Surface infiltration formula (Water Overlay)

Surface infiltration is calculated per cell. First, the infiltration capacities are calculated:

${\overline{I}}_{top}=\{\begin{array}{ll}{\overline{I}}_{con},& \text{if constructions are present on top of the surface}\\ {\overline{I}}_{terrain},& \text{otherwise}\\ \end{array}$

${\overline{I}}_{surface}=min({\overline{I}}_{ground},{\overline{I}}_{top})$

Then the actual infiltration:

$\mathrm{\Delta }{w}_t=min(h_t,{\overline{I}}_{surface}\cdot \mathrm{\Delta }t\cdot f_{i,t})$

Where:

${\overline{I}}_{con}$ = The average infiltration capacity based on constructions on top of the surface, based on GROUND_INFILTRATION_MD defined in either the building or function.

${\overline{I}}_{terrain}$ = The average infiltration capacity based on the surface terrain, defined by GROUND_INFILTRATION_MD. This value should be interpreted as the vertical conductivity (Kv) of the sub-soil.

${\overline{I}}_{top}$ = The average infiltration capacity on top of the surface.

${\overline{I}}_{ground}$ = The average infiltration capacity below the surface.

${\overline{I}}_{surface}$ = The infiltration capacity from surface to the unsaturated zone.

$\mathrm{\Delta }{w}_t$ = The surface infiltration which takes place at time $t$.

$h_t$ = The amount of water on the surface at time $t$. Also known as the water column.

$\mathrm{\Delta }t$ = Computational timestep.

$f_{i,t}$ = The interpolated infiltration factor at time $t$. Configured using INFILTRATION_FACTOR_S.

Related

The following topics are related to this formula.

Formulas

Surface water level formula

Groundwater level formula

Underground infiltration formula

Models

Surface model

Underground model

Infiltration model

Tracer flow model

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