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Water scarcity

By Michael Smith
NBS Information Specialist

Water is an essential resource for life and good health. Not having enough water to meet basic daily needs is a reality today for one in three people around the world. Globally the problem is getting worse as cities and populations grow, and the needs for water increase in agriculture, industry and households. Currently there are around 2.4 billion people worldwide who do not have adequate access to sanitation; with demand for water growing twice as fast as the global population.

Water scarcity already affects every continent. Around one-fifth of the world's population, live in areas of physical scarcity, and a further 500 million people are approaching this situation. Another quarter of the world's population, face economic water shortage (where countries lack the necessary infrastructure to take water from rivers and aquifers). Water scarcity is both a natural and a human-made phenomenon. There is enough freshwater on the planet for everyone, but it is distributed unevenly and too much of it is wasted, polluted and unsustainably managed. The average Briton directly uses about 150 litres of water a day, but taking into account the water involved in producing the food and drink we consume and the products we buy, the figure is more like 3,400 litres per day, according to Waterwise. Globally, about 65% of water use is embedded in food.

Water demand in Europe

While most of Europe is considered as having adequate water resources, water scarcity and drought is an increasingly frequent and widespread phenomenon. The long term imbalance resulting from water demand exceeding available water resources in the EU is no longer uncommon. It is estimated that by 2007, at least 17% of Europe's territory had been affected by water scarcity, putting the cost of droughts in Europe over the past thirty years at over €100 billion.

It is expected that further deterioration of the water situation will occur as a result of climate change. While agriculture makes up about 70% of total water demand, the increase in urbanisation and higher incomes has also lead to a need for more water and higher standards. Unfortunately climate change affects rainfall trends, causing water shortages as well as floods. In the UK recent years' extreme weather events seem to happen more often and be more severe.

The main overall objective of EU water policy is to ensure access to good quality water in sufficient quantity for all Europeans, and to ensure the good status of all water bodies across Europe. Therefore, policies and actions are set up in order to prevent and to mitigate water scarcity and drought situations, with the priority to move towards a water-efficient and water-saving economy.

Water stress versus water scarcity

Hydrologists typically assess scarcity by looking at the population-water equation. An area is experiencing water stress when annual water supplies drop below 1,700m³ per person. When annual water supplies drop below 1,000 m³ per person, the population faces water scarcity, and below 500m³ per person ‘absolute water scarcity’.

Water scarcity is defined as ‘the point at which the aggregate impact of all users impinges on the supply or quality of water under prevailing institutional arrangements to the extent that the demand by all sectors, including the environment, cannot be satisfied fully‘. Water scarcity is a relative concept and can occur at any level of supply or demand.

Water scarcity may be a the result of social factors (a product of affluence, expectations and customary behaviour) or the consequence of altered supply patterns (for example, climate change).

What is Drought?

Droughts can be considered as a temporary decrease of the average water availability, usually due to a rainfall deficiency. Droughts can occur anywhere in Europe, in both high and low rainfall areas and in any seasons. The impact of droughts can be exacerbated when they occur in a region with low water resources or where these resources are being improperly managed, resulting in imbalances between water demands and the supply capacity of the system.

Over the past thirty years, droughts have dramatically increased in number and intensity within the EU. The number of EU areas affected by droughts went up by almost 20% between 1976 and 2006.

European strategy for water scarcity

Based on information from the Member States and its own research, the European Commission prepares annual follow-up reports on the initial 2008 Review of the strategy for water scarcity and droughts that assess the implementation of water policy options throughout the EU. The 2010 follow-up report presents the water management measures introduced by Member States to tackle water scarcity and droughts and highlights the areas for further action. The report confirms that water scarcity and drought is not limited to Mediterranean countries and that, apart from some sparsely-populated northern regions, this is a growing issue across the EU. The Commission will further address this growing challenge in a review of EU water scarcity and drought policy which will form part of a ‘blueprint’ for safeguarding Europe's waters, scheduled for 2012.

UK national efficiency measures

Future water, the government's water strategy for England was published in February 2008 and sets out a vision for the water sector by 2030. The strategy maps out how the overarching target of reducing domestic water usage to 130 litres per person per day, can be achieved.

The current government is also committed to working with the European Commission to improve the water efficiency standards for appliances such as washing machines and dishwashers, under the mandate of the energy using products (EuP) directive.

Virtual water trading schemes

In Australia water-trading schemes similar to the EU's Emissions Trading Scheme have been established to encourage more efficient use of water.

The concept of virtual water is one that is gaining currency, putting a new perspective on the sustainability of individual products and of production processes. Utilising virtual water means that all businesses will have to take into account water use in their supply chains. For example oranges from the US, contain about 175 litres of embedded water per kilo, but oranges from Australia contain more than three times as much; Indian steel uses around 10,000-80,000 litres of water to produce a tonne of product, compared to 5,000-10,000 litres for the same amount of American steel.

Purifying seawater

The cost of desalination plants, worldwide, is seen as a great barrier to this technology and many countries consider it cheaper to pump water out of existing aquifers. Most of our planet comprises seawater and with a salt content of about 3.5%. This needs to be reduced to 0.5% (or less) to make it potable.

Older purifying processes used distillation, which requires about 10kWh of energy per cubic metre (m³) of seawater. The seawater is heated up and the resulting water vapour is condensed into drinkable form.

A more recent method, reverse osmosis, uses semi-permeable membranes to sieve out the sodium and chloride ions and only pass the fresh water through. The electrical cost of processing to accomplish this is about 4 kWh per m³ of salt water, considerably less than distillation. However, careful maintenance of the molecular screens is required to prevent fouling from pollutants and sea creatures.

Solar desalination, which is essentially free, uses the sun to heat a volume of water, which causes evaporation. The fresh water recovered drips into a collection system. The limitation here is that there is a theoretical maximum amount of water that can be evaporated by the sun in a given area.

Another rather clever process, called electrodialysis, pumps seawater through a series of channels with membranes which are dedicated to collecting either sodium or chloride ions when the appropriate voltage is applied. The water is repeatedly passed through this process until its salt concentration is reduced to below 1%. An ion-exchange resin is then used to bring the salt concentration below 0.5%. The energy required to do this is about 1.8kWh per m³; a dramatic reduction on the other methods available.

Low cost savings

On a smaller scale, there are many simple, low and no cost, ways of increasing water efficiency, both in business and domestically. These mainly focus on fixing dripping taps and installing water saving devices, as well as utilising rainwater harvesting.

Both the Environment Agency and Waterwise offer tips on saving water at home, in the garden and at work, all of which take very little effort. As an example of easily solvable water wastage, it has been estimated that a leaking tap, dripping two drops of water per second, could waste nearly 10,000 litres of water per year.