Hanson-Doyle Lake
Flathead County, MontanaView mapDirections
Nutrients and algae sit mid-range for this region.
↓ down from A at the last regrade
- Mesotrophic
- #26 of 44 in the county
Hanson-Doyle Lake in Flathead County, Montana has a water quality grade of C (Fair). Phosphorus: 7.3 µg/L. Chlorophyll-a (algae): 2.3 µg/L.
- Type
- Mesotrophic
- Phosphorus
- 7.3 µg/L
- Chlorophyll-a
- 2.3 µg/L
- Trend
- ↓ Declining
Stays via Stay22
Stays near Hanson-Doyle Lake
Compare lakeside cabins, hotels, and vacation rentals near Hanson-Doyle Lake in Flathead 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 Hanson-Doyle 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 Hanson-Doyle Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Hanson-Doyle Lake is a mesotrophic lake in Flathead County, Montana. Water quality is graded C based on 3 sampling years through 2023. Overall water quality is declining over recent sampling years. Compared to the 43 other monitored lakes in Flathead County, Hanson-Doyle Lake ranks #26 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-08-08. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyModerate
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 C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Phosphorus 7.3 µg/L. Chlorophyll-a 2.3 µg/L. TSI 36. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 7.3 µg/L | Good |
| Chlorophyll-a (Algae) | 2.3 µg/L | Fair |
| Trophic State Index (TSI) | 36 | Mesotrophic |
Moderate nutrients, good water quality
Fishing Hanson-Doyle Lake
Water Quality Trend: ↓ Declining
Based on 12 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.659 m/yr | 3 |
| Phosphorus | ↓ Declining | +0.23 µg/L/yr | 11 |
| Chlorophyll-a | → Stable | +0.02 µg/L/yr | 12 |
County Ranking
Ranked #26 of 44 lakes in Flathead County
Nearby Lakes in Flathead County
Frequently asked questions about Hanson-Doyle Lake
Where is Hanson-Doyle Lake?
- Hanson-Doyle Lake is a lake in Flathead County, Montana. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Hanson-Doyle Lake?
- Hanson-Doyle Lake in Flathead County, Montana has a water quality grade of C (Fair). Phosphorus: 7.3 µg/L. Chlorophyll-a (algae): 2.3 µg/L.
Is Hanson-Doyle Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Hanson-Doyle Lake across LakeQuality
Planning a trip around Glacier?
Hanson-Doyle Lake is about 38 miles from Glacier National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Glacier →More Montana Lake Rankings
Other Grade C Lakes in Montana
Mesotrophic Lakes in Montana
Where this data comes from
26 measurements from 1 monitoring station, 2012–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana Watershed
MTWTRSHD_WQX26 samples · 2012–2023
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.