Infiltration model (Water Overlay): Difference between revisions

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[[File:Infiltration_model.png]]
[[File:Infiltration_model.png]]
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When water infiltrates from the surface, it infiltrates at a speed dictated by the surface terrain's [[Ground infiltration md (Terrain) (Water Overlay)|GROUND_INFILTRATION_MD]] attribute, the underground terrain's [[Ground infiltration md (Terrain) (Water Overlay)|GROUND_INFILTRATION_MD]] attribute, or (if present) by the construction's [[Ground infiltration md (Water Overlay)|GROUND_INFILTRATION_MD]], whichever value is lowest. The least porous material present will always serve as a bottleneck for the water to flow through, even if the other layers allow for a high rate of infiltration.
Surface water can infiltrate into the underground unsaturated layer. When it does, it infiltrates at a speed defined by the surface terrain's [[Ground infiltration md (Terrain) (Water Overlay)|GROUND_INFILTRATION_MD]] attribute, the underground terrain's [[Ground infiltration md (Terrain) (Water Overlay)|GROUND_INFILTRATION_MD]] attribute, or (if present) by the construction's [[Ground infiltration md (Water Overlay)|GROUND_INFILTRATION_MD]], whichever value is lowest. The least conductive layer will therefore be the bottleneck, even if the other layers allow better infiltration.


Surface water infiltrates into the underground unsaturated layer. Water in the unsaturated layer is assumed to be spread equally across the entire unsaturated volume. Water then flows from the unsaturated zone into the saturated zone at the speed dictated by the underground terrain's GROUND_INFILTRATION_MD. For a given timestep, the distance the water travels is determined. The amount of water that flows from the unsaturated zone to the saturated zone is equal to the amount of water in a section of the unsaturated zone the height of which is equal to that distance. After water has been added to the saturated zone, the groundwater level (and thus the height of the saturated zone) is redetermined. The water in the unsaturated zone is redistributed uniformly across the (remaining) unsaturated zone.
Water infiltrating into the unsaturated layer is assumed to be spread equally across the entire unsaturated column within the grid cell.  


Water stored in the underground saturated zone can flow horizontally from one underground cell to another, if the groundwater level relative to datum is higher than the neighboring cell's ground water level, relative to datum. The amount of water which can flow from one cell to another is dictated by the underground terrain's GROUND_INFILTRATION_MD.
Water can flow further down into the saturated zone at a speed defined by the underground terrain's GROUND_INFILTRATION_MD. For a given timestep and the infiltration speed, the distance the water can travel downwards is determined. This distance can be projected on this unsaturated zone as a subsection. The amount of water that flows from the unsaturated zone to the saturated zone is then equal to the amount of water in this subsection. After water has been added to the saturated zone, the groundwater level (and thus the height of the saturated zone) is redetermined. The water remaining in the unsaturated zone is redistributed uniformly across the (remaining) unsaturated zone.


===Exfiltration===
===Exfiltration===
Water stored in the underground saturated zone can also exfiltrate out of the underground and back onto the surface, if the groundwater level relative to datum exceeds the neighboring cell's surface water level relative to datum. The amount of water which can flow from the underground of one cell onto the surface of an adjacent cell is dictated by the underground terrain's GROUND_INFILTRATION_MD.
Water stored in the underground saturated zone can also exfiltrate out of the underground and back onto the surface, if the groundwater level relative to datum exceeds the neighboring cell's surface water level relative to datum. The amount of water which can flow from the underground of one cell onto the surface of an adjacent cell is dictated by the underground terrain's GROUND_INFILTRATION_MD.

Revision as of 16:12, 12 April 2019

The Water Module supports two types of infiltration; surface to unsaturated zone and unsaturated to saturated zone. Furthermore, exfiltration can also occur due to horizontal groundwater flow.

Infiltration

File:Infiltration model.png
Surface water can infiltrate into the underground unsaturated layer. When it does, it infiltrates at a speed defined by the surface terrain's GROUND_INFILTRATION_MD attribute, the underground terrain's GROUND_INFILTRATION_MD attribute, or (if present) by the construction's GROUND_INFILTRATION_MD, whichever value is lowest. The least conductive layer will therefore be the bottleneck, even if the other layers allow better infiltration.

Water infiltrating into the unsaturated layer is assumed to be spread equally across the entire unsaturated column within the grid cell.

Water can flow further down into the saturated zone at a speed defined by the underground terrain's GROUND_INFILTRATION_MD. For a given timestep and the infiltration speed, the distance the water can travel downwards is determined. This distance can be projected on this unsaturated zone as a subsection. The amount of water that flows from the unsaturated zone to the saturated zone is then equal to the amount of water in this subsection. After water has been added to the saturated zone, the groundwater level (and thus the height of the saturated zone) is redetermined. The water remaining in the unsaturated zone is redistributed uniformly across the (remaining) unsaturated zone.

Exfiltration

Water stored in the underground saturated zone can also exfiltrate out of the underground and back onto the surface, if the groundwater level relative to datum exceeds the neighboring cell's surface water level relative to datum. The amount of water which can flow from the underground of one cell onto the surface of an adjacent cell is dictated by the underground terrain's GROUND_INFILTRATION_MD.