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Module Basin

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Overview

Main Processes

Evapotranspiration

Some water may disappear from the soil because of the evaporation and transpiration processes, which become a sink in soil water profile. These two processes, currently named Evapotranspiration may be modeled using the Penmann Monteith equation.

 \overset{\text{Energy flux rate}}{\lambda_v E=\frac{\Delta R_n   +   \rho_a c_p  \left(  \delta q  \right) g_a }{\Delta  + \gamma \left (    1 + g_a / g_s    \right)}}~ \iff ~  \overset{\text{Volume flux rate}}{ET_o=\frac{\Delta R_n   +   \rho_a c_p  \left(  \delta q  \right) g_a } { \left(   \Delta  + \gamma \left (    1 + g_a / g_s    \right)    \right) \lambda_v }}

λv = Latent heat of vaporization. Energy required per unit mass of water vaporized. (J/g)
Lv = Volumetric latent heat of vaporization. Energy required per water volume vaporized. (Lv = 2453 MJ m-3)
E = Mass water evapotranspiration rate (g s-1 m-2)
ETo = Water volume evapotranspired (m3 s-1 m-2)
Δ = Rate of change of saturation specific humidity with air temperature. (Pa K-1)
Rn = Net irradiance (W m-2), the external source of energy flux
cp = Specific heat capacity of air (J kg-1 K-1)
ρa = dry air density (kg m-3)
δe = vapor pressure deficit, or specific humidity (Pa)
ga = Hydraulic conductivity of air, atmospheric conductance (m s-1)
gs = Conductivity of stoma, surface conductance (m s-1)
γ = Psychrometric constant (γ ≈ 66 Pa K-1)

Potential evapotranspiration is calcuçtaed made in module Basin. However, not all of the potential water that can be evaporated or transpirated will be in fact removed from the soil. The water that will really leave the soil through these processes is calculated in the Module Porous Media.

Other Features

Outputs

References

Data File

Keywords

Sample