Abstract

Rainfall data (>30 years) of two locations (Bhavanisagar and Madurai) in Tamil Nadu were subjected to probability and variability analysis. The results revealed that on an average Bhavanisagar and Madurai receive 636 and 845 mm of rainfall annualy with a Coefficient of Variation of 35 and 21%. The average seasonal rainfall of South West Monsoon is 181 and 313 mm with a Co-efficient of Variation of 59 and 28 per cent. Both the locations are dominated by North East Monsoon season (302 and 376 mm) rainfall with more than 40% variability. North East Monsoon accounts for 48 and 45 per cent of total annual rainfall at Bhavanisagar and Madurai, respectively. The highest mean rainfall of 144 and 150 mm was recorded during the month October at Bhavanisagar and Madurai, respectively. The standard weeks 38 40 and 42nd - 47th have >50% chance to get 25 mm of rainfall in Bhavanisagar. At Madurai, standard weeks from 36 to 47 had more than 50% chance to get 25 mm of rainfall. At both the locations the chance of getting sowing rain seldom exceeds the threshold level of 67%, indicating risk of dry seeding under dryland condition. However, the analysis indicated that dry seeding could be taken up under dryland condition with substantial risk both at Bhavanisagar and Madurai. At Bhavanisagar region there is more chance for intermittent dry spell and hence drought resistant short duration grain legumes and groundnut may be suggested.

Keywords: Rainfall, Madurai, Bhavanisagar, Variability, Probability