Smith Lake
Flathead County, Montana17 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- #9 of 44 in the county
- Limited data
Smith Lake in Flathead County, Montana has a water quality grade of A (Excellent). Phosphorus: 7.4 µg/L. Chlorophyll-a (algae): 0.8 µg/L. Surface area: 17.3 acres.
- Area
- 17 acres
- Type
- Oligotrophic
- Phosphorus
- 7.4 µg/L
- Chlorophyll-a
- 0.8 µg/L
- Trend
- ↓ Declining
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Watch Smith Lake’s letter
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Smith Lake is a 17-acre 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, Smith Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-08-08. 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 A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
No clarity data. Phosphorus 7.4 µg/L. Chlorophyll-a 0.8 µg/L. TSI 31. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 7.4 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.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 17 acres |
No bathymetric survey has been published for Smith Lake, so its depth is not documented here.
Fishing Smith Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↓ Declining | +0.3 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.34 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Smith Lake is a man-made reservoir impounded by the Smith Lake Dam (completed 1938), built primarily for fish and wildlife pond on the Smith Creek; earth-type dam, 12 ft tall and 150 ft long.
- Surface area
- 17.3 ac
- Normal storage
- 95 ac-ft
- Max storage
- 131 ac-ft
- Drainage area
- 2.6 sq mi
- Hazard class
- High
- Owner
- STATE OF MONTANA, D.N.R.C., T.L.M.D.
Source: USACE National Inventory of Dams, NID ID MT03845 · Operator website
County Ranking
Ranked #9 of 44 lakes in Flathead County
Nearby Lakes in Flathead County
Frequently asked questions about Smith Lake
Where is Smith Lake?
- Smith 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 Smith Lake?
- Smith Lake in Flathead County, Montana has a water quality grade of A (Excellent). Phosphorus: 7.4 µg/L. Chlorophyll-a (algae): 0.8 µg/L. Surface area: 17.3 acres.
Is Smith Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Smith 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
Planning a trip around Glacier?
Smith Lake is about 31 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 A Lakes in Montana
Oligotrophic Lakes in Montana
Where this data comes from
14 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_WQX14 samples · 2012–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 10200 H ~ Chlorophyll a-b-c Determination
- 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.