Black gold became a fashionable term for oil when the gas-guzzling West sat up and took note of rapidly diminishing reserves of the precious fossil fuel. No wonder, then, that water should now receive the moniker of blue gold; as the Chairman of Nestle, Peter Brabeck-Letmathe, has repeatedly claimed,
We will run out of water before we run out of oil 
Unless NASA finds aliens on Mars or Europa, the Earth will remain unique in sustaining life and we owe this privilege to water. Earth is the blue planet because 70% is covered in ocean. Indeed, 97% of Earth’s water is saline. Which leaves a mere 3% for managing activities essential to life such as drinking and growing food. A problem then, and a growing problem, that the population is already 7.4 billion and estimated to hit 9.7bn by 2050. 
Ideas abound as to how to address this situation. White goods manufacturers have developed machines that wash our clothes with fewer litres, tiny robots with magnetic sensors are sent into piping systems to detect leaks, streets are cleaned with ‘grey’, non-potable water and Israel and the UAE have been tinkering for the past decade with cloud-seeding – the introduction of crystals, usually silver iodide, into clouds in order to cause rain.
One solution, dating back at least to 400BC and quite possibly beyond that , is the process of desalination – removing salt from sea water – which, in the past 60 years, has become a popular, though costly, means of providing drinking water to arid areas such as the Middle East, Australia and Spain. The modern process is not without its critics as it is energy-intensive and produces a lot of residual brine which is difficult to dispose of satisfactorily but strides are being made to find renewable power sources to address these issues. 
Education has improved and fewer people now leave the tap running as they clean their teeth. However, little noise is made about the water we all use each day as we go about our electronic communications. In 2015, researchers at Imperial College, London, calculated that up to 200 litres of water could be used, evaporated or polluted in the production of each gigabyte of data. That is equivalent to using the water from six loads of washing in a modern, efficient machine, to produce the data that most European smartphones get through in a fortnight.
The problem lies with data centres, the vast engines driving the ever-faster, ever-increasing supply of information that modern life has come to rely on. These huge factories, filled with servers, are kept cool by water. Lots of it. Countries such as Iceland have successfully marketed themselves as ideal locations for off-site data centres since they require little extra energy to keep water cool; Facebook has a data centre in northern Sweden.
In a bid to become yet more environmentally-conscious, Apple has pledged that all its data centres will be powered by renewable energy. Microsoft, meanwhile, is experimenting with underwater data centres, letting the ocean do the cooling. So it could be that the oceans provide another solution to our thirst for water, just as they did in Aristotle’s day.
 CNBC. Nestle Chairman: Time to turn off the water taps. 24 March 2015. www.cnbc.com
 United Nations. World population projected to reach 9.7 billion by 2050. 29 July 2015. www.un.org
 Aristotle. Meteorologica
 Clean Technica. Tiny solar thermal power plant solves gigantic salt problem. 18 February 2014. www.cleantechnica.com
 Imperial College, London. Download less: save water! 19 August 2015. www3.imperial.ac.uk