Interpreting N loading/ routing for prioritizing the placement of riparian buffers

Hello InVEST community! :seedling:

I want to use the outputs of the NDR model to prioritize different areas for riparian restoration. One of the prioritization criteria is the amount of N loaded into a given stream reach. Riparian areas that receive a lot of N would be prioritized for restoration.

Is there a way to combine any of the NDR outputs to determine the amount of N that is loaded into/ routed through a given pixel, for example, pixels directly adjacent to a stream? Or better yet, a way to determine the amount of N that ends up in a stream reach?

Hi @atershy -

Unfortunately, the NDR model does not calculate nutrient deposition/retention like the SDR model does, and, given how SDR calculates it, I suspect that there’s not a straightforward way to manually do so.

The n_export.tif output does quantify how much N reaches a stream. If you can generate the catchments that drain to each stream reach, you could sum n_export.tif within each catchment to determine the amount of N that ends up in each reach.

One way you might try to create the reach catchments is using the InVEST tool DelineateIt. Theoretically it can take either point, line or polygon outlets, so if you have, say, reach line segments (based on the same DEM-derived stream network that was used as input to NDR), it may generate a watershed flowing to each. While I’ve used this tool many times with point outlets, I’ve not tried it with line or polygon, so am not sure how well this works, but it would be worth an experiment if you don’t have another favorite tool for the purpose.

~ Stacie