Automatic watershed delineation for a complicated terrain in the Heihe River Basin, Northwestern China

Digital elevation model (DEM), as a useful data source for automatic delineation of flow paths, sub watersheds and flow networks for hydrologic modeling, watershed management and environmental assessment, has been much extensively utilized in the multiple-discipline studies. Variety of approaches to delineating flow networks, using different algorithms have been proposed in the previous literatures, and the professional software for automatic delineation of the watershed has been commercialized. The scale of the delineated network, however, is sometimes controlled by a support area threshold, which may impose an arbitrary and spatially constant drainage density disable the software to complete the delineation procedures for those rather complicated terrain surface where the rugged mountainous area mixed with the flat terrains occur. An effective delineation procedure to accommodate spatially variable drainage density with D∞ approach in association with D8 algorithms for delineation of complicated terrain was proposed. With this computation procedure, the digital representation of the flow network and topographic characteristics of an approximately 13×10 Km Heihe drainage basin, the largest inland river system geographically located on 96°42'~102°00'E to 37°41'~42°42'N in northwestern China was obtained. The delineation procedures applied to more than 30 watersheds over Chinese Hanjiang and Heihe region suggested it a useful methodology for accurate delineations. Keywords-watershed delineation; complicated terrain; flow network; topographic characteristics; scale