Lake Helena Center Deep
Lewis and Clark County, MontanaView mapDirections
Montana DEQ publishes the water-quality measurements for Lake Helena Center Deep. Here is what has been measured.
- Impaired · Metals (other than mercury)
- Limited data
Lake Helena Center Deep in Lewis and Clark County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 5.6 ft visibility.
Lake Helena Center Deep is a lake in Lewis and Clark County, Montana.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2026-06-16. Methodology: how these readings are compared.
For a place on the water, look through cabin and lake-house rentals near Lake Helena Center Deep on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Lake Helena Center Deep is listed impaired under Clean Water Act §303(d) (IR 4A) for metals (other than mercury), nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Lake Helena Center Deep 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 Lake Helena Center Deep
These are the measurements Montana DEQ publishes for Lake Helena Center Deep, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5.6 ft. TSI 52.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.6ft | 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. | 52 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Stays near Lake Helena Center Deep
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Fishing Lake Helena Center Deep
EPA Impairment Status
Lake Helena Center Deep is officially listed as impaired under Clean Water Act §303(d) in the 2021 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Drinking water, Aquatic life.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MT41I007_010 · Official waterbody report
Nearby Lakes in Lewis and Clark County
Frequently asked questions about Lake Helena Center Deep
Where is Lake Helena Center Deep?
- Lake Helena Center Deep is a lake in Lewis and Clark County, Montana. Its water-quality measurements are published by Montana DEQ and shown on this page as reported.
What is the water quality of Lake Helena Center Deep?
- Lake Helena Center Deep in Lewis and Clark County, Montana has water-quality measurements published by Montana DEQ, shown here as reported. Water clarity: 5.6 ft visibility.
Is Lake Helena Center Deep safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Helena Center Deep is listed impaired under Clean Water Act §303(d) (IR 4A) for metals (other than mercury), nutrients (phosphorus, nitrogen). Check local advisories before you swim.
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Where this data comes from
5 measurements from 1 monitoring station, 2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana DEQ WQPB
MDEQ_WQ_WQX5 samples · 2026
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
Impairment status from EPA ATTAINS 303(d) database