The Hawke's Bay economy could take a $50 million annual hit if environmental changes proposed by the board of inquiry considering the Ruataniwha dam project are confirmed, Hawke's Bay Regional Council says.
Farmers and the council would also face millions of dollars of cost under the changes, it says.
The changes to the Hawke's Bay Regional Resource Management Plan, known as Plan Change 6, set environmental rules and standards for the Tukituki River catchment, the area that would be affected by the Ruataniwha scheme.
The board's draft Plan Change 6 decision, setting strict limits on nutrient levels in the catchment and also setting minimum river flow rates, were welcomed by environmental groups but greeted with concern by the council when they were released last month.
The council said it feared it would have a major economic impact on the area by limiting the scope of farming activity.
Those concerns have been quantified in a report prepared for next week's meeting of the council's regional planning committee.
The report, by the council's group manager of strategic development, Helen Codlin, said the proposed nitrate limits and increased minimum flow limits "could translate into a $50 million ongoing loss in regional GDP [compared to the current situation]".
It said the limits might require 6000ha of productive land in the top half of the catchment to be converted to forestry.
"A preliminary economic analysis undertaken indicates that under the nutrient regulatory regime envisaged by the Draft Decision, on-farm regulatory costs will increase by more than $17 million," the report said.
The council would also be hit with significant additional costs, because the proposed plan change conditions would require a significant number of resource consents to be issued.
"The significant increase in the number of consents required to be processed and monitored represents significant implementation costs for the council. Staff have estimated that an additional seven consent officers would be required over the 2018-2020 period reducing to two additional consent officers on an ongoing basis," the report said. "An additional administration resource would also be required. Staff have estimated that an additional three compliance officers may be required."
The council, along with other organisations involved in the board of inquiry hearing process, have until next Friday to lodge submissions with the board on its draft proposal.
The scope of submissions is limited, however. Submitters cannot challenge the substance of the board's ruling but can address any errors they believe it has made, technical issues related to how the plan change would be implemented, and areas where they believe the board has omitted any aspects it should have considered.