‘Everything is saturated’: what’s driving the latest floods in eastern Australia

It's been a very wet couple of years. By now, most people are all too familiar with La Niña and the weather event's effect on rainfall over parts of Australia.

In the past week alone, heavy rain over Victoria, southern New South Wales and the northern parts of Tasmania has led to widespread flooding.

In Victoria, major flooding has occurred in the Murray, Wimmera, Campaspe, Loddon, Ovens, Goulburn, Avoca, King, Broken, and Maribyrnong rivers, and Seven and Castles creeks, according to the Bureau of Meteorology. In NSW, major flooding has affected the Barwon, Darling, Macquarie, Bogan, Lachlan, and Murrumbidgee rivers. There has also been significant flooding across the northern half of Tasmania, including in the Macquarie, Meander and Mersey rivers.

Dams have spilled for the first time in decades: Dartmouth Dam for the first time in 26 years, Lake Eildon for the first time in 28 years. On Monday afternoon, Thomson Dam in west Gippsland - Melbourne Water's biggest dam - was at 99.2% capacity.

There is unfortunately little reprieve for those in flood-affected areas, with heavy rain and storms forecast later in the week for eastern and south-eastern Australia.

When parts of the country's east coast flooded in February, scientists pointed to an "atmospheric river" that developed in the skies over Brisbane as a factor. Ten months later, what's driving the floods further south?

A triple La Niña event may be under way, but the main climate driver behind the extensive recent rain is the negative Indian Ocean dipole (IOD), according to Dr Milton Speer, a visiting fellow at the University of Technology Sydney.