Updated seasonal determinations
The Resource Manager for northern Victoria today updated the 2021/22 seasonal determinations.
The Murray system moves from 31 per cent of high-reliability water shares (HRWS) to 46 per cent HRWS. The Goulburn and Loddon systems increase from 37 per cent HRWS to 59 per cent HRWS.
The Campaspe system moves from 23 per cent HRWS to 59 per cent HRWS. The Broken system increases from 8 per cent HRWS to 67 per cent HRWS.
Seasonal determinations in the Bullarook system remain unchanged at 100 per cent HRWS and 100 per cent of low-reliability water shares.
Resource Manager Mark Bailey said rainfall on wet catchments led to the increases announced today.
“The catchments in all systems are wet and responding strongly to rainfall,” Dr Bailey said.
“Rain since the last assessment has increased the flow of water into the rivers and creeks across the region, adding to the volumes in the major storages and making more water available for allocation.”
Dr Bailey noted water levels at Lake Hume are rising quickly and the Murray-Darling Basin Authority is preparing to make releases to slow the rate of rise.
“Releases to control storage levels are treated as spills in Murray system accounting, which will cause deductions from spillable water accounts,” he said.
“Murray system entitlement holders will be informed about spills when they occur and the volumes are confirmed by the Murray-Darling Basin Authority.”
The seasonal determinations announced for the Murray and Goulburn systems marked the full establishment of the early season reserve in both systems. The early season reserve is designed to ensure there is sufficient water available to operate a system and deliver carried over allocation next season.
“Having established the early reserves, future resource improvements will be directed towards seasonal determinations against high-reliability water shares,” Dr Bailey noted.
“Resource improvements in the Murray system after the seasonal determination reaches 50 per cent HRWS will also contribute to allocating the volume owed to the Barmah Millewa Forest Environmental Water Allocation.”
Dr Bailey said the latest Bureau of Meteorology seasonal outlook favours above-average rainfall across the catchment areas for the three month period from August to October.
“The Bureau has confirmed that a negative Indian Ocean Dipole is underway, which increases the likelihood of above-average rainfall totals in south-east Australia.”
The seasonal determinations for northern Victorian water systems on Monday, August 2
Allocation trade from New South Wales to Victoria is limited to the lesser of a net annual volume of 200 GL or a volume that keeps the risk of spill in the Victoria’s share of the both Hume and Dartmouth reservoirs below 50 per cent. The current risk of spill in the Murray system allows 200 GL of net trade from New South Wales to Victoria. This volume is updated with each risk of spill announcement. Customers can learn about trade adjustments on the Water Register website.
An interim rule for trade from the Goulburn, Broken, Campaspe and Loddon systems to the Victorian Murray system, New South Wales and South Australia is in effect from 1 July 2021 to 30 June 2022, replacing the previous rule that had been in place since 2013. The new trade rule means that until December 15, 2021, trade is allowed whenever the total amount owed from the Goulburn to the Murray, including the Lower Broken Creek, is less than 190 GL. From December 15, 2021, net trade will be capped and the inter-valley trade account balance will be run down.
The volume currently committed to the Murray is 190 GL, meaning trade from the Goulburn, Broken, Campaspe and Loddon systems to the Victorian Murray system, New South Wales and South Australia is closed. More details about the new trade rule are available at Water Register website.
The Goulburn, Campaspe and Loddon systems can trade from the Victorian Murray system, New South Wales and South Australia while the total volume owed to the Murray system is greater than zero.
Customers participating in the water trading market can monitor trade availability on the Water Register website.
The Murray-Darling Basin Authority (MDBA) is restricting trade of water allocations from above the Barmah Choke to downstream of the Choke to protect the delivery of downstream water entitlements. Customers can monitor trading opportunities across the Barmah Choke on the MDBA website.
Upcoming Resource Manager announcements
- The next risk of spill update will be released on Tuesday 10 August 2021.
- The next 2021/22 seasonal determination announcement will be released on Monday 16 August 2021.
The Murray system moves from 94 per cent of high-reliability water shares (HRWS) to 100 per cent HRWS.
The Goulburn system and the Loddon system increase from 88 per cent HRWS to 93 per cent HRWS.
The seasonal determination in the Broken system increases from 24 per cent HRWS to 30 per cent HRWS.
The Campaspe system remains at 100 per cent HRWS and the Bullarook system remains at 100 per cent HRWS and 100 per cent of low‑reliability water shares (LRWS).
Resource Manager Mark Bailey said recent rain helped to improve water availability.
“Most of northern Victoria received some rainfall during the first half of December,” said Dr Bailey.
“The rainfall across the northeast catchments increased the flows into the storages and in the downstream rivers,” said Dr Bailey. “The flows were higher than our conservative estimates, and together with lower evaporation from the storages, provided additional resource to allocate.”
Dr Bailey noted these factors will influence seasonal determination improvements in the coming months.
“The seasonal determination outlook to 15 February 2019 is based on historical flows into the major storages under different scenarios,” said Dr Bailey. “These flows are generally low at this time of year. Seasonal determination assessments include estimates of evaporation and river losses.
“As we have seen, if actual losses are lower than these estimates, more water is available to allocate.”
Dr Bailey noted the climate outlooks for summer rainfall did not favour wetter or drier conditions.
“The latest Bureau of Meteorology seasonal outlook indicates there is an even chance of receiving above average rainfall during the December to February period,” Dr Bailey said. “The Bureau has issued an El Niño Alert, meaning the chance of an El Niño forming in the coming months is around 70 per cent. It is likely that the positive Indian Ocean Dipole is nearing its end, but it has little influence on rainfall from December to April.”
Dr Bailey urged water users to continue planning their water needs carefully. “Websites such as the Resource Manager ( www.nvrm.net.au ), the Victorian Water Register ( www.waterregister.vic.gov.au ) and the Murray-Darling Basin Authority ( www.mdba.gov.au ) provide information about water trends and availability, which can help users plan their use.”
The seasonal determinations for northern Victorian water systems on Monday, December 17 are: