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Using dual‐domain advective‐transport simulation to reconcile multiple‐tracer ages and estimate dual‐porosity transport parameters
Author(s) -
Sanford Ward E.,
Niel Plummer L.,
Casile Gerolamo,
Busenberg Ed,
Nelms David L.,
Schlosser Peter
Publication year - 2017
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2016wr019469
Subject(s) - tracer , advection , porosity , soil science , groundwater , flow (mathematics) , piston (optics) , environmental science , geology , mechanics , hydrology (agriculture) , geotechnical engineering , physics , thermodynamics , wavefront , nuclear physics , optics
Dual‐domain transport is an alternative conceptual and mathematical paradigm to advection‐dispersion for describing the movement of dissolved constituents in groundwater. Here we test the use of a dual‐domain algorithm combined with advective pathline tracking to help reconcile environmental tracer concentrations measured in springs within the Shenandoah Valley, USA. The approach also allows for the estimation of the three dual‐domain parameters: mobile porosity, immobile porosity, and a domain exchange rate constant. Concentrations of CFC‐113, SF 6 , 3 H, and 3 He were measured at 28 springs emanating from carbonate rocks. The different tracers give three different mean composite piston‐flow ages for all the springs that vary from 5 to 18 years. Here we compare four algorithms that interpret the tracer concentrations in terms of groundwater age: piston flow, old‐fraction mixing, advective‐flow path modeling, and dual‐domain modeling. Whereas the second two algorithms made slight improvements over piston flow at reconciling the disparate piston‐flow age estimates, the dual‐domain algorithm gave a very marked improvement. Optimal values for the three transport parameters were also obtained, although the immobile porosity value was not well constrained. Parameter correlation and sensitivities were calculated to help quantify the uncertainty. Although some correlation exists between the three parameters being estimated, a watershed simulation of a pollutant breakthrough to a local stream illustrates that the estimated transport parameters can still substantially help to constrain and predict the nature and timing of solute transport. The combined use of multiple environmental tracers with this dual‐domain approach could be applicable in a wide variety of fractured‐rock settings.