Fish and Game Otago and the Otago Regional Council are at odds over a West Otago farm grazing cattle in a paddock near a creek.
The ORC investigated the complaint and was happy no rules had been breached but Fish and Game councillors are worried run-off from pugging (mud that forms during grazing) would contaminate Glenshee Creek.
Fish and Game Otago chief executive Niall Watson said the matter was bought up at a council meeting last week and most agreed the farmer had fenced the paddock too close to the creek's edge.
''Staff consider the riparian margins protected by fencing are very thin, especially for a small, steep stream,'' Mr Watson said.
''It could only be a matter of time before the stream is adversely impacted if the current grazing pattern continues, especially with a rain event.
''In our view, if it is not presently a breach, it must be right on the edge.
''Fenced setbacks need to be more conservative to properly buffer streams.''
Regional field officer Morgan Trotter said grazing too close to waterways was a problem, as significant rain could send contaminants like E-coli into the water.
''We just think that the buffer isn't big enough.
''We've got some serious water-quality issues in South Otago. These tributaries are important because they feed into our waterways.''
ORC environmental monitoring and operations director Scott MacLean said it had investigated Fish and Game's complaint and was happy the paddock did not breach any rules.
''At the time of the investigation there was no breach of the [6A water quality] plan.
Where the cows were, were not in the bed of the river.
There was long grass growing [between the fence and the creek].
That was a mitigation factor for sediment.''
The rules did not specify a minimum buffer zone between a fence and a waterway, Mr MacLean said.
There had been another complaint about pugging at a different location at Glenshee Creek recently and the ORC was investigating that, Mr MacLean said.
He could not say if it was on the same farm or who made the complaint.
Federated Farmers Otago dairy chairman Stephen Crawford said as far as he was concerned, if the ORC was happy, that was the end of the matter.
