Melbourne

The volume recognised in the water accounting statements (287 ML) represents environmental water allocations made for the Bunyip catchment during 2009–10.

An environmental water allocation is the volume of water that is available to be diverted at the discretion of the environmental entitlement holder to meet priority environmental objectives.

The environmental water allocation made during 2009–10 refers to the volume of water that was returned to the Bunyip catchment following a period of zero allocation under the temporary qualification of rights in the Melbourne Water supply system.

The table below shows the breakdown of announcements made for the Bunyip catchment during 2009–10.

Data source

Melbourne Water: Waterworks database; supervisory control and data acquisition (SCADA) database.

Data provider

Melbourne Water.

Method

Environmental share of storage refers to the volume of environmental water held in the Bunyip catchment storages for discretionary diversion. For the Bunyip catchment, the environmental store was accrued as an ‘inflow’ rather than as an ‘allocation’. Inflow was calculated using a mass-balance approach. That is, inflow was determined as outflow minus change in storage.

For the Bunyip catchment, water allocated to the environmental share of storage in the Tarago Reservoir is limited to 3,000 ML, and was calculated as 10.3% of the inflow to the Tarago Reservoir minus water diverted from Tarago Reservoir to meet environmental passing flows. In addition, according to the Tarago and Bunyip rivers environmental entitlement, this arrangement becomes effective when Melbourne customers are no longer subject to a level of water restrictions equal to or more severe than Stage 3A. On 02 April 2010 the Victorian Government relaxed Melbourne restrictions to Stage 3 (from Stage 3A), thus allowing inflows to the Tarago Reservoir to contribute to the environmental share of storage.

Uncertainty

Not applicable.

Approximations, assumptions, caveats/limitations

Nil.