Wednesday, 3 October 2007

MEDIA RELEASE

Climate change, rainfall, and runoff

While there has been attention given to the effect on general rainfall under climate change, Bureau of Meteorology researchers are turning their attention to a more specialised area of research — Probable Maximum Precipitation or PMP.

Probable Maximum Precipitation is the greatest depth of rain possible for any given duration, area, location and time of year — with no allowance made for long-term climatic trends.

PMP is a particularly important input to the design of large storage dams around Australia. It assists engineers in designing the capacity of spillways so that the dam structure can safely withstand the impact of the extreme flood that they estimate will result from the PMP storm event.

Because PMP estimates rely on rainfall and moisture associated with previous significant rainfall events, they may be influenced by changes in the amount of moisture that are available under different climate conditions.

With climate models predicting an increase in extreme precipitable water for most seasons and locations across Australia — particularly those that previously have been associated with significant rainfall events — the challenge is to assess whether probable maximum precipitation may change, and relate any such changes to the design of large scale civil engineering projects.

"Our research examines future likely extreme rainfall under different climate scenarios. Our aim is to ensure that we can confidently provide estimates of extreme rainfall into the future," said Doerte Jakob from the Bureau of Meteorology.

The Harding River dam spillway, south of Roebourne, Western Australia, after Tropical Cyclone Monty, March 2003. Credit: Water Corporation (Western Australia).

Robert Smalley 0434 821 926
Doerte Jakob 03 9669 4317
Media assistance: David Grant 0439 452 424