Melbourne: Future outlook
Future prospects
This section looks forward 12 months and considers what water assets, claims, and commitments might affect the region's water resources.
Table N34 shows that there is a surplus of available water assets over water liabilities and future water commitments that are expected to be settled within 12 months of the reporting date.
| Volume ML | |
| Total water assets as at 30 June 2015 | 1,354,987 |
| less water assets not available to be accessed, taken or delivered within 12 months of the reporting date: | |
| dead storage1 | 21,534 |
| less total water liabilities as at 30 June 2015 | 5,952 |
| Subtotal | 1,327,501 |
| less future commitments expected to be settled within 12 months of the reporting date: | |
| expected diversion of allocated surface water to users (irrigation scheme)2 | 9,122 |
| expected surface water transfer under inter-region agreement3 | 3,206 |
| expected extraction of allocated groundwater to users4 | 15,237 |
| expected delivery to urban water system users5 | 394,700 |
| Surplus/Deficit of available water assets over water liabilities and future commitments expected to be settled within 12 months of the reporting date | 905,236 |
| add Future rights expected to be realised within 12 months of the reporting date: | |
| expected delivery of water under inter-region agreement6 | 66,690 |
| Surplus/Deficit of available water assets, expected future inflows and future water rights over water liabilities and future water commitments within 12 months of the reporting date | 971,926 |
1Dead storage volume for surface water storages
2Five-year average volume from 2010–11 to 2014–15: surface water diversions for individual users
3Five-year average volume from 2010–11 to 2014–15: surface water transfers made under inter-region commitment
4Five-year average volume from 2010–11 to 2014–15: groundwater extractions for individual users
5Five-year average volume from 2010–11 to 2014–15: surface water diverted to the urban water system
6Five-year average volume from 2010–11 to 2014–15: water delivered from outside the region
The volumes reported for future water rights and future water commitments are indicative only. The volumes presented in Table N34 were estimated from the average diversions and extractions in the previous five years. The actual volume of water delivered under these future water rights and future water commitments will depend on climatic conditions and demand.
Above average rainfall was experienced in the Melbourne region in both 2010–11 and 2011–12, increasing water availability and corresponding to a reduction in demand on water resources. These wetter conditions also enabled surface water storage levels to recover considerably. Consideration of diversions and extractions from these two years is likely to result in an underestimate of expected diversions and extractions for an average rainfall year.
Rainfall for the 2014–15 period was below the long-term average. Therefore the commitments stated in Table N33 are likely to be slightly underestimated and the surplus after the commitments is likely to be a slight overestimate of available water assets.
Although it was not possible to quantify future inflows, it is expected that with current storage levels and available inter-region sources, even below average inflows will meet the demands of future water commitments. The Victorian Desalination Plant at Wonthaggi is another source for future urban water supply when required.
Contingent water assets and contingent water liabilities
Contingent water assets
Sustainable yields have been estimated for all groundwater resources within Victoria, in the context of the permissible consumptive volumes (PCV). These were determined by the Department of Environment, Land, Water and Planning and represent the long-term average annual volume permitted to be extracted from aquifers within the Melbourne region. The limits are set to ensure groundwater is maintained at a sustainable level and are sufficient to maintain groundwater dependent ecosystems within the region.
The methods used to determine sustainable yields varied across the State according to the characteristics of the aquifers being investigated, and in many cases the full volume of the aquifer cannot be accurately quantified.
Water resource managers within the Melbourne region must adhere to the PCV extraction limitations for groundwater resources in the Melbourne region. The combined volume of the PCV has been recognised as a water asset in the National Water Account 2015. The volume of water that is beyond this extraction limit is considered a contingent water asset in the Melbourne region; however, there is currently not enough information available regarding the aquifers in the region to allow for a volumetric estimate.
Contingent water liabilities
There are no contingent water liabilities in the Melbourne region.