Head of the Tamar Lake Inc consortium, retired Launceston engineer Robin Frith, said they needed $100,000 for the next level of research into the barrage.

The plan is to construct it across a narrow neck of water on the Tamar Estuary at Point Rapid, just south of the deep water port at Long Reach.

Mr Frith said the $100,000 would pay for a three-dimensional modelling analysis on the rate of silt accumulation downstream from the proposed barrage by international environmental consultants BMT WBM.

It would also cover the cost of a $25,000 geological study of the estuary.

BMT WBM had advised the three-dimensional study should be done, Mr Frith said.

''And we think it's necessary because people continue to ask what will happen below the barrage,'' he said. ''We believe that the information is there but it's not backed up by any detailed analysis.

''We don't want to leave open an opportunity for a political party of any colour to distort the facts . . . like a claim of a $1 billion construction cost for the barrage, or that the silt deposits below the barrage would close down the Bell Bay port.''

Mr Frith said the consortium of 23 businesspeople who had backed his push for a detailed investigation into the feasibility of the barrage had raised $75,000 towards costs so far.

''The ideal situation from a Tamar Lake Inc viewpoint would be for the government of the day to provide a grant sufficient to pay for the development of the three-dimensional model, apply that model to the siltation below the barrage issue and pay for the barrage costing project,'' he said.

''The government would then have access to the 3D-modelling tools for any other study project.''

Mr Frith is convinced the barrage would generate economic wealth in the region and solve the problem of silting in the upper Tamar basin. 

A pre-feasibility study publicly released earlier this month was compiled by Mr Frith from more than 15 reports on Tamar siltation, flood mitigation, barrages in other countries and hydrodynamic modelling of the estuary and river catchments, including several existing report updates by BMT WBM.

It showed the barrage would create a 60-kilometre freshwater lake from Point Rapid upstream to Launceston.

Mr Frith said a barrage much further downstream would be the basis for a major economic transformation of the Tamar Valley that would more than justify the $200 million capital cost.

Mr Frith said he would stay with the campaign he started more than two years ago to investigate the feasibility of building the barrage until somebody else picked it up.

He said he believed it was the only long-term solution to the silt problem in the Tamar basin.