Origin and development of the biological monitoring working party score system

A history of biological monitoring of river water quality in Britain by individual biologists in different regions is briefly traced. The first official use of biological methods was in the 1970 National River Pollution Survey by the Department of the Environment. Following criticism regarding the adequacy of the method used, the Department set up the Biological Monitoring Working Party (BMWP) to recommend a system for use in national river pollution surveys. This paper reviews the proceedings of the working group, which led to the recommendation of a "score" system based on benthic macro-invertebrates. The outcome of the working groupʹs deliberations regarding levels of identification, abundance, zonation and method of sampling are recorded. The principles by which the scores were allocated to the different families and the reason for having different scores for eroding and depositing substrata samples are explained. The hitherto unpublished explanation is provided for the significant differences between the score system used in the 1980 and subsequent River Pollution Surveys and that recommended in the Final Report of BMWP.