Abstract: By probing into the evolvement of distributed hydrological model and considering real conditions of the arid or semi arid regions in China, this paper advances Distributed Time Variant Gain Model (DTVGM) by coupling the mechanism of water cycle with system theory. The distinguish feature of TVGM is that runoff generation contribution can be analyzed by a set of time variant gain parameters (g1, g2, etc.). The rainfall runoff relationship characterized by TVGM is just a typical nonlinear behavior. DTVGM is developed based on TVGM. It picks up such information as the gradient of the slope, the direction of the slope, the water current path, as well as the boundaries of the river network and the watershed of the land surface units with DEM by establishing itself on the basis of GIS/DEM. It simulates the movement of the water in the soil vegetation atmosphere (SVAT) system, describes the relation between the cellular grids in the horizontal direction, and performs mathematical calculations of the surface water and the groundwater on the watershed cellular grids divided by DEM. DTVGM includes two components: one is runoff generation process on grid elements; the other is flow routing process based on ranked grids. At present, the runoff generation process is divided into two layers in the vertical direction: the upper layer is the surface flow; the lower layer is the subsurface flow. On the other hand, the kinematic wave models are applied to simulate the flow routing process. At the end of the paper, the distributed hydrological model of Chaohe River Basin is established by applying DTVGM. The research results indicate that the application of DTVGM is successful, which can satisfy the requirement of water resources management.

Key words: Chaohe River Basin, Distributed Hydrological Model, System Theory