National Hydro Network (NHN)


Preview of NHN Data in ArcMap softwareThe National Hydro Network (NHN), for which the standard was officially adopted by the Canadian Council on Geomatics (CCOG) in August 2004, focuses on providing a quality geometric description and a set of basic attributes describing Canada's inland surface waters. It provides geospatial vector data describing hydrographic features such as lakes, reservoirs, rivers, streams, canals, islands, obstacles (e.g. waterfalls, rapids, rocks in water) and constructions (e.g. dams, wharves, dikes), as well as a linear drainage network and the toponymic information (geographical names) associated to hydrography.

The NHN forms the hydrographic layer of the GeoBase. The best available federal and provincial/territorial data are used for its production, which is done jointly by the federal government and interested provincial and territorial partners.

The modeling work of the NHN is based in part on Linear referencing System (LRS) concepts. This approach allows the management of geometric representations separately from attribute information (referred to as events in LRS). Unique identifiers (called National Identifiers - NID), associated to each NHN feature, allow for efficient management of updates. The NHN is a vector, topographic data product primarily designed to allow hydrographic network analysis. It is intented for water flow analysis, water and watershed management, environmental and hydrographical applications, as well as for a multitude of cartographic applications.

For more information on the NHN, you may refer to the following links:


NHN Standard (conceptual description)

For more information on the official National Hydro Network Standard approved by the CCOG in August 2004, you may refer to the following documents:

  • National Hydro Network, Canada, Level 1, Product Specifications, Edition 1.0, 2004-08 [pdf 109 KB]
  • National Hydro Network, Canada, Level 1, Data Model, Edition 1.0, 2004-08 [pdf 89 KB]
  • National Hydro Network, Canada, Level 1, Linear Referencing System (LRS), Data Catalogue, Edition 1.0, 2004-08 [pdf 605 KB]

NHN Product (data description)

For more information on the National Hydro network distribution profile, you may refer to the following documents:

National Vector Data

In GeoBase, documents found under the "National Vector Data" (NVD) label describe concepts which are potentially common to GeoBase vector products. The following document applies to the NHN:

  • National Vector Data - Identification Rules, Edition 2.0, 2007-04 [pdf 44 KB]


For a complete description of NHN product metadata, refer to the National Hydro Network Collection Metadata. Dataset Metadata are also provided with each NHN dataset distributed per NHN Work Unit via XML and HTML file formats. See Download section. For information about NHN Object Metadata, refer to the NHN Feature Catalogue - Distribution Profile above.

Use and Restrictions

Use of the GeoBase data is subject to the Open Government Licence – Canada.

Data Formats

NHN datasets are available in ESRI File GeoDatbase, GML (Geography Markup Language) and ESRI Shapefiles.

A subset of NHN datasets is also distributed in the KMZ format, which is a compressed version of the KML (Keyhole Markup Language) format. This format allows for displaying NHN data using software such as Google Earth and Google Map. For the KMZ format, it should be noted that large size NHN datasets are divided into quadrants. They are split into four smaller files in order to be acceptable to the Google Earth application. A resulting KMZ file from such a division may nevertheless still happen to be too heavy for the Google Earth application.

Image maps are also available in Portable Document Format (PDF). They are created from NHN work units (drainage areas), a subset of NHN data and the Canadian Digital Elevation Data. They also contain names information to allow to position oneself and the water flow direction is symbolized by arrows. It thus becomes easy to view and to print the hydrographic data contained in a drainage area. Image maps are datasets available in May 2010. They provide easy way to view and print hydrographic data contained in a drainage area.

Note: Some image maps may contain some shortcomings. For example, the water flow direction represented by arrows may be missing where the hydrographic network is dense. In addition they have been designed to be printed on a plotter 42 " wide. Since the width has been set, the length then becomes variable which makes some files too long to be printed at their planned level of details. This PDF format will be improved in future releases.

For more information on National Hydro Network data distribution formats, you may refer to the following document:

  • National Hydro network, Product Distribution Formats, Edition 1.0.3, 2010-05-17 [pdf 122 KB]

Free Data Viewers

Following are few links to freeware which can be used to display downloaded NHN data.

Preview of NHN Data in Google Earth software