State assessment records · federal gauge data
What does the record say about your lake?
42,622 named lakes and reservoirs, exactly as state agencies and tribal nations reported them to EPA: assessment status, listed impairment causes, and fish-consumption verdicts. Daily USGS water levels for the 121 that carry one. No modeling, no scores, the record itself.
The national picture in one line
State agencies and tribal nations report 60,590 lake-type waterbodies to EPA ATTAINS across 50 states; among the 24,429 carrying a definitive verdict, 52.5% are not supporting at least one designated use - a 1.1× ratio of not-supporting to fully-supporting listings.
- 52.5%
- definitive verdicts not supporting a use
- 11,598
- fully supporting on reported uses
- 78%
- fish fish-consumption or related fishery use not supporting
- 0.3%
- named lakes with a daily USGS gauge
A definitive verdict is Fully Supporting or Not Supporting. Not Assessed and Insufficient Information are excluded; an unassessed lake is neither confirmed clean nor confirmed impaired.
According to the U.S. Environmental Protection Agency's ATTAINS program, state agencies and tribal nations report 60,590 lake-type waterbodies nationwide in the August 2026 extract, and PlainLakes renders those filed assessment decisions alongside linked U.S. Geological Survey daily gauge records where a conservative name match exists. See our methodology for reporting-unit limits, filer attribution, and refresh cadence.
- 42,622
- Named waterbodies
- 12,831
- Not supporting a use
- 121
- Daily level record
- 50
- States reporting
Data updated 2026-08-17
Where impaired lakes concentrate
Waterbodies assessed as not supporting at least one designated use, by state
View all 50 states as a list
- New Hampshire: 3K
- Minnesota: 2K
- Michigan: 807
- Massachusetts: 678
- Florida: 636
- New Jersey: 583
- New York: 563
- Wisconsin: 493
- Illinois: 434
- Washington: 393
- Kansas: 241
- Nebraska: 219
- South Carolina: 212
- California: 202
- Virginia: 181
- Oregon: 165
- Vermont: 154
- Oklahoma: 153
- Missouri: 151
- Indiana: 145
- South Dakota: 145
- Alabama: 143
- Iowa: 137
- Pennsylvania: 135
- Texas: 125
- Rhode Island: 119
- North Carolina: 90
- Colorado: 89
- Utah: 77
- Kentucky: 72
- Louisiana: 64
- Arkansas: 62
- Tennessee: 60
- North Dakota: 52
- Idaho: 51
- Georgia: 47
- New Mexico: 46
- Connecticut: 44
- West Virginia: 44
- Delaware: 40
- Nevada: 36
- Arizona: 34
- Maryland: 32
- Maine: 31
- Montana: 28
- Mississippi: 14
- Alaska: 7
- Ohio: 7
- Wyoming: 7
- Hawaii: 2
What this shows New Hampshire lists the most not-supporting waterbodies of any state (2,783); darker tiles carry more listings. Coverage reflects each state's own monitoring program, so the map compares reported assessments, not underlying water quality.
Most-listed impairment causes nationally
Waterbodies carrying each listed cause, most first
- Mercury in Fish Tissue
Mercury in Fish Tissue
2,961 waterbodies
- Mercury - Fish Consumption Advisory
Mercury - Fish Consumption Advisory
2,893 waterbodies
- Phosphorus, Total
Phosphorus, Total
1,734 waterbodies
- pH
pH
1,395 waterbodies
- Dissolved Oxygen 948
Dissolved Oxygen
948 waterbodies
- Escherichia coli (E. coli) 922
Escherichia coli (E. coli)
922 waterbodies
- Nutrients 880
Nutrients
880 waterbodies
- Mercury 852
Mercury
852 waterbodies
What this shows Mercury in Fish Tissue leads on 2,961 waterbodies in 24 states. This ranks the cause names states file, not distinct pollutants: mercury reaches the list under 7 labels, and counting them together it is listed on 6,851 waterbodies across 42 states.
Come back when the record updates
Save lakes to re-check later
State integrated reports refresh on multi-year assessment cycles; linked USGS gauges publish new daily readings. The Lake Watchlist stores your list in the browser, tracks when you last looked, and nudges a re-check after about six months, no account and no email alerts.
- •EPA ATTAINS extract vintage: August 2026 on this build.
- •USGS NWIS daily values refresh for linked gauges; level charts show the latest observation in the series.
- •Use the fish-consumption lookup for one-off searches; save records you revisit.
Clear anytime via browser storage settings. We never receive your list.
Ways in
Explore the record
Six routes into the same underlying assessment and gauge data.
By state
Status mix, top causes, and gauge coverage for every state.
Most reported: Wisconsin, 19,871
All 50 states →Rankings
Largest lakes, most-listed causes, level movers, state shares.
Biggest 30-day drop: Paonia Reservoir. (-36.88 ft)
See the rankings →Browse A to Z
15,611 waterbodies with populated records, filterable by state.
Browse waterbodies →Lookup tools
Fish-consumption status and water levels by lake name.
Open the lookup →Research
Original analyses computed from the assessment corpus, each with its query and exclusions stated.
50 states · 24,429 ruled assessments
Read the analyses →Statistics
National impairment shares, gauge coverage, and a downloadable state summary CSV.
52.5% not supporting a use (ruled)
See key findings →Lakes readers are searching
Start here
Understand the data
- Can you eat the fish? What the consumption verdict means and where binding advice lives.
- Assessment status, decoded Fully Supporting, Not Supporting, and the five IR categories.
- Reading lake-level data Elevation, gage height, storage, and datum caveats.
- The 303(d) list, explained How lakes get listed as impaired, and how they get off.
- Common impairment causes Mercury, nutrients, pathogens, and what each means for you.
- Recreation safety signals What assessment data can and cannot tell swimmers.
What to do with this data
- Save lakes you care about and come back to check their assessment status or water level over time. Open the watchlist
- Every state runs its own assessment program on its own cycle; browse by state to see what your state has actually reported. Browse by state
- An impairment listing is a regulatory finding under the Clean Water Act, not a real-time pollution alert or a closure notice. 303(d) explained
PlainLakes renders state assessment decisions and federal gauge observations without modification. It does not issue advisories.
About this data
About this data
What this site is
PlainLakes is a reference layer over two public records: the assessment decisions state agencies report to EPA's ATTAINS system under the Clean Water Act, and daily lake-level observations from the USGS National Water Information System. Pages render those records without recomputing them; PlainLakes issues no advisories and computes no scores. PlainLakes makes fifteen decisions of its own about which filed record to publish, and states each of them on its methodology page. The furthest-reaching is which monitoring site belongs to which lake, because no federal source publishes that crosswalk. The opening location sentence is either the state's own text with non-geographic clauses removed, or, where the state filed county codes rather than a sentence, one PlainLakes composed from those codes.
Editorial process
- Ingest Assessment units, use verdicts, causes, and gauge daily values are pulled from the official EPA and USGS services, per state.
- Link conservatively A monitoring site is attached to a lake only on an exact name match within the same state that identifies one assessed waterbody, and only when that site reports daily values: a name fitting two waterbodies is left unlinked rather than guessed. Where several sites on one lake carry its name, the record follows the one with the densest 365-day series and names it.
- Publish with provenance Every page states its sources and data vintage; records lacking populated data dimensions stay out of the index with an honest coverage note.
Editorial independence & corrections
Spotted a value that disagrees with the official record? Write to corrections@plainlakes.com with the lake page and the source value; the corrections policy explains the process.
Frequently asked
Is this real-time water data?
No. Water levels are daily-batch USGS observations and assessment verdicts are cycle-based state decisions, typically updated every two years.
Why is a lake missing?
PlainLakes indexes waterbodies whose reported record has populated data dimensions, so a lake no agency has assessed and no gauge is linked to has nothing to render. A missing water level is not evidence that USGS ignores the lake: for 64.2% of the lakes without one, the waterbody carries a name, and no monitoring site in NWIS carries one that identifies it, at any status, in either the lake-site inventory or among the sites reporting lake or reservoir level under another site type, so there is nothing to match it to.
Can I rely on this to eat fish I catch?
Use it as a starting point only. Your state fish-consumption advisory program issues the binding, species-specific meal guidance.