Climate, landscape and vegetation controls of behavioral catchments on
dominant runoff response and catchment travel time distribution
Abstract
The three dominant processes contributing to runoff as proposed by the
Dunne diagram are Hortonian overland flow (HOF), Dunne overland flow
(DOF) and subsurface storm flow (SSF). Using a theoretical perspective,
we investigate the impact of climate, soil, topography and vegetation on
catchment water balance and the probability distribution of the travel
times of each runoff generation component in respect of the connected
instantaneous response function (CIRF) including the interaction of a
partial contributing area connecting to the outlet. A simple distributed
hydrologic model is used to capture the effect of the catchment response
and to estimate the CIRFs under different possible integration of
combined effect of climate, soil, topography and vegetation. A set of
dimensionless similarity parameters represent catchment functions and
provide a quantitative explanation of the conceptual Dunne diagram.
Behavioral catchments are defined from the empirical range of the Budyko
curve and mainly compatible to the physical relationship as illustrated
in the Dunne diagram. The results consistent with the Dunne diagram are:
(1) DOF and SSF dominates in humid for behavioral sand and silt
catchments, (2) HOF dominates in arid for behavioral silt and clay
catchments. Inconsistent results are: (1) SSF dominates in arid for
behavioral sand, silt and clay catchments, (2) HOF dominates in humid
for behavioral clay catchment and (3) no dominant HOF for behavioral
sand catchment. For HOF and DOF dominates, the distribution of CIRFs can
be grouped into similar shapes, which depend on the relative
contribution of hillslope scale and catchment scale. For SSF behavioral
catchments, the shape of the CIRFs depends on the dryness index. The
combined catchment CIRFs of mean travel time for runoff responses
consists with the higher first peak from the HOF and/or DOF and the
second peak from the SSF.