Field measurement of entrapped pore‐air pressure and the effect of rising groundwater level in the soil layer

Unsaturated soil contains pore air, some of which becomes entrapped in the soil layer during the infiltration process. Such entrapped pore air in the soil layer inhibits infiltration, decreases hydraulic conductivity, and causes erroneous estimates of groundwater response. Experimental studies sugge...

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Bibliographic Details
Published in:Hydrological processes 2024-07, Vol.38 (7), p.n/a
Main Authors: Iwagami, Sho, Noguchi, Shoji, Shimizu, Takanori, Kubota, Tayoko, Iida, Shin'ichi
Format: Article
Language:English
Subjects:
Air
Atmospheric pressure
Catchment area
Catchments
Compressed air
Compression
Entrapment
field measurement
Groundwater
Groundwater effects
groundwater level
Groundwater levels
Headwater catchments
Headwaters
Hurricanes
Hydraulic conductivity
Infiltration
Moisture content
Pore pressure
Pore water pressure
pore‐air entrapment
pore‐air pressure
Precipitation
Pressure effects
Pressurization
Rainfall
Rainfall intensity
Soil
Soil depth
soil layer
Soil layers
Soil moisture
Stream discharge
Typhoons
Unsaturated soils
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Summary:Unsaturated soil contains pore air, some of which becomes entrapped in the soil layer during the infiltration process. Such entrapped pore air in the soil layer inhibits infiltration, decreases hydraulic conductivity, and causes erroneous estimates of groundwater response. Experimental studies suggest an effect of compressed entrapped pore air on stream discharge. However, few studies have investigated the behaviour of pore air in the field, and no method for measurement of pore‐air behaviour has been established. We measured pore‐air pressure (Pair) with a simple handmade probe, combined with atmospheric pressure (Patm) and groundwater level. The entrapment and compression of pore air were detected based on the pressure difference (ΔP = Pair – Patm). Observations were conducted for approximately 1 year in two small headwater catchments (TC and HA, which have differences in soil depth and groundwater level dynamics) in Ibaraki Prefecture, Japan. Positive responses of ΔP during some rainfall events were confirmed at both TC and HA. Pore‐air entrapment occurred even during weak rainfall events with rainfall intensity of
ISSN:0885-6087
1099-1085
DOI:10.1002/hyp.15235