Journal of Hydrometeorology | Sinha et al. 
Frequent recurrences of drought in India have had major societal, economic and environmental impacts. While region-specific assessments are abundant, exhaustive appraisal over large spatial scales have been insubstantial. Here we devise and analyze a new drought index called Water Storage Deficit Index (WSDI) for holistic representation of drought. The crux of the method is the employment of Terrestrial Water Storage (TWS) variations from Gravity Recovery and Climate Experiment (GRACE) for quantification of drought intensity and severity. Drought events in recent times are well identified and quantified using the approach over four homogenous rainfall regions of India over the period of April 2002 – April 2015. Amongst all the four regions the highest peak deficit of -158.00 mm is observed in January 2015 over Central India. While the drought of 2002-2004 is prominent in Peninsular and West Central India, the drought of 2009-2010 and 2012-2013 is conspicuous in almost all the four regions of India. The longest deficit period of 23 months (February 2009 to December 2010), and the highest severity value of -26.31 are observed in Central and North West India respectively. WSDI values show an increasing trend in West Central India (0.07 yr-1), indicating recovery from previously existing drought conditions. On the contrary, a decreasing trend in WSDI is observed in North West (-0.07 yr-1) and Central (-0.18yr-1) India. Results demonstrate considerable confidence in the potential of WSDI for robust characterization of drought over large spatial scales.
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