Assured Rainfall and Dry Spell Analysis for Crop Planning in East Champaran District of Bihar

Abstract

Soil moisture is the major limiting factor for crop production under rainfed condition. Therefore, agricultural planning needs to be prepared based on climatic potential of the area. For this, minimum assured weekly rainfall at 10, 25, 50, 75 and 90% probability levels were computed over East Champaran district by using historical weekly rainfall data of Chakia, Mehasi and Motihari rain-gauge stations for a period of 48 years (1965-2012). Initial and conditional probabilities of weekly rainfall and dry spell sequences during summer, kharif and rabi seasons were worked out for efficient crop planning. Considering 20 mm weekly rainfall, moisture sufficiency period prevailed at 25-35 SMW (Standard meteorological week) at 75% probability level. When weekly water requirement of rice (without water stress) of 50 mm was considered, the stable rainfall period continued for 9 weeks (26-34 SMW) at 50% probability. The probability of dry spell increased significantly after 38 SMW in the district.