Tally Lake
Flathead County, MontanaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #1 of 44 in the county
Tally Lake in Flathead County, Montana has a water quality grade of A (Excellent). Water clarity: 15.2 ft visibility. Phosphorus: 4.7 µg/L. Chlorophyll-a (algae): 0.8 µg/L.
- Clarity
- 15.2 ft
- Type
- Oligotrophic
- Phosphorus
- 4.7 µg/L
- Chlorophyll-a
- 0.8 µg/L
- Trend
- ↓ Declining
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Stays near Tally Lake
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Watch Tally Lake’s letter
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Tally Lake is a cold, clear oligotrophic lake in Flathead County, Montana. Water quality is graded A 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, Tally Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-08-15. Grade methodology: LakeQuality methodology.
What Tally Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.2 ft of visibility
- Camping1 public campground nearby
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)
Crystal clear, you can see 15.2 ft down. Phosphorus 4.7 µg/L. Chlorophyll-a 0.8 µg/L. TSI 31. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.2 ft | Not graded |
| Phosphorus | 4.7 µg/L | Good |
| Chlorophyll-a (Algae) | 0.8 µg/L | Good |
| Trophic State Index (TSI) | 31 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Recreation & Access
Public campgrounds near Tally Lake
- Tally Lake Campground2.3 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Fishing Tally Lake
Water Quality Trend: ↓ Declining
Based on 12 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -1.006 m/yr | 9 |
| Phosphorus | → Stable | +0.04 µg/L/yr | 12 |
| Chlorophyll-a | ↓ Declining | +0.09 µg/L/yr | 12 |
County Ranking
Ranked #1 of 44 lakes in Flathead County
Nearby Lakes in Flathead County
Frequently asked questions about Tally Lake
Where is Tally Lake?
- Tally Lake is a lake in Flathead County, Montana. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Tally Lake?
- Tally Lake in Flathead County, Montana has a water quality grade of A (Excellent). Water clarity: 15.2 ft visibility. Phosphorus: 4.7 µg/L. Chlorophyll-a (algae): 0.8 µg/L.
Is Tally Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Are there campgrounds on Tally Lake?
- Tally Lake has 1 public campground from USGS The National Map within 5 km, including Tally Lake Campground. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Tally 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
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Other Grade A Lakes in Montana
Oligotrophic Lakes in Montana
Where this data comes from
54 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_WQX54 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.
Other records on this page
Public campgrounds from USGS The National Map Structures, within about 3 miles