Our colleagues in the National River Flow Archive (NRFA) have released a new, freely available dataset of spatial reference units for hydrological purposes, called "Integrated Hydrological Units of the United Kingdom". Filip Kral explains more:
"This dataset will aid hydrological analysis and water management in the UK by providing a consistent, nationwide framework for segregating river catchments into component parts. It also serves as a reference list of major river names and, by indicating which units are connected, it can be used to trace the flow of rivers across the country.
Researchers and organisations working to improve catchment management have already expressed interest in the dataset which we believe will become popular in the water industry and wider hydrological science community, thanks also to an open data licence.
Integrated Hydrological Units (IHU) of the United Kingdom (UK) consists of four polygon layers: Hydrometric Areas, Groups, Sections, and Catchments. Each layer represents a different level of spatial detail.
- The coarsest level, Hydrometric Areas, consists of more than 100 polygons corresponding to the spatial units used to organise river flow measurement and hydrometric data collection in the UK (for example, HA023 represents the Tyne in Northumberland).
- Each Hydrometric Area consists of one or more Groups (405 in total), which carry names derived from the major rivers flowing through, in, and out of each group, for example HA023G03 is Tyne (North Tyne to tidal limits) Northumberland.
- Each Group consists of even smaller units – Sections (more than 500,000 in total). A Section is the drainage area of a watercourse between two confluences, for example HA023G03S0024 is Tyne (Devil’s Water to March Burn).
- Each Section is associated with one Catchment representing the compound catchment upstream of the Section outflow point.
Historically, Hydrometric Areas were the primary reference units used by the NRFA to manage hydrometric data in the UK. IHU is a new release of the Hydrometric Area definition supplemented with finer scale units, all derived using the CEH Integrated Hydrological Terrain Model. Plans are being developed to utilise the IHU to help users explore other datasets produced by the NRFA and CEH’s Environmental Information Data Centre."