Response of river invertebrate indices to hydrological drought indicator

Relationship between a drought-oriented streamflow index and a series of riverine biological indicators have been investigated at c. 80 sites in England and Wales in order to assess: (i) the impact of drought conditions on river ecosystems; (ii) whether the streamflow index could be used successfully as an early-warning indicator of drought impact on river ecosystems. Results show some significant albeit limited response to drought conditions as well as antecedent conditions (eg flow indicator 6 months before, 12 months before). Overall, when flow conditions are drier, biological indicators decrease. Decrease magnitude varies greatly and at some sites, the actual ecological impact is limited. There is some significant but limited patterns of the biological indicator response slope to flow in terms of catchment characteristics.