Farmers are concerned that future releases of "diminished quality" treated water from the Kyneton Water Reclamation Plant may harm their stock, after previous releases coincided with problems with stock.
Kyneton farmer Huntly Barton said he believed previous releases polluted the river, possibly contributing to the death of his stock.
Coliban Water has said there is no sign it will be forced to discharge water of a "diminished quality" in 2019 from the plant.
Coliban Water said it undertook environmental assessments of the effect of its discharges on the Campaspe River, but these do not include assessing the suitability of river water as a source of drinking water for stock.
These assessments were in compliance with its EPA licence, the organisation said.
Coliban Water discharged treated water of diminished quality from the Kyneton Water Reclamation Plant into the Campaspe river in 2016 and 2018.
Mr Barton said he fears Coliban Water may be forced release more water from its pond system that has not been diluted to the ratio required.
"It's polluted our river. In 2016 we lost 15 calves, they were born prem or died within a week," Mr Barton said.
"Up until the last four or five years I've barely lost a calf."
Coliban Water has confirmed it discharged from the Kyneton Water Reclamation Plant into Snipes Creek in 2007, 2010, 2012, 2013, 2014 and 2016. It also confirmed it discharged treated water that did not meet the quality requirements of its licence in 2016 and 2018.
Coliban Water's licence to discharge into Snipes Creek ended in the 2006/07 financial year.
Read more: Sewage 'low risk' despite infractions
Coliban Water executive general manager water quality David Sheehan said Coliban Water "at times" needed to discharge out of its licence requirements when its onsite lagoons were close to full capacity, to protect its infrastructure from failure.
Coliban Water said the Environmental Protection Authority was informed when it made non-compliant discharges.
Coliban Water said it has has budgeted for works to the Kyneton Water Reclamation Plan to make sure it will be compliant with its EPA licence.
Kim Strawhorn farms sheep near the reclamation plant.
He said stock in the two paddocks next to the river have never done as well as others on his property, to the point where he has installed alternative water sources.
"Illegal releases have been happening for over a decade now, it's just ridiculous," Mr Strawhorn said.
"We advise landowners to seek advice from Agriculture Victoria regarding suitability for animals to drink water sourced from the Campapse River," Mr Sheehan said.
The EPA has been contacted for comment.
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