Abstract: With the view of energy variation, the machanism of evolution of barotropic disturbances is studied in this paper. It is found that the topography can affect only the variation of enstrophy but not the kinetic energy of baratropic disturbances. This is quite different with the effects of shearing of basic flow which do affect both the variation of kinetic energy and enstrophy. If the basic flow is uniform in space and the effect of topography is negligible, the mean kinetic energy and enstrophy averaged in the whole region are bounded. But if the basic flow is non-uniform and is wave-like, the development of disturbances is closely related to the structure of the disturbance. Generally, the kinetic energy and enstrophy are not conservative. The effects of topography with simple profile are also discussed in this paper.