Title: Modelling scale-dependent runoff generation in a small semi-arid watershed accounting for rainfall intensity and water depth
Authors: Langhans, Christoph ×
Govers, Gerard
Diels, Jan
Stone, Jeffry J.
Nearing, Mark A. #
Issue Date: 2014
Publisher: C.M.L. Publications
Series Title: Advances in Water Resources vol:69 pages:65-78
Abstract: Observed scale effects of runoff on hillslopes and small watersheds derive from complex interactions of
time-varying rainfall rates with runoff, infiltration and macro- and microtopographic structures. A little
studied aspect of scale effects is the concept of water depth-dependent infiltration. For semi-arid rangeland
it has been demonstrated that mounds underneath shrubs have a high infiltrability and lower lying
compacted or stony inter-shrub areas have a lower infiltrability. It is hypothesized that runoff accumulation
further downslope leads to increased water depth, inundating high infiltrability areas, which
increases the area-averaged infiltration rate. A model was developed that combines the concepts of water
depth-dependent infiltration, partial contributing area under variable rainfall intensity, and the Green–
Ampt theory for point-scale infiltration. The model was applied to rainfall simulation data and natural
rainfall–runoff data from a small sub-watershed (0.4 ha) of the Walnut Gulch Experimental Watershed
in the semi-arid US Southwest. Its performance to reproduce observed hydrographs was compared to
that of a conventional Green–Ampt model assuming complete inundation sheet flow, with runon infiltration,
which is infiltration of runoff onto pervious downstream areas. Parameters were derived from rainfall
simulations and from watershed-scale calibration directly from the rainfall–runoff events. The
performance of the water depth-dependent model was better than that of the conventional model on
the scale of a rainfall simulator plot, but on the scale of a small watershed the performance of both model
types was similar. We believe that the proposed model contributes to a less scale-dependent way of modeling
runoff and erosion on the hillslope-scale.
ISSN: 0309-1708
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division Soil and Water Management
Division of Geography & Tourism
× corresponding author
# (joint) last author

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