New concepts in assessing lowland streams in Germany in accordance with the EU Water Framework Directive

摘要

Since ratification of the EU Water Framework Directive (EU-WFD), river assessment in Europe has taken a new turn, with biological quality indicators becoming the main focus and primary tool for describing ecological river quality. Implementing the EU-WFD requires new assessment and monitoring methods, which meet both legal demands and those of water management application. Within the project AQEM (The development and testing of an integrated assessment system for the ecological quality of streams and rivers throughout Europe using benthic macroinvertebrates) a method meeting these demands based on multi-habitat sampling and modular assessment was developed. It considers organic and structural degradation as the two main impact factors currently affecting stream biota. We describe the development of this system for lowland river types in northern Germany. The module for assessing the impact of morphological stream degradation on the aquatic biota is described in further detail based on data from about 100 samples. A multimetric index for evaluating ecological stream quality using macroinvertebrates is introduced. The main component is a "Faunaindex" based on indicator species. The suggested assessment method provides a tool for correlating macroinvertebrate biocoenoses with structural degradation and for discernment of five classes of structural quality, regardless of organic pollution. Possibilities and advantages of implementing the method in water management are discussed.