Stream Hydrochemical Response to Flood Events in a Multi-Lithological Karstic Catchment from the Pyrenees Mountains (SW France)

Hydrological variations hold a significant influence over the water chemistry in karstic critical zone. In this context, Baget Catchment (BC) has been monitored at high resolution two years outlet order to set up typology of flood events. The objective was assess multiple streamwater physico-chemical patterns response hydrological variations, streamflow component (quick-response, subsurface, and baseflow) lithological contributions, biogeochemical processes. catchment exhibited an impulsive events relation typical structural morphological characteristics karst. addition, constrained by magnitude rainfall preceding hydroclimatic conditions. variability dissolved load closely associated with weathered rocks conditions throughout year. Two simple indicators allow characterize concentration–discharge relationships different hysteresis on floods various intensities shapes hydrograph under before flood. Almost all elements either clockwise loops or more complex behaviors, suggesting higher overall concentration when major contribution comes from quick-response flow (karst surface runoff fraction). Besides, epikarst flushing dry led counterclockwise for calcium (Ca2+) bicarbonate (HCO3−) which revealed chemostatic behavior as result carbonate dissolution On contrary, sulfate (SO42−) widest relative variation during flooding showed sensitivity dilution process increasing discharge. For medium episodes (Qmax < 4.4 m3·s−1), increase could be observed rising limb hydrograph. opposite, extreme > 8.3 m3·s−1) occurring after several rain events, pattern noted originating rock weathering. Finally, high-frequency sampling storm improved understanding factors controlling hydrochemical dynamic catchments.