## Dual Permeability + MIM

A discussion forum for users of the new HYDRUS 2D/3D. HYDRUS is a software package for simulating water, heat and solute movement in two- and three-dimensional variably saturated media. Happy Posting!
Kathrine
Posts: 5
Joined: Mon Nov 12, 2018 6:42 pm
Location: Spain

### Dual Permeability + MIM

Hallo,

Two questions please if someone can help.

1) In dual-permeability + MIM model, the ThImob.M. refers to local water content of matrix region right?

2) The mass transfer coefficient between mobile matrix and immobile, it is the AlphaM in Reaction Parameters for Solute? Because in the description it is referred as First-order rate coefficient for nonequilibrium adsorption in the matrix. I found some examples of dual-permeability+MIM model for Hydrus1D from

Šimůnek J., van Genuchten M.T. (2008) Modeling nonequilibrium flow and transport processes using HYDRUS. Vadose Zone Journal 7:782-797. DOI: 10.2136/vzj2007.0074

, in which the mass transfer coefficient for mobile-immobile matrix is equal 0.1 d-1 in AlphaM. Also, is that a realistic value?

Jirka
Posts: 4759
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Dual Permeability + MIM

1. Yes
2. Yes. AlphaM is interpreted as the "First-order rate coefficient for nonequilibrium adsorption in the matrix" when one uses the Two-Site Sorption model and as "First-order mass transfer coefficient between mobile and immobile water contents of the Matrix Domain" when the MIM model for the Matrix domain is used.

Note that I posted some examples for DualPerm on the HYDRUS website:
https://www.pc-progress.com/en/Default. ... 2-DualPerm

Below, I add two examples for the DPM-MIM and DPM-TS models.

What the value of AlphaM should be? I have no idea. It is usually a fitting coefficient. You can check there two review papers if you find some info:

Köhne, J. M., S. Köhne, and J. Šimůnek, A review of model applications for structured soils: a) Water flow and tracer transport, Journal of Contaminant Hydrology, Special Issue “Flow Domains”, 104(1-4), 4-35, doi: 10.1016/j.jconhyd.2008.10.002, 2009.

Köhne, J. M., S. Köhne, and J. Šimůnek, A review of model applications for structured soils: b) Pesticide transport, Journal of Contaminant Hydrology, Special Issue “Flow Domains”, 104(1-4), 36-60, doi: 10.1016/j.jconhyd.2008.10.003, 2009.

Jirka
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