Ashley Lake
Flathead County, Montana2,852 acresView mapDirections
Montana DEQ publishes the water-quality measurements for Ashley Lake. Here is what has been measured.
- Public access
- Limited data
Ashley Lake in Flathead County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 33.1 ft visibility. Surface area: 2852 acres.
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. Methodology: how these readings are compared.
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 conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Ashley Lake is safe to swim in today is a call for the Montana Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Ashley Lake
These are the measurements Montana DEQ publishes for Ashley Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 33.1 ft down. TSI 27.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 33.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 27 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Ashley Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
2,852 acres
Public access
Yes
Listed by Montana DEQ
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
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Stays near Ashley Lake
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Fishing Ashley Lake
Water Quality Trend: Worsening
Based on 12 years of monitoring (2012–2023).
Water clarity
Stable4 years
Phosphorus
Worsening+0.48 µg/L/yr12 years
Chlorophyll-a
Stable0 µg/L/yr12 years
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
Nearby Lakes in Flathead County
Frequently asked questions about Ashley Lake
Where is Ashley Lake?
- Ashley Lake is a lake in Flathead County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.
What is the water quality of Ashley Lake?
- Ashley Lake in Flathead County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 33.1 ft visibility. Surface area: 2852 acres.
Is Ashley Lake safe to swim in?
- Nutrient and algae readings are 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.
Can I fish at Ashley Lake?
- Ashley Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Montana's fish and wildlife agency, so check its current regulations before you go.
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory