> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/basin-1/parameters.bsn/n_perc.md).

# n\_perc

This parameter controls the amount of nitrate removed from the surface layer in runoff relative to the amount removed via percolation.

{% hint style="info" %}
The smaller *n\_perc*, the lower the concentration of nitrate in runoff. If *n\_perc* = 1.0, the surface runoff will have the same nitrate concentration as the percolate.
{% endhint %}