Seldom do flooding rains reach Lake Eyre in the arid heart of the continent, but it has now happened two years in a row, triggering a spectacular explosion of life in the region.

The outback rivers are flowing from a series of rain events across the deserts of central Australia which began late last year, and there is nearly as much water in Lake Eyre as there was at the height of last year's flood - with more to come.

The big difference this year is the huge flood working its way down the Cooper Creek, east of Lake Eyre. It is 20 years since the Cooper flowed into Lake Eyre but it will soon reach there, adding to the water already delivered by the rivers from the north, channelled down the Warburton Creek.

Outback adventurer Rex Ellis has witnessed every flooding event at Lake Eyre for the past 50 years. He famously crossed the lake by boat when it was last full to the top in 1974 and believes this year's flood will be the biggest since then.

"This is the driest state in the driest continent on earth apparently - apart from Antarctica - and there's more water in north-east South Australia than you can poke a stick at!" he said.

Desert areas that were ravaged by dust storms just before Christmas are lush and green, with patches of brilliant wildflowers.

The vast floodplains around Lake Eyre have been turned into wetlands brimming with life, and the birds have returned to breed.

When drought takes hold of this country, as it usually does for year on end, there's no sign of the birds. But as soon as the rivers run they're back.

How they know the water is there remains one of the big unanswered questions for the scientists, including Professor Richard Kingsford, a leading expert on Australia's waterbirds.

"We don't even know the basics of where these birds are going, how they know to go to a place," he said.

Scientists are working on theories that the birds may carry out reconnaissance flights to check on weather changes in the outback and that those hatched in central Australia may have the homing instinct to return there when a good season occasionally arrives.

Pelicans have returned to rivers and waterholes all around Lake Eyre to breed, as have many other species of waterbirds, including cormorants and ibis.

Last year's flood flow to Lake Eyre provided a crucial bird breeding opportunity after the long drought. It is rare that they would get the benefit of another flood the following year.

"These are the critical ones," said Professor Kingsford, "where you've got one flood that has primed the system last year and then a massive flood that's coming down."

"What's so exciting about this one is that it's coming down all of those river systems."

The Cooper Creek has already crossed the Birdsville Track on its way to Lake Eyre and the South Australian Government has had to dust off a 40-year-old punt to act as a vehicular ferry.

The punt has been sitting in the desert since the Cooper last crossed the Birdsville Track and ran into Lake Eyre in 1990.

On islands in the middle of Lake Eyre, thousands of seagulls have joined the bird invasion to breed. They are regular visitors to Lake Eyre at flood times but their big numbers indicate how bountiful the season is expected to be.

On the floodplains, alive with life at all levels, the predators stalk their prey. The dingoes are sleek and well-fed and the skies are filled with wheeling kites.

"These boom periods are when the whole biological system takes off, and whatever level you're looking at, from the microscopic up to the pelican, they're doing their thing," said Professor Kingsford.

Cattle stations emerging from the drought years are trying to restock their properties, now boasting knee-high pastures that will provide feed for another two seasons.

On Gidgealpa Station, near Innamincka in the north-east corner of South Australia, Jason Barnes has just taken delivery of 80 cows from the Northern Territory to start rebuilding his herd.

"It's hard to buy the cattle back, to buy good cattle back," he said.

"Everyone in Australia is looking for cattle, everyone has had a good start, so it's hard. We're lucky we got onto some good cattle here, got a good starting block. We should be all right."

The rare greening of the red centre is expected to produce a big tourist boom for the second successive year.

Rex Ellis, who has just taken a group in boats down the Warburton Creek to Lake Eyre, puts it this way: "Muslims like to go to Mecca. Aussies like to go to Lake Eyre."