Interactions between hydrology and habitat : Implications for river macroinvertebrates in England and Wales

While it is often considered axiomatic that both hydrological regime and channel morphology are key controls on ecological status in rivers, quantitative evidence of their combined influence is often lacking.
Here we describe the results of two studies from the UK which used Environment Agency monitoring data from England and Wales to describe common patterns in the response of one particular biotic index, LIFE (Lotic Invertebrate index for Flow Evaluation) to the combined effects of flow (discharge, measured in m³/s) changes and habitat modification. Across both the uplands and lowlands, there were relatively consistent patterns. LIFE responded to antecedent high and low flows. More modified sites not only had lower LIFE scores but also a steeper response of the LIFE score to antecedent low flows.
The results are consistent with the hypothesis that there is a greater variety of physical habitat niches in less modified channels, and that these habitats change less as flow changes. This is relatively unsurprising, however this is the first time this has been demonstrated using routine monitoring data. Further investigation has helped explain more detailed mechanisms behind these patterns.