Junior Lake
Junior Lake in Penobscot County, Maine has a water quality grade of A (Excellent). Water clarity: 25.9 ft visibility. Phosphorus: 6 µg/L. Chlorophyll-a (algae): 2 µg/L.
- Clarity
- 25.9 ft
- Type
- Oligotrophic
- Trend
- ↑ Improving
Junior Lake is a cold, clear oligotrophic lake in Penobscot County, Maine. Water quality is graded A based on 2 sampling years through 2022. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2022-08-01. Grade methodology: LakeGrade methodology.
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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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 25.9 ft down. Phosphorus level: 6 µg/L. Chlorophyll-a: 2 µg/L. Trophic State Index: 33.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 25.9 ft | Not graded |
| Phosphorus | 6 µg/L | Good |
| Chlorophyll-a (Algae) | 2 µg/L | Good |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Junior Lake
Compare lakeside cabins, hotels, and vacation rentals near Junior Lake in Penobscot County, Maine — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Fishing Junior Lake
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.525 m/yr | 3 |
| Phosphorus | ↓ Declining | +0.5 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -0.25 µg/L/yr | 3 |
County Ranking
Ranked #1 of 1 lakes in Penobscot County
Nearby Lakes in Penobscot County
Frequently asked questions about Junior Lake
What is the water quality grade for Junior Lake?
- Junior Lake in Penobscot County, Maine has a water quality grade of A (Excellent). Water clarity: 25.9 ft visibility. Phosphorus: 6 µg/L. Chlorophyll-a (algae): 2 µg/L.
Is Junior Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Junior Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2 µg/L. Always check local health department advisories before swimming.
Explore Junior Lake across LakeGrade
More Maine Lake Rankings
Other Grade A Lakes in Maine
Oligotrophic Lakes in Maine
Where this data comes from
37 measurements from 1 monitoring station, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples37 samples · 2020–2022
Monitoring station identifiers (1)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Data Sources
Water quality data from the EPA Water Quality Portal
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2022-08-01
Monitoring stations: 1