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Data Products and Interpolation

Oak Ridges Moraine Groundwater Program

Sub-watershed Characterization

Sub-watershed Delineation

The 3 million hectare ORMGP jurisdiction has been subdivided into thousands of ~10km² sub-watersheds as a basis for hydrometeorological data analysis. Every sub-watershed has a defined topological order in which headwater sub-watersheds can easily be mapped to subsequent downstream sub-watersheds, and so on until feeding the great lakes. The intent here is to make these sub-watersheds a “logical unit” for climatological and water budget analyses. Below is a description of the derivation the v.2023 OWRC 10km² sub-watershed map and its derivatives.

click on a subwatershed:

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Build v.2023

The sub-watershed delineation has expanded to include the entire Canadian Lake Ontario shoreline.

Build v.2020

The Provincial Digital Elevation Model (DEM) has been processed into a “hydrologically-correct” digital elevation model of the ORMGP ground surface. From this information, the ORMGP region is portioned into 2,813 ~10km² sub-watersheds.


The hydrologically-corrected digital elevation model (HDEM) is further process to derive a number of metrics aggregated at the sub-watershed scale. An overlay analysis was performed to characterize the sub-watersheds, including:


The ORMGP jurisdiction discretized into ~3000 ~10km² sub-watersheds. Below is an interactive map whereby Clicking at any sub-watershed will return a number of properties. In the figure below, sub-watersheds are colour-coded according to their degree of impervious cover, for instance.

Source Data

Sub watershed shapefile: owrc20-50a_SWS10-final.geojson