The work presented in this paper is part of a study to simulate the degeneration of internal waves, from an initial basin-scale seiche to high-frequency nonlinear internal waves (NLIWs), in a medium-sized lake. To fulfill this objective, a parallel three-dimensional (3D) code with non-hydrostatic capability, the MITgcm (Marshall et al. 1997a) is used. This model has been