State of the Storages
September 2010
Storages have started spring at their highest levels since December 2006 and are expected to continue to rise as the catchments that feed water to the major reservoirs are wet and typically produce the most runoff at this time of year.
Storages have started spring at 41.3% full after rising by 8.6% of capacity during winter – a net gain of 157 billion litres, the equivalent of about 40% of Melbourne’s yearly water use.
The key reason for the favourable spring outlook is the cumulative effect of consistent rainfall so far this year. The catchments - which act like a sponge, absorbing rain until they allow the water to run into the reservoirs – have had 722mm of rain so far this year. This is slightly above the 30-year average and much higher than recent years.
While the extent of a spring storage boost will depend on the amount of rain, because of the sponge effect the impact of rain on the storage levels will be greater than at any other time of the year.
The table below shows that, for the decade from 2000 to 2009 the average spring storage gain has been 4.3%.
| Year | Change in storage levels (% of capacity) |
|---|---|
| 2009 | 9.5% |
| 2008 | 0.3% |
| 2007 | 1.3% |
| 2006 | -5.1% |
| 2005 | 5% |
| 2004 | 6.1% |
| 2003 | 10.5% |
| 2002 | -0.6% |
| 2001 | 6.9% |
| 2000 | 9.2% |
| Average spring storage increase for 2000-2009 | 4.3% |
The good winter result came as rainfall and runoff were much more in tune with the 30-year average than in recent years. August was particularly wet – rainfall (166.2 mm) was 45.1% above average, and runoff (101.1 billion litres) was 25.3% above average.
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Here’s a snapshot of how storages are performing:
Impact of winter on storage levels
- Storages rose by 8.6% of their total capacity from 1 June to 31 August, from 32.7% to 41.3%. This compares with a rise of just 2% in the same period last year.
- The major catchments received 316.6mm or 3.5% below the 30-year average rainfall.
- A total of 177 billion litres flowed into Melbourne’s four major dams on the back of this rain, which was above the average by 0.2%.
- Melbourne’s total water use (households and business) dropped by 1.8% compared with the same period last year – a saving of 16.7 million litres a day.
Archive
To view previous State of the Storages reports see:
More information
- Factsheets:
Storages during Winter 2010 (PDF, 73kb)
Storages during August 2010 (PDF, 73kb) - Videos:
Answers to frequently asked questions on storages - Decade in dam levels
- Securing our Water Supply