Calculating seasonal R erosivity value?

Hi Nat Cappers,

I'm using both RIOS and InVEST to model erosion and nutrient exports in a watershed in Quebec (think similar agriculture and climate to Minnesota). In our system we know that most erosion and nutrient loss occurs in the fall rains, and spring melts & rains. 

I'm trying to think about how to best represent this within the SDR and NDR models as well as RIOS (Ièm trying to target agro-environmental practices).

One solution I was considere was trying to model only these two seasons by calculating the average annual precipitations in these periods, and also adjusting the R erosivity factor. In Quebec, these are the two seasons with the highest rainfall intensity. Since erosivity is usually calculated on an annual basis (and I've been cheating to date by using the global erosivity layer by Panagos et al 2017) I was wondering if you have any advice or guidance on how to do this? Or how to potentially use outputs from the Seasonal Water Yield model to do this. 

Any suggestions would be much appreciated.



  • PerrinePerrine Moderator, NatCap Staff
    Hi Sylvia,

    It's great to think carefully about the models' assumptions, both spatially and seasonally. 

    In this case, I'm not sure it's necessary to use seasonal data. Although the model uses annual inputs (annual erosivity R, or nutrient loads), it implicitly accounts for the seasonal budget, i.e. that most of the sediment will come during the fall and spring. This is because annual erosivity is the sum of erosivity values for individual rain events, so most of the total amount will be contributed by the spring and fall events.

    Unless you are explicitly interested in the sediment/nutrient budget from spring+fall, you can use the annual model results. Otherwise, you may use the annual results and take only X% of the sediment or nutrient export values (if you know the relative contribution from the spring and fall months).

    Also, if you are interested in prioritizing activities, you may want to check out the ROOT tool:, which may be easier than RIOS (I don't have direct experience myself but just want to flag it!)


  • Hi Sylvie -- building off Perrine's last comment, just a note that I've spent a lot of time comparing strengths and weaknesses of ROOT vs RIOS, so would be happy to discuss those with you if you are interested. Feel free to reach out directly (my username at, or start a new thread about your goals in that context.

    Best regards,
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