Where are the Canadian lakes in outback Queensland? They can't plop down on a river, and the next bet is a water storage dam, probably covered in wires?
Canadair did and published study last century when a CL415 was here on a sales mission. It proved that there were enough water in rivers and dams along the eastern seaboard to support the operation of these aircraft.
At that time in history, aerial assets was a four letter word.