Inverse model in HYDRUS - Water Content Profile

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litlux
Posts: 11
Joined: Thu Jul 04, 2019 4:24 am
Location: Korea

Inverse model in HYDRUS - Water Content Profile

Post by litlux » Wed Oct 02, 2019 12:28 am

Dear,

I am working on inverse model HYDRUS 1-D. We conducted an wetting experiment in vertical soil column and measure water content at different positions at the soil column until the certain time that we think it was almost saturated.

I applied that data set to inverse model in HYDRUS 1D. My data was not really "great" but the inverse model result was even weirder (as I attached image in this post). The water content profile from inverse model never reach fully saturated for the whole soil column. Anyone know why this happen?

Thank you so much for your help.

Best regards

Tho Tran
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Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Inverse model in HYDRUS - Water Content Profile

Post by Jirka » Wed Oct 02, 2019 12:57 am

I do not think that it is possible to comment on your project without knowing more details, at the minimum the boundary conditions. J.

litlux
Posts: 11
Joined: Thu Jul 04, 2019 4:24 am
Location: Korea

Re: Inverse model in HYDRUS - Water Content Profile

Post by litlux » Wed Oct 02, 2019 4:39 am

Dear Sir,

Thank you for your reply.

we have a loamy sand vertical soil column height of 66cm. We set the "groundwater level" is constant and simulated rainfall event with 1cm/hr precipitation. We assumed there is no evaporation.
The boundary condition I set in HYDRUS was
+ Upper boundary condition: Atmospheric BC with surface layer, 0 max h at soil surface
+ Lower boundary condition: Constant pressure head
The initial condition I set was that I assumed the pressure head varies from -66 to 0 (from upper surface to bottom of the soil column)
we measured water content through time at 5 positions along the soil column, using for inverse model in HYDRUS to optimize the hydraulic parameters of the soil.

I am looking forwards to hearing from you.

Best regards

Tho Tran

Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Inverse model in HYDRUS - Water Content Profile

Post by Jirka » Wed Oct 02, 2019 4:07 pm

The results look reasonable to me for the conditions that you described. I assume that the saturated water content is about 0.27 (the water content of the bottom node). Further I would assume that precipitation is smaller than Ks, and as a result, the profile will only reach the water content corresponding to K(h) equal to precipitation (which is about 0.24). What do you find unreasonable? J.

litlux
Posts: 11
Joined: Thu Jul 04, 2019 4:24 am
Location: Korea

Re: Inverse model in HYDRUS - Water Content Profile

Post by litlux » Fri Oct 04, 2019 4:18 am

Dear Sir,

Thank you so much for your reply. That would help a lot. I agree that it is because the boundary condition we set up and precipitation rate is smaller than Ks value.

Again, thank you.

Best regards

Tho Tran

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