Drought monitoring based on Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index in the arid zone of Balochistan province, Pakistan

Drought monitoring is of utmost concern in the efficient management of resources, for which several drought indices exist. Rainfall is the key indicator in monitoring drought, but temperature is also an important parameter in the occurrence of drought as it controls evapotranspiration. The study reported in this paper investigated periods of drought in the arid zone of Balochistan province of Pakistan using Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) based on monthly rainfall and temperature data for 38 years (1981–2018) from ten weather stations. Both SPI and SPEI were found successfully to detect temporal variation in drought at different time scales (1, 3, 6, 9, and 12 months). However, SPEI was successful in identifying more severe to extreme events in the study area at higher time scales and moderate droughts at lower timescales. The results show that temperature is an important parameter in drought characterization and the use of SPI is recommended only where temperature data is missing. Pearson correlation coefficients indicated positive relationships between SPI and SPEI. The Mann-Kendall test was applied to establish the trend in drought over the period studied, and Sen’s slope estimation detected an increasing trend in severity from lower to higher timescales.