Despite predictions of a wetter spring in large parts of eastern Australia, the south coast of Queensland received average or below average rainfall during September, prolonging at least 18 months of severe rainfall shortages in the region.
- The south coast of Queensland is still in severe drought after much of the east coast has recovered
- The Wivenhoe dam has dropped to 40 percent capacity
- Researchers have examined why the region has remained dry despite La Niña
This comes after spring rains largely failed last year in southern and eastern Queensland, despite an emphatically wet seasonal forecast.
“There were problems last year around the region that did not get typical rainfall as we would have expected during a La Niña year. Now it looks like it was sneaking back and we unfortunately have round two,” he said. Andrew Watkins, Chief Operating Officer at the Bureau of Meteorology.
Wivenhoe dam levels are falling
The drying time coincides with southeastern Queensland’s largest reservoir, Wivenhoe, which is falling to 40 percent capacity due to below-average rainfall.
It is lower than at the same time last year, when the dam was 42 percent full and continues significant declines over the last three years.
“We are not getting enough rainfall where we need it most – over our largest and most important dam, Wivenhoe Dam,” the dam operator said in a statement.
Southeast Queensland’s total dam levels are currently at 56 percent capacity — about 3 percent less than at the same time last year.
Seqwater said last month that water restrictions were likely to take effect in southeastern Queensland if the total sum of the area’s dams fell below 50 percent, which could happen in December.
“With the weather warming up, it’s now time for all of us to monitor our water consumption and be water wise,” Seqwater said in a statement.
Southeast Queensland still lacks La Niña rain
2020 was not the only year the south coast of Queensland has missed rain during the La Niña seasons, according to the Bureau of Meteorology’s Andrew Watkins.
“2000-2001 and 1988-89 were two La Niña periods where we also saw some droughts in that part of the world,” he said.
To better understand why the south coast of Queensland missed the La Niña rain last year, researchers from the Bureau of Meteorology teamed up with researchers from Australian universities to investigate why climate models have not accurately predicted dry weather.
“This forecast error in Eastern Australia was an unpleasant surprise to users of seasonal forecasts and damaged the credibility of seasonal climate forecasts,” the team led by Eun-Pa Lim, a senior researcher at the Bureau of Meteorology, wrote in the journal Scientific reports.
“The study highlights that it really is not as simple as ‘La Niña means wet,'” said Dr. Andrew King from Melbourne University, a co-author of the research.
The team found that other climate drivers, including a pattern of tropical storm activity called the Madden-Julian Oscillation (MJO), worked to suppress rainfall in northern and eastern Australia during November.
MJO can only be predicted exactly several weeks out, unlike La Niña, which can often be predicted months in advance.
“This means that if MJO does something weird later in the season, it will sometimes be missed in a seasonal forecast,” said Dr. King.
“When the model says something with really high confidence that is not happening, it is certainly worth inquiring about what went wrong,” he said.