The line graph shows the changes in the shares of high-quality water in four UK rivers, Wales, Northern Ireland, England, and Scotland, from 1990 to 2002.
Overall, while the figures for rivers in Northern Ireland and Scotland exhibited rising trends over the study period, the reverse was true for England, which remained almost unchanged, and Wales. It is also clear that the proportion of good-quality rivers in Wales and Northern Ireland showed relatively bigger figures.
The percentage of quality water in rivers of Wales and Northern Ireland showed much bigger figures than the remaining categories, with the former remaining stable at around 95% and the latter levelling off at approximately 85% prior to 1998. The figures for Wales decreased sharply from about 95% in 1998 to 80% in 2002. In contrast, the proportion of good-quality rivers in Northern Ireland recorded a high of 100% in 2000, surpassing Wales. A figure that then saw a marked decline to just below 100% in the final study year.
By contrast, the figures were smaller for the remaining categories, albeit with varying points. In 1990, the shares of good-quality rivers in England made up around 45%, before growing gradually to just under 70% in 1996. That growth, however, was not maintained, and later it dwindled sheerly to 30% in 1998. Despite falling in 1998, the figures for England began to go up, ending the study period at 50%. Starting at the lowest point in the chart (20%), the proportion of quality water in the rivers of Scotland increased slightly to 30% in 1992 and remained unchanged until 1996. By 1996, there was a dramatic rise, reaching its peak 60% in 2000, after which it fell by 20% in 2002.