If it dosen't rain in the next few months in some areas of Oz?.

I forgot to add, when I was in short pants in the 1950's, I lived 2 kms from Gnangara Lake.
Gnangara Lake sat over the top of the Gnangara Mound, the underground aquifer that supplied ever-increasing amounts of Perth's water, for all purposes, from drinking, to market gardening, to industrial use.

The Gnangara Mound ended up supplying about 60% of Perths water requirements as the dams in the Perth Hills continued to never fill up from the 1980's onwards.

Gnangara Lake in the 1950's was crystal-clear water, like rainwater, with a purity of 99.999%.
The lake was 12 feet deep (3.66M) and you could see the sandy bottom 50 metres out from the shoreline.

But constant water demand, unlicenced bores, and unmetered water draw, saw the massive Gnangara Mound aquifer deplete to about half its original size.
Gnangara Lake totally disappeared in the 1970's, never to return.

The Gnangara Mound is still supplying a percentage of Perths water, and its level is still declining.
It's a sad state of affairs that reflects Govt mismanagement, lack of adequate water controls, poor planning and a lack of political will, and decision-making.

The Gnangara Mound recharge area continues to be built on, paved over, and generally neglected in planning considerations. There's no sign this will change, not now, nor in the future.

Cheers, Ron.

If you pipe the water out of a river then the river dries up. The cotton farms at the top of the Darling show that.

From Wiki
"It is also the fourth-largest river in Australia by volume of flow, but is so erratic that its discharge can reach the mean discharge of the Yangtze River (after two severe cyclones in 1958) or have as many as seven months with no flow whatsoever (as in 1923). "