2025/26 opening seasonal determinations and risk of spill update
The Resource Manager for northern Victoria today announced the first 2025/26 seasonal determinations, together with updated determination outlooks and the initial risk of spill assessment for the Murray, Goulburn and Campaspe systems.
The Murray system starts 2025/26 with a seasonal determination of 39 per cent of high-reliability water shares (HRWS). The Goulburn and Loddon systems begin with 31 per cent HRWS.
The Campaspe system starts 2025/26 with 100 per cent HRWS. The Broken and Bullarook systems both start the year with 0 per cent HRWS.
Resource Manager Mark Bailey said the opening seasonal determinations were lower than recent years, except in the Campaspe system.
“Drier conditions through 2024/25 meant we had fewer reserves for the opening seasonal determinations compared to the last few years,” Dr Bailey said. “The Campaspe system was the exception and secured enough reserves for a 100 per cent seasonal determination.
“More water is needed in the Broken and Bullarook systems before seasonal determinations can increase.
“Recent rainfall in the catchment areas is welcome, but continued rainfall is needed over the coming months to increase storages levels and seasonal determinations across all systems.
“With below-average storage flows during May and June, the risks of spill have decreased since the last update was released in May 2025.
“The spill risk in both the Murray and the Campaspe systems is 40 per cent. In the Goulburn system, the risk of spill from Lake Eildon is about 25 per cent.
Dr Bailey said the risk of spill assessment did not describe the chances of flooding this season. “The risk of spill is a water accounting assessment. It does not refer to flood risks downstream of the storages.”
Further detail on outlook for the 2025/26 Season
The Bullarook seasonal determination outlook for 2024/25 is based on historical flow records that have been adjusted to match climate conditions observed since 1975. The outlook scenarios presented are:
- Wet Inflow volumes to major storages that are greater in 10 years out of 100
- Average Inflow volumes to major storages that are greater in 50 years out of 100
- Dry Inflow volumes to major storages that are greater in 90 years out of 100
- Extreme Dry Inflow volumes to major storages that are greater in 99 years out of 100
The following table summarises possible high-reliability water share seasonal determinations through the season and include a reference year to help users recognise the possible inflow conditions.
Murray System Outlook for Seasonal Determination of High-Reliability Water Shares
| Wet |
2021/22 |
83% |
100% |
100% |
100% |
| Average |
2014/15 |
60% |
97% |
100% |
100% |
| Dry |
2015/16 |
49% |
68% |
80% |
94% |
| Extreme Dry |
2006/07 |
40% |
41% |
43% |
46% |
Goulburn and Loddon System Outlook for Seasonal Determination of High-Reliability Water Shares
| Wet |
2016/17 |
78% |
100% |
100% |
100% |
| Average |
2021/22 |
50% |
92% |
100% |
100% |
| Dry |
2024/25
|
38%
|
49% |
61% |
67% |
| Extreme Dry |
2006/07 |
33% |
35% |
38% |
39% |
Broken System Outlook for Seasonal Determination of High-Reliability Water Shares
| Wet |
2016/17 |
63% |
100% |
100% |
100% |
| Average |
2021/22 |
63% |
100% |
100% |
100% |
| Dry |
2018/19 |
0% |
0% |
12% |
17% |
| Extreme Dry |
2006/07 |
0% |
0% |
0% |
0% |
Bullarook System Outlook for Seasonal Determination of High-Reliability Water Shares
| Wet |
|
100% |
100% |
100% |
100% |
| Average |
2012/13 |
100% |
100% |
100% |
100% |
| Dry |
2007/08 |
0% |
0% |
0% |
0% |
| Extreme Dry |
2015/16 |
0% |
0% |
0% |
0% |
Seasonal determinations under additional scenarios for each system are available from the .
Upcoming Resource Manager Announcements
- The risk of spill in the Murray, Goulburn and Campaspe systems will be updated on Thursday July 10, 2025.
- The next 2025/26 seasonal determination announcement will be released on Tuesday July 15, 2025. An updated outlook will be released with this announcement