Overland Flow Errors

A discussion forum for users of the new HYDRUS 2D/3D. HYDRUS is a software package for simulating water, heat and solute movement in two- and three-dimensional variably saturated media. Happy Posting!
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JeffS
Posts: 3
Joined: Thu Jul 19, 2018 2:41 pm
Location: USA

Overland Flow Errors

Post by JeffS » Thu Jul 19, 2018 6:58 pm

Good Afternoon,

I am using Hydrus 3x with the overland module, in which I have a 1800 cm length domain and a height sloped between 350 and 300 cm with variable hourly data for precipitation, transpiration, and evaporation for about four months which is run 5 times. It has mostly Loam soil and a patch of Sandy Loam near the center for a length of 200cm and depth of 122cm. Occasionally at time steps it says overland has not converged and when looking at the error in the overland flow balanceO file, which I attached pictures of is very high. Do you have any suggestions to reduce the error and have the overland converge? I have tried different mesh sizes, time steps, and water content tolerance to reduce it. The lowest mesh size being 10 cm and the lowest water content tolerance of 0.0001, but I have been unsuccessful so far. My errors using the normal balance out file are 1% or lower. Any help would be appreciated.

Thank you,
Jeff
Attachments
Balance O capture ending.JPG
Balance O capture ending.JPG (271.67 KiB) Viewed 604 times

Jirka
Posts: 4620
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Overland Flow Errors

Post by Jirka » Thu Jul 19, 2018 7:27 pm

Note that on the webpage from which you can download this module we state: "Note that this module is not a standard part of HYDRUS (2D/3D). It is a nonstandard extension that we share with HYDRUS users without guaranteeing its numerical stability and robustness", and we actually mean it. From the examples posted on this webpage, you can also see that testing of this module was rather limited. I can only suggest that you use similar discretization and iteration criteria/precision tolerances similar as in these examples. J.

JeffS
Posts: 3
Joined: Thu Jul 19, 2018 2:41 pm
Location: USA

Re: Overland Flow Errors

Post by JeffS » Thu Jul 19, 2018 8:31 pm

Jirka,

Thank you for you quick response and suggestion.

Jeff

Jirka
Posts: 4620
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Overland Flow Errors

Post by Jirka » Thu Jul 19, 2018 10:34 pm

A good modeling practice is to always start from a simple problem (e.g., one rainfall event) and make it gradually more complex (extend it once a single event works). J.

JeffS
Posts: 3
Joined: Thu Jul 19, 2018 2:41 pm
Location: USA

Re: Overland Flow Errors

Post by JeffS » Thu Jul 26, 2018 4:17 pm

Jirka,

Thank you for that tip. I haven't been doing that, but will now.

Jeff

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