Input preparation

Hi all, I am starting to use the InVEST tool, and as a beginner, I am finding some problems especially in the input preparation. I am trying to follow the user manual but there are a few things that are not fully clear for me (sorry if I am asking basic questions but forgive me, I insist I'm a beginner!) I did the MOOC, which helps a lot, but the inputs were already provided. I understand the whole thing and I think the tool is awesome, that's why I'd like to know how to handle it well, so it can be useful for my job.

My case: A water yield model of a watershed in Colombia. I am using QGis for data preparation

I've got the vector files for watershed, sub-watersheds, ok here

I've also raster files for:
precipitation (monthly)
Reference ET. Global map of reference evapotranspiration:
land use.

Talking about the water yield model:
Input on Plant available water fraction and root restricting layer
depth. I don't really know how to get these 2 raster layers. My

For root restricting layer depth, according to user
manual, it can be obtained from some soil maps. I tried to look at some
of the links of the manual, but I wasn't able to get the data for the
place I'm interested. How can I get it?
For pawc, I understand from
the manual that it should be acquired through a calculation with soil
depth, but it is not clear to me how to get this raster input layer.
would appreciate some guidance with these issues, maybe my language
understanding is not perfect and I might be missing something that is
actually explained there.

About the csv table for biophysical cofficients, can be used the same as the sample data for Cauca given in the MOOC?

Thanks in advance to all the community, your help would be more than appreciated,



  • swolnyswolny Member, NatCap Staff
    Hi Alex -

    Which soil maps are you looking at? Some soil maps that are more regional tend to only give information on the soil class and not any additional information like soil depth, PAWC etc. Colombia should have better soil data though, perhaps through IGAC? Globally, the FAO Harmonized World Soil Database definitely has these values, although at a coarse scale. If you choose to work with the HWSD, there is information on how to derive soil depth and PAWC in this forum thread. Similar processes can be applied to SOTER or other soil databases.

    As for the biophysical coefficients used in Cauca, you could use them to get started with your analysis, but I strongly recommend doing a literature search to look for values that are more appropriate to your specific area, land cover types, etc, so that you understand the source, accuracy and uncertainty of those values.

    ~ Stacie
  • Thanks a lot Stacie,

    I've been out the last few weeks, sorry for not answering before.

    I still need to explore IGAC. It has a lot of information that could be helpful for me. About PAWC, soil depth, etc... I tried to use SOTER and HWSD to derive these data and tried to follow the forum thread you mentioned, but it has been impossible for me at this moment. First step was to open the documents in ARCgis but in my QGIS seem to be impossible. As you can see, I posted a question in the forum thread to see if anybody can help me.

    I would appreciate it if you could give me a bit more detailed help on how to prepare intup information, I don't know if I can find tutorials, or other detailed manuals to do it.

    Thanks for your attention, I really appreciate your help. btw, about the other data I told you that I already had (land use, ET,...) do you think are they ok?

    Thanks a lot,

  • Hello, Natcap staffs and experienced users!!

    I have the SSURGO raster data for Kentucky. Is it good to go once I clip or mask the areas I am working or I shall do some processing?

    I have spent a lot of time trying to figure out the soil depth, water content etc.

    I am new to inVEST and GIS and shall be using these for my research as a graduate student. Thank you very much.

  • swolnyswolny Member, NatCap Staff
    Hi Kumari -

    If you have already done the calculations for AWC, soil depth, etc, and made sure that they are in the correct units, you should be able to join the results to the SSURGO soil shapefile, clip to your area of interest and turn the shapefile into a raster. The raster will be used in the water models.

    And I'm not sure which GIS you're using, but if it is ArcGIS, I hope you know about the USGS Soil Data Viewer, which will do these (and many other) calculations for you, even creating a map that you can save as a shapefile. It can also be run outside of Arc and do calculations for you, but will just generate a report, not spatial data. Still, it saves you a lot of work...

    ~ Stacie
  • LyndsyLyndsy Member
    Hello everyone,

    I am also fairly new to both ArcGIS and to InVEST. I have already worked my way through the MOOC, but since the data is already prepped and provided, I am really stuck on getting my data together. I am working my way though the Water Yield model, although I am planning to get to the Sediment Retention and Water Purification models as well.

    Can anyone suggest specific sets of instructions or tutorials for getting the data, for example Plant Available Water Content and Root Restricting Depth Layer, and getting it in the right format.

    Thank you so much!

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