Rainfall variability study for crop planning under rainfed production system in Western Orissa

Daily rainfall data for 30 years (1975-2004) of seven different locations in Western Orissa viz, Sundergarh, Jharsuguda, Sambalpur, Bolangir, Titlagarh, Bhawanipatna and Koraput were analyzed for establishing long term averages of annual and seasonal rainfall and its temporal variability by deploying appropriate statistical techniques. The results revealed that the average annual rainfall in different parts of western Orissa varied from 918 mm in Sundergarh to 1541 mm in Sambalpur at different locations 78 to 86% of the total annual rainfall was received during monsoon months (June to September). The data on weekly rainfall revealed that the rain due to Southwest monsoon generally started during 24th standard meteorological week (SMW) except at Sundergarh in the extreme northern parts of western Orissa where it is delayed for a week. The monsoon rain normally ceased during 40th to 41st SMW except Bolangir, Bhawanipatna and Koraput where it ceased early during 37th to 38th SMW. At 75% confidence level, assured rain (800 to 1000 mm) for cultivation could be expected at all the locations except Sundergarh and Bhawanipatna. Except the extreme northern part of Sundergarh region, the average rainfall during monsoon (1072-1339 mm from June-September) indicated the suitability of rainfed rice cultivation in this part of Orissa with appropriate rain water management while the winter rain was meager (average rainfall 12-57 mm during December–February) for agricultural operations at all the locations even at 50% probability level.

Author : Sanjoy Saha and K.S. Rao