Physico-chemical supporting elements in inland waters under the water framework directive : a review of national standards to support good ecological status

The task group on supporting physico-chemical elements have reviewed information reported by Member States to WISE (Water Information System for Europe) on the standards for general physico‐chemical quality elements including nutrients used under the European Water Framework Directive (WFD). A wide range of supporting physico-chemical elements are used by Member States. This report focusses on those that are ecologically most relevant for inland waters and which are used by enough Member States to make realistic comparisons. These are: Rivers: BOD (Biochemical Oxygen Demand), dissolved oxygen, pH, total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), nitrate-N, ammonium-N and salinity (conductivity and chloride); Lakes: Transparency (Secchi depth), dissolved oxygen, pH, TP, TN. A separate report will document the situation for transitional and coastal waters. Systematic variation between both types and countries is apparent for several of these, although comparisons are complicated by differences in the ways that data have been reported. Some of the standards appear unlikely to support good status for sensitive biological quality elements, based on type-specific comparisons with biological data in the EEA database (https://www.eea.europa.eu/data-and-maps/data/waterbase-biology). Further considerations and dialogue are needed with the countries using those standards.