Ian McIntosh and Derek Williams: Clearer flow of water facts please

Recent talking points and letters from Messrs Maxwell and Palmer of the Hawke's Bay Regional Council have been about the difficulties of controlling "water bottling", as distinct from preventing aquifer water from being extracted and exported, which is really what people in Hawke's Bay are concerned about. More specifically, they are concerned about summertime extraction, when local councils are urging us to reduce our consumption to conserve supply, while not requiring the water exporters to do the same.

Their statement about the Resource Management Act is that "RMA is our most powerful tool. It also stops public authorities from restricting access to natural resources, unless supported by strong science and planning processes". They add, as part of the same statement: "... this gives the community a say in decision-making", which is certainly not what happened in the case of the water exporters. Their consent applications were processed without any public consultation.

The reference to "strong science" is also worth further examination. They concede that some parts of the aquifer (unconfined and semiconfined) were at risk, so they now have interim allocations and consents and these are managed to ensure these are not exceeded. There are also parts (confined) that currently do not have an allocation as there is no evidence of the aquifer being under stress.

The 2009 study they quote shows marked drops in aquifer levels in summer, up to 3m in some areas, requiring the use of pumps to extract water from bores that flowed freely in winter, and accompanying exhortations from the councils to restrict water use. Isn't that strong evidence of "stress"? Another problem we face is that the "science" being quoted is often actually computer modelling. The assumptions made in order to simplify the model may not actually reflect reality.

Further evidence of the problems with Mr Maxwell's "science" are illustrated by some of the council's own papers. The paper Heretaunga Plains Groundwater put before the Council on August 26, 2015, says:

- One of the primary issues that has generated interest in this matter from a broader community perspective is a view that the Heretaunga Plains aquifer is being managed unsustainably and consents are being granted in the face of evidence that the aquifer is under pressure. Staff are clear that this is not the case.

- Monitoring across the confined part of the aquifer suggest that most groundwater levels have remained similar for approximately 150 years. The monitoring shows that the aquifer is not under "stress" in the confined part. This suggests that council does not need to take any immediate action. No supporting evidence is given.

In contrast, the paper Overview of water allocation Prepared for MfE (Report 4375/1, April 2000) says: "Monitoring of Heretaunga Plains groundwater levels over the last 20 years indicates a slow decline of 5cm per year (for a 130m thick aquifer)." That is a 1m drop.

The paper describing the development of the "steady State Computer Model" for the aquifer, on 14/08/2006, says in the final paragraph of the Abstract

"The calibrated Steady State Model can be used to predict the effects for different pumping scenarios. Simulation suggests that water levels have declined about 2m across the Heretaunga groundwater basin since ground-water pumping began in the early 1900s."

Dravid and Brown, noted in their book on the aquifer, Heretaunga Plains Aquifer Study, Book 1 1997, that sea water intrusion in the Bay View/Eskdale and Haumoana/Clifton areas had forced the closure of bores in those areas. It was also pointed out that problems with maintaining flows from bores on the fringes of the aquifer were a sign that the aquifer was under stress.

Messrs Maxwell and Palmer in their own piece point out that it is possible to impose allocations without getting into conflict with the RMA. All you need is some "strong science and planning". The examples above could help.

Of course, staff turnover at the Regional Council, and the high workload may mean that some staff are not familiar with the work of their predecessors. For that reason alone, members of the community deserve to have more notice taken of their submissions to annual planning processes and not receive cavalier treatment. We are sure councillors would also appreciate some more accurate, or at least balanced, scientific input.

- Ian McIntosh is a retired science teacher.

- Derek Williams is a UK structural brickwork and drainage expert.

- Business and civic leaders, organisers, experts in their field and interest groups can contribute opinions. The views expressed here are the writer's personal opinion, and not the newspaper's. Email: editor@hbtoday.co.nz