Queensland floods: the water journey to Kati Thanda-Lake Eyre
19 March 2019
Updated 16 April 2019
In late January and early February, an intense and slow-moving monsoonal low over northern Queensland caused record-breaking rainfall and disastrous flooding. Areas affected included the Townsville region and westwards, across large areas of the upper Flinders, Gulf Country and north Channel Country. Since then there's been a lot of water on the move—we follow its journey to Australia's largest lake, Kati Thanda-Lake Eyre.
A phenomenal amount of rain fell. In the seven days to 4 February 2019 our rainfall gauge at Townsville Aero recorded 1052.8 mm, and 1257 mm in the ten days to 6 February. There were several sites in elevated areas including Paluma, Woolshed, and Upper Bluewater that reported 12-day accumulations of more than 2000 mm! Further west, large areas recorded 300–500 mm including the northern parts of the Diamantina catchment—and it was this water that was about to start a long journey south.
Video: This short video looks back at the Queensland floods
While the rainfall has cleared across Queensland, flooding is expected to continue for a few more weeks in the northeast of South Australia as floodwaters continue to flow through the Goyder Lagoon and the Warburton River.
Where the water goes
Australia is divided up into drainage divisions and river regions based on topography. Most of the drainage divisions affected by the floods (such as around Townsville) empty out into the sea, with the exception being the Lake Eyre Basin—the lowest natural point in the country.
Animation: Topographic Drainage Divisions and River Regions
The vast Diamantina River catchment is in southwest Queensland and covers an area of approximately 119 000 sq km. The river passes through the town of Birdsville before crossing the Queensland–South Australia border 10 km south of Birdsville.
By the end of February, floodwaters captured by the Diamantina had been steadily moving downstream into the northeast of South Australia with flooding extending across vast areas of flood plain. On 22 February 2019, the Diamantina River gauge at Birdsville peaked at
8.15 m, surpassing the peak river heights of recent significant floods in 1999, 2000 and 2009—but falling short of the major flood of 1974 where the river peaked at 9.45 m.
By late March, the water had receded in the Diamantina between Birdsville and the Goyder Lagoon, and the vast flood plain was 'greening', following the inundation of the preceding weeks.
Photo: Birdsville, Queensland, in flood, February 2019. Credit: Birdsville Bakery
Lake Eyre Basin
The floodwaters continue to drain through the Goyder Lagoon in South Australia, which forms part of the Lake Eyre Basin. Water is flowing into the Warburton River on its way to Kati Thanda-Lake Eyre, one of the largest saltwater lakes in the world.
The Lake Eyre Basin region covers approximately 1.2 million sq km of arid and semi-arid central Australia. It represents 17 per cent of the continent and stretches, north to south, from just below Mount Isa in Queensland to Marree in South Australia. From west to east, it extends from Alice Springs in the Northern Territory to Longreach and Blackall in central Queensland. Lake Eyre is the world’s largest internally draining system.
Map: Lake Eyre Basin
By 5 March, the Warburton River gauge at Poothapoota in South Australia (just downstream of the Goyder Lagoon) gave the first indication that the floodwaters were moving through, with the water level jumping 0.8 m in about 30 minutes and then rising rapidly. The water level there peaked at 5.7 m on 12 March and has only dropped slowly—at 9 April it was around 4.5 m.
Water continued to flow into the Warburton River and as the channel filled it spilled to the flood plain. Inundation of flood plains, cutting of some roads and impacts to graziers are expected to continue over coming weeks, although the water level has started to recede slowly. A flood warning remains in place for the inland rivers of South Australia.
The first flows into Kati Thanda-Lake Eyre occurred on 15 March. Since then, water has continued to flow along the Warburton Groove towards Belt Bay in the south of the lake and also along a channel further east towards Madigan Gulf. Flows will continue for the next few weeks and it looks likely that they'll bring the lake to about one-third full.
But more water is on the way! Rain associated with the remnants of ex-tropical cyclone Trevor is expected to reach Kati Thanda-Lake Eyre sometime in May. While February's rain came to Lake Eyre from the Diamintina River only, the subsequent rain will bring not just more from the Diamintina, but also inflows from Eyre Creek. We estimate that the new flows may result in the lake being half to three-quarters full by June.
Australia's largest lake, Kati Thanda-Lake Eyre covers an area of approximately 9,500 sq km, however it's rare for the lake to completely fill. When the lake is full, it has the same salinity level as the sea, but as it dries up and the water evaporates, salinity increases.
Image: Lake Eyre, 2 April 2019. Credit: Sue Manniche
A 'green lining'
While Kati Thanda-Lake Eyre won't fill from the current flows, even partially filling the lake can create a desert oasis for a variety of birdlife, which will breed on the lake's islands and shoreline.
The floodplains of the Diamantina River and other channels in central Australia are also gradually rejuvenating after years of drought.
But, while the floodwaters are good news for some, it's hard to forget the devastation caused by the heavy rainfall and floods in northern Queensland, where homes were lost and much of the State's cattle industry wiped out.
Our thoughts are with all those affected by these devastating floods, or involved in supporting recovery and reconstruction efforts, which will continue for many months to come.
Animation: Floodwaters moving from Queensland to Kati Thanda-Lake Eyre, 14 February – 15 April 2019 (false-colour imagery). Source: Himawari satellite, Japan Meteorological Agency
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