An indicator system for surface water quality in river basins

Public utilities, agricultural and industrial economic sectors, and ecosystems depend on the water supplied by the natural environment. The European Water Framework Directive requirements, water demands and key surface water pollution problems identified in a river basin, lead to the need to develop a surface water quality indicator system. This tool allows the assessment of the pressure-state-impact of human activities on natural waters. This paper presents a methodology used for the development and application of an indicator system in the Portuguese River Ave basin, based on the conceptual Pressure-State-Response model, and on chemical and hydromorphological water quality parameters. It is shown that the most relevant questions'for the implementation of an indicator system for the surface waters of this river basin are: eutrophication, bacterial contamination, presence of organic mater, oxidation state and organic metals coming from industrial wastewater discharges.