Utilisation des indices diatomiques pour la mesure de la qualité des eaux du bassin Artois-Picardie: Bilan et perspectives

Abstract

Because of the special nature of the streams in its basin, the Water Agency of Artois-Picardie adopted in 1988 the diatoms and diatom indices for the assessment of water quality. Six indices have been tested. The results show that the IPS or Specific Polluosensitivity Index (Coste in CEMAGREF 1982) is the only on provide a realistic assessment of water quality. This index integrates three variables: organic pollution expressed as DBO5, DCO or ammonium, salinity expressed as conductivity and chlorides, and eutrophication which, when actual, is expressed as chlorophyll levels and, when potential, is expressed as phosphate levels. These three variables are the principal factors responsible for variations in water quality within the basin. In addition, the physicochemical conditions were markedly stable throughout the year and therefore the diatom indices calculated in September are representative of summer water quality. Different simulations have been made, using the program OMNIDIA, in order to determine a practical index that can be used routinely. The results show that the best approach is to work at the generic level with occasional determinations to species. © Gauthier-Villars, 1993.