Scaling Up from Point Scale to Small Catchment Scale
Using a Quasi-Physical Approach
Narendra Kumar Tuteja1 and Conleth Cunnane2
Runoff forecasting in the case of seasonally snow-covered small catchments with shallow snowpack
requires application of a quasi-physical approach wherein the dominant snow accumulation and
melting processes are accounted for by an intensive physically based modeling approach, and trans-
formation of the snowmelt and the rainfall to streamflow is accounted for by a conceptual modeling
approach. In the case of shallow snowpacks both high and low water saturation can occur more
frequently and therefore the physically based distributed (in depth) snowmelt model must account
for capillary pressure gradients as well as gravity drainage. One such physically based snowmelt
model, entitled UCGVDSM, which accounts for coupled transport of mass and energy into the
snowpack, developed from the Eulerian principles, is first validated on point snowmelt data of sta-
tion Khtai located in Austria. UCGVDSM is then applied to the TichOrlice catchment (96.8 km2)
located in the Czech Republic. It is shown how the constraints of data availability for application of
the physically based snowmelt model can be handled to reproduce accurately the three state vari-
ables, namely, the snow water equivalent (SWE), the depth of snowpack (H), and the meltwater flux
(qmelt). The snowmelt rates thus obtained for the snowcover periods are then incorporated along
with the rainfall and the evapotranspiration data into the Soil Moisture Accounting and Routing
model (SMAR), a conceptual rainfall runoff model. It is shown that incorporating a number of curve
fitting techniques into the SMAR model have no effect on improving the model performance, while
accounting for physical processes improves the model performance. An updating component is
finally incorporated into the SMAR model to set up the small catchment scale hydrological forecast-
ing model.
1
Department of Engineering Hydrology, University College Galway, Ireland. Now at Department of Land
and Water Conservation, Wagga Wagga Research Centre, P.O. Box 5336, Wagga Wagga, NSW 2650
Australia
2 Department of Engineering Hydrology, University College Galway, Ireland
41
Previous Page
