Use of probability Distribution models in Rainfall Analysis for Postmonsoon Crop Planning in Eastern ghat Region of Orissa

An attempt is made to use selected probability distribution functions for analyzing rainfall of Koraput district of Orissa for judicious crop planning. The data indicated that (1969 - 2007), mean maximum of 391.8 mm rainfall was observed during the month of August, whereas 29th week (July 15 - July 21) experienced maximum of 110.9 mm. Rainfall variability of less than 100% is observed during 26th to 35th and 37th to 39th weeks and similarly during May to October variability remained less than 100% implying uniform wetness period. Three probability distribution models viz. two and three parameter Gamma distribution and Log Pearson Type III functions were found to be best fitted to the weekly, monthly and annually rainfall data series. Two parameter or three parameter Gamma distribution functions were found best fitted to the rainfall data series except January and March and paired t test revealed that there is no difference between the observed and thoretical distributed values. Through water balance analysis, it is found that there is only 4.3 mm rainfall available during Rabi season at 70% probaility level. Thus, judicious planning for conservation of the Rabi crop. An attempt is also made to explore possibility of conserving 50% of surplus rainwater in excavated pond. It is deduced that a suitable combination of crops like wheat + tomato, wheat + potato, tomato + bean and potato + cabbage can be successfully grown by the farmers during rabi season from the harvested water.