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The current research intends to compare the agreement level between the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI), the former's variant, at different timescales such as 1, 3, 6, 9, 12, and 24 months. This data was compiled from the Mekerra basin with the help of time series of rainfall and temperature data for 42 years from 1970 to 2011. The authors used Cohen's kappa statistics and the Bland–Altman method to determine the test of agreement between SPI and SPEI. Furthermore, the innovative trend analysis (ITA) method was also employed to analyze the severe and extreme dry trends. The outcomes achieved from the Cohen's kappa statistic revealed the presence of a significant level of agreement between the SPI and SPEI values across the timescales. Furthermore, the researchers observed a positive linear correlation (r > 0.75, p < 0.0001) between the ratings under study. The existence of a small mean difference between the Bland and Altman analyses confirmed the level of agreement between the analytical tools under consideration. In addition to these, the outcomes also infer that in case of the unavailability of the temperature data to conduct the SPEI. Therefore, it is acceptable to use the SPI as the current study found the presence of an acceptable degree of agreement between these two scales in the study location. The present study suggests utilizing various types of drought indices to evaluate the drought performance in a specific location or geographical area to make knowledge-driven decisions. [ABSTRACT FROM AUTHOR]

This study investigates possible rainfall and drought trends using data from 38 rainfall stations in the Medjerda basin (northeast of Algeria) over 54 years (1965–2018). Drought-related data were calculated with the Standardized precipitation index (SPI). The Mann–Kendall test was used to find positive or negative precipitation trends. The magnitude of these trends was calculated using Sen's slope method. According to the analysis, a decrease during the spring precipitation season was observed. Furthermore, the authors found the maximum increasing (decreasing) precipitation magnitude to be 2.14 mm/season (− 4.41 mm/season) in winter (spring). In addition, the magnitude of the precipitation trend per year ranged from − 6.26 to 2.54 mm/year, with an average reduction of 39% for the entire basin. From the outcomes of drought trend analysis, it can be inferred that for a short-time scale, the innovative trend analysis method exhibited a negative trend for the minimum and maximum SPI values. Drought severity was found to have increased during severe and extreme wet episodes, directly affecting Algeria's frequently drought-affected agricultural regions, such as the Merdja plain and the irrigated perimeters of Sedrata and Zouabi. Considering the long-time scales, an increase was detected in drought severity and a decline during severe and extreme wet episodes. These findings show that the southeastern and central parts of the Medjerda basin's long-term water resources have been severely affected, which negatively impacts the newly-constructed Ouldjet Mellegue dam in Tébessa province. [ABSTRACT FROM AUTHOR]