VARIATIONS IN STABLE OXYGEN ISOTOPE AND SOLUTE CONCENTRATIONS IN SMALL SUBMEDITERRANEAN MONTANE STREAMS

Stable oxygen isotope concentrations in rainwater and streamwater were determined, combined with routine hydrochemical monitoring of three granitic catchments in the South of France. deltaO-18 in streamwater showed much less variation than in rainwater. A seasonal pattern in baseflow conditions (higher deltaO-18 in summer) suggests that the groundwater store is small and subject to evaporation. Variations in high flow conditions show that pre-event water can contribute significantly to streamflow, especially in non-forested areas. Alkalinity and silica concentration are the only other parameters that show consistent behaviour during storm events. The latter could be used as an alternative to deltaO-18 for hydrograph separation.