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| Titel |
Evaluation of rainfall infiltration characteristics in a volcanic ash soil by time domain reflectometry method |
| VerfasserIn |
S. Hasegawa |
| 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 ; 1, no. 2 ; Nr. 1, no. 2, S.303-312 |
| Datensatznummer |
250000149
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| Publikation (Nr.) |
 copernicus.org/hess-1-303-1997.pdf |
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| Zusammenfassung |
| Time domain reflectometry (TDR) was used to monitor
soil water conditions and to evaluate infiltration characteristics associated with
rainfall into a volcanic-ash soil (Hydric Hapludand) with a low bulk density. Four 1 m
TDR probes were installed vertically along a 6 m line in a bare field. Three 30 cm and
one 60 cm probes were installed between the 1 m probes. Soil water content was measured
every half or every hour throughout the year. TDR enabled prediction of the soil water
content precisely even though the empirical equation developed by Topp et al. (1980)
underestimated the water content. Field capacity, defined as the amount of water stored
to a depth of 1 m on the day following heavy rainfall, was 640 mm. There was approximately
100 mm difference in the amount of water stored between field capacity and the driest
period. Infiltration characteristics of rainfall were investigated for 36 rainfall events
exceeding 10 mm with a total amount of rain of 969 mm out of an annual rainfall of 1192 mm.
In the case of 25 low intensity rainfall events with less than 10 mm h-1 on to
dry soils, the increase in the amount of water stored to a depth of 1 m was equal to the
cumulative rainfall. For rain intensity in excess of 10 mm h-1, non-uniform
infiltration occurred. The increase in the amount of water stored at lower elevation
locations was 1.4 to 1.6 times larger than at higher elevation locations even though the
difference in ground height among the 1 m probes was 6 cm. In the two instances when
rainfall exceeded 100 mm, including the amount of rain in a previous rainfall event, the
increase in the amount of water stored to a depth of 1 m was 65 mm lower than the total
quantity of rain on the two occasions (220 mm); this indicated that 65 mm of water or
5.5% of the annual rainfall had flowed away either by surface runoff or bypass flow.
Hence, approximately 95% of the annual rainfall was absorbed by the soil matrix but it
is not possible to simulate soil water movement by Darcy's law over a long period at farm
level due to the local differences in rainfall intensity. |
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