Review of March 2019 Operations
No measurable inflow was observed for a fifth consecutive month. Total inflows remain at 38,120 ML for the 2018-19 year to date (or 35,540 ML excluding Taylors Lake). This is equivalent to 20% of the historic average inflow for the same period (174,200 ML excluding Taylors Lake inflow).
During March, the volume in headworks reservoirs decreased from 220,290 ML (39.4%) to 205,260 ML (36.7%).
Rainfall across the Grampians catchments was well below average during March. The highest rainfall for the month was 14.4 mm, recorded at Moora Moora Reservoir (37% of average), followed by 14.0 mm recorded at Lake Bellfield (36% of average). Taylors Lake recorded the least rainfall for the month, with 2.8 mm (12% of average). Calculated net evaporation from reservoirs was approximately 5,800 ML for the month; with evaporation exceeding rainfall, (Net evaporation considers rainfall on the reservoir as an evaporation offset).
Environmental water releases continued in both the Wimmera and Glenelg catchments, with a total of 1,550 ML delivered to the Wimmera River from Taylors Lake, 160 ML supplied to the lower Mt William Creek from Lake Lonsdale, 355 ML supplied to the lower Mackenzie River and Burnt Creek from Lake Wartook, and 155 ML supplied from Lake Fyans to environmental refuge pools in Mt William Creek (upstream of Lake Lonsdale). A total of 1,925 ML was released from Rocklands Reservoir to the Glenelg River, including 150 ML of the Glenelg River Compensation Flow.
A transfer of 3,000 ML from Lake Bellfield to Lakes Fyans was conducted during March, consistent with the Storage Manager’s Annual Operating Plan. The transfer provided fresh inflows to Lake Fyans, benefitting water quality, and also boosted water levels by over half a metre, improving recreational access and supporting recreational opportunities.
A two week shut down at Rocklands Reservoir was coordinated during March to enable scheduled maintenance and clean-out of the four Carp exclusion units. Concurrently, new regulating gates were installed at the Rocklands Channel outlets to the Glenelg River, as part of a metering and water delivery infrastructure upgrade project.
Wimmera-Mallee Pipeline supplied recreation lakes received 320 ML throughout the month of March, with top-up supplies made to number of lakes. No water was supplied to Wimmera-Mallee Pipeline connected wetlands within the Mallee, North Central and Wimmera Catchment Management Authority areas.
Consumptive entitlement holders collectively used 1,740 ML during March to supply urban and rural demands.
Planned April 2019 Operations
The Bureau of Meteorology (BoM) in their most recent El Niño -Southern Oscillation (ENSO) outlook have stated that tropical Pacific Ocean temperatures have remained close to El Niño thresholds for a number of weeks. Subsequently, BoM have recently increased their ENSO outlook to “El Niño ALERT”. This suggests a 70% chance of El Niño conditions developing during autumn or winter 2019. At the present time, atmospheric indicators are not yet showing a consistent El Niño type response. Most international climate models indicate tropical Pacific Ocean temperatures will remain at El Niño levels to at least mid-2019. This presents an increased likelihood for ocean and atmospheric indicators to reinforce each other, paving the way for a full El Niño event. However, it should be noted that climate model accuracy tends to be lower at this time of year. During El Niño events, rainfall in south eastern Australia has historically been below average during winter and spring, with warmer daytime temperatures also occurring.
The Indian Ocean Dipole (IOD) remains neutral and is predicted to remain neutral for the remainder of autumn. The Indian Ocean Dipole generally has little influence on Australian climate between December and April. The Storage Manager will continue to monitor BoM climate outlooks and consider this information in its planning activities
The Storage Manager’s operational focus for April will continue to centre on the supply of entitlement holder requirements. Water releases for the environment are anticipated to continue throughout the month in both Wimmera catchment waterways and to the Glenelg River.
Many reservoirs are anticipated to remain at suitable levels through April 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