Hunter Downs Water said it was "continuing to work through alternative funding options for the scheme".
Dr Rolleston said it was "extremely generous and community-minded" of Mr Rooney to put $18.5 million of his money on the line for the venture. But there was another way to fund the scheme that would avoid relinquishing ownership.
"We want to have this 100% farmer-owned. We want to have control. Any outside party involved needs to make money," Dr Rolleston said.
He recommended "dry" shares in Hunter Downs Water — bought as an investment, but which did not deliver irrigation water to the owner's land — be held by those who owned the "wet" shares.
"In the next few months, there will be a vote to set the structure in place," Dr Rolleston said.
"There's an opportunity to buy wet and dry shares.
"If you think you might want wet shares in the future, come and see me and we'll look at dry shares. They will give you added value on your property and equity in the company.
"If we don't sort this before the vote, you'll have a joint venture, not farmer-owned."
Dr Rolleston said there was a very good chance the proposal could secure funding from a lending institution.
If the irrigation scheme supplemented the Wainono Lagoon, it would allow farmers to continue current stock numbers and practices while providing wider environmental benefits that could make it eligible for the Government's regional development fund.
It was also in both the Waimate and Timaru District Councils' interest to make the scheme work, he said.
Timaru was "taking water from the top of one of the most water-depleted catchments in New Zealand".
sally.brooker@alliedpress.co.nz
Central Rural Life