Carryover of Commonwealth Water - NSW Murray and Murrumbidgee
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.
For example, in the NSW Murray the carryover limit on all general security entitlements is 50 per cent of these general security entitlements and in the Murrumbidgee catchment it is 30 per cent. Water in excess of these limits is reallocated to all users in the subsequent year. In addition, carryover affects how much additional water can accrue in an account in a future year as no user can have more than 110 per cent in their NSW Murray general security accounts (including carryover) or 100 per cent in their Murrumbidgee general security accounts. If a user's account is at the account limit then water that would otherwise have accrued would be foregone and allocated to other users. The carryover limit and account limit is illustrated below.
Figure 1 depicts how water accounts operate in the NSW Murray and Murrumbidgee
Commonwealth carryover in the NSW Murray and Murrumbidgee catchments
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 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 19 gigalitres in the NSW Murray. This was 1.6 per cent of the water that was carried over by all water users. In the Murrumbidgee catchment, the Commonwealth did not carry over any water into 2011-12 although other users carried over 600 gigalitres in total.
There will be higher volumes of carryover of environmental water into 2012-13. This is consistent with the expected approach of other users who have used less than the available water this year due to cooler than normal temperatures during 2011-12 and high rainfall towards the end of the irrigation season.
Impacts of Commonwealth carryover on other water users
If as expected the Commonwealth was to carryover about 25 gigalitres in the NSW Murray into 2012-13 then this would take up less than 0.4 percent of the storage capacity in Dartmouth and Hume Dams. If as expected the Commonwealth carried over about 42 gigalitres in the Murrumbidgee catchment then this would comprise 1.5 per cent of the storage capacity in this catchment.
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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