Groundwater Prequel (Water Overlay)

Groundwater levels in the Water model can be initialized using a Overlay Prequel.

Groundwater is only used when the GROUND WATER attribute of the Water Overlay is set to complete, meaning the ground model is vertically and horizontally fully active.

Values in the groundwater Prequel can represent either:

• the datum height of the ground water level.
• the water depth, as the initial distance between the surface and the watertable. A greater value in the GeoTIFF will result in a lower watertable.

When a groundwater Prequel is not configured for the Water Overlay, the watertable is initialized using the WATER_LEVEL attribute of the water area instead (or the Surface level prequel (Water Overlay), if so configured). For locations without water areas, the water table is set to one meter below the surface.

The following Prequels are possible:

Bottom flow prequel (Water Overlay)

Name	Prequel	Underlying data	Unit	Range	No data	Description
Groundwater datum	GROUND_WATER_DATUM	Water Prequel	m datum	-10000 10000	Clamped to range	Used for initializing the ground water level on this datum.
Groundwater depth	GROUND_WATER_DEPTH	Water Prequel	m	0 10000	Clamped to range	Used for initializing the ground water level to these depths.
Unsaturated fraction	UNSATURATED_FRACTION	Water Prequel		0 to 1	Clamped to range	Used for initializing the saturation of the unsaturated zone in the underground.
Bottom Pressure	BOTTOM_PRESSURE	Water Prequel	m datum	-1000000 to 1000000	Clamped to range	A grid of values containing the head of the ground water pressure caused by ground water in higher regions outside the project area.

Default data

For the Netherlands, a number of groundwater GeoTIFFs are provided by default, based on data provided by The Netherlands Hydrological Instrumentarium:

• NL_GHG_kk-nhi (Average highest waterdepth)
• NL_GLG_kk-nhi (Average lowest waterdepth)
• NL_GVG_kk-nhi (Average spring waterdepth)

It is important to emphasize that when using these GeoTIFFs, they should be configured as water depth (relative to terrain) rather than water height (relative to datum).

How-to's

• How to use a default groundwater GeoTIFF (Water Overlay)
• How to upload and use a groundwater GeoTIFF (Water Overlay)

See also

• Water area (Water Overlay)
• Ground model (Water Overlay)
• Ground watertable result type (Water Overlay)

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Water Module

Water Module

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Simulation data

Weather

Rain m • Evaporation m

Prequels

Bottom distance • Bottom pressure • Bottom resistance • Ground conductivity • Groundwater datum • Groundwater depth • Manning • Max infiltration • Microrelief • Sewer level • Surface level • Surface u • Surface v • Terrain elevation • Unsaturated fraction

Elevation

Elevation model

Related

Building attributes • Hydrological features • Hydraulic structures •  Terrain attributes • Model attributes • Prequels • Results