Commonwealth Environmental Water Office banner

Carryover of Commonwealth environmental water from 2012-13 into 2013-14 - Northern NSW

Commonwealth Environmental Water Office, 2013

What is meant by carryover of water?

Carryover is provided for in regulated parts of the Murray-Darling Basin (the Basin) and allows water entitlement holders to hold water in storages so that it is available in subsequent years. Carryover therefore provides water entitlement holders 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 entitlement holders may have on other entitlement holders through their carryover decisions.

The Commonwealth environmental water holdings are a set of water entitlements and associated allocations. The Commonwealth Environmental Water Holder, supported by the Commonwealth Environmental Water Office, manages these water holdings under the same rules and pays the associated fees and charges as other entitlement holders do with respect to their holdings. The Commonwealth can carry over water in the same way as occurred when the water entitlements were managed for agricultural use. So:

  • carryover that was previously available to the water entitlements now held by the Commonwealth and its acquisition for environmental purposes does not affect the maximum carryover in dams overall or associated with these entitlements; and
  • the Commonwealth, like any other water holder, cannot fill up dams to the exclusion of other water entitlement holders.

Northern NSW catchments include the Lachlan, Macquarie, Namoi, and Gwydir catchments, and the NSW Border Rivers. In most of these catchments there are continuous accounting rules, and there are no carryover limits applied at the end of a water year. The exception is the Macquarie catchment where there is a carryover limit lower than the account limit, as discussed below. Also, in the Lachlan and Macquarie catchments, accounts are re-set following dam spills.

Continuous accounting

Continuous accounting occurs under water sharing plans1 in the Lachlan, lower Namoi, Gwydir and NSW Border Rivers. This arrangement is designed to provide for substantial carryover (100 to 200 per cent depending on the catchment) because inflows are more variable than in the south of the Basin. Typically there are high maximum account limits which enable high levels of carryover.

There are also annual use limits (100 to 125 per cent of entitlement depending on the catchment). If the balance in a water account has reached the account limit then new allocations are no longer credited to that account. The total allocations that an entitlement holder can receive, including the Commonwealth, are limited by the space in their account. An illustration of this process is provided in figure 1.

The chart depicts how continuous water accounting operates most catchments in Northern NSW.

Figure 1. How continuous water accounting operates in most catchments in northern NSW.

Carryover limit

In the Macquarie catchment there is a carryover limit of 100 per cent and an account limit of 200 per cent. If an entitlement holder held 150 per cent in their account at the end of the year then 50 per cent would be forfeited and may be re-allocated to others. These arrangements are similar to those applying to general security entitlements in the Murrumbidgee and NSW Murray where a carryover limit (of 30 per cent and 50 per cent respectively) applies. An illustration of how these rules are applied is provided in figure 2. These arrangements apply equally to all entitlement holders, including the Commonwealth, in proportion to entitlement held.

How the rules relating to carryover and account limits are applied in the Macquarie catchment in northern NSW.

Figure 1. How the rules relating to carryover and account limits are applied in the Macquarie catchment in northern NSW.

Re-setting rules

In some northern NSW catchments, water sharing plans provide for account or allocation "re-set" if a dam spill occurs. Under the water sharing plan for the Lachlan catchment, when Wyangala Dam spills, all general security access licence accounts are re-set to 136 per cent of entitlement irrespective of whether they held more or less water at the time of spill. Under the water sharing plan for the Macquarie, when Burrendong dam spills, all high and general security allocations are re-set to 100 per cent. These arrangements apply to the Commonwealth and all other entitlement holders.

Commonwealth carryover in northern NSW

In 2012-13 rainfall across the Basin was below average, and carryover was drawn upon in a number of catchments so that desired environmental outcomes could be achieved. The Commonwealth had lower carryover in all northern NSW catchments on 1 July 2013 than it held on 1 July 2012, despite entitlement holdings increasing in 2012-13 in most catchments. For example, in 2012-13:

  • in the Macquarie catchment, the carryover decreased from 94 GL to 23 GL due to watering of the Macquarie Marshes, preceded by a spill from Burrendong Dam; and
  • in the Lachlan catchment, the carryover decreased from 116 GL to 66 GL due to watering of the Booligal wetlands and lower Lachlan Swamps.

Carryover from 2012-13 into 2013-14 in the north of the Basin was 225 GL, compared to a carryover in the south of the Basin of 169 GL.

Whilst the carryover of Commonwealth environmental water into 2012-13 was higher proportionally in several northern NSW catchments than anywhere else in the Basin, it was relatively small when compared to the capacity of storages. For example, in the Gwydir catchment, 121.6 gigalitres of Commonwealth environmental water was carried over into 2013-14, which is equivalent to 8.9 per cent of the capacity of Copeton Dam. This was the largest volume of Commonwealth carryover in the Basin. In the Lachlan catchment, 65.6 gigalitres of Commonwealth environmental water was carried over, which is equivalent to 5.2 per cent of the storage capacity in that catchment.

In 2012-13, carryover allowed entitlement holders, including the Commonwealth, to use water carried over from 2011-12 to contribute to meeting their water use needs.

Annual reporting of carryover

The Commonwealth Environmental Water Office annual carryover report provides further information about the volume of water that has been carried over in the Basin each year. Over the longer term it is expected that the percentage of Commonwealth environmental water that is carried over will be similar to other water entitlement holders - although like all water entitlement holders it will vary from year to year.

1 Water sharing plans are NSW instruments that can be reviewed or changed from time to time.