Central Rice Research Institute Annual report...2011-12

Fig. 24. Three months (July, August and September) SPI map of 2003
Fig. 25. Three months (July, August and September) SPI map of 2008
season crops. Similarly, water balance components of
Odisha districts were also worked out to aid in formulating
adaptation strategies for rice based cropping system.
The Standardized Precipitation Index (SPI) is an
index based on the probability of recording a given
amount of precipitation. Therefore, the probability of
rainfall being less or more than a certain amount can be
determined. Drought event means a particular
rainfall event gives a low probability
on the cumulative probability
function. Using this index, the severity
and pattern of wetness/dryness in
Odisha were examined at block level.
Daily rainfall data from 168 rain gauge
stations were collected for the period
1982-2008. Different time scales of SPI
viz., SPI for one, two, three, six, nine and
twelve months were worked out. SPI spatial
maps were generated by Kriging interpolation
method using Spatial Analyst
tool of ArcGIS and the spatial pattern
were categorized into extremely wet
(SPI >2.0), severely wet (1.5 -2.0), moderately
wet (1.0-1.5), near normal
(-1.0 to 1.0), moderately dry (-1.0 to -1.5),
severely dry (-1.5 to -2.0) and extremely
dry (