Water Stewardship Information Sources

Citation Caslys Consulting Ltd. 2009. Freshwater Water Atlas User Guide. Prepared for GeoBC.
Organization GeoBC
URL http://geobc.gov.bc.ca/base-mapping/atlas/fwa/docs/Freshwater_Atlas_User_Guide_Sept2009.pdf
Abstract/Description or Keywords The Freshwater Atlas is a standardized dataset that seamlessly maps the province’s hydrological features. It
represents a significant improvement over the previous 1:50,000 scale Watershed Atlas because it is derived
from the province’s more detailed 1:20,000 scale topographic base maps – the Terrain Resource Information
Management (TRIM) series. The atlas defines watershed boundaries by height of land and provides a connected
network of streams, lakes and wetlands, linking each stream to the other streams and watersheds it flows to
and from. This connected network defines stream systems – stream tributaries flow from a stream headwater to
a mouth located on either another stream or some other waterbody (e.g., a lake or the ocean). Simply put, you
could, conceptually, launch a paper boat in the headwaters of a small creek in the interior and trace its route to
the sea. You could also identify all the wetlands, lakes and watersheds your boat passed through.
An attribute (or code) assigned to each tributary specifies a hierarchy that maintains stream connectivity and
defines upstream and downstream locations relative to the other tributaries and hydrological features in the
system. In addition, the relative position information allows the direction of flow to be identified, allowing
upstream and downstream flow to be mapped. The code for a tributary is the code of the receiving stream,
concatenated with a number indicating the distance upstream along the receiving stream from its mouth.
Every tributary of a stream is associated with a unique watershed and therefore the key is called the Watershed
Code. The same Watershed Code is assigned to both the stream tributary and the watershed it falls within,
allowing the streams to be related to the land base. The Freshwater Atlas consists of over three million
watersheds with an average area of 30 hectares.
A watershed is the drainage area associated with a single stream (a first-order watershed) or a stream system (a
higher-order watershed). The Watershed Code attribute facilitates the division of the province into both major
and minor drainage basins. Major drainages are subsequently divided into a hierarchy of watersheds. The atlas
is capable of identifying and mapping the lower-order watersheds contained within a higher-order watershed
or within a major drainage. The various hydrological features (e.g., lakes, wetlands, rivers, streams and
obstructions) are all linked to one another and the watershed they fall within through the coding system. This
capability allows drainage networks of varying scales to be mapped and the land base associated with them to
be identified. In addition, the atlas stores the names of many water features.
As a convenience for downloading the information, the various data layers in the Freshwater Atlas have been
grouped into contiguous collections of watersheds. These groupings are called Watershed Groups. Figure 1
details the extent of a major drainage – the Thompson River and illustrates some of the feature types in the
atlas.
Information Type report, mapping
Regional Watershed Province
Sub-watershed if known
Aquifer #
Comments
Project status complete
Contact Name
Contact Email