Creek and river road crossings were closed for part of the week as water flooded fords.

But the government, which is already building a series of three dams which will divide Lake Alexandrina into separate, artificial salt and fresh-water zones, warned that no amount of local rain could make a realistic difference.

Environment department chief executive Allan Holmes said local rain could raise the water level marginally – both Lakes Alexandrina and Albert are now below sea level.

Only a huge inflow from the Murray-Darling catchment further upstream will see the lake’s health restored.

The building of the three so-called regulators, actually earthen and steel-paneled dams, is fiercely opposed by local environment groups.

The government hopes to stop acidic water from the Finnis River and Currency Creek flowing into the Goolwa Channel, but environmentalists say a much better solution would be to remediate the area by planting more native and imported grasses, which would increase soil nutrients.

Last weekend South Coast campaigners set up a “fresh water embassy” on the lake’s shores, mirroring the Aboriginal tent embassy at Parliament House in Canberra.

Three hundred and fifty people, including Greens senator Sarah-Hanson Young and her daughter and mother, joined “mourners” paying their respects to the Murray.

“We needed to grieve,” said Professor Diane Bell of the River, Lakes and Coorong Action Group. “Watching on a daily basis as thousands of tonnes of clay and sand and rumble are being dumped in the channel between Hindmarsh Island and Clayton Bay, hearing the whine of the trucks and knowing that this weir will cut Lake Alexandrina off from the fresh water of the Finniss River and Currency Creek has been painful. A complex eco-system is being cut into pieces and there are no credible plans to undo the damage.”

“This is ecological vandalism,” said Sarah Hanson-Young. Flags were lowered to half mast and the procession poured water from the tributaries into the narrow stretch of water still running between the cliff and the weir wall. A wreath of fresh water rushes and grasses in the shape of a boat was then cast into the water and sailed off to Lake Alexandrina.

“Our most recent monitoring shows that the water coming down the Finniss River and Currency Creek is not acidic,” said Prof Bell. “The rains have diluted the acids and the water at the weir site is alkaline. The country is greening up. A prudent policy of a responsible government would be to ensure that fresh water from the tributaries continues to flow and is not dammed and diverted further upstream.”

Adelaide University aquatic ecologist Dr Mike Geddes said the great earthen wall represented “the biggest environmental insult to the River Murray system.”

Dr Geddes said the danger of acidity had been exaggerated.

Meanwhile, a senior United Nations adviser on international water issues, Maude Barlow, wants a State of Emergency declared and a Royal Commission into the Murray and lower lakes.

Ms Barlow extensively toured the region recently and gave a damning assessment of state and federal water policies.

“I toured the Lower Lakes of the Murray-Darling Basin by land and air and was devastated by what I saw,” she said this week.

“Federal and State Governments kept blaming climate change and drought for the mess but there is much more to it than that. Australia has become wealthy by damming and diverting the the once mighty Murray-Darling Basin to grow crops for export and successive leaders have allowed the country's water heritage to be shipped out of the country in what is called virtual water trade.

“The river is so over over-extracted, particularly during drought, it is dying from the mouth up, and the resulting sulphuric acid and saline invasion is steadily advancing, killing the animals who ingest it.”

The call for a royal commission was rejected by water economist Mike Young, who said the lower lakes were now beyond help. A royal commission was needed 18 months ago, he said, and it is now too late.

Last month Professor Young told a parliamentary committee that parts of the Murray-Darling should be allowed to die to save other parts of the river system.

“It’s not about just closing off part of the lower lakes," he said. “It's about looking at every backwater, every wetland, every forest throughout the system from top to bottom and having a very careful discussion about which bits we invest in keeping going and which bits we are prepared to let go if it doesn't rain.”

The National Trust in SA has already placed the lower lakes and Coorong on its heritage-at-risk list.

“The Lower Lakes and Coorong is recognised as one of the top six water bird sites in Australia and is listed as a wetland of international significance under the Convention of Wetlands,” says the Trust.

“Existing regulatory structures and excessive water extraction have, for many years placed stress on the natural systems by changing the volume and pattern of seasonal flow of water.

“There has been an ongoing decline in biodiversity and population abundance for various species, including aquatic plants, migratory and sedentary birds, fish and frogs.

“The SA Government is taking three actions at present, none of which address the problem of lack of provision for environmental flows,” the National Trust says.

Meanwhile, the government has possibly already decided, but not yet announced, its position on the nationally-controversial Wellington Weir.

The project involves an artificial dam right across the Murray upstream of the lakes. It would completely stop the flow of Australia’s largest river system to the sea.

State Minister for Water Security Karlene Maywald says the decision will be reassessed at the end of August.

“Every month, the South Australian Government analyses seasonal forecasts and advice from the Murray-Darling Basin Authority to take into account the impacts on the Lower Lakes,” she said.

“Decisions such as the recent decision to cease pumping into Lake Albert also impact on whether we need to build the weir or not.

“A decision to commence construction will depend on local rainfall in SA and interstate over the coming months.”

According to Professor Young, while the government calls the Wellington dam ‘temporary’, it could well end up being a permanent barrier.

“Environmental impact statements assumed that this problem is going to be solved in three years' time because there'll be enough water in the system to enable us to remove the weir,” he said previously.

“I can't see how we can get the water back in the system in sufficient volumes that we could take out the weir.”

He says a flood similar to the monster 1956 event would be needed to fill the lakes and let the weir be demolished.