question about surface runoff

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swps
Posts: 3
Joined: Tue Sep 01, 2009 9:31 am

question about surface runoff

Post by swps » Fri Aug 12, 2011 7:00 am

Hi

I am using hydrus 2D version 2.05 for simulate water flow in the soil. In my experimental site we have surface runoff. Will you take into account for the variation on the amount of runoff?

Thank you
Nuttacha

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

Post by Jirka » Fri Aug 12, 2011 7:15 am

Any excess water (in excess of the infiltration capacity) is assumed in HYDRUS to be instantaneously removed by surface runoff. This is a reasonable assumption, assuming that the surface runoff acts in much shorter time scales than infiltration and subsurface flow. However, obviously, you can not have, with this assumption, reinfiltration at other locations.

Jirka

swps
Posts: 3
Joined: Tue Sep 01, 2009 9:31 am

Post by swps » Fri Oct 28, 2011 11:06 am

Dear Jirka,

Thank you Jirka. I still have question. I have GWL below surface around 5 meter. I don't know about boundary condition at the bottom that I should use between no flux and constant pressure head.

Thank you

Nuttacha

Jirka
Posts: 4799
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Post by Jirka » Fri Oct 28, 2011 1:52 pm

It depends if your domain extends all the way towards the GWL. If it does, and the GWL level can fluctuate as a result of what's happening in the soil profile, then zero flux seems to be the best option. If it should stay constant, then use constant head BC.


If the domain does not extends all the way towards the GWL, then use free drainage BC.

J.

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