AMCS Seminar

Speaker: 
Ricardo Mantilla Gutierrez, Asst. Professor, IIHR—Hydroscience & Engineering
Topic: 
"Propagation of nonlinearities, oscillation and thresholds at the hillslope scale (0.1 km$^2$) to the river basin scale (10000 km$^2$)"

Abstract:
I will show how nonlinearities in rainfall-runoff transformation that occur at the hillslope scale propagate through the river network to a watershed outlet using a theoretical model of runoff generation and runoff transport. I will use a system of ordinary differential equations (ODEs) to represent simultaneously the aggregated behavior of changes in water storage in the surface, the unsaturated and the saturated soil layers of a hillslope element. The ODE system is solved for the river network of the Cedar River basin in Iowa, a 17,000 km$^2$ basin. The ODE system can be modified to exhibit nonlinearities observed in data but can also be reduced to a simpler linear system that only captures partially the hillslope dynamics.  The ODE system is coupled to a runoff routing scheme to propagate runoff generated at the hillslope scale through the river network to the watershed outlet.  The results results reveal the role of the self-similar river network in smoothing out multiple aspects of the hillslope-scale complex dynamics.  More specifically we show that the second moment of the distribution of travel times at the hillslope scale (i.e. runoff hydrograph) determines almost entirely the dynamics that are observed at the scale of the river network outlet.  We demonstrate this by fitting lognormal distributions to the runoff hydrographs and comparing the output of routing it as input runoff.  Our work also helps explain how the performance of overly simplified watershed models can be comparable to more sophisticated, realistic and physically based ones.

Event Date: 
April 13, 2018 - 3:30pm to 4:30pm
Location: 
218 MLH
Calendar Category: 
Seminar