Water flow processes in weathered granitic bedrock and their effects on runoff generation in a small headwater catchment

Recent studies have suggested that bedrock groundwater can exert considerable influence on runoff generation, water chemistry, and the occurrence of landslides in headwater catchments. To clarify water infiltration and redistribution processes between soil and shallow bedrock and their effect on sto...

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Bibliographic Details
Published in:Water resources research 2006-02, Vol.42 (2), p.W02414-n/a
Main Authors: Kosugi, K, Katsura, S.Y, Katsuyama, M, Mizuyama, T
Format: Article
Language:English
Subjects:
base flow
bedrock
buffering capacity
granite
Groundwater/surface water interaction
hydraulic gradient
hydrochemistry
Hydrology
Infiltration
infiltration (hydrology)
landslides
measuring devices
physical properties
pore water pressure
Rocks
runoff
saturated conditions
saturated flow
soil water
Soils
spatial data
stormwater
unsaturated conditions
unsaturated flow
Vadose zone
water balance
water flow
watersheds
weathering
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Summary:Recent studies have suggested that bedrock groundwater can exert considerable influence on runoff generation, water chemistry, and the occurrence of landslides in headwater catchments. To clarify water infiltration and redistribution processes between soil and shallow bedrock and their effect on storm and base flow discharge processes in a small headwater catchment underlain by weathered granite, we conducted hydrometric observations using soil and bedrock tensiometers combined with hydrochemical measurements and water budget analyses at three different spatial scales. Results showed that in an unchanneled 0.024-ha headwater catchment, saturated and unsaturated infiltration from soil to bedrock is a dominant hydrological process at the soil-bedrock interface. Annual bedrock infiltration ranged from 35 to 55% of annual precipitation and increased as precipitation increased, suggesting a high level of potential bedrock infiltration, partly explained by the high buffering capacity of the soil layer overlying the bedrock. This physical property of the soil layer was an important factor in controlling the generation of bedrock infiltration and saturated lateral flow over the bedrock. In a 0.086-ha watershed including the unchanneled headwater catchment, exfiltration from the bedrock toward the soil layer composed more than half the annual discharge.
ISSN:0043-1397
1944-7973
DOI:10.1029/2005WR004275