{"id":"england-river-flow","slug":"england-river-flow","name":"England River Flow Dataset","description":"Monthly and annual mean river flow for long-record gauging stations in England, aggregated from the Environment Agency’s quality-controlled daily record. The Thames at Kingston runs from October 1883.","methodology":"Daily mean flows are read from the Environment Agency Hydrology Data Explorer and aggregated by Hydrionis to monthly means, then to annual means from those monthly values rather than from daily values directly — averaging days would weight a year toward its best-observed months. A month is published only where readings covering at least 80% of its days passed the Environment Agency’s quality control; readings flagged Suspect, Missing or Unchecked are excluded and counted. Only stations whose record opens before 1970 are collected, because the value of this dataset is depth of history.","domains":["river-flow"],"metricIds":["river-flow-mean","river-flow-monthly-mean"],"subjectScope":"English gauging stations with a record opening before 1970","cadence":"monthly","version":"1.0.0","released":"2026-08-24","changelog":[{"version":"1.0.0","date":"2026-08-24","summary":"First release.","additions":["Monthly and annual mean flow for 356 long-record English gauging stations."]}],"limitations":["Flow is a property of a gauge on a reach, not of a river. Two gauges on the same river can differ by an order of magnitude and neither describes the river as a whole.","Values are affected by abstraction and discharge upstream, so a record measures what reached the gauge rather than what fell on the catchment.","Recent months are absent until the Environment Agency has quality-checked them; provisional readings are not published.","Gauge ratings are revised over time, and a long record may contain breaks where structures were rebuilt."],"observationCount":255739,"seriesCount":711,"subjectCount":356,"from":1879,"to":2026,"sourceIds":["uk-ea-hydrology"],"units":["m³/s"],"redistributable":true,"commerciallyReusable":true,"citation":"Hydrionis (2026), England River Flow Dataset, version 1.0.0. Retrieved from https://hydrionis.com/data/datasets/england-river-flow/","downloads":[{"file":"/downloads/observations-river-flow-uk-ea-hydrology.csv","format":"CSV","label":"river-flow observations from EA (261,070 rows)"}],"apiPath":"/api/v1/datasets/england-river-flow.json","lastFetched":"2026-10-01","fields":[{"id":"river-flow-mean","name":"Mean river flow","definition":"Average volumetric discharge past a gauging station over a stated period.","unit":"m³/s","nativeGeography":["river-gauge"],"comparabilityNotes":"Flow is a property of a specific gauge on a specific reach, and cannot be attributed to a river as a whole. Two gauges on the same river can differ by an order of magnitude. Where a station measures flow through a sluice, lock or pumping station — much of the Dutch network does — discharge is signed and a negative value means water moving in the reverse direction, which is a real operating state and not an error. Managed flow of that kind is not comparable with discharge at a natural gauging station, because it reflects operational decisions as well as hydrology."},{"id":"river-flow-monthly-mean","name":"Mean monthly river flow","definition":"Average volumetric discharge past a gauging station over a calendar month.","unit":"m³/s","nativeGeography":["river-gauge"],"comparabilityNotes":"A gauge property, not a river property. Strongly seasonal, so compare a month against the same month in other years. Gauge records contain breaks where structures were rebuilt or ratings revised."}]}