Fact-Checking Policy
Last updated: June 2026
Every number on lakequality.org is meant to be traceable to a primary public record. This policy describes where our facts come from and how we check them before they are published.
Primary sources only
LakeQuality builds its pages from the EPA Water Quality Portal, the Minnesota DNR LakeFinder, and the Wisconsin DNR Surface Water dataset. We do not republish second-hand summaries, scraped aggregations, or unattributed figures. Each page cites the dataset it draws from and links back to the source so any reader can verify a figure independently.
No invented numbers, no synthetic data
If a value is not present in the underlying public data, it does not appear on lakequality.org. We never fabricate statistics to fill a gap, and we never use model-generated estimates in place of reported figures. Where the data is genuinely missing, we say so rather than guess.
How figures are verified
- Faithful processing. Data is fetched directly from the source, then transformed with documented, repeatable code — not hand-transcribed, where transcription errors would creep in.
- Source-of-truth checks. Derived values (rankings, grades, composite scores) are computed from the source fields using stated formulas, so the inputs to any number remain auditable. 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 evidence bar are on our /methodology page.
- Sanity bounds. Cross-cutting totals and outliers are checked against known ranges to catch unit errors, duplicates, and mis-scaled values before they reach a page.
- Dating. Every dataset page carries a “Last updated” date so readers know how current a figure is.
The limits of what we check
LakeQuality verifies that our pages faithfully represent the EPA Water Quality Portal, the Minnesota DNR LakeFinder, and the Wisconsin DNR Surface Water dataset. We do not independently audit the issuing agency’s collection methods, and we cannot guarantee the source itself is free of error. Source records may be incomplete, reported late, or restated after publication. We treat the primary record as authoritative and follow its corrections — always verify a consequential figure against the original source before acting on it.
Found an error?
Tell us and we will fix it. See our Corrections Policy for how to report an issue and what happens next, and our Editorial Policy for how our content is produced.