Review of July 2019 Operations
Opening inflows for the 2019-20 season were recorded at all reservoirs during July, with a total of 20,220 ML received (16,630 ML excluding Taylors Lake) This is equivalent to 48% of the historic average inflow for the same period (34,400 ML excluding Taylors Lake inflow). During July, the volume in storage increased, from 201,350 ML (36%) to 222,180 ML (39.7%).
Rainfall across the Grampians catchments was below average during July (69% average across all headworks storages). The highest rainfall for the month was 100.6 mm, recorded at Lake Wartook (71% of average), and followed by 95.2 mm recorded at Lake Bellfield (67% of average). Taylors Lake recorded the least amount of rainfall with 33.4 mm, however this equated to 78% of the monthly average which was the highest percent of average rainfall for the month at any storage. Calculated net evaporation from reservoirs was approximately
-2,160 ML for the month; with rainfall exceeding evaporation (Net evaporation considers rainfall on the reservoir as an evaporation offset).
There were no regulated environmental water releases in either the Wimmera or Glenelg catchments during the month of July. There was a total of 217 ML of passing flows delivered to the Glenelg system during July. No passing flows were delivered in the Wimmera system for July.
Wimmera-Mallee Pipeline supplied recreation lakes received 97.4 ML throughout the month of July. Supply to Wimmera-Mallee Pipeline connected wetlands within the Wimmera finished during early July with 1.66 ML delivered in July.
Consumptive entitlement holders collectively used 1,012 ML during July to supply urban and rural demands.
On 6 August, a transfer commenced from Rocklands to Taylors Lake. The Storage Manager determined that a transfer of up to 10,000 ML is necessary to support the demand from Taylors Lake over the remainder of the 2019-20 season. A transfer of up to 10,000 ML was outlined by the Storage Manager’s Annual Operating Plan 2019-20 under less than ‘average’ conditions.
Planned August 2019 Operations
The Bureau of Meteorology (BOM)
in their most recent El Niño -Southern Oscillation (ENSO) outlook have stated that all models currently indicate ENSO-neutral conditions will remain for the rest of 2019. This indicates that other climate drivers are likely to influence Australian weather for the remainder of the year.
The Indian Ocean Dipole (IOD) has recently risen above the positive IOD threshold. While the index has fluctuated around the positive IOD threshold, the broader Indian Ocean sea surface temperature, cloud and wind patterns have been consistent with a positive IOD since late May. Climate models now indicate that positive IOD conditions are likely to remain in the southern hemisphere for the remainder of winter and spring. Positive IOD events have historically resulted in below average winter–spring rainfall for southern and central Australia. Model outlooks indicate a positive Indian Ocean Dipole is likely to drive Australia's weather for much of the rest of 2019, meaning the likelihood of a drier than average winter–spring remains.
The Storage Manager will continue to focus on water harvesting to storages during August, with the next few months considered to be peak inflow periods. Initial rainfall in late June and early July both primed and generated some inflows to all storages, this is anticipated to continue in August.
The Rocklands to Taylors Lake transfer will continue through the month of August and will be monitored by the Storage Manager. No other transfers are planned for August.
Many reservoirs are anticipated to remain at suitable levels through August for a range of recreational activities. Recreation users are reminded to take care and abide by signage at reservoirs. Please refer to theReservoir 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