Assessing spatial characteristics of meteorological drought trends in the Parambikulam-Aliyar Basin, Tamil Nadu

Evaluation of drought characteristics in a basin provides useful information for sustainable water resources planning and management. In the present study, the Standardized Precipitation Index (SPI) was employed to investigate the meteorological drought characteristics in the Parambikulam-Aliyar basin, Tamil Nadu. The basin was divided into 97 grid-cells of 5 × 5 km and monthly rainfall data for the period 1972–2011 from 28 rain gauge stations were used for spatial interpolation of rainfall using ArcGIS. Historical drought was analysed from the regional representative of SPI values calculated from mean areal rainfall over the basin and its spatial distribution was assessed. The analysis of the SPI suggested that the basin had suffered severe and extreme drought in the 1970s and 1980s. In particular, the year 1974, 1976 and 1982 experienced severe and extreme droughts and had a larger spatial coverage and longer duration. The linear trend of SPI values of each grid was calculated and spatially distributed. The results of linear trends showed that positive trends are seen over large parts of the basin. Critical rainfall values were derived for each grid to determine least amount of rainfall required to avoid drought initiation. The spatial map of critical rainfall exhibited that rainfall demand for non-drought conditions increases in north south direction toward the south eastern direction, and in general, the northern parts will be least affected from drought. The results of this study can be used for developing drought preparedness plans and mitigation strategies within the basin.