COMPARISON OF SURFACE-WATER GROUNDWATER INTERFACE ZONES IN FLUVIAL AND KARSTIC SYSTEMS

Abiotic (solutes) and biotic (organic matter and living organisms) int eractions between groundwaters and surface waters were analyzed by def ining differences and exchanges between the 2 compartments of fluvial and karstic springs. Most of the physico-chemical variables showed som e homogeneity between the 2 compartments whatever the spring considere d. However they exhibited temporal variations throughout the study per iod The particulate organic matter accumulated differently in the surf ace stream and in the aquifer of both springs and showed variations wi th hydrological periods. Biotic interactions estimated from the compos ition and organization of the invertebrate communities made it possibl e to describe an ecotone between surface water and groundwater in the 2 springs (fluvial and karstic), characterized by mixed communities (e pigean and hypogean). These ecotones were mainly located in the ground water compartment whatever the spring considered but their limits show ed marked spatial fluctuations linked to hydrology, thus resulting in elasticity. Although the great difference in physical permeability, th e functionings of the 2 springs appeared relatively similar.