Multi-traçage de la Fontaine de Nîmes

Abstract

Multi-tracing of Fontaine de Nîmes. The main outlet of the Nimes karst system is the Fontaine de Nimes spring. In the past, several tracing experiments have identified relationships between points supposed to be part of the recharge area of the system and the Fontaine de Nimes spring. Nevertheless, these tracing experiments suffered from a lack of breakthrough curves. In this paper, the results of a multi-tracing test realized in March 2006 from four injection points are described. The monitoring network of this experiment has been designed in order to characterize the respective roles of the three karst conduits (west karst conduit, north karst conduit and Galerie des Poteries) leading to the main spring. The major results are following : (i) all the dye tracers have been identified at the Fontaine de Nimes spring (ii) the west karst conduit plays a major role in the drainage of the recharge area of the karst system (iii) no dye tracer has been identified on the north karst conduit (iv) the discharge rate into the Galerie des Poteries, measured by dilution of salt upstream injected, is less than 50 l/min, the recharge area of this conduit is geographically very limited. We can notice that well-structured breakthrough curves have been obtained for three of the four tracers.