Daily mean river flow, a.k.a. gauged daily flows (GDF), measured at over 1500 points on the river network across Great Britain and Northern Ireland. Most stations are managed by the Measuring Authorities (Environment Agency, Scottish Environmental Protection Agency, Natural Resources Wales and the Rivers Agency of Northern Ireland), and the daily flows are generally the average of the raw 15 minute series. GDF values are expressed as cubic metres per second (abbreviated to m3s-1 and sometimes also referred to as cumecs) in a water-day (09.00 to 09.00 GMT) or, where indicated, a calendar day. The National River Flow Archive also holds detailed information about river gauging stations and their catchments.
Gaugin stations are operated by the measuring authorities, which include the Environment Agency (EA), the Scottish Environment Protection Agency (SEPA), Natural Resources Wales and the Northern Ireland Rivers Agency. Measuring authorities typically calculate river flows on the basis of measurements at 15-minute intervals. These high resolution data are used to calculate the mean gauged daily flow. These mean daily data are submitted to the National River Flow Archive (NRFA), which quality controls and archive the data.