OS MasterMap Water Network Layer

OS MasterMap Networks - Water Layer | Data Products | OSOrdnance Survey

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 Product Notices 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.

This product is updated quarterly in January, April, July and October.

OS MasterMap Water Network Layer map.

Features

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.

Summary

• 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

• OS Data Hub plan: Energy & Infrastructure Plan, Premium Plan, Public Sector Plan

Additional information

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.

Compatibility 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.

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 Public Sector Geospatial Agreement (PSGA) Members. Find out if you are a PSGA Member or download a sample of OS MasterMap Water Network Layer data by accessing the product page on the OS website, which has links to all of the relevant resources. Alternatively, you can try out the full product by applying for a Data Exploration license.

Visualise OS MasterMap Water Network Layer data online

This product is available to try out online using one of our three sets of sample data (Exeter, Newport and Inverness) through the OS MasterMap Product Viewer:

OS MasterMap Product Viewer

Interactive demonstrator of OS MasterMap Generation data

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. Find out more on our OS API platform, where you can unlock 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:

Overview

The 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.

Getting Started Guide

The getting started guide provides instructions for using OS MasterMap Water Network Layer in different applications. Users with limited technical knowledge will be able to follow this guide.

Technical Specification

The technical specification provides detailed technical information about OS MasterMap Water Network Layer. It is targeted at technical users and software developers.

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.