HR: 1340h
AN: H33B-0459    [Abstracts]
TI: A preferential flow model based on flow variability in macropores
AU: * Weiler, M
EM: markus.weiler@ubc.ca
AF: University of British Columbia, Department of Forest Resources Management and Geography 2424 Main Mall, Vancouver, BC V6T1Z4 Canada
AB: Simulating infiltration in soils containing macropores still provides unsatisfactory results, as existing models seem not to capture all relevant processes. Recent studies of macropore flow initiation in natural soils containing earthworm channels revealed a distinct flow rate variability in the macropores depending on the initiation process (Weiler & Naef, 2003, J of Hydrology, 273: 139-154). When macropore flow was initiated at the soil surface, most of the macropores received very little water while a few macropores received a large proportion of the total inflow. In contrast, when macropore flow was initiated from a saturated or nearly saturated soil layer, macropore flow rate variation was much lower. The objective of this study was to develop and test a model, which combines the macropore flow variability with several established approaches to model dual permeability soils. We then evaluate the INfiltration-INitiation-INteraction Model (IN$^{3}$M) as a tool to explore the influence of macropore flow variability on infiltration behavior by performing a sensitivity analysis and applying IN$^{3}$M to sprinkling and dye tracer experiments at various field sites with different macropore and soil matrix properties. The sensitivity analysis showed that the flow variability in macropores reduces interaction between the macropores and the surrounding soil matrix and thus increases bypass flow, especially for surface initiation of macropore flow and at higher rainfall intensities. The model application shows reasonable agreement between IN$^{3}$M simulations and field data in terms of water balance, water content change, and dye patterns. The influence of macropore flow variability on the hydrological response of the soil was considerable and especially pronounced for soils where initiation occurs at the soil surface.
UR: http://faculty.forestry.ubc.ca/weiler/research.html
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting