An indicator system for surface water quality in river basins

Public utilities, agricultural and industrial economical sectors and ecosystems depend on the water supplied by the natura environment. These water needs, the European Water Framework Directive requirements and the key surface water pollution problems identified at a River Basin scale, lead to the development of a water quality indicator system for surface waters. This is an environmental tool, which allows the assessment of the pressure-stateimpact of human activities on surface water quality. This paper presents a methodology based on the conceptual model Pressure State Response, and on an environmental description of the Portuguese Ave River Basin, based on chemical and hydro-morphological water quality elements, due to the lack of information regarding biological elements. 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, contamination by bacterias, presence of organic mater, oxidation state and organic metals emission