Holter Reservoir is a cold, clear oligotrophic lake in Lewis and Clark County, Montana. Water quality is graded A based on 1 sampling years through 2026. Compared to the 11 other monitored lakes in Lewis and Clark County, Holter Reservoir ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DNR, last sampled 2026-06-17. Grade methodology: LakeGrade methodology.
Watch Holter Reservoir water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 15.4 ft down. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.4 ft | A |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Holter Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Holter Reservoir in Lewis and Clark 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 Holter Reservoir
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 trip to Holter Reservoir?
Get lake water-quality report cards plus the best cabin & lodging deals near Holter Reservoir — straight to your inbox. No spam, unsubscribe anytime.
Fishing Holter Reservoir
Location
County Ranking
Ranked #5 of 12 lakes in Lewis and Clark County
Nearby Lakes in Lewis and Clark County
Explore Holter Reservoir across LakeGrade
More Montana Lake Rankings
Other Grade A Lakes in Montana
Oligotrophic Lakes in Montana
More records, surveys & data sources
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2026-06-17
Monitoring stations: 1