The Ruataniwha dam and irrigation scheme would provide a $4 billion boost to the local economy and create 2500 jobs, according to a business case to be considered by Hawke's Bay Regional Council this week.
The $265 million water storage scheme, proposed for Central Hawke's Bay, is being promoted by the regional council's commercial arm, Hawke's Bay Regional Investment Company Ltd (HBRIC).
The water storage scheme has been the subject of much debate in Hawke's Bay with some groups calling for it to be shelved because of the potential for economic and environmental problems.
HBRIC's 75-page business case, setting out its proposal for the council to invest up to $80 million of ratepayer money in the irrigation scheme, will be discussed by councillors at a meeting on Wednesday.
"As farms convert over time to scheme irrigation and increase production from changing land uses, the region will have a sustained increase in GDP in farming and processing activities of $250m per year," the plan says.
This would lead to a total "net present value" economic benefit of $3,700 million. Regional GDP would increase by a further $410 million through the one-off impact of the construction of the scheme.
The plan says 2500 fulltime equivalent jobs will be created from farm and farm support work, and potential downstream processing and processing support. The scheme would also deliver millions of dollars in additional environmental benefits by improving water flows down the Waipawa and Tukituki Rivers, it says.
The plan outlines a number of conditions that need to be met before the scheme could proceed. These include a set of "workable" resource consents being granted by the board of inquiry convened last year to consider the environmental impact of the project. The board is due to produce a draft set of consents by the middle of next month.
The project also requires Central Hawke's Bay land users to sign contracts committing them to take at least 40 million cubic metres of water before it proceeds.
Funding from other investors, including the government agency Crown Irrigation Investments Ltd, also needs to be confirmed.
The business plan reveals local Maori are likely to become shareholders in the project. It says He Toa Takitini, the organisation negotiating Treaty of Waitangi claims covering the region's Tamatea and Heretaunga districts, has expressed interest in taking an equity stake in the scheme as part of its upcoming settlement with the Crown.
"The structure and quantum of investment is unknown as treaty negotiations are currently in progress," the business plan says.
This week's discussion on the business plan is one of a number of steps to be taken over the next three months before regional councillors vote on the Ruataniwha project. Next month the council will consider an independent peer review of the business case, being prepared by consultancy firm Deloitte.
In May, it will hold a series of public meetings across the region, and hearings in June. Councillors are due to vote on whether to proceed with the project on June 25.