Predictions
in Ungauged Basins: Promise and Progress (Proceedings of symposium S7 held during the
Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS
Publ. 303, 2006, 38-46.
Analysis of process controls on streamflow
response in an Australian tropical catchment
LAURA MONTANARI1, MURUGESU SIVAPALAN2 & ALBERTO MONTANARI1
1 Faculty of Engineering, University of Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy
laura.montanari@mail.ing.unibo.it
2 Department of Geography, University of Illinois at Urbana-Champaign, 220 Davenport Hall, MC-150, 607 South Mathews Avenue, Urbana, Illinois 61801, USA.
Abstract This study investigates the
dominant processes that may be responsible for the observed streamflow response
in the Seventeen Mile Creek, a tropical catchment of Northern Territory,
Australia. To achieve this, the available rainfall and runoff data from this
catchment are analysed through the systematic development of rainfall–runoff
models of appropriate complexity, by means of the “downward or top-down
approach”. We start with simple model constructs, and progressively increase
model complexity and improved process representation, and at each step of the
way, the predictions of the models are evaluated against signatures of observed
runoff variability, using standard measures of goodness of fit. This systematic
examination of observed streamflow variability leads to considerable physical
insights into the dominant process controls, and can be extremely valuable
towards the choice and development of models of appropriate complexity. The
results obtained from this modelling study show that the soils within the
catchment have a high storage capacity, which contributes to a significant
fraction of delayed runoff, whereas saturation excess overland flow occurs only
after heavy rainfall events during the wet season. Sensitivity analyses have
been conducted to determine the effects of interactions between soil depth and
temporal rainfall variability on the runoff regime. They show that on the one
hand the catchment total runoff is more sensitive to rainfall variations than to
soil variations, while on the other hand the runoff components appear more
influenced by soil depth changes.
Key
words bucket model; downward approach;
hydrological process; tropical catchment; ungauged basin