Decade in dam levels
It’s official – the past decade was the toughest on record for Melbourne’s dams.
Between 2000-2009 a total of 3,911 billion litres flowed into our main reservoirs. That’s almost a quarter lower than the previous low set during the 1980s (5,033 billion litres).
These figures are based on streamflow data dating back to the 1920s for the Maroondah, O’Shannassy, Upper Yarra and Thomson Reservoirs – including sites where these dams were later built.
Streamflow at major reservoir sites by decade
What this graph shows: A review of the amount of water flowing into Melbourne’s dams shows 2000-2009 was the worst on record for Melbourne’s major reservoirs. It was significantly down on the previous low set during the 1980s.
Rainfall vs. streamflow
The most revealing figures from the past 10 years are these ones: while rainfall was 10% lower than the 1990s, streamflow into reservoirs fell much further down – 33%.
The catchments need to be wet before they can generate runoff into dams – otherwise the moisture soaks into the soil. Long dry periods during the 2000s meant that when it did rain, the catchments were often too dry to generate normal amounts of runoff – and it had a devastating impact on dam levels.
Highs and lows
There were lots of ups-and-downs in between, but storages reached a high of 63.0% in November 2000 and a low of 25.6% in June 2009.
The biggest annual drop in the past 10 years was in 2006, when storages started at 58.4% and fell to 38.9%. It remains our worst single year on record in terms of the amount of water flowing into dams.
The biggest annual increase was in 2003, when storages rose from 51.2% to 56.6%.
Melbourne’s water storages 1990-2009
What this graph shows: Changes in storage levels in the mid-1990s and the 2000s. Dam levels dropped from almost full in 1996 to a quarter full by 2009 along with a steep decline in the amount of water flowing into our major reservoirs.
Water wise
Per capita water use was significantly lower during the past 10 years compared with the 1990s. It continued to drop during the 2000s as restrictions tightened so that by 2009 we used almost 40% less water per person compared with the 1990s.
2009 in review
The last year of the decade was one of extremes.
On the downside:
- one-third of the catchments damaged by Black Saturday bushfires
- dams recorded their second-lowest inflows for any January-June period
- storage levels reached a record low of 25.6%
But on the upside:
- above-average Spring rain for the first time in 12 years
- biggest monthly boost to storages for 17 years (in October)
- lowest per capita consumption since 1917
Across the year catchment rainfall was still below the long-term average and inflows into Melbourne’s major storages totalled 369 billion litres (compared with 287 billion litres in 2008).
Ultimately, storages finished the year higher than they started (from 34.9% to 37.5%). Part of this was due to the reconnection of Tarago Reservoir in June 2009, which adds around 15 billion litres annually to Melbourne’s supplies.
Factsheet – Performance of Melbourne’s Storages 2009 (PDF, 58kb)
More information
Factsheet – Performance of Melbourne’s Storages 2000-2009 (PDF, 59kb)
Factsheet – Performance of Melbourne’s Storages 2009 (PDF, 58kb)
Media release – Toughest decade on record for Melbourne’s dams
Securing Melbourne's Water Supply
Target 155
Videos: How our dams work
Bureau of Meteorology's seasonal outlook