Underground infiltration formula (Water Overlay)
Underground infiltration (from the unsaturated zone to the saturated zone) is calculated per cell.
First the height of the unsaturated zone is calculated.
- Hunsat = Hsurface - WLunderground
Then the ratio of water amount to unsaturated height is calculated.
- S = Wunsat/Hunsat
Then calculate the distance of the unsaturated zone which can infiltrate.
- Cinf = min( Hunsat , Δt * Iund )
Finally, calculate the actual amount of water infiltrating.
- Δw = Cinf * S
- Δw = The underground infiltration which takes place.
- Δt = Computational timestep.
- Hunsat = The height of the unsaturated zone.
- S = Ratio of water to height in the unsaturated zone.
- Cinf = The height in the unsaturated zone which can be subject to infiltration to the saturated zone.
- Wunset = The amount of water in the unsaturated zone. The height of the water column if the equivalent amount of water was placed on the surface.
- WLunderground = The groundwater level, relative to datum.
- Hsurface = The terrain height in the cell, relative to datum.
- Iund = The GROUND_INFILTRATION_MD of the underground terrain type.
The following topics are related to this formula.
- Groundwater level formula
- Surface infiltration formula
- Underground model
- Infiltration model
- Substance flow model