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Analysis of Solute Transport in Flow Fields Influenced by Preferential Flowpaths at the Decimeter Scale
Author(s) -
Zheng Chunmiao,
Gorelick Steven M.
Publication year - 2003
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2003.tb02578.x
Subject(s) - plume , hydraulic conductivity , aquifer , scale (ratio) , groundwater , flow (mathematics) , gaussian , diffusion , geology , groundwater flow , hydrology (agriculture) , soil science , mechanics , geotechnical engineering , chemistry , physics , meteorology , thermodynamics , computational chemistry , quantum mechanics , soil water
Several recent studies at the Macrodispersion Experiment (MADE) site in Columbus, Mississippi, have indicated that the relative preferential flowpaths and flow barriers resulting from decimeter‐scale aquifer heterogeneities appear to have a dominant effect on plume‐scale solute transport. Numerical experiments are thus conducted in this study to explore the key characteristics of solute transport in two‐dimensional flow fields influenced by decimeter‐scale preferential flowpaths. A hypothetical but geologically plausible network of 10 cm wide channels of high hydraulic conductivity is used to represent the relative preferential flowpaths embedded in an otherwise homogeneous aquifer. When the hydraulic conductivity in the channels is 100 times greater than that in the remaining portion of the aquifer, the calculated concentration distributions under three source configurations all exhibit highly asymmetrical, non‐Gaussian patterns. These patterns, with peak concentrations close to the source and extensive spreading downgradi‐ent, resemble that observed at the MADE site tracer tests. When the contrast between the channel and nonchannel hydraulic conductivities is reduced to 30:1 from 100:1, the calculated mass distribution curve starts to approach a Gaussian one with the peak concentration near the central portion of the plume. Additional analysis based on a fieldscale model demonstrates that the existence of decimeter‐scale preferential flowpaths can have potentially far‐reaching implications for ground water remediation. Failure to account for them in numerical simulation could lead to over‐estimation of the effectiveness of the remedial measure under consideration.