OPERATIONAL planning for the River Murray has recently been updated because of potential dry conditions continuing through to winter next year.
Murray-Darling Basin Authority River Management executive director Andrew Reynolds said the 2018-19 River Murray System Annual Operating Plan had been updated to reflect the low rainfall and relatively warm conditions experienced across much of the southern Basin over the past winter and spring.
"While we had a small amount of rain in August, things were unusually dry in July and September, which is typically when the system receives most of its rainfall and inflows," he said.
"We will continue to plan for all scenarios, including very wet conditions, but this update reflects the greater possibility that dry or very dry scenarios will eventuate.
"We have been transferring water to Lake Victoria during spring to improve its storage in preparation for the demands of summer, but under dry scenarios we will look to target a volume less than 350 gigalitres, half its capacity, by the end of May 2019.
"Going into winter 2019 with low volumes held in Lake Victoria provides us the greatest opportunity to capture any winter inflows that enter the system downstream of Hume Dam.
“With Lake Victoria having a relatively large surface area and situated in a hot and windy part of the Basin, this also helps to increase water availability in 2019-20 by minimising the loss of water through evaporation.
"Under all dry scenarios we continue to run the river high downstream of Yarrawonga, in anticipation of heavy irrigation demand throughout the Murray.
"We are conscious, however, that if conditions remain dry there is the possibility that demand will reduce as water entitlement holders with an allocation will elect to carry over some of their water to the next year."
Mr Reynolds said another key change in the update was the ability to use Murray Irrigation Limited canals to deliver water downstream of Barmah Choke, where the narrowing of the river limits the volume of water that can pass through.
"We are keenly aware of the difficult times many people are facing due to the drought,” he said. “This access helps us to reduce the risk of a shortfall in water delivery during times of peak irrigation demand.
"Environmental water holders have so far used less water than they would in an average year, in part because the usual overbank flows in the Barmah-Millewa forest caused by winter rain did not eventuate and as a result there was no natural event to extend. In this challenging season, having available water sources limited to Hume Dam releases and the Goulburn River has also impacted our ability to deliver water for the environment at the same time as moving water through the system to Lake Victoria.
"Looking forward, there is the possibility for more environmental water to be used but this will depend on system capacity and the environmental priorities that are identified."
Mr Reynolds said the updated operating plan helped river operators to manage water deliveries and provided a transparent signal to water entitlement holders about the likely risks and opportunities in the period ahead.
"We urge everyone who uses water to plan ahead for all scenarios, including the possibility that conditions stay dry and allocations do not improve,” he said.
“None of us know with certainty how much water we’ll have in storage at the end of the season – that depends on how much it rains.”
The update is prepared by the MDBA with input from the federal government and the Basin states of SA< NSW and Vic.
- Details: MDBA website