Hydrological Object‐Based Flow Direction Model for Constructing a Lake‐Stream Topological System

The topological system of lakes and streams is the basis for deriving a multitude of patterns and processes in hydrology, geomorphology and ecology. Flow direction is key to constructing a lake‐stream topological system. However, lakes and streams are important hydrological objects that should be considered since they are linked during the process of material and energy transportation. Therefore, a flow direction algorithm that can clearly express the topological relationship of lakes and streams, was proposed here. Lakes and streams were taken as the hydrological objects in stream networks and coupled into a flow direction algorithm. A topological system was established based on the proposed algorithms. Six areas on the Tibetan Plateau were chosen as sample areas with the MERIT digital elevation model (DEM) as the DEM data source. Streams derived from flow direction data in the HydroSHEDS data set (HYDROSTREAMS) and MERIT hydro data set (MERITSTREAMS), as well as streams derived from flow direction results of the D‐infinity algorithm and priority‐flood algorithm were compared with streams derived from the proposed algorithm. The topological relationship between streams and lakes was clearly expressed by the proposed algorithm. In lake areas, the proposed algorithm showed better performance, and no parallel streams were found. In nonlake areas, the stream networks derived from these algorithms were stable. The proposed algorithm offers an opportunity to treat lakes and streams differently during simulation, thus adding to the authenticity of the simulation. Key Points A novel flow direction algorithm considering the characteristics of lake‐stream is proposed to construct a lake‐stream topological system The proposed flow direction model exhibits good robustness, considering the errors in lake areas in digital elevation models The constructed lake‐stream topological system can be applied in both endorheic and exorheic basins worldwide