HR: 0800h
AN: H31D-0413    [Abstracts]
TI: A new laboratory instrument for defining near-saturation wetting-drying and capillary conductivity
AU: * Vache, K
EM: kellie.vache@oregonstate.edu
AF: Dept. of Forest Engineering, Oregon State University, Corvallis, OR 97331 United States
AU: McDonnell, J J
EM: jeff mcdonnell@orst.edu
AF: Dept. of Forest Engineering, Oregon State University, Corvallis, OR 97331 United States
AU: Ekanayake, J
EM: ekanayakej@landcareresearch.co.nz
AF: Landcare Research, 1 Landcare Way, Lincoln, 1 New Zealand
AU: Graham, C
EM: chris.graham@oregonstate.edu
AF: Dept. of Forest Engineering, Oregon State University, Corvallis, OR 97331 United States
AB: The moisture release curve is a fundamental descriptor of soil water movement. While tension table apparatus for defining drainage curves in the near-saturated region (0 to -100 cm H2O) have been available for many decades, there has been little advance in automating the process, particularly when measurements of wetting, drying and capillary conductivity are combined. We describe a new instrument, the Automated Moisture Release Apparatus (AMRA), that uses a precision water flow measurement coupled with an accurately controlled variable hydraulic head to exactly define the relationship between matric potential and volumetric water content? from 0 to -100 cm H2O. The new instrument automates the process without any disturbance to the soil core and and has fully programmable suction steps and equilibration times. We compare AMRA moisture release curve results with published Accusand tests for four different grain size mixtures and under different sample height and volume combinations. Our results are consistent with published results and our tests provide guidance on appropriate core lengths for media characterization. AMRA results from field samples from well-characterized soils at the HJ Andrews Experimental Forest in Oregon are also described. These experiments show both consistent drying behavior and drainable porosity decline with depth in the vadose zone. Overall, the instrument's precision, programmable platform, and combined conductivity and moisture content measurement features, make it a useful tool for estimating soil water storage properties/parameters for use in vadose zone hydrology.
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting