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!

What do Land cover classes here?

Hi @jhonalbert , welcome to the forums! I’m sorry, I don’t understand your question. Are you asking about what land cover classes are, or something else?


Yes, you are right. I’m asking about what land cover classes are?

Hi @jhonalbert ,

Thanks for your question. If this discussion will continue much further, I suggest we create a new thread within the “Training” category.

The following is from Horning, N. 2004. Land cover classification methods, Version 1.0. American Museum of Natural History, Center for Biodiversity and Conservation. Available from (accessed on February 4, 2022):
…land cover is what covers the surface of the earth… Examples of land cover classes include: water, snow, grassland, deciduous forest, and bare soil.
Although the terms “land cover” and “land use” are sometimes used interchangeably, they are actually different… land use describes how the land is used… Land use examples include: wildlife management area, agricultural land, urban, and recreation area.

Land use / land cover (LULC) data are input into InVEST models as rasters files. Details are available in our User Guide, here. There, we define LULC as describing “…the physical properties of the land and/or how people are using it (forest, wetland, water, paved, agricultural, nature preserve, etc.) In order to display the data in raster format, each LULC category is mapped to an integer code (these codes do not have to be consecutive or ordered).

I hope this answers your question!

Be well,

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