AWY and carbon storage results

Hello there!

i was modelling annual water yield and carbon storage, but when i see the results i think there is a problem, AWY values are too large and carbon storage are too low.

It´s a suposition. In that way i would like to know if you can check the results attached in the screenshot.

If those values are uncommon, what could be causing this?

Thank you.

Hi @mfcnico -

What do each of those list entries represent? Watersheds? Countries? Land cover classes? Something else? And how did you calculate those aggregated values?

~ Stacie

Hi Stacie,

  • Those points represent random pixels in a watershed.
  • The aggregated values are the results of the invest process that is contemplated on the user guide.

we think AWY results (Volume) are too large taking into account the units that user guide shows.

i hope you understand our question, thanks for your help.

Thanks for the clarification @mfcnico.

For carbon, as noted in the User Guide, the units are megagrams per pixel. How large are your pixels? What kind of vegetation is in those pixels?

For water yield, the per-pixel outputs for AET and water yield are provided are in millimeters, not volume. Volume is provided for each (sub)watershed. Which output layer are these values coming from? wyield_[Suffix].tif?

~ Stacie


Hi Stacie, thanks for your reply and sorry for the late answer.

Regarding the previous question, we’re using the output\subwatershed_results_wyield_[Suffix].shp and those values are wyield_vol.

As you can see, we attached a screenshot of the attribute table.

If the wyield_vol are in (m3), those values have any sense? if not, what could be doing wrong?

Also, we want to know how much water is in the watersheed, which value do you recommend for this?

We appreciate you help!

Without knowing more about your area, it’s kind of hard to say whether these numbers are reasonable. Given the simplistic nature of the model, the output values are rarely precise, which is why we recommend calibrating them against observed data if you can (and using relative values, not absolute, if you can’t). Do you have observed annual stream flow data for any of these subwatersheds?

Aside from model simplicity, I’d take into account a few things when evaluating these results:

  • The area appears to be getting ~1.5 meters of rain a year - that’s a lot.
  • Only around 1/3 of that is being lost to ET, so much of the rest will be considered water yield.
  • Is the Shape_Area value in square meters? And is it correct for these polygons? They do seem on the small side for that water yield volume, but maybe not, given how much rain falls.

~ Stacie


thank you so much, we appreciate your help!