More torrential rainfall in the Great Barrier Reef catchment: La Nina coming to an end?

After the flooding in late January in the Fitzroy catchment, and the downpour in Mackay causing rising levels in the Pioneer river earlier this month, the turbulent Queensland weather has caused more phenomenal localised rainfall in Rockhampton this morning, with over 200mm of rain falling in less than 2 hours. As residents in Rockhampton begin the cleanup process, the Chief executive officer of the Fitzroy Basin Association (Suzie Christensen) discussed management principals and how to reduce the impact of the recent flooding in the catchment on the inshore reefs of the Great Barrier Reef.

“The Fitzroy Basin is the largest river system draining to the east coast of Australia, with 20,850 kilometres of waterways all leading to the reef lagoon.

“The effect of this flood would have been worse if landholders weren’t already taking steps to reduce impact on the land by retaining ground cover and using best practice farming techniques.”

“In particular where land practices had allowed the ground to be disturbed such as some mining on floodplains and some areas cleared for cropping and grazing.”

Ms Christensen said the flood water plume into the Great Barrier Reef lagoon would have consequences for the reef ecosystem.

“The flood waters are flushing sediment, fertilisers, pesticides, herbicides and other run-off several kilometres out onto the reef.

“The delicate balance of the reef ecosystem is upset by changes in water quality, and the thick cloud of sediment will also block sunlight and prevent coral from photosynthesizing.” (Link)

Further north in Mackay the Mayor of Mackay is quoted as saying that last week’s flooding could be classified as a “one in 200 year event“. Over 625mm of rain fell in 6 hours on February 15th, averaging 132mm per hours (double the total of the classification of a one in 100 year event), peaking at 184mm in a one hour period – quite an event! After such a substantial wet season, the director of meteorology at the Australian Bureau of Meteorology, Dr Geoff Love, stated that the La Nina event identified last November is “probably reaching its peak“. However, according to the World Meteorological Organization, the La Niña period is expected to last until June or July this year, and could last longer.

  • La Niña conditions have become slightly stronger in the last three months
  • Sea surface temperatures are about three to four degrees colder than average over the central and eastern equatorial Pacific Ocean
  • La Niña already has influenced climate patterns in many parts of the globe.
  • La Niña is the meteorological opposite of the better-known El Niño
  • La Niña. Central and eastern Pacific Ocean areas are generally cool, while those in the west remain warmer. This is associated with the frequency of heavy rainfall on the western side of the Pacific Rim.
  • El Niño. The El Niño phenomenon is linked with warmer temperatures in the central and eastern Pacific areas and can lead to drier conditions
  • The El Niño/La Niña cycle historically happens every four to seven years and is strongly linked to major world climate fluctuations:
  • Typically, La Niña will follow an El Niño event and last up to 12 months.
  • Exceptionally, it lasted for two years from early 1998 to 2000. (Link)