The Qtracer2 Program for Tracer-Breakthrough Curve Analysis for Tracer Tests in Karstic Aquifers and Other Hydrologic Systems

Tracer testing is generally regarded as the most reliable and efficient method of gathering surface and subsurface hydraulic information. This is especially true for karstic and fractured-rock aquifers. Qualitative tracing tests have been conventionally employed in most karst sites in the United States. Quantitative tracing tests are employed sparingly at karstic sites in the United States, although it is widely recognized that they provide a wealth of hydraulic and geometric data and are commonly employed in nonkarstic hydrological systems. Quantitative tracer tests are regarded as more difficult and time-consuming than qualitative tracing tests, which is a fallacy that needs to be overcome. The benefits of quantitative tracing far outweigh any additional expenses incurred for all hydrologic systems.

An efficient, reliable, and easy-to-use computer program, QTRACER2, designed to run on PCs running any version of Microsoft Windows, has been developed to facilitate tracer-breakthrough curve (BTC) analysis. It solves the necessary equations from user-generated data input files using robust integration routines and relies on established hydraulic models. Additional features include dynamic memory allocation, the ability to extrapolate late-time data using any one of three different methods, two separate methods for handling oversized time-concentration data files, and a powerful interactive graphics routine.

Four other programs are included to facilitate the use of QTRACER2. The first, NDATA, allows users to interpolate either their time-concentration or time-discharge data files to fill in data gaps. The second program, AUTOTIME, allows users to convert time-concentration data files recorded using military time (a 24-hour clock) into sequential decimal time as required by QTRACER2. Files created by these two programs may be combined and appended to the bottom of a sampling station data file that can then be read by QTRACER2.

The easiest method for creating a new data-input file for use in QTRACER2 is to modify an existing data-input file using a standard text editor (e.g., Notepad) and save the revised file with a new name. However, if desired the user may access the third additional program, DATFILE, to create or modify a data-input file by answering a series of querries posed by the program.

Lastly, the fourth program was designed to address the problem of non-matching time-concentration and time-discharge data. The program, COMBINE, combines two disparate time-data sets into one time-concentration-discharge data set for use by Qtracer2.


U.S. EPA. The Qtracer2 Program for Tracer-Breakthrough Curve Analysis for Tracer Tests in Karstic Aquifers and Other Hydrologic Systems. U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Washington Office, Washington, DC, EPA/600/R-02/001, 2002.