Updated Aug 2026
Utah Lake Water Quality
Water quality grades for 168 monitored lakes across 28 counties.
Across Utah, 168 lakes carry an active water-quality grade spread over 28 counties. The underlying measurements come from the Utah Division of Water Quality, alongside federal programs and volunteer monitoring networks. Around 22% of the state's lakes pull an A — 37 top-tier waters. The B and C brackets together hold most of the rest, with the F bracket capturing 10 stressed lakes mostly in the agricultural south of the state.
Mesotrophic is the dominant trophic class — a workable middle ground between the pristine oligotrophic deep lakes and the algal-pressured eutrophic shallow ones. Tooele ranks highest on average county grade (A). Davis sits lowest. With only 28 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.
Grade Distribution
All 168 Utah lakes in the index: 126 (75.0%) carry an A–F grade and 42 (25.0%) are not rated, because they lack enough recent nutrient or algae sampling to support a letter.
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Top-Graded Utah Lakes
The highest water-quality grades in Utah — clarity, depth, and A-F grade at a glance.
Lake Map
Explore Utah Lakes
Utah reports, fishing & travel
Reservoirs in Utah
View all 95 reservoirs →95 of 168 Utah lakes (57%) are man-made reservoirs in the USACE National Inventory of Dams. 92 carry a High or Significant hazard rating. The oldest matched dam dates to 1872.
EPA-Impaired Lakes in Utah
View all 77 impaired lakes →77 of 168 Utah lakes (46%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 47 have an approved Total Maximum Daily Load (TMDL) restoration plan.
Utah Fishing & Recreation
Licenses, regulations, records, and where to fish across Utah.
Counties
All 28 Utah counties, ranked by average lake water quality. Compare them against every county nationwide in the county rankings, browse the full directory of graded lakes, or pick a different state.
Top 25 Cleanest Lakes
25 lakes25 graded lakes
| # | Lake | County | Grade | Clarity | Trophic | Access |
|---|---|---|---|---|---|---|
| 1 | AFlaming Gorge Reservoir Antelope Flat | Daggett | A | 25.3 ft | Oligotrophic | Not recorded |
| 2 | AFlaming Gorge Lake | Daggett | A | 29.5 ft | Oligotrophic | ✓ Public |
| 3 | AFlaming Gorge Reservoir | Daggett | A | 31.8 ft | Oligotrophic | Not recorded |
| 4 | AWide Hollow Reservoir | Garfield | A | 13.8 ft | Mesotrophic | ✓ Public |
| 5 | AStarvation Reservoir | Duchesne | A | 11.2 ft | Oligotrophic | ✓ Public |
| 6 | ARecapture Reservoir | San Juan | A | 8.9 ft | Oligotrophic | Not recorded |
| 7 | ALittle Dell Reservoir | Salt Lake | A | 14.8 ft | Oligotrophic | Not recorded |
| 8 | ARed Fleet Reservoir | Uintah | A | 5.9 ft | Oligotrophic | ✓ Public |
| 9 | ASilver Lake Flat Reservoir | Utah | A | 10.5 ft | Oligotrophic | Not recorded |
| 10 | ASalem Pond | Utah | A | 5.9 ft | Mesotrophic | Not recorded |
| 11 | ASettlement Canyon Reservoir | Tooele | A | 8.5 ft | Oligotrophic | Not recorded |
| 12 | AGrantsville Reservoir | Tooele | A | 5.9 ft | Mesotrophic | Not recorded |
| 13 | ALake Mary | Salt Lake | A | 26.9 ft | Oligotrophic | Not recorded |
| 14 | AMillsite Reservoir | Emery | A | 10.5 ft | Oligotrophic | ✓ Public |
| 15 | AGunlock Reservoir | Washington | A | 4.6 ft | Mesotrophic | ✓ Public |
| 16 | AGunlock Reservoir Midway | Washington | A | 4.6 ft | Mesotrophic | Not recorded |
| 17 | ANewton Reservoir | Cache | A | 15.4 ft | Oligotrophic | Not recorded |
| 18 | ADmad Reservoir N of Cut | Millard | A | 0.7 ft | Mesotrophic | Not recorded |
| 19 | AGunnison Bend Reservoir | Millard | A | 1.5 ft | Mesotrophic | Not recorded |
| 20 | AHyrum Reservoir | Cache | A | 6.9 ft | Mesotrophic | ✓ Public |
| 21 | ABear Lake | Rich | A | 20.7 ft | Oligotrophic | Not recorded |
| 22 | AMantua Reservoir N | Box Elder | A | 3 ft | Oligotrophic | Not recorded |
| 23 | ABig Sand Wash Reservoir | Duchesne | A | 10.7 ft | Mesotrophic | Not recorded |
| 24 | ABrough Reservoir | Uintah | A | 6.2 ft | Mesotrophic | Not recorded |
| 25 | AMoon Lake | Duchesne | A | 9.5 ft | Mesotrophic | Not recorded |
25 Lakes Needing Attention
25 lakes25 graded lakes
| # | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | FFarmington Bay Lake | Davis | F | No recent samples |
| 2 | FUtah Lake Sp @ Marina | Utah | F | 0.7 ft |
| 3 | FUtah Lake | Utah | F | 0.7 ft |
| 4 | FUtah Lake | Utah | F | 0.7 ft |
| 5 | FYuba Reservoir Midway | Juab | F | 2.8 ft |
| 6 | FKoosharem Reservoir | Sevier | F | 7.2 ft |
| 7 | FUtah Lake Outside Entrance To Provo Bay | Utah | F | 0.7 ft |
| 8 | FUtah Lake Goshen Bay Southwest End | Utah | F | 0.7 ft |
| 9 | FUtah Lake | Utah | F | 0.7 ft |
| 10 | FUtah Lake | Utah | F | 0.5 ft |
| 11 | DGsl Breach Lake | Box Elder | D | No recent samples |
| 12 | DWillard Pond East End | Box Elder | D | 6.4 ft |
| 13 | DWillard Pond West End | Box Elder | D | 4.3 ft |
| 14 | DLost Creek Reservoir | Morgan | D | 9.2 ft |
| 15 | DLost Creek Reservoir Midway | Morgan | D | 8.4 ft |
| 16 | DBirch Creek Reservoir | Rich | D | 7.4 ft |
| 17 | DUtah Lake Saratoga Springs Marina Boat Ramp | Utah | D | 0.7 ft |
| 18 | DAnderson Meadow Reservoir | Beaver | D | 10.2 ft |
| 19 | DYuba Reservoir | Juab | D | 3.9 ft |
| 20 | DMatt Warner Reservoir E | Uintah | D | 6.2 ft |
| 21 | DPanguitch L Shore Lake | Garfield | D | 5.7 ft |
| 22 | DMiller Flat Reservoir | Emery | D | 10.2 ft |
| 23 | DBrowne Lake | Daggett | D | 6.6 ft |
| 24 | DMantua Reservoir S | Box Elder | D | 2.6 ft |
| 25 | DHoop Lake | Summit | D | 5.6 ft |
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Source: EPA National Aquatic Resource Surveys and the EPA Water Quality Portal.
More on lake water quality
The top-graded lake in every state we cover, picked grade-first with water clarity as the tie-breaker — plus the states whose winner is still not clean.
State-by-state Secchi champions: the clearest measured lake in each U.S. state we grade, which is not the same as the cleanest nutrient grade.
A data snapshot of the lakes we grade: how the A–F distribution breaks down, the clearest and the greenest states, and where the water is improving.
How lakes are graded A–F on nutrients and algae using EPA ecoregion condition classes, what each letter means in the water, and why an A is not a clearance.