Helping you understand shortfall risks in the lower Murray and how it affects you
What is a shortfall?
Shortfalls can occur when water available in the storage dams cannot be delivered to meet all the demands of customers at the time when they need it.
There are two types of shortfalls related to water delivery in the lower Murray:
- “Delivery shortfalls”: when actual water use is higher than it was forecast when river water was released from Hume and Dartmouth storages, weeks earlier, to meet the forecast needs for irrigation and environmental water. Delivery shortfalls are more likely to occur in an intense or extended heatwave that causes a sudden unexpected spike in demand.
- “System shortfalls”: when there is not enough capacity in the river and channel system to supply all downstream water needs. For example, when flows through Barmah Choke are already at full capacity and there is not enough water remaining in Menindee Lakes and Lake Victoria to meet all the lower Murray demands. System shortfalls are more likely to occur towards the end of the irrigation season.
There has always been a risk that during peak demand periods on the River Murray, water may not be able to be delivered to meet all demand downstream of the Barmah Choke. It takes about three weeks to deliver water from Hume Dam to Sunraysia.
The Barmah Choke is a narrow section of the River Murray and can pass a flow of around 9,200 ML a day downstream of Yarrawonga Weir before water starts to pass into the Barmah-Millewa Forest.
The Murray-Darling Basin Authority (MDBA) manages the River Murray System, with input from Goulburn-Murray Water and Lower Murray Water, to minimise the risk of shortfalls by regularly reviewing forecast demands, climate and flows and adjusting operations such as the timing of releases from Lake Victoria and Menindee Lakes, as well as from the Goulburn and Murrumbidgee Rivers.
The last time irrigators experienced a shortfall was in 2002. So, are shortfall risks in the lower Murray increasing? There have been significant changes across the connected Murray-Darling Basin over the last 10-20 years. Changes in both demand (more water being delivered to the lower Murray) and supply (reduced capacity) have increased the challenge of delivering water to users where and when it is needed without damaging the environmental health of our waterways.
What happens when a shortfall occurs?
When a shortfall occurs in the Murray, the MDBA will confirm the volume available for diversion by Victoria. This volume will be distributed to each of the affected water corporations including GMW.
GMW will then ration the available water for distribution based on demand and the volume of Delivery Shares or Extraction Shares held in the areas where the shortfall applies.
As a result, delivery rights (including delivery shares and extraction shares) will be used as the basis for sharing arrangements between water users. Therefore it is essential that customers place accurate orders to register their needs for irrigation supply in accordance with the system rules you operate in as described in the Goulburn-Murray Water Customer Charter.
How can we improve delivery management?
We are working closely with the Victorian Government and the MDBA and other states to manage these delivery challenges in the River Murray.
- The Minister for Water has been assessing applications for new or increased extraction share in the lower Murray since July 2019 to make sure they do not negatively impact existing entitlement holders or the environment
- In late 2021 new legislation was introduced to Parliament to strengthen Victoria’s framework for delivery rights in a shortfall and help individual water users manage their shortfall risks.
- New Goulburn trade and operating rules have been introduced in 2021-22 which make sure traded water can be delivered within ecological tolerances of the lower Goulburn River without increasing delivery risks in the Murray.
Jointly with the other states we are:
- Informing water users about their delivery risks
- Preparing coordinated response plans should a shortfall occur and water use needs to be rationed
- Monitoring new extractions, and assessing and reporting on any cumulative impacts to existing entitlement holders
- Reviewing how we operate the system to make sure delivery risks are minimised
For more information on what is happening on the River Murray and what is being done to manage the flows, go to the below links.