Abstract
In karstic systems, the heterogeneity of the transfer processes within the different compartments of thecritical zone (soil, epikarst, and saturated zones) controls the recharge -discharge relationship. TheMEDYCYSS observatory (Multi scalE observatory of flooD dYnamiCs and hYdrodynamicS in karSt,belonging to OSU OREME and SNO Karst network) has been set up to better understand thesetransfers under a Mediterranean climatic context. On the Lez karst catchment (South of France), beingpart of MEDYCYSS, a 333 m deep borehole has been equipped with the PMPS Multi-level monitoringsystem (SolExperts) in the framework of the CRITEX project. The borehole is located 100 m from anintermittent river and 500 m from the main outlet (Lez Spring) of the aquifer where an intense pumpingis performed. Continuous pressure and temperature monitoring is realized at 5 depth levels, isolatedby packers, where discrete water sampling are also regularly achieved. The main objective of thismonitoring is to assess the different mechanisms of the recharge process at various time scales. Thecollected data implement the existing spatio-temporal monitoring of the hydrodynamic andgeochemical variations followed in bore-holes, karst features (caves and sink-holes), perennial andtemporal springs of the karstic aquifer. In this study, we aim at specifying the contribution of thedifferent karst compartments, from the recharge zone towards the main outlets. The results obtainedduring a one year monitoring show a contrasted hydrodynamic response and underline a pressuretransfer between compartments, surface water and karst flow. Assessed by temperature monitoring,the hydrochemistry shows a stable water composition for each compartment of the bore-hole, incontrast with the high variability and water mixing identified at the Lez spring. These new data areessential to better assess the recharge processes and specify the role of the vadose zone in the floworganization at short and long timescale.