NRES Departmental Seminar by Dr. Murugesu Sivapalan, Professor of Geography and Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign.
Title: Parameterization of the Effects ofLandscape Heterogeneity on Integrated
Subsurface Runoff Response: A Reconciliation of Newtonian and Darwinian Approaches
Subsurface stormflow is an important component of the rainfall-runoff response in mountainous regions. However; its contribution is poorly represented in current generation of land surface hydrological (i.e. rainfall-runoff) models. The lack of physical basis of their common parameterizations precludes a priori estimation (i.e. without calibration), which is a major drawback for prediction in ungauged basins, or for their use in global models. This paper is aimed at deriv-ing universally applicable parameterizations of the storage-discharge relationship relating to subsurface flow from a combination of top-down (Darwinian) empirical data analysis and physically based (Newtonian) model simulations. Empirical analysis involved derivation of storage-discharge relationships from streamflow recession curves extracted from 50 eastern United States catchments. Detailed regression analyses were then performed between parameters of these empirical storage-discharge relationships and the controlling climate, soil and topographic characteristics. Param-eterizations of storage-discharge relationships were then independently derived through simulations with a physically based (Darcian) subsurface flow model for idealized three dimensional rectangular hillslopes, accounting for within-hillslope heterogeneity of soil hydraulic properties, which were subsequently up-scaled to the catchment scale by ac-counting for within-catchment heterogeneity of topographic slopes. These theoretical simulation results, as is to be ex-pected, showed that parameters of the storage-discharge relationship are governed predominantly by soil hydraulic properties and topographic slope alone, whereas the regressions derived from empirical recession curve analyses indi-cated that between catchment variability of same parameters are more strongly affected by climate, and less by field scale soil hydraulic properties themselves. A reconciliation of the results from these two alternative approaches is achieved by utilizing empirical relationships obtained between the field scale soil hydraulic properties and climate (i.e., aridity index) that presumably arise from the co-evolution of climate, soil, vegetation and topography in these catch-ments. The synthesis of the results from both of these approaches is used to develop simple prediction equations for storage-discharge relationships using measurable landscape characteristics that could be applied to ungauged basins. At a fundamental level these results also point to the need for more detailed exploration of the co-evolution of climate, soil, vegetation and topography.
Speaker's website: http://cee.illinois.edu/faculty/murugesusivapalan
Dr. Sivapalan is hosted by Dr. Anthony Yannarell. If you wish to meet with the speaker, please contact Tony at email@example.com.