Clearwater River Lake
Missoula County, MontanaView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↓ down from A at the last regrade
- Oligotrophic
- #19 of 40 in the county
- Limited data
Clearwater River Lake in Missoula County, Montana has a water quality grade of B (Good). Phosphorus: 12 µg/L.
- Type
- Oligotrophic
- Phosphorus
- 12 µg/L
- Trend
- ↓ Declining
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Watch Clearwater River Lake’s letter
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Clearwater River Lake is a cold, clear oligotrophic lake in Missoula County, Montana. Water quality is graded B based on 2 sampling years through 2022. Overall water quality is declining over recent sampling years. Compared to the 39 other monitored lakes in Missoula County, Clearwater River Lake ranks #19 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2022-09-20. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
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 B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
No clarity data. Phosphorus 12 µg/L. TSI 40. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 40 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Fishing Clearwater River Lake
Water Quality Trend: ↓ Declining
Based on 13 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.095 m/yr | 8 |
| Phosphorus | ↓ Declining | +0.51 µg/L/yr | 5 |
| Chlorophyll-a | → Stable | 0 µg/L/yr | 2 |
County Ranking
Ranked #19 of 40 lakes in Missoula County
Nearby Lakes in Missoula County
Frequently asked questions about Clearwater River Lake
Where is Clearwater River Lake?
- Clearwater River Lake is a lake in Missoula County, Montana. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Clearwater River Lake?
- Clearwater River Lake in Missoula County, Montana has a water quality grade of B (Good). Phosphorus: 12 µg/L.
Is Clearwater River Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Clearwater River Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Montana's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
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Other Grade B Lakes in Montana
Oligotrophic Lakes in Montana
Where this data comes from
8 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana Volunteer Water Quality Monitoring
MTVOLWQM_WQX8 samples · 2022
Analytical methods
- Phosphorus by Colorimetry
- 4500 N C ~ Persufate Method for Total Nitrogen
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.