Our Precious Drinking Water !

If the pundits are right, one of the aspects of global warming will be a reduction in the rainfall pattern across Australia. Much of New South Wales at present is either in drought or starting to recover from one of the driest periods in history.  The television news has featured huge convoys of hay trucks bringing in feed from other states to try and keep sheep flocks and cattle herds alive in their parched paddocks.

This week Sydney faced the ominous news that the mothballed desalination plant at Kurnell was being reactivated.   This is an automatic decision when the level of Warragamba dam falls to sixty percent of capacity.  It ticked over 59.9% over the long weekend.   The plant was built in response to the Millennium water shortage at a cost of  $ 2.3 billion.   It ran from 2010 to 2012 during its last operation and ensures that Sydney will never completely run out of drinking water.

A desalination plant take salty water from the sea and runs it through a process called reverse osmosis.  What emerges is fresh water that is then treated to reach the standards contained in drinking water guidelines and has a small amount of  fluoride added to prevent tooth decay.   This plant has the capacity to produce  250 million litres of drinking water per day and that is about one sixth of Sydney's entire needs.

Obviously, the cheapest water is that stuff that falls from the sky and running the desalination plant will increase the average water bill by about thirty-five dollars a year, but that input will make the water stock contained in Warragamba dam last years longer as water rationing reduces wastage by hosing pathways and keeping lawns green.

We are seeing an emerging water problem in the towns of inland Australia.  Civilized communities demand reticulated water and it is obvious that our inland river system can not deliver the quantity being drawn for both household use and crop irrigation.   As the taps run dry we are facing a problem that global warming is likely to exacerbate.

The original farming families practised water conservation.   Their water supply depended on the rain falling on their roof being collected in water tanks and this was carefully used.  The family bath routine was often on a weekly basis and water for stock use was often carted from the nearest river.  The great Australian artesian basin delivered bore water that eased that problem but today too much is being drawn from that source.

It seems likely that many coastal cities will need to install desalination to meet their water needs because we are well served by the surrounding sea, but inland Australia can not continue to consume water at the present rate and change is necessary.  We are fortunate that our tropical far north is served by the annual monsoon and we need to design and construct water retaining schemes so that more of this water can be retained and pumped south to renew the inland river system.  It will be costly but that is the only way the inland river system can be made sustainable by way of regulated output and an enhanced flow to serve all the states reliant on the rivers for water.

Such a water retention scheme in the far north could become our premier engineering project for the balance of this century.