water balance

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!
Post Reply
OULIGEI
Posts: 18
Joined: Mon Nov 16, 2020 10:56 am
Location: China

water balance

Post by OULIGEI » Thu Nov 24, 2022 7:59 am

Hi Jirka
I am trying to do a water balance calculation for a model, but I am having a bit of a problem. Firstly, I am extracting the inflow and outflow from “CUM_Q.OUT”. Secondly, I get the total water storage of the model in “BALANCE.OUT”. However, I found that there are always some differences between them. The first is the accuracy of the water storage; it is only accurate to ten digits, while the inflow and outflow are accurate to two decimal places. In some periods, the error of water balance can exceed 5%. I want to ask if the water inflow and outflow in the model are strictly equal to the change in water storage, and if there is an error, is there any way to improve the accuracy?
Attachments
$2{R8MKN(})0@F92@J}C{AM.png
$2{R8MKN(})0@F92@J}C{AM.png (16.4 KiB) Viewed 29 times

Jirka
Posts: 5610
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: water balance

Post by Jirka » Thu Nov 24, 2022 7:57 pm

Water balance errors are calculated internally by the model and reported in the Balance.out file as absolute (WatBalT) and relative (WatBalR) error. Finer discretization should lead to smaller mass balance errors. J.

OULIGEI
Posts: 18
Joined: Mon Nov 16, 2020 10:56 am
Location: China

Re: water balance

Post by OULIGEI » Fri Nov 25, 2022 1:50 am

Thank you very much for your prompt reply!
I checked the relative (WatBalR) error, which is less than 1 % for most simulation time, but the absolute (WatBalT) error cannot be ignored. It is sometimes over the Q3(two CumQ3 diminish) in my model. Is there any way to improve the accuracy of the water storage calculation? The accuracy of this value is only ten digits which is confusing to me, I would like to get the inflow and inflow equal to the water storage variation or the absolute (WatBalT) error between the two is less than 10 (L*L)

Jirka
Posts: 5610
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: water balance

Post by Jirka » Fri Nov 25, 2022 9:28 pm

I do not know what else I can add here than what I have written before.

“Water balance errors are calculated internally by the model and reported in the Balance.out file as absolute (WatBalT) and relative (WatBalR) error. Finer discretization should lead to smaller mass balance errors.”

The absolute (WatBalT) and relative (WatBalR) errors are obviously related, as described in the manual. J.

Post Reply