Estimation of Hydraulic conductivity

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.
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Nangamso
Posts: 3
Joined: Mon Mar 06, 2017 1:46 pm
Location: Singapore

Estimation of Hydraulic conductivity

Post by Nangamso » Wed Aug 09, 2017 9:51 pm

Hi

I am running the RETC with retention data only to obtain all the hydraulic soil properties needed by Hydrus.
But when I look in the output file I only get alpha, n, Theta_r and Theta_s I understand that this is because I do not have hydraulic conductivity data but from the output file there is a list of hydraulic conductivity simulated by the model, Now which Hydraulic conductivity value do I choose from that list as a final Ks ?

Thanks in advance
Regards
Nangamso

Jirka
Posts: 4801
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Estimation of Hydraulic conductivity

Post by Jirka » Thu Aug 10, 2017 12:11 am

The program lists all the parameters in both RETC.in and RETC.out files. If you do not have a measured value of Ks, you should use a value of 1 (one) and get the relative conductivity values. Or you can select the Ks value using Rosetta (Neural networks) or Soil Catalog. The value of l (unless you specify is differently) is usually selected to be equal to 0.5. J.

Nangamso
Posts: 3
Joined: Mon Mar 06, 2017 1:46 pm
Location: Singapore

Re: Estimation of Hydraulic conductivity

Post by Nangamso » Sun Aug 13, 2017 8:42 pm

Hi Jirka

Thanks for the response. I tried to use Soil Catalog and Neutral prediction to get the Ks value but the values I get from these 2 methods are different though I selected the same textural class i.e Sandy Loam. Please see the two attachment files below. It's my first time using RETC model.
Attachments
Sand loam 2.PNG
Sand loam 2.PNG (15.54 KiB) Viewed 3867 times
sandy loam.PNG
sandy loam.PNG (34.83 KiB) Viewed 3867 times

Jirka
Posts: 4801
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Estimation of Hydraulic conductivity

Post by Jirka » Sun Aug 13, 2017 11:48 pm

Soil Catalog (Carsel and Parrish, 1988) and Rosetta (Schaap et al., 2001) comes from two different sources and thus give two different answers. J.

Carsel, R.F., and Parrish, R. S., Developing joint probability distributions of soil water retention characteristics, Water Resour. Res, 24, 755-769, 1988.
Schaap, M. G., Leij, F. J., and van Genuchten, M. Th., Rosetta: a computer program for estimating soil hydraulic parameters with hierarchical pedotransfer functions, J. of Hydrol., 251, 163-176, 2001.

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