Lake Helena Center Deep is a productive, nutrient-rich eutrophic lake in Lewis and Clark County, Montana. Water quality is graded D based on 1 sampling years through 2026. Compared to the 11 other monitored lakes in Lewis and Clark County, Lake Helena Center Deep ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DNR, last sampled 2026-06-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Murky, only visible to about 5.6 ft. Trophic State Index: 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | D |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Helena Center Deep
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Location
County Ranking
Ranked #11 of 12 lakes in Lewis and Clark County
Cleaner Lakes Within 30 Miles
Lake Helena Center Deep holds Grade D. One nearby lake has a higher grade.
Nearby Lakes in Lewis and Clark County
Explore Lake Helena Center Deep across LakeGrade
More Montana Lake Rankings
Other Grade D Lakes in Montana
Eutrophic 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: 2026-06-16
Monitoring stations: 1