US States With the Most Lake Waterbodies Assessed as Impaired
EPA ATTAINS data ranking states by lake-type waterbodies their agencies assessed as not supporting at least one designated use.
Original analysis
Research
Every figure below is read from the current assessment and water-level dataset and traces back to a source record you can check.
- 3
- published analyses
What can you learn from PlainLakes research?
What this research covers
PlainLakes research ranks EPA ATTAINS lake-type assessment units across 60,590 reported waterbodies in 50 states; 12,831 of 26,427 with a definitive verdict are not supporting at least one designated use.
- 60,590
- lake-type waterbodies in ATTAINS
- 50
- states reporting
- 12,831
- not supporting ≥1 designated use
Studies below answer one ranking question each from the live ATTAINS mirror; they are descriptive assessment statistics, not swimming or drinking-water advice.
Published research articles
The Most Common Impairment Causes in US Lake Assessments
EPA ATTAINS data ranking the causes states list most often when a lake fails to support a designated use.
The Largest Assessed Lakes in the United States
EPA ATTAINS data ranking lake-type assessment units by assessed acreage, with each unit's assessment outcome.
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.