Underground evaporation formula (Water Overlay)

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Underground evaporation is calculated per cell.

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

Feddes oxygen stress factor:

Feddes saturated zone root update factor:

Max potential evaporation:

Evaporation unsaturated:

Potential evaporation saturated:

Evaporation saturated zone:

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

where

is the datum height of the surface.
is the ground water level (datum height) at time t.
is the depth of the ground water level, which is equal to the column height of the unsaturated zone at time t.
is the transpiration factor of the buildings (plants) on the surface, or the surface terrain's transpiration factor if none present.
is the evaporation rate of the weather at time t
is the calculated feddes oxygen stress factor, calculated using the 3rd and 4th root depths and the feddes trapezium interpolation model and the ground water depth.
is the calculated feddes saturated zone root update factor, calculated using the 1st and 2nd root depths and the feddes trapezium interpolation model and the ground water depth.
is the nth root depth value.
is the amount of water in the unsaturated zone.
is the potential max evaporation
is the evaporation in the unsaturated zone
is the potential evaporation in the saturated zone
is the evaporation in the saturated zone
is the total evaporation from the underground.
is the ground bottom distance
is the column height of the saturated zone covered by the roots

Related

The following topics are related to this formula.

Formulas
Groundwater level formula
Models
Underground model
Evaporation model