The Ruataniwha dam and water storage scheme appears to have become a "feasible proposition" under a final board of inquiry decision released yesterday, says Irrigation New Zealand.
But other key supporters of the dam - including its financial backer, Hawke's Bay Regional Council - say they need time to review the decision before commenting.
The council and Irrigation NZ were among those to voice concerns about the board's draft decision, released in April, which placed strict nitrogen leaching limits on farmers in the Tukituki catchment as part of an environmental plan change.
It was feared the limits would restrict farming in the catchment and therefore make the Ruataniwha scheme unviable.
But in its final decision - released after it reviewed submissions on the draft - the board has corrected an "error" around how nitrate levels will be applied to individual farms.
"This decision indicatively shows us that common sense has prevailed," Irrigation NZ chief executive Andrew Curtis said.
"The Ruataniwha dam will be of huge benefit to the Hawke's Bay community and this looks like a positive step for New Zealand in future proofing its access to water and its socio-economic development."
The board of inquiry's final decision was also welcomed by the Environmental Defence Society, which opposes the dam.
EDS chairman Gary Taylor said the society was still assessing the implications of the changes the board had made to the way nitrogen would be measured but the future of the dam was "questionable".
"The risks of proceeding are high now that water quality must be maintained or improved in the Tukituki River," he said.
"This decision is a big win for the Tukituki catchment and also has wider implications for the management of freshwater quality elsewhere in the country."
Hawke's Bay Regional Council and its investment arm, Hawke's Bay Regional Investment Company (HBRIC), said it would be "some days before they can make informed comment" on the board's decision, which runs to several hundred pages.
HBRIC chief executive Andrew Newman had previously said the draft decision would need to change for the project to proceed and council chairman Fenton Wilson said Central Hawke's Bay faced a bleak economic future if it was not changed.
Federated Farmers, another critic of the draft report, said it also needed time to digest the final version.
The board's final decision leaves unchanged a key river nutrient indicator of 0.8mg of dissolved inorganic nitrogen (DIN) per litre which the board said was "a pragmatic limit that appropriately protects ecological health enabling more intensive land use".
However, individual farms will not have to observe the DIN limit although they will have to comply with leaching rates for nitrogen based on the Land Use Capability Classification System.
How our readers responded on Facebook
The Hawke's Bay Regional Council voted 6-3 this week in favour of investing $80 million of ratepayers money into the Ruataniwha Water Storage Scheme. We asked our readers on Facebook what they thought.
Danton William Smith: I think no because if it floods or breaks in the event of disaster it will probably kill a whole bunch of people.
Casey Mikaera: I think yes, most definitely yes.
Te Atakura Mokotupu: No.
Kel Hohaia: The council will always do what they want anyway, regardless of what the public opinion is.
Terry Bill: The regional council is not to fund bloody dams - that is not their job. Oh, that's right, they are not even doing their job properly re pollution in waterways.
Chantelle Roper: I think we just lost another river to pollution. The council needs a shake-up. I think people more concerned about money than the environment should have to pay to clean it up.
Tracey and Paul Gattsche: Wonderful news for CHB! Exciting time - now we will survive.
Jared Mulinder: @chantelle, how does this increase pollution again?
Daniel Hansen: Great news! Now it's time to do the same for the Heretaunga Plains.
Jill Loye: Another excuse to put rates up.
Annabelle Greer: Bloody marvellous! This is going to be the future of our kids.
Bon Mahu: Great news.
Brian Peter Drury: Great decision, eventually leading to more investment in more highly mechanised, efficient, larger farms requiring far less labour and enabling more profit to go out of the area to the new owners, foreign investors. A win for everyone except, of course, the people of Central Hawke's Bay who will end up destitute. A win-win for everyone who counts.
Ben Walch: Yes! Thank God our predecessors were not as anti-progress as many of this generation. We would be still in caves.
Shontae Ngahuka: This costs $80 million. Ratepayers and Bay people will pay the price if it goes through and for what? To better feed wineries and orchards - they have irrigation.
Phil Tasker-Poland: It's shameless politics in action once again ... dollar politics for the chosen few.
Alex Walker: Great decision for progress for the whole of Hawke's Bay.
Jeni Gilbert-Cox: We have no choice if we want a future and prosperity for Hawke's Bay. There is no question that in order for this region to prosper, we must store water. It has been done successfully elsewhere in NZ. The dam projects I have seen are glorious feats of engineering and the newly created "lakes" and surrounds are beautiful. There is no reason why we cannot achieve the desired outcomes - economically and environmentally.
Jeni Gilbert-Cox: And for those people above who say it is not the regional council's job to build dams, water storage is certainly part of their mandate.
Paul 'n' Shona Sunley: How does this help my family prosper here in Hastings, precisely? We barely see the benefits of our rate money as it is, so how is this going to be beneficial to anyone other than farmers and the like in Central Hawke's Bay? Am just interested in how this will benefit the whole Hawke's Bay region.
Alastair Scott, National Party Candidate for Wairarapa: @ Paul 'n' Shona Sunley - irrigated land produces more stuff. It might be crops, meat or dairy. More stuff will create jobs in the area, processing and transporting the stuff to Napier Port. More exports - economic good news. The dam will also allow for minimum flows, enabling bores to be retired, allowing aquifers to regenerate. The dam will have consents and water standards to be met which are set by the community. The water quality will improve. Non-compliant, "dirty" farmers will have the tap turned off.