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This report describes an enhanced version of the U.S. Geological Survey modular ground-water model, called MODFLOW-2000, for which the structure has been expanded to facilitate the solution of multiple related equations. The performance of the program has been tested in a variety of applications. Future applications, however, might reveal errors that were not detected in the test simulations. Users are requested to notify the U.S.
Harbaugh et al. (Sat,) studied this question.