OS MasterMap Water Network Layer
Here you will find all documentation for the OS MasterMap Water Network Layer product.
Product nearing its End of Life (withdrawal) date
The OS MasterMap Water Network Layer product (also referred to as OS MasterMap Networks – Water Layer) will become End of Life on 31 March 2026. As of this date, Ordnance Survey will cease to maintain or publish updates, and access to the product will be removed from the OS Data Hub, OS Features API and OS Vector Tile API.
Further information and details about the recommended product migration pathway are available on the End of Life Notice – OS MasterMap Water Network Layer 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.
Compatible with other layers of OS MasterMap
OS MasterMap Water Network Layer is fully interoperable with all existing layers of OS MasterMap, and enables a new generation of analysis, policy development and environmental reporting.
Content and context
With this water network data, you can look up the height of any watercourse, along with its flow direction, gradient, length and width anywhere along its length.
Precise watercourses details
As an island, water defines Great Britain. No other visualisation of our nation’s watercourses details the heights of watercourses in relation to sea level with this level of precision.
Complete picture in 2D and 3D
For planners, for surveyors, for engineers – this layer offers the potential to model in 2D and 3D like never before, thanks to the clarity of river flow, gradient and river widths.
Answers on tap
From aqueducts to tunnels, with annotations of flow direction, OS MasterMap Water Network Layer provides useful detailed mapping that includes underground watercourses (inferred from entry and exits).
Detailed centre line
OS MasterMap Water Network Layer provides a detailed centre line following the curve of the waterway precisely. It includes the coordinates of watercourse sources and where they meet, exactly.
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)
Access: Download
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
Please note that the January 2026 release will be 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 End of Life Notice – OS MasterMap Water Network Layer 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 ESPG 7405 OSGB36 / British National Grid + ODN. This projection is used as it specifies that the Z value is Ordnance Datum Newlyn.
How to get this product
Access to this product is free for PSGA (Public Sector Geospatial Agreement) Members. You can check if your organisation is a member of the PSGA on the OS website.
The OS MasterMap Water Network Layer product page on the OS website has advice on how to get the product for businesses, developers, OS Partners and PSGA Members (i.e. government and the public sector).
Sample data
Download OS MasterMap Water Network Layer sample data
You can download sample data for the product for free from the OS Data Hub. The sample data is available in GML 3.2 format and covers one area (Exeter).
Visualise OS MasterMap Water Network Layer sample data online
This product is available to try out free online using one of our three sets of sample data (Exeter, Newport and Inverness) through the OS MasterMap Product Viewer:
Other ways to access this data
OS MasterMap Water Network Layer data is available from our OS Features API, providing location-based insights combining topography data with buildings, transport, and water layer data to create finely detailed datasets with a high degree of accuracy. Visit the OS API docs site to unlock programmatic access to rich geospatial data and integrate OS data and services into your applications.
Access to OS MasterMap Water Network Layer data is also available through the OS NGD Water Theme, providing a three-dimensional structured link and note network of watercourses for Great Britain. Users may find that OS NGD Water Theme data is more accessible, contains greater attribution, and is easier to use with databases and GIS software. Visit the OS NGD docs site to discover how to access the OS NGD and learn what's available to users.
What's next?
To access additional documentation and resources relating to this product, please refer to the following:
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