Victorian carryover water explained

Victorian carryover water explained

29 May 2019

The Victorian water system can be difficult to understand. Tyson Milne, Senior Technical Officer – Irrigation Extensions with Lower Murray Water, has prepared this article on carryover water, to help explain.

Carryover is the opportunity to make use of unused storage space to carry unused water from one season for use in the next, so long as it does not impact allocations in the following season.
This information relates only to Victorian ABA’s and Water Shares, other states have different systems and processes.
In Victoria carryover makes use of unused storage space in Hume Dam, and is the first water lost if water spills from Victoria’s share of Hume.
Carryover is not new allocations of water, it is water allocated in the previous season which was not used.
It is important to understand that carryover is against your Water Shares, not your ABA.
To carry over water in your ABA you must have a Water Share attached to it – either by owning it or on a Limited Term Transfer (a type of lease for a Water Share).
The Water Share can be either High Reliability or Low Reliability, but carryover water is recorded against Low Reliability Water Shares first.
The maximum volume of water you can carryover is the volume of Water Shares attached to your ABA – any water in excess of this will be written off at the end of the current season.
A 5 % deduction is made to cover evaporation on the 30th of June eg: if you had 100 ML remaining in your ABA on the 30th of June you would have 95 ML of carryover on the 1st of July.
Your carryover (minus the 5 % deduction) is available in your ABA to trade or use from the 1st of July.
This is the case even if there has not yet been a seasonal allocation – your carryover is water that was allocated in the previous season and is therefore available for immediate use.
Once allocations begin to be made the maximum volume of water which can be allocated to your ABA, either as carryover or allocations, is the total volume of your Water Shares.
Any allocations which exceed this volume instead go in to your Spillable Account. For example, if you had a 100 ML Water Share and 50 ML of carryover on the 1st of July any allocations up to 50 % would go to your ABA, but once allocations reached 50 % any remaining allocations would go to your Spillable Account instead.
If you only had 20 ML of carryover on the 1st of July allocations would not go to your Spillable Account until they reached 80 %.
Water in your Spillable Account is quarantined until a Low Risk of Spill declaration is made, indicating that the risk of a spill from Victoria’s share of Hume Dam is less than 10 %.
If there is a spill from Hume while water is still in Spillable Accounts a proportion of the water in each Spillable Account will be lost.
A spill does not need to be a physical spill with water flowing over the dam wall, it can also be because Victoria’s share of the dam is full and is “spilling” to NSW’s share.
Once a Low Risk of Spill declaration is made any water remaining in your Spillable Account is returned to your ABA and is available for use or trade.
While this may seem complicated the Victorian Water Register website has an excellent tool (http://waterregister.vic.gov.au/CarryoverCalculator2014/index.html) which allows you to enter your own details, including Water Share volumes and estimated amount of carryover, and you can try different allocation scenarios to see how they impact on you.
If you have any questions on carryover you can contact your Water Broker or Lower Murray Water on (03) 5051 3400.
Your Water Broker may also be able to advise you on alternatives to carryover such as “parking” (carrying water over on another user’s Low Reliability Water Share) or forward contracts which may be better suited to your situation.

The picture above shows an example of the Carryover Calculator tool. In this case the grower has a 100 ML Water Share and had 50 ML of carryover on the 1st of July.

A 75 % allocation was then made which gave them 50 ML of carryover plus 100 x 75 % = 75 ML of allocation which is a total of 125 ML. This exceeds their Water Share volume of 100 ML, so the remaining 25 ML has been placed in their Spillable Account until a Low Risk of Spill declaration is made.

While in the Spillable Account some or all of this water may be lost due to spill.