> 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/theoretical-documentation/section-3-nutrients-pesticides/chapter-3-1-nitrogen/3-1.7-upward-movement-of-nitrate-in-water.md).

# 3:1.7 Upward Movement of Nitrate in Water

As water evaporates from the soil surface, the water content at the surface drops, creating a gradient in the profile. Water from lower in the profile will move upward in response to the gradient, carrying dissolved nutrients with it. SWAT+ allows nitrate to be transported from the first soil layer defined in the .sol file to the surface top 10 mm of soil with the equation:

$$N\_{evap}=0.1*NO3\_{ly}*\frac{E''*{soil,ly}}{SW*{ly}}$$                                                                                                                            3:1.7.1

where $$N\_{evap}$$ is the amount of nitrate moving from the first soil layer to the soil surface zone (kg N/ha), $$NO3\_{ly}$$ is the nitrate content of the first soil layer (kg N/ha), $$E''\_{soil,ly}$$ is the amount of water removed from the first soil layer as a result of evaporation (mm H$$*2$$O), and $$SW*{ly}$$ is the soil water content of the first soil layer (mm H$$\_2$$O).