The chart below shows the percentage of river water in UK rivers that is classified as having good chemical quality between 1990 and 2002.

The line chart illustrates the percentages of river water meeting good chemical quality standards, in four countries in the UK, from 1990 to 2002. Overall, rivers in Northern Ireland and Wales consistently had the cleanest water. Additionally, with the exception of Wales, all the regions showed improvements in their water quality over the period shown. […]