Page 1 of 1

Error: initial water content condition is lower than Qr

Posted: Wed Jan 15, 2020 12:06 am
by ritadg
Dear Hydrus community,

I'm using HYDRUS-1D version 4.14 in the dual porosity model (mobile-immobile, water content mass transfer).
I'm modeling water flow, upper BC: atmospheric BC with surface run-off, lower BC: free drainage.

I run Hydrus through Matlab. I'm generating parameter sets, by giving the lower and upper limit for each of the nine paramters, plus LAI.
My initial water content is: 0.266. I gave the lower and higher limits for theta r (mob and imm) equal to 0.01 and 0.1.
So the residual water content is always lower than the initial water content.
But I keep getting the error message(not in all of the runs):

'Initial water content condition is lower than Qr !'

Which is not true, from what I can understand.

I appreciate a lot if someone could help me.

Thank you very much,
Rita

Re: Error: initial water content condition is lower than Qr

Posted: Wed Jan 15, 2020 4:11 am
by Jirka
It would be good to see the project when this happens. For a uniform flow model, this is pretty straightforward, but for a dual-porosity model it is more complicated. J.

Re: Error: initial water content condition is lower than Qr

Posted: Wed Jan 15, 2020 10:42 pm
by ritadg
Thanks Jirka,

Yes, it is weird.
I gave a close look into the parameters from the runs with this error but I couldn't find a relationship between them.
For example, I thought maybe high theta r from both mob and immobile parts combined with a high LAI could be generating this error.
Or maybe high theta with high K (because as it's free drainage below, it could mean that the water percolates to lower layers of the soil).
But I couldn't find anything that explained it, because the runs that worked had similar cases to the ones with error. :?

I attached 3 runs that failed (in .docx) so you can have a look if you want. I'm not sure if that helps.

Thank you very much for your attention,

Rita.

Re: Error: initial water content condition is lower than Qr

Posted: Wed Jan 15, 2020 11:19 pm
by Jirka
This is not particularly useful. Can you just post the entire project (with the inverse file)? J.

Re: Error: initial water content condition is lower than Qr

Posted: Wed Jan 15, 2020 11:38 pm
by ritadg
Hi Jirka,

Again, I thank you for your prompt reply.
I tried to attach the project but I'm not able to attach this kind of extension here.
How do you think I could send it to you?

Best,
Rita.

Re: Error: initial water content condition is lower than Qr

Posted: Thu Jan 16, 2020 12:01 am
by Jirka
No problem. Also, I usually simply zip the project and post it; and I have not encountered any problems with that. J.

Re: Error: initial water content condition is lower than Qr

Posted: Fri Jan 17, 2020 3:13 am
by ritadg
Hi Jirka,

I haven't zipped before :shock:
Now I'm sending my Hydrus run that is having this error: "Initial water content condition is lower than Qr ! "
I also included three more files with the .txt inputs (changing only soil parameters - thr, ths, Alfa, n, Ks, l, thrIm, thsIm, Omega - and LAI), that are generating the same error.

I really appreciate your help.

Thank you,
Rita.

Re: Error: initial water content condition is lower than Qr

Posted: Fri Jan 17, 2020 5:15 pm
by Jirka
You are using a dual-porosity model and specify the saturated water content of the immobile (Ths_im) and mobile (Ths_m) domains equal to 0.806 and 0.428, respectively. That is obviously possible since then the porosity would be larger than 1 (Ths_im + Ths_m = 1.334). That's the first problem.
Second: The initial water content condition (ThInitTotal) is 0.266. This gets distributed proportionally into the mobile and immobile domains: TheInitM=ThInitTotal* Ths_m / (Ths_im + Ths_m ) = 0.092, while TheInitIm = ThInitTotal - TheInitM =0.174. TheInitM is smaller than Ths_m.
J.

Re: Error: initial water content condition is lower than Qr

Posted: Tue Jan 21, 2020 5:59 am
by ritadg
Dear Jirka,

Thanks a lot for your elucidation.

Indeed, the first mistake was obvious. I didn't pay attention to that as I was used to model only with single porosity.
The second thing I didn't know that the initial water content is proportionally divided into mobile and immobile (which makes sense).
Where can I find those equations that you sent? I haven't found them in HYDRUS-1D - 4.17 manual.

Thank you very much,
Rita

Re: Error: initial water content condition is lower than Qr

Posted: Fri Jan 31, 2020 12:42 am
by ritadg
Hi Jirka,

I'd like to know if this equation of partitioning of the initial water content in the mobile and immobile region is in any HYDRUS manual or where I could find it.

Best,
Rita

Re: Error: initial water content condition is lower than Qr

Posted: Fri Jan 31, 2020 2:15 am
by Jirka
I have written the following sentence in the manual:
"When the dual-porosity model is used, the water content given in 2.69 is divided into the mobile and immobile domains proportionally to the ratios of porosities (saturated water contents) of the two domains (as this is the equilibrium state for the dual-porosity model with the water content-based mass transfer)."