Keith Walker, Murray-Darling Association Forum - Murray Bridge - 20th of March 2007

Proposed Temporary Weir Below Lock One

Minister, Ladies and Gentlemen, Good Morning.

I would like to pay respect to the Ngarrindjeri Nation, traditional owners of the lands along the Lower Murray.

The Murray is a river in crisis. There is an irony in saying so, because for much of its evolutionary history the river has been in a crisis, or recovering from one, or about to confront another. It is part of the natural order of things, in an arid climate.

The old Murray had an erratic pulse. Floods and droughts were common­place, but unpredictable, and the native plants and animals were cast in that mould. Most of them are hardy opportunists, able to exploit the good times and endure the bad.

The modern crisis is different. Although we cannot escape the worst floods and droughts, we’ve steadied the river’s pulse by building dams and controlling the flow of water. Smaller floods and droughts have been eliminated. In some ways, the Murray has become a hostile environment for its own native flora and fauna. We’ve changed the river to such an extent, and at such a pace, that the entire ecosystem has been transformed. And still we persist, knowing what must be the long-term consequences.

Today, we have a drought—another, more transient crisis—that offers a glimpse of a future that none of us wants. There is too little water in the system to satisfy our needs, and we want more. We have not learned that the key to sustainability is to ease our demands in times of stress—just as a farmer keeps grain in reserve so that he can plant again when the rains return. We want to annex more water, from what little remains, by building another weir.

I’d like to sketch for you some of the changes associated with weirs on the Murray. Mind you, the weir planned for Wellington is not like those upstream—it will have a lower profile, and it will be ‘temporary’. Nevertheless, its effects will be significant, and added to those I’m about to describe.

There are 10 weirs on the Murray below the Darling. Six are in South Australia, the first at Blanchetown. Downstream there are more than 100 km of riverbank levees, and barrages to separate the lakes from the Coorong and the ocean. The weirs are so closely spaced that the river is no longer really a river but a chain of ponds, one cascading into another. The weirs and levees keep the river from its floodplain, and the barrages keep the sea from the river. Our control over flows is such that two thirds of the river’s discharge are diverted and only one third remains; the river mouth must be kept open by dredging. Our Ramsar commit­ments suggest that we will protect the Coorong, and Chowilla, yet both are being denied the water needed even for survival.

If you think about what a weir is designed to do, then consider a chain of 10 weirs, plus levees and barrages, and it is not hard to imagine the effects. So much of what scientists tell us is rooted in common sense.

A weir is designed to hold water, of course, and seasonal and annual changes in the river level are tightly controlled. There are other water-level changes, related to weir operations rather than flow, and they produce gradients of fluctuations between each complement of weirs. These have a big effect on plants growing along the river margins. More about them in a moment.

Weirs trap sediment as well as water. The weirs have caused the Murray to adjust its bed slope by eroding its banks below each weir and depositing the sediment above the next weir. In time, the river will resemble a staircase, with 3-m risers, extending over 600 km. Erosion and siltation are inevitable companions to dams and weirs.

One of the most worrisome changes due to the weirs is that the river is no longer able to flush as much of the salt that comes from groundwater underlying the basin. Half of the salt entering the Murray enters in South Australia, and a quarter of South Australia’s contribution is due to the weirs. The salt is being accumulated in the floodplain soil, and when the river eventually does flood again there will be slugs of highly saline water to contend with. Removing some or all weirs is not an easy option because there would be a short-term increase in river salinity, before a new balance is struck. It is a big dilemma for South Australia. What do we do?

The weirs have disconnected the river channel from the river floodplain, when those are two parts of one ecosystem. Most of the biodiversity associated with the Murray lives not in the channel, but on the floodplain. If the wetlands and woodlands are isolated, the river becomes merely a conduit for water.

The slow-flowing weir pools are home to wetland species rather than riverine plants and animals. The plants we see along the river banks today are refugees from wetlands, as in the days before the weirs the banks were mostly bare. Yabbies in the river today really belong in wetlands, but they have invaded the channel at the expense of the Murray crayfish, now virtually extinct in this region. Fresh­water mussels show the same pattern. Many snails have disappeared, fish have declined and red gums and black box in some areas are dead or dying. It’s a pretty bleak record.

What then of another weir? It is to be ‘temporary’, and smaller than the weirs upstream, but it is a weir nonetheless, and it will compound the effects already in train. It is planned for part of the river that is prone to algal blooms, in an area where the sediments are prone to erosion. It’s easy to conjure a dark view.

Much depends on what is meant by ‘temporary’. Climate forecasts suggest that droughts like this one will become the norm in future. What then, for a weir that may cost $25M to remove? Will we remove it? And when we do, how will we repair the damage it has caused?

Looking back at the sometimes-heated debate over the weir proposal, fuelled by a slow trickle of information from DWLBC, I feel no-less dismayed by the process of engaging the public than by the prospect of another weir. The Department’s FAQ sheets have been helpful, but they have trailed behind the leading edge of the debate. We cannot blame people for becoming upset at the prospect of a dimly-perceived, hastily assembled weir that will cost the economy $110M. Who knows what it will cost the environment.

We may have to accept the advice that, even with $110M to spend, there is no better, quicker alternative. If, in the government’s mind, a weir must be built, let us recognize that alternatives did exist a few years ago, had we been farsighted enough to see them, and that alternatives will exist again in future, once the drought eases. Let us ensure that ‘temporary’ means what it says, and that the apprehension we feel now will not be overwhelmed by the prospect of more droughts to come.

Let’s work hard to get it right. There is a tyranny in life along rivers—everyone who lives upstream is a bugger, and everyone downstream is a whinger. In South Australia, at the end of the river, we could claim to have a unique perspective on people in eastern Australia! And they on us. But it would be ridiculous to blame the other states for all of our problems. At least some are of our own making. There is a great deal we could do to put our own house in order and then, having captured some of the moral ground, we could plead for reason. The role of leader is more potent than that of a plaintiff.

Thank you for listening.