Dear Annu, kindly looked into @

http://civil.utah.edu/~mizukami/coursework/cveen7920/ETMeasurement.pdf

Hi Annu, 

here you can find something interesting using satellite (Landsat data) to estimate evapotranspiration:

http://www.ce.utexas.edu/prof/maidment/giswr2012/Ex5/Ex52012.pdf

But here you can find a paper comparing different method from data collected by lysimeter:

http://folk.uio.no/chongyux/papers_SCI/HYP_6.pdf

In addition some interesting issues:

http://meto.umd.edu/~zli/PDF_papers/Wang_et%20al_2006JD008351.pdf

http://edis.ifas.ufl.edu/pdffiles/ae/ae45900.pdf

I hope this can support you in your research.

Cheers, Valerio

Thanks both of you. This is exactly I am looking for. So I am starting my PhD and it revolves around the evapotranspiration, modelling it with simple physical thermodynamic approach. I have started reading the paper. But I always wonder is it that difficult. There are people who can calculate the total transpiration by plants by some GPP and all. Then we can easily calculate the contribution from the soil moisture.

As I am very new to this problem I would be interested to know what makes it so tough to estimate the evapotranspiration. Is it the plant contribution or the soil moisture. How much role the radiations play in it. If they play them how much the shortwave and how much the Long wave are responsible for it.

Annu, If interested in ET from ground water, pl have a look at this paper. Best, 

Article Groundwater resources assessment of the Koyna River Basin, India

Thanks pradeep Naik.... 

Dear Annu

There are different ways depending on the data that you have and each has its own advantages and disadvantages. It's also questionable whether you want to calculate it on daily basis or monthly basis.

You can follow the link also 

https://www.researchgate.net/post/Best_method_for_determination_of_ET_in_Himalaya

Hi vikram I want to calculate on daily basis. Can you also tell me more about the status and development in radiative and convective equilibrium in surface energy balance equations. 

Hi Annu 

If you want to calculate on daily basis then you can use standard method Penman–Monteith equation method as suggested in FAO. 

Steps to calculate you can find at

http://edis.ifas.ufl.edu/pdffiles/ae/ae45900.pdf

Even you can use CROPWAT software to calculate it if you have daily meteorological parameters.

As far as your other query is the concern I can't answer it. 

Thank you vikram. Actually we are working on it and we found that penmann equation don't represent the evapotranspiration well. As it lacks the proper radiative balance and impacted by vapour dificit. So it's still a question for me that how shall we tackel this problem. Well I have just started so don't have much knowledge. That why I am trying to understand step by step. Thanks for helping me.

Annu

Once you get it done and found something then do let me know.