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Abstract

Mikunthan, T. 2007. Modeling of rainfall: a measurable tool in sustainable agriculture. JEMREST 3:83-90.

 

DOI: 10.4029/2007jemrest3no19

Precise prediction of rainfall has a significant role in productive agriculture especially in dry zone of Sri Lanka with conservation of natural groundwater. A comprehensive analysis of rainfall data is equally important to predict, demonstrate and substantiate agronomic results. It makes a significant contribution in planning in agriculture at present and in future especially those areas receive lesser rainfall. Early prediction of rainfall will definitely help to plan out the cultivation and other related processes towards the efficient use of the rainfall accordingly. The probability density function of gamma distribution is used to explain the quantity of rainfall associated with each event and the risk of long dry spills of every month and of the respective year. A two parameter gamma distribution model was fitted to the annual rainfall pattern of Pelwatta sugar catchment with a mean amount of 2.3 mm rainfall per rainy day and 0.5914 of shape parameter with significant correlation (r2= 98.93) using 15 years daily rainfall. The result of occurrence of drought incidence for every month and year showed the ability of the model to predict incidence of drought with high correlation of observed and predicted values. The correlations of probability distributions were more than 99% for annual and monthly distributions except in the month of May which had the value of 96.7%. Occurrence of drought incidence of 75% probability was less than 3 consecutive days in all months except June, July and August which have the values of 15 days, 4 days and 4 days respectively. The results of 75% fiducial probability model for Jaffna and Pelwatta explained true seasonal break of Maha and Yala, presence of torrential erosive rains and short rainfall. The true break of the season during 40th to 41st standard weeks for Maha and 12th standard week for Yala were observed in Jaffna. The results of the analysis of daily and weekly rainfall data by gamma density function and fiducial probability model would be an effective tool for the purpose of assisting sustainable agricultural planning.

 

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