South East Queensland

The volume recognised in the water accounting statement (465 ML) represents the volume of water held in the pipes of LinkWater’s bulk transmission network.

Data source

LinkWater Geographic Information System (GIS) database.

Data provider

SEQ Water Grid Manager.

Method

The potable water supply system consists of large-diameter bulk transmission mains that transport potable water from the water treatment plant to key water tanks and distribution points within the urban potable water supply system. Smaller distribution mains distribute water to end users from these tanks and distribution points.

The total volume of the LinkWater bulk transmission network across the entire South East Queensland (SEQ) Water Grid was calculated.

The cross-sectional area was calculated based on the diameter of each pipe within LinkWater’s GIS. This was then multiplied by the total length of pipe of this diameter to give the total volume for each diameter. The volumes of all pipes of various diameters were then summed.

Uncertainty

Derived from GIS data. Ungraded.

Approximations, assumptions, caveats and limitations

• The potable water supply system storage was calculated only for the LinkWater SEQ Water Grid. GIS data were not readily available for the remaining water service providers’ distribution systems. No volume was calculated for non-LinkWater distribution systems or tanks because information on storage capacity could not be obtained, and hence this could not be quantified accurately. The value reported for this line item is an underestimate of the total urban potable water supply system storage.
• The potable water supply system storage could only be calculated for the LinkWater SEQ Water Grid as a whole. This system extends outside the National Water Account 2010 South East Queensland (SEQ) region in the north and includes part of the Mary water resource plan (WRP) area (Sunshine Coast).
• The diameter code rounds off the diameter of the pipe to provide an even number to work with, rather than using the exact internal diameter. For example, a diameter 250 has a 250-mm nominal diameter but the internal diameter may vary, depending on the pipe material and pressure rating – for example, polyethylene DN250 may have an internal diameter of around 230 mm, and a ductile iron DN250 may have an internal diameter of around 270 mm. The use of diameter rather than internal diameter to determine volume results in some inaccuracies in the estimate. It is expected that this is of the order of 5% for individual pipe segments.
• Due to the ‘live’ nature of GIS, the storage volume was only able to be calculated at the time of request, resulting in identical volume estimates for the start and end of the reporting period. It is expected that only a minor change in volume occurred between these dates as limited additional infrastructure was commissioned during the year.