Picture: Lake Fyans

Review of April 2022 Operations

Rainfall recorded during April was below average across most Wimmera-Glenelg reservoirs. The highest recorded monthly rainfall total was at Lake Bellfield which received 43.6 mm (or 72% of the historic average). Also noteworthy is Taylors Lake which received 39.4 mm, equivalent to 137% of the historic average for April. The lowest recorded monthly rainfall total was 21.4 mm at Toolondo Reservoir (62% of the historic average).

Despite most reservoirs recording below average rainfall during April, cooler conditions saw a very small amount of inflow recorded at Lake Wartook and Rocklands Reservoir (300 ML in total). Total inflow to the Grampians reservoirs for the water year to date (July 2021 to April 2022) increased from 73,340 ML to 73,640 ML, and continues to track at 42% of the historic average.

Between 6 April and 4 May 2022, the total volume in storage decreased from 174,900 ML (31.2%) to 168,830 ML (30.1%), representing a total decrease of 6,070 ML. This was the combined result of evaporation, very little inflow, and deliveries to entitlement holders.

The calculated net evaporation from reservoirs was approximately 1,660 ML during the month of April, with evaporation from storages exceeding rainfall. (Net evaporation considers rainfall on the reservoir as an evaporation offset).

During April, 2,890 ML of environmental water was released to waterways in the Wimmera catchment, and 1,350 ML to the Glenelg River.

Wimmera-Mallee Pipeline supplied recreation lakes received 190 ML during the month of April, and 1.9 ML was delivered to Wimmera-Mallee Pipeline connected wetlands during the month.

Consumptive entitlement holders collectively used 1,140 ML during April to supply their respective urban and rural demands.

 

May 2022 Operations

The Bureau of Meteorology (BoM) Climate Driver Update released on 26 April 2022 advised that the El Niño Southern Oscillation (ENSO) is exhibiting a continued weakening of the current La Niña. Climate models indicate a return to neutral ENSO conditions (neither La Niña nor El Niño) late in the southern hemisphere autumn. As La Niña weakens, it may continue to influence global weather and climate.

The Indian Ocean Dipole (IOD) is currently neutral, however outlooks indicate the possibility of a negative IOD developing in the coming months. BoM advises that model outlooks beyond autumn have a low accuracy at this time of year. A negative IOD increases the chances of above average winter–spring rainfall for much of Australia.

BoM rainfall outlooks indicate around a 65-80% chance of exceeding the median rainfall for May. Reservoir inflows during May remain dependent on the timing and magnitude of rainfall events during the month to further wet catchments and generate runoff. The Storage Manager will continue to monitor rainfall and catchment conditions through May, and will commence water harvesting activities should sufficient rainfall be received. Water harvesting is undertaken in accordance with Storage Management Rules, the Storage Manager’s Annual Operating Plan, and takes into consideration factors such as water quality and environmental objectives.

Upgrade works to the Lake Fyans dam wall will continue during May. Water levels at Lake Fyans have been closely managed over the past ten months in order to deliver this major upgrade. GWMWater (Storage Operator) is using this period of lower water levels to undertake works to improve long-term boat access onto Lake Fyans at both the southern marina and eastern boat ramp near Lake Fyans Holiday Park. Once this work is completed, the Storage Manager will seek to maximise water harvesting to Lake Fyans. The latest information on the Lake Fyans Dam Wall and Marina works can be found on the GWMWater website.

A number of reservoirs are projected to remain at suitable levels throughout May for a range of recreational activities. 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.

Blue-Green Algae above the levels safe for recreational contact have been recorded at Lake Lonsdale and Toolondo Reservoir. Information on all current algae warnings as well as general information on Blue-Green Algae is available from the GWMWater Algae Warnings webpage.