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| Titel |
Sensitivity of point scale surface runoff predictions to rainfall resolution |
| VerfasserIn |
A. J. Hearman, C. Hinz |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 11, no. 2 ; Nr. 11, no. 2 (2007-03-05), S.965-982 |
| Datensatznummer |
250009227
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| Publikation (Nr.) |
 copernicus.org/hess-11-965-2007.pdf |
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| Zusammenfassung |
| This paper investigates the effects of using non-linear, high resolution
rainfall, compared to time averaged rainfall on the triggering of hydrologic
thresholds and therefore model predictions of infiltration excess and
saturation excess runoff at the point scale. The bounded random cascade
model, parameterized to three locations in Western Australia, was used to
scale rainfall intensities at various time resolutions ranging from 1.875
min to 2 h. A one dimensional, conceptual rainfall partitioning model was
used that instantaneously partitioned water into infiltration excess,
infiltration, storage, deep drainage, saturation excess and surface runoff,
where the fluxes into and out of the soil store were controlled by
thresholds. The results of the numerical modelling were scaled by relating
soil infiltration properties to soil draining properties, and in turn,
relating these to average storm intensities. For all soil types, we related
maximum infiltration capacities to average storm intensities (k*)
and were able to show where model predictions of infiltration excess were
most sensitive to rainfall resolution (ln k*=0.4) and where using
time averaged rainfall data can lead to an under prediction of infiltration
excess and an over prediction of the amount of water entering the soil (ln k*>2) for all three rainfall locations tested. For soils
susceptible to both infiltration excess and saturation excess, total runoff
sensitivity was scaled by relating drainage coefficients to average storm
intensities (g*) and parameter ranges where predicted runoff was
dominated by infiltration excess or saturation excess depending on the
resolution of rainfall data were determined (ln g*<2).
Infiltration excess predicted from high resolution rainfall was short and
intense, whereas saturation excess produced from low resolution rainfall was
more constant and less intense. This has important implications for the
accuracy of current hydrological models that use time averaged rainfall
under these soil and rainfall conditions and predictions of larger scale
phenomena such as hillslope runoff and runon. It offers insight into how
rainfall resolution can affect predicted amounts of water entering the soil
and thus soil water storage and drainage, possibly changing our
understanding of the ecological functioning of the system or predictions of
agri-chemical leaching. The application of this sensitivity analysis to
different rainfall regions in Western Australia showed that locations in the
tropics with higher intensity rainfalls are more likely to have differences
in infiltration excess predictions with different rainfall resolutions and
that a general understanding of the prevailing rainfall conditions and the
soil's infiltration capacity can help in deciding whether high
rainfall resolutions (below 1 h) are required for accurate surface runoff
predictions. |
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