To say the world is on the brink of water shortage is somewhat misleading. Approximately 70 per cent of the earth’s surface is covered with it. However, almost all of it (97.5 per cent) is found in oceans and so is too salty for use in agriculture or for drinking.

Of the fresh water that remains, more than two thirds is locked up in glaciers and permafrost. So, less than one per cent of the planet’s total water is accessible and fresh.

Couple this with population growth over the last few decades and the demands on that one per cent are dramatic. There are now seven billion of us on the planet and by 2050 this is projected to be nine billion.

As a result, the area of land worldwide under irrigation has doubled and the amount of water used for farming has tripled. This huge increase in demand could mean that four billion people will be living in countries chronically short of water by 2050.

The next problem is that the usable water is not very conveniently distributed. Sparsely populated regions such as Siberia and Canada are rich in fresh water, whereas parts of east Africa are dependent on seasonal rains.

Urbanisation is another issue. In 2008, for the first time more people lived in towns and cities than in the country. China and India are obvious countries witnessing this phenomenon.

City populations are predicted to grow by a total of 600 million during the next 20 years. Research by Citigroup Global Markets estimate that 70 per cent of the earth’s population will live in urban areas by 2050. Existing infrastructure cannot meet the needs of these cities.

However, according to scientists there is some good news for the notoriously dry continent of Africa. They argue that the total volume of water in aquifers underground is 100 times the amount found on the surface. With 300 million people across Africa without access to safe drinking water this is excellent news – provided these resources can be accessed adequately.

Rising living standards in many places is another factor for water usage. Increased demand for flushing toilets, manufactured goods and richer food also means increased demand for water. The rest of the world is certainly catching up the western as heavy water users.

After agriculture, the next biggest water user is industry. Water is used a lot in the making of manufactured good. For example, it can take up to 90 litres of water to make just half a kilo of plastic in some areas. A big issue is doing a better job of capturing and storing rain when it falls. In Britain, water utilities have long wanted to build new reservoirs but local authorities and governments have been less keen. For example, Thames Water had an application for a £1 billion reservoir turned down last year.