Managing drought risks through new water-allocation outlooks: promoting adoption & supporting decision making

Vic Drought Hub - Farmland 1
  • MRIC (NW Irrigated Horticulture Node)
  • Water Management

Identified as a priority during the initial round of drought consultations with stakeholders, this project will use a proof-of-concept project calibrated earlier for Goulburn River System and calibrate it for Murray River System. The proof-of-concept project used BOM stream-flow forecasts to provide real-time forecasts grounded in current-year weather, rather than in potential climate scenarios. Using actual stream-flow forecasts reduces uncertainty of water allocation by 50% and improves decisions making with better prediction of available water in the current season.

bom-streamflow-forecast
Three-month streamflow forecast sourced from the Bureau of Meteorology.

Project status: on track

Project start date: 20 December 2023

Expected end date: 30 June  2024

Vic Hub partner organisation: The University of Melbourne

External partners: Bureau of Meteorology (BOM), Goulburn Murray Water (GMW) and Murray Darling Basin Authority (MDBA)

Identified as a priority during the initial round of drought consultations with stakeholders, this project will use a proof-of-concept project calibrated earlier for Goulburn River System and calibrate it for Murray River System. The proof-of-concept project used BOM stream-flow forecasts to provide real-time forecasts grounded in current-year weather, rather than in potential climate scenarios. Using actual stream-flow forecasts reduces uncertainty of water allocation by 50% and improves decisions making with better prediction of available water in the current season.

 

Update: April 2024

Successful completion of:

  • computer model to replace the current method of determining seasonal water allocations over at least 3 irrigation seasons, including 2017-20
  • computer model to use new method of determining seasonal water allocations over at least 3 irrigation seasons including 2017-20
  • an analysis comparing uncertainties involved in each method

New model for improved water forecasting

A new method for forecasting seasonal water allocations could be the “single most important” development to help reduce the impact of the next drought on Mallee irrigators.

The method has already been trialled on the Goulburn River system and was found to be much more accurate than the current method in predicting what water allocations will look like during the

MRIC consultant Tim Cummins said the new method was able to reduce the uncertainty of water allocation outlooks by up to 50%.

“Increasingly we are seeing horticultural enterprises developed in the Mallee with people more prepared to rely on the water market to meet their water requirements each year, and they are going to be the major beneficiaries of this project,” Tim said.

“What it means is people would have more-certain information about the water allocations they may get, so they can make better, more definite decisions about what to do with the water – whether to sell, buy or hold – and what crops to plant.

“It should also make the market more efficient because there is more information and more certainty, so people can make decisions with less risk for them.”

‘In times of drought, having more certainty about where allocation levels are going to end up will help minimise the need for irrigators to dry off high-value orchards and vineyards. Drying off crops would result in a significant economic loss in that year. But because we’re dealing with perennial horticulture crops, it would take another 4 or 5 years to get those irrigated lands back to full development.’

The new method produces water-allocation outlooks based on the BOM’s seasonal streamflow forecasts, which are grounded in the weather and catchment condition of the current year.

water-forecasting-project
University of Melbourne research fellow and project team member Tristan Graham.

In contrast, the old method provides estimates based on scenarios from historical climatic records (e.g., wet, average, dry and extreme dry), and the likelihood of each of those scenarios playing out in the current year is not communicated to irrigators.

The University of Melbourne’s Professor QJ Wang said while no decisions had been made, Northern Victoria Resource Manager Dr Mark Bailey was keen to implement the new method. This would involve running both methods in parallel to give stakeholders time to get used to the new system.

“With the support of the Mallee Regional Innovation Centre and the Victoria Drought Hub, we are now working to evaluate the technology on the Murray system, which is much more complex,” QJ said.

“This project really needed the help of GMW, the MDBA and the Bureau of Meteorology. All the organisations have been enthusiastic and supportive, and what it probably comes down to is that they all see the practical value of the project and the difference it could make to water users and the market.”

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Project Background

Irrigators and other water users rely on water allocation outlooks (forecasts) provided by water agencies to help them make their farming and business decisions for the coming irrigation season.

In current outlooks, estimates of water allocations are given under different historical climate scenarios; however, the scenarios have a wide range of uncertainty, and the onus is on the end-users to work out risk distributions.

Professor QJ Wang from The Melbourne University water team has recently developed a novel method to produce water allocation outlooks based on seasonal streamflow forecasts from the BOM. This new method improves the accuracy of the allocation outlooks and narrows their uncertainty range by up to 50%. The project’s aim is to enable water agencies to adopt the technology and roll out new water-allocation outlooks across Northern Victoria, and to support end-users to transition to the new outlooks, and thereby make more informed decisions and manage drought with greater confidence.