Characterization of droughts by comparing three multiscale indices in Zacatecas, Mexico

Drought is one of the most frequent natural disasters to occur in north-central Mexico and its identification and characterization are crucial for mitigating its effects. This study analyzed the evolution of meteorological drought over the period 1961-2012 in the state of Zacatecas, Mexico, using three multiscale indices: the Standardized Precipitation Index (SPI) based on precipitation data, the Reconnaissance Drought Index (RDI), and the Standardized Precipitation-Evapotranspiration Index (SPEI) based on precipitation and evapotranspiration data. The temporal pattern of the drought was analyzed at three time scales (3, 6 and 12 months). The indices were compared using the Pearson and Spearman correlation coefficients. The main dry periods were 1982-1983, 1998-2000, and 2010-2012. At a 3-month scale, the SPI detected the lowest number of drought events (41), with an average duration of 2.5 months; and at 6- and 12-month scales, the RDI detected the lowest number of drought events, 32 and 16, respectively, with an average duration of 3.0 and 6.1 months, respectively. The SPEI detected the greatest number of extreme events at the 3-month scale, and the RDI and the SPI did so at the 6- and 12-month scales, respectively. For the three scales of analysis, the SPEI had the greatest average frequency percentage of severe droughts. The SPI vs RDI had the highest correlation (> 0.92), and the SPI vs SPEI had lowest correlation. The areas that were most affected by droughts were the northwestern, central, and southern regions of Zacatecas, where the principal rainfed and irrigated agriculture areas of the state are located. The findings can primarily help decision-making regarding cropping patterns and the optimal allocation of water in Irrigation District 034 in the state of Zacatecas.