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Water availability and quality

Facts about water on Earth•Oceans cover 71% of the Earth’s surface

•Oceans and seas contain 97% of all water on Earth

•Only 3% of water on Earth is fresh water.

•Most of this 3% is in ‘deep freeze’ – in ice sheets.

Fresh water is a vital natural resource for all life on Earth. However, only 3% of the water on Earth is fresh water and most of this is not available for human use.

Global fresh water stores

75%

23%

2%Ice

Groundwater

Lakes, Soil,Rivers,Atmosphere

Globally, fresh-water supplies are abundant, despite the low percentage of available fresh water.

Precipitation is constantly replenishing natural stores by filling rivers and lakes and topping up underground stores.

The main problem is one of uneven distribution among and within countries.

In order to assess fresh-water availability in a country, 2 factors are taken into account:

1. The amount of renewable fresh-water resources per year (from precipitation and from rivers flowing in from other countries).

2. Population size.

The majority of the water-rich countries are in the hot, wet tropics. The most water-poor countries are located in the desert lands of the Middle East and the northern half of Africa.

Many of these countries rely on aquifers (underground stores of water trapped in layers of pervious rock) or great dams, such as the Aswan High Dam on the River Nile in Egypt.

Some water-poor countries are already suffering from severe water shortages, which the UN refers to as water stress. By relating water availability in a country to its water consumption, the organisation estimates that one in three of the world’s people lives in a country already experiencing moderate to high water stress.

The UN believes that the world’s thirst for water will become a pressing resource issue during the 21st century. Global water consumption is rising at twice the rate of population growth. Much of the new demand is from LEDCs, for a variety of reasons:

•Higher population growth than in MEDCs

•More water used for irrigation to meet rising demand for food.

•Traditionally low domestic demand is increasing with economic growth.

•Industrial and urban expansion is occurring, notably in China and India.