
Sweetwater County Lake Quality
Wyoming, 26 lakes — no lake here has enough monitoring data for a grade
Sweetwater County's 26 monitored lakes fall in the moderate-density bracket for Wyoming. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. No lake in Sweetwater County has enough sampling behind it for an A–F grade yet. The 26 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.
Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.
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Quick Answers for Sweetwater County
Planning a trip? Check special fishing regulations for Flaming Gorge Reservoir — or check the official Wyoming fishing regulations.
All Lakes in Sweetwater County
26 lakes · 0 graded, 26 not rated0 graded lakes · 26 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| NRFlaming Gorge ReservoirSweetwater | NR | 11.8 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlacks Fork LakeSweetwater | NR | 8.5 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlacks Fork Inflow LakeSweetwater | NR | 5.2 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRJim Bridger PondSweetwater | NR | 4.9 ft | 13 µg/L | No recent samples | No recent samples | ✓ Public | |
| NRBig Sandy ReservoirSweetwater | NR | 0.7 ft | 45 µg/L | No recent samples | No recent samples | ✓ Public | |
| NRGreen River Inflow LakeSweetwater | NR | 1.6 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRFlaming Gorge-Green River Off Firehole Canyon Campground LakeSweetwater | NR | 4.4 ft | No recent samples | 1.6 µg/L | No recent samples | Not recorded | |
| NRA And M ReservoirSweetwater | NR | No recent samples | 30 µg/L | No recent samples | No recent samples | Not recorded | |
| NRScotty LakeSweetwater | NR | No recent samples | 900 µg/L | No recent samples | No recent samples | Not recorded | |
| NRStevens Draw ReservoirSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCow Creek ReservoirSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMonument LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRFrewen LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRRed LakesSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NREden ReservoirSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMcKay LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBush LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBuffalo Hump LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBrannan ReservoirSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRHay ReservoirSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLost Creek LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMud LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRHansen LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMud Springs LakeSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMahoney LakesSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMahoney LakesSweetwater | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in Wyoming
See how Sweetwater County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.