Disclaimer

Last updated: April 2026

Informational use only

LakeQuality publishes data, scores, rankings, and analysis about U.S. lake and freshwater quality. Everything on lakequality.org is provided for general informational and educational purposes only. It is not professional advice and should not be relied on as the sole basis for any consequential decision.

Nothing on lakequality.org constitutes financial, legal, medical, tax, investment, real-estate, insurance, or engineering advice. Always consult a qualified, licensed professional for decisions that affect your money, health, safety, legal status, or property.

Data source and accuracy

The underlying data displayed on lakequality.org is derived from the EPA Water Quality Portal, the Minnesota DNR LakeFinder, and the Wisconsin DNR Surface Water dataset. We do our best to process that data faithfully, but we make no representations or warranties — express or implied — about the completeness, accuracy, reliability, suitability, or availability of any information, analysis, or related graphics.

Source records may contain errors, be incomplete, be reported late, or be restated by the issuing agency after publication. Where the source corrects a record, LakeQuality will follow on the next refresh — but there may be a lag. Always verify any figure against the original source before acting on it.

How we process this data: We ingest EPA Water Quality Portal samples from the June-September index period — chlorophyll-a, total phosphorus, total nitrogen, turbidity, true colour and Secchi depth — and grade each lake against the condition thresholds EPA publishes for its ecoregion in the National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3). Those thresholds are the 75th and 95th percentiles of least-disturbed reference lakes within each ecoregion, so a lake is compared with its own regional peers rather than a national average. Chlorophyll-a is the primary indicator because it measures algal biomass directly; phosphorus and nitrogen are the causal drivers. Water clarity is NOT graded — EPA assigns no condition class to Secchi depth, and low clarity is either redundant with chlorophyll-a or caused by natural dissolved colour or suspended sediment. We report clarity and explain what is driving it. Full thresholds, the composite rule, and the sampling a grade requires are all on our methodology page.

Refresh cadence: Refreshed every four months as new state-agency samples are pushed to the EPA Water Quality Portal. Ice-out observations, fish-species records, and invasive-species listings refresh on the cadence each state’s DNR publishes them — typically annually for ice data and quarterly for invasive-waters updates.

Known limitations of this source: A lake only receives a letter when the monitoring record supports one. Where it does not, we publish the measurements with an explicit reason and no grade — this is EPA Integrated Reporting Category 3, insufficient information, and it is not a failing grade. Every grade carries a confidence level; only high-confidence grades are used in rankings and comparisons. The grade covers nutrients and algae. It does NOT cover mercury, PFAS, bacteria or other contaminants, so it is not a swimming or fish-consumption clearance — check your state environmental and health agencies for current advisories. Ecoregion boundaries are a classification, not a wall: two lakes with similar chemistry on opposite sides of one can receive different letters. Sample timing matters, and depth figures marked as estimates are model output rather than survey measurements.

No warranties

lakequality.org is provided on an "as is" and "as available" basis, without warranty of any kind, either express or implied, including but not limited to warranties of merchantability, fitness for a particular purpose, non-infringement, or course of performance.

No professional relationship

Reading, using, linking to, or sharing lakequality.org does not create any advisor-client, attorney-client, doctor-patient, or fiduciary relationship between you and LakeQuality or its operators.

Third-party links and affiliate disclosure

lakequality.org is free to read and is supported by display advertising served by third parties. It contains links to third-party websites, and some outbound links may be affiliate links — if you buy through them we may earn a commission at no extra cost to you, always disclosed where it applies. We do not endorse, control, or assume responsibility for the content, products, services, or practices of any third party. Following a link is at your own risk, and a commission never changes our editorial judgment.

Rankings and scores

Any rankings, grades, or composite scores published on lakequality.org are editorial opinions derived from public data using documented methodologies. They are not professional certifications, accreditations, or endorsements, and they are not a substitute for independent due diligence.

Limitation of liability

In no event will LakeQuality, its operators, contributors, or data providers be liable for any loss or damage — including, without limitation, indirect, incidental, consequential, or punitive damages, or any loss of profits, data, or goodwill — arising out of or in connection with the use of lakequality.org or reliance on any information it contains.

External sites

When lakequality.org links out to government agencies, research organizations, or news publications, those external sites are governed by their own terms and privacy policies. LakeQuality is not responsible for their content or practices.

Changes to this disclaimer

We may update this disclaimer at any time. Continued use of lakequality.org after changes are posted constitutes acceptance of the updated disclaimer. The "Last updated" date above reflects the most recent revision.

Contact

Questions about this disclaimer or a specific page? contact@lakequality.org.