State of the Storages
June 2011
Dam levels started autumn at 54.2% and finished the season at 54.5% - a net gain of 6.9 billion litres.
On the face of it, the rise seems modest, but storages typically drop by 5% over this period, so they’ve effectively bucked the trend by 5.3%. The city’s dams are at their highest levels for the start of winter since 1999.
This rise in storages was due to good rain (31% above average) falling on catchments already damp from a wet summer. As a result, streamflow into the major harvesting dams was more than double the average.
The added bonus of a wetter-than-average autumn is that the catchments are primed to make the most of winter rainfall. In recent years, autumn has been dry so a lot of the winter rain was absorbed before it started to produce runoff into the dams.
With many of the smaller dams full or filling, any noticeable increases in 2011 will depend mainly on what happens over the Thomson Dam. The Thomson accounts for two-thirds of total system capacity and is the Melbourne’s largest dam.
The Thomson is still less than 40% full (with space for 655 billion litres) so we will continue to let it rest while the city is supplied by other parts of the system.
What does this graph show?
With smaller dams full or filling, any significant increases in winter/spring 2011 depend on what happens over the Thomson dam, which is just under 40% full.
Bureau of Meteorology climate modelling shows that the 2010-11 La Nina weather pattern – a key factor in recent unseasonal rainfall – has ended, with a return to neutral conditions in winter.
Autumn water consumption across all uses (homes, business and industry) was 1.8% lower, or 18 million litres a day less, than the same period in 2010.
Impact of Autumn 2011 on storage levels
- Storages rose from 54.2% to 54.5% during autumn – a net gain of 6.9 billion litres.
- The catchments received 288.4mm of rain – which is 31% above the 30-year average.
- A total of 106.9 billion litres flowed into Melbourne’s four major dams on the back of this rain, which is 117.3% above average.
To view previous State of the Storages reports see:
More information
- Factsheets:
- Thomson Dam Cam
- Interactive system map