Dam wrong: More dams not a solution to Murray Darling Basin floods

OPINION: Building more dams is not a solution to floods, nor drought, writes Peter Hunt.

The cry has gone out “build more dams to stop the floods and capture more water for dry times”.

Others want the Murray Darling Basin Authority’s dam operators to release more water when faced with a wet spring forecast, to create enough airspace to take the edge off floods.

But simple solutions to complex problems are usually wrong.

The Hume Dam spilling. Picture: NCA NewsWire/Simon Dallinger

The primary purpose of the basin’s large dams is to secure the water that underpins $22 billion a year in food and fibre production, plus supply two million Australians, from Albury to Adelaide.

In fact the Basin Officials Committee that oversees the MDBA operating rules states that when it comes to floods the key objectives in running the Murray system are, firstly to protect dams and weirs, second “maximise available water” and lastly limit flood damage.

The Echuca Floods begin inundating the homes on the wrong side of the Levy wall. Picture: Jason Edwards

That’s not to say flood mitigation is not part of the MDBA’s operating rules, given it can lower Hume Reservoir by up to 2m from its full supply level, equivalent to 386 gigalitres of its 3000GL capacity.

But the dam operating rules demand those flood mitigation releases are fully offset by the forecast inflows by the end of November.

So, given the inaccuracy of the BOM’s or other global climate models’ extended forecasts, it’s no surprise dam operators are extremely cautious when it comes to flood mitigation releases.

As we saw in 2014, spring rainfall forecasts can quickly dry up to nothing.

Sandbagging efforts in Echuca. Picture: Jason Edwards

As for building more dams, we need to remember that during the millennium drought not one of the southern Basin’s dams filled and spilled for a decade.

So what’s the value of building more of them?

It would mean destroying parts of yet another river valley and further curbing environmental flows, something that is no longer accepted by the majority of Australian voters.

We’d be better off spending the money on more levees and drains to protect our river towns, plus putting tighter controls on housing developments that have edged on to the floodplain.

Anyone proposing we build more dams also needs to ask themselves why we would further curb the basin’s flows, after just having spent $13 billion on its environmental revival.

Peter Hunt is The Weekly Times senior reporter.