While we are always reminded in the media about the questions of energy security, water resources are equally important and increasingly linked to energy in what became known as the energy water nexus, or how much of each is needed to make the other available.

For the greater part of energy production water comes in as a very important input. It is necessary for oil fields development not only for drilling but to maintain production later and more is needed when enhanced oil recovery is practised. The World Energy Council (WEC) estimates an average of 40 barrels of water needed for the production of one barrel of oil. In today’s increasingly practised shale oil and gas development and oil extraction from tar sands or what is known as unconventional oil and gas, WEC estimates 90 to 150 barrels of water for each barrel of oil. The list goes on as four cubic metres of water are needed for every tonne of coal produced and in biofuel production the ratio is staggering at 1,100 litres of water for a litre of ethanol.

In electricity generation, thermal power stations in the US use 143 billion gallons of water every day, three times more than that used in public water supply and even more than irrigation use. Even hydroelectric power plants “consume” water due to the evaporation in the reservoirs that feed them. Therefore a shortage of water can inhibit the production of electricity or more energy is needed to bring water from far away sources.

In petroleum refining, gas processing and the petrochemical industries large volumes of water are needed for cooling the products while also substantial amount of steam is required to drive machinery or for heating purposes. Water treatment processes in these facilities are complex especially if the water source is of low quality.

Turning to water, we know that 75 per cent of the globe is covered with water which gives the impression of plentiful supply. But 97.5 per cent of that water is salty sea water while only 2.5 per cent is fresh and the majority of that or 70 per cent is locked in ice caps in the poles or mountain tops and glaciers. Readers may be surprised that rivers and lakes, as important as they are, only provide 0.3 per cent of the fresh water and the rest comes from underground water.

While total water resources are renewable, the increasing use of water for human consumption, irrigation and industry is putting pressure on the readily available resources and forcing governments to seek others.

Industry is the largest user of water resources and the energy industry is the most intensive user among all. It is safe to say that there will be very little energy industry without water but at the same time there will be no usable water without the use of energy.

Water has to be delivered to users by pumping it from its sources and sometimes transported by pipelines for a long distance. Water treatment to get rid of impurities is very extensive especially if the source is of low quality. Industrial water treatment in power plants and other energy facilities are even more complex. All these operations require energy such that in the US, the transportation and purification of water consumes 4 per cent of all electricity while in California, water related energy use, consumes about 19 per cent of the state’s electricity, 30 per cent of its natural gas, and over two million barrels of diesel fuel every year.

Faced with the scarcity of water, some regions such as ours resorted to large scale sea water desalination using large amounts of energy and specialised and expensive plants. In 2009 14451 desalination plants operated worldwide, producing almost 60 million cubic metres per day and expected to increase to 120 million cubic metres by 2020. It is not surprising that some 40 million cubic metres capacity is planned for the Middle East and that the world’s largest desalination plant is in Jebel Ali.

To improve efficiency and reduce energy needs, desalinations plants are generally integrated with power stations such that the waste heat from power generation is used for the desalination. The cost of desalination has gone down such that it is around half a dollar per cubic metre of water now.

The linkage between energy and water is now well established and water security should receive the same attention if not more than energy security. Energy and water policies and plans should be viewed in an integrated manner to improve the efficiency of use of both. Energy conservation has been a great success in the last 40 years and water conservation is yet to be given equal regard especially with the expected increase of world population and its consequent economic growth.