> 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-technical-specification/code-lists-and-enumerations/hydronodecategoryvalue.md).

# HydroNodeCategoryValue

## **Code list: HydroNodeCategoryValue**

Classification value defining the type of hydrographic node.

| Code             | Description                                                                                                                                                                                                                                                                         |
| ---------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| flowConstriction | A split in the network captured to indicate a hydrographic point of interest or facility, or a man-made object that affects the network flow. This attribute is not manifested in this release of the data; however, it will be utilised in future data updates.                    |
| flowRegulation   | A split in the network captured to indicate a man-made object that is used to regulate the network flow. This value is not currently supplied.                                                                                                                                      |
| junction         | A split in the network to indicate where three or more WatercourseLink features meet at the same level, for example, confluences or bifurcations.                                                                                                                                   |
| outlet           | The end terminal of a set of one or more interconnected links that does not have any downstream flow, for example, where a watercourse sinks into the ground or the point where a river enters the sea.                                                                             |
| source           | The start terminal of a set of one or more interconnected links that has downstream flow, for example, springs or collects.                                                                                                                                                         |
| pseudo           | A location where the real-world attribution of a watercourse changes that requires a WatercourseLink to be split.                                                                                                                                                                   |
| boundary         | <p>HydroNode used to connect different networks.</p><p><em>Note: Can be used to connect cross border networks or adjacent networks together. Differs from source / outlet in that in the real world there is an adjacent link that is not present in the dataset supplied.</em></p> |

Where the hydroNodeCategory has not been determined, this attribute is set to null and the value of nilReason is set to ‘unknown’.


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