Articles | Volume 10, issue 5
Hydrol. Earth Syst. Sci., 10, 769–782, 2006
https://doi.org/10.5194/hess-10-769-2006
Hydrol. Earth Syst. Sci., 10, 769–782, 2006
https://doi.org/10.5194/hess-10-769-2006

  19 Oct 2006

19 Oct 2006

Investigation of dominant hydrological processes in a tropical catchment in a monsoonal climate via the downward approach

L. Montanari1, M. Sivapalan2,*, and A. Montanari1 L. Montanari et al.
  • 1DISTART, Faculty of Engineering, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
  • 2Departments of Geography and Civil {&} Environmental Engineering, University of Illinois at Urbana-Champaign, 220 Davenport Hall, 607 S. Mathews Avenue, Urbana, IL 61801, USA
  • *formerly at: Centre for Water Research, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia

Abstract. This study explores the dominant processes that may be responsible for the observed streamflow response in Seventeen Mile Creek, a tropical catchment located in a monsoonal climate in Northern Territory, Australia. The hydrology of this vast region of Australia is poorly understood due to the low level of information and gauging that are available. Any insights that can be gained from the few well gauged catchments that do exist can be valuable for predictions and water resource assessments in other poorly gauged or ungauged catchments in the region. To this end, the available rainfall and runoff data from Seventeen Mile Creek catchment are analyzed through the systematic and progressive development and testing of rainfall-runoff models of increasing complexity, by following the "downward" or "top-down" approach. This procedure resulted in a multiple bucket model (4 buckets in parallel). Modelling results suggest that the catchment's soils and the landscape in general have a high storage capacity, generating a significant fraction of delayed runoff, whereas saturation excess overland flow occurs only after heavy rainfall events. The sensitivity analyses carried out with the model with regard to soil depth and temporal rainfall variability revealed that total runoff from the catchment is more sensitive to rainfall variations than to soil depth variations, whereas the partitioning into individual components of runoff appears to be more influenced by soil depth variations. The catchment exhibits considerable inter-annual variability in runoff volumes and the greatest determinant of this variability turns out to be the seasonality of the climate, the timing of the wet season, and temporal patterns of the rainfall. The water balance is also affected by the underlying geology, nature of the soils and the landforms, and the type, density and dynamics of vegetation, although information pertaining to these is lacking.