There is not a lot that those of us sitting in Canberra or Wagga Wagga can usefully tell the people of Forbes as they have done such a good job in responding to the current flood.

It is heartbreaking for farmers who have suffered through the drought to now have excellent crops destroyed in the current flood, to the detriment of all the businesses depending on them.

I wish the people impacted all the best in recovering from this flood as soon as possible.

My job as an academic funded by taxpayers is to help society and governments make well informed decisions.

Building a dam is a big, expensive decision where there will be risks, losers and winners.

Governments have the right to decide to build a bigger dam but I believe they should only do so when they have done their due diligence, understand the risks and consider their moral obligation to compensate the losers.

In the case of the proposed raising of the Wyangala Dam, McCormack announced the "commitment" of the Federal Government on the 16th October 2019 without either a business case or an environmental effects statement.

Further, the announcement pre-empted the NSW Government's September 2020 draft Lachlan Regional Water Strategy that proposed a number of sensible alternative options for enhancing water security in the valley.

The dam project is immensely risky.

Global experience is that while flood control infrastructure controls medium sized floods it leads to more catastrophic outcomes for people on the floodplain when the inevitable big flood hits.

Further, we are being asked to believe that it will be some sort of 'magic pudding' dam, that can be both empty to catch floods yet full to maximise water supply for irrigation.

If the proposed 21 GL of additional water supply was paid for under the National Water Initiative's cost recovery principles, could irrigators afford the cost of this new water?

At around $2 billion in capital and offset costs, I calculate the cost of the bigger dam as over $90,000 per ML (million litres) compared to the price of a general security water licence of over a thousand dollars a megalitre.

There are many losers from raising the dam.

Evidence from the northern Basin is that livestock turnoff has fallen by around 40 per cent for floodplain pastoralists along more regulated rivers.

Will the Federal Government compensate the pastoralists of the lower Lachlan for falling production?

More losers: farmers whose best land will be inundated by the bigger dam; fishers, since high flows enhance native fish populations; anyone who depends on aquifers recharged by high waters; Indigenous communities who use river resources; and nearly half a million hectares of floodplain wetlands.

For these reasons, the cross-party NSW Legislative Council Portfolio Committee that investigated the proposal unanimously found in March that: "That the claimed economic and water security benefits of the election commitment to raise the Wyangala Dam wall are yet to be demonstrated" (Finding #3).

The job of a local member of parliament is to represent the best interests of all of their constituents.

Take for example implementation of the three NSW Floodplain Management Plans for the Lachlan that are now around a decade old.

The Gooloogong to Jemalong Gap Floodplain Management Plan (2011) says that, "A major restriction to flood flows is the Forbes/Stockinbingal Railway", which a number of local people tell me has exacerbated flooding around Forbes.

Surely a diligent local member would have asked the Minister for Transport to have the Inland Rail Track Corporation rebuild this viaduct with more culverts for the safe passage of flood water at Forbes.

Similarly, if flooding of the Newell Highway is a major problem, wouldn't the local member help by seeking the Minister for Transport's support to raise the road on a viaduct?

In terms of water security, why did the Lachlan valley irrigators largely miss out on Federal Government water efficiency program funding compared to other valleys in the Murray-Darling Basin?

Perhaps the Member for Riverina could "tell" the people of Forbes and the broader Lachlan valley what practical action he is taking for better water management rather than relying on a questionable dam proposal.

Professor Jamie Pittock

Fenner School of Environment and Society, The Australian National University