This dataset is part of Integrated Hydrometric Units (IHU) of the UK. Hydrometric Areas are used to organise river flow measurement and hydrometric data collection in the UK. Hydrometric Areas are either integral river catchments having one or more outlets to the sea or tidal estuary, or they may include several contiguous river catchments having topographical similarity but separate tidal outlets. In mainland Britain they are numbered from 1 to 97 in clockwise order around...