Rivers vary in their ecological sensitivity to abstraction, and these differences are important when determining if additional water is available for abstraction, or if more stringent abstraction licenses need to be enforced. The current system of abstraction sensitivity bands is based on the best available scientific evidence, but direct empirical evidence to validate this approach is limited. As part of a broader review of its approach to licensing to ensure it has a robust and well-evidenced process to assess abstraction impacts, the Environment Agency commissioned WRc to compare the ability of alternative typology systems to represent the ecological sensitivity of rivers to abstraction. Using advanced statistical techniques to explore complex relationships between flow pressure metrics and macroinvertebrate community indices, the study provided evidence that both reduced and elevated flows have a detrimental impact on macroinvertebrates and that communities in modified channels are less resilient to reductions in low flows than those in morphologically natural channels. Further analysis evaluated a selection of alternative typology systems based on river size and degree of channel re-sectioning. The results fed into a broader review of flow standards by UKTAG and informed the Environment Agency’s future vision for local management of flows.
Report: Macroinvertebrate response to flow alteration