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Tracer tomography: Conceptual design and field experiments using heat and uranine as tracers

Kennedy O. Doro1, Olaf A. Cirpka1, Carsten Leven1
1 Zentrum für Angewandte Geowissenschaften, Universität Tübingen

P 5.2 in Geophysikalische Methoden in der Hydrogeologie

 

The successful development of data inversion algorithms and experimental methods for hydraulic tomography has stimulated related research to include other type of data such as transport information derived from tracer testing. Tracer tomography involves by this means and in analogy to hydraulic tomography the sequential injection of a tracer at multiple points in an aquifer while measuring the corresponding spatial and temporal distribution of the tracer concentration at a large number of points. The resulting set of tracer breakthrough curves can subsequently be used in the inversion to further improve the recovery of the spatial structure of the hydraulic conductivity (K) distribution and to reduce the associated uncertainty. While reported studies on tracer tomography have so far focused on numerical or laboratory studies, we present field applications of tracer tomography using heat and uranine dye as tracers.

Our tracer tomographic experiments were conducted at the Lauswiesen test sites of the University of Tübingen. The aquifer at the site consists of a 6 m thick, heterogeneous alluvial sand and gravel deposit with an average K of 3 × 10-3 m/s. We used a forced gradient dipole injection-extraction system with a tracer injection in different levels in the injection well. Temperature sensors were installed at different levels in several observation wells to monitor the spreading of the heat tracer. For the monitoring of the uranine dye transport we used six fluorometer to record the tracer concentration at different depth levels in a multilevel well. A first analysis of the temporal and spatial distribution of temperature and uranine dye breakthrough curves shows aquifer connectivity and preferential flow paths that are in agreement with earlier work at the site. Subsequent inversion of the combined head data and concentration measurements will be presented revealing the spatial structure of the hydraulic conductivity distribution of the aquifer at the test site.

Letzte Änderung 01.11.2013