Defining Good Ecological Status of Water, as Required by the European Water Framework Directive

Keywords: Water Framework Directive, WFD, biological classification, eutrophication.

The EU Water Framework Directive (WFD) is an important new approach to managing water. It provides a clear approach to managing the water environment in a way that will achieve a long term sustainable use. Unlike previous European legislation it does not focus on specific pollutants or sources of pollution, but has at its centre the concept of ecological quality. The assessment of ecological quality is achieved using specific metrics that assess the status of the biological community of rivers, lakes, estuaries and coastal waters, together with the chemical and hydromorphological metrics that support the biology. The primary objective of the WFD is to prevent deterioration and subject to specific exceptions to achieve Good ecological status by 2015. The assessment of ecological status for the WFD has been a significant challenge to many countries as new biological assessment techniques have had to be produced. This has led to the development of common guidance concerning the development of boundaries for ecological status and the comparison of national methods and boundaries through a process of intercalibration.

One of the most widespread pressures on the water environment in Europe is nutrient enrichment leading to eutrophication. Several new methods have been developed to assess this pressure, but common approaches have been used and all express status as an Ecological Quality Ratio (EQR) which represents the degree of change of a biological community from what would have been expected. The precise nature of these metrics is a matter for each European country, but all respond to increases in plant nutrients. The boundaries for status are based on definitions provided in the WFD. A key principal underpinning boundary setting in the context of eutrophication is the increasing likelihood of undesirable disturbances to the aquatic community. Undesirable disturbances are not defined by the Directive, but examples are given in guidance documents and a common strategy has evolved within Europe for the establishment of boundaries for this particular pressure. The basic premise is that plants (algae and higher plants) will respond to increased nutrients and these changes can cause changes to other groups of organisms as a result of secondary effects. Where these changes are significant then this will represent an undesirable disturbance. The Directive recognises that few if any water bodies in Europe will be in a true pristine state; it accepts that at High status there will be minor but insignificant change. At Good status change will be greater, but the biology will demonstrate that there is a negligible chance of undesirable disturbances and by the time a water body reaches Poor status these effects will be very common.

The assessment of status also requires an assessment of uncertainty. This is a relatively new consideration for many Member States and is an aspect that will require further work. In the UK uncertainty has always been a key consideration and all new biological methods developed for the WFD quantify this uncertainty. Classifications are reported at their face value class, but where there is significant uncertainty the priority for action is to understand the reasons for this to ensure that measures are appropriately targeted. The WFD is a challenging Directive, but through its reliance on ecological status it requires us to understand how activities in a catchment can influence the sustainability of our freshwater environment and thus focuses our management where risks are high.

Geoff Phillips, Environment Agency, Kings Meadow House, Kings Meadow Road, Reading, Berkshire RG1 8DQ, UK.

19 pages, 1 figure, 41 references.