By Maggie Ayre
BBC Costing The Earth
The Australian of the year 2007, environmentalist Tim Flannery, once predicted that Perth in Western Australia could become the world's first ghost metropolis, its population forced to abandon the city due to lack of water.
People in Perth use more water than any other city in Australia
While some critics scoffed at this idea, there is no doubt that it has forced the city to wake up to the fact its water is running out and that it can no longer rely on its natural supply.
Australians are some of the world's greatest energy consumers, and people in Perth use more water than any other city in Australia.
Yet theirs is also the driest climate in the world, and Perth sits right on the edge of a vast desert, an island of greenery in the form of European style parks and gardens.
The city's case is a fascinating paradox of over consumption matched by a dawning awareness of climate change that is resulting in an urgent response to safeguard the city's water supplies for the future.
Perth sits above a vast ancient aquifer of 40,000-year-old water that has traditionally been the main source of drinking water. But in the mid 1970s there was a dramatic shift in climate that resulted in a decline of between 15% and 20% in winter rainfall.
The combination of rising temperatures and a lack of wet winters has meant a steady decline in water levels in the aquifer and they are not being recharged.
By the mid 1990s, scientists realised they were facing more than a prolonged drought, that this was in fact climate change.
Don McFarlane, of the Commonwealth Scientific Industrial Research Organisation (CSIRO), says: "Climatologists tell us that it is the most profoundly affected city in the world. People have accepted that it is climate change.
"In other parts of the world people are thinking it's something that's going to happen to them in the next 10 or 30 years and that they've got time to adjust. We've found we've been living with it for 30 years now and we're having to adjust very quickly."
City of industry
Although perhaps the residents of the city have been slow to respond to the threat of climate change, there has been intense pressure on water experts to find new sources of water for the city.
Perth is growing rapidly thanks to its thriving mining industry and the population will soon top two million people, attracted there by a high standard of living.
Australia as a whole is facing a water shortage
The city is made up of suburbs that stretch for more than 70km along the coast of the Indian Ocean.
People consume a lot of energy. It is a car-dependent city with little public transport. Many of the luxury houses overlooking the ocean (known locally as "starter mansions") boast currently fashionable black roofs that soak up the heat in temperatures of up to 42 degrees in summer, and produce a greater need for air conditioning inside.
And, ironically, although it's a desert climate, Perth prides itself on being a garden city, boasting vast expanses of beautifully kept lawns and parks complete with water hungry plants and flowers.
And many residents can extract water for these gardens directly from the aquifer. There are over 150,000 unlicensed boreholes in Perth's back gardens that allow householders unlimited access to groundwater for watering.
Yet the Water Corporation is reluctant to clamp down on private water usage even though before current restrictions people were often watering their gardens in the middle of the day when the water was most likely to evaporate and be wasted.
One gardener we spoke to for Costing the Earth told us that 90% of his water usage is for his garden and that it would break his heart if he ever had to stop watering and give up his beloved green lawns.
But Pierre Horwitz, associate professor of ecosystems at Edith Cowan University, Perth, questions why drinking water is being used for gardens to such an extent and says people have got to start using less water.
"If you compare our individual consumption rates, they're almost a third higher again than those in Sydney, Melbourne and Brisbane. You just can't continue to sustain that."
Horwitz says people have been too complacent about the availability of water because of the vast ground water resource.
"We're actually mining water. This is a non-renewable resource and we have to constrain our behaviours so that we use what's replenishable rather than eat into our reserves."
Following this early wake up call to the onset of climate change, Perth's water experts are now leading the way in exploring new ways of providing water for this thirsty city. One of them involves recharging the aquifer with treated waste water - left over from people's washing machines and dish washers.
There is plenty of it available because of the increasing population. Until now, most of it has been going straight out of the kitchen into the ocean. That is 111 billion litres of "wasted" waste water.
That water is now being put into some of Perth's lakes to be treated naturally in the soil before topping up the groundwater in the aquifer.
At the moment, it is not going to be used for drinking water but for irrigation and in the lakes for the benefit of wildlife; but there are concerns about potentially harmful effects on the environment, which scientists are monitoring very closely.
Research scientist Simon Toze says: "The biggest impact for the environment are nutrients which could cause algal blooms. Also, trace chemicals like hormones, things we excrete. We know most nutrients are taken out naturally by processes. We don't know so much about the trace organics."
There are well documented concerns about the so called "gender bending" hormones in water causing fish to change sex, but Toze says that so far results seem to show that things like oestrogen are stripped out during the bio processes taking place in the aquifer.
Sometime soon though, the citizens of Perth could be looking at drinking recycled water, and currently Toze and his colleagues are doing a lot of work to try to persuade people to get over what they call "the yuk factor".
He says that the recycled water would remain even longer in the aquifer to allow nature to remove any harmful nutrients, possibly for up to 50 years, before being used for drinking water.
Toze claims by then it would be pure to drink, better than what comes out of our taps at the moment. This is one solution to Perth's water crisis, although it may not be the most popular one.
There is a joke doing the rounds that goes: the good news is we'll all soon be drinking recycled sewage. The bad news is there will not be enough to go round. These may be desperate times for Perth's water supply, but the city is in the fortunate position of being fairly wealthy with a government that is prepared to invest in expensive water projects.
The latest is a state of the art desalination plant that came online last November and will supply 17% of the city's drinking water.
It is partly powered by a wind farm further up the coast and the city's Water Corporation claims it is the most efficient and environmentally friendly of its kind anywhere in the world.
Gary Crisp, the corporation's desalination engineer, is proud of their achievements: "What we've done [in Perth] is truly pioneering stuff.
"There's no one else really to help us so we have to bite the bullet and do the job ourselves."
However, he does concede that, ultimately, Perth is going to have to pay more for its water.
"At the current prices in Australia, there's not enough water to go around and there's not enough incentive for people to use less."
And that is the only true solution to Perth's water crisis - learning to live with less water and maybe even giving up some of those beautiful green lawns.
Otherwise that prediction that it could become a ghost town may yet come true.
Costing the Earth is on BBC Radio 4 on Thursday 3 May at 2100, and on Friday afternoon at 1500. You can also hear the programme after it is broadcast on the Listen Again service on the Radio 4 website