Mechanistic ecohydrological modeling in a semiarid environment, the role of runon in water redistribution

Ecohydrological studies are becoming very important in terms of enhancing predictability of both hydrologic and vegetation dynamics. Nonetheless, few efforts have been devoted to the implementation of mechanistic ecohydrological models. The role of processes such as runon or the uneven distribution of vegetation in semi-arid systems can be significant. These mechanisms are nonetheless often neglected in modelling approaches. In this study, plot-scale and spatially-distributed simulations of hydrologic and vegetation metrics are realized. The scope of the study is to investigate the performance of a physically-based ecohydrological model in a semi-arid system and to highlight the dominant hydrological dynamics. The ecosystem is located in southern Arizona (USA) and is representative of a desert shrub community. The model is capable of capturing the underlying physical processes of the studied environment, reproducing numerous metrics of hydrological and vegetation dynamics. The role of runoff-runon processes on water redistribution is predominant when compared with the subsurface flows. This affects vegetation distribution, leading to the formation of niches of favourability and vegetation patchiness.