The recent emergency release of recycled water into Bruce's Creek, Bannockburn, had no adverse impact on the waterway or the Barwon River, an investigation has found.
Barwon Water commissioned an independent aquatic ecology specialist and conducted its own review into the release from the Bannockburn water reclamation plant.
The corporation was forced to discharge about 31 million litres of the Class C water between August and November when the plant's storage lagoon reached capacity. This followed heavy rain in 2010 and 2011, which cut demand for the water during the peak irrigation season.
Class C water is suitable for crop irrigation and sporting facilities.
The plant's major customer is the Bannockburn Golf Club while Barwon Water also uses the recycled water on an on-site tree plantation.
Water Systems General Manager Carl Bicknell today described the emergency discharge as a last resort.
"Significant rainfall occurred at a time when we would have expected to be supplying customers. Because there was no demand with dams full and irrigation areas saturated, the large storage lagoon was approaching capacity.
"Therefore, based on storage level predictions and no foreseeable opportunity to provide the recycled water to existing users, Barwon Water sought approval from the Environment Protection Authority for emergency discharge," he said.
Several discharge options were reviewed by the water corporation in consultation with the EPA, with nearby Bruce's Creek identified as the most suitable location.
The creek connects to the Barwon River nine kilometres downstream.
Mr Bicknell said monitoring upstream and downstream of the Barwon showed "no detectable impact on water quality" during the discharge over 45 days of an allowable 120 days.
"Based on all the available information, we are confident the discharge has not caused any long-term interference to the beneficial use of the river," Mr Bicknell said.
A detailed risk assessment of the Barwon by the aquatic ecologist concluded there was "negligible or low risk" to the river's beneficial use. But the specialist did note the river regularly exceeded water quality standards for salinity and nutrients because of sediment, stormwater and run-off.
Similarly, a risk assessment of Bruce's Creek indicated "negligible or low" potential impact on the beneficial uses and values of Bruce's Creek. The exception was the possibility for deteriorating water quality in remnant pools if there was no significant rainfall after the emergency discharge.
However, this risk did not eventuate, with significant rain falling following the discharge, Mr Bicknell said.
He said the exercise had highlighted the need to improve inter-action with local interest groups, develop management plans for all inland water reclamation plants for possible similar emergencies and seek further information on water quality in waterways around these plants.
"Overall, this was an excellent outcome after every other option had been exhausted," Mr Bicknell said.
A major upgrade of the Bannockburn plant expected to be completed mid-2012 would not only ease pressure on the facility's capacity but would cater for future growth in the township, he added.
A detailed report on the findings can be viewed at www.barwonwater.vic.gov.au