Central Hawke's Bay farming companies want 15 million cubic metres of groundwater a year, but can they convince the public?

Ongaonga Stream all dried up in 2020. It will be one of the water bodies augmented if the Tranche 2 applications are successful. Photo / NZME

Eight farming groups which want to use 15 million cubic metres of Central Hawke's Bay groundwater a year face a crucial few months as they try to convince the public and council to allow it.

Nearly seven years after the earliest applications for Hawke's Bay Regional Council's Tranche 2 groundwater take from the Ruataniwha basin, public submissions on the consents have now opened up.

Duncan Abernethy, from I & P Farming, has been appointed the spokesman for the group of eight.

Abernethy said reliable water supply was key to the production and resilience of farms in the Hawke's Bay region ,which was prone to drought and river-quality issues.

"Tranche 2 irrigation water should help to improve the consistency of crop production and confidence in the agri-sector. A positive impact is expected to be seen on local businesses and the communities these support," Abernethy said.

Tranche 2 was first added to the Hawke's Bay Regional Resource Management Plan in 2015, with the stipulation that a consent holder must augment river flow to maintain it above a minimum level while taking groundwater.

Augmentation involves discharging part of the groundwater allocation into nearby bores, rivers or streams via pipes with small structures at the end to prevent erosion, so that minimum river flow during drier seasons is maintained.

The group of applicants said in a statement that it was decided just over a third of the 15 million cubic metre allocation would be used for augmentation after collective environmental assessments. 1 cubic metre is the equivalent of 1000 litres of water.

One of Plantation Road Dairies irrigation sites along Waipawa River in 2018, the river will be one of the water-bodies augmented if the applications are successful. Photo / NZME

Out of 703 existing wells in the Ruataniwha Basin, an application report by consultancy firms Sage Planning, Bay Geological Services Limited and Aqualinc published in August found only four may be adversely affected by the groundwater take. It concluded that any other potential adverse environmental effects of the proposed groundwater takes would be negligible or minor.

Abernethy said the models show a maximum decrease of 0.3-0.8m in the groundwater level during the growing season, which does not result in a permanent drop.

"These aquifers get replenished by the water that flows into the basin each year. HBRC have protections in place for local bore users - any Tranche 2 bore drilled will need to go through the existing testing regime for local bore interference," he said.

Abernethy sees huge benefits in allowing the take, but it will be a challenge to convince everyone.

Forest and Bird Freshwater Conservation Advocate Annabeth Cohen said there has already been a decade-long trend of groundwater levels dropping in the Ruataniwha basin - on average by 1.5m over 10 years across the area, she said.

"Not one more drop should be allocated. Climate change means we need to save our groundwater reserves. The council needs to decline these consents," Cohen said.

She said climate change made the applicants' models of future water regeneration potentially unreliable and argued that augmentation would not be enough to offset the environmental impact of taking more groundwater.

"The majority of groundwater recharge (90%) comes from rainfall, and the remainder comes from stream/river losses (10%). This means augmentation may help mitigate the effects of water takes on the main rivers' stems but not provide a benefit to the groundwater itself or springs and spring-fed streams."

Hawke's Bay Regional Council Team Leader Consents Paul Barrett said a hearing will be held for submitters that wish to be heard.

"The hearing should be completed within 75 working days from the close of submissions. The Hearing Panel will hear the evidence and make a decision on the applications. A decision is likely in the first half of next year," he said.

The eight Tranche 2 applicants are Te Awahohonu Forest Trust, Springhill Dairies, Tuki Tuki Awa, Plantation Road Dairies, I & P Farming, Papawai Partnership, Buchanan Trust No. 2 and Purunui Trust.

Public submissions on the application close at 5pm on Friday, December 17.