Assessment of occurrence of drought in a basin provides useful information for sustainable water resource planning and management. This study attempts to develop the spatial pattern of drought vulnerability based on frequency and severity of drought events at 3 and 12 month time scales in the Parambikulam-Aliyar river basin. Using the standardized precipitation index (SPI) as a drought assessment and monitoring tool, the occurrence of droughts was examined. The basin was divided into 97 grids of 5 × 5 km, spatial interpolation technique was applied in a geographic information system (GIS) environment with the help of inverse distance weighting approach and gridded rainfall data was generated using the monthly rainfall data for the period of 1972 to 2011 from 28 rain gauge stations. Gridded monthly SPI values were created using gridded rainfall and classified the SPI values based on drought categories and estimated percentage of occurrence (frequency) of drought categories (severity) at 3 and 12 month time scales. Spatial variation of moderate, severe and extreme drought maps are prepared and then integrated separately to prepare the drought vulnerability maps. Drought vulnerability map showed that the high and moderate vulnerability areas are mainly in the northern parts, while the areas with low vulnerability to drought are occurred in the southern parts of the basin.
Key words: Drought vulnerability, geographic information system (GIS), rainfall, standardized precipitation index (SPI).
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