Ashley Lake
Flathead County, Montana2,852 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Public access
- Limited data
Ashley Lake in Flathead County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 33.1 ft visibility. Surface area: 2852 acres.
- Clarity
- 33.1 ft
- Area
- 2,852 acres
- Trend
- ↓ Declining
- Public access
- Yes
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Watch Ashley Lake’s letter
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Why Ashley Lake has no grade
Ashley Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Ashley Lake is Not Rated — not an F. Its 33.1-foot median from 10 readings collected 2020–2023 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Montana DEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Ashley Lake is a 2,852-acre lake in Flathead County, Montana. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-09-16. Grade methodology: LakeQuality methodology.
What Ashley Lake is good for
From access and monitoring records, not editorial picks.
- Clear water33.1 ft of visibility
- Boat launch1 documented ramp
- Big water2,852 acres
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Ashley Lake
These readings exist but are not enough for an A–F grade — see why.
Crystal clear, you can see 33.1 ft down. TSI 27.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 33.1 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 27 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 2,852 acres |
| Public Access | Yes |
No bathymetric survey has been published for Ashley Lake, so its depth is not documented here.
Recreation & Access
- Ashley LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Ashley Lake
Water Quality Trend: ↓ Declining
Based on 12 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.027 m/yr | 4 |
| Phosphorus | ↓ Declining | +0.48 µg/L/yr | 12 |
| Chlorophyll-a | → Stable | 0 µg/L/yr | 12 |
Reservoir Info (USACE NID)
Ashley Lake is a man-made reservoir impounded by the Ashley (completed 1928), built primarily for irrigation on the Ashley Creek; earth-type dam, 10 ft tall and 20 ft long.
- Surface area
- 2,852 ac
- Normal storage
- 20,400 ac-ft
- Max storage
- 27,600 ac-ft
- Hazard class
- Low
- Owner
- STATE OF MONTANA, D.F.W.P.
Source: USACE National Inventory of Dams, NID ID MT01163 · Operator website
Graded lakes near Ashley Lake
Ashley Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Flathead County
Frequently asked questions about Ashley Lake
Where is Ashley Lake?
- Ashley Lake is a lake in Flathead County, Montana. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Ashley Lake?
- Ashley Lake in Flathead County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 33.1 ft visibility. Surface area: 2852 acres.
Is Ashley Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Ashley Lake?
- Ashley Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Ashley Lake. Public access is listed as yes.
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Where this data comes from
10 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North American Lake Management Society
NALMS10 samples · 2020–2023
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
Named boat-access points from the USGS National Boat Ramps inventory