Authors: R Caroni W van de Bund R T Clarke R K Johnson
Publish Date: 2012/08/24
Volume: 704, Issue: 1, Pages: 437-451
Abstract
The Water Framework Directive WFD requires EU Member States to classify the ecological status of surface waters by using multiple biological quality elements BQEs According to the WFD Classification Guidance a ‘oneoutallout’ OOAO rule should be applied when integrating multiple BQEs into an overall biological status of a waterbody ie classification is determined by the lowest status BQE Using both simulated and monitoring datasets we analyzed the effects of different combination rules in classification outcome and classification reliability The OOAO represented the strictest combination rule in terms of increased probabilities of waterbodies being in moderate or worse status in comparison to other rules The OOAO approach gave acceptable results when different BQEs were complementary showing the effects of different pressures and when level of uncertainty in the metrics used in the assessment was not high Increasing the number of BQEs used in the assessment affected the classification outcome when using the OOAO approach this was especially problematic if all BQEs address the same pressure Our study showed that grouping of metrics and metrics uncertainty has a large influence on classification outcomes and that this should be carefully considered to ensure that final classification adequately reflects ecological statusThis paper is a result of the project WISER Water bodies in Europe Integrative Systems to assess Ecological status and Recovery funded by the European Union under the 7th Framework Programme Theme 6 Environment including Climate Change contract No 226273 wwwwisereu We wish to thank two anonymous reviewers for critical comments that greatly contributed to improve the paper
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