Kaipara and the Mid North had already been identified as potentially viable locations for larger-scale irrigation initiatives, and the new study looked in more detail at availability of water and likely viability of community water storage facilities.
The $300,000-plus cost of the study - Scoping of Irrigation Scheme Options in Northland - had been jointly met by the regional council and the government. It was available at www.nrc.govt.nz/economicdevelopment
Researched by a consortium of consultants led by Opus over the last nine months, the report found that demand for water was significantly more on a per hectare basis, but varied less seasonally in the Kaipara than the Mid North, where water would be used over a longer period of each irrigation season.
Cr Smart said rainfall, geography and likely demand meant three cheaper and smaller options had been suggested for the Mid North. One, Mid North A, cost about $22 million, and could enable irrigation of about 1600ha south of Kaikohe.
Securing a reliable water supply would enable higher value use of land and provide "significant opportunities" within the town and wider community, generating about 500 extra jobs and boosting regional GDP by about $70 million.
The schemes would not come cheap. The capital cost of Mid North A was estimated at more than $11,000 per hectare.
If the focus was solely on farm gate returns paying for the schemes they were unlikely to proceed, the report warned.
Cr Smart said that while growers could not afford to build the schemes alone, given the likely flow-on economic, environmental and other benefits for the wider community there was a potential case for wider investment, including by both central and local government.
"The study acknowledges the potential costs to develop all four schemes in the scoping report, as much as $300 million, would be considerable for Northland alone. With that in mind, it suggests one possible solution could be to establish a special funding body to enable a mix of public, private and iwi investment," she said.
"Initially that entity could be as simple as a community steering group, with participation from all three groups, but it would need to be able to adapt to a more formal structure as and when the development process advanced."
Also recommended were much more comprehensive pre-feasibility studies (down to individual farm level) that would likely cost up to $2 million and take another year to complete. They would also include development of an investment case and benefits model, and would need to encompass detailed environmental impact assessments.
Cr Smart said Northland Inc had already recognised the massive difference improved irrigation could make to the region's future fortunes, ensuring it had been listed as a key project in last year's Tai Tokerau Northland Economic Action Plan.
Regional councillors, yet to come to a firm collective position on irrigation, would review the new information contained in the latest study in more detail over coming weeks.
The council also planned to share the report's findings with district councils, and liaise with them and the government to see what appetite there was to progress.
Even with support, it could still take several more years, and many millions of dollars of design and engineering work, before construction of any actual irrigation schemes finally began.
