Analysis of weekly rainfall data using onset of monsoon approach for micro level crop planning
2009
Kothari, A.K. | Jain, P.M. | Kumar, Virendra
Information on intervening critical dry spell and availability of surplus water is required for rainwater management in crop planning. Conventionally, probabilities of dry spells are computed for different standard meteorological weeks without consideration of the onset of monsoon in each year and information for crop growth period is assumed based on normal week of onset of monsoon. This approach has been compared with a rational approach called "Onset of monsoon approach" wherein the weekly rainfall data are arranged by considering onset of monsoon as datum in each year. Weekly rainfall data of Bhilwara district in Rajasthan state for a period of 45 years have been used for this analysis. Considerable difference has been observed in the initial and conditional probability of intervening dry spells due to these two approaches but the new approach has been found more rational as compared to conventional approach. Therefore, it has been adopted for analysis of dry spells and availability of surplus water at tehsil level in the district. The onset of monsoon was observed earliest in 22nd week and latest in 31st week in the district. The analysis of dry spells reveals that probability of dry spell is highest ( 75%) during late crop growth period (10th week from onset of monsoon). On the contrary, surplus water (20 mm) is available during initial to mid crop growth season (5th to 9th week of monsoon season). The probability of 100 mm surplus water during crop season ranges from 47 to 96 per cent at Asind and Mandalgarh, respectively. Suitable rainwater management practices and crop planning at micro (Tehsil) level have been suggested for efficient utilization of rainfall.
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