| Summary: | The suitability of using geographic information system (GIS) data to describe a watershed for
the UBC Watershed Model is investigated. A GIS combines the ability of a database
management system to store, retrieve, and analyse information with the capacity to produce
and manipulate graphical elements on a map. In hydrologic modeling, information from a
GIS is commonly used to describe the physical characteristics of a watershed such as terrain,
forest cover, and soil type. By using a GIS, possible sources of human error and subjectivity
present when manually measuring attributes from maps or aerial photographs can be
removed.
The Seymour Watershed located north of Vancouver, B.C. is used as an example in assessing
the value of GIS data for the watershed model and to illustrate the complexities of calibrating
the model. Terrain, ecological, and timber GIS databases for the Seymour Watershed are
used to create a watershed description file (WAT) which is implemented in the model to
produce synthetic watershed hydrographs. These hydrographs are then compared and
calibrated against recorded historical streamflows, resulting in a calibrated Seymour
Watershed model. This model is then used to forecast future streamflows when
meteorological forecasts are also provided.
Although GIS data is not perfect, it is valuable in describing a watershed as input for the
UBC Watershed Model, which is then used to produce calculated hydrographs. The main drawback of utilizing a GIS for the Seymour Watershed is the absence of adequate
documentation of some GIS characteristics. Despite the removal of subjectivity and human
error by using GIS data, inaccurate model streamflows remain due to errors in other non-GIS
data such as improper reservoir elevation readings, missing historical streamflow or
meteorological data, and inherent errors in the watershed modeling process.
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