Integrated Hydrological Units: UK River Catchment Hierarchy

Integrated Hydrological Units (IHU) define geographical reference units for hydrological purposes in the United Kingdom. The dataset comprises five hierarchical polygon layers: Hydrometric Areas (with and without coastline), Groups, Sections, and Catchments, representing different levels of spatial detail for river flow measurement and hydrometric data collection. The Hydrometric Areas layer covers Great Britain and Northern Ireland, while other layers currently cover only Great Britain.

Use Cases

• River flow measurement based on defined Hydrometric Areas.
• Hydrometric data collection and reporting based on standardized geographical units.
• Catchment modeling and analysis based on the hierarchical Sections and Catchments layers.
• Mapping hydrological reference units based on named Groups constructed from river and county names.

Strengths

• Provides a structured, hierarchical spatial framework with five distinct layers for hydrological analysis.
• Polygons within each layer are designed to have no gaps, and most layers do not overlap, ensuring clear spatial units.
• Available as a web map service (WMS) on multiple platforms, indicating established utility.

Limitations

• Column names and specific attribute data are unknown from the provided sources.
• Most layers (Groups, Sections, Catchments) cover only Great Britain, excluding Northern Ireland due to lack of detailed river data.
• The 'last updated' metadata conflicts: one source lists 2026-07-02, another lists none.

Provenance

Source

Environmental Information Data Centre

Freshness

2026-07-02 19:10:56.782776

Geography

Great Britain and Northern Ireland (for Hydrometric Areas with Coastline); Great Britain only (for other layers)