This major rally will be at the Goolwa Wharf as well as on the Hindmarsh Island Bridge which will be partly closed to traffic.

"We need to send a loud and clear message to the Prime Minister and all governments that we mean business. We will not go away, we have to stop this environmental disaster which is being allowed to happen along our river and Lower Lakes," Mayor Kym McHugh said.

"We now need a minimum of 375 gigalitres to save the Lower Lakes, there is enough water held in upstream storages which could be released and save our lakes from being irrepairably damaged.

"If this is allowed to happen through blinkered inaction, we will witness one of the most devastating examples of ecological vandalism this country has ever seen," Mayor McHugh added.