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).