There must have been a lot of head scratching going on in Perth the day 2007 Australian of the Year Tim Flannery talked up the prospects of the city becoming a ghost town.
’Strewth mate’ would have been the reaction as Perth residents stood at their ranch slider doors, listening to the radio as they hosed down their green lawns and verdant English gardens.
“This bloke reckons we’ll have to abandon the place ‘cos we’re running out of water.”
Whatever you think of the accuracy of Flannery’s prediction – and certainly the ex-pat Kiwi who works for the Perth Water Corporation wasn’t impressed when Urban reminded him of the quote – there’s no doubt that Perth has a water problem that has the potential to be bobby dazzler.
Part of the difficulty for the city planners is that while there are a lot of people certain that the situations is serious – but no one seems to be able to quantify accurately just how serious.
The bulk of Perth’s daily water consumption comes from a complex underground infrastructure of aquifer water, supplemented by above-ground water storage dams and lakes and a seawater desalination plant on the coast at Kwinana that’s intended to supply 17 per cent of Perth’s water needs.
That plant will be supplemented within a few years by another to be built to the south, that will see the water being piped back to Perth.
The city fathers have begun an exercise in urban planning that sees them trying to convince citizens of the value of the underground water, the possibility that it might one day run out, and the need for water conservation.
They’re also gradually introducing them to the fact that the city might have to supplement its water supply with recycled ‘grey water’ – not a prospect the average Australian likes to contemplate.
There’s a grim joke circulating in Perth: The good news is we’ll all be drinking recycled sewage. The bad news is there still won’t be enough to go round.”
At this stage it’s worth reading what Tim Flannery told an audience in Sydney back in May 2004.
“Perth today survives on fossil water, pumping water out of the ground. No-one knows how much is there or how long that fossil water will last.
But given the dire situation of agriculture in Western Australia, the increasing salination, the destruction of the western wheat belt, you have got to think that Perth might be the first metropolitan ghost town, if you want, of the 21st century. It is the most isolated city on the planet and is exquisitely vulnerable to the sorts of changes that global warming is bringing and amplifying every decade.” (Picture: Perth's water supply is under scrutiny. Picture (copyright) CSIRO Land and Water).
But tell most Perth residents that and they’re unlikely to take it seriously. Perth is a green, lush jewel - perched between the edge of the west Australian outback on one side and the sea on the other.
It’s said Perth is the most isolated modern city in the world - although that's often disputed - and as proud as Perth people are of their Australian identity, the fact is many of them trace their lineage back to ‘the old country’.
English country garden
On any weekend as they contemplate their isolation – a vast distance away from their own country’s east coast, let alone the country that many Perth residents’ forebears came from - there’s no doubt many people look outside and see their traditional English gardens as a cultural link.
Try to get them to adopt the varieties environmentalists recommend - native plants that are accustomed to surviving on little moisture. Good luck. Green lawns and colourful English flowers rule – as does a high water consumption from a mixture of bores sunk in people’s back yards, and from hoses that tap into the city supply. There are restrictions on sprinkler use, but early on any morning in suburban Perth, you’ll hear nothing but the constant hissing of irrigation systems watering lawns and gardens.
The only other noise will be the joyous screeching of the city’s abundant insect species, as they revel in the generous application of untold litres of Perth’s precious water supply. To be fair, many of the bores sunk in people’s gardens tap into Perth’s shallow aquifers, which contain water that isn’t suitable for drinking, and water authorities are encouraging as many of the locals to turn to bores as possible. However, if Perth’s climate is drying out – and there are plenty of people in Perth who would deny that - who knows whether this source is sustainable? There’s a lack of information on how many bores have been sunk, although one published estimate stands at 150,000.
And so where has this imbalance, this concern over the city’s water resource come from?
Climate scientists say they know the answer. Back in the 1970s, something weird happened to Perth’s weather patterns. There was a shift of some kind, which has brought higher temperatures and lower rain fall ever since. On the other hand, there are locals who would say that while weather does change, it doesn’t mean it won’t change back again.
Those people will no doubt be criticised by the more scientifically inclined, who say that in the meantime using potable water for watering the lawn just doesn’t make sense, especially since there is still a lot of doubt about how much water is left in Perth’s aquifers, and what continued high levels of draw-off will do. For instance, if the levels drop sufficiently, will sea water be drawn into the aquifers near the coast? If so, what damage will that do? Would it be possible to put enough water back into the aquifer?
Serious threats
A scientist from CSIRO - Australia ’s Commonwealth Scientific and Industrial Research Organisation – has been looking as closely as anyone at the various unknowns about Perth’s water supply.
Dr Tony Smith warned of dwindling water supplies around 19 months ago, when he presented results from a study of Perth’s groundwater levels. He said while one solution to the problem of dwindling water supply had been to increase the number of garden bores being used in Perth’s suburbs, there was still no surety that this is sustainable given Perth’s drying climate.
Back then, it was thought about a third of all gardens use groundwater from the shallow sandy aquifer, however, millions of litres of drinking water from the city system were still being used to keep lawns and gardens green.”
He said Perth’s groundwater supply was facing some serious threats, and that good data was essential to understand the resource and manage it wisely.
In his report in June 2006, Dr Smith said less than 20 per cent of all the water used in Perth now comes from the hills catchment area, which historically was Perth’s main water supply. “More than 80 per cent of comes from groundwater,” he said. Accurate data would be needed to know how many bores the aquifer can support without unacceptable impacts on groundwater dependent ecosystems and other uses such as public open space.
Dr Smith said the biggest threats to Perth’s groundwater are seawater incursion into the aquifer, the loss of valuable wetlands, and soil and groundwater acidification.
The report used 10 years of existing historical data gathered between 1995 and 2005 to provide information on what the investigation team called “freshwater thickness” at 543 sites within the ‘superficial’ or shallow aquifer under Perth.
“Using data available, we thought there was enough information to be able to do a reasonable job of estimating the trends. We did some statistical analyses to see if there’s a rising trend or a falling trend that was statistically significant,” he says.
Dr Smith’s team found that the water level was stable beneath only 14 per cent of the study area. It was falling beneath more than 40 per cent of the area, and rising below just one per cent.
The research team said a problem with the research was that it covered just over half of the greater Perth region. A lack of historical water level data prevented the team from making an assessment of the remainder of the field. Another problem was that the assessment of the information did not provide any information relating to “cause and effect”.
Bores a good move
Urban magazine spoke to Dr Smith shortly before publication (September 07) to update the situation, but he says since the report was issued in June 2006, the exercise has not been repeated or updated in any way, and so he is unable to say if there has been much change since then.
“You can imagine that if we are looking over a ten year period and we add another year or two onto that, it’s not going to change the results too much.
"We do have a project that should start either late this year or early next year where we will go back and repeat the exercise and cover a larger area, but that doesn’t alter the current state of knowledge,” he says.
Looking at Perth’s total water supply, he says the hills catchment area is now possibly supplying only 15 per cent. The desalination plant at Kwinana is making a contribution he says, but the remainder of the water, about 80 per cent, is coming from ground water through Perth Water Corporation wells that tap into both the shallow or ‘superficial’ aquifer and into the much deeper confined aquifers hundreds of metres under the city.
The move in recent years to encourage Perth people to sink their own bores has undoubtedly been a good move.
“If we are using large amounts of ground water for public water supply that is treated to drinkable quality and then piped to households to be sprayed on the lawn – wouldn’t it make more sense to cut into the resource locally and preserve the treated water for consumption? That was the thinking behind the move to bores.”
But he says there is still a need for water conservation, and the issues surrounding bore use include the question – do people actually use more water overall when they put a bore down?
“Is the only conservation result the fact that people use less metered water, but more water overall is taken out of the total aquifer system?”
He says just recently the Perth Water Corporation has began an advertising campaign, setting out the number of days and hours per day that are appropriate for lawn and garden watering from bores.
“The other issue is that the bores are an unlicensed supply of water – you don’t need a permit to put one down. And so no one knows exactly how many there are, although lately there has been an attempt to make some estimates based on information from Water Corporation meter readers who notice whether bores that have been installed in a particular neighbourhood.
“But the fact remains there’s a huge reliance on ground water for Perth’s water supply and there’s no accurate information on the effects. At least with the hills water supply there is accurate monitoring. You can go online and see the level of water in the dams, how much stream flow there’s been and so on.
“But the biggest reservoir is under our feet and we don’t have the same information on which direction the storage capacity is going. It’s fundamental that we need a good source of information before we make big decisions about its use.”