A vector representation of stream networks is a crucial dataset for the modelling the surface water and groundwater components of the hydrologic cycle. For many usages a crucial attribute of the drainage network is a digital topology and hierarchal stream order attribute (e.g., Strahler stream order). In Canada jurisdictional stream networks are available for the provinces and territories and nationally for Canada in the National Hydrological Network (NHN) dataset. Unfortunately, the NHN data lacks the same topological and attribute information that is available for numerous provinces due to standardization for the entire country. For Canada1Water it was also necessary to have a harmonized dataset with the United States, for both the southern transboundary watersheds and the Alaskan watersheds. This report documents the processes completed to upgrade the topological and graph network support for NHN and provide continuous connectivity with US datasets. It also highlights and corrects a number of stream density and stream order issues that occur within Canada across provincial and territorial borders and NTS tiles. All vector processing was completed in RivEX software extension for ArcMap. Following complete topological correction stream classification was assigned and a table of the node graph network developed. Additional work was then completed to normalize stream density particularly amongst low-order streams between British Columbia and the Yukon and amongst local NTS tiles in Quebec and Ontario. Corrected NHN Strahler stream order assignment was validated against a number of provincial and watershed datasets, all of which already have Strahler stream order attributed. These datasets are the same underlying digitized vector data, so there are no differences in node or polyline positions. Strahler stream order assignment validation was only done by visual comparison as due to differences in vector segments a statistical comparison is complicated. The transboundary integrated C1W stream network with complete classification provides a seamless national dataset to support transdisciplinary studies (fisheries, wildlife, health, pesticide and nutrient issues, mining impact, ecosystem restoration, numeric modelling) that involve a knowledge of stream distribution and ranking.

Please note that a web service is currently under development and will be launched in the fall of 2025. Stay on the lookout! ## #Avertissement :### ### #Le broadcaster cannot guarantee the accuracy, precision, or completeness of the data nor can it be held responsible for the conclusions that arise from their use. This data has no legal value. #### The Geobase of the Quebec Hydrographic Network at High Resolution (GRHQ-HR) offers an up-to-date representation of the hydrographic network with very high precision (scale of 1/2,000). This repository, produced from lidar data, is offered by hydrographic division unit (UDH). The deployment of this geobase is carried out progressively by levels of completeness (NC). Ultimately, it will cover the territory of southern Quebec. During the deployment phase of the repository, [the Quebec Hydrographic Network Geobase (GRHQ)] (https://www.donneesquebec.ca/recherche/fr/dataset/grhq), the GRHQ-HR as well as [potential flow beds] (https://www.donneesquebec.ca/recherche/dataset/lits-d-ecoulements-potentiels-issus-du-lidar) from the lidar will be simultaneously available on Data Quebec for this portion of the territory. The GRHQ-HR includes a 3D linear geometric network, which represents the continuity and direction of flow in all types of aquatic entities (streams, lakes, wetlands, etc.). This network is created by modeling potential flow beds and completed by central flow lines (simplified representation of hydrographic surfaces in central lines). This geobase is part of a strategy to update the cartographic map of Quebec's hydrography. It was carried out in partnership with the Ministry of the Environment, the Fight against Climate Change, Wildlife and Parks (MELCCFP). # #Caractéristiques UDH completion levels## Each level of completeness characterizes the level of work, editing, validation, and descriptive content of the datasets. Thematic and toponymic data will enhance the datasets. ### #NC -1 (primary geometric network) #### * Potential and filamentary flow beds derived from hydrographic, oriented, and topological surfaces. * Priority level defined (allows network analyses). * Presence of certain basic attributes (sustainability, network connection, accumulation of flows, Strahler and Horton orders, distance from upstream, distance from downstream). * Linear reference system (road numbers, vertex M coordinates). * Hydrographic surfaces of the GRHQ on a scale of 1/20,000 (2D). * Presence of some toponyms as an attribute. * Hydrocoherent digital terrain models (GeoTIFF). * Flow accumulation matrices (GeoTIFF). * Flow direction matrices (GeoTIFF). ### #NC -2 (enhanced geometric network) #### * NC-1 features. * Update of hydrographic surfaces by photogrammetry. * Correction of errors in the path of potential flow beds and update of downstream filamentaries. * Partial addition of thematic hydrographic data (dams, falls, reefs, islands, wetlands, rapids). * Lidar survey date index. * Topological nesting of matrices. * Update of hydrocoherent numerical terrain models. * Update of flow direction matrices. * Update of flow accumulation matrices. ### #NC -3 (thematic bonus) #### * Characteristics of the NC-2. * Hydrographic themes completed (breakwaters, quays). * Addition of toponyms. ### #NC -4 (improvement of toponymic content) #### * NC-3 features. * Continuity of toponymic data on geometries. * Addition of named entities. **This third party metadata element was translated using an automated translation tool (Amazon Translate).**