On the Observations and Environmental Modeling in Xingó Hydropower Plant - Northeast Brazil: Present and Future Hydroclimatic Features

The São Francisco River Basin plays a critical role in the hydroelectrical operational planning of Brazil. Understanding the hydroclimatic dynamic regime and, consequently, related climate changes is essential for decision-makers of the hydroelectrical sector. In this context, the Xingó hydropower plant and its drainage area are taken as a reference for the hydroclimatic features analyzed in this research. Observed rainfall in the drainage basin and streamflow measurements in the power plant between 1975 and 2016 are used to assess the climatology of the region and to identify trends in the time series. In addition, a methodological framework based on numerical modeling of the hydroclimatic variables is employed to examine the representation of the present climate (1961 to 1990) and to investigate the future projections (2011 to 2100). The outputs from the Eta regional climate model runs driven by two global models are adopted in this case under the RCP4.5 and RCP8.5 IPCC scenarios along with the SMAP rainfall-runoff model. In Xingó, the average annual precipitation is about 978 mm and the average annual streamflow is 2,534 m³ s⁻¹. The size of the Xingó HPP drainage area must be considered, as the rainfall that occurs in a given month can influence the streamflow of the following month. There is no trend regarding precipitation, while the streamflow time series show a statistically significant decreasing trend in the present climate. Climate projections point to an elevation in air temperature and a reduction in rainfall and streamflow by 2100. Most scenarios indicate that the average annual streamflow could be extremely low for nearly half of the twenty-first century. The results shown in this work may contribute to scenarios for operation of the Xingó HPP and support with information for planning decisions on country's energy security in the present and future climates.