Updated Aug 2026
Tennessee Lake Water Quality
Water quality grades for 76 monitored lakes across 42 counties.
76 Tennessee lakes carry a grade. Most of the input data flows through monitoring run by the Tennessee Department of Environment and Conservation, which feeds state, federal, and volunteer measurements into the EPA Water Quality Portal. Only about 0% of Tennessee's lakes pull an A grade — the smaller, agricultural-watershed lakes that dominate the dataset tend to carry persistent nutrient loads. 29% of lakes fall in the D or F brackets.
Eutrophic conditions dominate — nutrient-loaded, productive, with algal pressure that shows up most years in late summer. These lakes tend to be shallow, agricultural-watershed, and over-warmed by the time July ends. Rhea ranks highest on average county grade (B). Stewart sits lowest. With only 42 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.
Grade Distribution
All 76 Tennessee lakes in the index: 32 (42.1%) carry an A–F grade and 44 (57.9%) are not rated, because they lack enough recent nutrient or algae sampling to support a letter.
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Top-Graded Tennessee Lakes
The highest water-quality grades in Tennessee — clarity, depth, and A-F grade at a glance.
Lake Map
Explore Tennessee Lakes
Tennessee reports, fishing & travel
Reservoirs in Tennessee
View all 17 reservoirs →17 of 76 Tennessee lakes (22%) are man-made reservoirs in the USACE National Inventory of Dams. 15 carry a High or Significant hazard rating. The oldest matched dam dates to 1911.
EPA-Impaired Lakes in Tennessee
View all 22 impaired lakes →22 of 76 Tennessee lakes (29%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 7 have an approved Total Maximum Daily Load (TMDL) restoration plan.
Tennessee Fishing & Recreation
Licenses, regulations, records, and where to fish across Tennessee.
Counties
All 42 Tennessee 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 | BPiney River Lake | Rhea | B | 6.4 ft | Mesotrophic | ✓ Public |
| 2 | CHiwassee River Lake | Bradley | C | 4.1 ft | Eutrophic | ✓ Public |
| 3 | CTennessee River Lake | Rhea | C | 7.1 ft | Eutrophic | ✓ Public |
| 4 | CTennessee River Lake | Hamilton | C | 5.4 ft | Eutrophic | ✓ Public |
| 5 | CTennessee River Lake | Knox | C | No recent samples | Eutrophic | ✓ Public |
| 6 | CTennessee River Lake | Roane | C | No recent samples | Eutrophic | ✓ Public |
| 7 | CCalderwood Lake | Blount | C | 16.4 ft | Mesotrophic | ✓ Public |
| 8 | CPoor Valley Creek Lake | Hawkins | C | No recent samples | Mesotrophic | Not recorded |
| 9 | CBoiling Fork Creek Lake | Franklin | C | No recent samples | Eutrophic | Not recorded |
| 10 | CEmory River Lake | Roane | C | No recent samples | Mesotrophic | ✓ Public |
| 11 | DTennessee River Lake | Meigs | D | 4.4 ft | Eutrophic | ✓ Public |
| 12 | DTennessee River Lake | Marion | D | 7.6 ft | Eutrophic | ✓ Public |
| 13 | DTennessee River Lake | Loudon | D | No recent samples | Eutrophic | ✓ Public |
| 14 | DTennessee River Lake | Henry | D | No recent samples | Eutrophic | ✓ Public |
| 15 | DOcoee River Lake | Polk | D | 7.5 ft | Eutrophic | Not recorded |
| 16 | DClinch River Lake | Roane | D | No recent samples | Eutrophic | ✓ Public |
| 17 | DCumberland River Lake | Davidson | D | No recent samples | Eutrophic | Not recorded |
| 18 | DCumberland River Lake | Wilson | D | No recent samples | Eutrophic | ✓ Public |
| 19 | DCumberland River Lake | Stewart | D | No recent samples | Eutrophic | ✓ Public |
| 20 | DCumberland River Lake | Cheatham | D | No recent samples | Eutrophic | ✓ Public |
| 21 | DCumberland River Lake | Stewart | D | No recent samples | Eutrophic | ✓ Public |
| 22 | DBig Sandy River Lake | Benton | D | No recent samples | Eutrophic | ✓ Public |
| 23 | DBeech River Lake | Decatur | D | No recent samples | Eutrophic | Not recorded |
| 24 | DDuck River Lake | Humphreys | D | No recent samples | Hypereutrophic | Not recorded |
| 25 | DReelfoot Lake Blue Basin | Lake | D | No recent samples | Hypereutrophic | ✓ Public |
25 Lakes Needing Attention
25 lakes25 graded lakes
| # | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | DHolston River Lake | Hawkins | D | No recent samples |
| 2 | DCaney Creek Lake | Roane | D | No recent samples |
| 3 | DWatauga River Lake | Washington | D | No recent samples |
| 4 | DReelfoot Lake-Reelfoot Creek Embayment | Obion | D | No recent samples |
| 5 | DReelfoot Lake Upper Blue Basin | Obion | D | No recent samples |
| 6 | DMckellar Lake | Shelby | D | No recent samples |
| 7 | DRobertson Creek Lake | Hawkins | D | No recent samples |
| 8 | DReelfoot Lake Blue Basin | Lake | D | No recent samples |
| 9 | DDuck River Lake | Humphreys | D | No recent samples |
| 10 | DBeech River Lake | Decatur | D | No recent samples |
| 11 | DBig Sandy River Lake | Benton | D | No recent samples |
| 12 | DCumberland River Lake | Stewart | D | No recent samples |
| 13 | DCumberland River Lake | Cheatham | D | No recent samples |
| 14 | DCumberland River Lake | Stewart | D | No recent samples |
| 15 | DCumberland River Lake | Wilson | D | No recent samples |
| 16 | DCumberland River Lake | Davidson | D | No recent samples |
| 17 | DClinch River Lake | Roane | D | No recent samples |
| 18 | DOcoee River Lake | Polk | D | 7.5 ft |
| 19 | DTennessee River Lake | Henry | D | No recent samples |
| 20 | DTennessee River Lake | Loudon | D | No recent samples |
| 21 | DTennessee River Lake | Marion | D | 7.6 ft |
| 22 | DTennessee River Lake | Meigs | D | 4.4 ft |
| 23 | CEmory River Lake | Roane | C | No recent samples |
| 24 | CBoiling Fork Creek Lake | Franklin | C | No recent samples |
| 25 | CPoor Valley Creek Lake | Hawkins | C | No recent samples |
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.