Some of these decisions are EPA's. 21 of these 76 records carry a Clean Water Act cleanup plan EPA established rather than Louisiana. They are counted in every figure on this page, and each record page names which.
State water-quality picture · #43 by reported lake-type waterbodies
Louisiana lakes and reservoirs
Every figure on this page is computed from the assessment decisions Louisiana reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 2016–2026), plus daily water-level observations from the U.S. Geological Survey.
- 76
- Reported waterbodies
- 64
- Not supporting a use
- Not reported
- Fish use assessments
- 2
- Gauged lakes
Louisiana in one line
76 lake-type waterbodies in Louisiana are reported to EPA ATTAINS across reporting cycles 2016–2026: 64 assessed as not supporting at least one designated use, 11 fully supporting, and 1 without a definitive overall verdict. The most-listed impairment cause is Mercury - Fish Consumption Advisory, on 31 waterbodies. This ranks the cause names filed in Louisiana, not distinct pollutants: mercury appears under 2 of them, together listed on 31 waterbodies.
- 76
- reported waterbodies
- 64
- not supporting a use
- 11
- fully supporting
- 86%
- of definitive verdicts impaired
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles. 1 of those 11 fully supporting verdicts (9%) rest on designated uses this site does not report (irrigation, navigation and industrial water supply), with Louisiana recording no verdict on fish consumption, recreation, aquatic life and drinking water. They are counted above because the state filed them, and excluded from the impaired share below because that figure compares states.
A compact Louisiana register with a concentrated not-supporting share
Louisiana's 76 lake-type units sit in the smallest third of state inventories, yet the ruled not-supporting share (86%) is in the upper third. The load is dense relative to register size.
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Louisiana reported 76 lake-type waterbodies in Louisiana in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
Overall-status split on Louisiana's compact register
Every reported lake-type unit in this smaller Louisiana filing set falls into exactly one overall-status bucket. The bar partitions 76 units; cause and gauge panels below stay separate.
Most-listed impairment causes in Louisiana
Waterbodies carrying each listed cause, most first
- Mercury - Fish Consumption Advisory
Mercury - Fish Consumption Advisory
31 waterbodies
- Dissolved Oxygen
Dissolved Oxygen
26 waterbodies
- Turbidity
Turbidity
17 waterbodies
- pH, High 8
pH, High
8 waterbodies
- Total Dissolved Solids (TDS) 7
Total Dissolved Solids (TDS)
7 waterbodies
What this shows Mercury - Fish Consumption Advisory is the most-listed impairment cause in Louisiana, on 31 of the lake-type waterbodies reported there. This ranks the cause names filed in Louisiana, not distinct pollutants: mercury appears under 2 of them, together listed on 31 waterbodies.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
Louisiana: 86% of ruled verdicts are not-supporting, against a national share of 53%, 1.6× the national rate.
Reporting practice
Nearly all of Louisiana's inventory carries 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.
Louisiana holds the 43rd-largest reported lake-type inventory in the country, 76 assessment units, carrying a definitive verdict on 97.4% of it. The counts above describe the 74 units carrying a verdict, not all 76 reported. Louisiana has also retired 2 lake-type assessment units, superseded filings that are kept on the site but not counted here.
The states reporting at the nearest rates are Delaware (97.9%) and Kansas (96.3%).
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.
Louisiana against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
97.4% 6th of 47 higher than 41 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 Louisiana
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 | Toledo Bend Reservoir-From Texas-Louisiana state line to Toledo Bend Dam Not Supporting | 165,487 |
| 2 | White Lake Not Supporting | 56,487 |
| 3 | Lake Salvador Not Supporting | 49,477 |
| 4 | Grand Lake Not Supporting | 47,869 |
| 5 | Lac Des Allemands Not Supporting | 16,596 |
| 6 | Catahoula Lake Not Supporting | 16,509 |
| 7 | Lake Fausse Point and Dauterive Lake Not Supporting | 16,495 |
| 8 | Lake Verret and Grassy Lake Fully Supporting | 16,311 |
| 9 | Caddo Lake-From Texas state line to spillway; includes James Bayou Not Supporting | 15,758 |
| 10 | Lake Bistineau Not Supporting | 14,447 |
| 11 | Bayou D'Arbonne Lake Fully Supporting | 12,711 |
| 12 | Lake Palourde Not Supporting | 10,770 |
By cause count
Most-listed waterbodies in Louisiana
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Louisiana.
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | Devil's Swamp Lake and Bayou Baton Rouge Not Supporting | 13 |
| 2 | Lake LaFourche Not Supporting | 5 |
| 3 | Chicot Lake Not Supporting | 4 |
| 3 | Clear Lake and Smithport Lake; includes old Edwards Lake Not Supporting | 4 |
| 3 | Cocodrie Lake Not Supporting | 4 |
| 3 | Crew Lake Not Supporting | 4 |
| 3 | Lake St. Joseph Not Supporting | 4 |
| 3 | White Lake Not Supporting | 4 |
| 9 | Black Lake and Clear Lake Not Supporting | 3 |
| 9 | Caddo Lake-From Texas state line to spillway; includes James Bayou Not Supporting | 3 |
8 of the 10 rows in this table tie on the ranked value: 6 at 4 (rank 3), 2 at 3 (rank 9). 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.
Gauge network
Lakes with a daily level record in Louisiana
Lakes with a linked USGS gauge and a daily water-level record. Readings are daily-batch snapshots, not real-time.
States near Louisiana's heavier not-supporting load
Two EPA ATTAINS peer sets outside Louisiana. The reporting-practice chart above stays on definitive-verdict share; the neighborhoods below emphasize cross-state nearest neighbors when the not-supporting count is in the upper third.
States with a similar reported inventory
Nearest states by lake-type units on the register (76 here).
Comparable not-supporting counts
Nearest states by units assessed not supporting a use (64 here). Inventory peers above are omitted.
- Arkansas · 62 not supporting · 2 off
- Tennessee · 60 not supporting · 4 off
- Kentucky · 72 not supporting · 8 off
- North Dakota · 52 not supporting · 12 off
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: 97.4% of the inventory reported from Louisiana carries a definitive verdict, 6th 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 Louisiana 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 Louisiana 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 Louisiana, 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.