Scaling gridded river networks for macroscale hydrology: Development, analysis, and control of error

A simple and robust river network scaling algorithm (NSA) is presented to r escale fine-resolution networks to any coarser resolution. The algorithm wa s tested over the Danube River basin and the European continent. Coarse-res olution networks, at 2.5, 5, 10, and 30 min resolutions, were derived from higher-resolution gridded networks using NSA and geomorphometric attributes , such as river order, shape index, and width function. These parameters we re calculated and compared at each resolution. Simple scaling relationships were found to predict decreasing river lengths with coarser-resolution dat a. This relationship can be used to correct river length as a function of g rid resolution. The length-corrected width functions of the major river bas ins in Europe were compared at different resolutions to assess river networ k performance. The discretization error in representing basin area and rive r lengths at coarser resolutions were analyzed, and simple relationships we re found to calculate the minimum number of grid cells needed to maintain t he catchment area and length within a desired level of accuracy. This relat ionship; among geomorphological characteristics, such as shape index and wi dth function (derived from gridded networks at different resolutions), sugg ests that a minimum of 200-300 grid cells is necessary to maintain the geom orphological characteristics of the river networks with sufficient accuracy .