For biological quality, no absolute standards can be set across the community, so the
controls are specified to permit a small departure from the biological community expected in minimally anthropogenically impacted conditions, so-called reference conditions. These reference conditions are specified for each water body type and describe ecosystems representing relatively unmodified habitats with high values of the hydromorphological and physicochemical quality elements. The selection of those ecosystems allows for establishing type-specific biological reference conditions. Procedures for identifying ‘good ecological status’ for a given aquatic habitat, together with chemical or hydro-morphological standards needed to achieve this status, are provided. Good chemical status is defined with respect to compliance with all the quality standards established for chemical substances by the European Union.