Monthly hydrological indicators to assess impact of change on river ecosystems at the pan-European scale: preliminary results

The impact of change on river ecosystems at the pan-European scale under various climatological and development scenarios was assessed using a methodology based conceptually on the Range of Variability Approach (RVA) using Indicators of Hydrological Alteration (IHA), a desk-top technique for defining environmental flow requirements. The indicators are typically calculated from daily flows requiring extensive data storage and computing time when working at large spatial scales with multiple sites and scenarios. This paper presents an adaptation of the IHA approach using both daily and monthly flows. Modelled flows for nine scenarios (including baseline) and 664 sites from major rivers in contrasting European eco-regions were generated. IHA statistics based on daily and monthly data were calculated where appropriate (some daily IHA statistics cannot be calculated or are not meaningful at the monthly scale). Tailoring the RVA, acceptable baseline environmental flow ranges and and departures from these of the projected hydrological regimes were aggregated via a traffic-light colour-coding. The results show spatial patterns of potential river ecosystem impacts across Europe and demonstrate that using monthly flows is a reasonable trade-off for broad-scale studies.