How water is allocated
The Water Allocation Plan for the River Murray Prescribed Watercourse (the Plan) includes principles to guide the process for making water available for allocation to entitlement holders. Water available for allocation comes from South Australia’s River Murray Entitlement of up to 1,850 gigalitres (GL) per annum under the Murray-Darling Basin Agreement (the Agreement).
The Plan sets out a transparent approach to making water available for allocation and the hierarchy applied when allocations are made. This takes into account economic, social and environmental considerations.
The approach to allocating water was developed in collaboration with the SA Murray-Darling Basin Natural Resource Management Board’s community-based River Murray Advisory Committee (RMAC) and other key stakeholders. Further community input was provided during the consultation process on the draft Plan.
How is the volume of water available to South Australia from the River Murray determined?
In most years, South Australia receives its full Entitlement of 1,850 GL, which is made up of:
- Dilution and Loss Entitlement – 696 GL
- Consumptive Entitlement – 1,154 GL
The actual volume of Entitlement that South Australia receives each year is determined by the Murray-Darling Basin Authority (MDBA) in accordance with the water sharing rules of the Agreement. These rules set out how water must be shared between South Australia, New South Wales and Victoria.
Once advised by the MDBA on Entitlement availability, the principles in the Water Allocation Plan for the River Murray Prescribed Watercourse guide the process for determining how much water can be made available for allocation from one of four consumptive pools. These are:
- Metropolitan Adelaide
- All purpose
What happens in dry years?
During dry periods, South Australia’s Entitlement may be less than 1,850 GL. In these years, there may not be enough water available to meet the needs of all water users, including the environment. A transparent process for allocation decision making assists all water users in planning and preparing for dry conditions. This process is set out in Chapter 5 of the Water Allocation Plan for the River Murray Prescribed Watercourse and explained in the water allocation fact sheet.
When South Australia does not receive its full Entitlement of 1,850GL, the opening allocation for any water access entitlement on 1 July may be less than 1 kL per share. When this happens, allocations are reviewed at least monthly until South Australia is advised by the MDBA that it will receive its full Entitlement. If water conditions and storage volumes improve, allocations to water access entitlement can be increased.
In the last 15 years since 2002-03, the average improvement to restricted opening allocations for irrigators over the course of the water year has been 37 per cent.
The timing of these improvements to irrigator allocations has coincided with the general pattern of inflows to the broader River Murray System from winter‑spring rainfall and snowmelt. On average, 74 per cent of allocation improvements have been received by the end of October.
Increase in irrigation allocations in dry years
The Adelaide Desalination Plant (ADP) has been explicitly incorporated into how future River Murray water allocations are made. As a result, the ADP is making a major difference to how SA Water's water is shared between all users of the SA River Murray in dry years – with 50 GL of available River Murray water to be released to holders of irrigation licences in these years. This corresponds to an 8 percentage point increase in irrigators’ allocations from the Murray when allocations are below 100 per cent.
For example, under the very dry conditions that prevailed at the start of the 2016-17 water year, this policy change would have boosted irrigators’ opening allocations from 36 per cent to 44 per cent.
Boosting allocations to irrigators during dry times helps protect jobs and support industries in the South Australian Murray-Darling Basin. The extra volume for irrigators will be crucial for meeting the survival needs of permanent plantings during dry years and helps maintain business confidence in the irrigation sector and across the region.
Other state water sharing plans: