National Water Account 2017

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Key findings

Climate and water

Water Accounting Statements

Supporting information

Region description

Reference information

Melbourne: Statement details

Water assets

• Water asset volumes in the region at 30 June 2017 were 1,271,205 ML, almost 95% of which are surface water assets.
• More than half of the surface water assets are inter-region claims, which is the portion of water in the Thomson Reservoir and Lake Eildon set aside for water supply to the Melbourne region.

Storages

Figure S1 Total storage volume in the region at 30 June 2017 compared with the previous seven years 

• Storage volumes increased from 60% full at 30 June 2016 to 64% full at 30 June 2017.
• Above-average rainfall during winter and spring 2016 contributed to storage volumes exceeding 75% full in mid-November 2016.
• The increase in the region's surface water availability, as well as water supply from the Wonthaggi Desalination Plant for the first time, meant inter-region transfer from Thomson Reservoir was less than last year (see below).

Figure S2 Percentage-full volume on 30 June 2017 for each storage

• Pykes Creek and Melton reservoirs, which are used primarily for irrigation supply, reached 100% full for the first time in four years due to above-average rainfall in winter and spring 2016.
• More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.

Inter-region claims

• Inter-region claims refer to the volume of allocation remaining on licence entitlements from inter-region sources at the end of the 2016–17 year.

• Water supply from the Thomson Reservoir is classified as an inter-region transfer and is the primary source of water supply outside the region boundary.
• 93% of the total claim at 30 June 2017 is related to water delivery from the Thomson Reservoir.
• A more detailed description of inter-region water sources for the Melbourne region is given in the Region Description.

Figure S3 Inter-region claim from Thomson Reservoir at 30 June 2017 compared with the previous seven years 

• The inter-region claim from the Thomson Reservoir at 30 June 2017 was 8% higher than the previous year due to increased inflow to the reservoir and decreased transfers to the region during the year.

Groundwater assets

Figure S4 Permissible consumptive volumes: water table and underlying aquifers in the Melbourne region

• The groundwater asset volume for the region represents permissible consumptive volumes for water table aquifers and underlying aquifers in groundwater management and water supply protection areas.
• The groundwater asset volume remained constant during the year as there was no change in licences or the permissible consumptive volume.

Urban water system assets

• Urban water system asset volume at 30 June 2017 was 29,026 ML, similar to previous years.
• The asset volume includes water held in lagoons at wastewater treatment plants.

Water liabilities

• Water liabilities in the Melbourne region refer to the volume of allocation remaining on licence entitlements at the end of the 2016–17 year. 

• As there are no carryover provisions for groundwater supply licences in the region, the portion of water allocation that has not been abstracted at the end of a water year is forfeited and the allocation remaining at the end of the year was 0 ML.
• A more detailed description of water allocations and associated water rights in the Melbourne region is given in the Water rights note.

Water asset increases

• Total water asset increases for the region was 2,800,828 ML.
• The key item contributing to water asset increases for the region was runoff, which made up more than 60% of the total water asset increases. Runoff was 97% higher than the previous year, which reflects the well above-average rainfall conditions during winter and spring 2016, particularly over western parts of the region (see Climate and water).
• Recharge from the landscape represented more than 75% of the total groundwater increases and was also higher than the previous year.

Water asset decreases

• Total water asset decreases for the region was 2,377,812 ML.
• The key item contributing to water asset decreases for the region was outflow, which made up 50% of the total water asset decreases. The well above-average rainfall conditions during winter and spring, particularly over western parts of the region (see Climate and water), contributed to a greater than 70% increase in river outflow to sea from the previous year.
• Supply system delivery: urban users, which changes little from year to year, accounted more than half the total urban water system decreases.

Water flows

• Total water inflows to the region was 2,702,031 ML, which differs from the volume of Water asset increases (2,800,828 ML). Total water inflows includes the volume of water delivered under inter-region claims; total water asset increases includes the annual allocation for inter-region claims.
• Total water outflows from the region was 2,368,051 ML, which differs from the volume of Water asset decreases (2,377,812 ML). Total water outflows includes the flows corresponding to the accrual transactions—allocated diversions and allocated extractions. Total water asset decreases includes the forfeiture of inter-region claims.
• A detailed description on all the water flows associated with the surface water and groundwater stores, as well as the urban system, is provided in the Water stores note.

Unaccounted-for difference

• The unaccounted–for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements.

• The unaccounted-for difference value is primarily attributed to uncertainties associated with the runoff and river outflow estimates and unaccounted groundwater information including discharge to landscape and rivers (see Methods).