© Crown copyright and database rights 2025 Ordnance Survey 0100031673

OS NGD Water Theme comprises two ‘collections’ (Water Network and Water Features) which in turn provide geometry, feature classification and other attribution for nine feature types.

The NGD Water Network collection provides a three-dimensional structured link and node network of watercourses in Great Britain along with water features depicted by a line rather than polygon geometry:

  - Water Link Feature: represents the alignment and connectivity of permanent water (including inland rivers, tidal water, lakes, canals) with flow direction and catchment name.

  - Water Link Set Feature: represents named bodies of water that the water network flows through as single geometry for a complete named watercourse. Includes a cross reference table, referencing the Water Link Set back to Water Links.

  - Water Node Feature: depicts the location where a connected area of permanent water ends, where an area of permanent water is connected to two or more other areas of permanent water, or where a recorded attribute changes for an area of permanent water.


NGD Water Features includes watercourses, lakes, drains, springs and intertidal watercourses:

- River Basin District Catchment Feature: define river basin(s) together with coastal waters, as published by national water bodies. Main unit for management of river basins under the Water Framework Directive (NB. Water Environment and Water Services Act in Scotland).

- Waterbody Catchment Feature: represent surface water being the whole (or part) of a stream, river, canal, lake or reservoir as published by national water bodies.

- Water Feature: polygons representing areas of water larger than 8 square metres, with classifications for land cover and land use (including National Land Use Database NLUD codes).

- Water Point Feature: areas of water smaller than 8 square metres (e.g. a waterfall).

- Inter Tidal Line Feature: represent watercourses that extend across the inter tidal zone (e.g. rivers, streams, stream that diverge into multiple courses into marsh, sand).

- Tidal Boundary Feature: show the alignment of the limit of tidal water at specific states of the tide

OS NGD Water Theme is intended to enhance systems used to manage the flood hazard posed by waterways and rivers. It can be used to undertake analysis and visual interpretation or to display bodies of water and water catchments as a backdrop map. Unique identifiers, including Ordnance Survey ID (OSID) and Topographic identifier (TOID) enable data linking and analysis.