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:

Nevap=0.1NO3lyEsoil,lySWlyN_{evap}=0.1*NO3_{ly}*\frac{E''_{soil,ly}}{SW_{ly}} 3:1.7.1

where NevapN_{evap} is the amount of nitrate moving from the first soil layer to the soil surface zone (kg N/ha), NO3lyNO3_{ly} is the nitrate content of the first soil layer (kg N/ha), Esoil,lyE''_{soil,ly} is the amount of water removed from the first soil layer as a result of evaporation (mm H2_2O), and SWlySW_{ly} is the soil water content of the first soil layer (mm H2_2O).

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