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New data strengthens pipeline

1 May 2012

Orange residents would have been spared harsh water restrictions and Suma Park Dam would have remained at more than 50 per cent if the Macquarie Pipeline was available through the recent drought.


Macquarie River

This was one of the major findings during the development of the Environmental Assessment for the project. Expert consultants have provided more data strengthening the case for the Macquarie River to Orange Pipeline Project. The new findings have come to light in long term modeling produced for a Hydrology and Water Security Assessment by consultants Geolyse.

Orange Mayor John Davis said there was still work to do and the Macquarie Pipeline Project was yet to be assessed by the State Government, however the latest figures were encouraging.

“While some people have believed there have been little or no flows in the Macquarie River for much of the last decade the actual data tells a very different story. And what that data reveals is that even when the region was in drought the Macquarie Pipeline would have delivered water security to the city with minimal impact on the river,” Cr Davis said.

“At their worst Orange’s dams were at 23 per cent of capacity in May 2010. If we had the pipeline operational during that dry period from 1999 to 2010 the dams would have been at 63 per cent in May 2010. The pipeline will sustain Orange through drought and deliver water security to this city for the next 50 years.”

Suma Park, April 2009
The dry bed of Suma Park Dam in April 2009

The modeled annual average extraction between 1999 and 2010 was 1.4 per cent.

The latest investigation has found that there is more water flowing down the river than first estimated. As a result of the new data, Council has raised the trigger point for when pumping can commence from 30 to 34 megalitres, modified the level of extraction and amended the water security projection.

“The new data is the result of water modeling across more than 100 years and demonstrates the project is viable,” Cr Davis said.

The modeling found that lows flows, flows below 22 megalitres a day as determined by the NSW Office of Water guidelines, occur 20 per cent of the time. The Macquarie Pipeline will not operate during these times. 

On average, 300,000 megalitres a year flows past the proposed off take point. The pipeline’s long term average extraction is 1665 megalitres or 0.54 per cent of flows. This will improve the city’s secure yield by 2800 megalitres, double that first estimated. The pipeline’s peak demand has been capped at 12 megalitres a day.

On a day when the 34 megalitre trigger is reached and peak extraction of 12 megalitres occurs, the water level in the river would fall by 19mm. For 50 per cent of the time flows exceed 110 megalitres a day.

The State Government access rules for town water supplies do not contain cease to pump thresholds or triggers, which means Orange City Council is going beyond the requirements of the Draft Water Sharing Plan for the Macquarie Bogan Unregulated and Alluvial Water Sources by committing to a 34 megalitre trigger.

The latest assessment also found that the downstream impact of the Macquarie Pipeline would be negligible. For example the pipeline operations would equate to 0.16 per cent reduction of inflows into Burrendong Dam.

The Hydrology and Water Security Assessment is a key component of the Environmental Assessment. It will be forwarded to the Department of Planning for an adequacy assessment and then released to the public.