OS MasterMap Water Network Layer Documentation
Here you will find all documentation for the OS MasterMap Water Network Layer product.
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.
Category: Networks
Data theme: Water
Data structure: Vector – Topologically structured link and node network
Coverage: Great Britain
Scale: 1:1 250 to 1:10 000
Format: GML 3.2.1, GeoPackage, vector tiles
Ordering area: All of Great Britain or customisable areas (5km² tiles)
Publication months: January, April, July, October
Product has now been withdrawn
Please note that the January 2026 release was the final release of OS MasterMap Water Network Layer; more information about the product withdrawal timeline and the recommended product migration pathway is available from the OS MasterMap Water Network Layer End of Life information page.
Feature types included
The feature types within the product are:
WatercourseLink: This feature represents the alignment of a watercourse. The majority have been derived from Ordnance Survey detailed topographic data, made available to customers as the OS MasterMap Topography Layer.
HydroNode: A HydroNode feature explicitly represents the start, the junctions and the end of each watercourse, as well as places where there's a change in the real-world-related attribution.
Spatial reference system
The OS MasterMap Water Network is projected in the EPSG 7405 OSGB36 / British National Grid + ODN. This projection is used as it specifies that the Z value is Ordnance Datum Newlyn.
Other ways to access this data
We recommend you migrate to using the data in the OS NGD Water Network Collection as it contains very similar data content to OS MasterMap Water Network Layer – see the Comparison of Water Network Products page for a full comparison of the data supply, available formats, and attribution between the two products.
Further details on migration, including benefits to using OS NGD Water Network Collection data, FAQs and supporting documentation are available from the OS MasterMap Water Network Layer End of Life information page.
OS MasterMap Water Network Layer documentation
To access additional documentation and resources relating to this product, please refer to the following:
New users should start with the Overview to gain high-level insight into the product. The Getting Started Guide will help you to begin using product data in different software systems. The Technical Specification contains detailed technical insights.
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