The comments by Groenendijk et al. (2006) nicely illustrate the usefulness of analytical benchmarks for code developers to test and improve numerical models. These benchmarks may also be useful for model users to validate whether the numerical settings (e.g., space and time discretiztion, convergence and iteration parameters, discretiztion and/or linearization of the hydraulic functions) that they use guarantee sufficient accuracy of the numerical solution. The problem addressed by Groenendijk et al. (2006) actually points to the importance of these settings to obtain an accurate solution. As a consequence, some model developers tend to fix these settings in the model code,...

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