The line graph illustrates the changes in the proportion of water in UK rivers that met acceptable chemical quality standards from 1990 to 2002, covering a 12-year period. Overall, the percentage of water in rivers from Northern Ireland and Scotland showed an upward trend, while England experienced a slight increase. However, the situation was different for Wales, which exhibited a decrease. Notably, throughout most of this period, Wales had higher quality figures compared to Scotland, which consistently had the lowest quality water.
Looking at the increases first, the percentage of quality water in Northern Ireland started at over 85% in 1990. This figure grew slightly to around 89% in 1996, surpassing that of other regions, and made it the best quality river by 2000. Wales also recorded the best quality in 1998, but by 2002, the water quality in Wales decreased significantly.
In contrast, England saw a decline to 30% in 1998, but then increased from 45% in 1990 to 50% in 2002. By 2000, the percentage of quality water in Scotland rose to 60%.