The input data of NDR

Hello, Community! Hope everyone is well!
I am doing an assessment of water purification ecosystem services in a certain region and all the literature uses potential evapotranspiration raster data when using the InVEST model, but the model window does not ask for this data, and I can run successfully without entering potential evapotranspiration data, why is that? Also, all the data for TN and TP are available in the biophysical table, but there is always an error in the model window when I check Calculate Ni trogen Retenti on and Calcul ate phosphorous retention, why?
Thanks a lot.

Hi @littlepencil , thanks for posting,

Checking the User’s Guide, it doesn’t seem like any of the model’s computations require evapotranspiration. I’m not an expert in this field, so I can’t really explain why that might be surprising. Would you like to share some of the literature that you refer to?

Could you please post the content of the error message? You can see it by clicking the red X, or by clicking the Run button. Most likely there’s just a minor issue with formatting in the biophysical table. You could upload your table here if you can’t identify the problem.

Hi @littlepencil -

Can you provide more detail about “all the literature uses potential evapotranspiration raster data when using the InVEST model”? We do have two models that require potential evapotranspiration data (Annual and Seasonal Water Yield), but NDR does not require PET/ET0. Some people use the InVEST Annual or Seasonal Water Yield model to create the “Nutrient runoff proxy” input to NDR, so perhaps this is the case in the literature that you’re referring to?

~ Stacie

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thank you, my friends!
For the second question, I attach the error results for your reference, and again, thank you for your guidance and answers from experts and friends
The error warning is as follows:
“ValueError encountered:Missing header proportion_ subsurface_ n from D:/08_ DataCoIIect/ TheGreatBay/GuangDong/05_ tabIe/biophysicaI_ table_ gba.sv See the log for details.”

Thank you very much for your answer,!
maybe you are right that the potential evapotranspiration raster data is only used in the Water Yield model. By the way, the Nutrient Runoff Proxy (Raster) data can be replaced by the annual average precipitation, right?

Hi @littlepencil -

When reporting an error, it’s very helpful for us if you attach the entire log file (.txt) that the model creates in your Workspace - thanks!

Regarding the ValueError, are you using NDR to evaluate nitrogen? If so, does your biophysical table have a column named “proportion_subsurface_n”? I see now that the User Guide says that this column is optional, but if you’re evaluating nitrogen it might actually be required, even if the values in this column are all zeroes. Try adding this column (with values of 0s to test) and see if the error goes away. Meanwhile, I’ll talk with the software team and update the User Guide to be more clear.

And yes, you can use annual average precipitation for the Nutrient Runoff Proxy input.

~ Stacie

Dear Friends.
Thank you very much! According to your suggestion, I added “proportion_subsurface_n” to excel, and when I run it again, it doesn’t report any error. I set all the values to 0 and it won’t have any effect on the results, right? I would like to get your professional answer, thank you!

Hi @littlepencil -

When we set the values of proportion_subsurface_n to 0, that is saying that all of the nitrogen moves across the landscape with surface runoff, none of it goes to the subsurface. This is the recommended default way to use the model, unless you have information that tells you that some portion of nitrogen does go into subsurface flow.

If you do choose to model subsurface flow, the model will do an extra calculation (see equation 41 in the User Guide) that gives a very simple estimate of the amount of nitrogen that reaches the stream to subsurface flow, as differentiated from surface. So it will change the results somewhat, in that you’ll have two different results for nitrogen export (surface and subsurface) instead of one (just surface).

~ Stacie

Hi swolny:
I checked the results after running successfully, but compared to the results in the official documentation(InVEST 3.2.0 User’s Guide_20171008), there seems to be a lot of data missing, mainly the retention data of nutrients based on pixel and shapfile formats. For example, p_avl_tot/n_avl_tot (kg/ha), p_ ret_ tot/n_ ret_ tot (kg/watershed), p_ ret_ adj/n_ ret_ adj (kg/watershed), p_ retention.tif (kg/ pixel).Could it be that some parameters are still missing in the biophysical table?
The main parameters in my biophysical table are description、lucode、usle_c、usle_p、load_p、eff_p、load_n、eff_n、crit_len_p、crit_len_n、root_depth、Kc、LULC_veg and proportion_subsurface_n
The result of a successful run of my model is shown below

Hi @littlepencil
I have same question. I want to get N_retention.tif and P_retention.tif, but the results of NDR may can not build them. Could @dave give us some suggestions?

Hi @littlepencil and @asuleo -

InVEST 3.2.0 is VERY old and we no longer support it. I recommend using the latest version, which is 3.9.0. Some of the parameters and outputs of version 3.9.0 are different than the 3.2.0 nutrient model, so if you are actually running InVEST 3.9.0, but looking at the User Guide for 3.2.0, there will be a lot of inconsistencies. Please see the User Guide for 3.9.0 instead.

And as I noted in this post from @asuleo, unfortunately the current NDR model does not provide a nutrient retention result.

~ Stacie

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Yes, I did see in other literature to use data on potential evapotranspiration, etc., which I screenshot below with the relevant literature


doi: 10.3390/land6030048

Hi @littlepencil -

Those are not inputs to the NDR model, they are inputs to the Annual Water Yield model. Sometimes people use the Annual Water Yield model to create the Runoff Proxy input to NDR, but they are separate models. NDR does not require evapotranspiration, Water Yield does, as noted previously in this thread.

~ Stacie

Thanks! I see, does that mean I can get both the n/p_retention and n/p_export with the previous version (although there may be changes in the input data, such as replacing the current average annual precipitation with the potential evapotranspiration)?

Version 3.2 is so old I don’t really remember how it worked, and we don’t provide it for download any more, so I can’t go back to look at the documentation. But the model is different now because we are using methods that we feel are significantly better than were used in the old version, and in particular there was a lot of uncertainty around the retention calculations, so I can’t recommend using the old version.

We generally model nutrient retention by looking at the difference in nutrient export between the baseline landscape/management practices and a scenario where the landscape or management has changed. Of course, this only works if you have scenarios, and only provides an idea of how the change in landscape/management affects things, it does not provide a static idea of retention within a single scenario.

~ Stacie

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Well, thank you very much, according to all your answers, the concept of “relative” for this model may be more helpful to understand the model, or to do research on it. :grinning: