Storage Manager

October allocations for the 2026/27 water year.

Well below average monthly rainfall was recorded at all headworks sites across the Grampians during September. These conditions limited catchment flow and restricted inflow across the month. Residual rundown in the system and some rainfall was sufficient to generate 18,586 ML of inflow to storages during September, a reduction from the 42,558 ML recorded during August. A significant rainfall event did occur between 2^nd and 3^rd of October which was not captured in the inflow calculations but did contribute meaningful volumes of inflow to some storages.

Net evaporation increased during September with 4,660 ML recorded, a significant increase from the -2,270 ML calculated in August.

These improvements were sufficient to increase Wimmera-Mallee Pipeline Product entitlement allocations from 65% to 81%. Allocations were also made to Glenelg Compensations Flow (25%), Recreation (20%) and Wetlands (25%). 24.5 GL has also been allocated to the early system reserve. No allocation was possible to the Commonwealth Environmental entitlement.

With criteria for the Storage Manager to consider a Rocklands Reservoir to Toolondo Reservoir transfer being satisfied, the Storage Manager has completed an assessment of the likely impacts on the system using the guiding principles described in the Storage Management Rules.

These guiding principles were applied to the current and projected short-term conditions of both storages to determine if a transfer of either 5,000 ML or 10,000 ML would provide a positive outcome for both storages and entitlement holders in the system.

Key notes from the assessment are:

• Although models indicate some minor evaporative savings by either transfer volume, these saving were wholly negated by the volume projected to be lost to dead storage and transfer losses.
• Any volume transferred to Toolondo Reservoir is not expected to reduce the salinity in the lake, to the point where the water could be extracted and utilised by known demands (potential to reduce from 4,000 EC to 2,700 EC). Therefore, the volume of water was considered lost to the system from a supply point of view.
• The loss of transferred water through channel losses and to dead storage would likely result in a reduction in the volume of available water calculated for the Wimmera Glenelg Headworks System. This is likely to cause a reduction in potential entitlement holder allocation and does not support entitlement holder reliability or access to water.
• It is acknowledged that Toolondo Reservoir still holds some recreational and environmental values which would benefit from a water transfer. While these are important they are not prioritised above entitlement holder reliability and access to water.

Considering the above, a water transfer from Rocklands Reservoir to Toolondo Reservoir is not supported at this time. This may be reconsidered if the resource position of Rocklands Reservoir materially changes over the next few months.

September allocations for the 2026/27 water year.

Close to average monthly rainfall received to storages across the Grampians was sufficient to generate 42,558ML of inflow to storages. Net evaporation also contributed to a resource improvement with -2,270 ML in net evaporation calculated for system storages.

These improvements were sufficient to increase Wimmera-Mallee Pipeline Product entitlement allocations from 23% to 65%. Allocations were also made to Glenelg Compensations Flow (9%), Recreation (7%) and Wetlands (8%). 20 GL has also been allocated to the early system reserve. No allocation was possible to the Commonwealth Environmental entitlement.

August allocations for the 2026/27 water year.

Although rainfall was below the monthly average, it was sufficient to generate 28,301ML of inflow to storages. Net evaporation also contributed to a resource improvement with -920 ML in net evaporation calculated for system storages.

These improvements were sufficient to increase allocations from 12% to 23% for Wimmera-Mallee Pipeline Product entitlements. 20 GL has also been allocated to the early system reserve. No allocation was possible to Glenelg River Compensation Flow, Recreation, Wetland and Commonwealth Environmental entitlements.