The line graph illustrates the proportion of water in rivers which are located in UK that was categorized as having good chemical quality from 1990 to 2002.
Overall, Wales accounted for the highest proportion of river water with good chemical quality, whereas Scotland had the lowest proportion. England increased slightly before decreasing sharply.
In 1998, Wales had the highest percentage of good chemical quality river water at around 97%, holding a stable top position until 1998. However, after 1998, the figure for Wales experienced a sharp drop, falling to 80% by 2002. Northern Ireland began at approximately 84% in 1990 and steadily increased, surpassing Wales in 1999 and reaching a peak of roughly 99% in 2000, before slightly dipping to about 96% in 2002.
Regarding the remaining two countries, England started at 45% in 1990 and rose significantly to peak at nearly 68% in 1996. However, it plummeted to a low of 30% in 1998 before gradually recovering to nearly 50% by 2002. Scotland initially had the lowest percentage of good quality river water at around 22% in 1990. After hovering around 30% for several years, it rose steeply to peak at nearly 60% in 2000, but then dropped sharply to end the period at 40%.