## Calculating Alpha and N parameters from field data

A discussion forum for RETC users. RETC is a program which can be used to analyze the soil water retention and hydraulic conductivity functions of unsaturated soils.
Borntoeger
Posts: 1
Joined: Tue May 28, 2024 11:06 am
Location: Germany

### Calculating Alpha and N parameters from field data

Hello there,

is it possible to calculate/estimate the Alpha and N parameters from Mualem van Genuchten with measured field data from a Mini disc Infiltrometer?
I'm trying to compare the already measured Alpha and N Parameters from Mualem van Genuchten to the field data measured by me but I need to calculate my field data parameters first..

Website to Minidisc manual and excel data sheet which I used:

https://metergroup.com/products/mini-di ... r-support/
Attachments
20421_Mini_Disk_Manual_Web.pdf
Manual from Mini Disc
New-Minidisk-Infiltrometer-Macro.xlsx
Excel sheet for calculating

Jirka
Posts: 6075
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Calculating Alpha and N parameters from field data

RETC can use only the retention data (i.e., head-water content) or hydraulic conductivity data (head/water content -conductivity). It cannot use flow data (such as cumulative infiltration. For that, you need to use a flow model, such as HYDRUS. You can see a couple of examples in the literature, in which the disk data were used for this purpose. Below is some of my ancient work on this topic:

Šimůnek, J., and M. Th. van Genuchten, Estimating unsaturated soil hydraulic properties from tension disc infiltrometer data by numerical inversion, Water Resources Research, 32(9), 2683-2696, 1996.

Šimůnek, J., and M. Th. van Genuchten, Estimating unsaturated soil hydraulic properties from multiple tension disc infiltrometer data, Soil Science, 162(6), 383-398, 1997.

Šimůnek, J., R. Angulo-Jaramillo, M. G. Schaap, J.-P. Vandervaere, and M. Th. van Genuchten, Using an inverse method to estimate the hydraulic properties of crusted soils from tension-disc infiltrometer data, Geoderma, 86(1-2), 61-81, 1998.

Šimůnek, J., D. Wang, P. J. Shouse, and M. Th. van Genuchten, Analysis of field tension disc infiltrometer data by parameter estimation, International Agrophysics, 12, 167-180, 1998.

Šimůnek, J., O. Wendroth, and M. Th. van Genuchten, Estimating unsaturated soil hydraulic properties from laboratory tension disc infiltrometer experiments, Water Resources Research, 35(10), 2965-2979, 1999.

J.