Bighorn Lake
Big Horn County, WyomingView mapDirections
Nutrients and algae sit mid-range for this region.
- Eutrophic
- #2 of 5 in the county
- Limited data
Bighorn Lake in Big Horn County, Wyoming has a water quality grade of C (Fair). Phosphorus: 64.5 µg/L. Chlorophyll-a (algae): 18.6 µg/L.
- Type
- Eutrophic
- Phosphorus
- 64.5 µg/L
- Chlorophyll-a
- 18.6 µg/L
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Bighorn Lake is a productive, nutrient-rich eutrophic lake in Big Horn County, Wyoming. Water quality is graded C based on 1 sampling years through 2019. Compared to the 4 other monitored lakes in Big Horn County, Bighorn Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2019-08-13. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Phosphorus 64.5 µg/L. Chlorophyll-a 18.6 µg/L. TSI 62. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 64.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 18.6 µg/L | Not graded |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Fishing Bighorn Lake
County Ranking
Ranked #2 of 5 lakes in Big Horn County
Nearby Lakes in Big Horn County
Frequently asked questions about Bighorn Lake
Where is Bighorn Lake?
- Bighorn Lake is a lake in Big Horn County, Wyoming. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Bighorn Lake?
- Bighorn Lake in Big Horn County, Wyoming has a water quality grade of C (Fair). Phosphorus: 64.5 µg/L. Chlorophyll-a (algae): 18.6 µg/L.
Is Bighorn Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Bighorn Lake across LakeQuality
14.5 mi away · 200 ft
11.8 mi away · recorded at 68°F
Species activity outlook by water temperature and season
Where to stay at Wyoming's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Wyoming's cleanest and most-polluted lakes, ranked
More Wyoming Lake Rankings
Other Grade C Lakes in Wyoming
Eutrophic Lakes in Wyoming
Where this data comes from
20 measurements from 10 monitoring stations, 2019. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Wyoming Water Science Center
USGS-WY20 samples · 2019
Analytical methods
- P, wu, WCA, persulfate CF color
- Plant pigments, sonication & 445
Monitoring station identifiers (10)
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.