For the studies, Central Water Commission adopted the same criteria as followed by the Irrigation Commission, 1972 i.e. drought is a situation occuring in an area:
When the annual rainfall is less than 75% of the normal in 20% of the years examined.
Less than 30% of the cultivated area is irrigated.
Central Water Commission adopted a smaller Unit viz. Talukas for drought identification studies instead of districts and therefore, number of drought affected Talukas were identified as 315 out of a total of 725 Talukas in 99 districts.
Accordingly, out of 108 M. ha area of 99 districts, only 51.12 M. ha spread over 74 districts have been considered as drought districts. Thus, in comparison to total geographical area of the country (329 M. ha) about 1/6th is drought prone.