Rate of change in rivers classified as less than good as a percentage of the total river classified. Data shown is for different types of classification scheme, by country

Some countries have more than 1 national classification scheme and so results for each scheme are shown separately e.g. England and Wales has a chemical scheme and a biological scheme. This separation into types of scheme also illustrates that whilst one scheme may show an improvement in quality, another may show a deterioration e.g. The Northern Ireland chemical scheme showed an improvement whilst the biological scheme showed a deterioration.