Análise de Séries Hidrológicas na Bacia Hidrográfica afluente à Usina Hidrelétrica Castro Alves, RS

Abstract

This study aims to analyze the stationariety and homogeneity of rainfall and streamflow series of the contribution basin of Castro Alves Hydroeletric Power Plant, in Southern Brazil. The rainfall data were acquired from the Agência Nacional de Águas, and the average rainfall series was calculated for the period from 1945 to 2017. The streamflow data were acquired from the Operador Nacional do Sistema Elétrico covering a period from 1945 to 2017. The analysis were performed in the complete series and in two periods obtained from the same, referring to the period before and after 1970. Six statistical tests were used to check the stationarity: t-Student, F-Snedecor, Spearman Correlation Coefficent, Cox-Stuart, Mann-Whitney and Mann-Kendall. The verification of the point of change in the series of total annual precipitations, monthly totals and monthly average flows was performed using Pettitt’s test. The analysis results made it possible to conclude that the hydrological series are non-stationary. The period prior to 1970 was characterized as non-stationary. The period after 1970 showed significant signs of stationarity and homogeneity for both variables. Using the Pettitt test, a trend change was identified in the year 1971 and 1970 for the series of annual total precipitations and monthly mean flows, respectively. In the monthly analyzes of the series, it was found that the increase in the precipitated total was more accentuated in the dry months of May and November. This corroborates the more pronounced increase in the average monthly streamflow observed in those same months.

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