Concerns are growing about the impact requests to take another 15 million cubic metres of groundwater from the Ruataniwha Plains will have on the environment and the availability of water for CHB towns.

Between 2014 and 2017, eight applicants, including major dairy operations, applied to the regional council to collectively extract 17 million m3 of 'tranche 2' groundwater from the Ruataniwha Basin.

The Board of Inquiry into Tukituki Plan Change 6 determined that an additional 15 million m3 a year of 'tranche 2' groundwater could be extracted as a discretionary activity if the adverse environmental effects could be mitigated by river flow augmentation.

As such, any tranche 2 groundwater consent holder would be required to release up to 40 per cent of the water they take into rivers and streams at times of low flows.

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The regional council's investment arm, HBRIC Ltd, the company promoting the dam and the Ruataniwha Water Storage Scheme (RWSS), had a claim to 10 million m3 of tranche 2 groundwater but withdrew its application last October, leaving the eight remaining applications.

These applications were on hold, awaiting more details on the augmentation schemes, but in the meantime CHB farmer Alistair Setter had written to the regional council chief executive and councillors calling for the consents to be publicly notified, or better still terminated, amid fears of the environmental and social consequences.

Backed by other residents, farmers and Forest and Bird, he said the ramifications were wide ranging if the consents went ahead.

"Many farmers and businesses that use stream depleting bores are facing the prospect of reduced water availability in the coming years, due to the minimum flows in the Waipawa and Tukituki Rivers being increased.

"CHB townships use water from stream depleting sources — while they can take water during ban periods for human welfare, it means strict community water restrictions."

He noted that at his property at Swamp Rd, springs and waterways that had never before stopped running had done so twice in the last two years, and that many Ongaonga residents had been forced to re-drill and lower their bores at the time the larger irrigators started in the area in 2004/2005.

His concerns were echoed by CHB councillor Tim Chote who said the situation had gone under the radar.

"We have to stand up — I'm worried for the ratepayers and the possibility you could all of a sudden get water restrictions — we have to know what's going to happen with this."

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Tikokino farmer George Williams said he was concerned about any increased take from the aquifer.

"That is going totally against what the regional council has stood up for since the moratorium was put on any further allocations — to turn take another 15 million cubic metres, even though some would be put back in the river, is going to affect everyone."

CHB farmer and former CHB mayor and regional councillor Tim Gilbertson said if concerned local people had not raised the alarm about the consenting process no one would have been aware that eight people could enjoy a massive benefit at the expense of the rest of the district.

"If council has 15 to 20 million cubic metres in its own back pocket, it's money in the bank to encourage or apply new and exciting, profitable, high value, low input crops like hemp, rather than low value, high input enterprises such as dairy farming," he added.

He also noted that all the information was based on a model.

"Fifteen years ago we were told there was no connection between irrigation and the depletion of Ongaonga's water — there's no guarantee that the model they are using now was any better than others used over the years."

For Ongaonga resident Bill Stevenson, who had to put a new submersible pump into his well to access diminishing groundwater, the thought that there could be additional extraction was a worry.

"We've been dealing with dropping water levels for 14 years. In my opinion any further groundwater extraction has to be stopped."

Peter Kittow farms on the outskirts of Waipawa and said he could not understand why these consents were even being contemplated in the face of the evidence that the groundwater levels were dropping.

"If the rivers are being depleted there needs to be a step back. Any more irrigation consents should be terminated until the controlling bodies have a greater understanding of what that uptake means for the future."

Gaining that understanding was part of a process that was under way in considering the tranche 2 water take applications, said Hawke's Bay Regional Council chief executive James Palmer.

He said the issue arose from the Plan Change 6 Board of Inquiry (BOI) process, when the Ruataniwha Dam was pitched as being part of the solution to manage over-allocation of water on the plains.

During development of the plan change a number of irrigators disputed the science, he said.

"They said there's deep water below that's not being captured by council science and that they should be able to take that water.

"The council disputed that but in the closing stages of the BOI process the board decided it would throw a bone to those concerns and said there could be an allocation of an extra 15 million cubic metres as long as it was offset by augmentation either from storage or a proportion of the ground water take."

He said the council was uneasy about this as it seemed to be "robbing Peter to pay Paul".

"The council view was that it could be done sustainably by offsetting the groundwater take with equal water stored above ground — that would only have been feasible if the dam had gone ahead."

He said the dam was a crucial factor in the sustainability of the water resource, which was why HBRIC put in its application for the entire 15 million cubic metres, later wound back to 10 million cubic metres.

"In the intervening period everything was put on hold subject to the dam proceeding and no consents were processed.

"When the dam fell over those water consents came up the cue and reignited the issue — we now have to do more science to see how to mitigate the flows on the surface — 40 per cent of ground water taken at any one time would need to be put back in river to manage the effects in the short term but that does not solve the long term issue.

"The council's preference would have been to have never had this tranche 2 water but now we have a legal obligation under the plan to give these applications due consideration — it would be a hard process to terminate."

Any changes to Plan Change 6 would have to go through a comprehensive process which would cost several hundred thousand dollars and take nine to 12 months, with the possibility of future appeals.

"It's an invidious position to be in for the council and community — our current position is that we will not be processing any consents until we have more science," he said, adding there was at least two more months of work.

Regional council chairman Rex Graham said the concerns raised seemed plausible, but he wanted to understand the science better.

"... We could grant the consents, we could publicly notify them, we could terminate them, but we need to know more to do the right thing."