> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-getting-started-guide.md).
# OS MasterMap Water Network Layer Getting Started Guide
This 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.
{% hint style="warning" %}
#### 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-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-end-of-life-information.md).
{% endhint %}
OS MasterMap Water Network Layer is a digital representation of the watercourses in Great Britain as a series of connected features. The data represents the approximate central alignment of watercourses and is attributed to provide a range of information about the section of watercourses they represent.
The product has two core feature types:
* **WatercourseLink:** A WatercourseLink 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 product](/os-downloads/products/maps-and-imagery-portfolio/os-mastermap-topography-layer.md).
* **HydroNode:** A HydroNode feature explicitly represents the start, junctions and end of each watercourse, as well as places where there's a change in the real-world-related attribution.
Example extract from OS MasterMap Water Network Layer showing WatercourseLink and HydroNode features.
{% hint style="info" %}
This Getting Started Guide focusses solely on using the product in Geography Markup Language (GML) format.
For guidance on using the product in GeoPackage or vector tiles formats, please see either the [Getting Started with GeoPackage guide](/os-downloads/resources/product-resources/getting-started-with-geopackage-and-vector-tiles-guides/getting-started-with-geopackage.md) or the [Getting Started with Vector Tiles guide](/os-downloads/resources/product-resources/getting-started-with-geopackage-and-vector-tiles-guides/getting-started-with-vector-tiles.md).
{% endhint %}
## Index
This guide includes the following sections:
* [Requirements for using the data](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-getting-started-guide/requirements-for-using-the-data.md)
* [Structure of the supplied data](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-getting-started-guide/structure-of-the-supplied-data.md)
* [Loading GML data into a GIS](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-getting-started-guide/loading-gml-data-into-a-gis.md)
* [Creating a water network using ESRI software](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-getting-started-guide/creating-a-water-network-using-esri-software.md)
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.
Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://docs.os.uk/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-getting-started-guide.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
