Ground evaporation formula (Water Overlay)

Underground evaporation is calculated per cell.

For all underground evaporation calculation, the ground water depth at time t is used.

$d_{gw,t}=b_{s}-w_{g,t}$

Feddes oxygen stress factor:

$f_{o}={\begin{cases}1.0&{\text{if }}d_{gw,t}{\text{ is }}\geq d_{r,3}\\{\frac {d_{gw,t}-d_{r,4}}{d_{r,3}-d_{r,4}}}&{\text{if }}d_{gw,t}{\text{ is }}\geq d_{r,4}\\0.0&{\text{otherwise}}\end{cases}}$

Feddes saturated zone root update factor:

$f_{s}={\begin{cases}0.0&{\text{if }}d_{gw,t}{\text{ is }}>=d_{r,1}\\1.0-{\frac {d_{gw,t}-d_{r,2}}{d_{r,1}-d_{r,2}}}&{\text{if }}d_{gw,t}{\text{ is }}>=d_{r,2}\\1.0&{\text{otherwise}}\end{cases}}$

Max potential evaporation:

$E_{max}=f_{t}\cdot E_{w}\cdot f_{o}$

Evaporation unsaturated:

Failed to parse (unknown function "\begin{cases}"): {\displaystyle E_{u} = \begin{cases} 0.0 & \text{if } d_{us} \text{ is } <= 0.0} \\ min(E_{max}, h_u \cdot \frac{d_{r,1}}{d_{gw,t}})& \text{otherwise} \\ \end{cases} }

Evaporation saturated:

$h_{s}=w_{g,t}-(b_{s}-d_{gb})$

$h_{r}=max(0.0,w_{g,t}-(b_{s}-d_{r,1}))$

$E_{sp}=(E_{max}-E_{u})\cdot f_{s}$

$E_{s}=max(0.0,min(E_{sp},h_{s}\cdot f_{gw},h_{r}\cdot f_{gw}$

Evaporation total is the sum of evaporation in the saturated and unsaturated zone:

$E=E_{u}+E_{s}$

where

b_{s}

is the datum height of the surface.

w_{g}

is the underground water level.

d

is the column height of the unsaturated zone.

f_{t}

is the transpiration factor of the buildings (plants) on the surface, or the surface terrain's

[Terrain_water_evaporation_factor_(Water_Overlay)|transpiration factor]] if none present.

E_{w,t}

is the evaporation rate of the weather at time t

f_{0}

is the feddes oxygen stress factor, calculated using the 3rd and 4th root depths and the feddes trapezium interpolation model and the ground water depth.

Ground evaporation formula (Water Overlay)

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Ground evaporation formula (Water Overlay)

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