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Seasonal water yield monthly evaporation?

Dear everyone:
I want to acknowledged that what method  the seasonal water yield use to calculate the monthly evapotranspiration. In the user's guide I can not get useful information ,Could you please give the formula . The second question of mine was that the quick flow is real or just an index that tell user the relative number which could represent the higher or lower ability to produce quick flow, It can not be calibrated through the real observe data? 
Thank you very much ! 


  • swolnyswolny Member, NatCap Staff
    Hi @Liwei_hello -

    Are you asking about what method to use to create the monthly evaportanspiration that is an input to the model? There are several methods that you can use. The one that I usually use (because it requires the easiest-to-obtain data) is Modified Hargreaves. Sorry that our user guide does not list some of these options in the Seasonal Water Yield section, but we do list several of these methods in the Annual Water Yield Data Sources section. Doing a literature search will also provide more options, and you can decide which one is most appropriate for the data that you have and the place that you are working in.

    The quick flow value is a real value that you can use for calibration. The baseflow value is an index.

    ~ Stacie
  • Hi @swolny
    First,thanks  for your explanation with great patience, I feel sorry that I do not state my question clearly, what I want to know was that how the seasonal water yield model to calculate the monthly actual  evapotranspiration,not the reference evapotranspiration. Could you please list some literature that describe the method with more detail? I feel sorry that I can not figure out the  formula that listed in the user's guide. Second, Could I use the observed runoff value to compare with quick flow value, and then calculate the correlation coefficient for calibration ,Maybe there were some other method for calibration that I have no idea,yet. Could you please give some good advice, Thank you very much for your help.
    Have a good day!
  • RichRich Administrator, NatCap Staff
    AET monthly is calculated per cell as either the amount of water available for evapotranspiration in that month, or the PET in that month, whichever is smaller. This is Figure 1 in the user's guide. The amount of water available is a little complicated because you need to route water downhill through the watershed while also accounting for upstream AET as it flows. As far as I know, this is a model developed by several scientists at NatCap, lead by Perrine Hammel @perrine. There is a paper in preparation, but the math is the same as what's in the user's guide now. But I'd be happy to help further if you can let me know what you're struggling with.

    And I'm not sure about calibration, but what you propose sounds reasonable. And reading the user's guide it sounds like adjusting monthly alpha values might be a way to do that. Maybe @perrine can comment further.

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