Drainage (Water Overlay)

Drainages provide connections between the saturated ground layer and nearby waterways, draining groundwater to levels which are optimal for agriculture. Drainage can be passive, where water drains based on water head differences, or active, where the water is pumped from the drain to the nearby waterway.

A drainage is an area-based building.

Icon	Key	Unit	Range	Description	Default value
	DRAINAGE_Q	m3 per second		The maximum pump flow capacity, defined in cubic meters per second.	1
	DRAINAGE_DATUM	datum	-10000 to 10000	The datum height (int meters) of the drainage.	-10000
	DRAINAGE_ACTIVE	boolean	0 or 1	Whether the drainage is actively pumped.	False
	DRAINAGE_OVERFLOW_THRESHOLD	m + datum	-10000 to 10000	The threshold of the water end-point of the drainage.	n/a

Notes

• A drainage should have a part that overlaps with land and a part that overlaps with water. These should be two separate polygons. Neither polygon should overlap with the edge of the waterway.

There are three use cases that can be modeled using a drainage:

Passive Drainage

A passive drainage lets water flow from the drainage pipes into the waterway when it has a lower level. In case of a higher water level in the waterway the water flow from the waterway into the drainage pipes. A passive drain must always have a positive Drainage Q.

• Note: when the waterway level is higher then the Drainage datum (Water Overlay) flow into the pipes is blocked.

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• 

Active Drainage Negative Q

An active drainage with a negative Drainage Q can pump water from from the waterway (with a lower level) up into the drainage pipes.

The pump will keep pumping until:

• The level in the waterway drops to the Drainage overflow threshold.
• The the groundwater reaches: Drainage datum.

• 

Active Drainage Positive Q

An active drainage with a positive Drainage Q can pump water from the drainage pipes up into a waterway (with a higher level).

The pump will keep pumping until:

• The level in waterway reaches the Drainage overflow threshold.
• The the groundwater drops to: Drainage datum.

• 

How-to's

• How to model drainage (Water Overlay)

See also

• Drainage formula (Water Overlay)
• Ground model (Water Overlay)#Drainage

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Water Module

Water Module

Tutorials

Overview

Theory

Benchmarks

Group

Hydraulic structures

Inlet

Inlet q • Inlet area • Inlet capacity •  Lower threshold •  Upper threshold • Inlet underground

Pump

Pump q •  Lower threshold •  Upper threshold • Pump angle • Pump capacity • Pump area

Culvert

Culvert diameter • Culvert rectangular height • Culvert threshold • Culvert n

Weir

Weir height • Weir width • Weir angle • Weir coefficient • Weir target level

Sewer overflow

Sewer overflow • Sewer overflow speed

Drainage

Drainage q • Drainage datum • Drainage active • Drainage overflow threshold

Output

Object flow output • Object height output • Object datum output a • Object datum output b • Object width output

Related

Building attributes • Hydrological features •  Terrain attributes • Model attributes • Results • Simulation data