A woman who drowned three of her children and attempted to kill a fourth by driving the family car into an Australian lake has been sentenced to 20 years and six months in prison.

Akon Guode, 37, drove an SUV carrying four of her seven children into the lake in Melbourne in April 2015. Her five-year-old daughter Alual survived after passers-by pulled her from the partially submerged car.

But Guode's 16-month-old son Bol and four-year-old twins, Hanger and her brother Madit, died.

Victoria State Supreme Court Justice Lex Lasry said he would have sentenced Guode to life in prison if she had not pleaded guilty to murder and attempted murder.

"People don't understand why you did what you did," the judge told her.

"In my opinion, your actions were the product of extreme desperation."
Guode wept and wailed throughout her sentencing hearing as the judge outlined her crimes and her troubled life that led to it.

Born one of 16 children in 1979, she fled Sudan's civil war in which her husband died, arriving in Australia as a refugee in 2006.

The judge set a non-parole period of 20 years and said she is likely to be deported on release.

Her hometown, the city of Wau, is now in South Sudan, which became an independent country in 2011. It was not clear to which country she will be deported.