This dataset is part of Integrated Hydrological Units (IHU) of the UK, a set of geographical reference units for hydrological purposes including river flow measurement and hydrometric data collection. This dataset was derived from the Integrated Hydrological Terrain Model. A Catchment represents the full area upstream from a Section outlet, which is a cell upstream of a confluence of two watercourses with known names. While Sections do not overlap, Catchments can overlap because one Catchment contains Catchments for all upstream Sections. This layer currently covers Great Britain only as no dataset with river geometries and names with suitable detail is available for Northern Ireland. Full details about this dataset can be found at https://doi.org/10.5285/10d419c8-8f65-4b85-a78a-3d6e0485fa1f

This dataset is part of Integrated Hydrological Units (IHU) of the UK, a set of geographical reference units for hydrological purposes including river flow measurement and hydrometric data collection. 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. Hydrometric Areas are the coarsest units of the IHU in terms of spatial resolution. This dataset represents the same entities as the Hydrometric Areas with Coastline. The coastline of Hydrometric Areas without Coastline follows the boundaries of the CEH Integrated Hydrological Digital Terrain Model, from which IHU were derived, while the coastline used in Hydrometric Areas with Coastline was derived from Ordnance Survey data. The Hydrometric Areas without Coastline currently covers Great Britain only as no dataset with river geometries and names with suitable detail is available for Northern Ireland. Full details about this dataset can be found at https://doi.org/10.5285/3a4e94fc-4c68-47eb-a217-adee2a6b02b3

This dataset is part of Integrated Hydrological Units (IHU) of the UK, a set of geographical reference units for hydrological purposes including river flow measurement and hydrometric data collection. Groups represent the intermediate units of IHU in terms of spatial resolution. The most common size of a group is around 400 square kilometres. Each Group carries a name constructed from names of the major river flowing through the Group, the major river flowing into the Group, the major river into which the Group flows, and sometimes also from local county names. Each Group consists of one or more Section and Groups can be combined to form Hydrometric Areas without Coastline. Identifiers and attributes have been calculated so that direct upstream and direct downstream IHU units can be selected. This layer currently covers Great Britain only as no dataset with river geometries and names with suitable detail is available for Northern Ireland. Full details about this dataset can be found at https://doi.org/10.5285/f1cd5e33-2633-4304-bbc2-b8d34711d902

This dataset is part of Integrated Hydrological Units (IHU) of the UK, a set of geographical reference units for hydrological purposes including river flow measurement and hydrometric data collection. A Section is the drainage area of a watercourse between two confluences. Only confluences of named watercourses were considered. Each Section carries a name constructed from names of the major river flowing through the Section, the major river flowing into the Section, and the major river into which the Section flows. Sections are spatially consistent with Groups: each Group is made up of one or more Section. Each Section is associated with one Catchment representing the full area upstream from the Section outlet. Identifiers and attributes have been calculated so that direct upstream and direct downstream IHU units can be selected. This layer currently covers Great Britain only as no dataset with river geometries and names with suitable detail is available for Northern Ireland. Full details about this dataset can be found at https://doi.org/10.5285/a6e37e39-9e10-4647-a110-12d902403095