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Title: ANALYSIS OF TEMPERATURE EFFECTS ON TENSION INFILTROMETRY

Author
item CASTIGLIONE, PAOLO - MONTANA ST U, BOZEMAN
item SHOUSE, PETER
item MOHANTY, BINAYAK - TEXAS A&M, COLLEGE STN
item VAN GENUCHTEN, MARTINUS

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2004
Publication Date: 6/13/2005
Citation: Castiglione, P., Shouse, P.J., Mohanty, B., Van Genuchten, M.T. 2005. Analysis of temperature effects on tension infiltrometry. Vadose Zone Journal.4(3):481-487.

Interpretive Summary: Tension infiltrometers are used for measuring saturated infiltration rates in soils and fractured rock. Fluctuating ambient temperatures cause dramatic pressure variations due to the presence of confined air inside the infiltrometer, thus affecting the measured flux rate. This is especially true for low infiltration rates and long equilibration times. We developed a model to analyze the effects of temperature changes on the on infiltrometer accuracy. Experimental results confirmed our model simulations. Using our model we were able to optimize tension infiltrometer design criteria so that significant more accurate infiltrometer measurements are now possible under fluctuating temperature conditions.

Technical Abstract: Tension infiltrometers are useful for measuring in-situ near-saturated infiltration rates in soils and fractured rock. Fluctuating ambient temperatures can cause dramatic pressure variations due to the presence of confined air inside the infiltrometer, thus affecting the intended pressure head to be applied to the soil or rock surface, and hence also the measured flux rate. This is especially true for low infiltration rates and long equilibration times. We developed a model to analyze the effects of temperature changes on the static pressure of the confined air volume within tension infiltrometers. The model was tested using several prototype infiltrometer designs in a computer-controlled variable temperature room. Experimental results confirmed the model simulations. For example, predicted and measured changes in the pressure head were 11.2 and 12.5 cm following a change of 18.5 C in the temperature. Using the model we were able to optimize several infiltrometer designs that significant reduced the undesired effects of temperature on tension infiltrometers results.