OS MasterMap Water Network Layer Overview

This overview introduces OS MasterMap Water Network Layer and gives context for all users – highlighting key features, providing examples of uses, and listing details such as file sizes, etc.

Product has reached its End of Life (withdrawal) date

The OS MasterMap Water Network Layer product (also referred to as OS MasterMap Networks – Water Layer) reached its End of Life on 31 March 2026. As of this date, Ordnance Survey ceased to maintain or publish updates to the product, and access to the product was removed from the OS Data Hub, OS Features API and OS Vector Tile API.

Supporting product documentation will be removed from this site 12 months after this date, when access to existing data packages in the OS Data Hub is no longer available. Full details, including migration information and FAQs, are available on the OS MasterMap Water Network Layer End of Life information page.

OS MasterMap Water Network Layer is a three-dimensional digital representation of Great Britain's watercourses. The product includes rivers, streams, lakes, lochs and canals as a series of watercourse network lines. The network lines (links) are attributed to provide a range of information about the section of watercourse they depict. OS MasterMap Water Network Layer will significantly enhance systems used to manage waterways and rivers and the flood risk they pose.

Example extract from OS MasterMap Water Network Layer showing WatercourseLink and HydroNode features.

Watercourses that are underground or below structures are included where Ordnance Survey capture processes or accepted sources can infer the connection.

Polygons and lines representing the water area and its banks are not supplied in this product but will continue to be maintained and supplied as part of the OS MasterMap Topography Layer product.

OS MasterMap Water Network Layer is provided with three-dimensional coordinates.

Key features of the product

The OS MasterMap Water Network Layer product includes the following key features:

• Flow and connectivity.

• Three-dimensional geometry.

• Catchment information including name.

• The names of watercourses, including language alternatives.

• Vertical relationships where water courses pass over or under one other.

• Average widths.

• Additional information provided by national authorities.

Product applications

OS MasterMap Water Network Layer supports a wide range of customer applications that use geographic information. The product can be used alone or in combination with other Ordnance Survey products, such as OS MasterMap Topography Layer, OS MasterMap Imagery Layer and OS Terrain 5.

The OS MasterMap Water Network Layer product can be used for applications such as:

• Understanding flood risk

• Flood risk mitigation planning

• Flood response planning and execution

• Detailed flood modelling for insurance and land and property

• Environmental impact analysis

• Tracking water flows and any contamination

• Asset management and protection

• The management of statutory directives relating to watercourses

• Ecology studies, for example, species migration

• Analytics and visual interpretation, particularly when used in combination with other Ordnance Survey products, for example, OS Terrain 5

Index

This overview includes the following sections:

• Feature types in the product

• Standards and CRS

• Product supply