Relentless summers create dam dilemma in Australia
By BRIAN ROBINS
January 13, 2010 RISING average temperatures are reducing run-off into Sydney dams when it rains, putting the future of the city’s water supplies under a cloud. As a result, Sydney Water wants to operate the Kurnell desalination plant even when there are several years’ water supply in the Sydney dam network. Trials are under way at the desalination plant, which is expected to be in full operation soon. The State Government is yet to decide how soon the desalination plant will begin operations after the trials that will run for at least two and perhaps as long as four years. Sydney Water wants to operate the plant once dam storage levels drop below 70 per cent. Of concern is that rising average temperatures mean rainfall run-off into catchment areas will decline at a time of declining rainfall. ”A small decrease in rainfall translates into a more sizeable decrease in run-off,” said the managing director of Sydney Water, Dr Kerry Schott, referring to research by the CSIRO. Ian Prosser, the CSIRO’s science director with the Water for a Healthy Country project, has looked at historical records and found the variability of run-off levels is magnified when rainfall is highly variable. ”If you have a decline in rainfall, you have a bigger decline in run-off,” he said. ”Only 5 to 10 per cent of rainfall in a catchment goes into the dam.” Dr Prosser conceded that higher average temperatures might also affect run-off, since this might be drying out the catchment area to a greater extent, so that more of the initial rainfall was then absorbed before any run-off into dams occurred. ”Water planning has relied on historical records and the prospect of climate change means that this gives only a limited perspective. What if these unprecedented conditions continue?” …
