Author(s):

Sujitha E and Shanmugasundaram K

Abstract: Standard Precipitation Index is a tool for the investigation of drought by taking into accounts its intensity and duration. The rarity of a drought or an anomalously wet event at a particular time scale for any location in the world that has a precipitation record can be analysed using SPI. Shorter timescale SPIs, for example 1, 2, 3 month SPIs, can provide early warning of drought and help assess drought severity. It is spatially consistent. Precipitation data for Trichy region (1982-2011) is analysed by SPI method for SPI-3 (a and b)* and SPI-6. The result revealed that, SPI -3 (a) shows the drought condition during that period of 1984 were extremely dry, 1982 and 1985 shows severely dry condition (-1.50 to 1.99), 1994, 1997 and 1999 were moderately dry (-1.00 to -1.49), 2008 was moderately wet (1.00 to 1.49) and SPI-3 (b) shows 1984 was extremely wet ( >2.00), 1987, 1989, 1993 2002, 2007 were moderately dry (-1.00 to -1.49), 1996 severely dry (-1.50 to -1.99). SPI -6 (June to November) shows the severe drought condition during the period of 1987 and 2003 (-1.50 to-1.99), moderately dry was in 1982, 1985, 1988 & 1999 (-1.00 to -1.49). From this Study, SPI helps to identify the frequency of occurrence of dry & wet years and to reveal trends of dry & wet condition severity. Plotting against year and SPI gives a good indication of the drought history of a particular station and serves as good indicator tool for drought analysis. (a and b)*- (June to August and September to November)

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