Deviation in Occurrence of Climatic Drought Over Western Zone of Tamil Nadu

Drought is the major precipitation anomaly that has greater impact on water resource management, ground water table and agricultural production. The WASP index (Weighted Anomaly of Standardized Precipitation Index) was estimated for a period 1901-2019 (119 years) – four time scales (12 months, 9 months, 6 months and 3 months) based on the IMD precipitation dataset to analyse the dry events. Analysis over different time scales is necessary to find out the impact of the slowly evolving drought on the agricultural production as well as water resources. The numbers of moderate dry events were 276, 256, 188 and 100 for WASP12, WASP9, WASP6, and WASP3 respectively for the whole of 119 years data. The number of extreme dry events with WASP12, WASP9, WASP6, and WASP3 were 0, 4, 29 and 59, respectively, for 119 years. There was no specific trend in number of dry events over the study region and 1991-2019 was found to have higher number of dry events when compared with the other tri-decadal periods.