Earth is a blue watery planet.
70% of its surface is covered by oceans of salt water, some of which are extremely deep. These oceans contain about 97% of Earth's water. Another 2% is locked up in snow, ice caps and glaciers. That leaves just 1% of Earth's surface water in inland seas, lakes, rivers and dams. We have plenty of water, but not much to drink.
In addition to these vast surface water supplies, water vapour is the fourth most abundant gas in the atmosphere, after nitrogen (76%), oxygen (21%) and Argon (1%). Moisture in the atmosphere varies from almost zero over deserts and ice caps up to 4% over the wet tropics. (Carbon dioxide is a miniscule 0.04%).
Then there are the large and unmeasured supplies of hidden underground water – "renewable" water from rain soaking into alluvial sands and gravels; artesian water in deeper permeable rocks; hydro-thermal water associated with volcanic and igneous activity; and primary water originating deep in Earth's crust which feeds many natural springs and is sometimes discovered in unexpected places in very large quantities.
With this abundance of water, why do humans ever find themselves short of fresh water? Three reasons – insufficient water is conserved when it is abundant, too much water is wasted, and power costs make desalination unattractive.
The biggest water-wasters are those towns and cities which supply unlimited free or subsidised water to large and growing populations. Everything supplied "free" is wasted. Then when drought comes and water is most needed, it must be rationed. Under-priced or free water will be wasted watering lawns and golf courses so they can be mowed again, sprinkling decorative gardens, supplying fish ponds and water features, washing cars and footpaths, filling swimming pools, indulging long showers, and ignoring dripping taps and leaking pipes. If every user in every town and city were metered, and had to pay the full cost of water, it would be used much more carefully.
For example, back in the 1980's, the Central Queensland coal town of Moranbah, water was un-metered and water was supplied "free" by the coal company. But in droughts Moranbah water had to be rationed – gardens one side of the street could use water today, the other side tomorrow. Another town, Dalby, in the same climatic district was metered and self-regulated. No watering restrictions were imposed. The water consumption per resident in Dalby was half that of Moranbah (and gardens were just as good).
How should we charge for water? "Charge what it costs" sends the right signals to users. Maybe each user should pay a fixed base charge for water to cover essential needs. This should be related to the capital costs of the water infrastructure. Usage above this should be charged at a variable rate which would increase as the water levels in dams dropped. This would remove the need for water restrictions and generate public support for building more dams.
"The Lucky Country" also has a "Great Artesian Basin" and many grazing properties and inland towns have relied heavily on artesian water that flows to the surface from deep bores. Again this "free" water has been badly wasted by allowing the bores to flow unchecked into open bore drains subject to heavy losses by evaporation and soakage. There is a program to case and cap these bores to reduce wastage. Some of the government funding frittered on global warming "research" and green energy gambles would be better devoted to conserving artesian waters.
Some places like Perth in Western Australia with low rainfall and high evaporation rates have made good use of artificial desalination plants, but desalination is generally the last resort without abundant cheap electricity.
The nuclear energy of the sun powers the greatest desalination plant on earth using mainly sea water to create all of Earth's clouds, rain, hail and snow. Unfortunately it delivers these products in cycles of floods and droughts. Therefore dams are needed to improve water security in droughts, and to moderate the severity of floods.
Water storage is an important part of the water equation which every farmer understands. There is no point allowing immense floods of fresh water to erode the land and spew into the seas – the oceans are not short of water (but offshore sea life like prawns and corals can benefit from nutrients and minerals delivered offshore in floods).
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