Terrain water storage percentage (Water Overlay)

Infiltration and storage

Based on the properties of the terrain, water may infiltrate into the ground layers. Two ground layers are distinguished; the underground unsaturated zone and underground saturated zone.

The speed at which water can infiltrate from the surface to the underground unsaturated zone is dependent on both the GROUND_INFILTRATION_MD of the surface terrain, as well as the GROUND_INFILTRATION_MD of any construction in that location, if present. Of the infiltration values of the construction and the surface terrain, the lowest value is used. If either has an infiltration value of 0, water cannot infiltrate into the underground unsaturated zone.

The maximum amount of water which can be stored in the saturated zone is based on the WATER_STORAGE_PERCENTAGE of the underground terrain.

Underground flow, also known as horizontal infiltration, is also dependent on the infiltration properties of the underground, unless an aquifer exists the same location.

Notes

Contrary to its name, the WATER_STORAGE_PERCENTAGE should always be a fraction.
The groundwater level reduction is related inversely to the WATER_STORAGE_PERCENTAGE, as the contribution of a given volume of water to the groundwater level increases when the capacity for water storage in the underground layer decreases.