Tracer tests in karst hydrogeology and speleology

Abstract

This article presents an introduction to the fundamentals of tracing techniques and their application in cave and karst environments, illusrated by case studies from the Mammoth Cave, USA, and a small experimental site in Switzerland. The properties and limitations of the most important artificial tracers are discussed, and the available methods of tracer injection, sampling, online monitoring and laboratory analysis are presented. Fully quantitative tracer experiments result in continuous ordiscrete concentration-time data series, i.e. breakthrough curves, and concomitant discharge data, which make it possible to obtain detailed informaton about groundwaterflow and contaminant transport. Within the frame of speleological investigations, tracertests can help to resolve the active and often inaccessible part of cave and conduit networks and to obtain indications about the geometry and volume of the conduits. For hydrogeological studies, caves can in turn be used as natural experimental and monitoring sites inside the unsaturated or saturated zone of karst aquifer systems.