Résumé
Our study investigates the links between karst hydrogeology and surface hydrology. The aim is to assess to which extend karst can affect water balance, and which hydrological processes are affected. The used methodology is based on catchments water balance at their outlet, including precipitations P, evapotranspiration E, runoff Q, baseflow separation and intercatchment groundwater flows (IGF), combined to a geomorphological characterisation. Geomorphological parameters are drainage density, endorheism intensity and IDPR (Index of Development and Persistency of River networks, quantifying the terrains connectivity to hydrographic network). Annual components of the water balance are calculated from multi-annual time series at a daily time step for medium-sized catchments (from 50 to 500 km²). For each outlet, are differentiated global and intermediate catchments (defined as the draining area that feeds a river reach located between two gauging stations). The whole study site (25 000 km²) includes 3 karst zones of various geological settings in France (Cévennes Mountains, Jura Mountains, Normandy) equipped with 120 gauging stations. First, results show that many catchments are “non conservative” (i.e. Q > P or Qupstream > Qdownstream), and that this behaviour can be linked to supposed karstification associated to carbonate layers. Results also show that such karstification affects both quick and slow flow components, as well as the IGFs. In a second step, we find correlations between those hydrological characteristics and geomorphology, relatively strong depending on the study sites. Weakness in correlations for the karst Jura Mountains could be related to the importance of IGFs, as shown by local artificial tracing tests. Finally, our results highlight the control of catchment hydrology by karst and the specific role of groundwater flows in karst areas during floods. The high percentage of karst basins in the world gives interesting perspectives for hydrological flood indicators mapping linked to karstification.