Evaporation during ponded conditions

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ofsutton
Posts: 5
Joined: Fri Apr 20, 2018 1:09 am
Location: Canada

Evaporation during ponded conditions

Post by ofsutton » Thu Jun 20, 2019 3:11 pm

Hello all, I am getting strange behaviour of a recharge estimation model with an upper atmospheric boundary condition with surface layer and lower free drainage, root water uptake is considered.

I am adding a large quantity of water to the model in the first timestep to represent snowmelt (188mm) , and while it does infiltrate it mostly evaporates or transpires within the first 4 hours of the simulation (134mm of evaporation). My cumulative POTet during that time is 0, my LAI is also 0 (therefore no RWU, so there should not be any evaporation or transpiration).I have decreased the initial time step to be very small (fractions of a second). The mass balance also looks fine.
Actual_RWU.PNG
Actual_RWU.PNG (11.68 KiB) Viewed 217 times
Potential_RWU.PNG
Potential_RWU.PNG (11.66 KiB) Viewed 217 times
Atmospheric_Boundary.PNG
Atmospheric_Boundary.PNG (13.86 KiB) Viewed 217 times
Any thoughts on what could be causing this?

Thanks in advance for any help you can provide. Happy to provide model files if needed.

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

Re: Evaporation during ponded conditions

Post by Jirka » Thu Jun 20, 2019 4:11 pm

I can't help you if I do not see the h1d project. You are clearly doing something wrong. BTW, I will not be available during the next five days. J.

ofsutton
Posts: 5
Joined: Fri Apr 20, 2018 1:09 am
Location: Canada

Re: Evaporation during ponded conditions

Post by ofsutton » Thu Jun 20, 2019 4:17 pm

Thanks for your prompt reply Jirka. I have attached the project.

Cheers,
Attachments
URM_1972.zip
(801.28 KiB) Downloaded 17 times

ofsutton
Posts: 5
Joined: Fri Apr 20, 2018 1:09 am
Location: Canada

Re: Evaporation during ponded conditions

Post by ofsutton » Mon Jun 24, 2019 6:13 pm

I managed to get it to work by dividing the "snowmelt" into equal intervals over the course of the first 24 hours. This could have fixed the problem by decreasing the rate of water delivery to the surface to be less than Ksat, as ponding no longer occurs. Although I'm aware that this generally shouldn't be an issue...

However, I am still curious to know if there was a problem with my model parameters

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