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2 March 2005

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You are in: Subjects > Water Quality > Water Quality - background

Water quality

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Better waters




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Water quality - background information

Why is water quality important?

Most of the Earth’s water is in the oceans (97 per cent) or locked away as ice. The largest volumes of freshwater are stored underground as groundwater, accounting for about 0.6 per cent of the total. Only a tiny fraction (0.01 per cent) is present as fresh surface water in lakes, streams and rivers. But it is this proportion which is so important for many of our terrestrial ecosystems, including humans.

The quality of this fresh water is vitally important. We depend on surface and groundwater sources for our drinking water. We also need water to generate energy, to grow our crops, to harvest fish, to run machinery, to carry wastes, to enhance the landscape and for a great deal more. We use water for washing and cleaning, industrial abstraction, recreation, cooking, gardening and angling, as well as simply to enjoy it. Water is also vital as a habitat for both freshwater and marine plants and animals.

What causes water pollution?

Many human activities and their by-products have the potential to pollute water. Large and small industrial enterprises, the water industry, the urban infrastructure, agriculture, horticulture, transport, discharges from abandoned mines, and deliberate or accidental pollution incidents all affect water quality. Pollutants from these and many other activities may enter surface or groundwater directly, may move slowly within the groundwater to emerge eventually in surface water, may run off the land, or may be deposited from the atmosphere. Pollution may arise as point sources, such as discharges through pipes, or may be more dispersed and diffuse. Both point source and diffuse water pollution may be exacerbated by adverse weather conditions.

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©The Environment Agency 2005
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Author: Jackie Vale | enquiries@environment-agency.gov.uk