When simulating movement of large area of fluid without much turbulence, we usually employ shallow water equations for better efficiency. However, when high details of large area of water surface are involved, how to show the detail of surface of fluid, and maintain high computation efficiency at the same time remains to be a challenging problem. In addition, if we want to simulate the interactions between water and complex terrain, the computation cost will be increased further. Enlightened by successful experiences of LOD techniques in modeling static terrain, we propose a novel method to simulate movement of large area of dynamic water on terrain.In the method, an adaptive technique based on the distance from view point to water surface and the difference of velocity gradient is proposed to determine the level of detail for rendering. With the method, the simulation efficiency is much improved.