Ecological risk due to river flow alteration under climate and socioeconomic change scenarios

The river network was modelled as 33,668 cells (5° longitude; 5°latitude). For each cell, modelled monthly flows were generated for an ensemble of 10 scenarios for the 2050s and for the study baseline (naturalized flows for 1961-1990). These future scenarios consist of combinations of two climate scenarios and four socio-economic water-use scenarios (with a main driver of economy, policy, security or sustainability). Environmental flow implications are assessed using the new Ecological Risk due to Flow Alteration (ERFA) methodology, based on a set of monthly flow regime indicators (MFRIs). Differences in MFRIs between scenarios and baseline are calculated to derive ERFA classes (no, low, medium and high risk), which are based on the number of indicators significantly different from the baseline. ERFA classes are presented as colour-coded pan-European maps. Observed historical climate data for the reference period 1961-1990 were collated from the Climate Research Unit (University of East Anglia, UK). Projected future climate data for the period 2040-2069 (i.e. 2050s) were taken from two Global Circulation Models (GCMs): (i) IPSL-CM4, Institut Pierre Simon Laplace, France (IPCM4 thereafter); and (ii) MIROC3.2, Center for Climate System Research, University of Tokyo, Japan (MIMR thereafter). These two GCMs were chosen after comparing nine GCMs from the IPCC Fourth Assessment (IPCC, 2007); they were considered representative of the variability between GCMs (Bärlund, 2010). For both GCMs, the IPCC SRES A2 emission scenario (IPCC, 2007) was selected. In total, 11 sets of modelled monthly flow series were generated using different combinations of climate data inputs and socio-economic scenarios. Naturalized flows for 1961-1990 were generated by running WaterGAP with the hydrological component only (i.e. no water usage) and the historical climate data from CRU as input.