Picture: Lake Fyans

Reservoir Operations Update

Review of February 2026 Operations

Mixed rainfall totals were recorded across Grampians storages during February. The highest rainfall total received was at Rocklands Reservoir with 54.2 mm (214% of the historic monthly average), followed by 36.2 mm recorded at Toolondo Reservoir (150% of the historic monthly average). The lowest monthly rainfall total was received at Lake Lonsdale with 11.4 mm (38% of historic monthly average).

A low-pressure system impacted Victoria between 27th February, and 2nd March provided some moderate falls to headwork storages. Although this system provided some moderate rainfall totals to the system, dry conditions throughout February resulted in very limited inflow being recorded to system storages over the assessment period. A total of 450 ML of inflow was recorded to storages during February, representing 23% of the historic monthly average. Inflow recorded in the July to February period (57,221 ML) represents 33.2% of the historic average for the same period.

Between 31st January and 4th March 2026, the total volume in storage decreased from 218,870 ML (39.1%) to 204,790 (36.5%), representing a total decrease of 14,080 ML (2.6% of total operating capacity). Lake Wartook continues to be of particular interest, currently holding 10,870 ML (37%), an 870 ML (3%) reduction since the February resource assessment. Without continued rainfall at or above the month average, consistent demand from the storage is expected to cause further resource declines.

Evaporative losses from storages continued to be high during February, with 7.38 GL of net evaporation recorded during the month. This is a decrease from the 13.27 GL recorded in January. Losses are expected to reduce through the autumn period but remain a liability on the available water balance. This trend is expected to continue until monthly rainfall exceeds the rate of evaporation, most likely over the winter period.

Regulated environmental deliveries were active throughout February with the following river systems receiving water:

  • 3,364 ML delivered to the Glenelg River from Rocklands Reservoir,
  • 831 ML delivered to the Wimmera River from Taylors Lake, and
  • 125 ML delivered to the MacKenzie River from Lake Wartook and Moora Moora Reservoir.

There was also 122 ML of passing flow released to the Glenelg River downstream of Rocklands Reservoir.

Consumptive entitlement holders collectively used approximately 1,862 ML during the month to supply respective urban and rural demands.

March 2026 Operations and Climate Outlook

The Bureau of Meteorology (BoM) report there is no clear forecast signals in March for most of southern Australia, with below average rainfall signals strengthening and expanding to cover much of Australia from April. It’s also noted that there is an increased chance of unusually low rainfall (representing rainfall that is in the driest 20% of historic records) for parts of Victoria from April.

Short-term forecasts for the Wimmera-Glenelg headworks area suggest an average chance of receiving median rainfall conditions across the Grampians during March.

Medium-term outlooks indicate a less than 35% chance of rainfall exceeding the median for the March to May period. Daytime temperatures are expected to remain elevated, with the BOM projecting a >60% chance of exceeding median max temperatures for the March to May period.

A 1,500 ML transfer from Lake Bellfield to Lake Fyans is scheduled to occur in March. This transfer is required to ensure adequate supply for the urban centres of Ararat, Stawell and Great Western. Increased water levels at Lake Fyans will also support recreational opportunities over the Easter period.

Reservoirs are projected to hold suitable levels during March for a range of recreational activities, however evaporation losses over autumn are likely to cause a steady decline in water levels. Recreation users are reminded to take care and abide by signage at reservoirs. Please refer to GWMWater’s Reservoir information page for further information on water levels and recreation activities permitted at each reservoir.

There is currently a Blue-Green Algae warning issued for Lake Lonsdale. Information on all current algae warnings, as well as general information on Blue-Green Algae, is available from the GWMWater Algae Warnings webpage.