Perth has just experienced its second driest winter in 150 years of reliable rainfall records. Streamflow into dams has been negligible. You might think this would engender some panic in the city, but it hasn’t. Rationing of water is fairly modest given the circumstances. Households will only be permitted to turn on sprinklers once per week until Christmas. Hand watering is unrestricted.
The reason for the lack of panic is that the reality of climate change has been long recognised by policy makers and governments in Western Australia. In the years 1911-1975 the average annual streamflow into Perth dams was 360 GL. From 1975-2009 the average was 160 GL and this year it has been nearly zero. Perth has come to rely mostly on artesian water from acquifers a thousand meters beneath the sandy plain that the city sits on, and desalination. The first desalination plant has been running at its capacity of 45 GL per year since its completion in 2006 and the second plant will deliver another 50 GL per year from 2011 (hence the absence of panic). The later plant has approval for expansion to 100 GL. Since the streams are delivering less and the acquifer is being pumped out at an unsustainable rate, Perth will inevitably go to an all desalination model of water use (or largely desalination).
And why not? Desalination is not so expensive in the full scheme of things. The capital cost of desalination plant per person in Perth is about $1600 per person (average water useage of 300 L per person per day and capital costs of $15 million per GL). The Government is thinking of spending about $500 per person on a new football stadium. The total cost of producing desalinated water, including the costs off-setting CO2 output is less than $2.50 per kL. I will be happy if Perth goes to an all desalination model and charges users the full cost of producing water. Perth is growing faster than any other major city in Australia, but there is no more concern about running out of water than running out of electricity (which actually is a worry).
The other day I was lucky enough to be seated next to Dr Jim Gill on a flight from Melbourne to Perth. Dr Gill, who is now the Chancellor of Curtin University, was formerly the head of the Water Corporation in WA for 15 years until 2008. He is a terrifically interesting person who has an expert knowledge of desalination having presided over the building of Australia’s first major desalination plant. I have been collecting vignettes which show how little energy is used in the desalination of water and Jim Gill told me the following one. In Perth the average increase in the temperature of shower water in its journey from the water main to the shower head is 20C. The electricity used to desalinate water is only enough to heat the water about 3.5C. So, for shower water that is desalinated and then heated in an electric hot water heater, the desalination accounts for only about 14% of the energy used. My mental calculation is that desalination corresponds to a 5C increase in the water temperature, but Dr Gill was adamant that it is 3.5C, and he has a PhD in engineering from Cambridge and has actually built a desalination plant, so I believe him.