Abstract
Artificial tracer tests are widely used by consulting engineers for demonstrating water circulation, proving the existence of leakage, or estimating groundwater velocity. However, the interpretation of such tests is often very basic, with the result that decision makers and professionals commonly face unreliable results through hasty and empirical interpretation. There is thus an increasing need for a reliable interpretation tool, compatible with the latest operating systems and available in several languages. BRGM, the French Geological Survey, has developed a project together with hydrogeologists from various other organizations to build software assembling several analytical solutions in order to comply with various field contexts. This computer program, called TRAC, is very light and simple, allowing the user to add his own analytical solution if the formula is not yet included. It aims at collaborative improvement by sharing the tool and the solutions. TRAC can be used for interpreting data recovered from a tracer test as well as for simulating the transport of a tracer in the saturated zone (for the time being). Calibration of a site operation is based on considering the hydrodynamic and hydrodispersive features of groundwater flow as well as the amount, nature and injection mode of the artificial tracer. The software is available in French, English and Spanish, and the latest version can be downloaded from the web site http://trac.brgm.fr.
Highlights
Contaminant migration in aquifers threatens groundwater quality and the exploitability of water-supply wells
BRGM, the French Geological Survey, has developed a project together with hydrogeologists from various other organizations to build software assembling several analytical solutions in order to comply with various field contexts
In France, tracer tests are widely used for defining protection zones around water-supply wells; their interpretation generally relies on abacus [1, 2], or uses the simple CATTI [3] program running under MS-DOS
Summary
Contaminant migration in aquifers threatens groundwater quality and the exploitability of water-supply wells. - From an initial asumption of flow and transport parameters, the computation of a theoretical breakthrough curve aims at getting a good fit with the observed one. The computation codes for interpreting a breakthrough curve discussed here use an analytical solution derived from the general convection-dispersion equation to evaluate solute transport in porous media This equation can be written as follows: considering C(x, t) as the volumetric mass concentration of the contaminant and qw the flux velocity vector, if no adsorption reactions occur between the contaminant and the surrounding porous medium, the transport is determined by convection and diffusion.
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