State water-quality picture · #40 by reported lake-type waterbodies
Mississippi lakes and reservoirs
Every figure on this page is computed from the assessment decisions Mississippi reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 2014–2024), plus daily water-level observations from the U.S. Geological Survey.
- 114
- Reported waterbodies
- 14
- Not supporting a use
- 8
- Fish use not supporting
- 0
- Gauged lakes
Mississippi in one line
114 lake-type waterbodies in Mississippi are reported to EPA ATTAINS across reporting cycles 2014–2024: 14 assessed as not supporting at least one designated use, 84 fully supporting, and 16 without a definitive overall verdict. The most-listed impairment cause is Mercury in Fish Tissue, on 7 waterbodies.
- 114
- reported waterbodies
- 14
- not supporting a use
- 84
- fully supporting
- 14%
- of definitive verdicts impaired
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles.
Mississippi's smaller reported lake-type inventory
At 114 units, Mississippi is in the lowest third of state lake-type registers. The charts below describe that compact filing set, not a national-scale inventory.
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Mississippi reported 114 lake-type waterbodies in Mississippi in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
Overall-status split on Mississippi's compact register
Every reported lake-type unit in this smaller Mississippi filing set falls into exactly one overall-status bucket. The bar partitions 114 units; cause and gauge panels below stay separate.
Most-listed impairment causes in Mississippi
Waterbodies carrying each listed cause, most first
- Mercury in Fish Tissue
Mercury in Fish Tissue
7 waterbodies
- Organic Enrichment
Organic Enrichment
4 waterbodies
- Nitrogen 2
Nitrogen
2 waterbodies
- pH 2
pH
2 waterbodies
- Biochemical Oxygen Demand (BOD) 1
Biochemical Oxygen Demand (BOD)
1 waterbodies
What this shows Mercury in Fish Tissue is the most-listed impairment cause in Mississippi, on 7 of the lake-type waterbodies reported there.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
Mississippi: 14% of ruled verdicts are not-supporting, against a national share of 53%, 3.8× below the national rate.
Reporting practice
Mississippi's waterbodies mostly carry a definitive verdict
Each reporting authority decides how much of the water it files to EPA it actually assesses in a cycle. That decision sets the denominator behind every count on this page.
Mississippi holds the 40th-largest reported lake-type inventory in the country, 114 assessment units, carrying a definitive verdict on 86% of it. The counts above describe the 98 units carrying a verdict, not all 114 reported. Mississippi has also retired 4 lake-type assessment units, superseded filings that are kept on the site but not counted here.
The states reporting at the nearest rates are Virginia (84%) and South Carolina (88.4%).
Assessing more of an inventory is a reporting choice, set by cycle length, monitoring budget and how finely a state splits its waters into units. It is not a measure of water quality, and it is why a raw count from one state does not sit beside a raw count from another. How assessment coverage varies.
Mississippi against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
86% 16th of 47 higher than 31 of 47 states
the 47 comparable states, by definitive-verdict share
Each bar is a band; taller bars hold more states. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA ATTAINS · Reporting cycles 1987–2026
Each bar counts states whose definitive-verdict share falls in that 10-point band. The 47 states shown are those reporting at least 25 lake-type units; a share off a smaller inventory is precision the data does not have.
By size
Largest assessed lakes in Mississippi
By assessed acreage as reported in ATTAINS. Acreage is the assessed unit's size, which can differ from a lake's full surface area.
| # | Waterbody | Assessed acres |
|---|---|---|
| 1 | Ross Barnett Reservoir Assessment unit MS507511 Fully Supporting | 20,737 |
| 2 | Sardis Lake Fully Supporting | 15,277 |
| 3 | Grenada Lake Assessment unit MS914611 Fully Supporting | 9,927 |
| 4 | Arkabutla Lake Fully Supporting | 6,279 |
| 5 | Grenada Lake Assessment unit MS915811 Not Supporting | 6,011 |
| 6 | Ross Barnett Reservoir Assessment unit MS507412 Fully Supporting | 5,483 |
| 7 | Enid Lake Assessment unit MS907612 Fully Supporting | 4,741 |
| 8 | Enid Lake Assessment unit MS907911 Fully Supporting | 4,499 |
| 9 | Eagle Lake Fully Supporting | 4,476 |
| 10 | Okatibbee Lake Fully Supporting | 4,243 |
| 11 | Enid Lake Assessment unit MS907811 Not Supporting | 3,958 |
| 12 | Tunica Cutoff Not Supporting | 3,719 |
By cause count
Most-listed waterbodies in Mississippi
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Mississippi.
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | Loakfoma Lake Not Supporting | 4 |
| 2 | Lake Henry Not Supporting | 3 |
| 2 | Tunica Cutoff Not Supporting | 3 |
| 4 | Roebuck Lake Not Supporting | 2 |
| 5 | Beaver Lake Not Supporting | 1 |
| 5 | Enid Lake Assessment unit MS907811 Not Supporting | 1 |
| 5 | Enid Lake Assessment unit MS907513 Not Supporting | 1 |
| 5 | Grenada Lake Assessment unit MS915811 Not Supporting | 1 |
| 5 | Grenada Lake Assessment unit MS916312 Not Supporting | 1 |
| 5 | Grenada Lake Assessment unit MS914712 Not Supporting | 1 |
8 of the 10 rows in this table tie on the ranked value: 2 at 3 (rank 2), 6 at 1 (rank 5). Tied rows share a rank and are listed in no meaningful order; where a tie reaches the top the medal is shared, because nothing separates those rows.
States near Mississippi's lighter not-supporting load
Two EPA ATTAINS peer sets outside Mississippi. The reporting-practice chart above stays on definitive-verdict share; these neighborhoods highlight register-size and not-supporting peers while Mississippi's ruled impairment share sits in the lowest third.
Similar reported inventory
Nearest states by lake-type units on the register (114 here).
Peers are nearest-neighbor matches on EPA ATTAINS register size and not-supporting counts among states with at least 25 reported units. Impairment peers skip states already listed in the inventory column so the two link sets stay distinct.
Using this state picture
- Comparisons across states hold on shares, not counts: 86% of the inventory reported from Mississippi carries a definitive verdict, 16th of 47 comparable states. National rankings
- Fish-consumption verdicts here are assessment decisions. Species-level meal advice comes from the state fish-advisory program. Consumption guide
- Browse every named Mississippi waterbody with a populated record. Browse waterbodies
PlainLakes renders state assessment decisions and federal gauge observations without modification.
Figures on this page are computed from the assessment decisions Mississippi reported to EPA's ATTAINS system and from USGS National Water Information System daily values, no number is typed in by an editor. State counts aggregate every lake-type assessment unit reported by Mississippi, including unnamed units that never receive their own page. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.