Alva Lake
Missoula County, MontanaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #5 of 40 in the county
Alva Lake in Missoula County, Montana has a water quality grade of A (Excellent). Phosphorus: 4.7 µg/L. Chlorophyll-a (algae): 0.7 µg/L.
- Type
- Oligotrophic
- Phosphorus
- 4.7 µg/L
- Chlorophyll-a
- 0.7 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Alva Lake
Compare lakeside cabins, hotels, and vacation rentals near Alva Lake in Missoula County, Montana — 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.
Top-rated places to stay near Alva Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Montana’s top lakes →
Watch Alva Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Alva Lake is a cold, clear oligotrophic lake in Missoula County, Montana. Water quality is graded A based on 3 sampling years through 2025. Overall water quality is improving over recent sampling years. Compared to the 39 other monitored lakes in Missoula County, Alva Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2025-09-18. Grade methodology: LakeQuality methodology.
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)
No clarity data. Phosphorus 4.7 µg/L. Chlorophyll-a 0.7 µg/L. TSI 27. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 4.7 µg/L | Good |
| Chlorophyll-a (Algae) | 0.7 µg/L | Good |
| Trophic State Index (TSI) | 27 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Fishing Alva Lake
Water Quality Trend: ↑ Improving
Based on 12 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.046 m/yr | 8 |
| Phosphorus | → Stable | +0.11 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -0.4 µg/L/yr | 2 |
County Ranking
Ranked #5 of 40 lakes in Missoula County
Nearby Lakes in Missoula County
Frequently asked questions about Alva Lake
Where is Alva Lake?
- Alva Lake is a lake in Missoula County, Montana. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Alva Lake?
- Alva Lake in Missoula County, Montana has a water quality grade of A (Excellent). Phosphorus: 4.7 µg/L. Chlorophyll-a (algae): 0.7 µg/L.
Is Alva Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Alva 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.
Montana's cleanest and most-polluted lakes, ranked
More Montana Lake Rankings
Other Grade A Lakes in Montana
Oligotrophic Lakes in Montana
Where this data comes from
27 measurements from 1 monitoring station, 2023–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana Volunteer Water Quality Monitoring
MTVOLWQM_WQX27 samples · 2023–2025
Analytical methods
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 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.