River flow indexing using british benthic macroinvertebrates : A framework for setting hydroecological objectives

A method linking qualitative and semi-quantitative change in riverine benthic macroinvertebrate communities to prevailing flow regimes is proposed. The Lotic-invertebrate Index for Flow Evaluation (LIFE) technique is based on data derived from established survey methods, that incorporate sampling strategies considered highly appropriate for assessing the impact of variable flows on benthic populations. Hydroecological links have been investigated in a number of English rivers, after correlating LIFE scores obtained over a number of years with several hundred different flow variables. This process identifies the most significant relationships between flow and LIFE which, in turn, enables those features of flow that are of critical importance in influencing community structure in different rivers to be defined. Summer flow variables are thus highlighted as being most influential in predicting community structure in most chalk and limestone streams, whereas invertebrate communities colonizing rivers draining impermeable catchments are much more influenced by short-term hydrological events. Biota present in rivers with regulated or augmented flows tend to be most strongly affected by non-seasonal, interannual flow variation. These responses provide opportunities for analysing and elucidating hydroecological relationships in some detail, and it should ultimately be possible to use these data to set highly relevant, cost-effective hydroecological objectives. An example is presented to show how this might be accomplished. Key areas of further work include the need to provide robust procedures for setting hydroecological objectives, investigation of habitat quality and LIFE score relationships in natural and degraded river reaches and evaluation of potential links with other biological modelling methods such as RIVPACS. Copyright © 1999 John Wiley & Sons, Ltd.