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Title: UNCERTAINTY IN SOIL WATER FLOW SIMULATIONS WITH VARIOUS PARAMETER SOURCES

Author
item GUBER, ANDREY - ARS/BA VISITING SCIENTIST
item JACQUES, D. - SCK-CEN, BELGIUM
item SIMUNEK, J. - U. OF CA., RIVERSIDE,CA
item Pachepsky, Yakov
item Van Genuchten, Martinus
item CADY, R. - US NRC, WASHINGTON DC
item NICHOLSON, T. - US NRC, WASHINGTON DC

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2004
Publication Date: 10/31/2004
Citation: Guber, A.K., Jacques, D., Simunek, J., Pachepsky, Y.A., Van Genuchten, M.T., Cady, R.E., Nicholson, T.J. 2004. Uncertainty in soil water flow simulations with various parameter sources. [Abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. CD-ROM.

Interpretive Summary:

Technical Abstract: The extent of the uncertainty in soil water flow simulation results depends on the uncertainties in soil hydraulic properties (SHP). Objectives of this work were to assess uncertainty in accuracy of water flow simulations with laboratory-measured and pedotransfer-estimated SHP. Simulated soil water contents and fluxes were compared with water contents measured in loamy soil with TDR at five depths for 384 days and water fluxes measured with passive capillary samplers at 15 and 55 cm depths. Laboratory SHP variation was simulated via random sampling from the probability distribution of van Genuchten parameters for measured water retention curves. Variation in estimated SHP was simulated by random sampling from a set of 22 pedotransfer functions (PTF). Mechanistic, Richards equation-based model coded in HYDRUS1D and a water budget model were applied. For both models, laboratory SHP did not provide better accuracy compared with PTF in the uncertainty context. With both parameter sources, the water budget model predicted water contents more accurately as compared with the mechanistic one. With both models, accuracy in flux prediction increased with time scale, i. e. with the length of the time interval over which the fluxes were averaged. At time scales less than four days, the mechanistic model predicted water fluxes more accurately compared with the water budget model.