Picture: Lake Fyans

Review of November 2019 Operations

November was the first month in the 2019/20 water year where no measurable inflow was recorded at any reservoir. Year to date inflows for the 2019/20 season remain at 50,760 ML (42,740 ML excluding Taylors Lake), which is equivalent to 26% of the historic average inflow for the same period (161,600 ML excluding Taylors Lake inflow).

During November, the volume in storage decreased from 242,310 ML (43.3%) to 230,050 ML (41.1%). A decrease in storage volume was expected during November, but with windy conditions prevailing for much of the month, evaporation was uncharacteristically high given the mild daytime temperatures.

Rainfall recorded at Grampians reservoirs ranged between 81% and 42% of average during November. The highest rainfall for the month was 46.2 mm, recorded at Moora Moora Reservoir (79% of average), followed by 30.8 mm recorded at Toolondo Reservoir (81% of average). Taylors Lake recorded the lowest rainfall total with 16.6 mm, which equates to 54% of the monthly average.

Calculated net evaporation from reservoirs was approximately 4,200 ML for the month; with monthly evaporation exceeding rainfall (Net evaporation considers rainfall on the reservoir as an evaporation offset).

Environmental water releases to the MacKenzie River and Burnt Creek continued through the month of November. Environmental water was supplied to the Wimmera River from Taylors Lake and passing flows commenced from Lake Lonsdale.

Environmental water releases to the upper Glenelg River from Moora Moora Reservoir commenced during November. Passing flows and environmental water releases also recommenced from Rocklands Reservoir to the Glenelg River in late November.

Wimmera-Mallee Pipeline supplied recreation lakes received 198 ML throughout the month of November, and Wimmera-Mallee Pipeline connected wetlands received 11 ML.

Consumptive entitlement holders collectively used 1,380 ML during November to supply urban and rural demands.


Planned December 2019 Operations

The Bureau of Meteorology (BOM) in their most recent El Niño -Southern Oscillation (ENSO) outlook have remained consistent with previous statements, indicating ENSO-neutral conditions will remain for the rest of 2019. This suggests that other climate drivers are more likely to influence Australian weather for the remainder of the year.

A strong positive Indian Ocean Dipole (IOD) continues to persist although it has weakened slightly over the past couple of weeks. International climate models surveyed by the Bureau indicate the positive IOD event is likely to be slower to decline than usual, and may persist into mid-summer. Climate model outlooks indicate a positive Indian Ocean Dipole is likely to drive Australia's weather for the rest of 2019, meaning the likelihood of a drier than average summer remains.

The Bureau of Meteorology are predicting above average daily temperatures and below average rainfall for the remainder of December.

It is anticipated that the focus of reservoir operations during December will predominantly centre on routine delivery of water to entitlement holders, and operational actions to maximise headworks efficiency.

Many reservoirs are anticipated to remain at suitable levels through November for a range of recreational activities. Recreation users are reminded to take care and abide by signage at reservoirs. Please refer to the

Reservoir information page for further information on water levels and recreation activities permitted at each reservoir.

Blue-Green Algae blooms can be more common during warmer months. Recent Blue-Green Algae warnings for reservoirs can be found on the Storage Manager News Feed and all current warnings are available from the GWMWater Algae Warnings webpage.


1 ML = 1 megalitre = 1 million litres