Australian Water Information Dictionary

Alphabetical list of items

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vadose zone

The areas below the ground where void spaces are filled with a mixture of water under pressure less than atmospheric which includes water held by capillarity and air (gases) under atmospheric pressure.

Source: Poehls DJ and Smith GJ 2009, Encyclopedic dictionary of hydrogeology, Elsevier Inc., 517 pp.

Synonym: unsaturated zone

This definition applies to:


A check of a developed stage-discharge relationship, including gaugings, survey data and other relevant metadata.

This definition applies to:

vapour pressure deficit

The difference between the amount of moisture in the air and how much moisture the air can hold when it is saturated.

Source: Water Regulations 2008 Schedule 3 Part 1

This definition applies to:

vector data

Data organised as geometry consisting of points, lines and polygons.

This definition applies to:


Line on which velocity measurements or depth measurements are made.

Source: AS 3778.1—2009 Clause 2.4. Reproduced with permission from SAI Global Ltd under Licence 1307-c151. This standard can be purchased online at

This definition applies to:


Clay soils that shrink and swell, and crack as the soil dries. Largest single area occurs in the arid and semi-arid interior of the continent.

Source: R F Isbell, 1996, The Australian Soil Classification, CSIRO Publishing, Melbourne.

This definition applies to:


The volume of water stored at a particular time and date. It excludes the dead storage volume and hence is the volume of water that can be accessed under normal circumstances without the installation of additional infrastructure. See the water storage diagram for more information.

Synonym: accessible storage volume

This definition applies to:

volume weighted average price (VWAP)

The average value (dollars per megalitre) of the water traded where each trade is weighted proportionally by the volume of water (in megalitre) involved in the sale. This provides a more accurate representation of the price (i.e. high volume trades generally attract a ‘bulk discount’).

This definition applies to:


GPS data string that provides the velocity relative to the ground, including direction and speed.

This definition applies to: