Defining the bounds of using radioactive isotope tracers to sense past groundwater recharge under transient state conditions

Full description

This is the code accompanying the paper by Chmielarski et al. (2022) of the same name. The following code allows for the analysis of how radioactive isotope signatures in groundwater react to changes in various system paramaters (the half-life of the radioactive isotope, the Peclet number, the exchange between the mobile and immobile zones, and the ratio of water saturation in the immobile to mobile portions of the system). This exercise aims at assessing how these system parameters affect the efficacy of radioactive tracers to be used for sensing changes in groundwater recharge over time, which is here simulated by a step-change in groundwater velocity. Note, that this code can includes the 'DeHoog' script, which was developed by McCallum et al. (2020) using the de Hoog method (De Hoog et al., 1982) for inversing the Laplace transform, which applies a quotient-difference algorith. For full clarification, the analytical solution which is presented in this code can best be understood by following the supplementary documentation to the Chmielarski et al. (2022) paper, which presents a step-by-step solution. Relevant References: Chmielarski, M., Dogramaci, S., Cook, P.G., & McCallum, J.L. (2022). Defining the bounds of using radioactive isotope tracers to sense past groundwater recharge under transient state conditions. Geophysical Research Letters XXX de Hoog, F.R., Knight, J.H., & Stokes, A.N. (1982). An improved method for numerical inversion of Laplace transforms. Society for Industrial and Applied Mathematics Journal of Science and Statistical Computing 3(3): 357-366. McCallum, J.L., Höhne, A., Shaper, J.L., Shanafield, M., Banks, E.W., Posselt, M., Batelaan, O., & Lewandowski, J. (2020). A numerical stream transport modelling approach including multiple conceptualizations of hyporheic exchange and spatial variability to assess contaminant removal. Water Resources Research 56, e2019WR024987. https://doi.org/10.1029/2019WR024987.

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External Organisations
School of Earth Sciences and National Centre for Groundwater Research and Training, The University of Western Australia, Crawley, WA, Australia; National Centre for Groundwater Research and Training, College of Science and Engineering, Flinders University, Bedford Park, SA, Australia

Associated Persons
J.L. McCallum (Contributor)