South East Queensland

Contingent water assets

Desalinated water

The Gold Coast desalination plant officially became part of the SEQ Water Grid when handed over to WaterSecure on 30 September 2010. Desalinated water from the Gold Coast desalination plant, in Tugun, is blended with other water supplies before it joins the SEQ Water Grid. The SEQ Water Grid Manager works closely with all entities to determine the demand on the desalination plant through a grid instructions process. Under normal operating conditions, it was planned for the desalination plant to operate at a minimum of 33% capacity (44 ML/day) in accordance with rules outlined in the SEQ System Operating Plan V3.1. With the South East Queensland (SEQ) region’s dams full or near full, the SEQ Water Grid has been operating in ‘hot stand-by’ mode to minimise operating costs since December 2010. Under this mode of operation, the plant will typically produce around 25 ML/day of water two days a week, with no production in between. This small amount of production is needed to keep the membranes wet and the water in the pipes fresh, while retaining the capacity to ramp up to produce 44 ML/day (33%), 88 ML/day (66%) or 133 ML/day (100%) within hours whenever required.

The plant may be called on if there are interruptions to supply in other parts of the SEQ Water Grid, as occurred in the January floods and in lighting strikes that temporarily knocked out the Mount Crosby water treatment plant. The plant will also cover production when other parts of the Water Grid are offline for routine maintenance.

The contingent water asset associated with the Gold Coast desalination plant is the difference between the maximum operating capacity (133 ML/day) and the minimum operating rate (22 ML/day) and equates to 111 ML/day.

Groundwater

The groundwater management area (GMA) of the Lockyer Valley located within the Moreton water resource plan (WRP) area was the only aquifer included as a store in the water accounting statements. The total volume of the Central Lockyer Valley aquifer was estimated by Queensland Department of Environment and Resource Management (DERM). Within the Benefitted Area of the Central Lockyer water supply scheme (WSS), a groundwater limit exists, which defines the entitled maximum volume that can be extracted from the Benefitted Area of the aquifer as 9,340 ML.

The Non-Benefitted Area extraction is a groundwater outflow rather than a groundwater asset. More details on this volume can be found in 16.4.2 Groundwater extractions – other lumped basic rights. The contingent groundwater asset includes a deduction for the Non-Benefitted Area extraction in lieu of an extraction limit, as an extraction limit was not available.

The volume within the aquifer which exceeds this extractable limit has been defined as a contingent water asset.

The estimated contingent groundwater asset for the Lockyer Valley GMA can be seen in the table below.

Contingent liabilities

Water for urban use

The SEQ Water Grid Manager holds the urban water entitlements for South East Queensland and is responsible for managing the SEQ Water Grid. During 2009–10 water was supplied by Seqwater and WaterSecure, bulk distribution undertaken by LinkWater and potable water retailed by individual councils with the SEQ region. On the 1 July 2010 administrative arrangements changed, with the council owned retail organisations of Queensland Urban Utilities, Allconnex Water and Unity Water being formed.

The SEQ Water Grid Manager maintains water within its system for the provision of water to the councils or council owned entities, but the actual delivery of water is determined by the customers through their demand (i.e. when a customer turns on a tap). There is a contingent liability to provide water to potable water customers. Based on 2009–10 usage, it is expected that this liability would be in the order of 215 GL/year.