Séminaire animé par Julien Némery
Coupled hydrological-hydrogeological models, emphasizing the importance of the stream–aquifer interface, are more and more used in hydrological sciences for pluridisciplinary studies aiming at investigating environmental issues. They are of peculiar interest for biogeochemists who try to assess the elimination of biogenic compounds in such interfaces. If ecohydrologists do consider biogeochemical processes in sediments, it remains a challenge to quantify the functioning of the hyporheic buffer which controls the fate of biogenic compounds. In this presentation, I first illustrate the importance of the sediment compartment for the in-river carbon fate in the Seine River downstream Paris urban area using the hydro-ecological model ProSe. Far from being negligible as usually expected for large rivers, the sediments contribute for 30% to the total respiration of the system (Vilmin et al. 2016). Those estimates rely on a well calibrated model, and especially sediment fluxes along the 220 km simulated river stretch (Vilmin et al. 2015). The hyporheic zone also plays a significant role in river metabolism and greenhouse gas emission. In a collaborative work, we also recently estimated that the production and emission towards the river of end products such as CO2 are driven and controlled by the connection status (gaining or loosing) and the frequency of flow reversal due to hydrological events (Newcomer et al. 2018). It is therefore crucial to develop tools and methodologies to assess water fluxes between surface and subsurface (Flipo et al. 2014).