HR: 1330h
AN: H12A-0957    [PDF]
TI: Inverse Calibration of the Dual-Permeability Model MACRO: Theoretical Analysis and Application to Microlysimeter Experiments.
AU: * Roulier, S
EM: Stephanie.Roulier@mv.slu.se
AF: Dept. of Soil Sciences, Swedish University of Agricultural Sciences, Box 7014, Uppsala, 75007 Sweden
AU: Jarvis, N
EM: Nicholas.Jarvis@mv.slu.se
AF: Dept. of Soil Sciences, Swedish University of Agricultural Sciences, Box 7014, Uppsala, 75007 Sweden
AB: Macropore flow is a key factor for determining chemical transport in unsaturated soils, but the description of the complex processes involved in macropore flow requires several parameters that cannot be easily measured. Inverse modeling procedures are increasingly used for model calibration, because they are objective and reproducible. But this is only true when the problem is well-posed: an ill-posed problem leads to parameter nonuniqueness, and thus contributes to poor model performance, like error and/or uncertainty in model predictions. Factors linked to nonuniqueness are most often related to sensitivity issues and/or correlation among two or several parameters. This study focused on the use of inverse techniques to estimate parameters controlling macropore flow, transport, and transformation processes in the dual porosity/dual-permeability model of water flow and solute transport MACRO. MACRO was used together with the inverse modeling package SUFI. The Bayesian (global) approach followed by SUFI is stable, converging, and robust. Moreover, the procedure also predicts a posterior uncertainty domain for the estimated parameters. A theoretical study was carried out to test the inverse modeling tool SUFI/MACRO. Generated "dummy" data set were used for this purpose, representing transient leaching experiment for tracers and reactive solutes in small soil columns (20 cm height). General issues related to inverse modeling such as internal correlation and sensitivity were investigated, with the help of response surface analysis, as well as the influence of the choice of the goal function used in the inverse procedure. Attention was also focused on the most appropriate experimental design necessary for a reliable parameter estimation. The procedure was then applied to real data, obtained from tracer leaching experiments carried out on microlysimeters. Based on calculated model efficiencies, MACRO/SUFI gave good predictions of water movement and tracer transport. This is an encouraging first step prior to application against real data on reactive transport.
DE: 1875 Unsaturated zone
DE: 3210 Modeling
DE: 3260 Inverse theory
DE: 5139 Transport properties
SC: Hydrology [H]
MN: 2003 Fall Meeting