Review of March 2026 Operations
Well above average rainfall totals were recorded across Grampians storages in early March. The highest rainfall total received was at Lake Bellfield with 73.2 mm (194% of the historic monthly average), followed by 61.4 mm recorded at Lake Fyans (221% of the historic monthly average). The lowest monthly rainfall total was received at Lake Lonsdale with 32.4 mm (110% of historic monthly average).
A low-pressure system impacted Victoria between 27th February and 2nd March providing moderate falls to headwork storages. Although this system provided some moderate rainfall totals to the system, dry conditions throughout March. These conditions resulted in very limited inflow being recorded to system storages over the assessment period. A total of 92 ML of inflow was recorded to storages during March, representing 5% of the historic monthly average. Inflow recorded in the July to March period (57,335 ML) represents 32.9% of the historic average for the same period.
Between 4th March 2026 and 1st April 2026, the total volume in storage decreased from 204,790 ML (36.5%) to 194,030 ML (34.6%), representing a total decrease of 10,760 ML (1.9% of total operating capacity). Lake Wartook continues to be of particular interest, currently holding 9,960 ML, a 910 ML (3%) reduction since the March 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 reduced significantly during March, with above average rainfall offsetting daily evaporation. A total net evaporation of 3.84 GL was recorded from storages during March, well below the volume of 7.38 GL calculated for February. 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.
A 1,630 ML system transfer between Lake Bellfield and Lake Fyans was completed in early March. This transfer was timed to occur after the low-pressure system in early March to ensure any losses would be minimised. Lake Fyans is a critical supply point for the Townships of Ararat, Stawell and Great Western, along with existing and developing rural pipelines.
Regulated environmental deliveries were active throughout March with the following river systems receiving water:
- 1,533 ML delivered to the Glenelg River from Rocklands Reservoir,
- 1,159 ML delivered to the Wimmera River from Taylors Lake, and
- 136 ML delivered to the MacKenzie River from Lake Wartook and Moora Moora Reservoir.
Consumptive entitlement holders collectively used approximately 1,256 ML during the month to supply respective urban and rural demands.
April 2026 Operations and Climate Outlook
The Bureau of Meteorology (BoM) report climatic conditions reflect a neutral El Niño–Southern Oscillation (ENSO) state. 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 a below average chance (<30%) of receiving median rainfall conditions across the Grampians during April.
Medium-term outlooks indicate a less than 20% chance of rainfall exceeding the median for the April to June period. Daytime temperatures are expected to remain elevated, with the BOM projecting a >80% chance of exceeding median max temperatures for the April to June period.
With short- and medium-term outlooks suggesting dry climatic conditions are likely to persist across autumn and into winter. There is an increased likelihood of a delayed start to system inflows over the traditional inflow period (June-October).
Reservoirs are projected to hold suitable levels during April 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.