Stationarity of pluviometric series of the state of Ceará, Brazil

In climatically vulnerable and water-deficient regions, such as the Northeastern semiarid in Brazil, the study of hydrological behavior patterns becomes especially relevant to subsidize the decision-making in the management of water resources. In this context, this paper aims to investigate stationarity in the pluviometric historical series of the state of Ceará, Brazil. For that, pluviometric data was obtained through the HIDROWEB database; then, stations were selected based on their length (over 60 years of data), number of gaps in the series, and spatial distribution. After selection, the gaps were filled using linear regression. The Mann-Kendall and Pettitt tests were conducted with the help of the package 'trend', in R programming language. The aforementioned tests are non-parametrical, and analyze trend breaks and change points in long, historical pluviometric series. After applying the tests, it was noted that most of the selected stations presented stationary behavior, except for Chorozinho, which presented a p-value of 0,018 for the Mann-Kendall test, i.e., rejecting the null hypothesis of stationarity at 5% significance and presenting a positive monotone trend. For the Pettitt test, the station presented a p-value of 0,022, thus rejecting the null hypothesis of lack of change point at 5% significance, the change point being in the year of 1982. It is concluded that it was possible to analyze the stationarity of historic pluviometric series and have a better understanding of the hydrological regime of the region. This study aims to serve as a basis for future studies on rainfall in Ceará. (author)