The representation of stream networks is an integral component of river transport schemes used in large-scale hydrological and climate models. However, the coarse resolution of the cells describing the land component of climate models (e.g. 2.8°) is insufficient to adequately represent river flow directions across continents. Hence, a methodology is required for upscaling river network extraction from high resolution digital elevation models (DEMs) to the lower resolution of the climate models to which they will be applied. In this study, an innovative approach for upscaling flow directions is introduced. The method utilizes the maximum flow accumulation, computed from the high resolution DEM, to determine the most realistic representation of the river network at the coarse resolution. The approach is original because it incorporates a projected mesh as the overlay for the high resolution grid and uses a unique division of the low resolution grid into four sub-sections. Upscaled networks for rivers of Africa and South America are compared with the river networks from alternative upscaling methods and from the fine resolution river network to determine which approach best represents the rivers. Example river networks are provided for the Niger, the Congo and the Amazon River basins.
Upscaling River Network Extractions from Global Digital Elevation Models
By Mary S. Lear, M.S.E., James S. Famiglietti, and David R. Maidment
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