Reliance on the Gnangara groundwater system for Perth’s public water supply will be significantly reduced ahead of schedule this year due to a combination of good rains and sound management decisions, Water Minister Graham Jacobs said today.
Dr Jacobs said the draw on the mound for the 2009-10 year would be cut by 27 gigalitres (GL) from last year’s draw of 137GL.
“The ability for Water Corporation to reduce their abstraction from Gnangara was welcome news to the State Government and the community,” he said.
“The high dam levels have meant we do not need to fall back on Gnangara as we have had to in some previous years due to low rainfall and reduced catchment inflows.
“The new figure of 110GL brings the annual draw towards the recommended volumes to ensure the long term sustainability of the major contributor to Perth’s high quality scheme water.
“There is no question that the Gnangara system in particular is under stress because of the drying climate and it has always been the intention of the Department of Water and the Water Corporation to reduce drinking water abstraction by a significant amount when possible.
“This year our dams, while still only about 54 per cent full overall, are at their highest level for 10 years which leaves us in a position where we need to draw a lot less water from Gnangara.
“The savings made to scheme water use by this year’s trial winter sprinkler ban have also had a considerable effect on the amount of water available.”
The Gnangara system sits below Perth’s northern suburbs and its water is abstracted to the Integrated Water Supply System (IWSS) to feed high quality drinking water to greater Perth and the Goldfields.
The annual draw on Gnangara historically provides 60 per cent of this water with the State’s first desalination plant reducing that to 50 per cent in recent years.
Average abstraction in recent years has ranged from more than 158GL to a low of approximately 130GL, with an additional average of 10GL per annum coming from the Jandakot mound area in the south.
The Minister sounded a note of caution about the reductions.
“While it is extremely positive that drinking water abstraction will be well down in the 2009-10 year, the position could easily change if the 2010 winter is very dry or consumption levels unexpectedly increase,” he said.
“Several factors have combined for us to reach the position our dams are in right now.
“These include improved efficiency in lowering consumption − in particular the impact of the trial winter sprinkler ban - and the good rains that have been harnessed by the improvements to the dam catchment areas.
“The community deserves credit for supporting the winter sprinkler ban and keeping water consumption to a minimum even after the ban was lifted at the end of August.”
“Sustainable abstraction from the Gnangara system remains a high priority as it is essential to greater Perth’s water needs.”
Minister's office - 9213 6900