In most years, there is enough Murray River capacity to deliver water to meet customer needs. However, in rare circumstances, high demand or river capacity constraints can result in a shortfall, meaning not all water can be delivered when and where it is required.
This page explains how shortfalls work and how to use the Extraction/Delivery Share Calculator to understand what they could mean for your water access.
What is a shortfall?
- 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 Narrows 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 Narrows. It takes about three weeks to deliver water from Hume Dam to Sunraysia.
The Barmah Narrows 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.
How are customers affected?
If a shortfall occurs, rationing may be introduced. Rationing uses
Extraction/Delivery Shares to determine how much water can be taken at each service point during the rationing period. Your available water will depend on:
- The location of your service point
- The ration percentage in your river reach
- The Extraction/Delivery Shares assigned to your service points
This approach helps ensure all customers receive their fair share of the available delivery capacity.
Calculate your Extraction/Delivery Share
The Extraction/Delivery Share Calculator (below) allows you to see how rationing may affect your water access.Using the calculator, you can:
- View current rationing levels for your river reach
- See how current rationing applies to your service points
- Test different rationing scenarios
- Compare impacts across multiple service points to support planning decisions
Extraction/Delivery Share Calculator
More information
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.