Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 12 3 2008 10.5194/hess-12-727-2008 http://www.hydrol-earth-syst-sci.net/12/727/2008/ http://www.hydrol-earth-syst-sci.net/12/727/2008/hess-12-727-2008.html http://www.hydrol-earth-syst-sci.net/12/727/2008/hess-12-727-2008.pdf 727 738 2008-05-14 On the measurement of solute concentrations in 2-D flow tank experiments M. Konz m.konz@gmx.de P. Ackerer E. Meier P. Huggenberger E. Zechner D. Gechter University of Basel, Departement Umweltwissenschaften, Switzerland Université Louis Pasteur, Institut de Mécanique des Fluides et des Solides, CNRS, UMR 7507,Strasbourg, France Edi Meier & Partner AG, Winterthur, Switzerland In this study we describe and compare photometric and resistivity measurement methodologies to determine solute concentrations in porous media flow tank experiments. The first method is the photometric method, which directly relates digitally measured intensities of a tracer dye to solute concentrations, without first converting the intensities to optical densities. This enables an effective processing of a large number of images in order to compute concentration time series at various points of the flow tank and concentration contour lines. This paper investigates perturbations of the measurements; it was found both lens flare effects and image resolution were a major source of error. Attaching a mask minimizes the lens flare. The second method for in situ measurement of salt concentrations in porous media experiments is the resistivity method. The resistivity measurement system uses two different input voltages at gilded electrode sticks to enable the measurement of salt concentrations from 0 to 300 g/l. The method is highly precise and the major perturbations are caused by temperature changes, which can be controlled in the laboratory. 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