This summer has certainly highlighted the on-going water shortages faced by most Australians, whether they live in the cities or rural areas. One way or another, we need more fresh water, whether it is obtained by more careful use of our existing limited water resources or by obtaining new sources. For the cities, the problems are possibly more urgent than in rural areas which are always subject to periods of drought.

Perth has the most pressing problems, followed by Sydney, Melbourne and Adelaide. Perth has had declining rainfall over the last 30 years or so and has much reduced run-off into its dams. So Perth is taking the immediate approach of building a sea-water desalination plant, located next to the Kwinana power station. This makes sense, since it is close to the sea and the power source.

The plant will use the reverse osmosis process whereby sea-water under high pressure is applied to semi-permeable membranes to remove salt and other dissolved solids.

Reverse osmosis is the favoured process because it is one of the most energy efficient, although all desalination processes use large amounts of energy – hence the need to site the plant next to a power station.

Perth’s proposed plant has an annual capacity of 45 gigalitres or 130 million litres/day. It is estimated to cost $346 million to build and $24 million a year to run. That sounds like a lot of money but it pales into insignificance compared to the much higher cost to build the mooted pipe-line or canal from the Kimberley region in the north of Western Australia down to Perth. Not only will it cost billions to build such a pipeline but it will need some very big pumping stations to get the water from the Kimberley down to Perth.

Projections by Perth’s Water Corporation indicate that the energy cost for water from the desalination plant will be 5kWh/litre while that via the pipeline will be 15kWh/litre. Compare that with the price typically charged to domestic consumers in Australian cities – around $1 per thousand litres – and you wonder if our water shortage problems would suddenly disappear if the present water price was doubled!

Really, when you think about the large energy cost of our present water supplies, for pumping, filtering, chlorination (don’t forget the high energy cost of chlorine production), fluoridation and so on, we should be making every attempt to be frugal in water use. And maybe the water authorities could do much to foster this by increasing the price!

No doubt there will be many people who would be opposed to any increase in price for water but let’s face it, it is the most effective measure, requiring no new technology, no heavy consumption restrictions and no need for draconian policing – you use the water, you pay.

Leo Simpson