Estimation of Solute Transport Parameters in Heterogen Groundwater System of a Karstic Aquifer Using Artificial Tracer Experiments

The artificial tracer experiments performed in the Lurbach karst system (north of Graz, Austria) were interpreted using different mathematical models that simulated mass transport between injection and detection sites. The first model assumes that the system consists of several parallel subsystems characterised by different flow rates, water volumes and dispersivities. The second model assumes that the tracer flows through a double-porosity system consisting of several parallel channels in the microporous matrix, and containing both mobile and quazi stagnant (immobile) water. The channels have the same apertures, volumetric flow rates and dispersivities and are equally distributed in the matrix. The tracer diffuses between mobile and immobile phase. Both models calibrate the experimental data to a high degree of accuracy. Additionally, the measured tracer concentration curves were interpreted by applying the method of moments, a commonly used practice. It is shown herein that the parameters obtained in this way could not calibrate the experimental data.