A reappraisal of saprobic values and indicator weights based on Slovenian river quality data.

The saprobic values and indicator weights used in the Slovenian saprobic system are reappraised using data from the 1990 to 95 river quality surveys of Slovenia. The conceptual basis of the reappraisal is described and then formulated mathematically. The analysis is based on 1,106 biological samples and covers 300 taxa. The results are expressed in terms of revised saprobic values and indicator weights that mirror the ones previously assigned by ecological experts. The most significant differences between original and revised values are highlighted and discussed. It is concluded that: (a) the revised values and weights are more representative of their 'true' values than are the original values and weights, but that it would be premature to consider them definitive; (b) the analytical method provides a sound data-based approach to the revision of saprobic values and indicator weights; and (c) the method could help to improve and harmonise the various saprobic systems currently in use across Europe.

River Pollution Diagnostic System (RPDS)--computer-based analysis and visualisation for bio-monitoring data.

The importance of biological monitoring for the assessment of river quality is well established. Bio-monitoring programmes, in particular the recording of benthic macroinvertebrate assemblages, produce an abundance of data to support the process of river quality assessment. However, current data analysis techniques are largely based on subjective score systems that do not fully realise the potential information value of such complex multivariate data sets. More advanced techniques of data analysis and visualisation can help to maximise the value of biological data, and hence to more efficiently and effectively direct resources, funding and research. A River Pollution Diagnostic System (RPDS) is described. RPDS was recently developed by the authors for the Environment Agency in England and Wales; it aims to maximise information retrieval from biological and environmental data.