Event Title

Tracer study in a large undisturbed soil core

Description

We present results from tracer experiments in a large (27 cm diameter by 27.3 cm tall) undisturbed soil core from the UBC Malcolm Knapp Research Forest. The salt tracer experiments included both constant tracer applications and a slug tracer test. The conductivity of the soil water was measured at three locations in the core. The conductivity of the outflow water of different segments of the core and total outflow water were also measured. We found large differences in tracer concentrations from different segments of the core. The breakthrough curves were modeled using the advection-dispersion model. Fitted soil water pore velocities were smaller than the constant rainfall rate or the outflow pore water velocity. Both results show the importance of preferential flow in the large soil core. During one experiment, the rainfall intensity was temporarily increased. Our results show that a pressure-wave response occurred and resulted in an immediate increase in the outflow rate. The pressure-wave velocity was 20- 50 times larger than the average pore water velocity. Decreases in soil moisture in response to the pressure-wave were also observed. The results of this study show the importance of rapid responses due to preferential flow as well as due to pressure-wave responses.

Start Date

8-3-2008 8:00 AM

End Date

8-3-2008 5:00 PM

Subject - LCSH

Groundwater tracers--British Columbia; Drill cores--British Columbia

Geographic Coverage

British Columbia

Genre/Form

Posters

Session

Poster Session

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Digital Format

application/pdf

Language

English

Type

event

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Mar 8th, 8:00 AM Mar 8th, 5:00 PM

Tracer study in a large undisturbed soil core

We present results from tracer experiments in a large (27 cm diameter by 27.3 cm tall) undisturbed soil core from the UBC Malcolm Knapp Research Forest. The salt tracer experiments included both constant tracer applications and a slug tracer test. The conductivity of the soil water was measured at three locations in the core. The conductivity of the outflow water of different segments of the core and total outflow water were also measured. We found large differences in tracer concentrations from different segments of the core. The breakthrough curves were modeled using the advection-dispersion model. Fitted soil water pore velocities were smaller than the constant rainfall rate or the outflow pore water velocity. Both results show the importance of preferential flow in the large soil core. During one experiment, the rainfall intensity was temporarily increased. Our results show that a pressure-wave response occurred and resulted in an immediate increase in the outflow rate. The pressure-wave velocity was 20- 50 times larger than the average pore water velocity. Decreases in soil moisture in response to the pressure-wave were also observed. The results of this study show the importance of rapid responses due to preferential flow as well as due to pressure-wave responses.