This note describes a procedure for evaluating the accuracy of numerical solute transport models in situations where exact closed-form solutions are difficult or even impossible to obtain. The procedure attempts to match a specified closed-form test solution by adding forcing terms to the original equation, which is solved numerically. The quality of the match provides valuable information about the performance of the numerical algorithm. We illustrate this prescribed forcing method with an example which simulates solute transport in a heterogeneous velocity field. The numerical solver considered in the example is based on the Eulerian-Lagrangian method with linear velocity and concentration interpolation. Two test solutions of different degrees of difficulty are considered. Differences between the exact and numerical test solutions for the example clearly reveal the influence of grid resolution on model accuracy. The example demonstrates that the prescribed forcing method can be used to assess numerical accuracy in practical situations where model inputs are highly variable and the true solution is unknown. ¿ 1999 American Geophysical Union