# How obtain the values of eff\_n , eff\_p, crit\_len\_n, and crit\_len\_p in model NDR?

**URL:** <https://community.naturalcapitalalliance.org/t/how-obtain-the-values-of-eff-n-eff-p-crit-len-n-and-crit-len-p-in-model-ndr/2032>\
**Category:** Software Support\
**Tags:** ndr\
**Created:** [July 2, 2021, 2:31pm UTC](https://community.naturalcapitalalliance.org/t/how-obtain-the-values-of-eff-n-eff-p-crit-len-n-and-crit-len-p-in-model-ndr/2032 "2021-07-02T14:31:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Fermin](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/fermin/32/2087_2.png) [@Fermin](https://community.naturalcapitalalliance.org/u/Fermin)\
**Post date:** [July 2, 2021, 2:31pm UTC](https://community.naturalcapitalalliance.org/t/how-obtain-the-values-of-eff-n-eff-p-crit-len-n-and-crit-len-p-in-model-ndr/2032/1 "2021-07-02T14:31:00Z")

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Hi,  
I am working with the NDR in the river watershed Reventazón in Costa Rica, and I have a question about eff\_n, eff\_p, crit\_len\_n and crit\_len\_p.

¿How I could obtain eff\_n , eff\_p, crit\_len\_n, and crit\_len\_p value?, ¿Is there a database that your know to obtain this data?.

Greetings,  
Fermin V.

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**Author:** ![swolny](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/swolny/32/181_2.png) [@swolny](https://community.naturalcapitalalliance.org/u/swolny)\
**Post date:** [July 6, 2021, 3:36pm UTC](https://community.naturalcapitalalliance.org/t/how-obtain-the-values-of-eff-n-eff-p-crit-len-n-and-crit-len-p-in-model-ndr/2032/2 "2021-07-06T15:36:52Z")

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Hi @Fermin -

These values are, admittedly, harder to find. We typically do a literature search to see if nutrient retention studies have been done in our area (or a nearby/similar area), and I recommend doing that, to try and match the values as well as possible to the local conditions.

If these are not available, we do provide a Nutrient Database of literature sources from around the world, which you can find in the [Data Sources for InVEST section of the InVEST web page](https://naturalcapitalproject.stanford.edu/software/invest). Note that it is rather old, and non-exhaustive, which is why I recommend doing your own research as well.

~ Stacie