Seasonal Water Yield Model - Crop Factors (Kc)

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Hello, I am wondering if anyone knows of a good resource for crop factors (Kc) that can be used for general land use / land cover categories. I have found resources for specific species, but I am looking for more general parameter ranges for National Landcover Datasets. Thank you.

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Dear Jessica,
Yes, that is a huge problem in this model, for there are very few sources of Kc values for natural landcovers, especially for tropical landscapes (my case).
In that, I have two suggestions for you:

1) Check out this article:
“Environmental controls on seasonal ecosystem evapotranspiration/potential evapotranspiration ratio as determined by the global eddy flux measurements” (Liu, et al., 2017)
It has monthly average Kc values for several natural landcovers around the world. However, it is a global model, so final results might not be accurate depending on your study area.
2) Follow the step-by-step on how to calculate Kc values for crop seasons indicated on
“Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56”, CHAPTER 6 (ETc - Single crop coefficient (Kc))

Personally, I had better results (not good results, though) using the values estimated with the FAO guidelines. Also, the INVEST manual sugests some Kc values on the “Annual Water Yield” model chapter. Hope I could help.
Best regards,
Victor

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Hi Victor,
Thank you. The Liu et al. (2017) paper was especially helpful. I am wondering if there are similar papers for developed lands. I know the annual water yield model documentation provides a calculation for annual average Kc values based on % impervious surface, but not monthly or seasonal values.
Thank you for all your help,
Jessica

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HI @jbmoon,

Thanks for interacting with the NatCap forums! From searching the InVEST Users Guide Seasonal Water Yield model, it looks like the only bit of recommendation is:

Monthly Kc values (fields Kc_1 through Kc_12 ) can be obtained from the FAO guidelines: (Allen et al., 1998)

Hopefully more community members will come by and chip in!

Cheers

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Hi there,

you may also want to look at https://www.researchgate.net/profile/Margarit-Nistor/publication/323015339_Land_cover_and_temperature_implications_for_the_seasonal_evapotranspiration_in_Europe/links/5ac46de70f7e9becc9d4a25d/Land-cover-and-temperature-implications-for-the-seasonal-evapotranspiration-in-Europe.pdf

If I may add a question about Kc values: I am dealing with the Alps and wonder what to enter for winter/cold season (in Nistor et al. 2018 most are (-)), a 0.00?

Bests,

Felix

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Hi @fconitz,
I think you can enter 0 for Kc anywhere that plants are dead or covered with snow. Kc is “a coefficient expressing the difference in evapotranspiration between the cropped and reference grass surface” (FAO guide). I think it’s safe to assume that plants that are dead in the winter or covered in snow do not evapotranspirate significantly. So their evapotranspiration is 0% of the reference grass amount.

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Hi @esoth ,
thanks for your reply!
Sounds definitively reasonable :slight_smile: . I will enter 0 for Kc where logical^^

Best,
f

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