorophyll-a
- 1.4 µg/L
- Trend
- ↑ Improving
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Big Maggie Lake is a cold, clear oligotrophic lake in Iron County, Michigan. Water quality is graded A based on 2 sampling years through 2023. Overall water quality is improving over recent sampling years. Compared to the 20 other monitored lakes in Iron County, Big Maggie Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2023-08-27. Grade methodology: LakeQuality methodology.
What Big Maggie Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.5 ft of visibility
Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Good clarity, visible to about 11.5 ft. Phosphorus 10 µg/L. Chlorophyll-a 1.4 µg/L. TSI 38. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.5 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | 1.4 µg/L | Good |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Water Temperature
Big Maggie Lake typically sits around 67°F at the surface in August. Summer average is about 64°F. 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 water temperature breakdown →
Fishing Big Maggie Lake
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.983 m/yr | 5 |
| Phosphorus | ↑ Improving | -0.96 µg/L/yr | 7 |
| Chlorophyll-a | → Stable | -0.09 µg/L/yr | 7 |
County Ranking
Ranked #6 of 21 lakes in Iron County
Nearby Lakes in Iron County
Frequently asked questions about Big Maggie Lake
Where is Big Maggie Lake?
- Big Maggie Lake is a lake in Iron County, Michigan. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Big Maggie Lake?
- Big Maggie Lake in Iron County, Michigan has a water quality grade of A (Excellent). Water clarity: 11.5 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 1.4 µg/L.
Is Big Maggie Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Big Maggie Lake?
- Big Maggie Lake typically sits around 67°F at the surface in August, from 36 EPA Water Quality Portal field readings (2016–2016). That is a typical value for the month, not a live reading.
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Low nutrients, clear water. The letter is not a swimming clearance.
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Where this data comes from
77 measurements from 1 monitoring station, 2016–2023. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS77 samples · 2016–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.