THE $1 billion Mary River Traveston Dam provides the largest water storage at a reasonable cost of all the options considered by a much-anticipated technical report.

Engineering firm GHD’s review of the state’s identified dam and weir sites says the Traveston Dam will store 1.13 billion litres of water and supply 215,340 megalitres a year at an average cost of $4695 for each megalitre it provides.

Of the 15 potential dam sites studied, three alternative options had a lower average cost of water supply to the Traveston proposal – but they provided only a fraction of the water.

Traveston was by far the biggest water storage option and even after reducing the available annual water yield to take account of changing rainfall patterns, it remained the best option to supply the long-term water needs of southeast Queensland.

The proposed Cambroon Dam on the Mary River, the Kidaman Dam on Obi Obi Creek, and various flood harvesting works into a raised Hinze Dam would all provide a bigger bang for the Government’s buck.

But even added together they would provide less than half the potential yield of the completed Traveston project.

The Cambroon and Kidaman dams, as well as another at Amamoor Creek, were favoured by the Opposition.

Damming the Caboolture River at Zillman’s Crossing would be the least cost-effective of the proposals considered by the GHD report, commissioned by the Government’s Bulk Supply Infrastructure Task Group.

The Wyaralong Dam on the Logan River that was announced on Tuesday would provide 26,674 megalitres a year at an average cost of $4790 per megalitre, GHD said.

The Government also yesterday released its preliminary estimates of the so-called prudent yield of each of the proposals.

The GHD yields were based on historical rainfall records and related data and did not account for environmental flow requirements or severe drought periods.

The prudent yield figures do not considerably change the GHD yield rankings, but reveal a significant range in differences.

The GHD report also identified a “number of key factors with potential to jeopardise the viability of a dam at Traveston”.

These include geological conditions along the site of the dam wall, the availability of material nearby to build the dam wall and the cost of haulage for concrete aggregate if not locally available.

It also said more information needed to be gathered to design the spillway size, and environmental constraints of the World Heritage listed Great Sandy Strait needed to be investigated.

GHD also recommended more investigation into land contamination from gold mining and agriculture.