Data and methods

Where the numbers come from, how they were cleaned, and the problems found in the volunteer data along the way.

How clean the data is83,297 of 88,511 records (94%) are usable after removing undated, deleted and duplicate surveys. Context Water temperature switches unitsThe Hub stores no temperature unit; chapter readings switch from °C to °F in 2012, and 83 readings nationwide needed converting. Context Sources and methodsBuilt from a Clean Water Hub snapshot of 2026-10-27, with public land-cover and weather data. Context DownloadsWatershed-level figures and every finding, free to download. Context