The "Mighty Murray": Image via Wikipedia
After a decade of drought and two very wet years Australia is facing a third consecutive wet year. La Niña is back and the Murray Darling basin is already 87% full as of 23rd September. Last year levels were the highest since 2001 and this year they are even higher.
Water levels are high across all of Australia except in the West. The ground is also reported well saturated and as the rains come the controlled release of water from the dams system will be crucial to prevent a repeat of this year’s floods in January and February 2012.
… if the spring rains continue, the water storage that is so vital to the prosperity of irrigation farmers along the Murray River and to Adelaide’s drinking water supply, will be full by next year. Around the nation, water storage reserves are at levels not seen since the start of the decade-long drought in the late 90s.
The Bureau of Meteorology estimates Australia’s 261 largest drinking water and irrigation storages, with a total capacity of 78 million megalitres of water, are on average 80 per cent full. This time last year, the figure was 65 per cent.
Drinking water supplies for the major cities have been replenished by the wettest 10-month period ever recorded, between July last year and April. Sydney’s city water storages are now 79 per cent full, while dams supplying Adelaide and Brisbane are at a healthy 83 per cent capacity. Even Melbourne’s once critically low dams have climbed to 63 per cent full with recent rainfall, their highest levels in 12 years. Melbourne’s largest supply dam, the Thomson, is this week half-full for the first time since 2005.
The anomaly is Perth, which is still critically dry, relying on desalination plants and aquifers for 60 per cent of its water supplies. …..
… The filling of the giant Dartmouth Dam is an extraordinary feat that has happened just three times since the vast reservoir in the remote Victorian high country was commissioned in 1980. Only in 1990, 1993 and 1997 has water overflowed from the four-million-megalitre dam and thundered down its 180m drop spillway. It’s a far cry from this time last year, when the Dartmouth Dam was just 26 per cent full. Now holding 2.8 million ML of water, according to operators Goulburn-Murray Water, it’s a rejuvenation that has tourists, anglers and irrigation farmers flocking to enjoy the dam’s beauty and plentiful trout.
The level in the Dartmouth Dam is so high that irrigation needs for farmers downstream are assured for about 4 years. But the risk of flooding is being closely watched
La Niña has become synonymous with flooding as a result of above average rainfall. This year is likely to see a re-emergence of both but on a smaller scale than last year. “Above average rain through northern and eastern Australia is likely to once again prompt broad-scale flooding. Areas which will see a return of above average rain include; Queensland, the Northern Territory, northern parts of Western Australia, north-east parts of South Australia, much of New South Wales and northern Victoria,” says Dick Whitaker, Chief Meteorologist at The Weather Channel.
…. The Australian cyclone season runs from November to April and The Weather Channel expects a more active season compared to last year. “This year is likely to be a more active season than last year when despite strong La Niña conditions we saw only 11 cyclones. We are expecting a total of around 12 to 13 cyclones this year in Australian waters, but on average only half of our cyclones actually cross the coast,” says Tom Saunders, Senior Meteorologist at The Weather Channel.
“About 5-6 cyclones can be expected off the north-west coast of Western Australia and two of these should cross the coast, one of which is likely to be severe (category 3 or above),” he continues. “Off the Queensland coast, 4-5 tropical cyclones are likely, with one or two coastal crossings. While off the north coast between the Kimberley and Cape York Peninsula, four cyclones are likely, three of which should cross the coast,” Saunders continues.
“If La Niña conditions strengthen over the next few months as predicted by some models we may add one or two more cyclones to the forecast for each region,” says Saunders.
Paradoxically, “the heavy rains last year have pushed the nation’s grassfire risk to levels not seen in 40 years, with an area in central Australia twice the size of Tasmania having burned since June”.
The k2p blog 