Report on future projections of flow intermittence for the 6 European focal DRN

Künne, Annika; Mimeau, Louise; Devers, Alexandre; Kralisch, Sven; Branger, Flora; Lauvernet, Claire; Vidal, Jean-Philippe; Datry, T.; Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany]; RiverLy - Fonctionnement des hydrosystèmes  ; Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement; Friedrich Schiller Universität; European Project: 869226,DRYvER

Report on future projections of flow intermittence for the 6 European focal DRN

2023

Intermittent rivers and ephemeral streams (IRES) account for more than half of the world's rivers.However, few studies have investigated the evolution of IRES under climate change. To overcome thisproblem, DRYvER proposed to provide daily hydrological projections, daily flow conditions and flowintermittence indicators in 6 European Drying River Networks (DRNs).The current work aims to provide reach-scale daily flow conditions and flow intermittence indicatorsfor the period 1985-2100 for each DRN. To this end, daily reach-scale hydrological projections - drivenby several global climate models and Shared Socio-economic Pathways (SSP) - are used as input to arandom forest algorithm trained in the historical period with actual observations of daily flowconditions. Once the flow conditions have been generated, a set of flow intermittence indicators iscalculated to study the evolution of intermittence through the 21st century.Results highlight the coherence of the intermittence projections and intermittence reconstruction overthe period 1985-2014. The inter-annual number of dry days of each reach of the DRNs from theprojections are quite close to those from the reconstruction. Furthermore, the seasonality is wellcaptured on all 6 DRNs, providing a reasonable confidence for future intermittence projections. Theperiod 1985-2100 globally highlights a steady increase of the intermittence on all DRNs, with anintensity linked to the SSPs considered – i.e. higher increase with higher emissions - and the periodconsidered. The study also suggests the transition of some reaches from perennial to intermittent,depending on the catchments, the SSP and the period considered.

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