Melbourne
5.2 Surface water allocation remaining – urban water system
Supporting information
The volume presented in the water accounting statements (588,618 ML) represents the total volume of water that Melbourne retail and regional water authorities are entitled to within the Melbourne region.
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 which 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.
| Entitlement holder | Source – bulk entitlement | 30 June 2011 (ML) | 30 June 2012 (ML) | |
| City West Water South East Water Yarra Valley Water |
Yarra River1 | 528,009 | 535,307 | |
| City West Water South East Water Yarra Valley Water |
Tarago and Bunyip rivers2 | 21,000 | 19,434 | |
| Western Water | Melbourne Headworks system3 | 0 | 0 | |
| Western Water | Maribyrnong catchment | Gisborne—Baringo Creek | 32 | 20 |
| Lancefield | 46 | 46 | ||
| Macedon and Mount Macedon | 461 | 461 | ||
| Maribyrnong | 14,360 | 15,739 | ||
| Riddells Creek | 77 | 71 | ||
| Romsey | 297 | 297 | ||
| Subtotal Maribyrnong catchment | 15,273 | 16,634 | ||
| Western Water | Werribee catchment | Myrniong4 | 0 | 0 |
| Werribee system | 18,163 | 17,243 | ||
| Subtotal Werribee catchment | 18,163 | 17,243 | ||
| Total | 582,445 | 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 2011–12 year was derived from the opening storage volumes, inflows, diversions and outflows or losses from the reservoirs. These calculations are presented in the following tables for those entitlements which include a share of storage.
| Volume (ML) | ||
| Opening balance (30 June 2011) | 588,445 | |
| add | 21.2 Surface water allocation announcement – urban water system | 425,527 |
| less | 17.12 Entitled diversion of allocated surface water to urban water system | 374,198 |
| less | 13.2 Adjustment and forfeiture of surface water allocation – urban water system | 45,156 |
| Closing balance (30 June 2012) | 588,618 |
Comparative year
In the 2011 Account, it was reported that the bulk entitlements held by Melbourne's retail water authorities did not allow carryover of entitlements as no formal allocation announcements were made. Although this is correct, this does not accurately reflect the nature of the bulk entitlements operating in the Melbourne region.
In the 2012 Account, the volume of surface water allocation remaining – urban water system was reported as the retail and regional water authorities' share of storage in major reservoirs located throughout the region. This represents a significant change compared to the 2011 Account, but provides improved and more accurate information for users of the 2012 Account and ensures consistency in the approach used to report on other claims to water (refer to line item 1.5 inter–region claim on surface water).
Consequently, the volume has been restated from 0 ML (as published in the 2011 Account) to 582,445 ML.