Observed changes in long-duration droughts in major river basins in India

Droughts play a significant role in the planning and management of water resources. Variations in the frequency and magnitude of long-term (24-60 months) droughts exert far-reaching impacts on surface and groundwater resources. We analyze the changes in long-term drought (24-60 months) in major river basins in India. The role of temperature in influencing the areal extent and frequency of drought was analyzed by comparing the standardized precipitation index (SPI) and standardized precipitation-evapotranspiration index (SPEI). The influence of drought impact was assessed on streamflow and groundwater obtained from the gravity recovery and climate experiment (GRACE) data. The drought time scales of 24, 48, and 60 months were used for the Indian river basins using SPI and SPEI from 1951 to 2015. Observed precipitation and temperature data were obtained from the India Meteorological Department (IMD). The Thornthwaite method was used in the estimation of potential evapotranspiration (PET) to assess SPEI using mean temperature. The moderate drought (-1.0 to -1.49) was observed in 1965, 1974, 1979, and 1984. The river basins of the Indus, Ganga, and Sabarmati were found as drought hotspots. This study can be helpful in identifying the risk zones and can be used to improve potential management plans.