Others had used the episode to have a go at Overseer, claiming councils were relying on it to manage bacterial risk, when the computer programme modelled the flow of nutrients in the root zone of soil, not bacterial flow into underground aquifers.
Photographs in the media last week of beef cattle standing in the Tukituki River failed to mention that the site was downstream from the Havelock North bores.
"Unless the theory of gravity has changed this is unlikely to be the source," Dr Rolleston said.
"It is worth noting that Waipukurau's treated sewage water outflow is in the catchment above the bores, but this somehow doesn't fit the activist agenda.
"There is no question that animals and birds, both wild and on-farm, create an opportunity for pathogens in the environment. So do humans for that matter.
"Councils have a responsibility to assess and mitigate credible risks which exist in the environment when it comes to drinking water.
There has been a systems failure, and 4000 people got sick. The only way to re-establish confidence in the Havelock North water supply is with good factual, science-based evidence gathering.
That's what the councils, the Ministry of Health and the local community are trying to do. Distracting rants about building dams, wandering stock and activist theories do nothing to fix the system faster."