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Water

Rising water allocations impact carryover

In doubt: Extra low reliability water may be at risk when it is transferred into spillable accounts. Photo by Geoff Adams

Extra low reliability allocations for the Murray Valley district of northern Victoria have been welcomed, but the extra water may be at risk when it is transferred into spillable accounts under carryover water rules.

As it has been some time since low reliability water has been available, the VFF is endeavouring to clarify the announcement and its impact on carryover, and has released the following explainer:

On January 17, the Northern Victorian Water Resource Manager increased the Murray low reliability allocation from 12 per cent to 72 per cent.

This resulted in much of the remaining water farmers had carried over against their low reliability water shares being transferred to spillable water accounts, similar to what happened for water that was carried over against high-reliability water shares earlier in the season.

Water entitlement holders are able to carry over water and store more water than their full water entitlement volume when there is space in the storages.

Currently the major storages providing water to the Murray see the Hume Dam being 99 per cent full and Dartmouth Dam 91.77 per cent full.

Since August, releases have been made from Hume to maintain the storage level close to 100 per cent of capacity. These releases are classified as spills from spillable water accounts as the new inflows have not been able to be stored due to carryover occupying more than entitlement volume. Releases have continued in January with recent rainfall meaning further deductions from spillable accounts is likely.

Carryover and spill volumes explained

The volume remaining in spillable water accounts depends on how much was carried over against low-reliability water shares.

If there are further seasonal determination increases for low-reliability water shares in the Murray, more water will transfer into spillable water accounts.

For example, a farm with 200Ml of high reliability water shares with a 100 per cent allocation and 100Ml of low reliability water shares with a 72 per cent allocation. The farmer in this example carried over 100Ml against their low reliability at the start of the season. Five per cent of carryover was lost due to evaporation, bringing the carryover volume down to 95 Ml.

The numbers: The Victorian Water Register provides detail on the volumes of water carried over at the start of the irrigation season in July 2021.

In summary, 300Ml remains available to this farmer but 67Ml has been transferred into a spillable water account and as a result is subject to spill if Hume Dam spills occur this season.

The VFF believes more work is required to allow spilled water to be captured by farmers where this can be done within Victoria’s sustainable diversion limits.

Additionally, this water is freely flowing to the environment and may not be counted as environmental water.

Farmers wanting to understand their position can refer to the carryover calculator on the Victorian Water Register at https://www.waterregister.vic.gov.au/water-entitlements/carryover/carryover-calculator