The rainfall chronicles in the locality of Doba and its surroundings by the Standardized Rainfall Index (SPI) and Randomness Verification Tests

Abstract

The study of the rainfall chronicles and its surroundings by the standardized rainfall index (spi) and randomness verification tests is of great importance for the management and planning of water resources. This work aims to study the variations of the rainfall regime over time by determining the precise years of rupture in the chronological series. This study considered rainfall data spread over 4 decades (from 1980 inclusive to 2019). These data were used to calculate the Standard Pluviometric Precipitation Index (SPI). These results show that the standardized rainfall indices vary from - 2.48 to 1.99 (extreme dry to very wet). The statistical methods of Pettitt, of Buishand, Bayesian of Lee and Heghinan show two rainfall sequences. A rain deficit sequence from 1980 to 2002 with an average of the indices in the order of (- 0.3113) and intercalated by years of severe droughts (1993, 1980 to 1987, 1993, and 2002). A surplus sequence in rainfall from 2003 to 2019 with an average index of 0.42. The rainfall variations observed have had a significant impact on the incoming water flows.