Spatial scale and hydrological model response
Date
1999
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
This thesis focuses on the effects of varying spatial scale on the numerical simulation of
hydrological processes. Specifically, it examines the impact of changing the number
and sizes of sub-basins on the performance of the SLURP hydrological model.
Automated watershed segmentation and parameterization was essential for this scaling
analysis. The TOPAZ digital landscape analysis model was used to process a raster
digital elevation model (DEM) to derive a wide range of topographic and topologic
variables that are physically meaningful to watershed runoff processes. TOPAZ
automatically subdivides a main watershed into a variable number of sub-basin units at
specified levels of detail or scale. The SLURPAZ interface was used to manipulate
relevant output data from TOPAZ along with land cover, routing and climate station
data to provide all the necessary inputs for the SLURP hydrological model. Results of
an application using these techniques is presented for a northern alpine basin (i.e. Wolf
Creek, Yukon, Canada).
A comparative analysis is presented from an earlier hydrological simulation, for which
the physiographic parameters were derived manually using a geographical information
system (GIS), with a hydrological simulation of the same scale, where the physiographic
parameters were derived automatically using the digital landscape analysis model,
TOPAZ, and the SLURPAZ interface. Generally, simulations from the hydrological
model, SLURP, are very similar when comparing the automated and manual runs. The
major benefits of using the automated segmentation parameterization techniques versus
the manual ones are the cost and time factors, and that the automated methods offer
rapid parameterization at several scales or levels of detail.
Several model runs, varying in scale from 1 to approximately 1600 sub-basins, are
discussed. Varying sub-basin scale showed interesting trends at two levels of detail.
First, as the number of Aggregated Simulation Areas (ASAs) increases, it is necessary to have a sufficient number of ASAs to allow variations in water balance components to be
adequately represented. Secondly, results suggest that with an increasing number of
sub-basins, accuracy of the hydrological model outputs tend to increase up to a certain
threshold. Thereafter, any further subdivision does not enhance model performance
significantly. Another comparison ensued where a short channel versus a long channel,
both for the whole basin as one ASA, in order to evaluate SLURP's 'within-ASA'
routing sensitivity. Additionally, the 'between-ASA' storage routing method was
evaluated by assessing the sensitivity of the Alpha and Beta routing parameters.
Optimal scales found in previous research from varying the size and number of subbasins
are also compared to those found in this research.
Automated parameterization allows for scaling studies to take place in a more rapid and
cost effective manner. SLURPAZ acts as a useful link between the SLURP
hydrological model and the TOPAZ digital landscape analysis model. Such tools offer
the benefits of speed, precision and reproducibility in drainage basin analyses.
Description
Keywords
Citation
Degree
Master of Science (M.Sc.)
Department
Geography
Program
Geography