A discussion forum for Hydrus-1D users.
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Joined: Mon Nov 02, 2015 2:11 pm
Location: Yemen


Post by hazemalashwal » Tue Nov 03, 2015 2:19 pm

Dear, Jerka
in HYDRUS manual, the partitioning of ETP into EP+TP by this:

Ep=ETp*(1-SCF); Tp=ETp*SCF

And in another papers such as "Wöhling, T., & Schmitz, G. H. (2007). Physically based coupled model for simulating 1D surface–2D subsurface flow and plant water uptake in irrigation furrows. I: model development. Journal of Irrigation and Drainage Engineering, 133(6), 538-547.‏" and others, the equation of TP written as:

Tp=ET0*SCF* Kc

Also Kc was mentioned in VS2DT documentation (Lappala et al. 19870

And previously in other discussion (http://www.pc-progress.com/forum/viewto ... ?f=4&t=708) you said "I would personally recommend using the reference evapotranspiration (ET0), divide it based on surface cover fraction and use these values as potential transpiration and potential evapotranspiration. The code will then reduce these values based on soil conditions. When you multiply the reference evapotranspiration by the crop coefficient, you are already reducing evaporation from potential to actual values during earlier stages of flow (if I remember Kc coefficients start close to zero). However, for growth stages when the crop coefficient is larger than 1, then I would apply it on potential transpiration"
Thus, I still confused about which on should I use

this: Tp=ETp*SCF
or, this: Tp=ET0*SCF* Kc

if I want to simulate evapotranspiration for corn, and I have hourly ET0 data from automatic weather station.
waiting for your advice, thank you in advance>

Hazem Al-Ashwal

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