Carryover of Commonwealth Water - Northern Victoria
Commonwealth Environmental Water
June 2012
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What is meant by carryover of water?
Carryover is provided for in regulated parts of the Murray- Darling Basin and allows water users to hold water in storages so that it is available in subsequent years. Carryover provides water users with greater flexibility to manage their own water availability across years.
How is carryover governed?
The States have created rules that apply to the carryover of water. The rules manage the impact that water users may have on other users through their carryover decisions.
Commonwealth Environmental Water operates under the same rules and pays the fees and charges associated with its water as all other water licence holders. The Commonwealth can carry over water in the same way as occurred when the water entitlements were managed for agricultural use. So:
- Carryover was previously available to the water entitlements now held by Commonwealth Environmental Water and its acquisition for environmental purposes does not affect the maximum carryover in dams.
- Commonwealth Environmental Water, like any other water holder, cannot fill up dams to the exclusion of other water users.
In northern Victoria, there are rules for 'spillable water accounts' in larger catchments (Murray, Goulburn, and Campaspe), and carryover limits in other catchments. Water up to the entitlement volume can be stored in allocation bank accounts. A spillable water account allows the storage of water over and above the entitlement volume but if the associated dam spills then water is deducted from these spillable water accounts first.
For example, in the Goulburn catchment, storage of volumes of water over and above the entitlement volume is secure in spillable water accounts as long as Eildon Dam does not spill. In contrast, in the Loddon and Broken catchments, the rules are different and the maximum carryover from one year to the next is limited to 50 per cent of the entitlement volume.
Spillable water accounts
In the Murray, Goulburn and Campaspe catchments, spill rules operate as if carryover occupies 'air space' within dams, and the account size is effectively not limited provided that the dam has not spilled. At the start of each year the volume of allocation carried over in addition to entitlement volumes is assigned to a 'spillable water account' and this water is not available for use or trade until a declaration of low risk of spill is made by the Northern Victorian Resource Manager. In making this declaration, the volume of water in storage and possible future inflows under prevailing climatic and catchment conditions are taken into account. If there is a spill, water is forfeited from spillable water accounts on a proportional basis. An illustration of this follows.
Figure 1 depicts how spillable water accounts operate in Northern Victoria
Further information regarding spill rules is available at the Victoria Water Register website.
Carryover limits
Carryover limits apply in a number of the smaller catchments in northern Victoria. In the Ovens catchment, no carryover is permitted. In the Broken and Loddon catchments the carryover limit is 50 per cent of the entitlement volume and the account limit is 100 per cent. Therefore, if a Victorian user carries over 40 per cent of their entitlement volume in the Broken or Loddon catchments, then the allocations in the next year that could be received by that user would be a maximum of 60 per cent. The water that otherwise would have been received by that user would be re-allocated to other users.
Commonwealth carryover in northern Victoria
In 2011-12 many environmental requirements were met through natural high river flows and flooding. In very wet years, it makes sense to carryover some environmental water so that it is available in future years when it may be of more benefit. Commonwealth Environmental Water has carried water over into 2011-12, and will carry over water into 2012-13, in many northern Victorian catchments because use in future years is likely to produce more environmental benefit than further use in years with very high river flows.
Commonwealth Environmental Water carried over into 2011-12 a total of 112 gigalitres in northern Victorian catchments. This was less than 4.5 per cent of the water that was carried over by all water users.
It is anticipated that there will be approximately 200 gigalitres of carryover of Commonwealth environmental water in Victorian accounts into 2012-13, 175 gigalitres of which would be in the Victorian Murray. Other users are also expected to have relatively high carryover volumes due to cooler than normal temperatures and high rainfall towards the end of the irrigation season.
Impacts of Commonwealth carryover on other water users
Under Victorian rules, in wet years carryover in spillable water accounts will be the first to spill to ensure there is minimal impact on water available to others. If as expected the Commonwealth was to carryover 175 gigalitres in Victorian Murray into 2012-13 then this would take up 2.5 percent of the storage capacity in Dartmouth and Hume reservoirs. All of this water would be in allocation bank accounts (as the volume of water stored is less than the volume of entitlement that is in excess of 220 gigalitres) rather than spillable water accounts.
Commonwealth Environmental Water will report each year on the volume of water that has been carried over on each entitlement type held in the Basin. Over the longer term it is expected that the percentage of Commonwealth environmental water that is carried over will be similar to other water users - although like all water users it will vary from year to year.
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