An alternative approach to extending water resources is by water conservation. Different methods of water conservation exist such as:
Efficient water use
Recycling water
Water substitution
Changing practice
One method of water conservation is to use less water, more efficiently. In countries where water is available at the turn of a tap, water is wasted in many ways - by water-inefficient appliances and unaware users.
Industry may also use water inefficiently, and so does most irrigation, where water is transported to fields through unlined, uncovered canals, and used in surface furrow irrigation. Changes in technology can be used to reduce inefficient water use.
Recycling water can also extend the available water resource. For example, power stations are often major users of water to cool the steam that has driven the turbines. This steam is produced from very expensive demineralised water, so recycling it makes economic sense.
Another method of water conservation is water substitution - using alternatives instead of water. On a global scale this will make little difference, as most water (70%) is used for agriculture, mainly for irrigation, which is a non-substitutable use. However, on a local scale, particularly for many industrial purposes, substitution is possible.
For example, power stations can use a ‘dry’ cooling tower instead of the ‘wet’ cooling tower. However, this substitution comes at a cost; wet towers cost about US$20 million each, whereas dry towers cost about US$35 million, and a major power station usually has between six and eight of these towers.
The last, and most fundamental, conservation technique is changing practice - to change from a water-consuming practice to one that uses less or no water. On a small scale, for example, homes in areas of low rainfall could use only desert plants in their gardens, requiring no watering.
On a larger scale, a change for industrialised countries in their consumption of food, to a diet including more cereals and vegetables and less meat, may reduce the water used for agriculture, as it requires far more water per kilogram of meat protein produced than it does for cereal or vegetable protein.
Have been noted.