Confusion/request for guidance on the Hysteresis model

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Hydraus_1d_RD
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Confusion/request for guidance on the Hysteresis model

Post by Hydraus_1d_RD » Thu Dec 24, 2020 7:40 pm

Dear all, For a particular problem that I am trying to simulate using Hydrus1D I would like to use a hysteresis model that considers hysteresis in both water content and pressure head and relative hydraulic conductivity and pressure head relationships. I'm especially interested in applying the Bob Lenhard method. My confusion is that the screen description for this selection only says "Hysteresis in retention curve (no pumping, Bob Lenhard)". Would you please let me know if I select this option, then am I only considering theta(h) hysteresis and not also K(h) hysteresis ? How can I consider both hysteresis types with no pumping effect?
I'd really appreciate your help.
Sincerely,
a Hydrsu-1D user

Jirka
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Location: Riverside, CA

Re: Confusion/request for guidance on the Hysteresis model

Post by Jirka » Thu Dec 24, 2020 8:25 pm

The hysteresis model of Lenhard et al. [1991] and Lenhard and Parker [1992] that eliminates pumping by keeping track of historical reversal points has indeed been developed only for the retention curves. There will obviously be a corresponding hysteretic effect on K(h), although the K(theta) function will not have a hysteretic effect. J.

Hydraus_1d_RD
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Re: Confusion/request for guidance on the Hysteresis model

Post by Hydraus_1d_RD » Fri Dec 25, 2020 7:46 pm

Thank you!

Jirka
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Location: Riverside, CA

Re: Confusion/request for guidance on the Hysteresis model

Post by Jirka » Fri Dec 25, 2020 11:52 pm

In the figure below you can see the hysteretic loops for example 10 (described in the manual and distributed with the software). Jirka

hysteresis.png
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hysteresis.png
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Hydraus_1d_RD
Posts: 16
Joined: Thu Dec 17, 2020 10:11 pm
Location: USA

Re: Confusion/request for guidance on the Hysteresis model

Post by Hydraus_1d_RD » Sun Dec 27, 2020 5:26 am

Thank you. Would you please let me know how can one estimate theta_s for both main wetting and drying curves separately? Are there any guidelines or rules of thumb for estimating them separately?
Sincerely,

Hydraus_1d_RD
Posts: 16
Joined: Thu Dec 17, 2020 10:11 pm
Location: USA

Re: Confusion/request for guidance on the Hysteresis model

Post by Hydraus_1d_RD » Sun Dec 27, 2020 5:54 am

I have one more request. Would you please let me know the method used in generating those figures? After reviewing the Test10 model setup and output files I noted the soil column is 72 cm long and it is discretized into 73 nodes. Therefore, I'm not sure if the theta(h) plot is at a specific location or for the whole soil profile. I'd appreciate your help in understanding how to generate those types of figures.

Thank you!
Sincerely,
an Hydrus-1D user

Jirka
Posts: 5216
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Confusion/request for guidance on the Hysteresis model

Post by Jirka » Sun Dec 27, 2020 7:33 pm

I do not advise on experimental procedures. Ultimate source usually is:

Dane, J. H., and G. C. Topp (eds), Methods of Soil Analysis, Part 4, Physical Methods, Chapter 1.7, Third edition, SSSA, Madison, WI, 139-157, 2002.

Figures on the left were done using the results from output file Obs_node.out. There is no simple way of making the figures on the right. I general, you need to relate theta (from obs_node.out) with K.

J.

Hydraus_1d_RD
Posts: 16
Joined: Thu Dec 17, 2020 10:11 pm
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Re: Confusion/request for guidance on the Hysteresis model

Post by Hydraus_1d_RD » Mon Dec 28, 2020 6:30 pm

Thank you so much!
Sincerely,
A Hydrus-1D user

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