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Research article2005Peer reviewed

Simulating solute transport in a structured field soil: Uncertainty in parameter identification and predictions

Larsbo M, Jarvis N

Abstract

Dual-permeability models have been developed to account for the significant effects of macropore flow on contaminant transport, but their use is hampered by difficulties in estimating the additional parameters required. Therefore, our objective was to evaluate data requirements for parameter identification for predictive modeling with the dual-permeability model MACRO. Two different approaches were compared: sequential uncertainty fitting (SUFI) and generalized likelihood uncertainty estimation (GLUE). We investigated six parameters controlling macropore flow and pesticide sorption and degradation, applying MACRO to a comprehensive field data set of bromide and bemazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide] transport in a structured soil. The GLUE analyses of parameter conditioning for different combinations of observations showed that both resident and flux concentrations were needed to obtain highly conditioned and unbiased parameters and that observations of tracer transport generally improved the conditioning of macropore flow parameters. The GLUE "behavioral" parameter sets covered wider parameter ranges than the SUFI posterior uncertainty domains. Nevertheless, estimation uncertainty ranges defined by the 5th and 95th percentiles were similar and many simulations randomly sampled from the SUFI posterior uncertainty domains had negative model efficiencies (minimum of -3.2). This is because parameter correlations are neglected in SUM and the posterior uncertainty domains were not always determined correctly. For the same reasons, uncertainty ranges for predictions of bentazone losses through drainflow for good agricultural practice in southern Sweden were 27% larger for SUM compared with GLUE. Although SUM proved to be an efficient parameter estimation tool, GLUE seems better suited as a method of uncertainty estimation for predictions

Published in

Journal of Environmental Quality
2005, Volume: 34, number: 2, pages: 621-634
Publisher: AMER SOC AGRONOMY

      SLU Authors

    • Larsbo, Mats

      • Department of Soil Sciences, Swedish University of Agricultural Sciences

      • Jarvis, Nicholas

        • Department of Soil Sciences, Swedish University of Agricultural Sciences

      UKÄ Subject classification

      Agricultural Science

      Publication identifier

      DOI: https://doi.org/10.2134/jeq2005.0621

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/6565