The river water
quality indicator is one of the 68 indicators of the Government’s Sustainable Development Strategy. It separately measures biological and chemical river water quality on an annual basis and the indicator for each represents the proportion of river water, in terms of river length, which is considered to be of “good” quality.
Headline results
In England:
72 per cent of river length was of good biological quality in 2008, the same as in 2007 and 2006.
79 per cent of river length was of good chemical quality in 2008, up from 76 per cent in 2007.
In Wales:
88 per cent of river length was of good biological quality in 2008, up from 87 per cent in 2007.
95 per cent of river length was of good chemical quality in 2008, the same as between 2005 and 2007.
To read more click the link
http://www.defra.gov.uk