ANALYSIS OF THE SPATIAL AND TEMPORAL VARIATIONS IN THE WATER-QUALITY OF A KARSTIC AQUIFER USING UV SPECTROPHOTOMETRY

This article presents a simple method based on the examination of ultr aviolet multiwavelength absorptiometry of groundwater samples collecte d from a karstic aquifer, for direct and fast quality evaluation. The method provides information about the flow conditions of a karstic sys tem, it helps with the monitoring of groundwater sampling during the p umping procedure and, finally, it gives an insight into the complexity of the spatial and temporal evolutions of the system. Application of this method to the study of a karstic experimental field situated in t he south of France is subsequently presented. UV spectrophotometry use d during investigations shows the hydraulic relation between two piezo meters, and also between a piezometer and a surface watercourse. It st resses the influence of surface hydrology on water quality of this kar stic aquifer. During periods of high now, the water quality is the sam e in all the piezometers and is linked to the leaching of nitrates pre sent in the upper surrounds of the aquifer; during mean or low flow, e ach piezometer presents a particular water quality depending on its lo cal transmissivity.