Surface Water Quality Indicators

Abstract

Recent political pressures, often by environmental groups, have forced many of the Governments of the individual Member States to take a more positive approach to the management of the quality of surface waters within their country. This has increased markedly the need for monitoring the quality of surface water throughout the Community over the last few years. In addition the Community has introduced many water and environmental directives designed to protect the quality of the surface waters of the Community which will also lead to increased monitoring. Such monitoring programmes can be very complex and can generate so much data that presentation and interpretation becomes quite difficult. Accordingly, classification schemes, based on water quality indicators, have been devised by most Member States to convert the mass of data produced into water quality classes. These, in turn, can be used to demonstrate compliance with the requirements of EC Water Directives and to reveal temporal and spatial trends in surface water quality. Most schemes currently in use in the Member States for the monitoring and management of surface water quality are based on physico-chemical parameters, for example, suspended solids, biochemical oxygen demand, dissolved oxygen and ammoniacal nitrogen levels. It is most likely though that these will be complemented in the near future by biological/ecological techniques since these tend to provide a more overall assessment of the impact of water pollution and other environmental degradation. The paper examines the various approaches to the assessment of surface water quality and reviews a range of such schemes currently in use in the Community. Details of methods used to represent the data obtained from the use of these schemes on maps of water quality are also given. Finally recommendations are made for possible future surface water classification schemes.