Melbourne
5.2 Surface water allocation remaining – urban water system

The line item value for the 2012-13 year is (495,189 ML). The value represents the total volume of water that Melbourne's retail and regional water authorities are entitled to within the Melbourne region.

Melbourne Water Annual Report (2013); Western Water Annual Report (2013)

Melbourne Water; Western Water

Within the Melbourne region several bulk entitlements are in place which govern the source, volume, and arrangements under which the retail water authorities can divert surface water for urban water supply. Each bulk entitlement specifies an annual (or rolling annual average) volumetric upper limit; however, formal annual allocations are not made. As allocations are not made, carry-over of allocations is not possible.

Under the majority of the bulk entitlements, however, the retail and regional water authorities are entitled to a share of storage. This fluctuates annually depending on inflows to (rainfall, runoff) and outflows (evaporation, other losses) from the storages. This share of storage, at the start and end of the year, is recognised at this line item, as shown in the following table.

Melbourne retail and regional water authorities' share of storage at the start and end of the 2012–13 year

Entitlement holder	Source–bulk entitlement		30 June 2013 (ML)	30 June 2012 (ML)
City West Water	Yarra River1		428,906	535,307
South East Water
Yarra Valley Water
City West Water	Tarago and Bunyip rivers2		29,547	19,434
South East Water
Yarra Valley Water
Western Water	Melbourne Headworks system3		0	0
Western Water	Maribyrnong catchment	Gisborne—Baringo Creek	15	20
		Lancefield	9	46
		Macedon and Mount Macedon	360	461
		Maribyrnong	18,596	15,739
		Riddells Creek	43	71
		Romsey	72	297
Subtotal Maribyrnong catchment			19,095	16,634
Western Water	Werribee catchment	Myrniong4	0	0
		Werribee system	17,641	17,243
Subtotal Werribee catchment			17,641	17,243
Total			495,189	588,618

^1–2 The storage volume data does not include dead storage and was provided by Melbourne Water. It refers to a share of storage capacity only, and therefore does not correspond to the storage data reported at line item 1.1 Storages.

^3–4 These entitlements do not include a share of storage capacity; therefore the volume reported as claim remaining is zero.

Detailed information on the bulk entitlements used for urban water supply in the Melbourne region, including annual volumetric entitlement limits and share of storage, is provided in line item 32.3.

The Melbourne retail and regional water authorities' share of storage at the end of the 2012–13 year was derived from the opening storage volumes, inflows, diversions, and outflows or losses from the storages. These calculations are presented in the following tables for those entitlements which include a share of storage.

Calculation of the Melbourne retail water authorities' share of storage in the Melbourne region for the 2012–13 year

Account	Volume (ML)
Opening balance at 1 July 2012	588,618
11.18 Increase of urban claim on surface water	368,435
11.12 Entitled diversion of allocated surface water to urban water system	(408,812)
19.17 Adjustment and forfeiture of urban claim on surface water	(53,052)
Closing balance at 30 June 2013	495,189

Nil.

The uncertainty estimate was not quantified.