January 9, 2023 - Flooding along the the Murray River, South Australia

Flooding, black water event in South Australia, Murray River
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Wave after wave of heavy rainfall fell across a wide swath of
southeastern Australia in the closing quarter of 2022, leading to
extreme flooding in the Murray-Darling basin. According to news
reports, the basin saw its wettest October on record in 2022, with
rainfall totals nearing 150 millimeters—four times the average for the
month and well above the previous record set in 1950.

By late November, the waters in the Murray River had begun to rise
ominously. On November 21, the South Australia State Government
declared a major emergency due to flooding, advising that peak flow
near Christmastime was likely to result in 185 gigalitres of water flow
downriver per day, with a chance of higher. That’s the equivalent of 48
billion U.S. gallons per day, or about 73,000 Olympic-sized swimming
pools.

In early January 2023, flood waters were still cresting in some
locations. On January 5, local news reported that a levee had been
breeched by rising waters near Mannum, a town located on the west bank
of the Murray River in South Australia. By January 7, peaking
floodwaters had inundated most of the town, including flowing down
Mainstreet. Because of the very flat topography of the Riverlands near
the Murray, water recedes exceedingly slowly. Even after the crest is
past, residents may wait weeks before they can begin to assess damages
to their property-and months more before the river fully returns to its
banks.

The long-term, vast flooding has also caused fish kills and toxic algae
overgrowth in some regions, including in Lake Bonney, which had to be
closed to recreation temporarily. Widespread “blackwater” events have
been reported. Blackwater occurs naturally when floods wash leaves,
grass, and other organic materials into waterways. This creates an
abundant nutrient load, can be a good food source for fish and other
aquatic life. As temperatures warm, these creatures become even more
active, and their activity, along with decomposing organic matter,
depletes oxygen in the water. This low-oxygen blackwater can lead to
extensive fish kills.

On January 6, 2023, the Moderate Resolution Imaging Spectroradiometer
(MODIS) on board NASA’s Aqua satellite acquired a true-color image of
the flooded Murray River in South Australia. Below this is an Aqua
MODIS image acquired about a year prior, on January 15, 2022, which
shows a view of the Murray in a more normal year.

Image Facts
Satellite: Aqua
Date Acquired: 1/6/2023
Resolutions: 1km (131.9 KB), 500m (325.8 KB), 250m (190.1
KB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2023-01-09

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