Mass Balance Question

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crhansen
Posts: 21
Joined: Thu Dec 03, 2015 4:21 pm
Location: Canada

Mass Balance Question

Post by crhansen » Tue Mar 26, 2019 4:22 am

I am testing the water balance within HYDRUS-1D using a 50 cm thick soil profile, 2.5 cm of surface ponding allowed, one year of recorded hourly rainfall data ( multiplied by a factor of 10 to account for off-site runoff), Ks=.5 cm/hr, and PET = 0. The model is identical to the HYDRUS-1D Fig. 5b Tutorial, except for the rainfall amount, length of simulation, and Ks value. The models runs fine and there are no errors or warning messages. Initial water content is set to the field capacity. The water balance from T_LEVEL.OUT is as follows:

Rainfall = 1349.2 cm (this is sum(rTOP)
sum(Runoff) = 519.6 cm
sum(Infil) = 733.1 cm
sum(Evap) = 0.0001 cm

So the sum of Runoff plus Infil is 1252.7 cm, which represents 92.8% of the Rainfall. I am not clear on where the remaining 7.2% of the rainfall went. Can someone please comment or suggest an explanation. The discrepancy in the water balance tends to increase as the ponding depth increases (e,g, I tried changing the maximum ponding depth to 7.5 cm and 22.5 cm).

Colin

Jirka
Posts: 4759
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Mass Balance Question

Post by Jirka » Tue Mar 26, 2019 7:19 am

I’m currently giving a HYDRUS course in Prague and will not have time to look at this. J.

crhansen
Posts: 21
Joined: Thu Dec 03, 2015 4:21 pm
Location: Canada

Re: Mass Balance Question

Post by crhansen » Thu Apr 04, 2019 3:11 am

Jirka,

My compressed HYDRUS-1D file is attached. When you have a moment, I would appreciate it you could run the file. It runs in about 5 seconds on my laptop.

Thanks Again,

Colin
CHansen_HYDRUS-1D.zip
(348.51 KiB) Downloaded 35 times

Jirka
Posts: 4759
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Mass Balance Question

Post by Jirka » Sun Apr 07, 2019 6:38 pm

When I use my latest exe files I get the right fluxes and almost zero mass balance errors.
Rainfall = 1349.3 cm (this is sum(rTOP)
====================
sum(Runoff) = 541.7 cm
sum(Infil) = 806.6 cm
sum(Evap) = 0.0001 cm
====================
sum 1348.3 cm

Replaced the attached exe files in your HYDRUS folder. J.
h1d_calc_i.rar
(1013.01 KiB) Downloaded 31 times

crhansen
Posts: 21
Joined: Thu Dec 03, 2015 4:21 pm
Location: Canada

Re: Mass Balance Question

Post by crhansen » Wed Apr 17, 2019 2:42 am

Jirka,

I replaced the .EXE files as you suggested and got the same result you report

Thanks for your help.

Colin

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