Combination of BQEs into a complete water body assessment (workpackage 6.2)
This workpackage addresses the problem of combining information from different BQEs into a complete water body assessment, taking into account the pressures, the response signatures of the indicators, redundancy, and uncertainty. The underlying hypothesis is that response signatures as well as the uncertainties associated with the classification are different between indicators, both within a BQE and between BQEs, and that these differences have major consequences for the classification outcome when combining results for different BQEs. The main objectives of workpackage 6.2 are to: demonstrate the practical implications of the 'one-out all-out' approach and alternative approaches for assessment of water bodies and make practical recommendations for end users on the combination of metrics and BQEs.
The combination of BQEs into a complete water body assessment is primarily based on existing monitoring datasets containing pressure information and biological classification data from several BQEs for coastal waters, lakes, and rivers. Pressure gradients are identified and related to biological metrics for all BQEs. An analysis on the redundancy of metrics will facilitate identify the best suited combination of metrics and BQEs for a given water body category and stressor. Therefore, different combination rules were identified in a review and will be applied, and the consequences for the classification outcome will be demonstrated. The data from the WISER field campaign (lakes and transitional/coastal waters) are used to carry out a similar analysis as described above, and allow of taking into account a more complete coverage of pressures and BQEs.
A review has been made on how different BQEs are being combined in WFD monitoring and assessment programmes in different Member States (Deliverable D6.2-1). A further intention of the work is the identification and the description of overall national classification systems adopted in Member States for assessing ecological status of water bodies. A questionnaire has been elaborated to explore the combination rules being implemented by each Member State at different levels such as the biological status through the integration of different biological quality elements (BQEs) results and the final ecological status through the integration of biological, physico-chemical and hydromorphological results.
Relevance for end users
Guidance on the selection and combination of BQEs and metrics will help water managers select the most suited combinations for a given stressor. Hence, redundant metrics and BQEs can be identified, which will help optimise monitoring and reduce the costs. The implications of the application of the one-out-all-out principle will help identify the strengths and weaknesses of this approach.