Similarity and dissimilarity in model-results between single and multiple flow direction simulations based on a distributed ecohydrological model

Abstract. Distributed hydrological and ecosystem models route surface and subsurface flow in general two ways: single and multiple flow direction (SFD vs. MFD). However, few study has examined how model results differ between SFD and MFD simulation. The objective of this study is to explore the similarity and dissimilarity of model results between the two simulations. To achieve this objective, we compared model results based on a distributed ecohydrological model that was ran respectively under four different routing algorithms. Our results indicate that SFD and MFD algorithms behave in the same way in simulating stream hydrograph. When averaged for the watershed, the values of modeled ecohydrological variables do not differ significantly between SFD and MFD simulations. Nevertheless, due to differences between SFD and MFD algorithms, the modeled values of variables are spatially more autocorrelated under MFD algorithms than under SFD algorithms. In addition, there are significant differences in the modeled values of variables at individual cell level. For hydrological variables, differences are most significant in areas near channels and tend to decrease significantly as distances-from-channel increases. For ecological variables, differences are minimal in areas near channels and tend to increase significantly as distance-from- channel increases. The similarity and dissimilarity between SFD and MFD simulations are not subject to dry or wet year. Overall, we found there are no differences in model results between SFD and MFD algorithms when model results are averaged for a study area but there are significant differences in model results when individual cells are compared.