The host of The Country, Jamie MacKay, promoted it as "The Great Water Quality Debate". He introduced the two protagonists using political nomenclature: Professor Jacqueline Rowarth, (Waikato University) in the blue corner and Dr Mike Joy (Massey University) in the red corner. It was and still is riveting listening.

The discussion started with the Havelock North drinking water fiasco. The initial question was: Is dairying to blame? Rowarth was considered and measured. The matter is still under investigation but here are some possibilities, other than dairying, as to the possible cause. Joy responded somewhat defensively with a clarification - he said that intensive farming was the cause, not dairying. Rather a moot point I would have thought, a trick used most frequently by politicians.

He then painted a picture; feed-pads, mob-stocked, big slushy pools of urine and faeces, easy obvious pathway for that material, not just one or two sheep but hundreds and hundred and thousands of cows, so I think on the balance of probability that would have to be right up there. (The implication was that the cows are the obvious source of the contamination in the Havelock North aquifer)

In contrast to Rowarth's rational approach, Joy was being emotional. Rather than the blue and red branding offered by MacKay I think the correct categories are science versus alarmism.

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There were other examples of this contrast. Joy's suggestion that there have been "many outbreaks in intensively farmed areas" was reduced by Rowarth to two instances of water- borne outbreaks of campylobacter, one in Havelock North in 1998 and the other in Darfield in 2011.

From the ensuing discussion I learnt from Rowarth that most cases of campylobacter arise not from contaminated drinking water but from improperly cooked food. Joy added the numbers from ESR for 2014; 1900 cases from faecal contact and 2092 from recreational contact. There is no data for drinking water!

And so back to the topic of debate. Is dairying the cause of the problem in the drinking water in Havelock North? Rowarth asserted that the aquifers were known to be 'clean' and that the source was likely to be, as was the case in Darfield, an improperly sealed bore.

My understanding is that when this happens, surface water, which could well be contaminated, is drawn into the drinking water. Joy persisted with his view that the aquifer was the source of the problem - a necessary requirement for his general argument, that intensive farming is the problem, to persist . He added later in the discussion "water does not magically appear in the ground water, it comes from the land to get to the ground water - that is the connection there." This suggests that he misunderstood Rowarth's point about improperly sealed bores.

According to the transcript, Joy's solution to this problem is to get animals out of the food chain by 2050, which he then modified to say that, at present, we need to fence waterways to exclude animals. MacKay responded, quite correctly, that this was being done and laid down the challenge afresh: "Are you serious about riding the food chain of animals by 2050 - New Zealand would go broke?" "No they wouldn't" responded Joy "because we are gonna have to change - the whole planet has to change, the sums just do not work - you cannot feed 9 billion people which is expected by then if you have animals in there ..." Now that is not Science-speak - that is pure Green Alarmist speak.

The debate included a comparison with other countries - how do they get clean drinking water. Rowarth explained that they chlorinate the water and use new treatments such as ozone and ultraviolet light, helpfully suggesting that we should be exploring these possibilities.

Joy objected to making comparisons with other countries. In his view the "rest of the world is going to hell in a hand-basket environmentally." Once again his rhetoric is that of an activist not a scientist.

Earlier in the debate Joy had dismissed chlorination of drinking water with the throw away, and churlish suggestion, why not chlorinate the rivers! He believes that such an approach would be putting the ambulance at the bottom of the cliff and not dealing with the issue. However, if Rowarth is right in suggested that incorrectly sealed bores are the source of the drinking water problem, then it is likely that such accidents will happen again, and that chlorinating the drinking water or UV or ozone treatment, is a sensible precaution against such malfunctions.

My reason for writing this column about this debate is hopefully to assist the lay person as they wrestle with the question: the participants are both scientists so who should I believe?

Roger Pielte wrote a book about science and the role of science in informing public policy (The Honest Broker, Cambridge University Press, 2007). He drew particular attention to the difference between a scientist acting as an Honest Broker, who proceeds on the basis of the evidence, impartial as the political or social issue being addressed, and one who acts as an Advocate for an issue, bringing to it only the supportive evidence.

The Advocate becomes an agent of what is now formally known as "Post Normal Science." The role of science is not about a search for truth - the role of science now is to support the issue - the politically correct narrative.