THE EFFECTS OF WATER ABSTRACTIONS ON INVERTEBRATE COMMUNITIES IN UK STREAMS

There are increasing concerns about the ecological effects of water ab straction and in the UK, these concerns have been hightened by the 197 6, 1984 and 1988-92 droughts. This paper assesses macroinvertebrate an d environmental changes induced by surface and groundwater abstraction s on 22 streams throughout the UK. The approach involved comparative r esearch to assess differences between reference and impacted sites. Us ing a database comprising 204 sets of biological and environmental dat a (89 taxa and 16 environmental variables) a preliminary ordination us ing principle components analysis clearly differentiated three types o f sites: upland, lowland and an intermediate type. At this scale, any effects of abstractions on invertebrate communities are shown to be in significant relative to regional controls. A simultaneous ordination o f the environmental and faunal differences between pairs of sites was undertaken separately for each of the three regional groups. Differenc es are considered as vectors having both direction and amplitude and t he analysis elucidates common patterns in the faunal and environmental data. Important changes were observed in two situations: upland strea ms affected by major diversions as part of hydro-power schemes in Scot land and lowland rivers impacted by groundwater abstractions. No stron g patterns of change (either in amplitude or orientation) were demonst rated within any of the taxonomic groups. However, within the upland t ype some rheophilous taxa were shown typically to be reduced in abunda nce at impacted sites. Within the lowland type, a consistent pattern i n the dataset is demonstrated by a group of taxa that are reduced in a bundance at the impacted sites.