Assessing Flow Regime Alterations by Reservoirs in France Through Hydrological Signatures

Código

XXVI-SBRH0345

Autores

Julia dos Santos da Silva, Bruno Lemaire, Francesca Pianosi, Fanny Sarrazin

Tema

B - Usos múltiplos da Água e Reuso

Resumo

Reservoirs significantly alterer the natural flow of rivers, with varying impacts depending on how they are used and managed. In France, the increasing demand for irrigation reservoirs highlights the need to better understand these impacts. Here we present the first national-scale assessment of reservoir impacts on hydrological regime in France, using a large set of 1107 catchments. We distinguished 190 regulated and 917 potentially unregulated catchments, based on the presence of reservoirs above 1hm3 or with a cumulated storage capacity equivalent to more than 10mm of rain over the catchment area. A set of hydrological signatures was applied to detect changes in flow regime, and in drought and flood characteristics between regulated and unregulated catchments. Overall, reservoirs change flow seasonality, reduce intensity and duration of floods and droughts, reduce flood frequency, while increasing drought frequency and inter-annual sensitivity to rain. When separating the catchments according to their reservoirs purposes, we observe varying impacts. Specifically, irrigation reservoirs reduce low-flow variability, increase inter-annual sensitivity to rain and drought frequency, and shorten their duration. Hydroelectricity reduces runoff inter-annual sensitivity to rain, alters runoff seasonality and flood duration, reduces flood and droughtintensity and decreases drought duration. Multiple-use reservoirs have similar effects as on the national scale. Ultimately, the study allows us to better understand how reservoirs can affect regulated rivers, which is relevant for collective reservoir management in the frame of the ecological transition.