Hydrological changes caused by the construction of dams and reservoirs: The CECP analysis.

This article investigates the impact of cascade dam and reservoir construction on the predictability and complexity of daily streamflow in the São Francisco River basin, Brazil, using the complexity entropy causality plane (CECP) method in both standard and weighted forms. By analyzing streamflow data from three fluviometric stations—São Francisco (upstream, unimpacted), Juazeiro (downstream of Sobradinho dam), and Pão de Açúcar (downstream of Sobradinho and Xingó dams)—the study finds that dam operations increase streamflow entropy and reduce complexity, indicating a shift toward less predictable flow regimes. Time-dependent CECP analysis with sliding windows reveals that changes in predictability at Pão de Açúcar began before the Sobradinho dam's construction, likely due to the Paulo Afonso complex, while natural factors also contributed to predictability changes upstream at São Francisco. The findings suggest that CECP, particularly its weighted form incorporating amplitude information, is a robust tool for detecting hydrological alterations caused by both human activities and natural variability, offering advantages over traditional statistical methods that require longer datasets.