Definitions and requirements

Water quality is determined by 2 distinct elements - chemical quality and ecological quality. The former relates to substances present in the water body (e.g. pollutants) and the latter concerns the habitat and living species present in it (i.e. biology and ecology). The standard of the water-body is determined to be whichever of the 2 elements is poorer/lesser.

For surface waters, the standards are dependant on the type of water-body. Artificial and heavily modified water-bodies must achieve ‘good potential’ and other, more natural water bodies must achieve ‘good status’ in comparison with set reference conditions. Studies are being undertaken in Europe to more tightly define what is meant by good status, good potential, ecological quality, reference conditions, etc.

In progressing its implementation, a competent authority is designated in each jurisdiction to take a lead role and to work alongside other relevant bodies. In NI, Environment and Heritage Service has been so designated.

The Directive requires an extensive amount of monitoring to be undertaken to establish baseline conditions for the water bodies and to assist in determining their classification.