The Chart below shows the percentage of river water in the UK rivers classified as having good chemical quality between 1990 and 1992

The Chart below shows the percentage of river water in the UK rivers classified as having good chemical quality between 1990 and 1992

The given line graph elucidates and compares the river water in Wales, Scotland, Northern Ireland and England between 1990 and 2002. 

Overall, patterns of changes in chemical qualities of water were dissimilar in all states, except in the case of Wales and Scotland,  which stayed constant up to 1998. Furthermore, the quantity of good chemicals increased in all provinces, but in Wales it declined. And in Scotland and Ireland, the percentage of good chemicals was the highest  in 2000. 

In  1990 the ratio of good chemicals in water in Wales was approximately 96% and 95% in Scotland. These proportions remained stable from 1990 to 1998, but after that while there was a decline to nearly 94% in the former, the latter saw an increment nearly 97%. Moving further, even though Northern Ireland witnessed a fall from almost 93% to about 83% with a fluctuation, saw a steam rise in 1996 and 2002, reaching at power with Scotland. England, although the lowest, saw an incline from 82% to 90%.