The line graph compares river water in four different parts of the UK in terms of chemical quality over a 12-year period starting from 1990.
It is, overall, evident that all the regions with the exception of Wales underwent some positive changes in water condition. The irony is that water quality in rivers in Wales and Northern Ireland was at the top of the chart all over the period.
Starting with the areas experienced upwards trends, Northern Ireland and Scotland, proportions of water quality there were well-over 90% and just-under 20%. Having been increased to 30%, the figures for the latter began to stay constant in 1992 at which point the former saw a long term plateau. In 2000, a growth of around 30% was seen in the quality in Scottish rivers while that of roughly 10% was recorded in the other region. By 2002, index had reached its final point for both areas, accounting for 40% and approximately 95% in turn.
As for downward trends, they can mainly be seen in Wales and England. Even though water quality in Wales rivers had good chemical quality (95%), that in England was a complete reverse, showing about twofold difference. Maintaining the same figures until 1994, the index of England peaked at just-under 70%. Albeit a stability was observed in the water quality in Wales in 1998, that year saw a decline in the other region, constituting as low as 30%. Coming to the final years, the figures went to opposite directions, staying at about 50% and 80% respectively.