Assessing the Anthropogenic and Climatic Components in Runoff Changes of the São Francisco River Catchment

Quantifying the impacts caused by climate change and anthropogenic intervention on runoff is necessary for defining different adaptation strategies to climate change and understanding the future pattern of water and soil use for different human activities. Based on this rationale, this study proposes to associate the dynamics of flow variability in the São Francisco River catchment with that of climatic and anthropic covariates, by utilizing the Budyko framework and the decomposition method. Our results suggested that streamflow decreased in about 183 mm, 56 mm and 26 mm in the upper, middle and lower portions of the catchment, respectively. Climate change is the most prominent factor in the upstream region (75%, 43% and 42%), but the influence of human activities becomes more pronounced in the downstream areas (27%, 57% and 58%). However, as the drainage areas increase, model performance deteriorates, which introduces higher levels of bias and uncertainty to the attribution results.