Use this map to locate major river basins by Hydrometric Area number.
Source: NERC Institute of Hydrology (National River Flow Archive)

The designation of hydrometric areas is fundamental to the work of the National River Flow Archive, and is drawn upon in the annual publication of river flow data for rivers around the UK. Since 1996, the Yearbooks featuring these data have been published on the web, links are as follows:

These yearbooks also contain groundwater data for their respective years.
Link back to hydrochronology: