Add salt at the mouth to save the Murray

The release of a new Murray-Darling Basin plan next Friday is likely to reignite debate over how best to solve the problems of the Murray River. It will further pit some environmentalists and some South Australians against upstream irrigators over how to fix the two large freshwater lakes at the mouth of the Murray River.

Lake Alexandrina and Lake Albert are situated behind the narrow expanse of water known as the Coorong. Beyond the Coorong is the Southern Ocean and upstream of the lakes is the river proper.

Few understand how different ecologically this region was before European settlement and the effects of agriculture and the construction of barrages designed to keep out salt water.

Oral histories from local families and the diaries of the first European explorers paint a different picture of the lakes from that shaping the debate today. If we look back to what the river was like before the barrages, then there is a different solution from that being proposed.

It is a solution that may not be palatable to the SA government or those communities that have grown used to life behind the barrages but one that is a cheaper and more environmentally sustainable solution in the longer term.

Many academics and bureaucrats deny that the lakes were estuarine. But families who have lived in the region for generations explain, for example, that in 1915, before the barrages and during a period of prolonged drought, sea water penetrated beyond Lake Alexandrina up the Murray River as far as Mannum. There were sightings of a shark at Tailem Bend and a dolphin at Murray Bridge.

Since 1941 and the completion of the barrages that block 90 per cent of flows between the lakes and the Southern Ocean, a new history and geography of the Lower Lakes, Coorong and Murray mouth have been created.

These barrages were built to regulate the river flows, improving river use for local irrigators, boating and recreational activities and creating the artificial freshwater environment in the Lower Lakes that people enjoy today.

This has seen community understanding of where the river's mouth is moved to the sand bars beyond the barrages, rather than 52km upstream at Wellington, where the river empties into Lake Alexandrina.

Farming, urban development and recreational use during the past 70 years have entrenched this understanding of the lakes. It has reached the point where the once estuarine Lower Lakes have become eligible for freshwater allocations from the Darling and Murray rivers under national water-sharing plans, enabling the SA government to argue for more environmental flows from upstream.

To get a fresh perspective on the region, it is worth going back in time and considering the diary of the first European to visit the region. British explorer Charles Sturt travelled down the Murrumbidgee and then the Murray in a whale boat, arriving at the place now known as Wellington in 1830. He described this as the Murray's mouth, writing:

We had, at length, arrived at the termination of the Murray. Immediately below me was a beautiful lake, which appeared to be a fitting reservoir for the noble stream that had led us to it; and which was now ruffled by the breeze that swept over it.