Comment on “Advective transport in heterogeneous aquifers: Are proxy models predictive?” by A. Fiori, A. Zarlenga, H. Gotovac, I. Jankovic, E. Volpi, V. Cvetkovic, and G. Dagan
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Neuman, Shlomo P.Affiliation
Univ Arizona, Dept Hydrol & Atmospher SciIssue Date
2016-07
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AMER GEOPHYSICAL UNIONCitation
Comment on “Advective transport in heterogeneous aquifers: Are proxy models predictive?” by A. Fiori, A. Zarlenga, H. Gotovac, I. Jankovic, E. Volpi, V. Cvetkovic, and G. Dagan 2016, 52 (7):5701 Water Resources ResearchJournal
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© 2016. American Geophysical Union. All Rights Reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
Fiori et al. (2015) examine the predictive capabilities of (among others) two "proxy'' non-Fickian transport models, MRMT (Multi-Rate Mass Transfer) and CTRW (Continuous-Time Random Walk). In particular, they compare proxy model predictions of mean breakthrough curves (BTCs) at a sequence of control planes with near-ergodic BTCs generated through two-and three-dimensional simulations of nonreactive, mean-uniform advective transport in single realizations of stationary, randomly heterogeneous porous media. The authors find fitted proxy model parameters to be nonunique and devoid of clear physical meaning. This notwithstanding, they conclude optimistically that "i. Fitting the proxy models to match the BTC at [one control plane] automatically ensures prediction at downstream control planes [and thus] ii .... the measured BTC can be used directly for prediction, with no need to use models underlain by fitting.'' I show that (a) the authors' findings follow directly from (and thus confirm) theoretical considerations discussed earlier by Neuman and Tartakovsky (2009), which (b) additionally demonstrate that proxy models will lack similar predictive capabilities under more realistic, non-Markovian flow and transport conditions that prevail under flow through nonstationary (e.g., multiscale) media in the presence of boundaries and/or nonuniformly distributed sources, and/or when flow/transport are conditioned on measurements.Note
First published: 30 July 2016; 6 month embargo.ISSN
00431397Version
Final published versionAdditional Links
http://doi.wiley.com/10.1002/2016WR019093ae974a485f413a2113503eed53cd6c53
10.1002/2016WR019093