FINIFLUX 2.0

A quantitative understanding of groundwater-surface water interactions is vital for sustainable management of water quantity and quality. The Noble gas Radon-222 (Rn) is becoming increasingly used as a sensitive tracer to quantify groundwater discharge to wetlands, lakes and rivers; a development driven by technical and methodological advances in Rn measurement equipment. However, quantitative interpretation of this data is not trivial, and the methods used to date are usually based on the simplest solutions to the mass-balance equation (e.g. first order finite difference, inversion, trial and error).

FINIFLUX is an implicit Finite Element model that numerically solves the steady state mass balance equation for Rn in lotic (rivers, streams) systems. Degassing is represented using two very popular models which originally are from O'Connor and Dobbins (1958) and Negulescu and Rojanski (1969) with modifications (mostly unit conversions from feet to meter) from Cartwright et al. (2011). Alternatively, FINIFLUX also can work with degassing fluxes specified by the user, which can either be measured directly (e.g. using gas tracer experiments) or some other empirical equation (recommended for head water streams). FINIFLUX is intended to estimate groundwater fluxes into river systems as well as hyporheic exchange characteristics based on measured Rn concentrations and discharge data. The model is coupled to the optimisation software package BEOPEST (Doherty 2010, Principia Mathematica, Inc.) for inverse parameter estimation. FINIFLUX is intended to help scientists and authorities that use the Rn technique to estimate groundwater - surface water exchange for river systems at the reach scale.

UPDATE 1: We have had some particularly difficult datasets where PEST fails to find a good fit to the data. In particular modelled Rn activities are too high. We have found that a regularisation program available on the PEST site can solve this problem and again produce very good fits. See http://www.pesthomepage.org/PEST_FAQ.php. If you have this problem, it is probably best to contact us in how to do the regularisation process.

Update 2: the plotting program plot_output.exe has been disabled. Use pest_tracker.exe instead.

Note: recently, a few people have had problems with the pre_pest routine. The pre_pest does not copy any files into the slaves because msvcp110.dll is missing. This has been hard for us to solve as we could not reproduce this problem on our computers. A colleague in Portugal, Gustavo Santiago Luis, has found a solution. He installed both the x64 and x86 versions of Visual Studio 2012, which can be found here: https://www.microsoft.com/en-us/download/details.aspx?id=30679

If using FINIFLUX please cite the papers:
Frei, S., and B. S. Gilfedder (2015), FINIFLUX: An implicit finite element model for quantification of groundwater fluxes and hyporheic exchange in streams and rivers using radon, Water Resour. Res., 51, 6776-6786, doi:10.1002/2015WR017212.

Adyasari, D., Dimova, N. T., Dulai, H., Gilfedder, B. S., Cartwright, I., McKenzie, T., and Fuleky, P.: (2023): Radon-222 as a groundwater discharge tracer to surface waters, Earth-Science Reviews, 104321, https://doi.org/10.1016/j.earscirev.2023.104321.