Review of April 2018 Operations
No measurable inflow was observed to reservoirs for a fifth consecutive month during April. Between July and April 67,250 ML of inflow has been recorded into headworks storages, which is 38% of the historic average for the same period (176,600 ML).
During April, the volume in headworks reservoirs decreased from 268,750 ML (48%) to 259,930 ML (46%).
Rainfall was below average at all reservoirs during April. The highest rainfall for the month was 35mm, recorded at Bellfield Reservoir followed by 30mm received at Lake Wartook.
Environmental water releases continued during April, with 750 ML supplied from Lake Wartook to the MacKenzie River, and 220 ML released from Lake Lonsdale to provide baseflows to the lower Mt William Creek. Rocklands Reservoir released 1,670 ML of environmental water to the Glenelg River. Taylors Lake delivered 960 ML to the Wimmera River before releases were suspended in late April for outlet channel maintenance works.
Wimmera-Mallee Pipeline supplied Recreation Lakes received 160 ML during the month.
Consumptive entitlement holders collectively used 1,080 ML during April to supply urban and rural demands.
Due to below average rainfall, net evaporation from reservoirs was approximately 2,300 ML for the month; with evaporation exceeding rainfall (Net evaporation considers rainfall on the reservoir as an evaporation offset).
Planned May 2018 Operations
The Bureau of Meteorology (BoM) in their most recent climate outlook predict predict a 40% to 45% chance of above average rainfall this May. BoM reports that the El Niño Southern Oscillation (ENSO) remains neutral, with neither El Niño nor La Niña conditions dominating. The current neutral ENSO indicator suggests that conditions over the coming months will not be particularly wet or dry. Most climate models surveyed by BoM suggest ENSO is likely to remain neutral for the reminder of autumn and winter.
It is noted that climate model which predict ENSO tend to have a lower accuracy during autumn compared with other parts of the year. The Storage Manager will continue to monitor BoM climate outlooks and consider this information in its planning activities.
There are no transfers between reservoirs planned for this month, however the Storage Manager will continue to monitor conditions. Further information in relation to water transfers are described in the Storage Manager’s Annual Operating Plan.
The release of environmental water and the routine delivery of water to consumptive entitlement holders is expected to be the Storage Manager’s operational focus during May. Due to dry catchment conditions, substantial rainfall will be required to wet catchments and begin generating inflow to reservoirs. As the catchment becomes saturated and inflows begin to occur, the Storage Manager’s focus will transition to water harvesting operations.
Reservoirs are expected to remain at suitable levels through May for a range of recreational activities, including boating at reservoirs where this is permitted. Please refer to the Reservoir information page for further information on water levels and recreation activities permitted at each reservoir.
While Blue-Green Algae (BGA) blooms are generally less common during the cooler months, there is still ability for these to occur. 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.