Equations

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epelde.ane@gmail.com
MOHID Advanced user
Posts: 172
Joined: Thu Jan 01, 1970 00:00

Equations

Postby epelde.ane@gmail.com » Fri Dec 30, 2011 14:33

Hi all!
I wonder how does mohid calculate actual evapotranspiration. I dont know if I´m right, so I write how I think it works..
ETP (ET0) with Penman-Monteith. then ETc (multiplying ET0 by Kc). And then, I saw that there are two ways to calculate the actual evapotranspiration.
The equation I found is:
ETactual=ETc·f·(AW/AWC) and, some authors consider the f=1 so the graph ET/ETP vs AW/AWC is linear, but others dont. So does mohid use this equation? and does it consider that function linear?
If it is like this, then, and using Feddes eq. (with which actual transpiration is calculated) ETactual-Tactual --> Eactual.
Does this make sense?

Have a good christmas!!! :D

davidbrito
MOHID Advanced user
Posts: 187
Joined: Thu Jan 01, 1970 00:00

Re: Equations

Postby davidbrito » Mon Jan 16, 2012 16:59

Hello,


1) ET0 with Penam Montheith
2) ETc with crop coefficient
3) then you have to ways:
3.1 if EVAPOTRANSPIRATION_METHOD : 2 you will have potential transpiration and potential evaporation (from ETc and separated by LAI)
3.2 if EVAPOTRANSPIRATION_METHOD : 1 you will only have potential transpiration (all ETc)
4) ActualEvaporation is computed in ModulePorousMedia at the surface
5) ActualTranspiration is computed in ModuleVegetation along the roots.
You have two options in WATER_UPTAKE_METHOD. if 1 first the potential transpiration is distributed in depth accordingly to root geometry and after with feddes (stress depending on water content) you will get Actual Transpiration = Potential Transpiration * Feddes Factor
6) After actual transpiration and actual evaporation are computed tey are putted together in basin result called evapotranspiration_rate

David

epelde.ane@gmail.com
MOHID Advanced user
Posts: 172
Joined: Thu Jan 01, 1970 00:00

Re: Equations

Postby epelde.ane@gmail.com » Tue Apr 10, 2012 13:25

Hello all :)
Can anybody check the transport equation at the module porous media properties,please? it doesnt appear in the wiki, it seems to be a kind of problem.. and, in tortuosity equation, the water content is elevated at 7/3 and the porosity elevated at 2?
Thanks!!

davidbrito
MOHID Advanced user
Posts: 187
Joined: Thu Jan 01, 1970 00:00

Re: Equations

Postby davidbrito » Thu Apr 12, 2012 11:14

Hello Ane,

I think it is done now. The property transport equation was to big to be in that format. now as a picture it works.

Best regards,
David


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