Farmers need to ensure stock are empty before transporting them, says Environment Canterbury commissioner Tom Lambie.
He said Ecan preferred not to prosecute, and wanted people to be "doing the right thing" in the first place.
The Lower Waitaki South Coastal Canterbury zone committee meeting in Waimate last Wednesday heard that Ecan received more than 5000 complaints last year through its pollution hotline.
These included a complaint of cattle effluent on a bridge near a domestic water intake.
Area leader (South) for Ecan's RMA monitoring and compliance unit, Jo Field, said the farmer involved hadn't been located.
There had been a significant amount of effluent, and it would have washed into the waterway in the next rain event.
Lambie said farmers had to move stock around, but also had to plan ahead and think about the consequences.
"What a farmer can do when transporting any stock is to stand them for a while and empty them out. We still need to move stock but we need to be aware of the consequences of what we do."
Field said Ecan's investigations unit considered various criteria when deciding how to handle pollution incidents.
These included whether the person was a repeat offender, the magnitude of the offence and the level of environmental harm.
Prosecution could occur "when everything else is deemed to have failed", she said.
She emphasised the need for people phoning Ecan's pollution hotline to be prepared to give their name and contact details.
She said people could be assured this information would be protected and would not be disclosed. It was needed so that investigators could follow up and gather more evidence.
The only time people would be asked to be identified would be if a case went to court and the person's evidence, such as photographs, was required for prosecution.
Pollution hotline: 0800 765 588.
- Fairfax Media