## hysteresis

A discussion forum for Hydrus-1D users.
Mitra
Posts: 27
Joined: Thu Dec 06, 2018 3:44 pm
Location: Switzerland

### hysteresis

Hello,

I am trying to account for hysteresis in my soil column. In the manual the subject is discussed on pages 31-35. However, I cannot find the parameter equivalent to "\theta_m^d" among the parameters when using HYDRUS software. Is it the same as theta_s^d?
Also, I cannot see exactly the difference between these hysteresis options:1. Hysteresis in retention curve( is it Scott et al. [1983]?)
; 2. Hysteresis in retention curve and conductivity (is it Kool and Parker [1987],); 3. Hysteresis in retention curve (no pumping, Bob Lehnard);
Do you mind distinguishing these options with their application and mass conservation (preferably with a reference that has used their formulations)?

Thanks,
Mitra

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

### Re: hysteresis

1. Hysteresis in retention curve: This model is based on Kool and Parker [1987]. Make Theta_m equal to Theta_s^d for the Kool and Parker [1987] model. Theta_m > Theta_s^d is an extension for Vogel and Císlerová [1988].
2. Hysteresis in retention curve and conductivity: This model is based on Kool and Parker [1987] extended to hysteresis in the conductivity curve as well.
3. Hysteresis in retention curve (no pumping, Bob Lenhard): This model is based on Lenhard et al. [1991] and Lenhard and Parker [1992] and eliminates the so-called pumping effect, which the Kool and Parker [1987] model suffers from.

All the references are given in the HYDRUS manual. Example 10 in the Hydrus manual deals with hysteresis.

J.