OS MasterMap Water Network

OS MasterMap® Water Network is the only detailed, heighted water network of Great Britain – showing the flow and precise course of every river, stream, lake and canal, at a national and local level. This product contains nationally consistent views of Great Britain's watercourses.


Since 2015, a collaboration between OS, Environment Agency (EA) and Scottish Environment Protection Agency (SEPA) has produced 850,000 improvements to this crucial dataset which focuses on watercourse connectivity, flow direction, contiguous naming and identified primary flow path.

The combination of OS MasterMap's Water Network and Topography Layer offers richer insights into water-related risks, property information and 3D height data. National coverage and clarity of river flow, widths and gradient offers the potential to model in 2D and 3D like never before.

OS and EA are delighted to confirm that EA will start to mitigate from their existing Detailed River Network to the OS MasterMap Water Network and will be progressively implementing this across all systems and projects where a network of watercourses is required.

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Answers on tap

With this government endorsed data, you can look up the height of any water course in Great Britain, along with its flow direction, gradient, length and width anywhere along its length. This also includes the location of culverted rivers.

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How far, how wide

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.

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Content and context

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.


Key featuresWhat this product offers

GML 3.2

Data structure

Vector – toplogically structured link and node network


Watercourse name, flow direction, gradient, primary flow, TOID® reference, EA or SEPA catchment name and ID


1:1250 – 1:10 000

Update frequency

Quarterly – April, July, October and January


DVD and download



OS MasterMap Water Network support ›


How is this data supplied and what do I need to use it?

Water Network is supplied on DVD or as a download.

You'll need geographic information system (GIS) software to use the data.

What spatial reference system does OS MasterMap Water Network use?

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.

Does OS Mastermap Water Network work with all the other layers of OS MasterMap?

Yes, it is fully interoperable with all existing layers of OS MasterMap and enables a new generation of analysis, policy development and environmental reporting.

What feature types does the product include?

The feature types within the product are:

  • WatercourseLink. This feature represents the alignment of a watercourse and 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. The nodes exist only at the end-points of a WatercourseLink feature.
See all FAQs for OS MasterMap Water Network ›


OS MasterMap Water Network is available under the following Licences:

Explore our data

You’re welcome to try out this data for free under our Data Exploration Licence.

Internal business use

When using OS data in your own business, you need our Framework Contract (Direct Customers) together with a data contract.

Creating products or services

To use this data commercially in your own products and services, or to distribute it, you will need to sign up to our Framework Contract (Partners) and a relevant defined use contract. This will vary depending on what you’re going to do with the data.

Collective mapping agreements

These products are available to members of public sector organisations under the following agreements:

Find out more in our Public sector licensing guide ›

This product is available under the:

  • Media Licence. We encourage the use of OS maps in the media – TV, films, print and online. Sign up free to give your consumers valuable context via an authoritative map.
  • Publishing licence. This is suitable for one-off publishing of maps in publications, on merchandising and websites.
View all licences ›

Case studies

Give it a try

Download a small area of OS MasterMap Water Network sample data

Or you can apply for a Data Exploration Licence to try out the real thing.

If you're in the public sector, this product is free of charge thanks to your mapping agreement.